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1.  What is the risk of stress risers for interprosthetic fractures of the femur? A biomechanical analysis 
International Orthopaedics  2012;36(12):2441-2446.
Purpose
Due to increasing life expectancy we see a rising number of joint replacements. Along with the proximal prosthesis in the femur, more and more people have a second implant on the distal ipsilateral side. This might be a retrograde nail or a locking plate to treat distal femur fractures or a constrained knee prosthesis in the case of severe arthrosis. All these constructs can lead to fractures between the implants. The goal of this study was to evaluate the risk of stress risers for interprosthetic fractures of the femur.
Methods
Thirty human cadaveric femurs were divided into five groups: (1) femurs with a prosthesis on the proximal side only, (2) hip prosthesis on the proximal end and a distal femur nail, (3) femurs with both a hip prosthesis and a constrained knee prosthesis, (4) femurs with a hip prosthesis on the proximal side and a 4.5-mm distal femur locking plate; the locking plate was 230 mm in length, with ten holes in the shaft, and (5) femurs with a proximal hip prosthesis and a 4.5-mm distal femur locking plate; the locking plate was 342 mm in length, with 16 holes in the shaft.
Results
Femurs with a hip prosthesis and knee prosthesis showed significantly higher required fracture force compared to femurs with a hip prosthesis and a distal retrograde nail. Femurs with a distal locking plate of either length showed a higher required fracture force than those with the retrograde nail.
Conclusions
The highest risk for a fracture in the femur with an existing hip prosthesis comes with a retrograde nail. A distal locking plate for the treatment of supracondylar fractures leads to a higher required fracture force. The implantation of a constrained knee prosthesis that is not loosened on the ipsilateral side does not increase the risk for a fracture.
doi:10.1007/s00264-012-1697-0
PMCID: PMC3508046  PMID: 23132503
2.  The BHU bicentric bipolar prosthesis in fracture neck femur in active elderly 
Background
55 BHU bicentric bipolar hemiarthroplasties were reviewed after a mean follow up of 4 years (range 1–5 years). Patients with displaced subcapital fractures were selected for operation on the basis of good mobility before the fracture. Object of the study was to see the efficacy of BHU bipolar prostheses and functional outcome.
Results
There were no incidences of dislocation. Modified Harris hip scoring system scoring system was used which included sitting crosslegged and squatting in view of the sociocultural needs of the patients of Indian subcontinent. Modified Harris hip scoring system 89% had a good or excellent result and 94% had no or only occasional pain. Majority of the patients returned to their prefracture activity.
Conclusion
Thus at follow up of 4 year the BHU bicentric bipolar prosthesis has been shown to be a good option for intracapsular fractures of neck femur with encouraging results.
doi:10.1186/1752-2897-2-7
PMCID: PMC2586620  PMID: 18817566
3.  Revision Rates after Primary Hip and Knee Replacement in England between 2003 and 2006 
PLoS Medicine  2008;5(9):e179.
Background
Hip and knee replacement are some of the most frequently performed surgical procedures in the world. Resurfacing of the hip and unicondylar knee replacement are increasingly being used. There is relatively little evidence on their performance. To study performance of joint replacement in England, we investigated revision rates in the first 3 y after hip or knee replacement according to prosthesis type.
Methods and Findings
We linked records of the National Joint Registry for England and Wales and the Hospital Episode Statistics for patients with a primary hip or knee replacement in the National Health Service in England between April 2003 and September 2006. Hospital Episode Statistics records of succeeding admissions were used to identify revisions for any reason. 76,576 patients with a primary hip replacement and 80,697 with a primary knee replacement were included (51% of all primary hip and knee replacements done in the English National Health Service). In hip patients, 3-y revision rates were 0.9% (95% confidence interval [CI] 0.8%–1.1%) with cemented, 2.0% (1.7%–2.3%) with cementless, 1.5% (1.1%–2.0% CI) with “hybrid” prostheses, and 2.6% (2.1%–3.1%) with hip resurfacing (p < 0.0001). Revision rates after hip resurfacing were increased especially in women. In knee patients, 3-y revision rates were 1.4% (1.2%–1.5% CI) with cemented, 1.5% (1.1%–2.1% CI) with cementless, and 2.8% (1.8%–4.5% CI) with unicondylar prostheses (p < 0.0001). Revision rates after knee replacement strongly decreased with age.
Interpretation
Overall, about one in 75 patients needed a revision of their prosthesis within 3 y. On the basis of our data, consideration should be given to using hip resurfacing only in male patients and unicondylar knee replacement only in elderly patients.
Jan van der Meulen and colleagues show that about one in 75 patients with a primary hip or knee replacement needed a revision of their prosthesis within 3 years.
Editors' Summary
Background.
Though records show attempts to replace a hip date back to 1891, it was not till the 1960s before total hip replacements were successfully performed, and the 1970s before total knee replacements were carried out. These procedures are some of the most frequently performed surgical operations, with a total of 160,00 total hip and knee replacement procedures carried out in England and Wales and about half a million in the US in 2006. Hip and knee replacements are most commonly used as a treatment for severe arthritis once other approaches, such as pain relief medications, have failed. A total hip replacement involves replacing the head of the femur (the thigh bone) with an artificial component, typically metal; the socket into which the new femur head will insert is also replaced with artificial components. In an alternative procedure, resurfacing, rather than replacing the entire joint, the diseased surfaces are replaced with metal components. This procedure may be better suited to patients with less severe disease, and is also thought to result in quicker recovery. The techniques for hip and knee replacement can also be divided into those where a cement is used to position the metal implant into the bone (cemented) versus those where cement is not used (cementless).
Why Was This Study Done?
To date, little evidence has been available to compare patient outcomes following hip or knee replacement with the many different types of techniques and prostheses available. National registries have been established in a number of countries to try to collect data in order to build the evidence base for evaluating different types of prosthesis. Specifically, it is important to find out if there are any important differences in revision rates (how often the hip replacement has to be re-done) following surgery using the different techniques. In England and Wales, the National Joint Registry (NJR) has collected data on patient characteristics, types of prostheses implanted, and the type of surgical procedures used, since its initiation in April 2003.
What Did the Researchers Do and Find?
The researchers linked the records of the NJR and the Hospital Episode Statistics (HES) for patients treated by the NHS in England who had undergone a primary hip and knee replacement between April 2003 and September 2006. The HES database contains records of all admissions to NHS hospitals in England, and allowed the researchers to more accurately identify revisions of procedures that were done on patients in the NJR database.
They identified 327,557 primary hip or knee replacement procedures performed during that time period, but only 167,076 could be linked between the two databases.
76,576 patients in the linked database had undergone a primary hip replacement. The overall revision rate was 1.4% (95% confidence interval [CI] 1.2%–1.5%) at 3 years, with the lowest revision rates experienced by patients who had cemented prostheses. Women were found to have higher revision rates after hip resurfacing, and the revision rate was about twice as high in patients who had had a hip replacement for other indications than osteoarthritis. A patient's age did not appear to affect revision rates after hip surgery.
80,697 patients in the linked database had undergone a primary knee replacement. The overall revision rate was 1.4% (95% CI 1.3%–1.6%) at three years, again with the lowest rates of replacement experienced by patients who had cemented prostheses. Revision rates after knee replacement strongly decreased with age.
