For successful TKA, good soft tissue balance is one of the most important factors; however, it is unknown whether the coronal balance immediately after surgery is maintained with time. We hypothesized, if neutral mechanical alignment was achieved at the time of TKA, some degree of lateral ligamentous laxity could be accepted and the laxity would diminish with time. To confirm this hypothesis, we posed two scientific questions: (1) Does the coronal ligament balance measured immediately after TKA change with time? (2) Does the degree of preoperative varus alignment correlate with the lateral or medial ligamentous laxity observed after TKA? We measured coronal lateral or medial ligamentous laxity in 71 knees with varus deformities immediately after surgery and at 3, 6, and 12 months thereafter. The mean mechanical axis was 15.9°varus preoperatively and 0.4°varus postoperatively. The mean medial ligamentous laxity was relatively constant postoperatively from immediately after surgery to 12 months. However, the mean lateral ligamentous laxity was as much as 8.6°immediately after surgery and decreased to 5.1°at 3 months. The lateral ligamentous laxity immediately after surgery correlated with the preoperative varus mechanical axis. Our data show residual lateral ligamentous laxity observed in preoperative varus deformity may be corrected spontaneously after TKA.

IntroductionFor the total knee arthroplasty in valgus deformed knee, superiority of the medial or lateral approach is still controversial. We compared the short-term result of two approach groups.Materials and methodsForty-seven knees in rheumatoid arthritis with valgus deformity from 6° to 24° were randomly divided into two group; medial approach (24 knees) and lateral approach (24 knees). We used Scorpio NRG PS for all knees. Median postoperative periods were 43 months in both groups. We compared the surgical time, and alignment on standing radiograph, range of motion (ROM) pre/postoperatively, and degrees of soft-tissue release procedure, and lateral laxity measured by stress radiograph immediately after operation and at final follow-up.ResultPre/postoperative alignment, surgical time, lateral laxity, and preoperative ROM had no significant in two groups; however, postoperative flexion was superior in lateral approach group 123.8°, 109° in medial approach group. All cases required iliotibial band (ITB) release at Gerdy’s tubercle, 83 % ITB at joint level, 21 % lateral collateral ligament (LCL), 17 % popliteus tendon (PT) in medial approach group, and 88 % ITB at Gerdy’s tubercle, 46 % ITB at joint level, 13 % LCL, 4 % PT in lateral approach group.DiscussionIn the valgus knee, lateral structures are tight. Lateral approach can directly adjust the tight structure, and also less vascular compromise to the patella than medial approach with lateral patellar release. Less invasiveness to the quadriceps muscle in lateral approach could result into better range of motion after the surgery.

Slightly greater lateral laxity was observed after TKA, although equal medial-lateral balance was achieved intra-operatively.

Treatment once extension contracture of the knee has completed is difficult and costly. The most effective treatment might be the prevention of contracture, especially after joint injury. In order to establish an effective method for contracture prevention we first made an extension contracture in rabbit knees, then studied the effect of a sheet made from hyaluronic acid and carboxymethyl cellulose (HA/CMC) for the prevention of knee contracture. One hundred and twenty two mature male Japanese white rabbits were divided into three groups: (1) group B (n=42), where bony holes were made at the medial and lateral epicondyles, (2) group H (n=40), where HA/CMC sheets were placed on the bony holes, and (3) group S (n=40),where only arthrotomy was performed. All surgical procedures were performed on the right knees. All right knees were fixed at 45 degrees using external fixators; this is the maximum extension angle the rabbit is able to tolerate and still walk. At 1, 3, and 6 weeks after surgery, we measured the moment necessary to flex the knee using a special device. We defined the moment as flexion moment (FM). Forty four left knees were also tested as group N, not operated on and serving as the healthy side. In all groups, FM was increased parallel to the increment of flexion angle from 45 degrees to 115 degrees . At many flexion angles, the FM in group B was higher than those of group S at 3 and 6 weeks. The FM in group H was significantly lower than those of group B at 85 degrees and 95 degrees of flexion at 6 weeks after the operation. By macroscopic observation, the area and degree of adhesion were greater in group B than those of group S. In group H, adhesions around the bony hole were less evident than in group B at 6 weeks after the operation. By histological examination, dense granulation tissue was found adjacent to the bony hole in group B at 3 and 6 weeks after the operation. In contrast, in group H the amount of granulation tissue was smaller at 3 and 6 weeks after the operation than those of group B. The usage of HA/CMC sheet should be effective for prevention of contracture occurring after trauma such as treatment for intra-articular fracture.

The bony landmark method provided a more accurate posterior tibial slope than the conventional method. However, there was no difference in coronal alignment compared with the conventional method.