RELATIONSHIP OF CORRECTABLE VARUS DEFORMITY WITH FEMUR EXTERNAL ROTATION IN PATIENTS UNDERGOING TOTAL KNEE ARTHROPLASTY USING COMPUTER ASSISTED SURGERY AND COMPARISON BETWEEN GAP MANAGEMENT AND MEASURED RESECTION TECHNIQUES.

Presenting Author - SANDEEP KUMAR REDDY
Total knee arthroplasty is a successful operation for relieving the pain of end- stage arthritis but there is a reported dissatisfaction rate of 10-20% in various studies. One of the reasons for persistent pain and early failure is rotational malalignment of the femoral component.Computer assisted surgery (CAS) can help in accurately measuring the femoral external rotation and making the appropriate distal femur resection. The objective of this study was to do a comparative analysis of the relationship between correctable varus deformity in varus osteoarthritic knees with the amount of femoral external rotation in patients undergoing total knee arthroplasty by CAS and analyze the differences in this relationship between gap management and measured resection techniques. Our study included 117 patients with 57 patients in group1 (gapmanagement technique) and 60 patients in group 2 (measured resection technique). All patients in both the groups underwent primary, cemented, cruciate retaining total knee arthroplasty (Aesculap Columbus) using CAS (B Braun Orthopilot 5.1) with sub- vastus approach by a single surgeon.The amount of varus in extension, varus in flexion, correctable varus after soft tissue release and femur external rotation were measured. TKA was performed by tibia first gapbalancing technique in group 1 and by femur first technique in group 2. In group 1 the mean preoperative varus in extension was 7.73 which was correctable to a mean of 2.19 . The mean external rotation was 3.61.There was a positive correlation between correctable varus and external rotation (r=0.180) which was statistically not significant (p=0.181).In group 2 the mean pre-operative varus in extension was 8.59 which was correctable to a mean of 2.87. The mean external rotation was 3.60.There was a positive correlation between correctable varus and external rotation(r=0.133) which was statistically not significant (p=0.311).The comparison of correctable varus showed no statistically significant difference between the two groups (p=0.245). The comparison of external rotation showed no statistically significant difference between the two groups (p=0.968). Our results show a positive correlation between the amount of correctable varus and femur external rotation which is variable in different knees and hence a different resection angle should be employed in each knee based on the anatomy. CAS can consistently improve the accuracy of component alignment irrespective of the type of technique.