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Year of Publication
1.  Conversion of a failed hip resurfacing arthroplasty to total hip arthroplasty: pearls and pitfalls 
Surface replacement arthroplasty (SRA) remains a viable alternative to total hip arthroplasty (THA) in appropriately selected, active adults with degenerative hip disease. However, orthopedic surgeons are facing a number of scenarios where revision of one or both components of an SRA is indicated. Indications for revision vary and impact the potential outcomes of conversion of a SRA to THA. While clinical outcomes are generally favorable, a growing body of data illustrates patients who undergo conversion of a SRA to THA to be at increased risk of requiring a repeat revision surgery and experiencing functional outcomes inferior to that of a primary THA. The results of patients undergoing conversion of a SRA to THA highlight the need for careful patient selection, thorough preoperative counseling, and technical precision when performing a SRA. Furthermore, a systematic approach to the failed SRA is necessary to ensure optimal clinical results.
doi:10.1007/s12178-016-9326-y
PMCID: PMC4762797  PMID: 26803608
Surface replacement arthroplasty; Total hip arthroplasty; Metallosis; Femoral neck fracture; Aseptic loosening
2.  The Use of Warfarin for DVT Prophylaxis Following Hip and Knee Arthroplasty: How Often Are Patients Within Their Target INR Range? 
The Journal of arthroplasty  2014;30(2):315-319.
The purpose of this study was to determine the percentage of time that patients are subtherapeutic, therapeutic, and supratherapeutic based on the recommended INR for therapeutic efficacy when prescribed warfarin for chemical thromboprophylaxis following a hip or knee arthroplasty procedure. One hundred eighty-four patients receiving warfarin for 4 weeks postoperatively, dosed using a web-application accounting for patient demographics, INR levels, and concomitant medication use, were included for analysis. On average, patients with a target INR range between 1.7-2.7 were therapeutic for only 54.4% of the time (32.5% subtherapeutic, 13.0 supratherapeutic) while patients with a target INR range between 2.0 and 3.0 were therapeutic for only 45.9% of the time (39.2% subtherapeutic, 14.8% supratherapeutic) of their warfarin regimen. This study confirms that patients receiving warfarin for chemical thromboprophylaxis are within their targeted INR range for only a limited period of time during their postoperative course.
doi:10.1016/j.arth.2014.08.032
PMCID: PMC4324127  PMID: 25261182
total knee arthroplasty; warfarin; coumadin; thromboprophylaxis
3.  New Total Knee Arthroplasty Designs: Do Young Patients Notice? 
Background
Although the volume of total knee arthroplasties (TKAs) performed in the United States continues to increase, recent reports have shown the percentage of patients who remain “unsatisfied” is as high as 15% to 30%. Recently, several newer implant designs have been developed to potentially improve patient outcomes.
Questions/purposes
The purpose of this study was to determine the impact of high-flex, gender-specific, and rotating-platform TKA designs on patient satisfaction and functional outcomes.
Methods
A four-center study was designed to quantify the degree of residual symptoms and functional deficits in patients undergoing TKA with newer implant designs compared with a 10-year-old, cruciate-retaining (CR) TKA system introduced in 2003. Each contributing surgeon was fellowship-trained and specialized in joint replacement surgery. Only patients younger than 60 years old were included. Data were collected by an independent, third-party survey center blinded to the implant type, who administered questionnaires about patient satisfaction, residual symptoms, function, and pre- and postoperative activity levels using previously published survey instruments. Two hundred thirty-seven CR, 137 rotating-platform, 88 gender-specific, and 65 high-flex TKAs were included in the analysis. Differences in baseline demographic variables were accounted for using multiple logistic regression statistical analyses.
Results
Patients who received certain newer designs reported more residual symptoms (grinding, popping, and clicking) in the 30 days before survey administration than the group receiving a 10-year-old CR design (CR, 24% [57 of 237 patients] versus gender-specific, 36% [32 of 88 patients]; odds ratio [OR], 2.1; 95% confidence interval [CI], 1.1–3.8; p = 0.03; and rotating-platform, 43% [59 of 137 patients]; OR, 2.2; 95% CI, 1.3–3.7; p < 0.001). They also reported more functional problems, including getting in and out of a chair (CR, 19% [46 of 237 patients] versus gender-specific, 37% [32 of 88 patients]; OR, 1.0; 95% CI, 1.1–3.5; p = 0.001). Patients with newer TKA designs did not demonstrate any improvements in function or patient satisfaction versus those who received the 10-year-old CR design.
Conclusions
When interviewed by an independent, blinded third party, the use of newer implant designs did not improve patient satisfaction and the presence of residual symptoms when compared with patients who received the 10-year-old CR design. Future studies should prospectively determine whether the purported benefits of newer implant designs improve patient-perceived outcomes.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-014-3713-8
PMCID: PMC4390919  PMID: 24903823
4.  What Are the Advantages and Disadvantages of Imaging Modalities to Diagnose Wear-related Corrosion Problems? 
Background
Adverse tissue reactions are known to occur after total hip arthroplasty using both conventional and metal-on-metal (MoM) bearings and after MoM hip resurfacing arthroplasty (SRA). A variety of imaging tools, including ultrasound (US), CT, and MRI, have been used to diagnose problems associated with wear after MoM hip arthroplasty and corrosion at the head-trunnion junction; however, the relative advantages and disadvantages of each remain a source of controversy.