What Do These Findings Mean?
Overall, about one in 75 patients required a revision of their joint replacement, which is considered low, and cemented hip or knee prosthesis had the lowest revision rates. Post hip replacement, the highest revision rate was in patients who had undergone hip resurfacing, especially women. Following knee replacement, the highest revision rate was in patients who had undergone unicondylar prosthesis. However, in this study patients were only followed up for three years after the initial knee replacement, and it's possible that different patterns regarding the success of these differing techniques may emerge after longer follow-up. Importantly, this study was entirely observational, and data were collected from patients who had been managed according to routine clinical practice (rather than being randomly assigned to different procedures). Substantial differences in the age and clinical characteristics of patients receiving the different procedures were seen. As a result, it's not possible to directly draw conclusions on the relative benefits or harms of the different procedures, but this study provides important benchmark data with which to evaluate future performance of different procedures and types of implant.
Additional Information.
Please access these Web sites via the online version of this summary at http://dx.doi.org/10.1371/journal.pmed.0050179.
The website of the British Orthopaedic Association contains information for patients and surgeons
The website of the National Institute for Health and Clinical Excellence contains guidance on hip prostheses
Information is available from the US National Institutes of Health (Medline) on hip replacement, including interactive tutorials and information about rehabilitation and recovery
Medline also provides similar resources for knee replacement
The NHS provides information for patients on hip and knee replacement, including questions patients might ask, real stories, and useful links
The National Joint Registry provides general information about joint replacement, as well as allowing users to download statistics on the data it has collected on the numbers of procedures carried out in the UK
doi:10.1371/journal.pmed.0050179
PMCID: PMC2528048  PMID: 18767900
4.  Bipolar or Unipolar Hemiarthroplasty after Femoral Neck Fracture in the Geriatric Population 
Balkan medical journal  2013;30(4):400-405.
Background:
The choice of prosthesis in hemiarthroplasty is controversial for geriatric patients after femoral neck fracture. We hypothesised that selection criteria for unipolar or bipolar prostheses could be constructed based on factors affecting mortality.
Aims:
The aims of this retrospective study were: (1) to determine the factors affecting mortality of femoral neck fracture patients ≥65 years of age; (2) to compare patient mortality rates, radiological findings, and functional outcomes according to prosthesis type (unipolar or bipolar); and (3) to evaluate the persistence of inner bearing mobility of bipolar prostheses.
Study Design:
Retrospective comparative study.
Methods:
In total, 144 patients operated for hemiarthroplasty and aged ≥65 were included. We classified the patients into either unipolar or bipolar prosthesis groups. To reveal factors that affected mortality, age, sex, delay in surgery, and American Society of Anesthesiologists score were obtained from folders. Barthel Daily Living, Harris hip, and acetabular erosion scores were calculated and bipolar head movement was analysed for live patients.
Results:
One-year mortality was 31.94%. Age ≥75 (p=0.029), male sex (p=0.048), and delay in surgery ≥6 (p=0.004) were the patient characteristics that were related to increased mortality. There were no significant differences in sex, age, American Society of Anesthesiologists score, delay in surgery, mortality, or Barthel, Harris, acetabulum scores between the two groups. Twenty patients from each group were admitted for last follow-up. Bipolar head movement was preserved for 33.3% of patients. They were inactive patients with low Barthel and Harris scores.
Conclusion:
Although bipolar head movement was preserved in inactive patients, we suppose that this conferred no advantage to these patients, who could hardly walk. In this study, male patients, those aged ≥75 years, and those operated at ≥6 days had an increased risk of mortality. Also, although not significant in multivariate analysis, high American Society of Anesthesiologists score (≥3) was related to increased mortality. Considering that one of three patients died during the first postoperative year, we think that these patients should be operated as soon as possible, and expensive bipolar prostheses must be used selectively in regard to patient characteristics.
doi:10.5152/balkanmedj.2013.8571
PMCID: PMC4115937  PMID: 25207148
Femoral neck fracture; mortality; hemiarthroplasty
5.  Bipolar versus fixed-head hip arthroplasty for femoral neck fractures in elderly patients 
Between 2002 and 2007, fifty elderly patients with displaced femoral neck fractures were treated with hip replacement at Emergency Hospital, Mansoura University. Patients were randomly selected, 25 patients had either cemented or cementless bipolar prosthesis, and another 25 patients had either cemented or cementless fixed-head prosthesis. There were 34 women and 16 men with an average age of 63.5 years (range between 55 and 72 years). All patients were followed up both clinically and radiologically for an average 4.4 years (range between 2 and 6 years). At the final follow-up, the average Harris hip score among the bipolar group was 92 points (range between 72 and 97 points), while the fixed-head group was 84 points (range between 65 and 95 points). Radiologically, joint space narrowing more than 2 mm was found in only 8% (2 patients) among the bipolar group, and in 28% (7 patients) of the fixed-head group. Through the follow-up period, total hip replacement was needed in two cases of the bipolar group and seven cases of the fixed-head group. Bipolar hemiarthroplasty offered a better range of movement with less pain and more stability than the fixed-head hemiarthroplasty in elderly patients with displaced femoral neck fractures.
doi:10.1007/s11751-010-0100-1
PMCID: PMC3058187  PMID: 21589675
Femoral neck fractures; Hip prosthesis; Arthroplasty
6.  Bipolar versus fixed-head hip arthroplasty for femoral neck fractures in elderly patients 
Between 2002 and 2007, fifty elderly patients with displaced femoral neck fractures were treated with hip replacement at Emergency Hospital, Mansoura University. Patients were randomly selected, 25 patients had either cemented or cementless bipolar prosthesis, and another 25 patients had either cemented or cementless fixed-head prosthesis. There were 34 women and 16 men with an average age of 63.5 years (range between 55 and 72 years). All patients were followed up both clinically and radiologically for an average 4.4 years (range between 2 and 6 years). At the final follow-up, the average Harris hip score among the bipolar group was 92 points (range between 72 and 97 points), while the fixed-head group was 84 points (range between 65 and 95 points). Radiologically, joint space narrowing more than 2 mm was found in only 8% (2 patients) among the bipolar group, and in 28% (7 patients) of the fixed-head group. Through the follow-up period, total hip replacement was needed in two cases of the bipolar group and seven cases of the fixed-head group. Bipolar hemiarthroplasty offered a better range of movement with less pain and more stability than the fixed-head hemiarthroplasty in elderly patients with displaced femoral neck fractures.
doi:10.1007/s11751-010-0100-1
PMCID: PMC3058187  PMID: 21589675
Femoral neck fractures; Hip prosthesis; Arthroplasty
7.  Interprosthetic humeral fracture revision using a tibial allograft total elbow prosthetic composite in a patient with hemophilia A : a case report 
Introduction
Interprosthetic fractures of the humerus are rare. Revisions of total elbow arthroplasty components in these cases are difficult. We report the first case of a patient with hemophilia who underwent a revision with a tibial allograft prosthetic composite without the need for hardware augmentation.
