l07 extensor mechnsm injury

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  • Injuries to the Patella and Extensor MechanismCharles G. Haddad, Jr., MDLisa K. Cannada, MDEmory University

    Robert Cantu, MD

  • AnatomyLargest sesamoid boneThick articular cartilage proximallyArticular surface divided into medial and lateral facets by longitudinal ridgeDistal pole nonarticular

  • AnatomyPatellar RetinaculumLongitudinal tendinous fibersPatellofemoral ligamentsBlood SupplyPrimarily derived from geniculate arteries

  • BiomechanicsThe patella undergoes approximately 7 cm of translation from full flexion to extensionOnly 13-38% of the patellar surface is in contact with the femur throughout its range of motion

  • BiomechanicsThe patella increases the moment arm about the kneeContributes up to 30% increase in force with extensionPatella withstands compressive forces greater than 7X body weight with squatting

  • BiomechanicsTwice as much torque is needed to extend the knee the final 15 degrees than to extend from a fully flexed position to 15 degrees of flexion

  • HistoryFall from heightDirect blow to the anterior knee (dashboard injury)Rapid knee flexion with quadriceps resistance

  • Physical Examination Pain, swelling, contusions, lacerations and/or abrasions at the site of injuryPalpable defectAssessment of ability to extend the knee against gravity or maintain the knee in full extension against gravity

  • Radiographic EvaluationAP, Lateral, and Tangential Note fracture patternArticular step-off, diastasisPatella alta or bajaCT ScanOccult fractures

  • Radiographic EvaluationBipartite PatellaObtain bilateral viewsOften involves superolateral cornerAccessory ossification center

  • EtiologyAllows prediction of outcomeDirect traumaDashboard injuryIncreasing cases with penetrating traumaOften with comminution and articular damageIndirect traumaViolent flexion directed through the extensor mechanism against a contracted quadricepsResults in simple, transverse fractures

  • ClassificationAllows prediction of treatment Types TransverseMarginal VerticalComminutedOsteochondral

    Based on mechanism-OTA-predicts outcomeErase types and pull back each bullet?Picture of classification

  • Transverse Fractures35% are nondisplaced*

    If nondisplaced then medial and lateral retinaculum usually intact

    *Bostrom Acta Orthop Scand Suppl 1972

  • Vertical Fractures

    Account for 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

  • Stellate FracturesResult from direct blow

    65% of stellate fractures are displaced

    May have associated articular damage to femoral condyles

  • Nonoperative TreatmentIndicated for nondisplaced fractures
  • Nonoperative TreatmentLong leg cylinder cast for 4-6 weeksMay consider a knee immobilizer for the elderlyImmediate weightbearing as toleratedRehabilitation includes range of motion exercises with gradual quadriceps strengthening

    May add slide referencing JAAOS ref #1, 90% good-excellent results, 1% poor resultsOTA manual protected ROM 0-45 X 4 weeks???

  • Operative TreatmentGoalsPreserve extensor functionRestore articular congruencyPreoperative SetupTourniquet Prior to inflation, gently flex the knee ApproachLongitudinal midline incision recommendedTransverse approach alternativeConsider future surgeries!

  • TechniquesModified tension band wiringLag-screw fixationCerclageCannulated lag-screw with tension bandPartial patellectomyPatellectomy

    OK to change title??

  • Modified Tension Band WiringTransverse, noncomminuted fracturesAfter reduction, fracture is fixed with two parallel, 2mm Kirschner wires placed perpendicular to the fracture 18 gauge wire passed behind proximally and distally

  • Modified Tension Band WiringWire converts anterior distractive forces to compressive forces at the articular surfaceTwo twists are placed on opposite sides of the wireTighten simultaneously to achieve symmetric tensionRepair any retinacular tears

  • Lag-Screw FixationIndicated for 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

  • Lag-Screw FixationContraindicated for extensive comminution and osteopenic boneSmall secondary fractures may be stabilized with 2.7mm or 3.5mm cortical screwsTransverse or vertical fractures require 3.5mm or 4.5mm cortical screwsRetrograde insertion of screws may be technically easier

