Anatomic Risk Factors for Osteochondral Fracture of Acute First-Time Patellar Dislocation in Adolescents: A Retrospective Magnetic Resonance Imaging Study

Abstract

Objective. To analyze the risk factors for osteochondral fracture (OCF) of first-time acute patellar dislocation (APD) through measurements of patellofemoral anatomy in adolescents. Methods. In this prospective study, all patients were divided into two groups according to whether OCF was detected on magnetic resonance imaging (MRI): Group A (associated with OCF) and Group B (without OCF). Patellofemoral anatomy was evaluated with four aspects including trochlear/patellar dysplasia, patella location, patellofemoral matching, and morphologic classification. On MRI scans, trochlear facet asymmetry ratio (TFAR), lateral trochlear inclination (LTI), sulcus angle (SA), trochlear depth (TD), and patellar depth (PD) were measured to assess trochlear/patellar dysplasia. Insall–Salvati index (ISI), Caton–Deschamps index (CDI), Blackburne–Peel index (BPI), lateral patellofemoral angle (LPFA), patellar tilt angle (PTA), and lateral patellar displacement (LPD) were measured to show the location of patella. Patellofemoral matching was analyzed through the measurements of patellofemoral congruence angle (PFCA), patellofemoral index (PFI), and patellotrochlear index (PTI). Results. A total of ninety-four adolescents from 49 boys and 45 girls (mean age, 15 years; range, 10–18 years) with first-time APD were recruited and included in Group A (65) and Group B (29). The PFI (2.62 ± 0.51 vs. 2.10 ± 0.44) and PTI (0.28 ± 0.05 vs. 0.22 ± 0.07) were significantly higher in Group B than Group A P < 0.05 . There were no significant differences in other quantitative outcomes of the two groups P > 0.05 . The distribution of Dejour/Wiberg classification was statistically similar between the two groups P > 0.05 . Conclusions. Adolescent patients with first-time APD complicating OCF have closer morphologic features of patellofemoral dysplasia and patella location when compared to adolescents without OCF. Abnormal patellofemoral matching increases the risk of OCF after first-time APD in adolescents.

Patellar Lateralization, Absence of Joint Hypermobility, and the Mechanism of Injury Are Associated With Osteochondral Fracture After First-time Acute Lateral Patellar Dislocation in Adolescents: An MRI-based Evaluation

“…Although the mechanism of injury was not found to be an independent risk factor in the logistic regression analysis, this finding demonstrated that the risk of developing OCF in APD is multifactorial, and the mechanism of injury is one of these factors. Li et al 16 found no relationship between the risk of OCF and the mechanism of injury. Although the mechanism of injury has not been evaluated in other studies, it has been reported that highenergy dislocations in the patellofemoral joint may cause OCF due to the greater force exerted on the cartilage surface.…”

“…None of the previous studies investigating the causes of OCF in APD have evaluated the presence of joint hypermobility. [14][15][16][17] Joint hypermobility is seen in patients with hyperlaxity due to ligament and connective tissue laxity. Therefore, joint subluxations and dislocations may occur even in minor traumas in these patients.…”

“…In that study, it was reported that abnormal lateralization of the patella causes chronic loads on the lateral femoral condyle and patella, which may lead to OCF. 14 Li et al 16 evaluated patients with and without OCF in first-time APD and found no significant relationship between lateral patellar displacement and the groups. From an evaluation of cartilage lesions in APD, Zheng et al 17 found that the normal TT-TG distance was a risk factor for patellar cartilage lesions, but no relationship was determined between the lesions seen in the femur and the TT-TG distance.…”

“…Studies on this subject have started to be conducted in recent years, but the results are contradictory, and no consensus has been reached. [14][15][16][17] When evaluating risk factors for OCF, it is necessary to consider not only intra-articular anatomic risk factors but also patient-related factors such as trauma mechanism and joint hypermobility. Therefore, the aim of this study was to investigate the risk factors for osteochondral fracture by evaluating patients with and without OCF after first-time APD.…”

“…However, the risk factors associated with OCFs, which are very important in terms of treatment and prognosis after APD, have not been as clearly defined. Studies on this subject have started to be conducted in recent years, but the results are contradictory, and no consensus has been reached 14–17 …”