Case presentation
A 43-year-old Caucasian man with a history of hemophilia and transfusion-related human immunodeficiency virus and hepatitis B and C presented with an interprosthetic fracture of his humerus after months of pain between his total elbow and total shoulder arthroplasties. Because of the poor remaining bone stock available in his distal humerus, a revision using a barrel-staved tibial allograft prosthetic composite was performed. Our patients’ factor VIII level was optimized before the operation and he suffered no major long-term complications at 28 months. His only complication was an incomplete radial nerve palsy that ultimately recovered and left him with some numbness on the dorsum of his hand.
Conclusion
Careful use of an allograft prosthetic composite is a very reasonable option when a patient experiences an interprosthetic fracture. We have successfully performed revision total elbow arthroplasty for a patient with hemophilia with an interprosthetic fracture using a tibial allograft and no additional fixation, which resulted in his return to full activities of daily living, minimal pain and full incorporation of the allograft to host bone.
doi:10.1186/1752-1947-6-319
PMCID: PMC3492012  PMID: 23009283
8.  Metal-on-Metal Total Hip Resurfacing Arthroplasty 
Executive Summary
Objective
The objective of this review was to assess the safety and effectiveness of metal on metal (MOM) hip resurfacing arthroplasty for young patients compared with that of total hip replacement (THR) in the same population.
Clinical Need
Total hip replacement has proved to be very effective for late middle-aged and elderly patients with severe degenerative diseases of the hips. As indications for THR began to include younger patients and those with a more active life style, the longevity of the implant became a concern. Evidence suggests that these patients experience relatively higher rates of early implant failure and the need for revision. The Swedish hip registry, for example, has demonstrated a survival rate in excess of 80% at 20 years for those aged over 65 years, whereas this figure was 33% by 16 years in those aged under 55 years.
Hip resurfacing arthroplasty is a bone-conserving alternative to THR that restores normal joint biomechanics and load transfer. The technique has been used around the world for more than 10 years, specifically in the United Kingdom and other European countries.
The Technology
Metal-on-metal hip resurfacing arthroplasty is an alternative procedure to conventional THR in younger patients. Hip resurfacing arthroplasty is less invasive than THR and addresses the problem of preserving femoral bone stock at the initial operation. This means that future hip revisions are possible with THR if the initial MOM arthroplasty becomes less effective with time in these younger patients. The procedure involves the removal and replacement of the surface of the femoral head with a hollow metal hemisphere, which fits into a metal acetabular cup.
Hip resurfacing arthroplasty is a technically more demanding procedure than is conventional THR. In hip resurfacing, the femoral head is retained, which makes it much more difficult to access the acetabular cup. However, hip resurfacing arthroplasty has several advantages over a conventional THR with a small (28 mm) ball. First, the large femoral head reduces the chance of dislocation, so that rates of dislocation are less than those with conventional THR. Second, the range of motion with hip resurfacing arthroplasty is higher than that achieved with conventional THR.
A variety of MOM hip resurfacing implants are used in clinical practice. Six MOM hip resurfacing implants have been issued licences in Canada.
Review Strategy
A search of electronic bibliographies (OVID Medline, Medline In-Process and Other Non-Indexed Citations, Embase, Cochrane CENTRAL and DSR, INAHTA) was undertaken to identify evidence published from Jan 1, 1997 to October 27, 2005. The search was limited to English-language articles and human studies. The literature search yielded 245 citations. Of these, 11 met inclusion criteria (9 for effectiveness, 2 for safety).
The result of the only reported randomized controlled trial on MOM hip resurfacing arthroplasty could not be included in this assessment, because it used a cemented acetabular component, whereas in the new generation of implants, a cementless acetabular component is used. After omitting this publication, only case series remained.
Summary of Findings
 
Health Outcomes
The Harris hip score and SF-12 are 2 measures commonly used to report health outcomes in MOM hip resurfacing arthroplasty studies. Other scales used are the Oxford hip score and the University of California Los Angeles hip score.
The case series showed that the mean revision rate of MOM hip resurfacing arthroplasty is 1.5% and the incidence of femoral neck fracture is 0.67%. Across all studies, 2 cases of osteonecrosis were reported. Four studies reported improvement in Harris hip scores. However, only 1 study reported a statistically significant improvement. Three studies reported improvement in SF-12 scores, of which 2 reported a significant improvement. One study reported significant improvement in UCLA hip score. Two studies reported postoperative Oxford hip scores, but no preoperative values were reported.
None of the reviewed studies reported procedure-related deaths. Four studies reported implant survival rates ranging from 94.4% to 99.7% for a follow-up period of 2.8 to 3.5 years. Three studies reported on the range of motion. One reported improvement in all motions including flexion, extension, abduction-adduction, and rotation, and another reported improvement in flexion. Yet another reported improvement in range of motion for flexion abduction-adduction and rotation arc. However, the author reported a decrease in the range of motion in the arc of flexion in patients with Brooker class III or IV heterotopic bone (all patients were men).
Safety of Metal-on-Metal Hip Resurfacing Arthroplasty
There is a concern about metal wear debris and its systemic distribution throughout the body. Detectable metal concentrations in the serum and urine of patients with metal hip implants have been described as early as the 1970s, and this issue is still controversial after 35 years.
Several studies have reported high concentration of cobalt and chromium in serum and/or urine of the patients with metal hip implants. Potential toxicological effects of the elevated metal ions have heightened concerns about safety of MOM bearings. This is of particular concern in young and active patients in whom life expectancy after implantation is long.
Since 1997, 15 studies, including 1 randomized clinical trial, have reported high levels of metal ions after THR with metal implants. Some of these studies have reported higher metal levels in patients with loose implants.
Adverse Biological Effects of Cobalt and Chromium
Because patients who receive a MOM hip arthroplasty are shown to be exposed to high concentrations of metallic ions, the Medical Advisory Secretariat searched the literature for reports of adverse biological effects of cobalt and chromium. Cobalt and chromium make up the major part of the metal articulations; therefore, they are a focus of concern.
Risk of Cancer
To date, only one study has examined the incidence of cancer after MOM and polyethylene on metal total hip arthroplasties. The results were compared to that of general population in Finland. The mean duration of follow-up for MOM arthroplasty was 15.7 years; for polyethylene arthroplasty, it was 12.5 years. The standardized incidence ratio for all cancers in the MOM group was 0.95 (95% CI, 0.79–1.13). In the polyethylene on metal group it was 0.76 (95% CI, 0.68–0.86). The combined standardized incidence ratio for lymphoma and leukemia in the patients who had MOM THR was 1.59 (95% CI, 0.82–2.77). It was 0.59 (95% CI, 0.29–1.05) for the patients who had polyethylene on metal THR. Patients with MOM THR had a significantly higher risk of leukemia. All patients who had leukemia were aged over than 60 years.
Cobalt Cardiotoxicity
 
Epidemiological Studies of Myocardiopathy of Beer Drinkers
An unusual type of myocardiopathy, characterized by pericardial effusion, elevated hemoglobin concentrations, and congestive heart failure, occurred as an epidemic affecting 48 habitual beer drinkers in Quebec City between 1965 and 1966. This epidemic was directly related the consumption of a popular beer containing cobalt sulfate. The epidemic appeared 1 month after cobalt sulfate was added to the specific brewery, and no further cases were seen a month after this specific chemical was no longer used in making this beer. A beer of the same name is made in Montreal, and the only difference at that time was that the Quebec brand of beer contained about 10 times more cobalt sulphate. Cobalt has been added to some Canadian beers since 1965 to improve the stability of the foam but it has been added in larger breweries only to draught beer. However, in small breweries, such as those in Quebec City, separate batches were not brewed for bottle and draught beer; therefore, cobalt was added to all of the beer processed in this brewery.