Questions/purposes
The purposes of this review were to evaluate the advantages and disadvantages of (1) US; (2) CT; and (3) MRI as diagnostic tools in the assessment of wear-related corrosion problems after hip arthroplasty.
Methods
A systematic literature review was performed through Medline, EMBASE, Scopus CINAHL, and the Cochrane Library without time restriction using search terms related to THA, SRA, US, CT, MRI, adverse tissue reactions, and corrosion. Inclusion criteria were Level I through IV studies in the English language, whereas expert opinions and case reports were excluded. The quality of included studies was judged by their level of evidence, method of intervention allocation, outcome assessments, and followup of patients. Four hundred ninety unique results were returned and 40 articles were reviewed.
Results
The prevalence of adverse local tissue reactions in both asymptomatic and symptomatic patients varies based on the method of evaluation (US, CT, MRI) and imaging protocols. US is accessible and relatively inexpensive, yet has not been used to report synovial thicknesses in the setting of wear-related corrosion. CT scans are highly sensitive and provide information regarding component positioning but are limited in providing enhanced soft tissue contrast and require ionizing radiation. MRI has shown promise in predicting both the presence and severity of adverse local tissue reactions but is more expensive.
Conclusions
All three imaging modalities have a role in the assessment of adverse local tissue reactions and tribocorrosion after total hip arthroplasty. Although US may serve as a screening technique for the detection of larger periprosthetic collections, only MRI has been shown to predict the severity of tissue destruction found at revision and correlate to the degree of tissue necrosis at histologic evaluation.
doi:10.1007/s11999-014-3579-9
PMCID: PMC4397750  PMID: 24664197
5.  Relationship of the Posterior Femoral Axis of the “Kinematically Aligned” Total Knee Arthroplasty to the Posterior Condylar, Transepicondylar, and Anteroposterior Femoral Axes 
The Knee  2014;21(6):1120-1123.
Background
A recent proposed modification in surgical technique in total knee arthroplasty (TKA) has been the introduction of the “kinematically aligned” TKA, in which the angle and level of the posterior joint line of the femoral component and joint line of the tibial component are aligned to those of the “normal,” pre-arthritic knee. The purpose of this study was to establish the relationship of the posterior femoral axis of the “kinematically aligned” total knee arthroplasty (TKA) to the traditional axes used to set femoral component rotation.
Methods
114 consecutive, unselected patients with preoperative MRI images undergoing TKA were retrospectively reviewed. The transepicondylar axis (TEA), posterior condylar axis (PCA), antero-posterior axis (APA) of the trochlear groove, and posterior femoral axis of the kinematically aligned TKA (KAA) were templated on axial MRI images by two, independent observers. The relationships between the KAA, TEA, APA, and PCA were determined, with a negative value indicating relative internal rotation of the axis.
Results
On average, the KAA was 0.5° externally rotated relative to the PCA (minimum of -3.6°, maximum of 5.8°), -4.0° internally rotated relative to the TEA (minimum of -10.5°, maximum of 2.3°), and -96.4° internally rotated relative to the APA (minimum of -104.5°, maximum of -88.5°). Each of these relationships exhibited a wide range of potential values.
Conclusions
Using a kinematically aligned surgical technique internally rotates the posterior femoral axis relative to the transepicondylar axis, which significantly differs from current alignment instrument targets.
doi:10.1016/j.knee.2014.07.025
PMCID: PMC4267996  PMID: 25112211
kinematic alignment; total knee arthroplasty; femoral rotation; transepicondylar axis; flexion-extension axis
6.  What is the Prognosis of Revision Total Hip Arthroplasty in Patients 55 Years and Younger? 
Background
Revision THAs are expected to increase; however, few studies have characterized the prognosis of revision THAs in younger patients.
Questions/purposes
We performed a case-control study to evaluate intermediate-term survivorship, complications, and hip and activity scores after revision THAs in patients 55 years and younger, compared these outcomes with the results of primary THAs in a matched patient population, and evaluated risk factors for failed revisions.
Methods
Ninety-three patients (103 hips) had a minimum of 4 years after revision THA, died, or had rerevision surgery. They were matched with 98 patients (103 hips) with primary THAs. Survivorship, complications, and clinical outcomes were compared between the groups using t-tests. Risk factors for failure also were assessed with chi-square analysis.
Results
At mean followup of 6.7 years, 71 revision THAs (69%) survived, compared with 102 (99%) primary THAs (odds ratio [OR], 45.9; 95% CI, 16.5–128.4; p < 0.001). Complications occurred in 29% of the revision group and 6% of the primary group (OR, 6.64; 95% CI, 4.14–10.67; p < 0.001). After revision THA, the average improvement in Harris hip score was 19.2 compared with 34.4 after primary THA (p < 0.001). The UCLA activity score improved by an average of 0.87 after revision compared with 2.36 after primary THA (p < 0.001). Conventional polyethylene was associated with failure after revision THA (OR, 2.98; 95% CI, 1.87–4.76; p = 0.004).
