Background The radiological indicators can help doctors determine whether to make tibial tubercle transfer. But which indicator is better is still in question. Methods 117 knees in 103 patients who had undergone patellar surgery and 60 knees in 58 patients who had no history of patellar dislocation from 2014 to 2019 were analyzed. Significant differences of tibial tubercle–trochlear groove (TT-TG) on CT and tibial tubercle–posterior cruciate ligament (TT-PCL) on MRI between the case group and the control group were estimated by an unpaired t test. Significant differences between TT-TG on CT and TT-TG on MRI were estimated by a paired t test. The correlation between TT-PCL on MRI and tibial width was estimated by Pearson test. Receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC) were measured to assess the diagnostic accuracy of TT-TG and TT-PCL on MRI. Results The intraclass correlation coefficient (ICC) for TT-TG between CT and MRI evaluated by two raters was were 0.566. When comparing TT-TG on CT with that on MRI, the mean difference was 2.5 mm (p< 0.001). The mean TT-TG difference on CT between the case group and the control group was 5.3 mm, which was significantly bigger than the mean TT-PCL difference on MRI of 1.2 mm(p< 0.001). AUC of TT-TG on CT and TT-PCL were 0.838 and 0.580 (P< 0.001). TT-PCL correlated with tibial width (r=0.450, P< 0.001). Conclusion A statistically significance and a fair ICC proved that TT-TG could not be used interchangeably. The bigger mean difference between the case group and the control group and better AUC proved that TT-TG on CT might be an indicator more suitable for measuring the lateralization of the tibial tubercle. And TT-PCL should be considered as an individual parameter because of the significant correlation between TT-PCL and tibial width.

Background Medial patellofemoral ligament (MPFL) reconstruction combined with tibial tubercle osteotomy (TTO) and lateral retinacular release (LRR) is one of the main treatment methods for patellar instability. So far, few studies have evaluated the clinical effectiveness and assessed potential risk factors for recurrent patellar instability. Purpose To report the clinical outcomes of MPFL reconstruction combined with TTO and LRR at least three years after operation and to identify potential risk factors for recurrent patellar instability. Methods A retrospective analysis of medical records for patients treated with MPFL, TTO and LRR from 2013 to 2017 was performed. Preoperative assessment for imaging examination included trochlear dysplasia according to Dejour classification, patella alta with the Caton-Deschamps index (CDI), tibial tubercle–trochlear groove distance. Postoperative assessment for knee function included Kujala, IKDC and Tegner scores. Failure rate which was defined by a postoperative dislocation was also reported. Results A total of 108 knees in 98 patients were included in the study. The mean age at operation was 19.2 ± 6.1 years (range, 13–40 years), and the mean follow-up was 61.3 ± 15.4 months (range, 36–92 months). All patients included had trochlear dysplasia (A, 24%; B, 17%; C, 35%; D, 24%), and 67% had patellar alta. The mean postoperative scores of Tegner, Kujala and IKDC were 5.3 ± 1.3 (2–8), 90.5 ± 15.5 (24–100) and 72.7 ± 12.1 (26–86). Postoperative dislocation happened in 6 patients (5.6%). Female gender was a risk factor for lower IKDC (70.7 vs 78.1, P = 0.006), Tegner (5.1 vs 6.0, P = 0.006) and Kujala (88.2 vs 96.6, P = 0.008). Age (p = 0.011) and trochlear dysplasia (p = 0.016) were considered to be two failure factors for MPFL combined with TTO and LRR. Conclusion As a surgical method, MPFL combined with TTO and LRR would be a reliable choice with a low failure rate (5.6%). Female gender was a risk factor for worse postoperative outcomes. Preoperative failure risk factors in this study were age and trochlear dysplasia. Level of Evidence Level IV; Case series

BackgroundThe radiological indicators can help doctors determine whether to make the tibial tubercle transfer. But that which indicator is better is still in question.Methods117 knees in 103 patients who had gone through patellar surgery and 60 knees in 58 patients who had no history of patellar dislocation from 2014 to 2019 were analyzed. Significant differences of tibial tubercle–trochlear groove (TT-TG) on CT and tibial tubercle–posterior cruciate ligament (TT-PCL) on MRI between the case group and the control group were estimated by an unpaired t test. Significant differences between TT-TG on CT and TT-TG on MRI were estimated by a paired t test. The correlation between TT-PCL on MRI and tibial width was estimated by Pearson test. Receiver operating characteristic (ROC) curves and the area under the ROC curve (AUC) were measured to assess the diagnostic accuracy of TT-TG and TT-PCL on MRI. ResultsThe intraclass correlation coefficient (ICC) for inter-method of TT-TG evaluated by two raters was were 0.566. When comparing TT-TG on CT with that on MRI, the mean difference was 2.5mm (p<0.001). The mean TT-TG difference on CT between the case group and the control group was 5.3 mm, which was significantly bigger than the mean TT-PCL difference on MRI of 1.2mm(p<0.001). AUC of TT-TG on CT and TT-PCL were 0.838 and 0.580 (P<0.001). TT-PCL correlated with tibial width (r=0.450, P<0.001). ConclusionA statistically significance and a fair ICC proved that TT-TG could not be used interchangeably. The bigger mean difference between the case group and the control group and better AUC proved that TT-TG on CT might be an indicator more suitable for measuring the lateralization of the tibial tubercle. And TT-TG should be considered as an individual parameter because of the significant correlation with tibial width.