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L07 extensor mechnsm injury
- 1. Injuries to thePatella and Extensor Mechanism Charles G. Haddad, Jr., MD Lisa K. Cannada, MD Emory University Robert Cantu, MD
- 2. Anatomy • Largest sesamoidbone • Thick articular cartilage proximally • Articular surface divided into medial and lateral facets by longitudinal ridge • Distal pole nonarticular
- 3. Anatomy • Patellar Retinaculum –Longitudinal tendinous fibers – Patellofemoral ligaments • Blood Supply – Primarily derived from geniculate arteries
- 4. Biomechanics • The patellaundergoes approximately 7 cm of translation from full flexion to extension • Only 13-38% of the patellar surface is in contact with the femur throughout its range of motion
- 5. Biomechanics • The patellaincreases the moment arm about the knee – Contributes up to 30% increase in force with extension • Patella withstands compressive forces greater than 7X body weight with squatting
- 6. Biomechanics • Twice asmuch torque is needed to extend the knee the final 15 degrees than to extend from a fully flexed position to 15 degrees of flexion
- 7. History • Fall fromheight • Direct blow to the anterior knee (dashboard injury) • Rapid knee flexion with quadriceps resistance
- 8. Physical Examination • Pain,swelling, contusions, lacerations and/or abrasions at the site of injury • Palpable defect • Assessment of ability to extend the knee against gravity or maintain the knee in full extension against gravity
- 9. Radiographic Evaluation • AP,Lateral, and Tangential – Note fracture pattern • Articular step-off, diastasis – Patella alta or baja • CT Scan – Occult fractures
- 10. Radiographic Evaluation • BipartitePatella – Obtain bilateral views – Often involves superolateral corner – Accessory ossification center
- 11. Etiology • Allows predictionof outcome • Direct trauma – Dashboard injury – Increasing cases with penetrating trauma – Often with comminution and articular damage • Indirect trauma – Violent flexion directed through the extensor mechanism against a contracted quadriceps – Results in simple, transverse fractures
- 12. Classification • Allows predictionof treatment • Types – Transverse – Marginal – Vertical – Comminuted – Osteochondral
- 13. Transverse Fractures • 35%are nondisplaced* • If nondisplaced then medial and lateral retinaculum usually intact *Bostrom Acta Orthop Scand Suppl 1972
- 14. Vertical Fractures • Accountfor 22% of patella fractures* • Typically results from compression of patella with flexed knee • Sometimes only seen on sunrise view *Browner et al. Skeletal Trauma 2nd Ed
- 15. Stellate Fractures • Resultfrom direct blow • 65% of stellate fractures are displaced • May have associated articular damage to femoral condyles
- 16. Nonoperative Treatment • Indicatedfor nondisplaced fractures – <2mm of articular stepoff and <3mm of diastasis with an intact extensor mechanism • May also be considered for minimally displaced fractures in the elderly • Patients with a extensive medical comorbidities
- 17. Nonoperative Treatment • Longleg cylinder cast for 4-6 weeks – May consider a knee immobilizer for the elderly • Immediate weightbearing as tolerated • Rehabilitation includes range of motion exercises with gradual quadriceps strengthening
- 18. Operative Treatment • Goals –Preserve extensor function – Restore articular congruency • Preoperative Setup – Tourniquet • Prior to inflation, gently flex the knee • Approach – Longitudinal midline incision recommended – Transverse approach alternative – Consider future surgeries!
- 19. Techniques • Modified tensionband wiring • Lag-screw fixation • Cerclage • Cannulated lag-screw with tension band • Partial patellectomy • Patellectomy
- 20. Modified Tension BandWiring • Transverse, noncomminuted fractures • After reduction, fracture is fixed with two parallel, 2mm Kirschner wires placed perpendicular to the fracture • 18 gauge wire passed behind proximally and distally
- 21. Modified Tension BandWiring • Wire converts anterior distractive forces to compressive forces at the articular surface • Two twists are placed on opposite sides of the wire – Tighten simultaneously to achieve symmetric tension • Repair any retinacular tears
- 22. Lag-Screw Fixation • Indicatedfor stabilization of comminuted fragments in conjunction with tension band wiring • May also be used as an alternative to tension band wiring for transverse or vertical fractures
- 23. Lag-Screw Fixation • Contraindicatedfor extensive comminution and osteopenic bone • Small secondary fractures may be stabilized with 2.7mm or 3.5mm cortical screws • Transverse or vertical fractures require 3.5mm or 4.5mm cortical screws – Retrograde insertion of screws may be technically easier
- 24. Operative Treatment ofPatella Fractures • Stellate pattern may be fixed with cerclage wiring
- 25. Cannulated Lag-Screw with TensionBand • Fully threaded screws placed with a lag technique • Wire through screws and across anterior patella in figure of eight tension band
- 26. Cannulated Lag-Screw with TensionBand • Most stable construct – Screws and tension band wire combination eliminates both possible separation seen at the fracture site with modified tension band and screw failure due to excessive three point bending
- 27. Partial Patellectomy • Indicatedfor fractures involving extensive comminution not amenable to fixation • Larger fragments repaired with screws to preserve maximum cartilage • Smaller fragments excised – Usually involving the distal pole
- 28. Partial Patellectomy • Tendonis attached to fragment with nonabsorbable suture passed through drill holes in the fragment – Drill holes should be near the articular surface to prevent tilting of the tendon and minimize articular step-off • Load sharing wire passed through drill holes in the tibial tubercle and patella may be used to protect the repair and facilitate early range of motion • Watch for patellar tilt!
