Patella Fractures & Extensor Mechanism Injuries

Lisa K. Cannada, MDRevised: October 2008; May 2011

Anatomy

• Largest sesamoid bone• Thick articular

cartilage proximally• Articular surface

divided into medial and lateral facets by longitudinal ridge

• Distal pole nonarticular

Anatomy

• Patellar Retinaculum– Longitudinal tendinous

fibers

– Patellofemoral ligaments

• Blood Supply– Primarily derived from

geniculate arteries

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

Biomechanics

• The patella increases the moment arm about the knee– Contributes up to 30%

improvement in lever arm

• Patella withstands compressive forces greater than 7X body weight with squatting

Biomechanics

• 2 X Torque:– Extend final 15°

– Than to extend from a fully flexed position to 15 degrees of flexion

Physical Examination

• Pain, swelling, contusions, lacerations and/or abrasions at the site of injury– Can determine timing of operative intervention

• Palpable defect

• Assessment of ability to extend the knee – Cannot perform a straight leg raise with no

extensor lag

Radiographic Evaluation• AP & Lateral

– Note patella height (baja or alta)

– Note fracture pattern• Articular step-off, diastasis

• Marginal impaction

• Special views– Axial or sunrise

• CT Scan- Occult Fractures

- Complex or Marginal Impaction Fractures

Radiographic Evaluation

• Bipartite Patella:• Don’t get fooled!

– Obtain bilateral views

– Often superolateral corner

(Saupe Classification, 1923)

– Accessory ossification center

– Occurs 1-2% of patients

Etiology

• Direct trauma– Direct blow to flexed knee (dashboard)– Increasing cases with penetrating trauma– Comminution & articular marginal impaction

• Indirect trauma– Flexion force directed through the extensor

mechanism against a contracted quadriceps– Simple, transverse fracture

Classification• Allows guidance with

treatment • Types

– Transverse

– Marginal

– Vertical

– Comminuted

– Osteochondral

– Avulsion (not pictured)

Tip: Vertical fractures may not result in disruption of extensor mechanism

OA/OTA Classification

Nonoperative Treatment

• Indicated for minimally or nondisplaced fractures– < 2mm of articular step-off & < 3mm of diastasis with an

intact extensor mechanism (extensor retinaculum)

– If difficulty assessing, consider intra-articular injection of local anesthetic to better assess ability to extend

• Consider for minimally displaced fractures in low demand patients (evaluate comorbidities & function)

• Patients with a extensive medical comorbidities

Nonoperative Treatment

• Long leg cylinder cast for 4-6 weeks– May consider a knee immobilizer or hinged

knee brace for the elderly/low demand

• Immediate weight-bearing as tolerated

• Rehabilitation includes range of motion exercises with gradual quadriceps strengthening

• Protect eccentric contraction 3 months

Operative Treatment• Goals

– Preserve extensor function– Restore articular congruency

• Preoperative Setup– Tourniquet (debatable)

• Prior to inflation, gently flex the knee

• Approach– Longitudinal midline incision

recommended– Transverse approach alternative (dotted

lines) – potentially higher risk wound problems, can limit initiation of ROM

– Consider future surgeries!

Procedure

Longitudinal Incision

Clean Fracture Site

Torn Retinaculum

Longitudinal Incision

Clean Fracture Site

Torn Retinaculum

ProcedureReduce & Compress Fracture

Operative Techniques

• K-wires w/ tension band wiring (TBW)

• Lag-screw fixation

• Cannulated lag-screw with TBW (tension band screw – TBS)

• Partial patellectomy

• Total Patellectomy

Tension Band Wiring• Transverse, non-comminuted

fractures

• Reduce and clamp, then place two parallel 1.6mm K- wires placed perpendicular to the fracture

• 18 gauge wire passed behind proximally and distally

• Double Figure-8 wire for equal compression

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

• Retinacular Injury– Keep open until the end

– Window to assess articular reduction

– Repair the retinacular injury last

Lag-Screw Fixation

• Indicated for stabilization of comminuted fragments in conjunction w/ cerclage wires if necessary

• May also be used as an alternative/adjunct to TBW for transverse or vertical fractures

Example

Example

Lag-Screw Fixation

• Contraindicated for extensive comminution and osteopenic bone

• Small secondary fractures may be stabilized with 2.0mm, 2.7mm or 3.5mm cortical screws

• Reduce out of plane fragments to main fragments superiorly and inferiorly

• Transverse or vertical fractures require 3.5mm, 4.0mm, or 4.5mm cortical screws– Retrograde insertion of screws may be technically

easier

Cannulated Lag-Screw With Tension Band (TBS)

• Partially threaded cannulated screws (4.0mm)

• Wire through screws and across anterior patella in figure of eight tension band

• Make sure tip of screw remains buried in bone so it will not compromise wire

Cannulated Lag-Screw With Tension Band

• More stable construct – Screws and tension band wire combination

eliminates both possible separation seen at the fracture site with K wire/TBW and screw failure due to excessive three point bending

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

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

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 patella

• 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

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 (30°) and loss of strength (30%) – H Kaufer, JBJS

Postoperative Management

• Immobilization with knee brace, WBAT in extension• Early range of motion

– Based on intraoperative assessment of repair & bone quality– Active flexion with passive extension