Conclusions
At intermediate-term followup, young patients undergoing revision THAs had markedly higher failure and complication rates and more modest clinical improvements compared with patients in a matched cohort who had primary THAs.
Level of Evidence
Level III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3377-9
PMCID: PMC3971212  PMID: 24249534
7.  Evaluation of the 3-Dimensional, Weight-bearing Orientation of the Normal Adult Knee 
The Journal of arthroplasty  2013;29(5):906-911.
The purpose of this study was to use 3-dimensional, weight-bearing images corrected for rotation to establish normative data of limb alignment and joint line orientation in asymptomatic, adult knees. One hundred adults (200 lower extremities) were recruited to receive weight-bearing, simultaneous biplanar imaging of both lower extremities. Multiple radiographic parameters were measured from 3D images, corrected for limb rotation. 70.0% of knees were in neutral, 19.5% in varus, and 10.5% in valgus overall alignment. Only 31 % of knees possessed both a neutral mechanical axis and the absence of joint line obliquity. There was substantial agreement between the 2D and 3D images for overall mechanical alignment (κ=0.77), but only a moderate agreement for joint line obliquity (κ=0.58). A substantial portion of asymptomatic adults possess either a varus or valgus mechanical alignment and joint line obliquity,
doi:10.1016/j.arth.2013.10.024
PMCID: PMC4017250  PMID: 24315446
8.  Are Younger Patients Undergoing TKAs Appropriately Characterized As Active? 
Background
The use of TKAs in young patients is increasing. Demographic characteristics and activity levels among this patient group may affect implant selection, performance, and survivorship. Patient age (≤ 55 years) and preoperative diagnosis have been used to define this patient group, with the presumption that these patients are more active than older patients with similar indications for TKA.
Questions/purposes
We questioned whether (1) demographic features of young patients support high activity expectations after TKA, and (2) preoperative or postoperative functional activity measures support projections that young patients are active after TKA.
Methods
We retrospectively compared demographic characteristics (gender, BMI, diagnosis) and functional activity profile (as determined by preoperative and postoperative UCLA activity score and functional subscores of The Knee Society and WOMAC instruments) for 150 patients 55 years old or younger (181 TKAs) and 262 patients who were between 65 to 75 years old (314 TKAs) at the time of surgery.
Results
Younger patients having TKAs were significantly more likely than older patients to be female (74% versus 60%, p < 0.001) and to have diagnoses other than osteoarthritis (18% versus 3%, p < 0.001). BMI was significantly greater among younger female patients than among other age and gender combinations (35 kg/m2 versus 31 kg/m2, p < 0.001). Male patients had higher mean postoperative UCLA activity scores (5.5 versus 4.4, p < 0.001), Knee Society function subscores (80.2 versus 66.4, p < 0.001), and WOMAC function subscores (82.8 versus 74.2, p < 0.01) compared with female patients, but these were not different in older versus younger patients.
Conclusions
Sustained high activity levels are not likely to be a principal cause of revision TKAs among younger patients when considering age and diagnosis alone. Determining the effect of activity on survivorship of prosthetic designs and techniques should be based on measured functional activity instead of using age and diagnosis as surrogates for activity.
Level of Evidence
Level III, therapeutic study. See the Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3376-x
PMCID: PMC3940741  PMID: 24249533
9.  Impact of Socioeconomic Factors on Outcome of Total Knee Arthroplasty 
Background
Few data exist regarding the impact of socioeconomic factors on results of current TKA in young patients. Predictors of TKA outcomes have focused primarily on surgical technique, implant details, and individual patient clinical factors. The relative importance of these factors compared to patient socioeconomic status is not known.
Questions/purposes
We determined whether (1) socioeconomic factors, (2) demographic factors, or (3) implant factors were associated with satisfaction and functional outcomes after TKA in young patients.
Methods
We surveyed 661 patients (average age, 54 years; range, 18–60 years; 61% female) 1 to 4 years after undergoing modern primary TKA for noninflammatory arthritis at five orthopaedic centers. Data were collected by an independent third party with expertise in collecting healthcare data for state and federal agencies. We examined specific questions regarding satisfaction, pain, and function after TKA and socioeconomic (household income, education, employment) and demographic (sex, minority status) factors. Multivariable analysis was conducted to examine the relative importance of these factors for each outcome of interest.
Results
Patients reporting incomes of less than USD 25,000 were less likely to be satisfied with TKA outcomes and more likely to have functional limitations after TKA than patients with higher incomes; no other socioeconomic factors were associated with satisfaction. Women were less likely to be satisfied and more likely to have functional limitations than men, and minority patients were more likely to have functional limitations than nonminority patients. Implants were not associated with outcomes after surgery.