- 29. Total Patellectomy • Indicatedfor displaced, comminuted fractures not amenable to reconstruction • Bone fragments sharply dissected • Defect may be repaired through a variety of techniques • Usually results in extensor lag and loss of strength
- 30. Postoperative Management • Immobilizationwith knee brace • Immediate WBAT • Early range of motion – Based on intraoperative assessment of repair – Active flexion with passive extension • Quadriceps strengthening – Begun when there is radiographic evidence of healing, usually around 6 weeks
- 31. Complications • Knee Stiffness –Most common complication • Infection – Rare, depends on soft tissue compromise • Loss of Fixation – Hardware failure in up to 20% of cases • Osteoarthritis – May result from articular damage or incongruity • Nonunion < 1% with surgical repair • Painful hardware – Removal required in approximately 15%
- 32. Quadriceps Tendon Rupture •Typically occurs in patients > 40 years old • Usually 0-2 cm above the superior pole • Level often associated with age – Rupture occurs at the bone-tendon junction in majority of patients > 40 years old – Rupture occurs at midsubstance in majority of patients < 40 years old
- 33. Quadriceps Tendon Rupture •Risk Factors – Chronic tendonitis – Anabolic steroid use – Local steroid injection – Diabetes mellitus – Inflammatory arthropathy – Chronic renal failure
- 34. History • Sensation ofa sudden pop while stressing the extensor mechanism • Pain at the site of injury • Inability/difficulty weightbearing
- 35. Physical Exam • Effusion •Tenderness at the upper pole • Palpable defect above superior pole • Loss of extension • With partial tears, extension will be intact
- 36. Physical Exam Quadriceps TendonRupture • Palpable defect proximal to superior pole of patella • If defect present but patient able to extend the knee then the extensor retinaculum is intact • If no active extension, then both tendon and retinaculum completely torn
- 37. Quadriceps Tendon Rupture Radiographic Evaluation •X-ray- AP, Lateral, and Tangential (Sunrise, Merchant) – Distal displacement of the patella • MRI – Useful when diagnosis is unclear Treatment • Nonoperative – Partial tears and strains • Operative – For complete ruptures
- 38. Blumensaat’s Line • Basedon lateral x-ray with knee in 30 degrees of flexion • Lower pole of patella should be at level of line projected anteriorly from intercondylar notch (Blumensaat’s line) • Patella alta may be seen with patellar tendon rupture and patella baja with quadriceps tendon rupture
- 39. Nonoperative Treatment Quadriceps TendonRupture • Reserved for incomplete tears in which active, full knee extension is preserved • Immobilize leg in extension for approximately 4-6 weeks • Progressive physical therapy required to regain strength and motion
- 40. Operative Treatment • Reapproximationof tendon to bone using nonabsorbable sutures – Locking stitch (Bunnel, Krakow) with No. 5 ethibond passed through transverse bone tunnels – Repair tendon close to articular surface to avoid patellar tilting
- 41. Operative Treatment • Midsubstancetears may undergo end-to-end repair after edges are freshened and slightly overlapped – May benefit from reinforcement from distally based partial thickness quadriceps tendon turned down across the repair site (Scuderi Technique)
- 42. Treatment • Chronic tearsmay require a V-Y advancement of a retracted quadriceps tendon (Codivilla V- Y-plasty Technique)
- 43. Postoperative Management • Kneeimmobilizer or cylinder cast for 5-6 weeks • Immediate vs. delayed (3 weeks) weightbearing as tolerated • At 2-3 weeks, hinged knee brace starting with 45 degrees active range of motion with 10-15 degrees of progression each week
- 44. Complications • Rerupture • Persistentquadriceps atrophy/weakness • Loss of motion • Infection
- 45. Patellar Tendon Rupture •Less common than quadriceps tendon rupture • Most often occurs in patients < 40 years old • Associated with degenerative changes of the tendon • Rupture often occurs at inferior pole insertion site
- 46. Patellar Tendon Rupture •Risk Factors – Rheumatoid – Systemic Lupus Erythematosus – Diabetes – Chronic Renal Failure – Systemic Corticosteroid Therapy – Local Steroid Injection – Chronic patellar tendonitis
- 47. Anatomy • Patellar tendon –Averages 4 mm thick but widens to 5-6 mm at the tibial tubercle insertion – Merges with the medial and lateral retinaculum – 90% type I collagen