In March 1966, a committee was appointed under the chairmanship of the Deputy Minister of Health for Quebec that included members of the department of forensic medicine of Quebec’s Ministry of Justice, epidemiologists, members of Food and Drug Directorate of Ottawa, toxicologists, biomedical researchers, pathologists, and members of provincial police. Epidemiological studies were carried out by the Provincial Ministry of Health and the Quebec City Health Department.
The association between the development of myocardiopathy and the consumption of the particular brand of beer was proven. The mortality rate of this epidemic was 46.1% and those who survived were desperately ill, and recovered only after a struggle for their lives.
Similar cases were seen in Omaha (Nebraska). The epidemic started after a cobalt additive was used in 1 of the beers marketed in Nebraska. Sixty-four patients with the clinical diagnosis of alcoholic myocardiopathy were seen during an 18-month period (1964–1965). Thirty of these patients died. The first patient became ill within 1 month after cobalt was added to the beer, and the last patient was seen within 1 month of withdrawal of cobalt.
A similar epidemic occurred in Minneapolis, Minnesota. Between 1964 and 1967, 42 patients with acute heart failure were admitted to a hospital in Minneapolis, Minnesota. Twenty of these patients were drinking 6 to 30 bottles per day of a particular brand of beer exclusively. The other 14 patients also drank the same brand of beer, but not exclusively. The mortality rate from the acute illness was 18%, but late deaths accounted for a total mortality rate of 43%. Examination of the tissue from these patients revealed markedly abnormal changes in myofibrils (heart muscles), mitochondria, and sarcoplasmic reticulum.
In Belgium, a similar epidemic was reported in 1966, in which, cobalt was used in some Belgian beers. There was a difference in mortality between the Canadian or American epidemic and this series. Only 1 of 24 patients died, 1.5 years after the diagnosis. In March 1965, at an international meeting in Brussels, a new heart disease in chronic beer drinkers was described. This disease consists of massive pericardial effusion, low cardiac output, raised venous pressure, and polycythemia in some cases. This syndrome was thought to be different from the 2 other forms of alcoholic heart disease (beriberi and a form characterized by myocardial fibrosis).
The mystery of the above epidemics as stated by investigators is that the amount of cobalt added to the beer was below the therapeutic doses used for anemia. For example, 24 pints of Quebec brand of beer in Quebec would contain 8 mg of cobalt chloride, whereas an intake of 50 to 100 mg of cobalt as an antianemic agent has been well tolerated. Thus, greater cobalt intake alone does not explain the occurrence of myocardiopathy. It seems that there are individual differences in cobalt toxicity. Other features, like subclinical alcoholic heart disease, deficient diet, and electrolyte imbalance could have been precipitating factors that made these patients susceptible to cobalt’s toxic effects.
In the Omaha epidemic, 60% of the patients had weight loss, anorexia, and occasional vomiting and diarrhea 2 to 6 months before the onset of cardiac symptoms. In the Quebec epidemic, patients lost their appetite 3 to 6 months before the diagnosis of myocardiopathy and developed nausea in the weeks before hospital admission. In the Belgium epidemic, anorexia was one of the most predominant symptoms at the time of diagnosis, and the quality and quantity of food intake was poor. Alcohol has been shown to increase the uptake of intracoronary injected cobalt by 47%. When cobalt enters the cells, calcium exits; this shifts the cobalt to calcium ratio. The increased uptake of cobalt in alcoholic patients may explain the high incidence of cardiomyopathies in beer drinkers’ epidemics.
As all of the above suggest, it may be that prior chronic exposure to alcohol and/or a nutritionally deficient diet may have a marked synergistic effect with the cardiotoxicity of cobalt.
Conclusions
MOM hip resurfacing arthroplasty has been shown to be an effective arthroplasty procedure as tested in younger patients.
However, evidence for effectiveness is based only on 7 case series with short duration of follow-up (2.8–3.5 years). There are no RCTs or other well-controlled studies that compare MOM hip resurfacing with THR.
Revision rates reported in the MOM studies using implants currently licensed in Canada (hybrid systems, uncemented acetabular, and cemented femoral) range from 0.3% to 3.6% for a mean follow-up ranging from 2.8 to 3.5 years.
Fracture of femoral neck is not very common; it occurs in 0.4% to 2.2% of cases (as observed in a short follow-up period).
All the studies that measured health outcomes have reported improvement in Harris Hip and SF-12 scores; 1 study reported significant reduction in pain and improvement in function, and 2 studies reported significant improvement in SF-12 scores. One study reported significant improvement in UCLA Hip scores.
Concerns remain on the potential adverse effects of metal ions. Longer-term follow-up data will help to resolve the inconsistency of findings on adverse effects, including toxicity and carcinogenicity.
Ontario-Based Economic Analysis
The device cost for MOM ranges from $4,300 to $6,000 (Cdn). Traditional hip replacement devices cost about $2,000 (Cdn). Using Ontario Case Costing Initiative data, the total estimated costs for hip resurfacing surgery including physician fees, device fees, follow-up consultation, and postsurgery rehabilitation is about $15,000 (Cdn).
Cost of Total Hip Replacement Surgery in Ontario
MOM hip arthroplasty is generally recommended for patients aged under 55 years because its bone-conserving advantage enables patients to “buy time” and hence helps THRs to last over the lifetime of the patient. In 2004/2005, 15.9% of patients who received THRs were aged 55 years and younger. It is estimated that there are from 600 to 1,000 annual MOM hip arthroplasty surgeries in Canada with an estimated 100 to 150 surgeries in Ontario. Given the increased public awareness of this device, it is forecasted that demand for MOM hip arthroplasty will steadily increase with a conservative estimate of demand rising to 1,400 cases by 2010 (Figure 10). The net budget impact over a 5-year period could be $500,000 to $4.7 million, mainly because of the increasing cost of the device.
Projected Number of Metal-on-Metal Hip Arthroplasty Surgeries in Ontario: to 2010
PMCID: PMC3379532  PMID: 23074495
9.  Prosthetic replacement in femoral neck fracture in the elderly: Results and review of the literature 
Indian Journal of Orthopaedics  2008;42(1):61-67.
Background:
Intracapsular fractures of the proximal femur account for a major share of fractures in the elderly. The primary goal of treatment is to return the patient to his or her pre-fracture functional status. There are multiple internal fixation options (screws, dynamic hip screw plate or blade plates) and hemi and total hip arthroplasty. Open reduction and internal fixation has been shown to have a high rate of revision surgery due to nonunion and avascular necrosis. Hip replacement arthroplasty (hemi or total) is a viable treatment option.
Materials and Methods:
Eighty-four elderly patients (age >70 years) with a femoral neck fracture were treated over a five-year period (January 2001 to December 2006). Eighty of the 84 patients underwent some form of hip replacement after appropriate medical and anesthetic fitness.
