To analyze formation of the varus angle of the knee due to osteoarthritis and to explore techniques of the soft tissue balance in the total knee arthroplasty(TKA).
One hundred patients with 145 varus knees (18 males, 25 varus knees; 82 females, 120 varus knees) underwent TKA from January 1999 to December 2003. Their ages averaged 62.4 years (range, 45-80 years), and their HSS(hospital of special surgery)scores were 38.0 +/- 3.2 points. Before operation,all the patients were measured in the alignment of the lower extremity, accurate bone-cutting was performed, and their static alignment was achieved. Then, the soft tissue release was made. The release performance consisted of 3 steps: release before the bone-cutting, release during the bone-cutting, and release after the bone-cutting. Release of the medial ligament and capsule, elimination of the osteophytes, and release of the lateral patellar retinaculum were more important.
The varus angles in these patients were 9.2 +/- 3.1 degrees before operation. Among them, the varus angles caused by the soft tissue imbalance accounted for 53.2%, and caused by the bone structure accounted for 46.8%; and the latter caused by the tibia varus, 22.8%, and by the tibia plateau destruction, 24.0%. There was no significant difference between the varus angles caused by the soft tissue imbalance and the varus angles caused by the bone structure deformity (P > 0.05). According to the postoperative imaging studies, the correction degree for the varus angles by the bone-cutting was 4.3 degrees, which represented 27.9% of the total corrected angles, and the correction degree for the varus angles corrected by the soft tissue balance was 10.7 degrees, which represented 72.1% of the total corrected angles. The HSS scores were 87.0 +/- 4.5 points after operation, and the difference between preoperation and postoperation was significant.
The varus knee due to osteoarthritis results from the varus angle in the bone structure and the angles caused by the imbalance of the collateral ligaments and the soft tissues around the knee. The latter causative factor is more important in the formation of the varus knee and should only be corrected through the soft tissue release. The more important part to be released is the attachments of the medial ligament and the posterior capsule. The release performance should be followed by the principles, i.e., step by step, tests at all the time, and avoidance of the excessive release.