Hartford J M, Banit D, Hall K, Kaufer H
Division of Orthopaedic Surgery, University of Kentucky, Chandler Medical Center, Lexington 40536, USA.
J Bone Joint Surg Am. 2001 Feb;83(2):229-34. doi: 10.2106/00004623-200102000-00010.
Meniscal bearing total knee replacements were developed to decrease the contact stresses on polyethylene and to reduce polyethylene wear. The kinematics of meniscal bearing knee replacements is poorly understood. The present study was designed to evaluate, with radiographic analyses, the motion of the meniscal bearings and the femoral rollback of the Low Contact Stress meniscal bearing knee replacement during knee flexion.
Eighty-one Low Contact Stress meniscal bearing total knee replacements in seventy-six male patients were assessed on fluoroscopically centered lateral radiographs made with the knee in full extension and in full flexion at an average of six years (range, twenty-four to 147 months) after the operation. The distance and direction of motion of the meniscal bearings and the center contact position of the femoral condyles were measured. Knee evaluations were performed with use of the Knee Society rating system.
The average range of motion of the knees, measured on lateral radiographs, was 90 degrees (range, 45 degrees to 136 degrees). As they moved from terminal extension to terminal flexion, thirty-nine knees (48%) exhibited anterior motion of both bearings and sixteen (20%) demonstrated posterior motion of both bearings. Ten knees (12%) had reciprocal motion of the two bearings (one bearing moving anteriorly and one bearing moving posteriorly) with flexion, nine knees (11%) had motion of only one bearing, and seven knees (9%) had no motion of either bearing. When moving from full extension to full flexion, eighteen knees (22%) demonstrated femoral rollback, six knees (7%) showed no change in the position of femoral contact, and fifty-seven knees (70%) exhibited anterior sliding of the femoral condyles. Flexion of the knees demonstrating femoral rollback averaged 104 degrees (range, 76 degrees to 128 degrees), and flexion of the knees demonstrating anterior sliding averaged 94 degrees (range, 45 degrees to 125 degrees). The difference was significant (p = 0.03). According to the Knee Society rating system, the average clinical score for the entire group was 76 points (range, 27 to 100 points) and the average functional score for the entire group was 72 points (range, 30 to 100 points). The average clinical score was 79 points (range, 27 to 98 points) for the knees that exhibited anterior sliding of the femoral condyles and 87 points (range, 52 to 100 points) for those exhibiting femoral rollback (p = 0.09). The average functional scores were 64 points (range, 30 to 100 points) and 72 points (range, 45 to 100 points), respectively (p = 0.15).
Radiographic analysis of meniscal bearing total knee replacements demonstrated an average anterior motion of both the medial and the lateral meniscal bearing of 4.7 mm (range, 1 to 14 mm) in thirty-nine knees (48%) as they moved from terminal extension to terminal flexion. Sixty-three knees (78%) demonstrated no femoral rollback as they were flexed. Knees with anterior sliding of the condyles had a significantly smaller average range of flexion (p = 0.03) and a lower average Knee Society score than did knees demonstrating femoral rollback. We believe that lack of rollback indicates a functional insufficiency of the posterior cruciate ligament.
半月板承载型全膝关节置换术旨在降低聚乙烯上的接触应力并减少聚乙烯磨损。人们对半月板承载型膝关节置换术的运动学了解甚少。本研究旨在通过影像学分析评估半月板承载部件的运动以及低接触应力半月板承载型膝关节置换术在膝关节屈曲过程中股骨的后滚情况。
对76名男性患者的81例低接触应力半月板承载型全膝关节置换术进行评估，在术后平均6年（范围为24至147个月）时，拍摄膝关节完全伸直和完全屈曲时的透视中心侧位X线片。测量半月板承载部件的运动距离和方向以及股骨髁的中心接触位置。使用膝关节协会评分系统进行膝关节评估。
通过侧位X线片测量，膝关节的平均活动范围为90度（范围为45度至136度）。从终末伸直位到终末屈曲位时，39个膝关节（48%）的两个承载部件均向前运动，16个膝关节（20%）的两个承载部件均向后运动。10个膝关节（12%）在屈曲时两个承载部件呈相反运动（一个向前一个向后），9个膝关节（11%）只有一个承载部件运动，7个膝关节（9%）两个承载部件均无运动。从完全伸直位到完全屈曲位时，18个膝关节（22%）出现股骨后滚，6个膝关节（7%）股骨接触位置无变化，57个膝关节（70%）股骨髁向前滑动。出现股骨后滚的膝关节屈曲平均为104度（范围为76度至128度），出现向前滑动的膝关节屈曲平均为94度（范围为45度至125度）。差异具有统计学意义（p = 0.03）。根据膝关节协会评分系统，整个组的平均临床评分为76分（范围为27至100分），整个组的平均功能评分为72分（范围为30至100分）。股骨髁向前滑动的膝关节平均临床评分为79分（范围为27至98分），出现股骨后滚的膝关节平均临床评分为87分（范围为52至100分）（p = 0.09）。平均功能评分分别为64分（范围为30至100分）和72分（范围为45至100分）（p = 0.15）。
对半月板承载型全膝关节置换术的影像学分析表明，39个膝关节（占48%）从终末伸直位到终末屈曲位时，内侧和外侧半月板承载部件平均向前运动4.7毫米（范围为1至14毫米）。63个膝关节（占78%）在屈曲时未出现股骨后滚。髁向前滑动的膝关节平均屈曲范围明显更小（p = 0.03），且膝关节协会平均评分低于出现股骨后滚的膝关节。我们认为缺乏后滚表明后交叉韧带功能不全。
