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2.  Patient-related risk factors for fracture-healing complications in the United Kingdom General Practice Research Database 
Acta Orthopaedica  2012;83(6):653-660.
Background and purpose
A variety of risk factors have been hypothesized to contribute to the development of fracture-healing complications; however, population-based estimates of the strength of these risk factors are limited. In this case-control study, we evaluated patient-related risk factors for fracture-healing complications.
Methods
Using the United Kingdom General Practice Research Database, we identified patients with a fracture-healing complication (delayed union, nonunion, or malunion) between 1988 and 2008. 4 controls (i.e. patients with normal healing) were matched to each case on general practice, fracture site, fracture date, and length of history in the database. We used conditional logistic regression to estimate odds ratios (ORs) of various risk factors, including demographics, comorbidities, and medication use.
Results
Diabetes and use of non-steroidal anti-inflammatory drugs (NSAIDs) within 12 months before the initial fracture were associated with a higher odds of a fracture-healing complication (type-I diabetes: adjusted OR = 2.3, 95% CI: 1.3–3.8; type-II diabetes: adjusted OR = 2.3, CI: 1.4–3.7; NSAIDs: adjusted OR = 2.6, CI: 2.1–3.2). Patients who had a motor vehicle accident recorded within 1 month before their initial fracture were also at increased odds of a fracture-healing complication (adjusted OR = 2.6, CI: 1.2–5.4).
Interpretation
Diabetes, NSAID use, and a recent motor vehicle accident were most consistently associated with an increased risk of a fracture-healing complication, regardless of fracture site or specific fracture-healing complication. This analysis suggests that certain patient-related characteristics influence the development of fracture-healing complications in general, even though specific healing complications may differ by their mechanism.
doi:10.3109/17453674.2012.747054
PMCID: PMC3555441  PMID: 23140093
3.  Dual-mobility cups for revision due to instability are associated with a low rate of re-revisions due to dislocation 
Acta Orthopaedica  2012;83(6):566-571.
Background and purpose
Revision total hip arthroplasty (THA) due to recurrent dislocations is associated with a high risk of persistent instability. We hypothesized that the use of dual-mobility cups would reduce the risk of re-revision due to dislocation after revision THA.
Patients and methods
228 THA cup revisions (in 228 patients) performed due to recurrent dislocations and employing a specific dual-mobility cup (Avantage) were identified in the Swedish Hip Arthroplasty Register. Kaplan-Meier survival analysis was performed with re-revision due to dislocation as the primary endpoint and re-revision for any reason as the secondary endpoint. Cox regression models were fitted in order to calculate the influence of various covariates on the risk of re-revision.
Results
58 patients (25%) had been revised at least once prior to the index cup revision. The surgical approach at the index cup revision was lateral in 99 cases (44%) and posterior in 124 cases (56%). Median follow-up was 2 (0–6) years after the index cup revision, and by then 18 patients (8%) had been re-revised for any reason. Of these, 4 patients (2%) had been re-revised due to dislocation. Survival after 2 years with the endpoint revision of any component due to dislocation was 99% (95% CI: 97–100), and it was 93% (CI: 90–97) with the endpoint revision of any component for any reason. Risk factors for subsequent re-revision for any reason were age between 50–59 years at the time of the index cup revision (risk ratio (RR) = 5 when compared with age > 75, CI: 1–23) and previous revision surgery to the relevant joint (RR = 1.7 per previous revision, CI: 1–3).
Interpretation
The risk of re-revision due to dislocation after insertion of dual-mobility cups during revision THA performed for recurrent dislocations appears to be low in the short term. Since most dislocations occur early after revision THA, we believe that this device adequately addresses the problem of recurrent instability. Younger age and prior hip revision surgery are risk factors for further revision surgery. However, problems such as potentially increased liner wear and subsequent aseptic loosening may be associated with the use of such devices in the long term.
doi:10.3109/17453674.2012.742395
PMCID: PMC3555442  PMID: 23116439
4.  Development of the Knee Injury and Osteoarthritis Outcome Score for Children (KOOS-Child) 
Acta Orthopaedica  2012;83(6):666-673.
Background and purpose
The Knee Injury and Osteoarthritis Outcome Score (KOOS) is distinguished from other knee-specific measures by the inclusion of separate scales for evaluation of activities of daily living, sports and recreation function, and knee-related quality of life, with presentation of separate subscale scores as a profile. However, its applicability in children has not been established. In this study, we examined how well the KOOS could be understood in a cohort of children with knee injury, with a view to preparing a pediatric version (KOOS-Child).
Material and methods
A trained researcher conducted cognitive interviews with 34 Swedish children who had symptomatic knee injuries (either primary or repeated). They were 10–16 years of age, and were selected to allow for equal group representation of age and sex. All the interviews were recorded. 4 researchers analyzed the data and modified the original KOOS questionnaire.
