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Patellar Instability: Diagnosis Management
- 1. Patellar Instability Allison KPerry Bhargavi Maheshwer Steven F DeFroda Journal of Bone And Joint Surgery (Nov 2022 Vol 10 issue 11) Dr Nitin (Junior Resident)
- 2. Introduction Patellar instability isa potentially devastating diagnosis with high recurrence rate upto 71% Return to preinjury level of sport 67% without surgery After index instability episode, patients with a patellar dislocation have nearly 7 fold increased risk of recurrence
- 3. Risk Factors General Factors Ligamentouslaxity Previous traumatic event Miserable Malalignment syndrome Anatomic Factors Patella Alta Trochlear Dysplasia Increased TT TG and TT PCL distance Patellar Dysplasia Excessive patellar tilt Dysplastic VMO Overpull of lateral structures:ITB, vastus lateralis
- 4. Recurrence risk factors YoungerAge Previous contralateral patellar dislocation Skeletal immaturity Lateral patellar tilt Increased TT-TG distance Patella alta Trochlear Dysplasia
- 5. Classification Acute - singleepisode after significant trauma Almost always lateral Recurrent- Repeated occasional dislocation Occurs at interval pf weeks or months Habitual - Patella dislocates every time the knee is flexed (Critical Angle- Angle of flexion at which patella dislocates)
- 6. Patellofemoral Joint Stabilizer Static Shapeof patella Shape of femoral sulcus Joints capsule Retinaculum Ligaments MPFL
- 7. Dynamic Quadriceps Muscle Vastus medialisobliqus During full extension to 30° flexion main stabilizer MPFL Beyond 30° main stabilizer trochlear bony anatomy (Medial patellotibial and medial patellomeniscal ligament serve as secondary stabilizer beyond 45°)
- 8. Examination After an instabilityepisode,lower limb alignment,hypermobility and gait should be assessed Patellar height in seated position: high/low riding patella Dynamic patellar tracking :Positive J sign :Patella move laterally on active knee extension from flexed position. hard/jumping snap - severe Dysplasia Or soft glide - Malalignment
- 9. Q Angle Anglebetween line of action of patella and quadriceps tendon Male >15° Female>20° indicate greater lateral force
- 10. Q angle measuredat 20° flexion •Lateral Subluxation pf patella in full extension can give rise false low value •External tibial torsion in full extension can increase the apparent Q angle
- 11. Factors Increasing QAngle Genu Valgum Excessive femoral anteversiom External tibial torsion .lateral Tibial Tuberosity
- 12. Beighton Score >4 outof 9 indicate ligamentous laxity •passive little finger dorsiflexion >90° •passive thumb opposition to flexor aspect of the wrist • Elbow Hyperextension >10° •knee Hyperextension >10° • Ability to flatten both palms on floor with extended knee and flexed hip
- 13. Patellar Glide test Patellais divided into 4 longitudinal quadrants Patella is displaced medially Medial displacement of one quadrant or less is suggestive of excessive retinaculum tightness If displacement ≥ 3 quadrants- Possible injury to lateral or medial patellar stabilizer
- 14. Patellar Grind test Pressureover patella Displace it medially, laterally, superiorly and inferiorly in the trochlear groove Positive Test: Anterior knee pain with a pathologic condition of Patellpfemoral joint
- 15. Rotational profile ofstaheli Craig Test (Femoral anteversion) normally 10-15° Thigh foot angle (rotational deformity of tibia) >30° Foot progression angle (ntoe gait)
- 16. Fairbanks apprehension test Patellartilt test: knee in 20 degree flexion Inability to raise patella with thumb and finger to the horizontal plane or slightly past indicates excessive lateral retinacular tightness
- 17. Shape of patella Wibergclassification of patellar shape.
- 18. Symptoms Pain around kneeaggregated on walking uphill/downhill or stairs Feeling of insecurity and knee cap giving away Patellar crepitation Knee swelling
- 19. Investigations Xray AP view Xrayknee lateral Xray axial view CT Scan MRI (MRI >CT)
- 20.
- 21. Insall Salvati index Blackburnpeel Ratio Caton Deschampe index
- 22.
