| Purposes This paper aimed to optimize CT imaging measurement on patellofemoral anatomy of patients with recurrent patellar dislocation and to compare with controlled group without dislocation and to report normal and abnormal range of Chinese patellofemoral joint bony parameters.We further assessed male and female TT-TG distance and discussed appropriate imaging and surgical indications for tibial tuberosity transposition.Methods Patients were selected from Shanghai Sixth People’s Hospital between September 2013 to October 2015.The study group included 67 recurrent patellar dislocation patients(123 knees)and control group included 64 anterior cruciate ligament injury patients(64 knees).We used Osirix software to decide the corresponding reference surfaces,lines,points and to analyze patellofemoral joints among study group and the control groups’ CT image data.Prism statistics software was utilize to calculate diagnostic reference range for Chinese race.Results Compared to the control group,study group patients had a greater sulcus angle(139.32 ± 9.13 ° vs 128.93 ± 6.32 °),congruence angle(41.21 ± 23.01 ° vs 3.92 ± 17.82 °),patellar tilt angle(27.59 ± 9.42 ° vs 12.62 ± 5.47 °),lateral patellar angle(8.66 ± 10.34 ° vs-5.85 ± 7.21 °),lateral patellar translation(1.29 ± 0.79 vs 0.67 ±0.37 cm),TT-TG distance(18.39 ± 3.59 vs 13.92 ± 3.13 mm),Insall-Salvati index(1.37 ± 0.15 vs 1.12 ± 0.17);smaller lateral trochlear inclination angle(20.41 ± 5.19 vs 26.33 ± 4.25 mm),patella width(41.1 ± 3.9 vs 44.0 ± 3.8 mm)patella thickness(19.8 ± 2.3 vs 21.2 ± 2.0 mm),and statistically significant difference were found(P <0.05).Individual left and right knee TT-TG distance had no significant difference(P <0.05);ROC curve analysis rendered male abnormal cutoff TT-TG distance > 17.90 mm,women> 14.35 mm.Patellofemoral joint common risk factors for study group had higher prevalence(≥2 risk factors,69.92% vs 7.81%),mainly including a combination of abnormal TT-TG distance,patella alta and trochlear dysplasia(33.33 % vs 0.00%).Study group had more patella form of Wiberg III type(43.1% vs 15.6%);patellar Wiberg classification and trochlear Dejour classfication had no significant association;W/T index=2.1 remained consistent across study group and control group with no significant difference(P <0.05).Trochlear apex had an anteroposterior relationship with tibial tubercle;in study group apex is anterior to tibial tubercle in a larger proportion(69.1% vs 17.4%),and there was a significant difference(P <0.05).Conclusions This study presents a method for optimizing CT measurement of patellofemoral anatomy and provides with a comprehensive and systematic coverage of Chinese parameters of patellofemoral joint.Our statistics show that 1)TT-TG distance differences were related to gender,in which male TT-TG distance was larger and there was a significant difference compared with women;2)TT-TG distance is similar between left and right sides of the knee;3)women in control group had a positive correlation between patellar width and TT-TG distance.Further calculations conform to sex differences in recurrent dislocation TT-TG distance diagnostic reference values.After combined with a comprehensive analysis of the additional risk factors,we made an appropriate surgical indication for Chinese patients.We believed that women with TT-TG distance> 15mm;male patients TT-TG distance> 20 mm and not combined with other structural abnormalities of the patellofemoral joint(femoral dysplasia,patella alta,etc.);male patients TT-TG distance> 15 mm combined with other patellofemoral joint abnormalities.If the patient has Wiberg III patella,above TT-TG distance can also be appropriately widened for the tibial tuberosity transposition indications.We look forward to more imaging,biomechanics and clinical studies to further clarify the correlation between recurrent dislocation risk factors.Depending on the type and extent of the risk factors,assessment of the surgical risk and the expected effect of surgical treatments allows for a personalized plan. |
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