Nove-Josserand L, Dejour D
Service Professeur H. Dejour, Centre Hospitalier Lyon-Sud, Pierre-Bénite.
Rev Chir Orthop Reparatrice Appar Mot. 1995;81(6):497-504.
Dysplasia of the vastus medialis, a well-known landmark of patellar instability, is difficult to point out pre-operatively. We propose the measurement of patellar tilt on the CT scans in order to appreciate abnormality.
We studied 3 well defined groups: 143 knees operated on for a true dislocation of the patella, either for the first time or a recurrent episode, 67 asymptomatic and nonoperated contralateral knees and 54 control knees. The patellar tilt in extension was measured on the CT-scan with the quadriceps relaxed and contracted.
The results showed the increase of the patellar tilt as an characteristic factor of patellar instability (28.8 + 10.5 degrees against 11.8 degrees + 5.7 degrees in the control group). Patellar tilt was not a consequence of the dislocation because it was also significantly increased in the asymptomatic contralateral group (17 degrees + 9 degrees). Quadricipital contraction increased the patellar tilt only in the two groups of patellar instability (+ 6 degrees) and asymptomatic contralateral group (+ 13 degrees) but not in the control group (+ 1.6 degrees). The mean of the relaxed and the contracted quadriceps patellar tilt includes the dynamic trouble. We propose the threshold of 20 degrees to determine a pathological patellar tilt. In this case, sensibility is 90 per cent and the specificity is 91 per cent. In the other patellar instability factors, only severe trochlear dysplasias involved the patellar tilt.
We think that the patellar tilt in extension is a landmark of a functional disorder of the whole quadriceps muscle more than the vastus medialis only. The mean of the relaxed and contracted quadriceps patellar tilt measures permitted to point out the border cases of this functional abnormality. This measurement is reliable and can be considered pathologic above 20 degrees. The results of Insall's muscular plasty were only symptomatic because this procedure could not correct the effect of the quadricipital contraction.
股内侧肌发育异常是髌骨不稳定的一个著名标志，术前很难指出。我们建议在CT扫描上测量髌骨倾斜度，以评估异常情况。
我们研究了3个明确界定的组：143例因髌骨真正脱位而接受手术的膝关节，无论是首次脱位还是复发性脱位；67例无症状且未接受手术的对侧膝关节；54例对照膝关节。在股四头肌放松和收缩的情况下，在CT扫描上测量伸直位时的髌骨倾斜度。
结果显示，髌骨倾斜度增加是髌骨不稳定的一个特征因素（28.8±10.5度，而对照组为11.8度±5.7度）。髌骨倾斜不是脱位的结果，因为在无症状对侧组中也显著增加（17度±9度）。股四头肌收缩仅在两组髌骨不稳定组（增加6度）和无症状对侧组（增加13度）中增加了髌骨倾斜度，而在对照组中未增加（增加1.6度）。股四头肌放松和收缩时的髌骨倾斜度平均值包括动态问题。我们建议以20度为阈值来确定病理性髌骨倾斜度。在这种情况下，敏感性为90%，特异性为91%。在其他髌骨不稳定因素中，只有严重的滑车发育异常涉及髌骨倾斜度。
我们认为，伸直位时的髌骨倾斜度更多地是整个股四头肌功能障碍的一个标志，而不仅仅是股内侧肌的标志。股四头肌放松和收缩时的髌骨倾斜度测量平均值有助于指出这种功能异常的临界情况。这种测量是可靠的，超过20度可被认为是病理性的。因萨尔肌肉成形术的结果只是对症的，因为该手术无法纠正股四头肌收缩的影响。
