Objective To analyze formation of the varus angle of the knee dueto osteoarthritis and to explore techniques of the soft tissue balance in the total knee arthroplasty(TKA). Methods One hundred patients with145 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 bonecutting 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 bonecutting. Release of themedial ligament and capsule, elimination of the osteophytes, and release of thelateral patellar retinaculum were more important. Results The varus angles in these patients were 9.2±3.1° 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 thetibia varus, 22.8%, and by the tibia plateau destruction, 24.0%. There was nosignificant 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°, 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°, 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. Conclusion 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 isthe 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.
Objective To analyze the relationship between the collateral ligament attachment and the epicondylar axis with rotational alignment of the femoral component in the total knee arthroplasty(TKA).Methods Twenty normal cadaver knee joints were anatomized and 2 holes were drilled on the distal femur from the deep and superficial insertions of the medial collateral ligaments to the lateral condylar part, respectively. Then, all the knees were scanned by MRI on the sagittal plane, making the drilled hole located relatively to the posterior condylar joint surface on the axial plane, and the posterior condylar angle (PCA) and thecondylar twist angle (CTA) were measured.Results The colateral ligament had the deep and superficial parts, and the deep part was strained during the knee flexing. PCA and CTA were 4.50±1.26° and 7.10±0.30° respectively, and there was a significant difference between them(P＜0.05), which were significantly greater than those reported abroad. On the sagittal plane, there wasno significant difference between the radiuses of the posterior medial and lateral condylar circles (Pgt;0.05). The distance from the center of the posterior condylar circle to the deep insertion of the medial collateral ligament (MCL) (d1) was 4.22±0.20 mm, and the distance to the superficial insertionof MCL (d2) was 7.36±0.13 mm. The difference between d1 and d2 was significant(Plt;0.05). Conclusion The center of the posterior condylar circle passes from the deep insertion of the collateral ligament, which can be regarded as a fixed flexionextension axis of the knee. By releasing the different parts of the collateral ligaments, the balance of the flexion and extension gap canbe obtained, and then varus, valgus or flexed contracture deformity of the kneecan be realigned. Besides, the rotational orientation of the femoral prothesis can be made by a reference to the epicondylar insertion of the collateral ligament.