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1.  Predictors of Activity Limitation and Dependence on Walking Aids following Primary Total Hip Arthroplasty 
Journal of the American Geriatrics Society  2010;58(12):10.1111/j.1532-5415.2010.03182.x.
To study function outcomes and their predictors after primary total hip arthroplasty (THA).
Prospective Cohort Study
Single Institution
All patients who underwent primary THA at our institution between 1993 and 2005 and were alive at the time of follow-up.
Whether sex, age, body mass index (BMI), comorbidity, anxiety, and depression predict moderate to severe activity limitation (limitation in ≥3 activities) and complete dependence on waling aids 2 and 5 years after primary THA was examined. Multivariable logistic regression adjusted for operative diagnosis, American Society of Anesthesiologists score, implant type, and distance from medical center.
At 2 years, 30.3% of participants reported moderate to severe activity limitation; at 5 years, 35% of participants reported moderate to severe activity limitation. Significant predictors of moderate to severe activity limitations at 2-year follow-up were female sex (odds ratio (OR)=1.2, 95% confidence interval (CI)=1.1–1.4), aged 71 to 80 (OR=2.0, 95% CI=1.6–2.5), aged 80 and older (OR=4.5, 95% CI=3.4–6.0), depression (OR=2.1, 95% CI=1.6–2.7), and BMI greater than 30. At 5-year follow-up, significant predictors were aged 71 to 80 (OR=1.7, 95% CI=1.3–2.2), older than 80 (OR=4.3, 95% CI=2.8–6.6), depression (OR=2.3, 95% CI=1.6–3.4), and BMI greater than 30.Significant predictors of complete dependence on walking aids at 2 years were female sex (OR=2.0, 95% CI=1.4–2.7), aged 71 to 80 (OR=2.4, 95% CI=1.4–4.2), older than 80 (OR=11.4, 95% CI=6.0–21.9), higher Deyo-Charlson score (OR=1.5, 95% CI=(1.1–1.2) for 5-point increase, depression (OR=2.0, 95% CI=1.2–3.4), and BMI greater than 35. Each of these factors also significantly predicted complete dependence on walking at 5-year follow-up, with similar odds ratios, except that BMI 30–34.9 was not significantly associated.
Higher BMI, depression, older age, and female sex predict activity limitation and complete dependence on walking aids 2 and 5 years after primary THA.
PMCID: PMC3850176  PMID: 21143444
Primary Total Hip Arthroplasty; THA; Predictors; Activity Limitation; Function; walking aids
2.  Higher Body Mass Index Is Not Associated with Worse Pain Outcomes After Primary or Revision Total Knee Arthroplasty (TKA) 
The Journal of arthroplasty  2010;26(3):366-374.e1.
We assessed whether higher Body Mass Index (BMI) is associated with higher risk of moderate-severe knee pain 2- and 5-years after primary or revision Total Knee Arthroplasty (TKA). We adjusted for gender, age, comorbidity, operative diagnosis and implant fixation in multivariable logistic regression. BMI (reference, <25 kg/m2) was not associated with moderate-severe knee pain at 2-years post-primary TKA (odds ratio (95% confidence interval): 25-29.9, 1.02 (0.75,1.39), p=0.90; 30-34.9, 0.93 (0.65,1.34), p=0.71; 35-39.9, 1.16 (0.77,1.74), p=0.47; ≥40, 1.09 (0.69,1.73), (all p-values ≥0.47). Similarly, BMI was not associated with moderate-severe pain at 5-year primary TKA and at 2- and 5-yr revision TKA follow-up. Lack of association of higher BMI with poor pain outcomes post-TKA implies that TKA should not be denied to obese patients for fear of suboptimal outcomes.