Results
Many children (n =14) had difficulty in tracking items based on the time frame and an equivalent number of children had trouble in understanding several terms. Mapping errors resulted from misinterpretation of items and from design issues related to the item such as double-barreled format. Most children understood how to use the 5-point Likert response scale. Many children found the instructions confusing from both a lexical and a formatting point of view. Overall, most children found that several items were irrelevant.
Interpretation
The original KOOS is not well understood by children. Modifications related to comprehension, mapping of responses, and jargon in the KOOS were made based on qualitative feedback from the children.
doi:10.3109/17453674.2012.747921
PMCID: PMC3555443  PMID: 23140110
5.  Reverse hybrid and cemented hip replacement compared using radiostereometry and dual-energy X-ray absorptiometry 
Acta Orthopaedica  2012;83(6):592-598.
Background and purpose
Total hip replacement (THR) with a reverse hybrid (RH), a combination of a cemented polyethylene cup and a cementless femoral stem, has been increasingly used in Scandinavia. In a randomized trial, we compared an RH THR with a proximal hydroxyapatite- (HA-) coated stem to a conventional cemented THR. Both groups received the same polyethylene cup.
Patients and methods
51 patients (52 hips) were included. Radiostereometry (RSA) and dual-energy X-ray absorptiometry (DEXA) were performed postoperatively and after 6, 12, and 24 months. 42 patients (43 hips) were followed for 2 years.
Results
Mean cup rotation around the x-axis was 0.13° for the cemented group and –0.24° for the RH group (p = 0.03). Cup migration in the other axes, and stem migration and wear were similar between the 2 study groups. Bone remodeling around the cup was also similar between the groups. Bone loss in Gruen zone 1 was 18% for the cementless stems, as compared to an increase of 1.4% for the cemented ones (p < 0.001). Bone loss was similar in the other Gruen zones. Harris hip score and Oxford hip score were similar pre- and postoperatively in the 2 groups.
Interpretation
In the present study, RH THR with a cementless hydroxyapatite-coated stem and conventional cemented THR did not show any major differences regarding stem migration and bone loss after 2 years of follow-up.
doi:10.3109/17453674.2012.742393
PMCID: PMC3555444  PMID: 23116437
7.  Intraoperative findings and procedures in culturally and geographically different patient and surgeon populations 
Acta Orthopaedica  2012;83(6):577-582.
Background and purpose
Patient and implant registries are important clinical tools in monitoring and benchmarking quality of care. For comparisons amongst registries to be valid, a common data set with comparable definitions is necessary. In this study we compared the patients in the Norwegian Knee Ligament Registry (NKLR) and the Kaiser Permanente Anterior Cruciate Ligament Reconstruction Registry (KP ACLRR) with regard to intraarticular findings, procedures, and graft fixation characteristics reported by the operating surgeon for both primary and revision anterior cruciate ligament reconstructions (ACLRs).
Methods
We performed a cross-sectional comparison of the NKLR and KP ACLRR cohorts registered between 2005 and 2010. Aggregate-level data including patient characteristics (age, sex, and laterality), meniscal and cartilage injury patterns and corresponding treatment procedures, choice of graft, and fixation characteristics (type and component material) were shared between registries. Descriptive analyses were then conducted.
Results
During the study period, 11,217 ACLRs were registered in the NKLR and 11,050 were registered in the KP ACLRR. In the NKLR, hamstring autograft was used more (68% vs. 30%) for primary ACLRs and allograft was used less (0.2% vs. 41%) than in the KP ACLRR. The KP ACLRR reports more meniscal tears among both primary and revision ACLRs (63% and 50% vs. 49% and 36%). The NKLR reports less use of biodegradable fixation devices.
Conclusions
Baseline findings between the NKLR and the KP ACLRR were congruent regarding patient characteristics and most injury patterns, adding to the evidence that comparisons and collaborations between these registries will provide generalizable information to the international orthopedic community. The variation in the treatment, including graft and implant selection and meniscus procedures, between the 2 registries provides opportunities to explore the impact of treatment choices on the outcomes of ACLRs.
doi:10.3109/17453674.2012.741451
PMCID: PMC3555446  PMID: 23116436
8.  Periprosthetic Vancouver type B1 and C fractures treated by locking-plate osteosynthesis 
Acta Orthopaedica  2012;83(6):648-652.
Background and purpose
Historically, the treatment of periprosthetic femoral fractures (PFFs) has been associated with a high frequency of complications and reoperations. The preferred treatment is internal fixation, a revision of the femoral stem, or a combination of both. An improved understanding of plate use during internal fixation, and the introduction of locking-plate osteosynthesis may lead to improved outcome. We evaluated the outcome of Vancouver type B1 and C PFFs treated by locking-plate osteosynthesis, by assessing rates of fracture union and reoperations and by analyzing failure cases.
