Recurrent Patellofemoral Instability in the Pediatric Patient: Management and Pitfalls

Abstract

Purpose of review: The purpose of the review is to discuss the relevant pathoanatomy, management, complications, and technical considerations for recurrent patellofemoral instability (PFI) in the pediatric population. Special consideration is given to recent literature and management of the patient with repeat instability following surgery.

Recent findings: Patellar stabilization surgery is in principle dependent upon restoration of normal patellofemoral anatomy and dynamic alignment. Historically, treatment options have been numerous and include extensor mechanism realignment, trochleoplasty, and more recently repair and/or reconstruction of the medial patellofemoral ligament (MPFL) as a dynamic check rein during initial knee flexion. In skeletally immature patients, preference is given to physeal-sparing soft tissue procedures. While medial patellofemoral ligament reconstruction has become a popular option, postoperative failure is a persistent issue with rates ranging from 5 to 30% for PFI surgery in general without any single procedure (e.g., distal realignment, MPFL reconstruction) demonstrating clear superiority. Failure of surgical patellar stabilization is broadly believed to occur for three main reasons: (1) technical failure of the primary stabilization method, (2) unaddressed static and dynamic pathoanatomy during the primary stabilization, and (3) intrinsic risk factors (e.g., collagen disorders, ligamentous laxity). PFI is a common orthopedic condition affecting the pediatric and adolescent population. Treatment of repeat instability following surgery in the PFI patient requires understanding and addressing underlying pathoanatomic risk factors as well as risks and reasons for failure.

Keywords: Patellar dislocation; Patellar instability; Patellar stabilization; Pediatric; Revision patella surgery; Skeletally immature.

Fig. 1

Schematic showing radiographic landmarks used to determine isometric femoral insertion of the medial patellofemoral ligament (Schottle’s point). A line is drawn as an extension to the posterior diaphyseal femoral cortex (PFC) distally (red). A second line is drawn from the posterior tip of Blumensaat’s line perpendicular to the PFC (purple). A third line is drawn from the posterior origin of the medial femoral condyle (MFC) perpendicular to the PFC (blue). Schottle’s point is located anterior to the PFC and between lines 2 and 3

Fig. 2

Schematic showing the insertions of the medial patellofemoral ligament (MPFL) on the patella and femur in relation to other bony anatomic landmarks. The MPFL inserts on the proximal half of the medial patella (yellow oval) as well as the “saddle point” (red circle) between the adductor tubercle (purple circle) and medial epicondyle (blue circle) of the distal femur