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Patella Fractures & Extensor Mechanism Injuries Lisa K. Cannada, MD Revised: October 2008; May 2011.

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Presentation on theme: "Patella Fractures & Extensor Mechanism Injuries Lisa K. Cannada, MD Revised: October 2008; May 2011."— Presentation transcript:

1 Patella Fractures & Extensor Mechanism Injuries Lisa K. Cannada, MD Revised: October 2008; May 2011

2 Anatomy Largest sesamoid bone Thick articular cartilage proximally Articular surface divided into medial and lateral facets by longitudinal ridge Distal pole nonarticular

3 Anatomy Patellar Retinaculum –Longitudinal tendinous fibers –Patellofemoral ligaments Blood Supply –Primarily derived from geniculate arteries

4 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

5 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

6 Biomechanics 2 X Torque: –Extend final 15° –Than to extend from a fully flexed position to 15 degrees of flexion

7 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

8 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

9 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

10 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

11 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

12 OA/OTA Classification

13 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

14 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

15 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!

16 Procedure Longitudinal Incision Clean Fracture Site Torn Retinaculum Longitudinal Incision Clean Fracture Site Torn Retinaculum

17 Procedure Reduce & Compress Fracture

18 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

19 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

20 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

21 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

22 Example


24 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

25 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

26 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

27 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 McGreal et al, J Med Eng Tech, 1999 Cadaveric models Quality and stability of fixation comparable to wire Conclude suture an acceptable alternative

28 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

29 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

30 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

31 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

32 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%

33 Nonunion

34 Loss of Fixation

35 Malunion

36 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

37 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

38 Quadriceps Tendon Ruptures Risk Factors –Chronic tendonitis –Anabolic steroid use –Local steroid injection –Inflammatory arthropathy –Chronic renal failure –Systemic disease

39 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

40 Physical Exam Effusion Tenderness at the upper pole Palpable defect above superior pole Loss of extension With partial tears, extension will be intact

41 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

42 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

43 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)

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

45 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

46 Complications Rerupture Persistent quadriceps atrophy/weakness Loss of motion Infection

47 Patellar Tendon Rupture Less common than quadriceps tendon rupture Associated with degenerative changes of the tendon Rupture often occurs at inferior pole insertion site

48 Patellar Tendon Rupture Risk Factors –Rheumatoid arthritis –Systemic Lupus Erythematosus –Diabetes –Chronic Renal Failure –Systemic Corticosteroid Therapy –Local Steroid Injection –Chronic tendonitis

49 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

50 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

51 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

52 History Often a report of forceful quadriceps contraction against a flexed knee May experience and audible “pop” Inability to weightbear or extend the knee

53 Physical Examination Palpable defect Hemarthrosis Painful passive knee flexion Partial or complete loss of active extension High riding patella on radiographs (patella alta)

54 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

55 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

56 Treatment Surgical treatment is required for restoration of the extensor mechanism Repairs categorized as early or delayed

57 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

58 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

59 Early Repair Repair retinacular tears May reinforce with wire, cable or umbilical tape Assess repair intraoperatively with knee flexion

60 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

61 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

62 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

63 Complications Knee stiffness Persistent extensor weakness Rerupture Infection Patella baja (Insall-Salvati ratio of < 0.8)

64 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.

65 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.

66 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.

67 Thank You! Return to Lower Extremity Index E-mail OTA about Questions/Comments 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

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