Kinamed (United States)

Replicating native knee kinematics remains the ultimate goal of total knee arthroplasty (TKA). Technology, such as robotics, provides robust intraoperative data; however, no evidence-based targets currently exist for improved clinical outcomes. Furthermore, some surgeons target a rectangular flexion space in TKA unlike the native knee. This study evaluated the effect of in vivo flexion gap asymmetry on patient-reported outcome measures (PROMs) in contemporary TKA. In vivo tibiofemoral joint space dimensions were measured during 129 TKAs using a calibrated tension device before and after complete posterior cruciate ligament resection. PROMs were compared based on the final dimensions and the change in flexion gap dimensions at 90° of flexion: (1) equal laxity, (2) lateral laxity, and (3) medial laxity. Groups did not differ by demographics ( P ≥ 0.347), clinical follow-up ( P = 0.134), tibiofemoral alignment ( P = 0.498), or preoperative PROMs ( P ≥ 0.093). Mean follow-up for the cohort was 1.5 years (range, 1-3). Pain with climbing stairs, pain while standing upright, and knees "always feeling normal" scores were superior for patients with equal or lateral laxity compared with medial laxity ( P ≤ 0.064). Pain with level walking, University of California Los Angeles activity level, KOOS JR, and satisfaction scores also tended to be superior for patients with equal or lateral laxity, although it lacked statistical significance ( P ≥ 0.111). Results of this study suggest that patients with either an equally tensioned rectangular flexion space or with later-flexion lateral laxity after posterior cruciate ligament resection may achieve superior PROMs. Findings support the clinical benefit of facilitating posterolateral femoral roll back in flexion, which mimics native knee kinematics and further helps define targets for advanced technology.

The treatment of isolated patellofemoral arthritis is controversial. Several surgical procedures have been used to treat the severely degenerated patellofemoral joint, with varying degrees of success. The purpose of this study was to determine the clinical results of a custom patellofemoral arthroplasty for the treatment of isolated patellofemoral degenerative arthritis of the knee. From 1995 through 2002, twenty-five patellofemoral replacements, three of which were bilateral, were performed in twenty-two patients for the treatment of isolated patellofemoral arthritis of the knee. According to the Ahl-back radiographic evaluation scale, the mean preoperative score for the severity of the arthritis was 4.65 points in the patellofemoral compartment and 0.5 point in both the medial and the lateral compartment. The patients included sixteen women (two of whom had a bilateral replacement) and six men (one of whom had a bilateral replacement) with a mean age of forty-five years at the time of the index arthroplasty. Seventeen patients (nineteen knees) had had a prior procedure on the knee. The mean preoperative Knee Society functional score was 49 points, and the mean preoperative Knee Society objective score was 52 points. At a mean of seventy-three months (range, thirty-two to 119 months) postoperatively, all twenty-five implants were in place and functioning well. There were eighteen excellent and seven good results. The mean Knee Society functional score was 89 points, and the mean Knee Society objective score was 91 points. No patient had required additional surgery or had component loosening. On the basis of our relatively short-term follow-up study, custom patellofemoral arthroplasty appears to be a safe and effective treatment for isolated patellofemoral arthritis of the knee. We believe that the results presented in this paper justify the additional cost associated with the custom device. Therapeutic Level IV. See Instructions to Authors for a complete description of levels of evidence.