A Closer Look is necessary: Traumatic luxation of the patella as a co-injury of an acl-rupture

AIMS AND OBJECTIVES: The rupture of the acl is considered to be one of the most common knee injuries in sports traumatology. Many patients report that they felt the sensation of a luxated patella during their knee distorsion. In many cases patients patients with the suspicion of a traumatic patella luxation showed in the mri a complete rupture of the acl. MATERIALS AND METHODS: We report about 10 patients consulting our department within the last year after a significant knee trauma. In the mri as well as during the arthroscopic evaluation they showed a complete rupture of the acl as well as the findings of a fresh, traumatic patella luxation. We evaluated and analysed the preoperative and intraoperative pictures (mri and arthrosopy). RESULTS: All patients showed in the posttraumatic mri a complete rupture of the acl as well as an at least partial rupture of the mpfl and a rupture of the medial retinaculum. 4 patients showed a persistent subluxation of the patella, 8 patients showed also a rupture of the medial collateral ligament. During the operation we verified a significant instability of the patella in 8 patients so that a stabilization of the patella was performed (open medial stabilization or mpfl reconstruction) in the same operation the acl was reconstructed (semi-t). Eventhough the patients were treated with only one operation and the regaining of motion was prolonged compared with isolated acl-reconstruction, after 12 months postoperatively all patients had a satisfactory range of motion. CONCLUSION: The typical trauma mechanism for an acl rupture is a valgus position of the knee in combination with an external rotation of the tibia, which leads to an enlargement of the q-angle which is considered a predisposition for a patella luxation. If an acl rupture occurs, the patella can luxate within the same trauma. In the posttraumatic mri the rupture of the mpfl is often misinterpreted as a rupture of the medial collateral ligament, particularly if the patella is, as in most cases, in full reposition. Within an acl-rupture a luxation of the patella can occur simultaneously, leading to a significant instability which needs to be treated (medial stabilization or mpfl-reconstruction). Our data shows that a single stage treatment with acl-reconstruction and medial stabilization is technical practicable and mid-term investigation shows good clinical results without a higher risk of an arthrofibrosis.