Objective: To introduce the method of prior-localization femoral tunnel by using a special positioning tool under the C-arm radiographic machine before surgery, and to study the effect on the knee function recovery after medial patellofemoral ligament (MPFL) reconstruction.
Methods: Between January 2014 and January 2016, 32 patients with recurrent unilateral knee patellar dislocation were treated by arthroscopic patellofemoral lateral retinaculum release and MPFL reconstruction. The femoral tunnel position during MPFL reconstruction was prior-localizated under C-arm radiographic machine before operation. There were 8 males and 24 females, aged from 15 to 37 years, with an average of 23.8 years. The time from injury to admission ranged from 1 to 24 months, with an average of 9.7 months. Isometric point distance was measured on CT three-dimensional reconstruction image after operation to evaluate whether the position of femoral tunnel was isometric, and knee joint function was evaluated by Lysholm score. Spearman correlation analysis was performed between isometric point distance and Lysholm score.
Results: All the 32 patients were followed up 12-18 months (mean, 14.2 months). No symptoms of patellar subluxation or dislocation was found during follow-up. Patellar extrapolation test and patellar extrapolation fear test were negative. The isometric point distance was 1.5-5.9 mm (mean, 3.44 mm) at 3 days after operation. All femoral tunnels were located in equidistant tunnels. At last follow-up, the Lysholm score of the patients was 92.8±2.1, which was significantly improved when compared with preoperative score (54.4±2.8) ( t=61.911, P=0.000). Isometric point distance was negatively correlated with Lysholm score ( r=-0.454, P=0.009).
Conclusion: C-arm radiographic machine can locate the femoral tunnel position of MPFL easily and accurately before operation. The short-term and medium-term effectiveness are satisfactory, and the ionizing radiation injury caused by multiple fluoroscopy during operation is avoided.
目的: 在内侧髌股韧带（medial patellofemoral ligament，MPFL）重建术前预先使用 C 臂 X 线机和皮外固定器定位股骨隧道位置，探讨其对复发性髌骨脱位患者术后膝关节功能恢复的影响。.
方法: 2014 年 1 月—2016 年 1 月，采用关节镜下髌股外侧支持带松解+MPFL 重建术治疗 32 例单侧膝复发性髌骨脱位患者，术前在 C 臂 X 线机下用皮外固定器预先定位 MPFL 重建术中股骨隧道位置。其中男 8 例，女 24 例；年龄 15～37 岁，平均 23.8 岁。受伤至入院时间 1～24 个月，平均 9.7 个月。术后于 CT 三维重建图像上测量等距点距离，评价股骨隧道位置是否等距，并采用 Lysholm 评分评价膝关节功能；将等距点距离与 Lysholm 评分行 Spearman 相关分析。.
结果: 32 例患者术后均获随访，随访时间 12～18 个月，平均 14.2 个月。随访过程中未出现髌骨半脱位或脱位症状，髌骨外推试验及髌骨外推恐惧试验均为阴性。术后 3 d 测量等距点距离为 1.5～5.9 mm，平均 3.44 mm；所有股骨隧道位置均为等距隧道。末次随访时，患者 Lysholm 评分为（92.8±2.1）分，较术前的（54.4±2.8）分显著改善，差异有统计学意义（ t=61.911， P=0.000）。等距点距离与术后 Lysholm 评分成负相关（ r=–0.454， P=0.009）。.
结论: C 臂 X 线机下皮外固定器辅助定位法可术前简便、准确定位 MPFL 重建的股骨隧道位置，中短期临床疗效满意，且避免了术中多次透视给患者及术者的电离辐射伤害。.
Keywords: Patellofemoral joint instability; femoral tunnel; isometric point; medial patellofemoral ligament; positioning tool.