Isolated Avulsion Fracture of Patellar Attachment of Medial Patellotibial and Medial Patellomeniscal Ligaments in the Presence of Trochlear Dysplasia: An Indication for Acute Surgical Repair

Abstract

We present the case of a 13-year-old female athlete with acute traumatic lateral patellar dislocation. Patella reduced spontaneously with knee extension. Clinical examination revealed pain and tenderness at the middle/inferior part of the medial patellar border. An MRI showed an avulsion fracture at the middle/inferior part of the medial patellar border along with type C dysplastic trochlea and medial femoral condyle hypoplasia. On examination under anesthesia, the patella was stable in extension, indicating intact medial patellofemoral ligament (MPFL), but dislocated beyond 30 degrees of knee flexion. Surgical repair of the common patellar attachment of medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML) by means of strong nonabsorbable transosseous sutures was performed, in order to allow healing of MPTL/MPML with the patella centered on the trochlear groove. The follow-up was uncomplicated. It is concluded that isolated acute traumatic insufficiency of MPTL/MPML with coexisting trochlear dysplasia, even with intact MPFL, is an indication for acute surgical MPTL/MPML repair in order to compensate for the inherent osseous instability of the patellofemoral joint.

Patellar Dislocation: Workup and Decision-Making

“…This is explained biomechanically because the MPML/MPTL complex is in line with the quadriceps and is the first to oppose quadriceps contraction, which is the triggering force of PD [37,39]. Furthermore, in the case of concomitant severe TD, isolated MPTL/MPML rupture may lead to PD without simultaneous MPFL rupture (Figure 6) [40].…”

“…Avulsion fractures of the patellar attachments of the medial patellar restraints may be observed in the context of ligamentous medial restraint injury [27,37]. Avulsion fractures should be fixed if they involve the medial patellar facet [41] or if the increased number and severity of patellar instability factors favor early surgery [40]. Free intra-articular osteochondral fragments should be reduced anatomically and fixed with absorbable pins; however, fragment fixation may be impossible for very small fragments (<1-1.5 cm), which are removed (Figure 8) [16].…”