Conclusions
Socioeconomic factors, in particular low income, are more strongly associated with satisfaction and functional outcomes in young patients after TKA than demographic or implant factors. Future studies should be directed to determining the causes of this association, and studies of clinical results after TKA should consider stratifying patients by socioeconomic status.
Level of Evidence
Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3002-y
PMCID: PMC3889415  PMID: 23633182
10.  High Level of Residual Symptoms in Young Patients After Total Knee Arthroplasty 
Background
TKA is among the fastest growing interventions in medicine, with procedure incidence increasing the most in younger patients. Global knee scores have a ceiling effect and do not capture the presence of difficulty or dissatisfaction with specific activities important to patients.
Questions/purposes
We quantified the degree of residual symptoms and specific functional deficits in young patients who had undergone TKA.
Methods
In a national multicenter study, we quantified the degree of residual symptoms and specific functional deficits in 661 young patients (mean age, 54 years; range, 19–60 years; 61% female) at 1 to 4 years after primary TKA. To eliminate observer bias, satisfaction and function data were collected by an independent, third-party survey center with expertise in administering medical outcomes questionnaires for federal agencies.
Results
Overall, 89% of patients were satisfied with their ability to perform normal daily living activities, and 91% were satisfied with their pain relief. After TKA, 66% of patients indicated their knees felt normal, 33% reported some degree of pain, 41% reported stiffness, 33% reported grinding/other noises, 33% reported swelling/tightness, 38% reported difficulty getting in and out of a car, 31% reported difficulty getting in and out of a chair, and 54% reported difficulty with stairs. After recovery, 47% reported complete absence of a limp and 50% had participated in their most preferred sport or recreational activity in the past 30 days.
Conclusions
When interviewed by an independent third party, about 1/3 of young patients reported residual symptoms and limitations after modern TKA. We recommend informing patients considering surgery about the high likelihood of residual symptoms and limitations after contemporary TKA, even when performed by experienced surgeons in high-volume centers, and taking specific steps to set patients’ expectations to a level that is likely to be met by the procedure as it now is performed.
Level of Evidence
Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3229-7
PMCID: PMC3889453  PMID: 24061845
11.  Do Patients Return to Work After Total Knee Arthroplasty? 
Background
Although there is extensive literature supporting a high success rate, there are limited data on return to work after total knee arthroplasty (TKA).
Questions/purposes
We sought to determine (1) the percentage of patients who returned to work after TKA; (2) what percentage returned to their original job; (3) whether this varied based on the physical job demand category; and (4) whether there were differences between men and women in terms of the likelihood of returning to work after TKA.
Methods
A multicenter study was conducted of patients of working age (18–60 years) who underwent TKA 1 to 5 years previously. An independent third-party survey center with expertise in collecting healthcare data for state and federal agencies collected the data. Definitions from the US Department of Labor’s Dictionary of Occupational Titles were used to determine physical job demand categories of sedentary, light, medium, heavy, and very heavy. Complete data were collected on 661 patients undergoing TKA (average age 54 years, 61% women).
Results
Seventy-five percent (494 of 661) were employed in the 3 months before their TKA and 98% (482 of 494) returned to work after surgery; 89% (440 of 494) returned to the same job. Before surgery, physical demand categories of the patients’ jobs were sedentary 12%, light 10%, medium 24%, heavy 24%, and very heavy 30%. The return to work rate for those employed during the 3 months before surgery by physical demand category was sedentary 95%, light 91%, medium 100%, heavy 98%, and very heavy 97%. Men were more likely than women to have worked within the 3 months before TKA but there was no difference between sexes in return to work after TKA.
Conclusions
In this group of young patients, most returned to work at their usual occupation after TKA.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-3099-z
PMCID: PMC3889457  PMID: 23761175
12.  Do Young, Active Patients Perceive Advantages After Surface Replacement Compared to Cementless Total Hip Arthroplasty? 
Background
Potential advantages suggested but not confirmed for surface replacement arthroplasty (SRA) over THA include lower frequency of limp, less thigh pain, less limb length discrepancy, and higher activity.
Questions/purposes
We therefore determined whether patients having SRA had a limp, thigh pain, or limb length discrepancy less frequently or had activity levels higher than patients having THA.
Methods
In a multicenter study, we surveyed 806 patients aged 18 to 60 years with a premorbid UCLA activity score of 6 or more who underwent hip arthroplasty for noninflammatory arthritis at one of five orthopaedic centers. Patients had either a cementless THA with an advanced bearing surface (n = 682) or an SRA (n = 124). The patients were demographically comparable. Specific telephone survey instruments were designed to assess limp, thigh pain, perception of limb length, and activity levels. Minimum followup was 1 year (mean, 2.3 years; range, 1.1–3.9 years).
Results
When controlled for age, sex, and premorbid activity level, patients with SRA had a higher incidence of complete absence of any limp, lower incidence of thigh pain, lower incidence of perception of limb length discrepancy, greater ability to walk continuously for more than 60 minutes, higher percentage of patients who ran after surgery, greater distance run, and higher percentage of patients who returned to their most favored recreational activity.
