Pediatric Patellar Instability Conservative Management and Outcomes Daniel W. Green , M.D., M.S., F.A.C.S. Hospital for Special Surgery Lindsay Schlichte, M.S.

76 (38.4%) had recurrent instability Natural History Predictors of Recurrent Instability After Acute Patellofemoral Dislocation in Pediatric and Adolescent Patients Lewallen, McIntosh, Dahm AJSM 2013 222 Knees 24 (10.8%) had early surgery 198 treated non-op 76 (38.4%) had recurrent instability 39 (51.3%) required surgical -Age 9-18 -54.1% male -3 year follow up 69% of patients with BOTH immature physes and trochlear dysplasia had recurrence

No difference in sex or BMI Patients involved in sports at the time of initial dislocation were 70% more likely to have a reoccurrence than those not involved in sports No difference in sex or BMI Immature physes and trochlea dysplasia : 3-fold increased risk of recurrent instability vs. Mature physes and trochlea dysplasia 2.5 times more likely to have recurrent instability Lewallen, McIntosh, Dahm AJSM 2013

First-Time Patellofemoral Dislocation: Risk Factors for Recurrent Instability. Lewallen, McIntosh, Dahm J Knee Surgery 2015 Retrospective review of patients with first-time patellofemoral dislocation

No differences in male/female First-Time Patellofemoral Dislocation: Risk Factors for Recurrent Instability. Lewallen, McIntosh, Dahm J Knee Surgery 2015 Recurrent instability more likely with sports related injuries, skeletal immaturity, patella alta and trochlear dysplasia Older age protective No differences in male/female

Predictors of Recurrent Patellar Instability in Children and Adolescents After First-time Dislocation. Jaquith, Parikh J Peds Ortho, 2017 Significant risk factors for recurrence were skeletal immaturity , history of contralateral patellar dislocation, trochlear dysplasia, and a CDI>1.45 Presence of all 4 had a predicted risk of 88% Presence of any 3 had predicted risk of 75% Presence of any 2 had a predicted risk of 55%

Patellar Instability Severity Score Which patellae are likely to redislocate? Balcarek, Oberthür, Hopfensitz et., al Knee Surg Sports Traumatol Arthrosc 2014 61 patients Ages 9-51 (Median 19) All had initial non-op treatment Within 24 months 40 (65.6%) experienced redislocation Identified risk factors for recurrent lateral patellar dislocations to create a Patellar Instability Severity Score

Assessed: “Patellar Instability Severity Score”: Age at primary dislocation Gender Affected side BMI Bilateral instability Physical activity (baecke’s questionnaire) Grade of trochlear dysplasia Patellar height Tibial tuberosity-trochlear groove (TT-TG) distance Patellar tilt “Patellar Instability Severity Score”: Age* Bilateral Instabilty Severity of Trochlear dysplasia* Patella Alta TT-TG Distance Patellar tilt* Total possible score = 7 Odds ratio with regards to patellar redislocation *=significant Which patellae are likely to redislocate? Balcarek, Oberthür, Hopfensitz et., al Knee Surg Sports Traumatol Arthrosc 2014

Scoring Applied to study population: Redislocation group: median = 4 (range 2-7) No redislocation group: median = 3 (range 1-6) Odds Ratio for early episode of patellar redislocation was nearly 5 times higher for the patient who scored 4-7 than for those who scored 1-3 However- still small differences between those who experienced a redislocation and those who did not example: median TT-TG difference: Redislocation: 16 (range 7-27) None: 14 (range 8-24) Balcarek et., al. Which patellae are likely to redislocate? Balcarek, Oberthür, Hopfensitz et., al Knee Surg Sports Traumatol Arthrosc 2014

Primary dislocation Injury Patterns Anatomic patellar instability risk factors in primary lateral patellar dislocations do not predict injury patterns: an MRI-based study. Tompkins, Rohr, Agel, Arendt KSSTA 2017 Prospective study describing injury patterns in 1st time lateral patellar dislocators (LPD) 157 patients (107 skeletally mature) Skeletally immature patients had a greater risk of isolated patellar MPFL and chondral injury. MPFL Injury Location and Severity Osteochondral injury Location and Severity

