1. 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.

2. 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 % male -3 year follow up
69% of patients with BOTH immature physes and trochlear dysplasia had recurrence

3. 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

4. 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

5. 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

6. 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%

7. 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

8. 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

9. 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

10. 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

11. 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

12. 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

13. 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

14. Why waiting for surgery may be detrimental to the patient
Trochlea development (Fu, Duan, Liu et.,al 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

15. 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

16. 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

17. 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.

18. 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

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

20. Lewallen, L. W. , McIntosh, A. L. , & Dahm, D. L. (2013)
Lewallen, L. W., McIntosh, A. L., & Dahm, D. L. (2013). Predictors of recurrent instability after acute patellofemoral dislocation in pediatric and adolescent patients. The American journal of sports medicine, 41(3),
Lewallen, L., McIntosh, A., & Dahm, D. (2015). First-time patellofemoral dislocation: risk factors for recurrent instability. The journal of knee surgery, 28(04),
Balcarek, P., Oberthür, S., Hopfensitz, S., Frosch, S., Walde, T. A., Wachowski, M. M., ... & Stürmer, K. M. (2014). Which patellae are likely to redislocate?. Knee Surgery, Sports Traumatology, Arthroscopy, 22(10),
Buchner, M., Baudendistel, B., Sabo, D., & Schmitt, H. (2005). Acute traumatic primary patellar dislocation: long-term results comparing conservative and surgical treatment. Clinical Journal of Sport Medicine, 15(2), 62-66
Jaquith, Bradley P., and Shital N. Parikh. "Predictors of recurrent patellar instability in children and adolescents after first-time dislocation." Journal of Pediatric Orthopaedics 37.7 (2017):
Nwachukwu, B. U., So, C., Schairer, W. W., Green, D. W., & Dodwell, E. R. (2016). Surgical versus conservative management of acute patellar dislocation in children and adolescents: a systematic review. Knee Surgery, Sports Traumatology, Arthroscopy, 24(3),
Regalado, G., Lintula, H., Kokki, H., Kröger, H., Väätäinen, U., & Eskelinen, M. (2016). Six-year outcome after non-surgical versus surgical treatment of acute primary patellar dislocation in adolescents: a prospective randomized trial. Knee Surgery, Sports Traumatology, Arthroscopy, 24(1), 6-11.
Fu, K., Duan, G., Liu, C., Niu, J., & Wang, F. (2018). Changes in femoral trochlear morphology following surgical correction of recurrent patellar dislocation associated with trochlear dysplasia in children. Bone Joint J, 100(6),
Chen, X., Wang, W., Xin, H., Wang, Y., & Wang, J. (2015). Cartilage status in knees with recurrent patellar instability using magnetic resonance imaging T2 relaxation time value. Knee Surgery, Sports Traumatology, Arthroscopy, 23(8),
Nomura, E., & Inoue, M. (2005). Second-look arthroscopy of cartilage changes of the patellofemoral joint, especially the patella, following acute and recurrent patellar dislocation. Osteoarthritis and cartilage, 13(11),
Zimmerer, A., Sobau, C., & Balcarek, P. (2018). Recent developments in evaluation and treatment of lateral patellar instability. Journal of experimental orthopaedics, 5(1), 3.
Bitar AC, Demange MK, D’Elia CO, Camanho GL. Traumatic patellar dislocation: nonoperative treatment compared with MPFL reconstruction using patellar tendon. The American journal of sports medicine Jan;40(1):
Tompkins MA, Rohr SR, Agel J, Arendt EA. Anatomic patellar instability risk factors in primary lateral patellar dislocations do not predict injury patterns: an MRI-based study. Knee Surgery, Sports Traumatology, Arthroscopy Mar 1;26(3):