Treatment of First-time Patellar Dislocations and Evaluation of Risk Factors for Recurrent Patellar Instability Approximately one-third of skeletally mature patients with primary patellar dislocation will experience recurrent patellar instability over time. Because of the multifactorial combination of features contributing to overall stability of the patellofemoral joint, first-time patella dislocation presents a challenge to the treating physician. A detailed patient history, focused physical examination, and appropriate diagnostic imaging are essential for identifying risk factors for recurrent instability. Individual risk factors include young patient age, patella alta, trochlear dysplasia, and lateralization of the tibial tubercle. In combination these factors may pose even greater risk, and recently published predictive scoring models offer clinicians objective criteria to identify patients most at risk for recurrence. In patients at low risk of recurrence, nonoperative management can be effective, with “a la carte” surgical treatments gaining popularity in those with a higher than acceptable risk of re-dislocation.

An Updated Overview of the Anatomy and Function of the Proximal Medial Patellar Restraints (Medial Patellofemoral Ligament and the Medial Quadriceps Tendon Femoral Ligament) The medial patellofemoral ligament (MPFL) has been widely accepted to function as “the primary static restraint to lateral patellar displacement.” However, current growing evidence suggests that there is a complex of medial patellofemoral/tibial ligaments, both proximal [MPFL, and medial quadriceps tendon femoral ligament (MQTFL)], and distal (medial patellotibial ligament and the medial patellomeniscal ligament) which restrain lateral patellar translation at different degrees of knee flexion. Specifically, the MQTFL has gained popularity over the last decade because of pure soft tissue attachments into the extensor mechanism that allow for avoidance of drilling tunnels into the patella during reconstruction. The purpose of this article was to report on the current knowledge (anatomy, biomechanics, diagnosis, indications for surgery, and techniques) on the proximal medial patellar restraints, namely the MPFL and the MQTFL, collectively referred to as the proximal medial patellar restraints.

Concepts of the Distal Medial Patellar Restraints: Medial Patellotibial Ligament and Medial Patellomeniscal Ligament The important medial patellar ligamentous restraints to lateral dislocation are the proximal group (the medial quadriceps tendon femoral ligament and the medial patellofemoral ligament) and the distal group [medial patellotibial ligament (MPTL) and medial patellomeniscal ligament (MPML)]. The MPTL patellar insertion is at inferomedial border of patella and tibial insertion is in the anteromedial tibia. The MPML originates in the inferomedial patella, right proximal to the MPTL, inserting in the medial meniscus. On the basis of anatomy and biomechanical studies, the MPTL and MPML are more important in 2 moments during knee range of motion: terminal extension, when it directly counteracts quadriceps contraction. In a systematic review on MPTL reconstructions 19 articles were included detailing the clinical outcomes of 403 knees. All were case series. Overall, good and excellent outcomes were achieved in >75% of cohorts in most studies and redislocations were <10%, with or without the association of the medial patellofemoral ligament. The MPTL is a relevant additional tool to proximal restraint reconstruction in select patient profiles; however, more definitive clinical studies are necessary to better define surgical indications.

The Ribbon-shaped Femoral Footprint of the Medial Patellofemoral Ligament: Implications for Reconstruction The medial patellofemoral ligament (MPFL) is the primary static stabilizer to lateral translation of the patella and serves as part of the medial patellar soft tissue restraints. Because of the sensitivity of MPFL graft function after reconstruction to the position of the femoral tunnel, many studies have aimed to identify the exact point of the femoral origin, as well as defining techniques to confirm this position intraoperatively. We describe the ribbon-shaped footprint of the MPFL on the medial femur and the associated difficulty in identifying the origin as a single “point.” Varying isometry and biomechanical functions have been shown to exist within the most proximal and most distal fibers, suggesting the function of the MPFL may not be fully recreated with a tubular graft in a round tunnel. We review the anatomical descriptions of the elongated femoral footprint of the MPFL and describe our surgical technique to recreate this.

