Types of Patellar Instability PRi SM Patellar Instibialiy

Types of Patellar Instability PRi. SM Patellar Instibialiy RIG Jason Rhodes, MD, MS Alex Tagawa, BA

Purpose/Background • Purpose: Description of Types and Classification of Patellar Instability ▪ No Legitimate Accepted Classification ▪ Etiologies affect treatment and long term outcomes ▪ 2/3 of acute patellar dislocations are in patients less than 20 years of age 2

Types • • • Lateral, Medial, Vertical, Rotational First-time vs Recurrent LPD Congenital Dislocation Developmental Dislocation Habitual Dislocation Permanent Dislocation Chotel, et al. 14

Location of Dislocation • Lateral ▪ Most common ▪ 23. 2 per 100, 000 person years • Age and sex adjusted 3 • Medial ▪ Less Common • Vertical ▪ Superior or inferior to trochlea • Rotational ▪ Axial dislocation

Nomenclature for Lateral Instability Parikh SN, Lykissas MG 17

Recurrence • Primary acute dislocations ▪ 77. 4 (95% CI: 61. 1 -96. 8) per 100, 000 persons per year in males 4 • Recurrence ▪ 22. 7% (95% CI 22. 2 -23. 2) of suffering a recurrent dislocation, with young girls aged 10 -17 experiencing the highest risk 5

Congenital Patellar Dislocation • Rare condition in which the patella is permanently dislocated and cannot be reduced manually 6 • Presents immediately after birth 6 • Flexion contracture of the knee, genu valgus, external tibial torsion and foot deformity 6 • Can be associated with other diagnoses such as arthrogryposis 7

Developmental Patellar Dislocation • Not present at birth but develops after walking age 17 • 40% of immature patients may develop recurrent instability 8, 9 • 10% of these patients may develop contralateral knee patellar instability 8, 10

Habitual Dislocation • Habitual dislocation in knee flexion 8 ▪ At variable angles of flexion 8 ▪ Patella reduces in extension 8 • Habitual dislocation in knee extension 8 ▪ Patella slides over the lateral trochlea when knee reaches almost full extension 8

Permanent Dislocation • After walking age ▪ Distinguished morphologically by normal patellar height and an intact, rounded lateral trochlea and single-facet patella ▪ Antalgic gait common 8

Classification • Classification vs. Types ▪ No official classification • Many different ways to classify ▪ ▪ ▪ Etiology Anatomically Underlying pathologies Age Pathophysiology

Historical/Literature Review • Adult population ▪ Dejour, et al. 11 ▪ Garin, et al. 12 ▪ Sillanpaa 13 • Pediatric Population ▪ ▪ ▪ Chotel, et al. 14 Hiemstra. et al. 15 Frosch and Schmeling 16 Parikh and Lykissas 17 Weeks, et al. (Green)18 Keyes, et al. (Parikh) AJO Summary 1

Dejour, et al. 11 • Anatomic abnormalities and pain • 3 types ▪ Major • More than 1 documented dislocation ▪ Objective • 1 dislocation and anatomic abnormality ▪ Potential • Radiographic abnormalities and patellar pain Jaquith, Parikh 19

Garin, et al. 12 • 2 groups ▪ Major • Permanent or habitual ▪ Recurrent ▪ Reported that soft tissue ligamentous transfer was a successful method for patellar realignment but pending the underlying cause often complementary procedures were needed as well

Sillanpaa 13 • 1 st time • Recurrent • Acute injuries only

Pediatric Dislocations 1 • Historical Classifications ▪ Traumatic ▪ Congenital

Chotel, et al. 14 • 5 categories ▪ Congenital • At birth with a functional genu valgum ▪ Permanent • 1 -5 years of age ▪ Habitual during knee flexion • 5 -8 years of age ▪ Habitual during extension • 5 -8 years of age ▪ Recurrent • Preadolescence or adolescence due to atraumatic event

Chotel, et al. 14

Hiemstra. et al. 15 • WARPS ▪ Weak, atraumatic, risky anatomy, pain and subluxation • Continued instability • Valgus, ligamentous laxity, rotational abnormalities, shallow and short trochlear groove, and patella alta • STAID ▪ Strong, traumatic, anatomy normal, instability and dislocation • No underlying anatomic issues

• Type 1 Frosch and Schmeling 16 ▪ Simple dislocation with no maltracking or instability • Type 2 ▪ High risk of redislocation and no maltracking • Type 3 ▪ 5 subcategories • Contracture, patella alta, pathological tibial tuberosity and TG distance • Type 4 ▪ Highly unstable “floating patella” • Type 5 ▪ Patellar maltracking without instability

Frosch and Schmeling 16

Parikh and Lykissas 17 • Type 1 ▪ First-time dislocation • Type 2 ▪ Recurrent instability • 2 A – positive apprehension • 2 B – instability related to anatomic abnormalities

Parikh SN, Lykissas MG 17

Weeks, et al. 18 (Green) • Traumatic ▪ Acute or recurrent • Obligatory ▪ Flexion or extension • Fixed laterally ▪ Often congenital abnormalities • All can be syndromic ▪ Skeletal dysplasia, Ehlers-Danlos, CP, Marfan disease, nailpatella syndrome, Down Syndrome, Rubenstein-Taybi syndrome, Kabuki syndrome

Keyes, et al. 20181

Patellar Dislocation Types/Classifications • • • No one excepted standard classification Many different patterns of dislocation/instability Many underlying etiologies and pathologies Appropriate to evaluate and address all issues Where do we start?