PMCID: PMC2930933  PMID: 20413245
3.  Failed Metal-on-Metal Hip Arthroplasties: A Spectrum of Clinical Presentations and Operative Findings 
A number of recent reports have described novel failure mechanisms of metal-on-metal bearings in total and resurfacing hip arthroplasty. Hip arthroplasties with metal-on-metal articulations are also subject to the traditional methods of failure seen with different bearing couples. There is currently little information in the literature to help guide timely clinical evaluation and management of these patients.
We therefore describe the (1) clinical presentations; (2) reasons for failure; (3) operative findings; and (4) histologic findings in patients with failed metal-on-metal hip arthroplasties.
We retrospectively identified all 37 patients (37 hips) with metal on metal total hip or resurfacing arthroplasties who underwent revision over the past 3 years at our institution. Relevant clinical, radiographic, laboratory, intraoperative, and histopathologic findings were analyzed for all patients.
Of the 37 patients, 10 were revised for presumed hypersensitivity specific to the metal-on-metal articulation. This group included eight patients with tissue histology confirming chronic inflammation with lymphocytic infiltration, eight with aseptic loosening of a monoblock screwless uncemented acetabular component, two with iliopsoas impingement associated with a large-diameter femoral head, and three with femoral neck fracture after resurfacing arthroplasty; the remainder of the patients were revised for infection, instability, component malposition, and periprosthetic fracture.
Increased awareness of the modes of failure will bring to light the potential complications particular to metal-on-metal articulations while placing these complications into the context of failures associated with all hip arthroplasties. This novel clinical information should be valuable for the practicing surgeon faced with this patient population.
Level of Evidence
Level IV, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.
PMCID: PMC2919884  PMID: 20559767
4.  C-Reactive Protein, Erythrocyte Sedimentation Rate and Orthopedic Implant Infection 
PLoS ONE  2010;5(2):e9358.
C-reactive protein (CRP) and erythrocyte sedimentation rate (ESR) have been shown to be useful for diagnosis of prosthetic hip and knee infection. Little information is available on CRP and ESR in patients undergoing revision or resection of shoulder arthroplasties or spine implants.
We analyzed preoperative CRP and ESR in 636 subjects who underwent knee (n = 297), hip (n = 221) or shoulder (n = 64) arthroplasty, or spine implant (n = 54) removal. A standardized definition of orthopedic implant-associated infection was applied. Receiver operating curve analysis was used to determine ideal cutoff values for differentiating infected from non-infected cases. ESR was significantly different in subjects with aseptic failure infection of knee (median 11 and 53.5 mm/h, respectively, p = <0.0001) and hip (median 11 and 30 mm/h, respectively, p = <0.0001) arthroplasties and spine implants (median 10 and 48.5 mm/h, respectively, p = 0.0033), but not shoulder arthroplasties (median 10 and 9 mm/h, respectively, p = 0.9883). Optimized ESR cutoffs for knee, hip and shoulder arthroplasties and spine implants were 19, 13, 26, and 45 mm/h, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 89 and 74% for knee, 82 and 60% for hip, and 32 and 93% for shoulder arthroplasties, and 57 and 90% for spine implants. CRP was significantly different in subjects with aseptic failure and infection of knee (median 4 and 51 mg/l, respectively, p<0.0001), hip (median 3 and 18 mg/l, respectively, p<0.0001), and shoulder (median 3 and 10 mg/l, respectively, p = 0.01) arthroplasties, and spine implants (median 3 and 20 mg/l, respectively, p = 0.0011). Optimized CRP cutoffs for knee, hip, and shoulder arthroplasties, and spine implants were 14.5, 10.3, 7, and 4.6 mg/l, respectively. Using these cutoffs, sensitivity and specificity to detect infection were 79 and 88% for knee, 74 and 79% for hip, and 63 and 73% for shoulder arthroplasties, and 79 and 68% for spine implants.
CRP and ESR have poor sensitivity for the diagnosis of shoulder implant infection. A CRP of 4.6 mg/l had a sensitivity of 79 and a specificity of 68% to detect infection of spine implants.
PMCID: PMC2825262  PMID: 20179760

Results 1-4 (4)