Joint line elevation is not associated with mid-flexion laxity in patients with varus osteoarthritis after total knee ar
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KNEE
Joint line elevation is not associated with mid‑flexion laxity in patients with varus osteoarthritis after total knee arthroplasty Yukihide Minoda1 · Ryo Sugama1 · Yoichi Ohta1 · Hideki Ueyama1 · Susumu Takemura1 · Hiroaki Nakamura1 Received: 11 July 2019 / Accepted: 11 December 2019 © European Society of Sports Traumatology, Knee Surgery, Arthroscopy (ESSKA) 2019
Abstract Purpose Previous cadaver studies showed that the additional bone cuts in the distal and posterior femur and joint line elevation resulted in laxity at mid-flexion after total knee arthroplasty (TKA). However, these results are not always applicable to TKA candidates because the related studies used cadaver knees with no osteoarthritis. It was hypothesized that the joint line elevation results in mid-flexion laxity after TKA in patients with knee osteoarthritis. The purpose of this study was to analyze the relationship between joint line elevation and mid-flexion laxity in patients with knee osteoarthritis. Methods 30 knees with varus osteoarthritis undergoing TKA were evaluated. Two femoral trial component models were prepared: (1) normal model with a thickness of the distal and posterior femoral components of 9 mm, and (2) 2-mm joint line elevation model with a thickness of the distal and posterior femoral components of 9 − 2 = 7 mm. This 2-mm joint line elevation model simulated an additional bone cut in the distal and posterior femur, and joint line elevation, without an additional bone cut. The femoral trial component models were set before implantation and measured the joint gap kinematics using a tensor device through the full knee range of motion. Results The differences in joint gap change from 30° to 90° were not statistically significant between the two models. However, the joint line elevation model decreased the joint gap laxity at 120° (p = 0.02) and at 145° (p = 0.01). Conclusions This study showed that a 2-mm joint line elevation was not associated with mid-flexion laxity in patients with varus osteoarthritis in the knee. The results of this study differed from the results in previous cadaver studies. Level of evidence Therapeutic study, level II, prospective comparative study. Keywords Total knee arthroplasty · Joint line · Mid-flexion laxity
Introduction Soft tissue balancing of the knee is important for the success of total knee arthroplasty (TKA) [5, 11], and instability is one of the most common causes of early and late failure of TKA [8]. Soft tissue balance at 0° and 90° is assessed intraoperatively; however, soft tissue balance in the mid-flexion range is not well-considered intraoperatively. Stability in the mid-flexion range was first reported in 1990 with a laboratory investigation [10]. During most activities of daily living, especially ascending and descending stairs or walking on slopes, the knee is loaded near full extension as well as in * Yukihide Minoda [email protected]‑cu.ac.jp 1
Department of Orthopaedic Surgery, Osaka City University Graduate School of Medicine, 1‑4‑3 Asahimachi, Abeno‑k
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