The influence of soft tissue balance in mobile-bearing posterior-stabilized (PS) total knee arthroplasty (TKA) on the patellofemoral (PF) joint was investigated in thirty varus-type osteoarthritis patients. Intraoperative soft tissue balance including joint component gap and varus/valgus ligament balance and the medial/lateral patellar pressure were measured throughout the range of motion after the femoral component placement and the PF joint repair. The lateral patellar pressure, which was significantly higher than the medial side in the flexion arc, showed inverse correlation with the lateral laxity at 60° and 90° of flexion. The lateral patellar pressure at 120° and 135° of flexion also inversely correlated with the postoperative flexion angle. Surgeons should take medial and lateral laxity into account when considering PF joint kinematics influencing postoperative flexion angle in PS TKA.
Many factors can influence postoperative knee flexion angle after total knee arthroplasty (TKA), and range of flexion is one of the most important clinical outcomes. Although many studies have reported that postoperative knee flexion is influenced by preoperative clinical conditions, the factors which affect postoperative knee flexion angle have not been fully elucidated. As appropriate soft-tissue balancing as well as accurate bony cuts and implantation has traditionally been the focus of TKA success, in this study, we tried to investigate the influence of intraoperative soft-tissue balance on postoperative knee flexion angle after cruciate-retaining (CR) TKA using a navigation system and offset-type tensor. We retrospectively analyzed 55 patients (43 women, 12 men) with osteoarthritis who underwent TKA using the same mobile-bearing CR-type implant (e.motion; B. Braun Aesculap, Germany). The mean age at the time of surgery was 74.2 (SD 7.3) years. The exclusion criteria for this study included valgus deformity, severe bony defect requiring bone graft or augmentation, revision TKA, active knee joint infection, and bilateral TKA. Intraoperative soft-tissue balance parameters such as varus ligament balance and joint component gap were measured in the navigation system (Orthopilot 4.2; B. Braun Aesculap) while applying 40-lb joint distraction force at 0°, 10°, 30°, 60°, 90°, and 120° of knee flexion using an offset-type tensor with the patella reduced. Varus ligament balance was defined as the angle (degree, positive value in varus imbalance) between the seesaw and platform plates of the tensor that was obtained from the values displayed by the navigation system. To determine clinical outcome, we measured knee flexion angle using a goniometer with the patient in the supine position before and 2 years after surgery. Correlations between the soft-tissue parameters and postoperative knee flexion angle were analyzed using simple linear regression models. Pre- and postoperative knee flexion angle were also analyzed in the same manner.Introduction / Purpose
Methods
Surgeons sometimes encounter moderate or severe varus deformed osteoarthritic cases in which medial substantial release including semimembranosus is compelled to appropriately balance soft tissues in total knee arthroplasty (TKA). However, medial stability after TKA is important for acquisition of proper knee kinematics to lead to medial pivot motion during knee flexion. The purpose of the present study is to prove the hypothesis that step by step medial release, especially semimembranosus release, reduces medial stability in cruciate-retaining (CR) total knee arthroplasty (TKA). Twenty CR TKAs were performed in patients with moderate varus-type osteoarthritis (10° < varus deformity <20°) using the tibia first technique guided by a navigation system (Orthopilot). During the process of medial release, knee kinematics including tibial internal rotation and anterior translation during knee flexion were assessed using the navigation system at 3 points; (1) after anterior cruciate ligament resection (pre-release), (2) medial tibial and femoral osteophyte removal and release of minimum deep layer of medial collateral ligament (minimum release) and (3) release of semimembranosus (semimembranosus release). In addition, the kinematics after all prostheses implantation (semimembranosus release group) were assessed and compared with those assessed in another 20 patients in which only minimum release was performed (minimum release group).Purpose
Methods
The tibia first technique in unicompartmental knee arthroplasty (UKA) may have the advantage that surgeons can obtain a balanced flexion-extension gap. However, changes of the soft tissue tension during UKA has not been elucidated yet. The purpose of this study was to examine the correlation between the soft tissue tension before the femoral osteotomy and after the femoral component in place using the tensor in UKA. Thirty UKAs for isolated medial compartmental osteoarthritis or idiopathic osteonecrosis were assessed. The mean age was 71.8±8.5 years old (range: 58–85), and the average coronal plane femorotibial angle (FTA) was 181.2±3.2 degree preoperatively. All the patients received a conventional medial Zimmer Unicompartmental High Flex Knee System (Zimmer Inc, Warsaw, Ind). The actual values of the proximal and posterior femoral osteotomy were calculated by adding the thickness of the bone saw blades to the thickness of the bony cut. Using a UKA tensor which designed to facilitate intra-operative soft tissue tension throughout the range of motion (ROM), the original gap before the femoral osteotomy, the component gap after the femoral osteotomy, and component placement were assessed under 20 lb distraction forces. (Figure 1)Purpose
Methods
Patients planning to undergo total knee arthroplasty (TKA), especially in Asian and Middle Eastern countries, usually expect to be able to perform activities requiring knee flexion such as sitting cross-legged or kneeling with ease after the surgery. Postoperative range of motion (ROM) can be affected by multiple factors such as the patient's gender, age, preoperative ROM, diagnosis, the surgeon's technique, the pre- and post-operative rehabilitation program, and the design of the prosthesis. Among these, the choice of the prosthesis depends on the surgeon's preference. As a result, several trials and studies have been conducted to improve postoperative ROM by modifying prosthesis design. The present study aimed to examine the results of TKA with the NexGen LPS-Flex system (Zimmer, Warsaw, Indiana), which is one of several high-flexion total knee prostheses that were designed to achieve a wide ROM for osteoarthritis in the valgus knee. A total of 27 primary TKAs in 26 osteoarthritis patients with valgus knee deformities (femorotibial angle (FTA) ≤ 170°) were performed using the NexGen LPS-Flex fixed prosthesis between July 2003 and December 2011. The patients included 2 men (7.7%, 2 knees) and 24 women (92.3%, 25 knees) with a mean age of 72.6 years (range, 59 to 83 years) at the time of the surgery. The mean duration of follow-up after surgery was 50.1 months (range, 24 to 126 months). Knee Society Knee Score (KSKS), Knee Society Function Score (KSFS), maximum flexion angle, maximum extension angle, and radiological femorotibial angle (FTA) were evaluated pre- and post-operatively. The mean preoperative KSKS and KSFS were 42.6 points (SD 7.5) and 41.1 points (SD 8.6), respectively, which improved after surgery to 82.2 points (SD 8.2) and 80.9 points (SD 7.6), respectively (P < 0.01). The maximum flexion angle improved from 109.1° (SD 23.1) to 117.3° (SD 12.4) postoperatively, but it did not reach statistical significance (P = 0.097). The preoperative maximum extension angle improved from −9.7° (SD 10.8) to −3.6° (SD 4.9) postoperatively (p < 0.05). The mean radiological FTA was 166.4° (SD 4.2; range: 155° − 170°) preoperatively and 172.4° (SD 2.7; range: 168° − 178°) at the final follow-up, and the difference was statistically significant (P < 0.01). None of the patients had undergone revision surgery by the final follow-up. As a conclusion, the results of the present study showed that the use of NexGen LPS-Flex implant in TKA for knee osteoarthritis with valgus deformity produced a satisfactory improvement in the clinical and radiological outcomes. Further studies on the outcomes of other prosthesis are needed to determine whether the NexGen LPS-Flex implant is advantageous for osteoarthritis patients with valgus knees who undergo TKA, and further large-scale studies with longer term follow-up are necessary to verify our results.
