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Patella Fractures

Definition

  • Caused from direct blow, fall on flexed knee
  • the patella height adds, by lever arm an ↑ in extension power of 60%

Examination

  • SLR
  • may be able to palpate a defect

Xrays

  • AP, lateral & skyline views

Differential Diagnosis

  • Tendon ruptures
  • patellar dislocation
  • growth abnormalities (patella bipartite)
    • these are located on the proximal, lateral portion of patella

Classification

Displaced vs Undisplaced

AO classification

AO Classification of Patella Fractures
Classification Description
A extra articular extensor mechanism avulsions, etc
B partial articular – extensor mechanism in tact, therapy may be non operative, or ORIF, if articular surface incongruent
C Complete articular, disrupted extensor mechanism

Fracture Configuration

  • Undiplaced
  • Transverse
  • Lower or upper pole
  • Comminute undisplaced
  • Comminuted displaced
  • Vertical
  • Osteochondral

Treatment

  • Approach to treatment
  • almost always operative if displaced, extensor mechanism disrupted

Non-operative

  • Zimmer Knee Split

Operative

  • Options
    • ORIF
    • Patellectomy for unreconstructable fractures
  • Extra-articular:
    • Lag screw plus tension band wire or cerclage
    • Transosseous suture of avulsed tendon
  • Partial-articular:
    • Non displaced non-operative
    • Displaced, simple
      • lag screw plus cerclage
      • tension band wire
    • Multifragmentary
      • circumferetntial cerclage plus tension band
  • Complete articular
    • k-wire plus tension band wire
    • with 3rd fragment, lag screw plus tension band
    • with 4th fragment or more
      • k-wires, screws plus tension band
      • partial or total patellectomy
      • Should always use figure of 8 or figure of 0 to augment, reinforce repair
    • Use tibial/ patellar figure of 8 to protect inferior pole partial patellectomy or patellar tendon repair
  • Patellectomy
    • preserve as much of the extensor apparatus as possible
    • functionally better to shorten the quadriceps somewhat, as you are reducing its power by taking out patella
    • if unable to coapt, then can do V to Y tendinoplasty of quadriceps tendon
    • Keep as much of the patella as possible (even one large fragment)

Post Operative

  • brace (Zimmer) until quadriceps control regained
  • active ROM OK to 90°
  • CPM advisable
  • Partial ROM for 6 weeks

Complications

  • wound breakdown
    • Important to separate layers between subcutaneous fascia & extensor mechanism