骨性关节炎患者人工膝关节假体旋转定位标志研究

目的探讨对合并内、外翻畸形的膝关节骨性关节炎行人工全膝关节置换术，以股骨内外上髁外科轴（surgical epicondylar axis，SEA）作为股骨假体旋转参考轴，以胫骨结节内1／3作为胫骨假体旋转定位的骨性标志，判断股骨假体和胫骨假体的旋转对线情况。方法2004年7月～2005年1月，对32例（62膝）拟行人工全膝关节置换术的膝关节骨性关节炎患者（病例组），男2例，女30例；年龄58～80岁，平均68．9岁；内翻畸形55膝，胫股角平均内翻-8．23°；外翻畸形7膝，胫股角平均外翻＋15．48°。于术前行伸膝旋转中立位CT扫描，测量膝关节股骨后髁角（posterior condylar angle，PCA），并以10个正常膝关节作为对照组，测量SEA中点C与髌腱内1／3连线（BC）和经SEA中点C的垂线（AC）之间的夹角，即α角。结果病例组80％以上膝关节CT图像显示股骨内上髁陷凹；PCA中位数为＋2．36°（0～＋7．5°）；对照组膝关节α角为＋6．45±3．68°（0～＋11．8°）；病例组内翻畸形患者膝关节α角为＋10．85±10．47°（0～＋28．1°），与对照组比较差异有统计学意义（P〈0．05），病例组外翻畸形患者膝关节α角为＋11．6±7．3°（-6．5～＋26．8°），与对照组比较差异有统计学意义（P〈0．05）。结论以胫骨结节内1／3作为胫骨假体旋转参考轴线，胫骨假体相对于股骨假体处于轻度外旋位；合并内、外翻畸形患者的胫骨假体外旋角度明显增大，容易使股骨假体和胫骨假体间出现旋转对线不良。

ROTATIONAL LANDMARKS AND TOTAL KNEE ARTHROPLASTY IN OSTEOARTHRITIC KNEES

OBJECTIVE: To investigate the rotational mismatch of total knee replacement with medial 1/3 of tibial tuberosity as bony landmark in osteoarthritic patients with varus or valgus deformity. METHODS: Axial images on computed tomography of 62 knees (including 55 varus deformities and 7 valgus deformities) in 32 Chinese osteoarthritic patients who had total knee arthroplasty were analyzed, compared with that of 10 healthy knees. On images of the distal femur, the angle between the lines of surgical epicondylar axis (SEA) and posterior condylar axis was measured as posterior condylar angle (PCA), and on images of the proximal tibia, a baseline for the anteriorposterior axis of each component was drawn based on the SEA for the femur and the medial 1/3 of the tibial tuberosity for the tibia. The angle between these lines (Angle a) was defined as the rotational mismatch between the components when they were aligned to the anatomic landmarks of each bone. RESULTS: The sulcus of medial epicondyle of femur could be identified on CT images of over 80% osteoarthritic knees; the median value of PCA was +2.36 degrees, with an individual variation of 0 degree to +7.5 degrees. Angle a was +6.45 +/- 3.68 degrees (range, 0 degree to +11.8 degrees) in 10 healthy knees, which increased significantly to +10.85 +/- 10.47 degrees (range, 0 degree to +28.1 degrees) in 55 varus knees (P < 0.05), which also increased significantly to +11.6 +/- 7.3 degrees (range, -6.5 degrees to +26.8 degrees) in 7 valgus knees (P < 0.05). CONCLUSION: With the medial 1/3 of the tibial tuberosity as the rotational landmark for the tibial component, there was a tendency to align the tibial component in external rotational position relative to the femoral component in knees with normal alignment, the rotational mismatch increased in Chinese osteoarthritic knees with varus and valgus deformity.