Multiple Hip Intra-Articular Steroid Injections Increase Risk of Periprosthetic Joint Infection Compared With Single Injections.

BACKGROUND: Patients with hip osteoarthritis often temporize their symptoms with multiple intra-articular steroid hip injections (IASHIs) before undergoing total hip arthroplasty (THA). Although there is recent evidence to suggest that IASHI can lead to an increased risk of future periprosthetic joint infection (PJI), the potential increase in risk of PJI after multiple IASHIs compared with single IASHI remains largely unknown. The aim of the study was to evaluate whether multiple IASHIs are associated with increased risk of PJI compared with single IASHI in THA patients. METHODS: We evaluated 2 cohorts of patients consisting of 106 patients who received 2 or more IASHI in the year before THA and a matched group of 350 patients who received one IASHI in the 12 months before THA. RESULTS: The single and multiply-injected patient cohorts had an infection rate of 2.0% and 6.6% (7/350 and 7/106), respectively (P = .04, odds ratio 3.30) and average follow-up of 28.9 and 24.2 months. The 2 cohorts did not differ with regard to age, gender, American Society of Anesthesiologist score, presence of diabetes mellitus, or body mass index. CONCLUSION: In comparison with patients with single IASHI, multiple IASHIs are associated with an increased risk of PJI significantly higher than the elevated risk reported with single injection before THA. The present study findings would be clinically useful in counseling patients who are considering temporizing their symptoms with multiple IASHIs before undergoing THA.

Medial Femoral Condyle Cartilage Defect Biomechanics: Effect of Obesity, Defect Size, and Cartilage Thickness.

BACKGROUND: Medial femoral condyle (MFC) chondral defects cause knee pain. Clinical studies have shown worse functional outcomes and cartilage defect fill rates after microfracture in obese patients (BMI ≥30) and for defects with size ≥2 cm(2). PURPOSE: To determine the effect of obesity, defect size, and cartilage thickness on the force sustained at the base of full-thickness MFC cartilage defects during weightbearing. STUDY DESIGN: Controlled laboratory study. METHODS: Eight human cadaveric knees were loaded in 15° of flexion. A sensor measured force across the medial compartment. The area at the base of the defect protected from load, termed the "area of containment," was quantified, and loads simulating weightbearing for BMIs of 20, 30, and 40 were applied. A full-thickness cartilage defect was created on the MFC. Cycles of loads were applied for defect sizes with diameters of 6, 8, 10, 12, 14, 16, 18, and 20 mm. A second sensor recorded force at the base of the defect for defects with diameters of 14, 16, 18, and 20 mm. RESULTS: Loads simulating BMI ≥30 led to a decrease in the area of containment for all defects ≥14 mm in diameter (P ≤ .038). Base of defect force increased for defects ≥16 mm in diameter (area, ≥2 cm(2)) between loaded and unloaded states (P ≤ .042) and for loads simulating BMI ≥30 (P ≤ .045). Cartilage rim thickness <2 mm showed higher base of defect force than did thickness ≥2 mm, for all BMI groups (P ≤ .025). CONCLUSION: Increased force at the base of MFC cartilage defects was observed for weightbearing loads simulating BMI ≥30, for defect size ≥2 cm(2), and for rim thickness <2 mm. This may lead to a biomechanically unfavorable environment after microfracture in these patient subsets. CLINICAL RELEVANCE: These biomechanical findings corroborate clinical studies that have noted worse outcomes after microfracture in patients with BMI ≥30 and cartilage defects of size ≥2 cm(2). Further clinical studies are needed to compare microfracture with other cartilage restoration procedures in these patient subsets.