Conclusions
When interviewed by an independent third party, patients with SRA reported higher levels of function with fewer symptoms and less perception of limb length discrepancy compared to a similar cohort of young, active patients with THA.
Level of Evidence
Level III, therapeutic study. See Instructions for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-013-2915-9
PMCID: PMC3825884  PMID: 23508842
14.  Is Pain and Dissatisfaction After TKA Related to Early-grade Preoperative Osteoarthritis? 
Background
There is growing evidence to suggest many patients experience pain and dissatisfaction after TKA. The relationship between preoperative osteoarthritis (OA) severity and postoperative pain and dissatisfaction after TKA has not been established.
Questions/Purposes
We explored the relationship between early-grade preoperative OA with pain and dissatisfaction after TKA by (1) determining the incidence of early-grade preoperative OA in painful TKAs with no other identifiable abnormality; and (2) comparing this incidence with the incidence of early-grade OA in three other cohorts of patients undergoing TKA.
Methods
We evaluated all (n = 49) painful TKAs in a 1-year period that had no evidence of loosening, instability, malalignment, infection, or extensor mechanism dysfunction and classified the degree of preoperative OA according to the scale of Kellgren and Lawrence. For comparison, we identified three other cohorts of TKAs from the same center and classified their preoperative grade of OA: Group B (n = 100) was a consecutive series of primary TKAs performed for OA during the same year; Group C (n = 80) were asymptomatic TKAs from 1 to 4 years postoperatively; and Group D (n = 80) were TKAs with some degree of pain at 1 to 4 years postoperatively.
Results
Patients in Group A had a higher incidence of early-grade OA is preoperatively (49%) compared with any of the comparison groups: Group B, 5%; Group C, 6%; and Group D, 10%.
Conclusions
A high percentage of patients referred for unexplained pain after TKA had early-grade osteoarthritis preoperatively. Patients undergoing TKA for less than Grade 3 or 4 OA should be informed that they may be at higher risk for persistent pain and dissatisfaction.
Level of Evidence
Level III, prognostic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-012-2465-6
PMCID: PMC3528890  PMID: 22923158
15.  Computer-assisted Total Knee Arthroplasty Is Currently of No Proven Clinical Benefit: A Systematic Review 
Background
Navigated total knee arthroplasty (TKA) may improve coronal alignment outliers; however, it is unclear whether navigated TKA improves the long-term clinical results of TKA.
Questions/Purposes
Does the literature contain evidence of better long-term function and lower revision rates with navigated TKA compared with conventional TKA?
Methods
A systematic literature review was conducted of navigated TKA reviewing articles related to coronal alignment, clinical knee and function scores, cost, patient satisfaction, component rotation, anteroposterior and mediolateral stability, complications, and longer-term reports.
Results
Coronal plane alignment is improved with navigated TKA with fewer radiographic outliers. We found limited evidence of improvements in any other variable, and function was not improved. The duration of surgery is increased and there are unique complications related to navigated TKA. The long-term benefits of additional increase in accuracy of alignment are not supported by any current evidence.
Conclusions
The findings in reports of navigated TKA should be interpreted with caution. There are few short- and medium- and no long-term studies demonstrating improved clinical outcomes using navigated TKA. Despite substantial research, contradictory findings coupled with reservations about the cost and efficacy of the technology have contributed to the failure of computer navigation to become the accepted standard in TKA. Longer-term studies demonstrating improved function, lower revision rates, and acceptable costs are required before navigated TKA may be widely adopted. In the future, with improvements in study design, methodology, imaging, navigation technology, newer functional outcome tools, and longer-term followup studies, we suspect that navigated TKA may demonstrate yet unrecognized benefits.
doi:10.1007/s11999-012-2528-8
PMCID: PMC3528921  PMID: 22948522
16.  Does Standing Affect Acetabular Component Inclination and Version After THA? 
Background
Avoiding complications after hip arthroplasty with hard-on-hard bearings, especially metal-on-metal, correlates with the position of the acetabular component. Supine imaging with conventional radiography has traditionally been utilized to assess component inclination (abduction), as well as anteversion, after THA and surface replacement arthroplasty (SRA). However, most adverse events with hard bearings (excessive wear and squeaking) have occurred with loading. Standing imaging, therefore, should provide more appropriate measurements.
Questions/purposes
We determined whether standing changed standard measurements of acetabular component position using a novel biplanar imaging system compared to traditional supine imaging.
Methods
We performed simultaneous biplanar standing imaging of the lower extremity with a novel imaging system using low radiation collimated beam on 46 patients who underwent THA (23) or SRA (23). Patients who had previously undergone THA had standard CT scans performed. For patients who underwent SRA, we compared acetabular inclination in the supine versus double-limb and single-limb standing.
Results
Standing anteversion differed from supine anteversion by greater than 5° for 12 of 23 patients who underwent THA (range, 5°–16°). For patients who underwent SRA, 13 of 23 patients exhibited a difference of greater than 3° in inclination between supine and double-limb standing images, and six of 23 patients exhibited a difference of greater than 3° in inclination between supine and single-limb standing images.
