Treatment of a first-time acute patellofemoral dislocation in the adolescent athlete is usually nonsurgical unless associated with an articular cartilage fracture. In the setting of recurrent patellar instability, surgical reconstruction is indicated after nonoperative treatment has failed. The medial patellofemoral ligament (MPFL) is the primary restraint to patellofemoral instability at 0 to 30 degrees of flexion and provides more than 50% of the medial restraint to the patella.³,²² The patella is most prone to dislocate from 0 to 30 degrees of knee flexion.²⁵ The MPFL helps to guide the patella into the trochlear groove during early knee flexion. Once the patella is in the trochlea groove, the slope of the lateral patella facet provides the primary restraint to lateral translation.¹⁰,¹³ The origin of the MPFL is near the adductor tubercle on the medial femoral epicondyle at or just distal to the distal femoral physis.¹⁵,¹⁷ In children and adolescents, a large drill hole in this area risks physeal injury.¹⁴ The MPFL originates about 1 cm distal to the superior pole of the patella on the upper third of the medial patella. The MPFL is about 55 mm long and 15 mm wide.³¹ The MPFL is torn during acute lateral patellar dislocations in the majority of patients.²⁴,²⁶

Surgical treatment of patellofemoral instability in the adolescent athlete has evolved from nonanatomic extensor mechanism realignment procedures to anatomic restorative procedures based on reconstitution of the MPFL.

Many surgical procedures have been described for treatment of recurrent patellar instability.¹,²⁰ The surgical approach should be individualized for each patient and should address the pathoanatomy contributing to the repeat dislocations. Often, combinations of procedures are needed to correct all patellofemoral problems.²⁸ No single procedure has been shown to be indicated in all patients with patellar dislocations. Surgical options for patellofemoral instability in adolescents includes proximal realignment, distal realignment, lateral release, MFPL reconstruction, guided growth with tension band plates, and combinations of the earlier procedures.¹⁴ Osteotomies of the proximal tibia or distal femur are reserved for older teenagers who have demonstrated closure of the growth plates.¹⁸ The goal of MPFL reconstruction is to reestablish the normal checkrein against lateral motion of the patella. When reconstructing the MPFL, it is important to replicate the native anatomy. In most chronic cases, reconstruction is recommended rather than MPFL repair because the chronically injured medial retinacular tissues are usually insufficient to reestablish the normal tether to prevent lateral dislocation. Multiple graft choices have been used for MPFL reconstruction including hamstrings,¹⁶ patellar tendon,⁵,¹⁵ adductor magnus,³⁰ allografts, and the quadriceps tendon.¹²,²⁰,³²

Isolated MPFL reconstruction may not be sufficient to prevent recurrent dislocation if other risk factors such as patella alta, patella tilt, an increased Q angle, a tibial tuberosity-trochlear groove (TT-TG) distance of more than 20 mm, or trochlear dysplasia are also present.⁷,⁹,³⁴ Treatment of the other risk factors can be combined with an MPFL reconstruction.

Indications for surgical treatment of patellar instability in the adolescent athlete include repeat patellar dislocations that have failed nonoperative treatment.¹⁴ The essential lesion in chronic lateral is patellofemoral instability insufficiency of the MPFL.¹⁹ The ideal indications for an isolated MPFL reconstruction in a child or adolescent would be a recurrent lateral patellar dislocation without valgus malalignment, patella alta, or trochlear dysplasia.

For the adolescent athlete with recurrent patellar dislocations, we prefer an anatomic MPFL reconstruction using the medial quadriceps tendon. This technique avoids injury to the
growth plates and is particularly applicable to the skeletally immature pediatric and adolescent athlete. This technique is a combination of previously described techniques by Noyes and Albright,²⁰ Steenson et al.,³² and Goyal.¹² An 8- × 70-mm full-thickness strip of medial quadriceps tendon is used to reconstruct the MPFL. The quadriceps graft is left attached to the superomedial border of the patella. The free end of the graft is passed between the synovium and the retinaculum and is sutured to the medial intermuscular septum adjacent to the medial femoral epicondyle (Figs. 16.1 and 16.2). Femoral fixation is augmented with a small absorbable suture anchor placed via C-arm direction to ensure accurate placement of the graft. The remaining medial retinaculum is imbricated when the quadriceps tendon harvest site is closed. This technique avoids large patella and femoral drill holes and minimizes the risk of patellar fracture or injury to the distal femoral physis. The graft is tensioned at 30 to 45 degrees of knee flexion. A lateral release is added if tightness of the lateral retinaculum prevents normal medial patellar translation or in cases of abnormal patellar tilting.

The goal of MPFL reconstruction is to replace the torn ligament with a graft that is stronger than the native MPFL and with a tension similar to the native ligament. Normal patellar motion allows about two patella quadrants of lateral translation.² Graft tensioning should be performed with the knee in about 30 to 45 degrees of flexion.¹¹,¹⁶ In addition, we use the C-arm to help locate the femoral attachment site. Schöttle et al.²⁷ and Redfern et al.²³ have described radiographic landmarks to locate the anatomic femoral position of the MPFL. The femoral attachment site is very important for achieving a good outcome.²⁵ For example, in cadaver studies, Steensen et al.³¹ and Stephen et al.³³ demonstrated that the position of the MPFL graft femoral attachment substantially influenced the graft length change pattern. The patellar attachment site, on the other hand, had little effect. The most common error in graft placement is to fix the graft too far anteriorly on the femur which may lead to graft laxity in extension and graft tension in flexion. This graft malposition can lead to overloading of the medial patellofemoral cartilage, anterior knee pain, and loss of flexion.⁴,⁸,³⁵ In addition, Camp et al.⁶ reported that a nonanatomic MPFL femoral attachment site can result in a high rate of recurrent patellar dislocation following MPFL reconstruction. An overtightened graft combined with a lateral release can result in iatrogenic medial patellar subluxation in flexion.⁴ After graft fixation, knee motion should be equal to the opposite knee and there should be a good end point to lateral patellar translation from 0 to 30 degrees of knee flexion.