Although various platelet-rich plasma (PRP) kits are commercially available, the efficacy of these kits for knee osteoarthritis (KOA) has not been fully investigated. This study aimed to investigate the short-term results of leukocyte-poor PRP (LP-PRP) and the factors that contribute to its efficacy. We retrospectively reviewed 124 patients with KOA who were treated with LP-PRP. White blood cell (WBC) and platelet counts in the whole blood and the LP-PRP were measured. KOA severity was assessed using radiography. Clinical evaluation was performed both prior to injection and after an average of 3.3 weeks after the injection using the Japanese Knee Osteoarthritis Measure (JKOM). Responders were defined based on the JKOM. The contributing factors for responders were examined using a multivariate logistic analysis. The responder rate was 58.1% and the contributing factors for responders were a higher visual analog scale score before injection, WBC count in whole blood, and platelet concentration ratio of LP-PRP. The LP-PRP improved the clinical scores in the short term. Certain patient characteristics before injection and the concentration ratio of LP-PRP may be predictors of its efficacy; these may provide clues for elucidating which components of LP-PRP act on KOA pathologies.

Background and Objectives: Although hybrid closed-wedge high tibial osteotomy (HTO) is an effective procedure for varus knee osteoarthritis, delayed bone union is a frequent occurrence. The rate of bone union and its associated factors remain unclear. This study aimed to investigate the detailed process of bone union in hybrid closed-wedge HTO using computed tomography (CT) and to examine factors associated with delayed bone union. Materials and Methods: We retrospectively reviewed 53 consecutive patients who underwent hybrid closed-wedge HTO. Cases with no bone union at any of five sites (anterior flange, posterior, lateral, hinge, and medial) on coronal and sagittal computed tomography at 3 months postoperatively were defined as delayed bone union. Regression analysis was performed with delayed bone union as the dependent variable and sex, age, height, body weight, body mass index, correction distance, smoking, and diabetes mellitus as independent variables. Results: Among 50 analyzed knees (mean age, 61.4 ± 7.8 years), 17 (34.0%) had delayed bone union at 3 months postoperatively and one knee had screw breakage. Sex was the only significant factor associated with delayed bone union (male: β = 2.1, p < 0.004). Conclusions: Delayed bone union (absence at 3 months after hybrid closed-wedge high tibial osteotomy) occurred in 34% of patients, and male sex was associated with delayed bone union.