Patella Fractures & Extensor Mechanism InjuriesExtensor Tendon Ruptures • Patellar and quadriceps...
Transcript of Patella Fractures & Extensor Mechanism InjuriesExtensor Tendon Ruptures • Patellar and quadriceps...
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Patella Fractures & Extensor Mechanism Injuries
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Anatomy
• Largest sesamoid bone• Thick articular
cartilage proximally• Articular surface
divided into medial and lateral facets by longitudinal ridge
• Distal pole nonarticular
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Anatomy
• Patellar Retinaculum– Longitudinal tendinous
fibers– Patellofemoral
ligaments
• Blood Supply– Primarily derived from
geniculate arteries
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Biomechanics
• The patella undergoes 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
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Biomechanics
• The patella increases 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
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Biomechanics
• Twice 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
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History
• Direct blow to the anterior knee (dashboard injury)
• Fall from height • Rapid knee flexion
with quadriceps resistance
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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
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Radiographic Evaluation
• AP & Lateral – Patella alta or baja– Note fracture pattern
• Articular step-off, diastasis
• Special views– Axial or sunrise
• CT Scan-Occult fractures
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Radiographic Evaluation
• Bipartite Patella– Obtain bilateral views– Often involves
superolateral corner– Accessory ossification
center
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Etiology• Allows prediction of
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
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Classification
• Allows prediction of treatment
• Types – Transverse– Marginal – Vertical– Comminuted– Osteochondral
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Nonoperative Treatment
• Indicated for 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
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Nonoperative Treatment
• Long leg 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
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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!
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Operative Techniques
• Modified tension band wiring• Lag-screw fixation• Cannulated lag-screw with tension band• Partial patellectomy• Patellectomy
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Modified Tension Band Wiring
• Transverse, noncomminuted fractures
• After reduction, fracture is fixed with two parallel, 1.6mm Kirschner wires placed perpendicular to the fracture
• 18 gauge wire passed behind proximally and distally
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Modified Tension Band Wiring
• 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
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Lag-Screw Fixation
• Indicated for stabilization of comminuted fragments in conjunction with tension band wiring or cerclage wires
• May also be used as an alternative to tension band wiring for transverse or vertical fractures
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Lag-Screw Fixation
• Contraindicated for 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
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Cannulated Lag-Screw With Tension Band
• Fully threaded screws placed with a lag technique
• Wire through screws and across anterior patella in figure of eight tension band
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Cannulated Lag-Screw With Tension Band
• 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
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Suture vs. Wire Tension Band
Gosal et al Injury 2001• Wire v. #5 Ethibond• 37 patients• Reoperation 38% wire
group vs. 6%• Infection 3 pts wire
group vs. 0
Patel et al, Injury 2000McGreal et al, J Med
Eng Tech, 1999• Cadaveric models• Quality and stability
of fixation comparable to wire
• Conclude suture an acceptable alternative
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Partial Patellectomy
• Indicated for 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
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Partial Patellectomy
• Tendon is 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
• Watch for patellar tilt! • 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
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Total Patellectomy
• Indicated for 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
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Postoperative Management
• Immobilization with 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
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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%
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Extensor Tendon Ruptures
• Patellar and quadriceps tendon ruptures are uncommon injuries
• Patients are typically males in their 30’s or 40’s– Patellar < 40 yo– Quadriceps > 40 yo
• Fall, sports, MVA
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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
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Quadriceps Tendon Ruptures
• Risk Factors– Chronic tendonitis – Anabolic steroid use– Local steroid injection– Inflammatory
arthropathy– Chronic renal failure– Systemic disease
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History
• Sensation of a sudden pop while stressing the extensor mechanism
• Pain at the site of injury• Inability/difficulty weightbearing
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Physical Exam
• Effusion • Tenderness at the
upper pole• Palpable defect above
superior pole• Loss of extension• With partial tears,
extension will be intact
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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
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Operative Treatment
• Reapproximation of tendon to bone using nonabsorbable sutures with tears at the muscultendonous junction– Locking stitch (Bunnel, Krakow) with No. 5
ethibond passed through vertical bone tunnels– Repair tendon close to articular surface to avoid
patellar tilting
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Operative Treatment
• Midsubstance tears 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)
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Treatment
• Chronic tears may require a V-Y advancement of a retracted quadriceps tendon (Codivilla V-Y-plasty Technique)
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Postoperative Management
• Knee immobilizer 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
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Complications
• Rerupture• Persistent quadriceps
atrophy/weakness• Loss of motion• Infection
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Patellar Tendon Rupture
• Less common than quadriceps tendon rupture
• Associated with degenerative changes of the tendon
• Rupture often occurs at inferior pole insertion site
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Patellar Tendon Rupture
• Risk Factors– Rheumatoid– Systemic Lupus
Erythematosus– Diabetes– Chronic Renal Failure– Systemic Corticosteroid
Therapy– Local Steroid Injection – Chronic patellar tendonitis
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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
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Blood Supply
• Fat pad 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
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Biomechanics
• Greatest forces are 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
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History
• Often a report of forceful quadriceps contraction against a flexed knee
• May experience and audible “pop”
• Inability to weightbear or extend the knee
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Physical Examination
• Palpable defect• Hemarthrosis • Painful passive knee
flexion• Partial or complete
loss of active extension
• High riding patella on radiographs
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Radiographic Evaluation
• AP and 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
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Classification
• No widely accepted 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
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Treatment
• Surgical treatment is required for restoration of the extensor mechanism
• Repairs categorized as early or delayed
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Early Repair
• Better overall 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
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Early Repair• Frayed edges 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
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Early Repair
• Repair retinaculartears
• May reinforce with wire, cable or umbilical tape
• Assess repair intraoperatively with knee flexion
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Postoperative Management• Maintain hinged knee brace which is gradually increased
as motion increases (tailor to the patient)• 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
• Immediate isometric quadriceps exercises• All restrictions are lifted after full range of motion and
90% of the contralateral quadriceps strength are obtained; usually at 4-6 months
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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
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Postoperative Management
• More conservative 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
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Complications
• Knee stiffness• Persistent quadriceps weakness• Rerupture• Infection • Patella baja