Results:
We had good results in all the patients in terms of return to pre-fracture level of activity, independent ambulation and satisfaction with the procedure. Patients over the age of 80 years who underwent bipolar hemiarthroplasty all progressed well without any complication. Patients in their seventies underwent some form of total hip replacement and barring one case of deep infection, two cases of deep vein thrombosis and three cases of dislocation (which were managed conservatively), there were no real complications.
Conclusion:
Hip replacement (hemi or total) is a successful procedure for the elderly population over 70 years with femoral neck fractures. Return to pre-morbid level of activity and independent functions occur very swiftly, avoiding the hazards of prolonged incumbency. We have proposed a treatment algorithm following the results of treatment of this fracture in our series. We have also reviewed the different contemporary treatment options used (conservative treatment, cancellous screw fixation, Dynamic Hip Screw (DHS) fixation, hemi and total hip replacement) used for treatment of an elderly patient with of femoral neck fracture.
doi:10.4103/0019-5413.38583
PMCID: PMC2759595  PMID: 19823657
Elderly patient; femoral neck fracture; hip arthroplasty
10.  The Conversion Rate of Bipolar Hemiarthroplasty after a Hip Fracture to a Total Hip Arthroplasty 
Clinics in Orthopedic Surgery  2012;4(2):117-120.
Background
Bipolar hip hemiarthroplasty is used in the management of fractures of the proximal femur. The dual articulation is cited as advantageous in comparison to unipolar prostheses as it decreases acetabular erosion, has a lower dislocation rates and is easier to convert to a total hip arthroplasty (THA) should the need arise. However, these claims are debatable. Our study examines the rate of conversion of the bipolar hemiarthroplasty to THA and the justification for using it on the basis of future conversion to THA.
Methods
All cases of bipolar hemiarthroplasty performed in our unit for hip fractures over a 9-year period (1999-2007) were reviewed. Medical notes and radiographs of all patients were reviewed, and all surviving patients that were contactable received a telephone follow-up.
Results
Of all 164 patients reviewed with a minimum of 1 year from date of surgery, 4 patients had undergone a conversion of their bipolar prosthesis to THA. Three conversions were performed for infection, dislocation, and fracture. Only one (0.6%) conversion was performed for groin pain.
Conclusions
Our study show that bipolar hemiarthroplasties for hip fractures have a low conversion rate to THAs and this is comparable to the published conversion rate of unipolar hemiarthroplasties.
doi:10.4055/cios.2012.4.2.117
PMCID: PMC3360183  PMID: 22662296
Hip fracture; Bipolar arthroplasty; Total hip arthroplasty
11.  A 42-year-old patient presenting with femoral head migration after hemiarthroplasty performed 22 years earlier: a case report 
Introduction
Treatment of femoral neck fractures in young adults may require total hip arthroplasty or hip hemiarthroplasty using a bipolar cup. The latter can, however, result in migration of the femoral head and poor long-term results.
Case presentation
We report a case of femoral head migration after hemiarthroplasty performed for femoral neck fracture that had occurred 22 years earlier, when the patient (a Japanese man) was 20 years old. He experienced peri-prosthetic fracture of the femur, subsequent migration of the prosthesis, and a massive bone defect of the pelvic side acetabular roof. After bone union of the femoral shaft fracture, the patient was referred to our hospital for reconstruction of the acetabular roof. Intra-operatively, we placed two alloimplants of bone from around the transplanted femoral head into the weight-bearing region of the acetabular roof using an impaction bone graft method. We then implanted an acetabular roof reinforcement plate and a cemented polyethylene cup in the position of the original acetabular cup. Eighteen months post-operatively, X-rays showed union of the transplanted bone.
Conclusions
Treatment of femoral neck fractures in young adults is usually accomplished by osteosynthesis, but it may be complicated by femoral head avascular necrosis or by infection or osteomyelitis. In such cases, once an infection has subsided, either hip hemiarthroplasty using a bipolar cup or total hip arthroplasty may be required. However, if the acetabular side articular cartilage is damaged, a bipolar cup should not be used. Total hip arthroplasty should be performed to prevent migration of the implant.
doi:10.1186/1752-1947-9-17
PMCID: PMC4326395  PMID: 25592554
Acetabular articular cartilage; Femoral head migration; Femoral neck fracture; Hemiarthroplasty; Infection
12.  Management pitfalls of fractured neck of femur in osteogenesis imperfecta 
Introduction
Fractured neck of femur in osteogenesis imperfecta is rarely reported. Its management is always difficult because of bone fragility and the outcome is not well known. We, therefore, aimed to study the management pitfalls in this group of patients.
Methods
We retrospectively reviewed five cases of fractured neck of femur in four patients treated in our hospital between 2006 and 2009. The demographic data, mode of injury, fracture configuration, treatment, complications, clinical and radiological outcome were reviewed.
Results
According to the Sillence classification, one patient was type I, two were type III and one was type IV. There were two children (aged 8 and 15 years) and two adults (aged 21 and 22 years), with the 8 year-old girl suffering from hip fracture on different sides in two accidents. All five hip fractures were the result of low-energy injury and were associated with other fractures. Two undisplaced fractures required intra-operative fluoroscopic confirmation to demonstrate movement at the fracture site. The interval between the injury and fixation ranged from 6 h to 3 days. One hip required secondary surgery to openly reduce the fracture due to inadequate primary fixation and reduction. Two hips were fixed with paediatric dynamic hip screws and three hips were fixed with cannulated screws. All patients were immobilised in hip spica for 6 weeks. The average follow-up was 4 years (3–5 years). All patients had satisfactory union and none of them developed radiological evidence of avascular necrosis at the latest follow-up. All patients returned to their pre-injury functional level.
Conclusion
Fractured neck of femur is rare given the high prevalence of long bone fractures in osteogenesis imperfecta. They all have characteristic associated fractures of the extremity at the time of injury and neck of femur fractures could be easily missed. Fracture fixation is a great challenge to the orthopaedic surgeons because of the small size of the patients, poor bone quality with suboptimal imaging intra-operatively and compromised purchase of fixation devices. The choice of implants should be determined by the size of the patients and the presence of prior instrumentation close to the hip joint.
doi:10.1007/s11832-013-0495-6
PMCID: PMC3672462  PMID: 24432078
Osteogenesis imperfecta; Fractured neck of femur; Operative challenge
13.  Ceramic-on-Ceramic Total Hip Arthroplasty: Minimum of Six-Year Follow-up Study 
Clinics in Orthopedic Surgery  2013;5(3):174-179.
Background
This study examines the clinical and radiologic results of ceramic-on-ceramic total hip arthroplasties with regard to wear, osteolysis, and fracture of the ceramic after a minimum follow-up of six years.
Methods
We evaluated the results of a consecutive series of 148 primary ceramic-on-ceramic total hip arthroplasties that had been performed between May 2001 and October 2005 in 142 patients. The mean age was 57.2 years (range, 23 to 81 years). The mean follow-up period was 7.8 years (range, 6.1 to 10.1 years). Preoperative diagnosis was avascular necrosis in 77 hips (52%), degenerative arthritis in 36 hips (24.3%), femur neck fracture in 18 hips (12.2%), rheumatoid arthritis in 15 hips (10.1%), and septic hip sequelae in 2 hips (1.4%). Clinical results were evaluated with the Harris hip score, and the presence of postoperative groin or thigh pain. Radiologic analysis was done with special attention in terms of wear, periprosthetic osteolysis, and ceramic failures.