Conclusions
Standing changed the acetabular inclination and version in a substantial percentage of patients undergoing hip arthroplasty.
doi:10.1007/s11999-012-2391-7
PMCID: PMC3462863  PMID: 22610527
18.  Are Patient-specific Cutting Blocks Cost-effective for Total Knee Arthroplasty? 
Background
Using patient-specific cutting blocks for TKA increases the cost to the hospital for these procedures, but it has been proposed they may reduce operative times and improve implant alignment, which could reduce the need for revision surgery.
Questions/purposes
We compared TKAs performed with patient-specific cutting blocks with those performed with traditional instrumentation to determine whether there was improved operating room time management and component coronal alignment to support use of this technology.
Methods
We retrospectively reviewed 57 patients undergoing primary TKAs using patient-specific custom cutting blocks for osteoarthritis and compared them with 57 matched patients undergoing TKAs with traditional instrumentation during the same period (January 2009 to September 2010). At baseline, the groups were comparable with respect to age, sex, and BMI. We collected data on operative time (total in-room time and tourniquet time) and measured component alignment on plain radiographs.
Results
On average, TKAs performed with patient-specific instrumentation had similar tourniquet times (61.0 versus 56.2 minutes) but patients were in the operating room 12.1 minutes less (137.2 versus 125.1 minutes) than those in the standard instrumentation group. We observed no difference in the femorotibial angle in the coronal plane between the two groups.
Conclusions
Patient-specific instrumentation for TKA shows slight improvement in operating room time management but none in component alignment postoperatively. Therefore, routine use of this new technology may not be cost-effective in its current form.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-011-2221-3
PMCID: PMC3270159  PMID: 22183476
19.  Do Patient-specific Guides Improve Coronal Alignment in Total Knee Arthroplasty? 
Background
Coronal alignment may impact clinical outcome and survivorship in TKA. Patient-specific instrumentation has been developed to restore mechanical or kinematic axis and potentially reduce component malpositioning. Although it is clear these instruments add cost, it is unclear whether they improve alignment.
Questions/purposes
We determined whether the mean coronal alignment after TKA performed with conventional versus patient-specific instrumentation better restored the mechanical and kinematic axes and whether there were more outliers with one of the two methods.
Methods
We retrospectively evaluated 150 primary TKAs performed for osteoarthritis: Group 1 (n = 50) conventional instrumentation; Group 2 (n = 50) patient-specific instrumentation restoring the mechanical axis; Group 3 (n = 50) patient-specific instrumentation restoring the kinematic axis, and measured femorotibial angle, hip-knee-ankle angle, and the zone of the mechanical axis from scout CT images taken 0 to 6 weeks postoperatively.
Results
The mean femorotibial angle differed between the groups: Group 1 had the greatest varus mean alignment and most varus outliers. The mean hip-knee angle was similar between Groups 1 and 2, with Group 3 having greater valgus mean alignment and the most valgus outliers. For the zone of the mechanical axis, Groups 1 and 2 had similar percentages of outliers (40% versus 32%), whereas Group 3 had a greater number of outliers (64%) that were valgus.
Conclusions
TKAs with patient-specific instrumentation restoring the mechanical axis had a similar number of outliers as conventional instrumentation with both groups having more varus outliers than TKAs with patient-specific instrumentation restoring kinematic axis, which had more valgus outliers. Therefore, additional studies are needed to determine whether patient-specific instrumentation improves clinical function or patient satisfaction and whether their routine use can be justified in primary TKA.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-011-2222-2
PMCID: PMC3270188  PMID: 22183477
20.  Causes of Failure of Ceramic-on-Ceramic and Metal-on-Metal Hip Arthroplasties 
Background
Few large series of hard bearing surfaces have reported on reasons for early failure. A number of unique mechanisms of failure, including fracture, squeaking, and adverse tissue reactions, have been reported with these hard bearing surfaces. However, the incidence varies among the published studies.
Questions/purposes
To confirm the incidences, we identified the etiologies of early failures of hard-on-hard bearing surfaces for ceramic-on-ceramic and metal-on-metal THAs.
Methods
We retrospectively reviewed records of 2907 THAs with hard-on-hard bearing surfaces implanted between 1996 and 2009; 1697 (58%) had ceramic-on-ceramic and 1210 (42%) had metal-on-metal bearing surfaces. We recorded bearing-related complications and compared them to nonspecific reasons for revision THA. The minimum followup of the ceramic-on-ceramic and metal-on-metal cohorts was 6 months (mean, 48 months; range, 6–97 months) and 24 months (mean, 60 months; range, 24–178 months), respectively.
Results
The overall revision rate for ceramic-on-ceramic THA was 2.2% (38 of 1697), with aseptic loosening accounting for 55% of revisions (femur or acetabulum). The bearing accounted for 13% of the revisions in the ceramic-on-ceramic THA cohort. The overall metal-on-metal revision rate was 5.4% (65 of 1210), 17 involving adverse tissue reactions related to the metal-on-metal bearing surface (17 of 1210, 1.4% of cases; 17 of 65, 26% of revisions).