Trochlear Dysplasia Definitions for presented studies Lewallen et al., 2013: Dejour Classification 4 grade: low grade (type A) high grade (types B-D) Lewallen et al., 2015: Dejour Classification Jaquith et al., 2017: Dejour Classification Balcarek et al., 2014: Dejour Classifcation Tompkins et al., 2017: Trochlear depth <3 mm

Resolution of pain, swelling and inflammation Conservative Treatment First patellar dislocation: from conservative treatment to return to sport Respizzi, Cavallin Stage 1 Resolution of pain, swelling and inflammation Recovery of joint motion and flexibility Recovery of muscle strength Stage 4 Recovery of motor patterns and coordination Stage 5 Recovery of the sport-specific athletic action and return to sporting activity Stage 2 Stage 3

Conservative vs. Surgical Treatment Earlier studies: support surgery for those who fail conservative treatment Buchner, Baudendistel, Sabo et., al. 2005 Nikku, Nietosvaara, Aalto et., al 2004 More recent RCTs highlight the higher rates of recurrent instability in the athletic pediatric population undergoing conservative treatment Nwachakwu, Schairer, Green et., al. 2016 Regalado, Lintula, Kokki et., al. 2016 Bitar, Alexandre Carneiro, et al. 2012

Why waiting for surgery may be detrimental to the patient Trochlea development (Fu, Duan, Liu et.,al. 2018 Bone Joint J) 23 patients, mean age: 9.6 (7-11) all with bilateral recurrent patellar dislocation with femoral trochlea dysplasia Knee with most frequent dislocation or with traumatic dislocation at time of presentation was treated with medial patellar retinacular plasty (Group S) Contralateral knee served as conservative treatment control (Group C) Results: femoral trochlear morphology can be improved by early (before epiphyseal closure) surgical correction in children with recurrent patellar dislocation associated with femoral trochlear dysplasia

Why waiting for surgery may be detrimental to the patient More dislocations = more cartilage injury= more long term pain (even after the instability is surgically corrected) Cartilage status in knees with recurrent patellar instability using magnetic resonance imaging T2 relaxation time value. Chen, Li, Wang et., al. KSSTA 2015 113 patients with patellar instability 50 healthy controls CT and MRI to measure joint anatomy and cartilage status respectively MRI: 32 patients were determined to have cartilage defects Remaining 81: T2 relaxation time value was significantly higher than that of the control group on the middle or medial sites of the patellar cartilage CT: Patellar instability group showed greatly abnormal anatomy of the PF joint compared to controls

Second-look arthroscopy of cartilage changes of the patellofemoral joint, especially the patella, following acute and recurrent patellar dislocation E. Nomura, M. Inoue Osteoarthritis and Cartilage Fig. 8. A 15-year-old girl with RPD. A: She did not have MPFL reconstruction and only arthroscopy examination was performed. Fibrillation on the medial facet and cracking on the central dome were observed. B: Recurrent subluxation and dislocations: MPFL reconstruction was performed 31 months post arthoscopy

Fig. 5. A 14-year-old girl of APD. Second-look arthroscopy of cartilage changes of the patellofemoral joint, especially the patella, following acute and recurrent patellar dislocation E. Nomura, M. Inoue Osteoarthritis and Cartilage Fig. 5. A 14-year-old girl of APD. A: At the first arthroscopy, the right patella was manually dislocated over the lateral femoral condyle and interlaced cracking was seen on the central dome. B: A second-look arthroscopy was performed 20 months after first arthroscopy. Cracking on the central dome was fibrillated.

Recent developments in evaluation and treatment of lateral patellar instability Zimmerer, Sobau, Balcarek Journal of Experimental Orthopedics 2018 15% to 72% of patients treated non-op Patients without reoccurrence often reported not restoring their pre-injury function High risk of patellofemoral arthritis after non-op treatment of lateral patellar dislocations Paradigm shift from conservative to primary op treatment However: reduced re-dislocations not yet reflected in the clinical results Individual clinical decision-making approach, taking each individual risk of re-dislocation into account

Thank You! Daniel W Green, MD greendw@hss.edu Lindsay Schlichte, M.S.

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