Patients and methods
From 2002 through 2011, 58 consecutive patients (60 fractures) with low-energy PFF around or below a stable femoral stem, i.e. Vancouver type B1 and C fractures, underwent osteosynthesis with a locking plate. All patients had a total hip replacement (THR). They were followed up clinically and radiographically, with 6 weeks between visits, until fracture union or until death. Fracture union was evaluated 6 months postoperatively.
Results
At a median follow-up time of 23 (0–121) months after PFF, 8 patients (8 fractures) had been reoperated due either to infection (n = 4), failure of fixation (n = 3), or loosening of the femoral stem (n = 1). All the patients who had been followed up for at least 6 months—and who did not undergo reoperation or die—went on to fracture union (n = 43).
Interpretation
Locking-plate osteosynthesis of periprosthetic Vancouver type B1 and C fractures gives good results regarding fracture union. It appears that spanning of the prosthesis to avoid stress-rising areas is important for successful treatment. Infection is the major cause of failure.
doi:10.3109/17453674.2012.747925
PMCID: PMC3555447  PMID: 23140109
9.  More accurate component alignment in navigated total knee arthroplasty has no clinical benefit at 5-year follow-up 
Acta Orthopaedica  2012;83(6):629-633.
Background and purpose
Computer navigation in total knee arthroplasty is somewhat controversial. We have previously shown that femoral component positioning is more accurate with computed navigation than with conventional implantation techniques, but the clinical impact of this is unknown. We now report the 5-year outcome of our previously reported 2-year outcome study.
Methods
78 of initially 84 patients (80 of 86 knees) were clinically and radiographically reassessed 5 (5.1–5.9) years after conventional, image-based, and image-free total knee arthroplasty. The methodology was identical to that used preoperatively and at 2 years, including the Knee Society score (KSS) and the functional score (FS), and AP and true lateral standard radiographs.
Results
Although a more accurate femoral component positioning in the navigated groups was obtained, clinical outcome, number of reoperations, KSS, FS, and range of motion were similar between the groups.
Interpretation
The increased costs and time for navigated techniques did not translate into better functional and subjective medium-term outcome compared to conventional techniques.
doi:10.3109/17453674.2012.747923
PMCID: PMC3555448  PMID: 23140107
10.  Legg-Calvé-Perthes disease and the risk of injuries requiring hospitalization 
Acta Orthopaedica  2012;83(6):572-576.
Background and purpose
Previous studies have suggested that Legg-Calvé-Perthes disease (LCPD) is associated with repetitive trauma, coagulation problems and anatomical abnormalities of the blood supply to the femoral head. The hypothesis that repetitive trauma can affect the blood supply of the femoral head, leading to LCPD, is supported by an animal model. For evidence of an increased risk of repetitive trauma, we investigated whether patients with LCPD have a higher risk for severe injuries requiring hospitalization.
Patients and methods
We identified 2579 patients with LCPD in Sweden during the period 1964–2005. 13,748 individuals without LCPD were randomly selected from the Swedish general population, matched by year of birth, sex and region (control group). Cox proportional hazard regression estimated the risks.
Results
Compared to the control group, patients with LCPD had a modestly raised hazard ratio (HR) of 1.2 (95% CI 1.1–1.3) for injury requiring hospitalization. The risks were slightly higher for soft tissue injuries (HR = 1.3, 95% CI:1.1–1.4) than for fractures (HR = 1.1, 95% CI: 1.0–1.3) and more pronounced among females. Compared to the control group, the higher risk for injury only applied to the lower extremities (HR = 1.2, 95% CI: 1.0–1.4) in patients with LCPD.
Interpretation
Patients with LCPD are vulnerable to injuries which could be interpreted as a marker of hyperactive behavior. It could also implicate that anatomical changes in the bone formation or blood supply of the femoral head – increasing its sensibility for trauma – contribute to the etiology of LCPD.
doi:10.3109/17453674.2012.736167
PMCID: PMC3555449  PMID: 23043293
11.  Metal-on-metal joint bearings and hematopoetic malignancy 
Acta Orthopaedica  2012;83(6):553-558.
Abstract
This is a review of the hip arthroplasty era. We concentrate on new metal bearings, surface replacements, and the lessons not learned, and we highlight recent reports on malignancies and joint implants. A low incidence of blood malignancies has been found in bone marrow taken at prosthetic surgery. The incidence is increased after replacement with knee implants that release very low systemic levels of metal ions. A carcinogenic effect of the high levels of metal ions released by large metal-on-metal implants cannot be excluded. Ongoing Swedish implant registry studies going back to 1975 can serve as a basis for evaluation of this risk.
doi:10.3109/17453674.2012.747055
PMCID: PMC3555450  PMID: 23140092
12.  Screening for osteoporosis reduced new fracture incidence by almost half 
Acta Orthopaedica  2012;83(6):661-665.