Results
The mean Harris hip score improved from 58.3 (range, 10 to 73) to 92.5 (range, 79 to 100) on the latest follow-up evaluation. At final follow-up, groin pain was found in 4 hips (2.7%), and thigh pain was found in 6 hips (4.1%). Radiologically, all femoral stems demonstrated stable fixations without loosening. Radiolucent lines were observed around the stem in 25 hips (16.9%), and around the cup in 4 hips (2.7%). Endosteal new bone formation was observed around the stem in 95 hips (64.2%) and around the cup in 88 hips (59.5%). No osteolysis was observed around the stem and cup. There were 2 hips (1.4%) of inclination changes of acetabular cup, 2 hips (1.4%) of hip dislocation, 1 hip (0.7%) of ceramic head fracture, and 1 hip (0.7%) of squeaking. The Kaplan-Meier survival rate of the prostheses was 98.1% at postoperative 7.8 years.
Conclusions
The ceramic-on-ceramic total hip arthroplasty produced excellent clinical results and implant survival rates with no detectable osteolysis on a minimum six-year follow-up study. The ceramic-on-ceramic couplings could be a reasonable option of primary total hip arthroplasty for variable indications.
doi:10.4055/cios.2013.5.3.174
PMCID: PMC3758986  PMID: 24009902
Hip; Total hip arthroplasty; Ceramic-on-ceramic
14.  Stress shielding effects of two prosthetic groups after total hip joint simulation replacement 
Objective
The study aims to compare the stress shielding effects of implantable anatomical and traditional prostheses after in vitro total hip joint replacement simulation. The study serves as a biomechanical basis for novel artificial prostheses and for clinical hip joint replacements.
Methods
Sixteen femoral specimens from adult male corpses were randomly divided into two groups: the traditional prosthesis group implanted into femur specimens using simulated total hip joint replacement (n = 8) and the femoral neck-preserved anatomical prosthesis implantation group that used a collum femoris preserving stem/trabeculae oriented pattern (CFP/TOP) acetabular cup (n = 8). The strain values in the two groups before and after prosthesis implantation were measured at different test points using electric resistance strain gauges. The stress shielding rate was calculated according to the related formula.
Results
The results showed that the rates of proximal femoral stress shielding were significantly higher at test points 1–10 in the traditional femoral prosthesis transplantation group than in the anatomical prosthesis group (p < 0.05).
Conclusions
There were different effects of stress shielding between the anatomical and traditional prostheses. Retained femoral anatomical implants should reduce stress shielding and increase the stability of anatomical prosthesis implants.
doi:10.1186/s13018-014-0071-x
PMCID: PMC4237889  PMID: 25174846
Hip joint; Artificial prosthesis; Replacement; Electric measurement
15.  Fractures in the elderly: when is hip replacement a necessity? 
As the world’s population ages, hip fractures pose a significant health care problem. Hip fractures in the elderly are associated with impaired mobility, and increased morbidity and mortality. Associated conditions, such as osteoporosis, medical comorbidity, and dementia, pose a significant concern and determine optimal treatment. One-year mortality rates currently range from 14% to 36%, and care for these patients represents a major global economic burden. The incidence of hip fractures is bimodal in its distribution. Young adult hip fractures are the result of high energy trauma, and the larger peak seen in the elderly population is secondary to low-energy injuries. The predilection for the site of fracture at the neck of femur falls into two major subgroups. Pertrochanteric fractures occur when the injury is extracapsular and the blood supply to the head of femur is unaffected. The management of this group involves internal fixation through a sliding hip screw device or intramedullary fixation device, both of which have good results. The other group of patients who sustain an intracapsular fracture at the femoral neck are at increased risk of nonunion and osteonecrosis. Recent papers in the literature have shown better functional outcomes with a primary hip replacement over other treatment modalities. This article reviews the current literature and indications for a primary total hip replacement in these patients.
doi:10.2147/CIA.S10204
PMCID: PMC3066247  PMID: 21472086
hip fractures; elderly; hip replacement
16.  Different competing risks models applied to data from the Australian Orthopaedic Association National Joint Replacement Registry 
Acta Orthopaedica  2011;82(5):513-520.
Purpose
Here we describe some available statistical models and illustrate their use for analysis of arthroplasty registry data in the presence of the competing risk of death, when the influence of covariates on the revision rate may be different to the influence on the probability (that is, risk) of the occurrence of revision.
Patients and methods
Records of 12,525 patients aged 75–84 years who had received hemiarthroplasty for fractured neck of femur were obtained from the Australian Orthopaedic Association National Joint Replacement Registry. The covariates whose effects we investigated were: age, sex, type of prosthesis, and type of fixation (cementless or cemented). Extensions of competing risk regression models were implemented, allowing the effects of some covariates to vary with time.
Results
The revision rate was significantly higher for patients with unipolar than bipolar prostheses (HR = 1.38, 95% CI: 1.01–1.89) or with monoblock than bipolar prostheses (HR = 1.45, 95% CI: 1.08–1.94). It was significantly higher for the younger age group (75–79 years) than for the older one (80–84 years) (HR = 1.28, 95% CI: 1.05–1.56) and higher for males than for females (HR = 1.37, 95% CI: 1.09–1.71). The probability of revision, after correction for the competing risk of death, was only significantly higher for unipolar prostheses than for bipolar prostheses, and higher for the younger age group. The effect of fixation type varied with time; initially, there was a higher probability of revision for cementless prostheses than for cemented prostheses, which disappeared after approximately 1.5 years.
Interpretation
When accounting for the competing risk of death, the covariates type of prosthesis and sex influenced the rate of revision differently to the probability of revision. We advocate the use of appropriate analysis tools in the presence of competing risks and when covariates have time-dependent effects.
doi:10.3109/17453674.2011.618918
PMCID: PMC3242946  PMID: 21895508
17.  Nonunion of the femoral neck: Possibilities and limitations of the various treatment modalities 
Indian Journal of Orthopaedics  2008;42(1):13-21.
Nowadays in cases of nonunions of the femoral neck, the surgeon is tempted to perform prosthetic replacement of the hip, more so if there is also evidence of avascular necrosis of the head of femur. This provides rapid pain relief and allows early mobilization. However, long-term results of hip arthroplasties, especially in younger people and in the presence of osteopenia, are not always as expected; and a less radical approach is worth considering. The intertrochanteric valgization osteotomy, described by Pauwels, is an excellent alternative for healthy patients up to 65 years of age with a nonunion of the femoral neck. A union rate of 80-90% of the nonunion is described by most authors. Leg length inequallity, rotational and angular deformities can be corrected at the same time. During the period 1973-1995, we performed valgization osteotomy according to Pauwels in 66 patients of, 18-72 years old (mean 49.5 years). 24 (37%) of our patients died 4 months to 24 years (mean: 9.5 years) after the operation. Union of the femoral neck was achieved in 58 (88%) of the 66 patients; union of the osteotomy in 65 patients (99%). A good or excellent result was achieved in 62% (23 uneventful and 13 with healed, necrosis/arthrosis without need for further treatment) of our patients. However, the method has its limits. We feel if there is too little bone stock inside the femoral head, a valgization osteotomy does not give good result. The radiographic signs of avascular necrosis in patients over 30 years of age is considered a contraindication for an osteotomy. However our results show that it is worthwhile trying to save the joint of young patients even in case of a segmental collapse. In the race between revascularization and collapse, often revascularization is the winner. We deliberately give nature its chance and don't rely on the result of bleeding from drill holes in the head, nuclear scans and other methods to estimate vascularity. A secondary total hip replacement if necessary because of avascular necrosis or osteoarthritis is considerably postponed; and better milieu for hip replacement can be achieved by the development of sclerotic bone in the subchondral areas of the acetabulum and femoral head. Between 65 and 80 years of age, a total hip replacement is probably the best option for fit patients. We treat fresh femoral neck fractures with a hemiarthroplasty in patients over the biological age of 80 years. Logically the same choice will be made for patients with a nonunion. During the period 1973-1995 we performed hemiarthroplasty (n = 34) in patient with low general condition. Their mean age was 79 years. The average survival in these patients was less than three years and that explains probably the low late complication rate: in this group. Total hip replacement was performed in 37 younger patients with a mean age of 69 years. They were not considered for a valgization osteotomy because of age being over 70 years, severe osteoporosis or a total collapse of the femoral head. In this group, we observed one aseptic cup revision and two extractions of the prosthesis because of a deep infection.