- 48. Blood Supply • Fatpad vessels supply posterior aspect of tendon via inferior medial and lateral geniculate arteries • Retinacular vessels supply anterior portion of tendon via the inferior medial geniculate and recurrent tibial arteries • Proximal and distal insertion areas are relatively avascular and subsequently are a common site of rupture
- 49. Biomechanics • Greatest forcesare at 60 degrees of flexion • 3-4 times greater strain are at the insertions compared to the midsubstance prior to failure • Forces through the patellar tendon are 3.2 times body weight while climbing stairs
- 50. History • Often areport of forceful quadriceps contraction against a flexed knee • May experience and audible “pop” • Inability to weightbear or extend the knee
- 51. Physical Examination • Palpabledefect • Hemarthrosis • Painful passive knee flexion • Partial or complete loss of active extension • Quadriceps atrophy with chronic injury
- 52. Radiographic Evaluation • APand Lateral X-ray – Patella alta seen on lateral view • Patella superior to Blumensaat’s line • Ultrasonagraphy – Effective means to determine continuity of tendon – Operator and reader dependant • MRI – Effective means to assess patellar tendon, especially if other intraarticular or soft tissue injuries are suspected – Relatively high cost
- 53. Classification • No widelyaccepted means of classification • Can be categorized by: – Location of tear • Proximal insertion most common – Timing between injury and surgery • Most important factor for prognosis • Acute- within two weeks • Chronic- greater than two weeks
- 54. Treatment • Surgical treatmentis required for restoration of the extensor mechanism • Repairs categorized as early or delayed
- 55. Nonoperative Treatment of PatellarTedon Rupture • Nonoperative treatment reserved for partial tears in which patient able to fully extend knee • Treatment is immobilization in full extension for 3-6 weeks
- 56. Early Repair • Betteroverall outcome • Primary repair of the tendon • Surgical approach is through a midline incision – Incise just lateral to tibial tubercle as skin thicker with better blood supply to decrease wound complications • Patellar tendon rupture and retinacular tears are exposed
- 57. Early Repair • Frayededges and hematoma are debrided • With a Bunnell or Krakow stitch, two ethibond sutures or their equivalent are used to repair the tendon to the patella • Sutures passed through three parallel, longitudinal bone tunnels and tied proximally • Repair retinacular tears • May reinforce with wire, cable or umbilical tape • Assess repair intraoperatively with flexion
- 58. Operative Treatment ofPatellar Tendon Rupture • For rupture at osteotendinous junction, tendon reattached to patella with heavy, nonabsorbable sutures passed through drill holes in patella • Medial and lateral retinacula repaired with heavy absorbable suture • Knee immobilized in extension for 6 weeks
- 59. Operative Treatment ofPatellar Tendon Ruptures • 18 gauge wire can be used to reinforce repair • Repair should be tested with flexion of knee in OR and any loose sutures replaced
- 60. Postoperative Management • Hingedknee brace locked at 20 degrees • Immediate isometric quadriceps exercises • Active flexion with passive extension at two weeks; start with 0-45 degrees and advance 30 degrees each week • Active extension at three weeks
- 61. Postoperative Management • Initialtoe-touch weightbearing is gradually advanced to full weightbearing by six weeks • Maintain hinged knee brace which is gradually increased as motion increases • All restrictions are lifted after full range of motion and 90% of the contralateral quadriceps strength are obtained; usually at 4-6 months
- 62. Delayed Repair • >6 weeks from initial injury • Often results in poorer outcome • Quadriceps contraction and patellar migration are encountered • Adhesions between the patella and femur may be present • Options include hamstring and fascia lata autograft augmentation of primary repair or Achilles tendon allograft
- 63. Postoperative Management • Moreconservative when compared to early repair • Bivalved cylinder cast for 6 weeks; may start passive range of motion • Active range of motion is started at 6 weeks
- 64. Complications • Knee stiffness •Persistent quadriceps weakness • Rerupture • Infection • Patella baja Return to Lower Extremity Index