Background and purpose
Fractures can be prevented if osteoporosis is identified and treated. In 2002, we initiated a screening program at our orthopedics department, in which patients between 50 and 75 years of age with a wrist, shoulder, vertebral, or hip fracture are assessed by DEXA of the hip and spine and encouraged to see their doctor for decision on treatment regarding osteoporosis. The patients receive written documents containing information, DEXA results, and a letter to their doctor with suggestions regarding blood tests and treatment. In this 6-year follow-up study, we compared the fracture recurrence in 2 groups: patients screened for osteoporosis after fracture as described, and a historical control group with fracture patients who presented at our department 1 year before we started the screening intervention.
Methods
A questionnaire was sent to the 2 groups of fracture patients, those from before the time that we started the screening in 2002 and those who participated in the initial screening study in 2003. The questionnaire included questions on whether they had sustained further fractures, whether they had seen a doctor, and whether treatment had been initiated.
Results
239 of the 306 unscreened patients (68%) and 219 of the 286 screened patients (77%) answered the questionnaire. In the unscreened group, 69 new fractures had occurred, in contrast to 39 in the screened group. The fracture risk was 42% lower in the screened group. Answers regarding treatment were incomplete in the unscreened group.
Interpretation
Screening of fracture patients for osteoporosis reduced fracture recurrence, which indicates that the screening procedure has resulted in treatment that prevents fractures.
doi:10.3109/17453674.2012.747922
PMCID: PMC3555451  PMID: 23140108
13.  Deviation between navigated and final 3-dimensional implant position in mini-invasive unicompartmental knee arthroplasty 
Acta Orthopaedica  2012;83(6):625-628.
Background and purpose
Unicompartmental knee arthroplasty (UKA) is an established method of treating isolated gonartrosis. Modern techniques such as computer-assisted surgery (CAS) and minimally invasive surgery (MIS) are attractive complementary methods to UKA. However, the positioning of the components remains a concern. Thus, we performed a prospective study to assess whether there was deviation between the navigated implant position and the final implant position.
Patients and methods
We performed UKA with MIS and CAS in 13 patients. By comparing intraoperative navigation data with postoperative computed tomography (CT) measurements, we calculated the deviation between the computer-assisted implant position and the final 3-D implant position of the femoral and tibial components.
Results
The computer-assisted placement of the femoral and tibial component showed adequate position and consistent results regarding flexion-extension and varus-valgus. However, regarding rotation there was a large variation and 6 of 10 patients were outside the target range for both the femoral component and the tibial component.
Interpretation
Difficulties in assessing anatomical landmarks with the CAS in combination with MIS might be a reason for the poor rotational alignment of the components.
doi:10.3109/17453674.2012.736840
PMCID: PMC3555452  PMID: 23043273
14.  Early proximal migration of cups is associated with late revision in THA 
Acta Orthopaedica  2012;83(6):583-591.
Background and purpose
The association between excessive early migration of acetabular cups and late aseptic revision has been scantily reported. We therefore performed 2 parallel systematic reviews and meta-analyses to determine the association between early migration of acetabular cups and late aseptic revision.
Methods
One review covered early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were classified according the Swedish Hip Arthroplasty Register and the Australian National Joint Replacement Registry: < 5% revision at 10 years.
Results
Following an elaborate literature search, 26 studies (involving 700 cups) were included in the RSA review and 49 studies (involving 38,013 cups) were included in the survival review. For every mm increase in 2-year proximal migration, there was a 10% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, proximal migration of up to 0.2 mm was considered acceptable and proximal migration of 1.0 mm or more was considered unacceptable. Cups with proximal migration of between 0.2 and 1.0 mm were considered to be at risk of having revision rates higher than 5% at 10 years.
Interpretation
There was a clinically relevant association between early migration of acetabular cups and late revision due to loosening. The proposed migration thresholds can be implemented in a phased evidence-based introduction, since they allow early detection of high-risk cups while exposing a small number of patients.
doi:10.3109/17453674.2012.745353
PMCID: PMC3555453  PMID: 23126575
15.  Early migration of tibial components is associated with late revision 
Acta Orthopaedica  2012;83(6):614-624.
Purpose
We performed two parallel systematic reviews and meta-analyses to determine the association between early migration of tibial components and late aseptic revision.
Methods
One review comprised early migration data from radiostereometric analysis (RSA) studies, while the other focused on revision rates for aseptic loosening from long-term survival studies. Thresholds for acceptable and unacceptable migration were determined according to that of several national joint registries: < 5% revision at 10 years.
