Montgomery Spencer J, Sikes James H, Melancon Drew P, Aparicio Humberto A, Spears Isaac J, Powers Evan H
Orthopaedic Surgery, University of Mississippi Medical Center, Jackson, USA.
Medical School, University of Mississippi Medical Center, Jackson, USA.
Cureus. 2025 Apr 12;17(4):e82148. doi: 10.7759/cureus.82148. eCollection 2025 Apr.
Implants and fixation in revision total knee arthroplasty (rTKA) are based on intramedullary referencing and mechanical axis (MA) restoration. Alternative alignment strategies to primary MA total knee arthroplasty (TKA) are increasing in popularity and often place implants in positions of joint line obliquity. The deviation in implant position could result in significant bony defects when being revised to MA-based revision reconstructions. The purpose of this study was to analyze the medial and lateral, as well as flexion and extension gaps, following a standardized workflow to revise a kinematically aligned total knee arthroplasty (KA TKA) to an MA rTKA.
Seven cadaveric lower extremities that previously underwent caliper-verified KA TKA were converted to MA rTKA utilizing a series of sequential soft tissue releases followed by a tibial osteotomy set perpendicular to the tibial mechanical axis. Gap measurements following each step were recorded using a digital gap-balancing device.
After conversion from KA TKA to MA rTKA, statistically significant increases were observed in the medial extension, medial flexion, lateral extension, and lateral flexion spaces of 1.6 mm (p=0.033), 3. 6mm (p<0.001), 5.6 mm (p<0.001) and 6.9 mm (p<0.001), respectively. Release of the posterior cruciate ligament (PCL) resulted in isolated flexion space opening by 2.4 mm (p=0.002) and 2.3 mm (p=0.022), respectively, for the medial and lateral flexion gaps.
Soft tissue releases seen in rTKA have minimal effect on the medial laxity in extension. In specimens with only mild deviation from neutral alignment and joint line obliquity, the conversion from caliper-verified KA TKA to MA rTKA still resulted in large increases in the lateral-sided gaps, especially in the flexion space. This may create issues with current implant offerings, and surgeons should anticipate substantial augmentation or joint line adjustments when revising implants that were placed with intentional joint line obliquity.
翻修全膝关节置换术（rTKA）中的植入物和固定基于髓内参考和机械轴（MA）恢复。与初次MA全膝关节置换术（TKA）不同的对线策略越来越受欢迎，并且常常将植入物放置在关节线倾斜的位置。当翻修为基于MA的翻修重建时，植入物位置的偏差可能导致明显的骨缺损。本研究的目的是分析按照标准化工作流程将运动学对线全膝关节置换术（KA TKA）翻修为MA rTKA后的内侧和外侧以及屈伸间隙。
七具先前接受卡尺验证的KA TKA的尸体下肢，通过一系列连续的软组织松解，然后进行垂直于胫骨机械轴的胫骨截骨术，转换为MA rTKA。使用数字间隙平衡装置记录每个步骤后的间隙测量值。
从KA TKA转换为MA rTKA后，内侧伸展、内侧屈曲、外侧伸展和外侧屈曲间隙分别有统计学意义的增加，增加量分别为1.6mm（p = 0.033）、3.6mm（p < 0.001）、5.6mm（p < 0.001）和6.9mm（p < 0.001）。后交叉韧带（PCL）的松解分别导致内侧和外侧屈曲间隙的孤立屈曲间隙开口增加2.4mm（p = 0.002）和2.3mm（p = 0.022）。
rTKA中的软组织松解对伸展时的内侧松弛影响最小。在仅与中立对线和关节线倾斜有轻微偏差的标本中，从卡尺验证的KA TKA转换为MA rTKA仍然导致外侧间隙大幅增加，尤其是在屈曲间隙。这可能给当前的植入物带来问题，并且外科医生在翻修有意设置关节线倾斜放置的植入物时应预期需要大量的骨增量或关节线调整。
