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Updated: May 14 2022

Patellar Tendon Rupture

Images
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https://upload.orthobullets.com/topic/3024/images/patella alta lateral xray.jpg
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https://upload.orthobullets.com/topic/3024/images/ap patella alta.jpg
  • Summary
    • A traumatic rupture of the patellar tendon caused by a tension overload during activity in a patient at risk.
    • Diagnosis can be confirmed by physical exam and radiographs for complete tears. Partial tears may need an MRI to confirm the diagnosis.
    • Treatment for complete tears is timely surgical repair to optimize the chance of healing. Partial tears with an intact extensor mechanism may be treated with immobilization.
  • Epidemiology
    • Incidence
      • rare
        • affects < 1 per 100,000 people annually
    • Demographic
      • most commonly in 3rd and 4th decade
      • male > female
    • Anatomic location
      • quadriceps tendon rupture is more common than patella tendon rupture (2:1 ratio)
    • Risk factors
      • may see weakening of collagen structure
        • systemic diseases
          • associated with bilateral ruptures
            • diabetes mellitus
            • systemic lupus erythematous
            • rheumatoid arthritis
            • chronic renal disease
        • local
          • patellar degeneration (most common)
          • previous injury
          • patellar tendinopathy
        • other
          • corticosteroid injection
  • Etiology
    • Pathophysiology
      • mechanism of injury
        • tensile overload of the extensor mechanism
          • sudden quadriceps contraction with knee in a flexed position (e.g., jumping sports, missing step on stairs)
        • most ruptures occur with knee in flexed position
          • greatest forces on tendon when knee flexion > 60 degrees
          • ratio of patellar tendon force to quads tendon force >1 at <45° and <1 at >45°
            • at smaller flexion angle, patellofemoral contact point is at distal pole of patella, giving quads tendon a mechanical advantage
      • pathoanatomy
        • 3 patterns of injury
          • avulsion with or without bone from the proximal insertion/inferior pole of patella (most common)
            • strain at tendon-bone interface is 3-4x strain at midsubstance
          • midsubstance
          • distal avulsion from the tibial tubercle
      • pathobiology
        • rupture is usually the result of end stage or long-standing chronic tendon degeneration
    • Associated conditions
      • orthopedic conditions
        • tibial tubercle avulsion
        • patella fractures
        • TKA extensor mechanism rupture
  • Anatomy
    • Extensor mechanism of the knee
      • quadriceps tendon
      • patella
      • patellar tendon
      • tibial tubercle
    • Blood supply
      • infrapatellar fat pad
      • retinacular structures (medial and lateral inferior geniculate arteries)
    • Biomechanics
      • Forces in patellar tendon
        • ascending stairs is 3x body weight
        • to rupture a normal tendon is 17x body weight
  • Classification
    • Anatomic
      • incomplete tear
        • intact extensor mechanism
        • in some cases can be treated noperatively
      • complete tear
        • patella alta with palpable defect
        • treated with surgical repair
  • Presentation
    • History
      • history of jumping event with sudden quadriceps contraction with knee in a flexed position (e.g., jumping sports, missing step on stairs)
        • patient will often hear/feel a popping sensation
    • Symptoms
      • infrapatellar pain
      • immediate swelling
      • difficulty weight-bearing
    • Physical exam
      • inspection
        • elevation of patella height
        • usually associated with a large hemarthrosis and ecchymosis
        • localized tenderness
        • palpable gap below the inferior pole of the patella
      • motion
        • reduced ROM of knee (and difficulty bearing weight) due to pain
          • if only tendon is ruptured and retinaculum is intact, active extension will be possible but will have extensor lag of a few degrees
      • provocative tests
        • straight leg raise
          • unable to perform active straight leg raise or maintain passively extended knee
  • Imaging
    • Radiographs
      • recommended views
        • AP and lateral of the knee
          • knee in flexion (ideally 30 degrees)
      • optional views
        • merchant or skyline
      • findings
        • patella alta seen in complete rupture
        • various measurements indicating patella alta
          • Insall-Salvati ratio is > 1.2
            • normal between 0.8 and 1.2
          • Blackburne-Peel ratio > 1.0
            • normal between 0.5 and 1.0
          • Caton Deschamps ratio > 1.3
            • normal between 0.6 and 1.3
    • MRI
      • indications
        • differentiate partial from complete tendon rupture
        • most sensitive imaging modality
      • findings
        • site of disruption, tendon degeneration, patellar position, and associated soft tissue injuries
    • Ultrasound
      • indications
        • suspected acute and chronic injuries
      • findings
        • effective at detecting and localizing disruption
        • operator and user-dependent
  • Diagnosis
    • Complete tears
      • can be confirmed by physical exam and radiographs for complete tears. 
