Treatment of Patellar Fractures
For displaced patellar fractures (>2-3 mm step-off or >1-4 mm displacement) or those disrupting the extensor mechanism, surgical treatment with open reduction and internal fixation is recommended, while undisplaced fractures with intact extensor mechanism should be treated conservatively with immobilization. 1
Initial Assessment and Classification
- Obtain anteroposterior and lateral radiographs as the primary diagnostic modality to assess fracture displacement, comminution, and extensor mechanism integrity 1
- Consider CT imaging preoperatively for complex or comminuted fractures, as this frequently modifies both classification and treatment planning by revealing fracture complexity not apparent on plain films 1
- Assess extensor mechanism integrity clinically by evaluating the patient's ability to perform straight leg raise against gravity 2
Treatment Algorithm
Non-Displaced Fractures (≤2 mm displacement, intact extensor mechanism)
- Immobilize the knee in extension or slight flexion using a cast or brace 1, 3
- Initiate early rehabilitation to prevent knee joint capsule contractures and cartilage degeneration 2
- Serial radiographic monitoring is essential to detect any secondary displacement requiring surgical intervention 1
Displaced Fractures (>2-3 mm step-off or >1-4 mm displacement)
Surgical intervention is indicated to restore articular congruity and extensor mechanism function 1
Simple Transverse (2-Part) Fractures
- Modified anterior tension band wiring is the treatment of choice for non-comminuted transverse fractures 2
- Combine with cannulated screw fixation for biomechanical superiority and enhanced stability 2
- Additional circular cerclage wiring using metal cerclage wires or FiberWires increases fixation stability and decreases re-dislocation risk 2
Comminuted Fractures
- Perform open reduction and internal fixation using small fragment screws or angular stable plates to achieve anatomic restoration of the retropatellar surface 2
- Anatomical reconstruction of the articular surface is mandatory to prevent posttraumatic osteoarthritis 1
- Supplemental cerclage wiring should be added to increase construct stability in severely comminuted patterns 2
Distal Avulsion Fractures
- Fix with small fragment screws and protect with a transtibial McLaughlin cerclage 2
Salvage Options
- Partial or complete patellectomy should be reserved only as a rare salvage operation due to severe functional impairment and compromised quadriceps force transmission 2
Postoperative Management
- Early rehabilitation is recommended regardless of treatment method to avoid knee joint contractures and cartilage degeneration 2
- Hardware removal is frequently necessary after fracture healing due to implant-related pain, particularly with tension band constructs 1
- Monitor for complications including nonunion, infection, posttraumatic arthritis, arthrofibrosis, symptomatic hardware, and extensor mechanism insufficiency 4
Special Populations
Post-Total Knee Arthroplasty Fractures
- Patellar fractures occur in up to 5.2% of patients after total knee arthroplasty, usually within the first few postoperative years 5
- Treatment should be individualized based on fracture displacement, comminution, and patellar button fixation status 6
- Minimally displaced, non-comminuted fractures should be immobilized conservatively 6
- Displaced, comminuted fractures with loose patellar prostheses require operative treatment 6
Common Pitfalls
- Failure to obtain CT imaging in comminuted fractures leads to underestimation of fracture complexity and inadequate surgical planning 1
- Inadequate restoration of articular surface inevitably results in posttraumatic osteoarthritis 1
- Delayed or inadequate rehabilitation causes arthrofibrosis and permanent loss of knee motion 2
- Overlooking extensor mechanism disruption in apparently "undisplaced" fractures leads to inappropriate conservative management 1