Conclusions
Twenty-six percent of the revisions from metal-on-metal and 13% of ceramic-on ceramic were bearing related. The overall short- to medium-term revision rate was 2.2% and 5.4% for ceramic-on-ceramic and metal-on-metal, respectively. The most common etiology of failure was loosening of the femoral or acetabular components.
Level of Evidence
Level IV, therapeutic study. See the Guidelines for Authors for a complete description of level of evidence.
doi:10.1007/s11999-011-2161-y
PMCID: PMC3254760  PMID: 22045071
21.  2011 Marshall Urist Young Investigator Award: When to Release Patients to High-impact Activities after Hip Resurfacing 
Background
Surface replacement arthroplasties are commonly performed in young, active patients who desire return to high-impact activities including heavy manual labor and recreational sports. Femoral neck fracture is an arthroplasty-related complication unique to surface replacement arthroplasty. However, it is unclear regarding whether patients are at lower risk for fracture after a certain postoperative time.
Questions/purposes
We therefore raised the following questions: (1) does stress shielding occur after surface replacement arthroplasty, and (2) when does bone mineral density return to normal so patients can return to high-impact activities without excessive risk of fracture?
Patients and Methods
We prospectively enrolled 90 patients (96 hips) with either surface replacement arthroplasty or THA, and performed dual energy x-ray absorptiometry scans at 6 weeks, 6 months, 1 year, and 2 years. We analyzed bone density by Gruen zone in both groups, and six femoral neck zones in the patients who had surface replacement arthroplasties. We calculated 6-month, 1-year, and 2-year ratios for the change in bone density compared with baseline.
Results
Bone density was greater in patients who had surface replacement arthroplasties than for patients who had THAs at 6 months and 1 year in Gruen Zones 1, 2, 6, and 7, with the largest increase in femoral neck bone density on the tension side at 6 months in Zone L1. We saw no decrease in bone density in patients who had surface replacement arthroplasties in any Gruen zone at any time, and observed no decrease in bone density in female patients.
Conclusions
Increased bone density at 6 months postoperatively in patients who had surface replacement arthroplasties provides evidence that clinically relevant stress shielding does not occur after surface replacement arthroplasty. Owing to the increased bone mineral density at 6 months, we believe patients who underwent surface replacement arthroplasties may to return to high-impact activities at that time without increased risk of fracture.
doi:10.1007/s11999-011-2131-4
PMCID: PMC3237978  PMID: 22006198
22.  Aspirin Decreases Heterotopic Ossification After Hip Resurfacing 
Background
Heterotopic ossification (HO) is a concern for patients undergoing hip surgery, especially surface replacement arthroplasty (SRA) who tend to be younger, more active, and anticipate good motion. It is unclear, however, whether HO occurs more frequently after SRA than traditional total hip arthroplasty (THA) and whether aspirin influences the risk.
Questions/purposes
We therefore determined the incidence of HO after hip resurfacing compared with THA and determined whether aspirin influenced the incidence or severity of HO.
Methods
Retrospectively we compared three patient cohorts: SRA with aspirin (176 hips; 160 patients), SRA with warfarin (60 hips; 57 patients), and THA with warfarin (240 hips; 222 patients). All patients satisfied the same selection criteria and all surgeries were performed through the posterolateral approach using spinal anesthesia. HO was classified using the technique of Brooker et al. comparing the preoperative, immediate postoperative, and 6- to 12-month followup radiographs (minimum, 1 year; mean, 2.7 years).
Results
In the SRA with aspirin group, HO was detected in four of 151 hips (2.6%; two Grade I; one Grade II; one Grade III); in the SRA with warfarin group, eight of 46 hips (17.4%) had HO with four hips (8.7%) having severe HO (Grade III). All 12 patients with HO in both SRA groups were male. The HO incidence and severity was less for the SRA patients treated with aspirin compared with those treated with warfarin. In the THA with warfarin control group, HO was detected in five of 189 hips (2.6%; two Grade I; three Grade II). The HO incidence and severity were the same between the THA with warfarin and the SRA with aspirin cohorts.
Conclusions
The risk of HO is greater in SRA than in THA in patients treated with warfarin postoperatively; aspirin appears to decrease the incidence and severity of HO after hip resurfacing surgery to a similar level as total hip arthroplasty.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-011-1846-6
PMCID: PMC3094639  PMID: 21409458
23.  Pharmacogenetic Warfarin Dose Refinements Remain Significantly Influenced by Genetic Factors after One Week of Therapy 
Thrombosis and Haemostasis  2011;107(2):232-240.
Summary
Introduction
By guiding initial warfarin dose, pharmacogenetic (PGx) algorithms may improve the safety of warfarin initiation. However, once INR response is known, the contribution of PGx to dose refinements is uncertain. This study sought to develop and validate clinical and PGx dosing algorithms for warfarin dose refinement on days 6–11 after therapy initiation.