doi:10.4103/0019-5413.38575
PMCID: PMC2759582  PMID: 19823649
Fracture neck femur; nonunion; osteotomy; prosthetic replacement
18.  Advances in the surgical treatment of fragility fractures of the upper femur 
Fragility fractures typically occur in elderly patients. They are related to osteoporosis, because of the weakening of the bone structure, and are the result of low-energy injuries and often involve the metaphyseal segments of bone. The fracture of the upper extremity of the femur are one of the most typical of the elderly patients. They may be intracapsular (femoral neck fractures) or extracapsular (intertrochanteric fractures). Each kind of fracture can be treated in several ways: the intracapsular fracture can be treated with screws, unipolar or bipolar hemiarthroplasty or even with total arthroplasty. The extracapsular fractures instead can be treated with sliding hip screw, intramedullary nail, femoral neck screws, helical blade or primary arthroplasty. What must be remembered is that osteoporotic bone has distinct morphologic characteristics that influence its biomechanical properties and therefore the choices and techniques for internal fixation. Therefore only a complete understanding of the biology of the osteoporotic bone will lead to a good quality of the treatment of the fragility fractures.
PMCID: PMC2811350  PMID: 22461246
fragility fractures, upper extremity of the femur fractures, osteoporosis.
19.  Early Complications Following Cemented Modular Hip Hemiarthroplasty 
Introduction :
Hemiarthroplasty is the recommended treatment for displaced, intracapsular, femoral neck fractures. This study aimed to evaluate the early complications following insertion of the JRI Furlong cemented hemiarthroplasty, a contemporary, modular, double tapered, polished prosthesis.
Method :
A series of 459 consecutive patients (May 2006 - June 2009) treated with a JRI hemiarthroplasty with a minimum of one-year (1-4years) follow-up were evaluated. Data collected retrospectively from clinical records and hospital databases included patient demographics, mortality, deep infection, dislocation, periprosthetic fracture, and any requirement for revision or complications related to the prosthesis.
Results :
Full data were available for 429 of 459 (93%), partial data for 30 (7%). Average age was 83 years (52-100), 76% were female. One-year mortality was 24%. Intraoperative fractures occurred in 17 patients (3.7%). There were two intraoperative deaths. There were nine early deep wound infections (2%). There were two revisions to total hip replacement (THR), four patients required conversion to THR and one underwent an excision arthroplasty procedure.
Discussion :
Early surgical outcomes for the JRI hemiarthroplasty prosthesis are equivalent or superior to other major hemiarthroplasty prostheses previously reported however, there was a high intraoperative fracture rate of 3.7%. We recommend using a stem one size smaller than the final broach in fragile, osteoporotic bone. No patients re-presented with aseptic loosening or stem failure.
doi:10.2174/1874325001509010015
PMCID: PMC4323769
Cement; fracture; hip; hemiarthroplasty; modular; orthogeriatric.
20.  Early result of hemiarthroplasty in elderly patients with fracture neck of femur 
Background:
Fractured neck of femur is a frequent and severe injury in elderly patients with consequent high morbidity and mortality. Hemiarthroplasty is an established treatment modality for displaced intracapsular femoral neck fractures in elderly patients above 60 years. This study analysed the early functional outcome and complications of Austin Moore endoprosthesis in elderly patients above 60 years with fractured neck of femur.
Materials and Methods:
Retrospective data were obtained over a 5 year period from January 2007 to December 2012. Thirty-five elderly patients of 60 years and above with displaced intracapsular fracture neck of femur treated with hemiarthroplasty using Austin Moore endoprosthesis were included. Data were analysed using SPSS version 21.
Results:
A total of 35 patients were involved. The age-range was 60-90 years with mean age of 69.7 ± 7 years. The predominant mechanism of injury was trivial falls in 18 (66.7%) patients. The commonest complication was pressure sore in 2 (5.7%) patients, followed by surgical site infection in 1 (2.9%) patient and periprosthetic fracture in 1 (2.9%) patients. Early post-operative mortality was 2.9%. Post-operative hip functional status according to Postel and Merle d Aubigne revealed that majority (66.6%) of patients had satisfactory hip function.
Conclusion:
Functional outcome of Austin Moore in elderly patients above 60 years with fracture neck of femur was satisfactory in most of the cases with minimal morbidity. Careful patient selection for hemiarthroplasty is vital and may decrease the incidence of complications and ameliorate the outcomes in the treatment of intracapsular femoral neck fractures.
doi:10.4103/0300-1652.149174
PMCID: PMC4314864  PMID: 25657497
Austin Moore prosthesis; fracture neck femur; hemiarthroplasty
21.  Long-term results of the Wagner cone prosthesis 
International Orthopaedics  2007;33(1):53-58.
The Wagner cone prosthesis is indicated in uncemented total hip replacement of cases with cylinder-shaped femurs, deformed femurs, femurs with increased antetorsion, and in conditions of intramedullary bony scar tissue after previous osteotomies. The objective of this study is to present long-term results. From January 1, 1993 to December 31, 1995, 132 implantations were made with the Wagner cone prosthesis. We report the clinical and radiographic results of 94 cone prostheses with a mean observation period of 11.5 years. The Merle d’Aubigné score improved from a preoperative mean value of 8.8 to a postoperative mean of 16.3. The radiographic evaluation revealed 32 cases with cortical hypertrophy, 73 cases with atrophy of the proximal femur, and 18 cases with complete pedestal formation. Radiolucencies over Gruen zones 1 and 7 occurred in 42 cases; only zone 1 was affected in 24 cases. Complications included three deep infections, three acetabular revisions, five total joint revisions, one recurrent luxation, and three heterotopic ossifications. In spite of the fact that the examined cohort often included patients who had undergone multiple previous operations (a maximum of six) of the proximal femur or the acetabulum, the long-term results of the Wagner cone prostheses were very promising.
doi:10.1007/s00264-007-0460-4
PMCID: PMC2899218  PMID: 17932669
22.  Hip abductor moment arm - a mathematical analysis for proximal femoral replacement 
Background
Patients undergoing proximal femoral replacement for tumor resection often have compromised hip abductor muscles resulting in a Trendelenberg limp and hip instability. Commercially available proximal femoral prostheses offer several designs with varying sites of attachment for the abductor muscles, however, no analyses of these configurations have been performed to determine which design provides the longest moment arm for the hip abductor muscles during normal function.