• Quadriceps strengthening– Begin when there is radiographic evidence of healing,

usually around 6 weeks• Modify depending upon fracture, osteoporosis,

comorbidities, tenuous fixation and/or wounds at risk

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%

Nonunion

Loss of Fixation

Malunion

Extensor Tendon Ruptures

• Patients are typically males in their 30’s or 40’s– Patellar < 40 yo

– Quadriceps > 40 yo

• Mechanism– Fall

– Sports “The weekend warrior”

– MVA

– Tendonopathies, Steroids, Renal Dialysis

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

Quadriceps Tendon Ruptures

• Risk Factors– Chronic tendonitis

– Anabolic steroid use

– Local steroid injection

– Inflammatory arthropathy

– Chronic renal failure

– Systemic disease

History

• Sensation of a sudden pop while stressing the extensor mechanism (eccentric load)

• Pain at the site of injury

• Inability to extend the knee

• Difficulty weight-bearing

Physical Exam

• Effusion • Tenderness at the

upper pole• Palpable defect above

superior pole• Loss of extension• With partial tears,

extension will be intact

Quadriceps Tendon Rupture

Radiographic Evaluation• X-ray- AP, Lateral, and

Tangential (Sunrise, Merchant)– Distal displacement of

the patella (patella baja)

• MRI– Useful when diagnosis

is unclear

Treatment• Nonoperative

– Partial tears and strains

• Operative– For complete ruptures

Operative Treatment

• Reapproximation of tendon to bone using nonabsorbable sutures with tears at the muscle-tendon junction– Locking stitch (Bunnel, Krakow) with No. 5

ethibond passed through vertical bone tunnels– Repair tendon close to articular surface to avoid

abnormal patellar tilting

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)

Treatment

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

Postoperative Management

• Knee immobilizer, Hinged Knee Brace, or cylinder cast for 5-6 weeks

• Immediate weight-bearing 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

Complications

• Rerupture• Persistent quadriceps

atrophy/weakness• Loss of motion• Infection

Patellar Tendon Rupture

• Less common than quadriceps tendon rupture

• Associated with degenerative changes of the tendon

• Rupture often occurs at inferior pole insertion site

Patellar Tendon Rupture

• Risk Factors– Rheumatoid arthritis– Systemic Lupus

Erythematosus– Diabetes– Chronic Renal Failure– Systemic

Corticosteroid Therapy– Local Steroid Injection – Chronic tendonitis

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

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

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

History

• Often a report of forceful quadriceps contraction against a flexed knee

• May experience and audible “pop”

• Inability to weightbear or extend the knee

Physical Examination

• Palpable defect• Hemarthrosis • Painful passive knee

flexion• Partial or complete

loss of active extension

• High riding patella on radiographs (patella alta)

Radiographic Evaluation

• AP and Lateral X-ray– Patella alta seen on lateral view

• Patella superior to Blumensaat’s line

• Ultrasonagraphy– Effective means to confirm diagnosis by determining

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

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: < 2 weeks

• Chronic: > 2 weeks

Treatment

• Surgical treatment is required for restoration of the extensor mechanism

• Repairs categorized as early or delayed

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 & retinacular tears are exposed• Frayed edges and hematoma are debrided

Early Repair

• With a Bunnell or Krakow stitch, two ethibond sutures or their equivalent are used to repair the tendon to the patella

• Drill holes in patella in mid-sagittal plane to prevent cut out of suture

• Sutures passed through three parallel, longitudinal bone tunnels and tied proximally

Early Repair

• Repair retinacular tears• May reinforce with wire,

cable or umbilical tape• Assess repair

intraoperatively with knee flexion

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

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

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

Complications

• Knee stiffness

• Persistent extensor weakness

• Rerupture

• Infection

• Patella baja (Insall-Salvati ratio of < 0.8)

References Patella Fractures: New

• Hughes SC, Stott PM, Hearnden AJ, Ripley LG: A new and effective tension band braided polyester suture technique for transverse patellar fracture fixation. Injury 2007:38:212-222.

• Luna-Pizarro D, Amato D, Arellano F, Hernandez A, Lopez-Rojas P: Comparison of a technique using a new percutaneous osteosynthesis device with conventional open surgery for displaced patella fractures in a randomized controlled trial. J Orthop Trauma 2006; 20:529-535.

References Patella Fractures: Classic

• Carpenter JE, Kasman R. Matthews LS: Fractures of the patella. Instr Course Lect 1994: 43:97-108.

• Burvant JG, Thomas KA, Alexander R, Harris MB. Evaluation of methods of internal fixation of transverse patella fractures: A biomechanical study. J Orthop Trauma 1994;8:147-153.

• Einola S, Aho AJ, Kallio P. Patellectomy after fracture: long term follow-up results with special reference to functional disability. Acta Orthop Scand 1976:47:441-447.

References:Extensor Mechanism Injuries

• Siwek CW, Rao JP. Ruptures of the extensor mechanism of the knee joint. J Bone Joint Surg Am 1981; 63:932-937.

• Bhargava SP, Hynes MC, Dowell JK. Traumatic patella tendon rupture: early mobilization following surgical repair. Injury 2004;35:76-79.

• Konrath GA, Chen D, Lock T et al. Outcomes following repair of quadriceps tendon ruptures. J Orthop Trauma 1998;12:273-279.

Thank You!Thank You!

lcannada@slu.edu

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