Materials and Methods
An international sample of 2,022 patients at 13 medical centers on 3 continents provided clinical, INR, and genetic data at treatment days 6–11 to predict therapeutic warfarin dose. Independent derivation and retrospective validation samples were composed by randomly dividing the population (80%/20%). Prior warfarin doses were weighted by their expected effect on S-warfarin concentrations using an exponential-decay pharmacokinetic model. The INR divided by that “effective” dose constituted a treatment response index.
Results
Treatment response index, age, amiodarone, body surface area, warfarin indication, and target INR were associated with dose in the derivation sample. A clinical algorithm based on these factors was remarkably accurate: in the retrospective validation cohort its R2 was 61.2% and median absolute error (MAE) was 5.0 mg/week. Accuracy and safety was confirmed in a prospective cohort (N=43). CYP2C9 variants and VKORC1-1639 G→A were significant dose predictors in both the derivation and validation samples. In the retrospective validation cohort, the PGx algorithm had: R2= 69.1% (P<0.05 vs. clinical algorithm), MAE= 4.7 mg/week.
Conclusions
A pharmacogenetic warfarin dose-refinement algorithm based on clinical, INR, and genetic factors can explain at least 69.1% of therapeutic warfarin dose variability after about one week of therapy.
doi:10.1160/TH11-06-0388
PMCID: PMC3292349  PMID: 22186998
warfarin; VKORC1; CYP2C9; pharmacogenetic
24.  The Incidence of Acetabular Osteolysis in Young Patients With Conventional versus Highly Crosslinked Polyethylene 
Background
Osteolysis is a major mode of hip implant failure. Previous literature has focused on the amount of polyethylene wear comparing highly crosslinked polyethylene (HXPLE) with conventional liners but has not clarified the relative incidence of osteolysis with these two liners.
Questions/purposes
We determined (1) the incidence of osteolysis in HXLPE versus conventional polyethylene (CPE), (2) the ability to detect and evaluate the size of lytic lesions using radiographs compared with CT scans, (3) head penetration in hips without and with lysis, and (4) determined whether acetabular position, head size, and UCLA activity score contributed to lysis.
Methods
We compared head penetration and osteolysis on plain radiographs and presence and volume of osteolysis on CT scans in 48 patients with HXLPE (mean, 46.5 years) and 50 patients with CPE (mean, 43.2 years). The minimum followup was 5 years (average, 7.2 years; range, 5.1–10.9 years),
Results
Osteolysis was apparent on CT in a larger number of patients with CPE liners than HXLPE liners: 12 of 50 (24%) versus one of 48 (2%), respectively. We found no correlation between head penetration and volume of osteolytic lesions. Head penetration was greater in patients with osteolysis. Smaller head sizes were associated with greater wear and those with osteolysis had smaller head sizes; however, there was no difference in acetabular component position or UCLA activity in those with lysis compared with those without.
Conclusions
HXLPE diminished the incidence of osteolysis, but the lack of correlation between penetration and volume of osteolysis suggests other factors other than wear contribute to the development of osteolysis.
Level of Evidence
Level III, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
doi:10.1007/s11999-010-1518-y
PMCID: PMC3018187  PMID: 20824407
25.  The Frank Stinchfield Award: The Impact of Socioeconomic Factors on Outcome After THA: A Prospective, Randomized Study 
Background
Most studies of total hip arthroplasty (THA) focus on the effect of the type of implant on the clinical result. Relatively little data are available on the impact of the patient’s preoperative status and socioeconomic factors on the clinical results following THA.
Questions/purposes
We determined the relative importance of patient preoperative and socioeconomic status compared to implant and technique factors in predicting patient outcome as reflected by scores on commonly utilized rating scales (eg, Harris Hip Score, WOMAC, SF-12, degree of patient satisfaction, or presence or severity of thigh pain) following cementless THA.
Methods
All patients during the study period were offered enrollment in a prospective, randomized study to receive either a titanium, tapered, proximally coated stem; or a Co-Cr, cylindrical, extensively coated stem; 102 patients were enrolled. We collected detailed patient data preoperatively including diagnosis, age, gender, insurance status, medical comorbidities, tobacco and alcohol use, household income, educational level, and history of treatment for lumbar spine pathology. Clinical evaluation included Harris Hip Score, SF-12, WOMAC, pain drawing, and UCLA activity rating and satisfaction questionnaire. Implant factors included stem type, stem size, fit in the canal, and stem-bone stiffness ratios. Minimum 2 year followup was obtained in 95% of the enrolled patients (102 patients).
Results
Patient demographics and preoperative status were more important than implant factors in predicting the presence of thigh pain, dissatisfaction, and a low hip score. The most predictive factors were ethnicity, educational level, poverty level, income, and a low preoperative WOMAC score or preoperative SF-12 mental component score. No implant parameter correlated with outcome or satisfaction.
Conclusion
Socioeconomic factors and preoperative status have more impact on the clinical outcome of cementless THA than implant related factors.
Level of Evidence
Level I, prospective, randomized clinical trial. See the guidelines online for a complete description of level of evidence.
doi:10.1007/s11999-010-1519-x
PMCID: PMC3018201  PMID: 20717856

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