In Jun Koh1, Charles C Lin2, Nilay A Patel3, Christen E Chalmers2, Mauro Maniglio4, Sung Bin Han5, Michelle H McGarry6, Thay Q Lee6. 1. Joint Replacement Center, Eunpyeong St. Mary's Hospital, 03312 Seoul, Republic of Korea; Department of Orthopaedic Surgery, College of Medicine, The Catholic University of Korea, 06591 Seoul, Republic of Korea. Electronic address: oskoh@catholic.ac.kr. 2. University of California, Irvine, School of Medicine, 92697 Irvine, CA, United States. 3. Department of Orthopaedic Surgery, University of California, Irvine, UCI Medical Center, route 81, 101 City Drive South, 92868 Orange, CA, United States. 4. Department of Orthopaedics and Traumatology; Inselspital Bern, University Hospital, Bern, Switzerland. 5. Joint Replacement Center, Eunpyeong St. Mary's Hospital, 03312 Seoul, Republic of Korea. 6. Congress Medical Foundation, 800 South Raymond Pasadena, 91105 CA, United States.
Abstract
BACKGROUND: A growing body of evidence supports that kinematically aligned (KA) total knee arthroplasty (TKA) provides superior clinical outcomes and satisfaction than mechanically aligned (MA) TKA. In theory, KA TKA would restore knee kinematics closer to the native condition than MA TKA, but the current biomechanical evidence is lacking. HYPOTHESIS: KA TKA would restore knee biomechanics to the native condition better than MA TKA. METHODS: Seven pairs of cadavers were tested. For each pair, one knee was randomly assigned to KA TKA and the other to MA TKA. During KA TKA, the sizes of femur and tibia resections were equivalent to implant thickness to align with the patient-specific joint line. MA TKA was performed using conventional measured resection techniques. All specimens were mounted on a customized knee-testing system and digitized. Knee motions measured during flexion included rollback, axial tibiofemoral rotation, and laxities, specifically varus-valgus laxity, anterior-posterior translation, and internal-external rotation. RESULTS: The pattern of knee motion following KA TKA was similar to the native knee. However, following MA TKA, both medial and lateral rollback and tibiofemoral axial rotation were decreased relative to those of the native knee. Valgus laxity was restored only after KA TKA, whereas varus laxity was restored only after MA TKA. Anterior translation was increased regardless of the alignment strategy. In addition, rotational laxities were restored after KA TKA, but external rotation laxity increased after MA TKA. CONCLUSION: KA TKA restores femoral rollback and laxity to the native condition better than MA TKA. KA TKA may enhance functional performance and provide a more normal knee sensation. LEVEL OF EVIDENCE: II, Controlled laboratory study.
BACKGROUND: A growing body of evidence supports that kinematically aligned (KA) total knee arthroplasty (TKA) provides superior clinical outcomes and satisfaction than mechanically aligned (MA) TKA. In theory, KA TKA would restore knee kinematics closer to the native condition than MA TKA, but the current biomechanical evidence is lacking. HYPOTHESIS: KA TKA would restore knee biomechanics to the native condition better than MA TKA. METHODS: Seven pairs of cadavers were tested. For each pair, one knee was randomly assigned to KA TKA and the other to MA TKA. During KA TKA, the sizes of femur and tibia resections were equivalent to implant thickness to align with the patient-specific joint line. MA TKA was performed using conventional measured resection techniques. All specimens were mounted on a customized knee-testing system and digitized. Knee motions measured during flexion included rollback, axial tibiofemoral rotation, and laxities, specifically varus-valgus laxity, anterior-posterior translation, and internal-external rotation. RESULTS: The pattern of knee motion following KA TKA was similar to the native knee. However, following MA TKA, both medial and lateral rollback and tibiofemoral axial rotation were decreased relative to those of the native knee. Valgus laxity was restored only after KA TKA, whereas varus laxity was restored only after MA TKA. Anterior translation was increased regardless of the alignment strategy. In addition, rotational laxities were restored after KA TKA, but external rotation laxity increased after MA TKA. CONCLUSION: KA TKA restores femoral rollback and laxity to the native condition better than MA TKA. KA TKA may enhance functional performance and provide a more normal knee sensation. LEVEL OF EVIDENCE: II, Controlled laboratory study.
Authors: Shady S Elmasry; Peter K Sculco; Cynthia A Kahlenberg; David J Mayman; Michael B Cross; Andrew D Pearle; Timothy M Wright; Geoffrey H Westrich; Carl W Imhauser Journal: Clin Orthop Relat Res Date: 2022-03-24 Impact factor: 4.755