- 23. Trochlear Dysplasia Dejour’ Classification(True lateral view) Shape of trochlear Groove
- 24. Crossing Sign The pointat which the line of trochlear floor crosses the anterior contour of lateral femoral condyle As the crossing sign move inferiorly- More assymetrical condyles and more severe trochlear Dysplasia Trochlear Bump >3mm abnormal
- 25. Sulcus Angle >145° and trochlear depth< 4mm - Trochlear Dysplasia Congruence angle > 16° - patellar Subluxation
- 26. CT Scan TT TGDistance (>20 mm is suggest Malalignment)
- 27.
- 29. MRI Useful in assessment ofbony,cartilaginous and ligamentous lesions eg MPFL Associated chondral injuries
- 30. MRI vs CT MRITT-TG values were 4.16 mm less than CT measurement TT-PCL distance can be measured on MRI with excellent reliability TT PCL >24 mm abnormal (Represent true tibial tubercle lateralisation)
- 32. Treatment Aim Decrease swelling andrelieve pain Enhance restraints Painfree ROM Address the Pathoanatomy causing Dislocation
- 33. Acute Dislocation Conservative Immobilization for6 Weeks : Stiffness Immediate mobilization with brace : recurrence Surgery indicated for: 1 osteochondral fractures 2 Loose bodies 3 Athlete with high level activity MPFL reconstruction +VMO Repair A systematic review of meta-analysis comparing nonoperative and operative management found that surgery have lower rate of recurrent dislocation but does not improve functional outcome A recent RCT demonstrated - MPFLR 6.7% instability rates Non operative - 41.9% instability rates
- 34. Recurrent Dislocation Surgery No singleuniversal surgical procedure Choice of surgery depends on Pathological anatomy Patient demand Skeletal maturity
- 35. Lateral release Medial repair MPFLreconstruction Trochleoplasty Proximal realignment procedure Distal realignment procedure (Patellar dislocation recurrence may occur after surgical stabilization 8.4% upto 5 years postop)
- 36. MPFL Reconstruction Autograft/Allograft •Gracils •Semitendinosus •Patellar •Quadriceps Adequately tensioned (Note-MPFL insert between Adductor tubercle and medial epicondyle on femur And some other its fibers insert on quadriceps tendon as in addition to patella)
- 37. Complications of MPFLR Patellarfracture ( Transpatellar bone tunnel - provide greater stability than suture repair but increase risk of iatrogenic fracture and other complication rate) Postoperative instability Flexion loss Pain Overall complication rate 26%
- 38. Tibial tubercle transfer Elmslie-TrillatTechnique (Distal realignment procedure) Lateral Retinacular release Medial capsular reefing Medial transposition of anterior tibial tubercle C/I varus knee, degenerative medial compartment,medial Menisectomy Fulkerson Technique Anteromedialisation technique Decrease contact pressure on lateral and central trochlea and increase on medial trochlea
- 39. Proximal realignment procedure Donein skeletally immature individual Lateral Retinaculum and capsule released Quadriceps tendon split and suture to patella
- 40. Trochleoplasty Indications J sign withTT TG distance >20 mm Dome shaped trochlea Reduces risk of dislocation but does not halt the progression of arthritis
- 41. Summary Presence of apreoperative J sign is predictive of recurrent instability after operative management Nonoperative treatment with patellar bracing and therapy best for primary patellar dislocations Aspiration of effusion acutely allows patient to regain quadriceps strength and control Loose body - arthroscopic removal / fixation +/- medial repair Primary repair indicated when there is extensiveextensive medial side injury, femoral avulsion of MPFL and avulsion of VMO
- 42. In case ofrecurrence treatment should be directed at correcting underlying pathological condition No role of isolated lateral release for patellar instability MPFLR the choice of recurrent instability with or without trochlear Dysplasia with normal TT TG distance and normal patellar height Distal realignment- Choice for increased TT TG distance and patella alta ( standard medialisation of TT- Normal patellar height and trochlear anatomy and increased TT TG Distalisation- added if there is concomitant patella alta Anteromedialisation of TT- Lateral and/or distal patellar facet Chondrosis)