Why and Where to Move the Tibial Tubercle: Indications and Techniques for Tibial Tubercle Osteotomy Patellofemoral disorders including pain and instability are common orthopedic problems, particularly in the adolescent population. Patellofemoral pain is usually anterior, poorly localized, and diffuse. Because of its multifactorial etiology, patellofemoral pain can be clinically challenging to diagnose and manage. With regards to instability, predisposing factors include trochlear dysplasia, patella alta, patellar tilt, and an elevated tibial tuberosity and trochlea groove distance. Initially, nonoperative management is recommended to treat patellofemoral maladies such as overload, maltracking, and acute first-time dislocations. However, tibial tubercle transfer (TTT) is commonly used to address cases of symptomatic malalignment and overload and recurrent patellar instability. The tubercle can be translated in multiplanar directions to correct patellar height, maltracking associated with instability, and to offload chondral defects. A thorough understanding of the anatomy and biomechanics of the patellofemoral joint is essential for optimizing results after TTT. Individualizing the direction and degree of tubercle transfer on the basis of patient parameters is critical to producing successful long-term results after surgery. This article will review the indications for performing a TTT and highlight the various techniques.

When to Add Lateral Soft Tissue Balancing? Lateral patellofemoral (PF) soft tissue abnormalities range from excessive lateral PF tightness (lateral patellar compression syndrome, lateral patellar instability and arthritis), to excessive laxity (iatrogenic lateral PF soft tissue insufficiency postlateral release). The lateral soft tissue complex is composed of the iliotibial band extension to the patella, the vastus lateralis tendon, the lateral PF ligament, lateral patellotibial ligament, and lateral patellomeniscal ligament, with intimate connections between those structures. To identify lateral retinaculum tightness or insufficiency the most important tests are the patellar glide test and patellar tilt test. Imaging aids in that evaluation relying mostly on the patella position assessed by radiographs, computed tomography, and magnetic resonance imaging with referencing to the posterior femoral condyles. Lateral retinaculum lengthening (preferred) or release may be added when there is excessive lateral retinaculum tightness. A lengthening may be performed using a minimally invasive approach without compromising the lateral patella restraint. Lateral retinaculum repair or reconstruction is indicated when there is lateral retinaculum insufficiency. Lateral retinaculum surgery to balance the medial/lateral soft tissue restraints, improves patellar positioning and clinical results.

When is Trochleoplasty a Rational Addition? Trochlear dysplasia has been recognized as a dominant anatomic risk factor in patients with recurrent patellar instability. Sulcus-deepening trochleoplasty is a very effective and powerful procedure for correcting trochlear dysplasia and, specifically, eliminating the supratrochlear spur. However, it must be emphasized that trochleoplasty is not appropriate for patients with mild trochlear dysplasia or those without a large supratrochlear spur or bump. We discuss the characteristics and classification of trochlear dysplasia and discuss specific indications for sulcusdeepening trochleoplasty.

When and How I Add Trochleoplasty in the Treatment of Recurrent Patella Instability Long experience and recent evidence suggest that trochleoplasty is needed in very few patella stabilization surgeries. As trochleoplasty adds risk, this author recommends it only in patients with high degrees of dysplasia, prominent supratrochlear spurs, ligamentous laxity, and more dramatic J signs.

Pediatric Management of Recurrent Patellar Instability Patellofemoral instability is a common orthopedic condition in children and adolescents, with recurrent instability often requiring surgical intervention. Age, bilateral instability, and various anatomic features such as trochlear dysplasia, patella alta, increased tibial tubercle to trochlear groove distance, and patellar tilt have all been described as risk factors for recurrent patellar instability. Medial patellofemoral ligament reconstruction has become the mainstay of treatment for addressing recurrent patellar instability in skeletally immature patients. For some patients, additional interventions such as distal realignment and guided growth procedures may be required to address anatomic pathology. This article discusses various risk factors associated with patellofemoral instability, reconstruction techniques, and a case example.