Medial Retinaculum Reefing for Patellar Instability

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Patellofemoral instability occurs commonly in young and active patients. A spectrum of clinical entities can be identified according to the Dejour classification [1]: objective patellar instability (OPI), potential patellar instability (PPI), and the painful patellar syndrome (PPS). OPI is defined by the observation of at least one patellar dislocation in patients with one or more predisposing factors for patellar instability: excessive patellar height, excessive tibial tuberosity-trochlear groove distance (TT-TG), vastus medialis obliquus (VMO) dysplasia, and trochlear dysplasia. The PPS group is characterized by anterior knee pain, subjective instability, and popping, with no objective evidence of patellar dislocation or predisposing factors. The PPI group is a mix of the previous two groups: symptoms like the painful patellar group with one or more predisposing factors but without evidence of patellar dislocation. This condition may evolve to a true objective instability. Generally, non-operative treatment is suggested as the first-line therapy in patients with PPI and PPS conditions, whereas surgery is indicated in case of OPI. Sometimes in patients with PPI surgery could be indicated in case of failure of conservative treatment. Several studies investigated the anatomy and biomechanics of the medial stabilizers of the patella [2–4]. The medial retinaculum (MR), formed by fibers of the deep transverse layers, consists of a strong fibrous structure formed by important ligaments: the medial patellofemoral ligament (MPFL), the medial patellotibial ligament (MPTL), and the medial patellomeniscal ligament (MPML). These ligaments offer a medial restraint to lateral patellar dislocation. Some authors [5] investigated the contribution of these structures to the patellar stabilization, proving that the role of passive stabilizers is more important than dynamic ones and this condition is more evident in case of patella alta or patellofemoral dysplasia. In patients with PPI or PPS, conservative treatment remains the first option, in absence of important predisposing factors for patellar instability. In these particular patients, in case of failure of the conservative approach for at least 6 months, medial reefing might be considered.