Results
Following an elaborate literature search, 50 studies (involving 847 total knee prostheses (TKPs)) were included in the RSA review and 56 studies (20,599 TKPs) were included in the survival review. The results showed that for every mm increase in migration there was an 8% increase in revision rate, which remained after correction for age, sex, diagnosis, hospital type, continent, and study quality. Consequently, migration up to 0.5 mm was considered acceptable during the first postoperative year, while migration of 1.6 mm or more was unacceptable. TKPs with migration of between 0.5 and 1.6 mm were considered to be at risk of having revision rates higher than 5% at 10 years.
Interpretation
There was a clinically relevant association between early migration of TKPs and late revision for loosening. The proposed migration thresholds can be implemented in a phased, evidence-based introduction of new types of knee prostheses, since they allow early detection of high-risk TKPs while exposing only a small number of patients.
doi:10.3109/17453674.2012.747052
PMCID: PMC3555454  PMID: 23140091
16.  Good short-term outcome of primary total hip arthroplasty with cementless bioactive glass ceramic bottom-coated implants 
Acta Orthopaedica  2012;83(6):599-603.
Background and purpose
Cementless total hip arthroplasty is currently favored by many orthopedic surgeons. The design of the porous surface is critically important for long-term fixation. We examined the clinical and radiographic outcome of the cementless titanium hip implant with a bottom coating of apatite-wollastonite containing bioactive glass ceramic.
Methods
We retrospectively reviewed 109 hips (92 patients) that had undergone primary cementless total hip arthroplasty with bioactive glass ceramic bottom-coated implants. The mean follow-up period was 7 (3–9) years. Hip joint function was evaluated with the Merle d’Aubigné and Postel hip score, and radiographic changes were determined from anteroposterior radiographs.
Results
The mean hip score improved from 9.7 preoperatively to 17 at the final follow-up. The overall survival rate was 100% at 9 years, when radiographic loosening or revision for any reason was used as the endpoint. 3 stems in 2 patients subsided more than 3 mm vertically within 1 year after implantation. Radiographs of the interface of the stem and femur were all classified as bone ingrowth fixation.
Conclusions
The short-term results of this study show good outcome for cementless implants with a bottom coating of apatite-wollastonite containing bioactive glass ceramic.
doi:10.3109/17453674.2012.736173
PMCID: PMC3555455  PMID: 23043270
17.  Evaluation of a single preoperative dose of etoricoxib for postoperative pain relief in therapeutic knee arthroscopy 
Acta Orthopaedica  2012;83(6):642-647.
Background and purpose
Analgesics can have undesirable effects. We assessed whether a single preoperative dose of 120 mg etoricoxib reduces the need for additional opioids after therapeutic arthroscopic knee surgery.
Methods
A double-blind, placebo-controlled study was performed at a single center. 66 patients scheduled to undergo elective therapeutic knee arthroscopy were included. They were randomly selected to be given either 120 mg of etoricoxib (n = 33) or placebo (n = 33) 1 hour before induction of general anesthesia. A patient-controlled analgesia device was used postoperatively. We recorded total postoperative morphine consumption over 24 h, degree of pain as assessed with a visual analog scale, degree of satisfaction, and occurrence of adverse effects.
Results
Mean total morphine consumption during the first 24 h was 24 (9–60) mg in the placebo group and 9 (0–34) mg in the etoricoxib group. In the etoricoxib group, pain intensity levels at rest were reduced and patient satisfaction with the analgesia provided was higher during the first postoperative day. There was no difference in the incidence of typical adverse effects of opioids in the 2 groups.
Interpretation
Etoricoxib is a suitable premedication to use before therapeutic arthroscopic knee surgery, as it reduced patients’ morphine requirements.
doi:10.3109/17453674.2012.747053
PMCID: PMC3555457  PMID: 23140090
18.  Is mortality after hip fracture associated with surgical delay or admission during weekends and public holidays? 
Acta Orthopaedica  2012;83(6):609-613.
Background and purpose
Hip fractures are associated with high mortality, but the cause of this is still not entirely clear. We investigated the effect of surgical delay, weekends, holidays, and time of day admission on mortality in hip fracture patients.
Patients and methods
Using data from the Danish National Indicator Project, we identified 38,020 patients admitted from 2003 to 2010. Logistic regression analysis was used to study the association between sex, age, weekend or holiday admission, night-time admission, time to surgery, and ASA score on the one hand and mortality on the other.
Results
The risk of death in hospital increased with surgical delay (odds ratio (OR) = 1.3 per 24 h of delay), ASA score (OR (per point added) = 2.3), sex (OR for men 2.2), and age (OR (per 5 years) = 1.4). The mortality rate for patients admitted during weekends or public holidays, or at night, was similar to that found for those admitted during working days.
