Systematic Review Treating Patella Instability in Skeletally Immature Patients Patrick Vavken, M.D., M.Sc., Matthias D. Wimmer, M.D., Carlo Camathias, M.D., Julia Quidde, M.D., Victor Valderrabano, M.D., Ph.D., and Geert Pagenstert, M.D. Purpose: The purpose of this study was to comprehensively and systematically review the current evidence for ortho- paedic treatment of immature and adolescent patients with acute and chronic patellar instability. Methods: We searched the online databases PubMed, CINAHL, EMBASE, Cochrane Central Register of Controlled Trials, and Cochrane Database of Systematic Reviews for relevant publications on patellar instability. All dates and languages were included. Results: Twenty articles reporting on a total of 456 knees in 425 patients (131 male patients, 294 female patients) followed-up for 56.7  42.2 months on average were included in the analysis. Two studies focused specifically on conservative versus surgical treatment in acute dislocations and reported no difference in outcomes after 7 and 14 years, even in the face of slight trochlear dysplasia. For recurrent instability, we found consistent beneficial effects from surgical stabilization on clinical scores, postoperative stability, and radiographic assessment. There is no evidence for growth disturbance with surgical patellar stabilization in immature patients. Conclusions: The current best evidence does not support the superiority of surgical intervention over conservative treatment in an acute patellar dislocation. However, anatomic variations and their effect on healing should be considered and included in decision making. In recurrent patellar instability in pediatric and adolescent patients with normal or restored knee anatomy, reconstruction of the medial patellofemoral ligament (MPFL) is the most effective treatment option and can be done safely, together with extensor realignment as needed. Level of Evidence: Level IV, systematic review of mixed-level studies. P atellofemoral problems are considered to be among the most frequent causes of knee pain in young and adolescent patients. However, the use of termi- nology such as “patellofemoral problem” or “anterior knee pain” shows the elusiveness of the underlying problems and the lack of clear-cut diagnostic criteria. Although anterior patellofemoral pain can be caused by a number of pathologic entities, such as patellar hypercompression and chondromalacia, this study focuses on patellar instability, both acute and recurrent, and the evidence concerning its management in pedi- atric and adolescent patients. The discussion of treatment options in patellar insta- bility in skeletally immature patients is overshadowed by concerns of damage to physes and subsequent growth disturbances. 1 Similar concerns have also materialized as barriers to the development of other musculoskeletal procedures in skeletally immature patients, (e.g., in the management of anterior cruciate ligament injuries) but have been found to be largely unsubstantiated. 2 Treatment is chosen analogously to that in adult patients. Acute dislocations are typically treated with conservative treatment unless there is evidence of osteochondral damage. The latter are treated surgically as are recurrent dislocations. 3-5 However, it is prudent to assess the knee anatomy in acute dislocations and differentiate between those with normal anatomic features and those with underlying anatomic abnor- malities, as suggested by DeJour et al. 6 In the latter, anatomic deficiencies should be considered equivalent to osteochondral damage, and early surgical interven- tion might be chosen to counter lateral forces that might interfere with healing, particularly of the medial patellofemoral ligament (MPFL). This systematic review had 3 objectives: (1) to comprehensively and systematically review the current From the Departments of Orthopaedic Surgery, University Hospital Basel (P.V., M.D.W., J.Q., V.V., G.P.) and University Childrens Hospital Basel (C.C.), Basel, Switzerland; University of Bonn Medical School (M.D.W.), Bonn, Germany; Children’s Hospital Boston, Harvard Medical School (P.V.), and the Harvard Center for Population and Development Studies, Harvard School of Public Health (P.V), Boston, Massachusetts, U.S.A. Drs. Vavken and Wimmer contributed equally to this work. The authors report that they have no conflicts of interest in the authorship and publication of this article. Received December 28, 2012; accepted March 11, 2013. Address correspondence to Patrick Vavken, M.D., M.Sc., Department of Orthopaedic Surgery, Boston Children’s Hospital, 300 Longwood Ave, Enders 260, Boston, MA 02115, U.S.A. E-mail: patrick.vavken@childrens.harvard. edu Ó 2013 by the Arthroscopy Association of North America 0749-8063/134/$36.00 http://dx.doi.org/10.1016/j.arthro.2013.03.075 1410 Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 29, No 8 (August), 2013: pp 1410-1422