  • Operative Treatment of Patella Fractures

    Stellate pattern may be fixed with cerclage wiring

  • Cannulated Lag-Screw with Tension BandFully threaded screws placed with a lag techniqueWire through screws and across anterior patella in figure of eight tension band

  • Cannulated Lag-Screw with Tension BandMost 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

  • Partial PatellectomyIndicated for fractures involving extensive comminution not amenable to fixationLarger fragments repaired with screws to preserve maximum cartilageSmaller fragments excisedUsually involving the distal pole

  • Partial PatellectomyTendon is attached to fragment with nonabsorbable suture passed through drill holes in the fragmentDrill holes should be near the articular surface to prevent tilting of the tendon and minimize articular step-offLoad sharing wire passed through drill holes in the tibial tubercle and patella may be used to protect the repair and facilitate early range of motionWatch for patellar tilt!

  • Total PatellectomyIndicated for displaced, comminuted fractures not amenable to reconstructionBone fragments sharply dissectedDefect may be repaired through a variety of techniquesUsually results in extensor lag and loss of strength

  • Postoperative ManagementImmobilization with knee braceImmediate WBATEarly range of motionBased on intraoperative assessment of repairActive flexion with passive extensionQuadriceps strengtheningBegun when there is radiographic evidence of healing, usually around 6 weeks

  • ComplicationsKnee StiffnessMost common complication InfectionRare, depends on soft tissue compromiseLoss of FixationHardware failure in up to 20% of cases

    OsteoarthritisMay result from articular damage or incongruityNonunion < 1% with surgical repairPainful hardwareRemoval required in approximately 15%

  • Quadriceps Tendon RuptureTypically occurs in patients > 40 years oldUsually 0-2 cm above the superior poleLevel often associated with ageRupture occurs at the bone-tendon junction in majority of patients > 40 years oldRupture occurs at midsubstance in majority of patients < 40 years old

  • Quadriceps Tendon RuptureRisk FactorsChronic tendonitis Anabolic steroid useLocal steroid injectionDiabetes mellitusInflammatory arthropathyChronic renal failure

  • HistorySensation of a sudden pop while stressing the extensor mechanismPain at the site of injuryInability/difficulty weightbearing

  • Physical ExamEffusion Tenderness at the upper polePalpable defect above superior poleLoss of extensionWith partial tears, extension will be intact

  • Physical Exam Quadriceps Tendon RupturePalpable 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

  • Quadriceps Tendon RuptureRadiographic EvaluationX-ray- AP, Lateral, and Tangential (Sunrise, Merchant)Distal displacement of the patellaMRIUseful when diagnosis is unclear

    TreatmentNonoperativePartial tears and strainsOperativeFor complete ruptures

  • Blumensaats LineBased on lateral x-ray with knee in 30 degrees of flexionLower pole of patella should be at level of line projected anteriorly from intercondylar notch (Blumensaats line)Patella alta may be seen with patellar tendon rupture and patella baja with quadriceps tendon rupture

  • Nonoperative Treatment Quadriceps Tendon Rupture

    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

  • Operative TreatmentReapproximation of tendon to bone using nonabsorbable suturesLocking stitch (Bunnel, Krakow) with No. 5 ethibond passed through transverse bone tunnelsRepair tendon close to articular surface to avoid patellar tilting

  • Operative TreatmentMidsubstance tears may undergo end-to-end repair after edges are freshened and slightly overlappedMay benefit from reinforcement from distally based partial thickness quadriceps tendon turned down across the repair site (Scuderi Technique)

  • TreatmentChronic tears may require a V-Y advancement of a retracted quadriceps tendon (Codivilla V-Y-plasty Technique)

  • Postoperative ManagementKnee immobilizer or cylinder cast for 5-6 weeksImmediate vs. delayed (3 weeks) weightbearing as toleratedAt 2-3 weeks, hinged knee brace starting with 45 degrees active range of motion with 10-15 degrees of progression each week

  • ComplicationsRerupturePersistent quadriceps atrophy/weaknessLoss of motionInfection

  • Patellar Tendon RuptureLess common than quadriceps tendon ruptureMost often occurs in patients < 40 years oldAssociated with degenerative changes of the tendonRuptu