Interpretation
Minimizing surgical delay is the most important factor in reducing mortality in hip fracture patients.
doi:10.3109/17453674.2012.747926
PMCID: PMC3555458  PMID: 23140106
19.  Minimally invasive surgery did not improve outcome compared to conventional surgery following unicompartmental knee arthroplasty using local infiltration analgesia 
Acta Orthopaedica  2012;83(6):634-641.
Background and purpose
There has recently been interest in the advantages of minimally invasive surgery (MIS) over conventional surgery, and on local infiltration analgesia (LIA) during knee arthroplasty. In this randomized controlled trial, we investigated whether MIS would result in earlier home-readiness and reduced postoperative pain compared to conventional unicompartmental knee arthroplasty (UKA) where both groups received LIA.
Patients and methods
40 patients scheduled for UKA were randomized to a MIS group or a conventional surgery (CON) group. Both groups received LIA with a mixture of ropivacaine, ketorolac, and epinephrine given intra- and postoperatively. The primary endpoint was home-readiness (time to fulfillment of discharge criteria). The patients were followed for 6 months.
Results
We found no statistically significant difference in home-readiness between the MIS group (median (range) 24 (21–71) hours) and the CON group (24 (21–46) hours). No statistically significant differences between the groups were found in the secondary endpoints pain intensity, morphine consumption, knee function, hospital stay, patient satisfaction, Oxford knee score, and EQ-5D. The side effects were also similar in the two groups, except for a higher incidence of nausea on the second postoperative day in the MIS group.
Interpretation
Minimally invasive surgery did not improve outcome after unicompartmental knee arthroplasty compared to conventional surgery, when both groups received local infiltration analgesia. The surgical approach (MIS or conventional surgery) should be selected according to the surgeon’s preferences and local hospital policies.
ClinicalTrials.gov. (Identifier NCT00991445).
doi:10.3109/17453674.2012.736169
PMCID: PMC3555459  PMID: 23043272
20.  The type of surgical approach influences the risk of revision in total hip arthroplasty 
Acta Orthopaedica  2012;83(6):559-565.
Background and purpose
The most common surgical approaches in total hip arthroplasty in Sweden are the posterior and the anterolateral transgluteal approach. Currently, however, there is insufficient evidence to prefer one over the other regarding risk of subsequent surgery.
Patients and methods
We searched the Swedish Hip Arthroplasty Register between the years 1992 and 2009 to compare the posterior and anterolateral transgluteal approach regarding risk of revision in the 3 most common all-cemented hip prosthesis designs in Sweden. 90,662 total hip replacements met the inclusion criteria. We used Cox regression analysis for estimation of prosthesis survival and relative risk of revision due to dislocation, infection, or aseptic loosening.
Results
Our results show that for the Lubinus SPII prosthesis and the Spectron EF Primary prosthesis, the anterolateral transgluteal approach gave an increased risk of revision due to aseptic loosening (relative risk (RR) = 1.3, 95% CI: 1.0–1.6 and RR = 1.6, CI: 1.0–2.5) but a reduced risk of revision due to dislocation (RR = 0.7, CI: 0.5–0.8 and RR = 0.3, CI: 0.1–0.4). For the Exeter Polished prosthesis, the surgical approach did not affect the outcome for dislocation or aseptic loosening. The surgical approach had no influence on the risk of revision due to infection in any of these designs.
Interpretation
This observational study shows that the surgical approach affected the risk of revision due to aseptic loosening and dislocation for 2 of the most commonly used cemented implants in Sweden. Further studies are needed to determine whether these results are generalizable to other implants and to uncemented fixation.
doi:10.3109/17453674.2012.742394
PMCID: PMC3555460  PMID: 23116440
21.  10-year results of a new low-monomer cement 
Acta Orthopaedica  2012;83(6):604-608.
Background and purpose
The properties and performance of a new low-monomer cement were examined in this prospective randomized, controlled RSA study. 5-year data have already been published, showing no statistically significant differences compared to controls. In the present paper we present the 10-year results.
Methods
44 patients were originally randomized to receive total hip replacement with a Lubinus SPII titanium-aluminum-vanadium stem cemented either with the new Cemex Rx bone cement or with control bone cement, Palacos R. Patients were examined using RSA, Harris hip score, and conventional radiographs.
Results
At 10 years, 33 hips could be evaluated clinically and 30 hips could be evaluated with RSA (16 Cemex and 14 Palacos). 9 patients had died and 4 patients were too old or infirm to be investigated. Except for 1 hip that was revised for infection after less than 5 years, no further hips were revised before the 10-year follow-up. There were no statistically significant clinical differences between the groups. The Cemex cement had magnitudes of migration similar to or sometimes lower than those of Palacos cement. In both groups, most hips showed extensive radiolucent lines, probably due to the use of titanium alloy stems.
