Medial patellofemoral ligament injuries and management

Medial patellofemoral ligament injuries

1. MPFL Injuries Samir KC

2. Patellofemoral Joint Osseous diameter of lateral femoral condyle > medial femoral condyle primary constraint to lateral patellar instability when knee flexion is > 30 degrees Ligaments- provides static stability medial patellofemoral ligament (MPFL)   patellotibial ligament retinaculum Muscles dynamic stability of the patella within the trochlear groove vastus medialis  = medial restraint to lateral translation vastus lateralis = lateral restraint to medial translation

3. Extracapsular layer two of the soft tissue layers of the medial aspect of the knee Creates anatomical aponeurosis with VMO and Vastus intermedius keeps the patella centered in the early 30 degrees of knee flexion Wide patellar insertion in the proximal two third of patella/ 28mm Narrow femoral insertion/10mm

4. Mechanism of injury Usually Twisting injury Non Contact Foot planted and an internal rotatory force is applied to the flexed knee in valgus Patella disengaged from the trochlear groove Direct Lateral directed blow External tibial rotation

5. most commonly occurs in 2nd-3rd decades of life Risk factors   ligamentous laxity (Ehlers- Danlos syndrome ) " miserable malalignment syndrome" femoral anteversion genu valgum external tibial torsion / pronated feet patella alta trochlear dysplasia lateral femoral condyle hypoplasia

6. Classification four categories based on location at the level of the MPFL patellar insertion, within the midsubstance of the ligament, at the femoral origin- M/C more than one location. Patellar insertion MPFL type P  with purely ligamentous disruption, type P 1  with a bony avulsion fragment type P 2  with bony avulsion involving the articular surface from the medial facet of the patella

7. Clinical Features Deformity large hemarthrosis   medial sided tenderness (over MPFL) increase in passive patellar translation patellar apprehension increased Q angle J sign  excessive lateral translation in extension which "pops" into groove as the patella engages the trochlea early in flexion

8. Investigations Plain Radiographs CT MRI

9. Investigations

10. Acute Dislocations prompt reduction of the dislocation. usually A&E with some sedation as needed. flexing the hip, applying gentle pressure to the lateral pole of the patella, in a medial direction, while slowly extending the knee . The recurrence rate following a first-time dislocation is around 15-60%.

11. Management M ainstay of treatment for first-time dislocators without evidence of loose bodies or intra-articular damage is conservative, analgesia , icing NSAIDs, activity modification. Bracing in a J brace or a patella stabilizing sleeve for 2 to 4 weeks to allow the soft tissues to heal. Subsequent , physiotherapy quadriceps and vastus medialis oblique strengthening, Hip core strengthening and proprioception.

12. Surgical management can be a consideration in several situations: first time dislocation with osteochondral fracture/loose body MRI demonstrating disruption of MPFL Subluxed patella on Merchant radiograph view with a normal contralateral knee Failure to improve with conservative management with anatomical factors which predispose to dislocation Recurrent dislocations

13. Surgical Management isolated repair/reconstruction of the MPFL Avoid if TT-TG distance greater than 20mm trochlear dysplasia severe patella alta advanced cartilage degeneration

14. MPFL Reconstruction

15. References Campbell’s Operative Orthopaedics Miller’s Review of Orthopaedics Apley’s System of Orthopedics Orthobullets The Medial Patellofemoral Ligament review of literature

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