Treatment of Patellar Fracture
For a patient with a patellar fracture, obtain anteroposterior and lateral knee radiographs immediately, then determine treatment based on fracture displacement and extensor mechanism integrity: non-displaced fractures with intact extensor mechanism receive conservative management with hinged knee brace and protected weight-bearing, while displaced fractures (>2-3mm step-off or >1-4mm displacement) or those with disrupted extensor mechanism require surgical fixation. 1, 2
Initial Diagnostic Approach
Imaging Protocol
- Standard radiographs are the first-line diagnostic study, including anteroposterior and lateral views at 25-30 degrees of knee flexion to assess fracture pattern, displacement, and articular congruity 3, 1
- The lateral view should demonstrate the patella in profile and allows evaluation for joint effusion 3
- CT imaging should be obtained when radiographs are inconclusive, particularly for complex fracture patterns, as it frequently changes both classification and treatment decisions by revealing fracture complexity not apparent on plain films 1, 2
- A patellofemoral (sunrise) view is typically obtained in suspected patellar fractures to assess articular surface involvement 3
Critical Clinical Assessment
- Examine extensor mechanism integrity immediately - the ability to perform straight leg raise against gravity is the key clinical finding 4, 2
- Check for open fracture, which requires immediate coverage with clean dressing to reduce contamination risk 1
- Assess for vascular compromise (blue, purple, or pale extremity) requiring immediate medical attention 1
- Evaluate for severe bleeding requiring emergency treatment priority 1
Treatment Algorithm
Non-Displaced Fractures (<2mm displacement, intact extensor mechanism)
Conservative management is appropriate for non-displaced fractures with intact extensor mechanism 1, 2
Conservative Protocol
- Hinged knee brace with initial non-weight bearing or touch-down weight bearing with crutches 5
- Progress to partial weight bearing while continuing brace protection during ambulation 5
- Advance to full weight bearing as fracture healing progresses, typically by 8-12 weeks 5
- Serial radiographs at 2,4, and 6 weeks are essential to confirm maintained fracture alignment - this is critical as displacement can occur during conservative treatment 5
Common pitfall: Functional knee braces are designed primarily for ligamentous instability, not fracture immobilization, though they provide some stability during rehabilitation 5. The key is serial imaging to catch any loss of reduction early.
Displaced Fractures (>2-3mm step-off or >1-4mm displacement)
Surgical treatment is recommended for fractures with >2-3mm articular step-off, >1-4mm displacement, or disrupted extensor mechanism 1, 2
Surgical Indications by Fracture Pattern
- Transverse fractures with displacement - often associated with patellar maltracking and require surgical intervention 1
- Multiple fracture lines (flail segments) - should be stabilized whenever possible, applying principles similar to rib fracture stabilization 1
- Vertical fractures through fixation holes in post-arthroplasty patients may require surgical intervention 1
- Comminuted fractures - anatomical reconstruction of the articular surface is the only way to prevent posttraumatic osteoarthritis 2
Surgical Technique Considerations
The evidence comparing surgical techniques is of very low quality, making definitive recommendations difficult 6. However:
- Tension band wiring has been the most commonly employed technique historically 2
- Percutaneous osteosynthesis versus open surgery shows no clear superiority based on very low-quality evidence 6
- Cable pin systems versus tension band technique shows very low-quality evidence favoring cable pins for function and adverse events 6
- Hardware removal is frequently required after fracture healing due to implant-related pain - this is a common complication that patients should be counseled about 2
Critical caveat: Failure to restore articular surface contour results in posttraumatic arthritis 2. The surgical goal must be anatomical reduction of the articular surface, not just restoration of extensor mechanism continuity.
Special Considerations for Osteoporosis Risk
Systematic Fracture Risk Evaluation
Every patient aged 50 years and over with a patellar fracture should be evaluated systematically for risk of subsequent fractures 3
Comprehensive Assessment Protocol
- DXA of spine and hip to measure bone mineral density 3
- Imaging of the spine (radiography or vertebral fracture assessment) to detect subclinical vertebral fractures, which are frequent in patients with recent non-vertebral fractures 3
- Falls risk evaluation starting with history of falls during the last year, followed by specific tests when indicated 3
- Laboratory evaluation including erythrocyte sedimentation rate, serum calcium, albumin, creatinine, thyroid-stimulating hormone, and vitamin D when clinically indicated 3
- Clinical risk factors assessment including age, gender, low body mass index, lifestyle, personal and family history of fracture using tools such as FRAX, Garvan, or Q-Fracture 3
Fracture Liaison Service Model
The most effective organizational structure for risk evaluation and treatment initiation is a Fracture Liaison Service (FLS) with a dedicated coordinator 3. This model improves osteoporosis treatment implementation from 26% to 45% within 6 months after fracture 3.
Pharmacological Prevention
For patients at high risk of subsequent fractures, pharmacological treatment should use drugs demonstrated to reduce vertebral, non-vertebral, and hip fractures 3
- Alendronate and risedronate are first-choice agents due to good tolerance, low cost (generic availability), and extensive clinical experience 3
- For patients with oral intolerance, dementia, malabsorption, or non-compliance, zoledronic acid (intravenous) or denosumab (subcutaneous) are alternatives 3
- Vitamin D supplementation (800 IU/day) with adequate calcium intake is associated with 15-20% reduction in non-vertebral fractures and 20% reduction in falls 3
- For patients with very severe osteoporosis, anabolic agents such as teriparatide are an option 3
Important warning: High pulse dosages of vitamin D are associated with increased fall risk and should be avoided 3
Complications and Long-Term Outcomes
Expected Complications
- Arthrosis of the patellofemoral joint is very common after healing of patellar fractures 4
- Substantial functional deficits may persist long after fracture healing 4
- Painful and functional complications including knee stiffness, loss of extension, and patellofemoral osteoarthritis can be very disabling 2
- These complications often compromise return to professional or recreational activity and induce falls in elderly populations 2