ObjectiveTo explore the feasibility and short-term effectiveness of lateral unicompartmental knee arthroplasty (LUKA) through a lateral parapatellar approach for lateral compartmental osteoarthritis (LCOA). MethodsBetween November 2010 and August 2012, 15 consecutive patients (15 knees) with LCOA were treated with LUKA. There were 7 men and 8 women with a mean age of 67.3 years (range, 51-82 years). The mean duration of disease was 5.4 years (range, 3-15 years). The left knee was involved in 6 cases and the right knee in 9 cases. According to Ahlback rating, there were 2 cases (2 knees) of grade I, 8 cases (8 knees) of grade Ⅱ, and 5 cases (5 knees) of grade Ⅲ. The incision length, operation time, blood loss, drainage, and complication were recorded. The pre- and post-operative knee function was evaluated by Hospital for Special Surgery (HSS) score system. The pre- and post-operative range of motion (ROM) and alignment of the lower limbs (hip-knee-ankle angle) were measured and compared. ResultsACL rupture or medial compartmental osteoarthritis occurred in 2 patients (2 knees) who changed to total knee arthroplasty (TKA); 1 case (1 knee) failed to follow up. The other 12 cases (12 knees) were followed up 32.5 months on average (range, 26- 45 months). The mean length of incision was 6.9 cm (range, 6-8 cm); the mean operation time was 115.8 minutes (range,90-155 minutes); the mean blood loss volume during operation was 152.2 mL (range, 105-250 mL); and mean drainage was 145.6 mL (range, 50-300 mL). At last follow-up, the average HSS score was significantly improved from 73.4±4.6 preoperatively to 94.6±2.1 postoperatively (t=14.240, P=0.000). The results were excellent in 9 cases, good in 2 cases, and fair in 1 case, with an excellent and good rate of 91.7%. The hip-knee-ankle angle was significantly decreased from valgus angle of (10.08±1.38)° preoperatively to valgus angle of (5.17±0.94)° postoperatively (t=14.626, P=0.000). Postoperative ROM was significantly improved to (123.75±4.09)° from (108.67±5.10)° preoperatively (t=8.998, P=0.000). Two patients developed superficial skin infection, which was managed with anti-inflammatory therapy and dressing. No patient had complication of deep vein thrombosis, prosthesis dislocation and loosing, or development of medial osteoarthritis. ConclusionLUKA through a lateral approach has the advantages of rapid recovery of joint function, less complication, and small trauma in the treatment of LCOA. Correct patient selection and further mid- and long-term studies, however, are essential.
ObjectiveTo investigate the biomechanical characteristics of the proximal tibia (including cortical bone, cancellous bone, and bone cement) after lateral unicompartmental knee arthroplasty (L-UKA) under conditions of normal bone mass, osteopenia, and osteoporosis through finite element analysis of the tibial plateau, and to evaluate the impact of osteoporosis on the risk of postoperative tibial fracture from a biomechanical perspective, focusing on stress, strain, and deformation distribution patterns. MethodsBased on CT data of the tibia from a healthy adult male volunteer, a three-dimensional finite element model of L-UKA was established, including the femoral component, tibial component, ultra-high molecular weight polyethylene insert, bone cement, medial tibial cartilage, and tibia (comprising cortical and cancellous bone). Three groups of bone density parameters were defined: normal bone mass (T-score ≥?1.0SD), osteopenia (T-score –2.5SD-–1.0SD), and osteoporosis (T-score ≤–2.5SD). Different bone conditions were simulated by adjusting the elastic modulus of cortical and cancellous bone. Boundary conditions included complete constraint of the distal tibia, application of a 600 N vertical load on the femoral component, and a 400 N vertical load on the medial tibial cartilage to simulate single-leg stance during slow walking. The maximum stress, maximum strain, and maximum deformation of key structures were measured. Results As bone mass decreased, the biomechanical responses of bone and bone cement changed significantly. Specifically, the maximum stress, maximum strain, and maximum deformation of cortical bone and the bone cement layer increased markedly. For cancellous bone, the maximum stress decreased, while the maximum strain and maximum deformation increased. The maximum stress of the insert were similar across the three groups, with minimal variation (<1%); the peak stress was located at the contact area between the insert and the femoral component. ConclusionThe biomechanical risk of tibial fracture after L-UKA significantly increases in patients with osteoporosis, particularly for periprosthetic stress or fragility fractures.