Methods
This study analyzed hip abductor moment arm through hip adduction and abduction with a trigonometric mathematical model to evaluate the effects of alterations in anatomy and proximal femoral prosthesis design. Prosthesis dimensions were taken from technical schematics that were obtained from the prosthesis manufacturers. Manufacturers who contributed schematics for this investigation were Stryker Orthopaedics and Biomet.
Results
Superior and lateral displacement of the greater trochanter increased the hip abductor mechanical advantage for single-leg stance and adduction and preserved moment arm in the setting of Trendelenberg gait. Hip joint medialization resulted in less variance of the abductor moment arm through coronal motion. The Stryker GMRS endoprosthesis provided the longest moment arm in single-leg stance.
Conclusions
Hip abductor moment arm varies substantially throughout the hip's range of motion in the coronal plane. Selection of a proximal femur endoprosthesis with an abductor muscle insertion that is located superiorly and laterally will optimize hip abductor moment arm in single-leg stance compared to one located inferiorly or medially.
doi:10.1186/1749-799X-6-6
PMCID: PMC3247065  PMID: 21266066
23.  Transfracture abduction osteotomy: A solution for nonunion of femoral neck fractures 
Indian Journal of Orthopaedics  2014;48(1):25-29.
Background:
Nonunion and avascular necrosis (AVN) of the femoral head remains one of the major complications following femoral neck fractures. Despite various surgical techniques and internal fixation devices, the incidence of nonunion and AVN has remained unsolved. Neglected nonunion of femoral neck fracture is common in the developing world. Treatment options include rigid internal fixation with or without bone grafting, muscle pedicle bone graft, valgus osteotomy of the proximal femur with or without bone graft, valgus osteotomy or hip arthroplasty. We conducted a retrospective analysis of cases of nonunion of femoral neck fracture treated by transfracture abduction osteotomy (TFAO).
Materials and Methods:
Over a period of 35 years (1974-2008), 30 patients with nonunion of femoral neck fractures were treated with TFAO over a period of 35 years (1974-2008), All patients were less than 50 years of age. Absence of clinical and radiological signs of union after four months was considered as nonunion. Patients more than 50 years of age were excluded from the study. Union was assessed at 6 months radiologically. Limb length was measured at six months. The mean duration of femoral neck fracture was 19 months (range 4 months 10 years). Results were analyzed in terms of radiological union at six months. Average followup was five years and six months.
Results:
Consistent union was noted at the followup after six months in 29 cases. One case was lost to followup after five and one-half months postoperatively. However, the fracture had united in this case at the last followup. Average shortening of the limb at six months was 1.9 cm. Average neck shaft angle was 127° (range 120-145°). Five cases went into AVN but were asymptomatic. Two cases required reoperation due to back out of Moore's pins. These were reopened and cancellous screws were inserted in the same tracks.
Conclusions:
Consistent union of nonunion femoral neck fracture was noted at the followup after six months in 29 cases. The major drawback of the procedure is immobilization of the patient in the hip spica for eight weeks.
doi:10.4103/0019-5413.125485
PMCID: PMC3931149  PMID: 24600059
Femoral neck fracture; nonunion; transfracture abduction osteotomy
24.  Cementless bipolar hemiarthroplasty in femoral neck fractures in elderly 
Indian Journal of Orthopaedics  2011;45(3):236-242.
Background:
Cemented hip arthroplasty is an established treatment for femoral neck fracture in the mobile elderly. Cement pressurization raises intramedullary pressure and may lead to fat embolization, resulting in fatal bone cement implantation syndrome, particularly in patients with multiple comorbidities. The cementless stem technique may reduce this mortality risk but it is technically demanding and needs precise planning and execution. We report the perioperative mortality and morbidity of cementless bipolar hemiarthroplasty in a series of mobile elderly patients (age >70 years) with femoral neck fractures.
Materials and Methods:
Twenty-nine elderly patients with mean age of 83 years (range:71-102 years) with femoral neck fractures (23 neck of femur and 6 intertrochanteric) were operated over a 2-year period (Nov 2005–Oct 2007). All were treated with cementless bipolar hemiarthroplasty. Clinical and radiological follow-up was done at 3 months, 6 months, 12 months, and then yearly.
Results:
The average follow-up was 36 months (range 26-49 months). The average duration of surgery and blood loss was 28 min from skin to skin (range, 20–50 min) and 260 ml (range, 95–535 ml), respectively. Average blood transfusion was 1.4 units (range, 0 to 4 units) Mean duration of hospital stay was 11.9 days (7–26 days). We had no perioperative mortality or serious morbidity.
We lost two patients to follow-up after 12 months, while three others died due to medical conditions (10–16 months post surgery). Twenty-four patients were followed to final follow-up (average 36 months; range: 26–49 months). All were ambulatory and had painless hips; the mean Harris hip score was 85 (range: 69–96).
Conclusion:
Cementless bipolar hemiarthroplasty for femoral neck fractures in the very elderly permits early return to premorbid life and is not associated with any untoward cardiac event in the perioperative period. It can be considered a treatment option in this select group.
doi:10.4103/0019-5413.80042
PMCID: PMC3087225  PMID: 21559103
Cementless bipolar; femoral neck fractures; comorbidities; elderly
25.  The Geometry of the Bone Structure Associated with Total Hip Arthroplasty 
PLoS ONE  2014;9(3):e91058.
Close adaptation of the prosthesis to the bone is the key to achieving optimal stability and fixation for total hip arthroplasty (THA). However, there have been no adequate studies of bone morphology, especially in different races. The aim of this study was to analyze the geometry of the acetabulum and proximal femur of people from South China, based on three-dimensional reconstruction, and to detect differences between different population subsets. CT scans were performed on 80 healthy volunteers (160 hips) from South China, comprising 40 males (80 hips) and 40 females (80 hips). The images were imported into Mimics 10.01 to perform 3D reconstruction. THA-associated anatomical parameters were measured and compared with other published data. In comparison with published data, it seemed that people from South China have smaller acetabular abduction angle, larger acetabular supro-inferior diameter, larger neck-shaft angle, smaller offset, thinner femoral shaft and more proximal isthmus, which needed to be further confirmed. There were significant differences between the genders in most parameters. As significant differences in canal flare index (CFI) and distal canal flare index (DCFI) were found between genders, it was concluded the most significant differences lay in the isthmus of the femur. Among the femora, according to Noble’s classification we identified more normal types and fewer stovepipe and champagne-flute types than expected from the literature, indicating that uncemented prostheses would be suitable for most people from South China. Our findings reveal that simply choosing the smallest of a series of prostheses would not necessarily provide a good fit, due to the different trends from the proximal to the distal part of the femur. Significant variation exists in THA-associated anatomy between genders and population subsets. It is therefore imperative that each patient receives individual consideration rather than assuming all patients have the same anatomy, especially for different races.
doi:10.1371/journal.pone.0091058
PMCID: PMC3946655  PMID: 24608343

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