    • Partial tears
      • partial tears may need an MRI to confirm the diagnosis.
  • Treatment
    • Nonoperative
      • immobilization in full extension
        • indications
          • partial tears with intact extensor mechanism
        • modalities
          • immobilization
            • hinged knee brace locked in extension for 6 weeks with weight bearing
          • rehabilitation
            • progressive active flexion / passive extension protocol
    • Operative
      • primary repair
        • indications
          • complete patellar tendon ruptures
          • ability to approximate tendon at site of disruption
        • techniques
          • end-to-end repair
          • transosseous tendon repair
          • suture anchor tendon repair
        • rehabilitation
          • locked extension brace with immediate weight bearing for 6 weeks
          • early motion protocol at 7-10 days with focus on passive extension and active flexion
        • outcomes
          • biomechanical studies have shown less gap formation with suture anchor repair compared to transosseous repair
          • clinical studies have shown a significant decrease in re-rupture rate with use of suture anchor compared to transosseous repair.
      • tendon reconstruction
        • indications
          • severely disrupted or degenerative patella tendon
          • chronic tears > 6-8 weeks out from injury
        • techniques
          • ipsilateral semitendinosus or gracilis autograft
          • central quadriceps tendon-patellar bone autograft
          • contralateral bone-patellar tendon-bone autograft or allograft
  • Techniques
    • Nonoperative Treatment - Immobilization
      • protocol similar to post-operative protocol below
    • Direct primary repair
      • approach
        • longitudinal midline incision
        • expose rupture and adjacent retinacula
        • debride the ends of the rupture
        • for subacute tears (> 2 weeks out from injury)
          • quadplasty or scar tissue release to facilitate tendon approximation
      • technique
        • end-to-end technique
          • approximate tendon at site of rupture
          • nonabsorbable sutures are woven with locking stitch
        • transosseous tendon repair
          • suture the patellar tendon to the patella with a #5 non-absorbable transosseous suture
          • drill 2 trans-patellar bony tunnels and pass the sutures through tunnels and tie over the top of patella
          • can be protected with a cerclage wire or nonabsorbable tape between patella and tibial tuberosity
        • suture anchor tendon repair
          • number of anchors debatable
            • most authors advocate for at least 2 anchors
          • higher ultimate load to failure and less gap formation compared to transosseous suture fixation 
      • postoperative rehabilitation
        • weight bearing
          • may weight bear early with protected knee brace locked in extension
          • goal of brace free ambulation by 6 weeks
        • early motion
          • begins at 7-10 days
          • controlled initiation of knee ROM at 7-10 days
          • exercises to optimize range of motion and minimizes stress on the repair include
            • passive extension and active closed chain flexion (heel slides)
            • prone open chain knee flexion
          • goal of brace free ambulation, full knee extension, and 120 degrees of knee flexion by 6 weeks, and
        • return to sport
          • full return to sport at 6 months
    • Tendon reconstruction
      • approach
        • retracted patella may require extensive surgical release
          • quadplasty
          • release of scar tissue
      • technique
        • graft sources
          • autograft
            • ipsilateral gracilis, semitendinous, and quadriceps autografts have all been used
          • allograft tendon or ligament
        • technique
          • free ends of the tendons are passed through transosseous hole of the patella, and then through a transosseous hole within the tibial tubercle to make a complete circle graft
  • Complications
    • Knee stiffness
      • incidence
        • most common complication
      • risk factors
        • delay in surgical treatment
        • delay in initiating post-operative range of motion
      • treatment
        • manipulation under anesthesia (MUA)
          • if flexion is <120° at 6-12 weeks post-op
        • lysis of adhesions
          • if flexion is < 120° after >12 weeks post-op
    • Re-tear
      • incidence
        • ~8% with transosseous direct primary repair
          • 1-2% following suture anchor repair
      • treatment
        • primary repair
          • if acute and adequate tendon quality remains
        • reconstruction
          • chronic lesions
          • poor tendon quality
    • Infection
      • incidence
        • ~2% following surgery
    • Quadriceps atrophy
      • incidence
        • 2nd most common complication
          • does not compromise return of strength
      • treatment
        • physical therapy
  • Prognosis
    • Outcome with treatment
      • excellent outcomes seen with early repair
    • Prognostic variables
      • most important prognostic factor for complete tears is timing of repair
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