7/20/14. Patella Instability. Alignment. PF contact areas. Tissue Restraints. Pain. Acute Blunt force trauma Disorders of the Patellafemoral Joint

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1 Patella Instability Acute Blunt force trauma Disorders of the Patellafemoral Joint Evan G. Meeks, M.D. Orthopaedic Surgery Sports Medicine The University of Texas - Houston Pivoting action Large effusion Pain Manual reduction Chronic Hyperextension Minimal force No effusion ±pain PF contact areas Alignment In full extension, the patella rests proximal to the trochlea Natural valgus alignment of extensor mechanism At 30 flexion patella engages the trochlea Creates contact stresses between trochlea and patella chondral surfaces As flexion angle increases, contact area moves proximal on patella and distal on trochlea Lateral force vector on patella Q-angle traced from anterior iliac spine to patella, then patella to tibial tubercle Higher in women Tissue Restraints Pain Complete control of patella from 0-20 of flexion Anterior, diffuse, not well localized Lateral side linked by lateral retinaculum to iliotibial band MPFL 50%-60% of medial restraint to lateral patella subluxation Referred mostly to medial, but sometimes lateral, retinaculum Bar below patella Posterior in setting of effusion Worse when overloading the PF joint Descending>Ascending stairs Squatting, jumping, quad contraction Prolonged sitting with knees flexed 1

2 Instability Observe High energy activity High Q-angle Patella loses contact with trochlea Capsule or ligament rupture Effusion, hemarthrosis Low energy activity Walking or ascending/ descending stairs Quadriceps inhibition (reflex) due to pain No loss of articulation ± effusion normal Femoral anteversion Squinting patellae Tibial torsion ER in setting of increased femoral anteversion VMO appearance J sign Tracking of patella in flexion and extension Palpation Tests Quad tendon Glide test Patella tendon Medial retinaculum MPFL Lateral retinaculum Medial and lateral displacement of the patella in full extension and at 30 Divide patella into 4 quadrants Less than 1 quadrant and more than 3 quadrants is abnormal Medial/Lateral facets Evaluate the competence of the MPFL Compression Compare R/L Tilt test Medial and lateral margins should be in the same horizontal plane Tilt greater than 10 is abnormal Evaluate lateral and medial structures for flexibility or contracture Apprehension test With the knee in full extension, apply controlled, laterally directed force on the patella Fear of dislocation by patient Apply bilaterally DO NOT use in acute dislocation 2

3 First time dislocation Conservative management Pain control Decrease swelling Increase ROM Quadriceps strengthening Some propose immobilization Bracing Lateral buttress Prevent lateral subluxation Compression McConnell taping Prevent lateral subluxation Better tolerated at times Stiffness Surgical fixation of MPFL Conflicting results Chronic Dislocations Osteochondral fracture Medial patella Lateral trochlea Indication for operative fixation Surgical fixation indicated Must address bony AND soft tissue problems Not one procedure fits all patients Soft tissue procedures Lateral release Arthroscopic or open Poor results alone MUST HAVE LATERAL RETINACULUM TIGHTNESS - + tilt test Contraindicated for any other reason VMO advancement = proximal realignment Help correct lateral patellar tilt and subluxation In combination with other procedures MPFL reconstruction Effective and works alone in cases of mild instability Check reign to lateral displacement Proper tensioning allows flexion without overconstraining No dislocation in full extension 3

4 Bony procedures Tibial tubercle transfer Medial/Anteromedialization Corrects high Q angle or TT-TG distance Decreases lateral force on patella Must watch for overloading medial patella facet and trochlea Maquet Angle of osteotomy has large effect on amount of anterior or medial tilt 4

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