Interpretation
At 10 years, the Cemex bone cement tested performed just as well as the control (Palacos bone cement).
doi:10.3109/17453674.2012.742392
PMCID: PMC3555461  PMID: 23116438
22.  Good function after shoulder arthroplasty 
Acta Orthopaedica  2012;83(5):467-473.
Background and purpose
Different results after shoulder arthroplasty have been found for different diagnostic groups. We evaluated function, pain, and quality of life after shoulder arthroplasty in 4 diagnostic groups.
Patients and methods
Patients with shoulder arthroplasties registered in the Norwegian Arthroplasty Register from 1994 through 2008 were posted a questionnaire in 2010. 1,107 patients with rheumatoid arthritis (RA), osteoarthritis (OA), acute fracture (AF), or fracture sequela (FS) returned completed forms (65% response rate). The primary outcome measure was the Oxford shoulder score (OSS), which assesses symptoms and function experienced by the patient on a scale from 0 to 48. A secondary outcome measure was the EQ-5D, which assesses life quality. The patients completed a questionnaire concerning symptoms 1 month before surgery, and another concerning the month before they received the questionnaire.
Results
Patients with RA and OA had the best results with a mean improvement in OSS of 16 units, as opposed to 11 for FS patients. Both shoulder pain and function had improved substantially. The change in OSS for patients with AF was negative (–11), but similar end results were obtained for AF patients as for RA and OA patients. Quality of life had improved in patients with RA, OA, and FS.
Interpretation
Good results in terms of pain relief and improved level of function were obtained after shoulder arthroplasty for patients with RA, OA, and—to a lesser degree—FS. A shoulder arthropathy had a major effect on quality of life, and treatment with shoulder replacement substantially improved it.
doi:10.3109/17453674.2012.720118
PMCID: PMC3488172  PMID: 22950481
23.  Effects of hydroxyapatite coating of cups used in hip revision arthroplasty 
Acta Orthopaedica  2012;83(5):427-435.
Background and purpose
Coating of acetabular revision implants with hydroxyapatite (HA) has been proposed to improve ingrowth and stability. We investigated whether HA coating of revision cups can reduce the risk of any subsequent re-revision.
Methods
We studied uncemented cups either with or without HA coating that were used at a primary acetabular revision and registered in the Swedish Hip Arthroplasty Register (SHAR). 2 such cup designs were identified: Harris-Galante and Trilogy, both available either with or without HA coating. These cups had been used as revision components in 1,780 revisions of total hip arthroplasties (THA) between 1986 and 2009. A Cox proportional hazards model including the type of coating, age at index revision, sex, cause of cup revision, cup design, the use of bone graft at the revision procedure, and the type of cup fixation at primary THA were used to calculate adjusted risk ratios (RRs with 95% CI) for re-revision for any reason or due to aseptic loosening.
Results
71% of the cups were coated with HA and 29% were uncoated. At a mean follow-up time of 6.9 (0–24) years, 159 (9%) of all 1,780 cups had been re-revised, mostly due to aseptic loosening (5%), dislocation (2%), or deep infection (1%). HA coating had no significant influence on the risk of re-revision of the cup for any reason (RR = 1.4, CI: 0.9–2.0) or due to aseptic loosening (RR = 1.1, 0.6–1.9). In contrast, HA coating was found to be a risk factor for isolated liner re-revision for any reason (RR = 1.8, CI: 1.01–3.3). Age below 60 years at the index cup revision, dislocation as the cause of the index cup revision, uncemented cup fixation at primary THA, and use of the Harris-Galante cup also increased the risk of re-revision of the cup. In separate analyses in which isolated liner revisions were excluded, bone grafting was found to be a risk factor for re-revision of the metal shell due to aseptic loosening (RR = 2.1, CI: 1.05–4.2).
Interpretation
We found no evidence to support the notion that HA coating improves the performance of the 2 studied cup designs in revision arthroplasty. In contrast, patient-related factors such as younger age and dislocation as the reason for cup revision, and technical factors such as the choice of revision cup were found to influence the risk of subsequent re-revision of the cup. The reason for inferior results after revision of uncemented cups is not known, but it is possible that these hips more often had pronounced bone loss at the index cup revision.
doi:10.3109/17453674.2012.720117
PMCID: PMC3488167  PMID: 22937978
24.  Low revision rate after total hip arthroplasty in patients with pediatric hip diseases 
Acta Orthopaedica  2012;83(5):436-441.
Background
The results of primary total hip arthroplasties (THAs) after pediatric hip diseases such as developmental dysplasia of the hip (DDH), slipped capital femoral epiphysis (SCFE), or Perthes’ disease have been reported to be inferior to the results after primary osteoarthritis of the hip (OA).