References 1. 2. 3. 4. 5. 6. 7. 8. 9. Keyes S, Price M, Green DW, Parikh SN, Special considerations for pediatric patellar instability, Am J Orthop (Belle Mead NJ). 2018 Mar; 47(3). doi: 10. 12788/ajo. 2018. 0017 Duthon VB, Acute traumatic patellar dislocation, Orthop Traumatol Surg Res. 2015 Feb; 101(1 Suppl): S 59 -67. doi: 10. 1016/j. otsr. 2014. 12. 001, Epub 2015 Jan 12. Sanders TL, Pareek A, Hewett TE, Stuart MJ, Dahm DL, Krych AJ, Incidence of First-Time Lateral Patellar Dislocation: A 21 -Year Population-Based Study, Sports Health, 2018 Mar/Apr; 10(2): 146151. doi: 10. 1177/1941738117725055. Epub 2017 Aug 10. Sillanpää P, Mattila VM, Iivonen T, Visuri T, Pihlajamäki H, Incidence and risk factors of acute traumatic primary patellar dislocation, Med Sci Sports Exerc. 2008 Apr; 40(4): 606 -11. doi: 10. 1249/MSS. 0 b 013 e 318160740 f. Gravesen KS, Kallemose T, Blønd L, Troelsen A, Barfod K, High incidence of acute and recurrent patellar dislocations: a retrospective nationwide epidemiological study involving 24. 154 primary dislocations, Knee Surg Sports Traumatol Arthrosc, 2018 Apr; 26(4): 1204 -1209. doi: 10. 1007/s 00167 -017 -4594 -7. Epub 2017 Jun 23. Wada A, Fujii T, Takamura K, Yanagida H, Surijamorn P, Congenital dislocation of the patella, J Child Orthop. 2008 Mar; 2(2): 119 -23. doi: 10. 1007/s 11832 -008 -0090 -4. Epub 2008 Mar 4. Eilert RE, Congenital dislocation of the patella, Clin Orthop Relat Res. 2001 Aug; (389): 22 -9. Popkin CA, Bayomy AF, Trupia EP, Chan CM, & Redler LH, (2018). Patellar Instability in the Skeletally Immature, Current Reviews in Musculoskeletal Medicine, 11(2), 172– 181. http: //doi. org/10. 1007/s 12178 -018 -9472 -5 Lewallen LW, Mc. Intosh AL, Dahm DL, Predictors of recurrent instability after acute patellofemoral dislocation in pediatric and adolescent patients, Am J Sports Med, 2013; 41(3): 575– 581. doi: 10. 1177/0363546512472873.

References Continued 10. Sanders TL, Pareek A, Hewett TE, Stuart MJ, Dahm DL, Krych AJ, High rate of recurrent patellar dislocation in skeletally immature patients: a long-term population-based study, Knee Surg Sports Traumatol Arthrosc. 2017. 11. Dejour H, Walch G, Nove-Josserand L, Guier C, Factors of patellar instability: an anatomicradiographic study, Knee Surg Sports Traumatol Arthrosc. 1994; 2(1): 19 -26. 12. Garin C, Chaker M, Dohin B, Kohler R, Permanent, habitual dislocation and recurrent dislocation of the patella in children: surgical management by patellar ligamentous transfer in 50 knees, Rev Chir Orthop Reparatrice Appar Mot. 2007; 93(7): 690 -700. 13. Sillanpaa P, Terminology of patellar dislocation, In: Sillanpaa P, ed. Trauma. Saarbrucken, Germany: Lambert Academic Publishing; 2010: 16 -18. 14. Chotel F, Bérard J, Raux S, Patellar instability in children and adolescents, Orthop Traumatol Surg Res. 2014; 100(suppl 1): 125 -137. doi: 10. 1016/j. otsr. 2013. 06. 014. 15. Hiemstra LA, Kerslake S, Lafave M, Heard SM, Buchko GML, Introduction of a classification system for patients with patellofemoral instability (WARPS and STAID), Knee Surg Sport Traumatol Arthrosc. 2014; 22(11): 2776 -2782, doi: 10. 1007/s 00167 -013 -2477 -0. 16. Frosch KH, Schmeling A, A new classification system of patellar instability and patellar maltracking. Arch Orthop Trauma Surg, 2016; 136(4): 485 -497. doi: 10. 1007/s 00402 -015 -2381 -9. 17. Parikh SN, Lykissas MG, Classification of lateral patellar instability in children and adolescents, Orthop Clin North Am. 2016; 47(1): 145 -152. doi: 10. 1016/j. ocl. 2015. 08. 016. 18. Weeks KD, Fabricant PD, Ladenhauf HN, Green DW, Surgical options for patellar stabilization in the skeletally immature patient, Sports Med Arthrosc Rev. 2012; 20(3): 194 -202. 19. Jaquith BP, Parikh SN, Predictors of Recurrent Patellar Instability in Children and Adolescents After First-time Dislocation, J Pediatr Orthop. 2017 Oct/Nov; 37(7): 484 -490. doi: 10. 1097/BPO. 0000000674.