Patella Fractures Extensor Mechanism Injuries Lisa K Cannada

Patella Fractures & Extensor Mechanism Injuries Lisa K. Cannada, MD Revised: 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 7 X 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 – < 2 mm of articular step-off & < 3 mm 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

Procedure Reduce & 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. 6 mm 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. 0 mm, 2. 7 mm or 3. 5 mm cortical screws • Reduce out of plane fragments to main fragments superiorly and inferiorly • Transverse or vertical fractures require 3. 5 mm, 4. 0 mm, or 4. 5 mm cortical screws – Retrograde insertion of screws may be technically easier

Cannulated Lag-Screw With Tension Band (TBS) • Partially threaded cannulated screws (4. 0 mm) • 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 2000 Mc. Greal 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 midsagittal plane to prevent cut 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! lcannada@slu. edu If you would like to volunteer as an author for the Resident Slide Project or recommend updates to any of the following slides, please send an e-mail to ota@ota. org E-mail OTA about Questions/Comments Return to Lower Extremity Index