Materials and methods
We compared the survival of primary THAs performed during the period 1995–2009 due to previous DDH, SCFE, Perthes’ disease, or primary OA, using merged individual-based data from the Danish, Norwegian, and Swedish arthroplasty registers, called the Nordic Arthroplasty Register Association (NARA). Cox multiple regression, with adjustment for age, sex, and type of fixation of the prosthesis was used to calculate the survival of the prostheses and the relative revision risks.
Results
370,630 primary THAs were reported to these national registers for 1995–2009. Of these, 14,403 THAs (3.9%) were operated due to pediatric hip diseases (3.1% for Denmark, 8.8% for Norway, and 1.9% for Sweden) and 288,435 THAs (77.8%) were operated due to OA. Unadjusted 10-year Kaplan-Meier survival of THAs after pediatric hip diseases (94.7% survival) was inferior to that after OA (96.6% survival). Consequently, an increased risk of revision for hips with a previous pediatric hip disease was seen (risk ratio (RR) 1.4, 95% CI: 1.3–1.5). However, after adjustment for differences in sex and age of the patients, and in fixation of the prostheses, no difference in survival was found (93.6% after pediatric hip diseases and 93.8% after OA) (RR 1.0, CI: 1.0–1.1). Nevertheless, during the first 6 postoperative months more revisions were reported for THAs secondary to pediatric hip diseases (RR 1.2, CI: 1.0–1.5), mainly due to there being more revisions for dislocations (RR 1.8, CI: 1.4–2.3). Comparison between the different diagnosis groups showed that the overall risk of revision after DDH was higher than after OA (RR 1.1, CI: 1.0–1.2), whereas the combined group Perthes’ disease/SCFE did not have a significantly different risk of revision to that of OA (RR 0.9, CI: 0.7–1.0), but had a lower risk than after DDH (RR 0.8, CI: 0.7–1.0).
Interpretation
After adjustment for differences in age, sex, and type of fixation of the prosthesis, no difference in risk of revision was found for primary THAs performed due to pediatric hip diseases and those performed due to primary OA.
doi:10.3109/17453674.2012.736171
PMCID: PMC3488168  PMID: 23043269
25.  The risk of revision due to dislocation after total hip arthroplasty depends on surgical approach, femoral head size, sex, and primary diagnosis 
Acta Orthopaedica  2012;83(5):442-448.
Background and purpose
The effects of patient-related and technical factors on the risk of revision due to dislocation after primary total hip arthroplasty (THA) are only partly understood. We hypothesized that increasing the femoral head size can reduce this risk, that the lateral surgical approach is associated with a lower risk than the posterior and minimally invasive approaches, and that gender and diagnosis influence the risk of revision due to dislocation.
Patients and methods
Data on 78,098 THAs in 61,743 patients performed between 2005 and 2010 were extracted from the Swedish Hip Arthroplasty Register. Inclusion criteria were a head size of 22, 28, 32, or 36 mm, or the use of a dual-mobility cup. The covariates age, sex, primary diagnosis, type of surgical approach, and head size were entered into Cox proportional hazards models in order to calculate the adjusted relative risk (RR) of revision due to dislocation, with 95% confidence intervals (CI).
Results
After a mean follow-up of 2.7 (0–6) years, 399 hips (0.5%) had been revised due to dislocation. The use of 22-mm femoral heads resulted in a higher risk of revision than the use of 28-mm heads (RR = 2.0, CI: 1.2–3.3). Only 1 of 287 dual-mobility cups had been revised due to dislocation. Compared with the direct lateral approach, minimally invasive approaches were associated with a higher risk of revision due to dislocation (RR = 4.2, CI: 2.3–7.7), as were posterior approaches (RR = 1.3, CI: 1.1–1.7). An increased risk of revision due to dislocation was found for the diagnoses femoral neck fracture (RR = 3.9, CI: 3.1–5.0) and osteonecrosis of the femoral head (RR = 3.7, CI: 2.5–5.5), whereas women were at lower risk than men (RR = 0.8, CI: 0.7–1.0). Restriction of the analysis to the first 6 months after the index procedure gave similar risk estimates.
Interpretation
Patients with femoral neck fracture or osteonecrosis of the femoral head are at higher risk of dislocation. Use of the minimally invasive and posterior approaches also increases this risk, and we raise the question of whether patients belonging to risk groups should be operated using lateral approaches. The use of femoral head diameters above 28 mm or of dual-mobility cups reduced this risk in a clinically relevant manner, but this observation was not statistically significant.
doi:10.3109/17453674.2012.733919
PMCID: PMC3488169  PMID: 23039167

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