Management of Patellar Fractures and Extensor Mechanism Disruptions

High-Yield Summary

• Patellar fractures and extensor mechanism disruptions require precise assessment of extensor continuity and articular congruity to guide management.
• Displaced fractures with >2 mm articular step-off or extensor lag mandate surgical fixation to restore knee mechanics and prevent post-traumatic arthritis.
• Tension band wiring remains the gold standard for transverse patellar fractures; comminuted or inferior pole fractures often require fragment excision and patellar tendon repair or augmentation.
• Extensor mechanism disruptions without fracture (quadriceps or patellar tendon ruptures) demand early surgical repair to restore knee extension and prevent chronic disability.
• Postoperative rehabilitation protocols must balance early mobilization with protection of repair integrity to optimize functional outcomes.

Clinical Fundamentals

Relevant Anatomy

The patella functions as a sesamoid bone within the quadriceps tendon, increasing the lever arm of the extensor mechanism. The extensor mechanism comprises the quadriceps tendon proximally, the patellaand the patellar tendon distally, inserting on the tibial tubercle. The retinacular structures provide medial and lateral stability. Blood supply is predominantly from the genicular arteries, with a watershed zone at the inferior pole, predisposing to fracture nonunion.

Biomechanics

The patella transmits quadriceps force to the tibia, increasing extension efficiency by 30%. Disruption of the extensor mechanism or articular incongruity alters load distribution, increasing contact pressures and risk of osteoarthritis. The extensor mechanism must be restored to maintain knee extension strength and prevent extensor lag.

Epidemiology

Patellar fractures account for approximately 1% of all skeletal fractures, commonly resulting from direct trauma or eccentric quadriceps contraction. Extensor mechanism ruptures are less common but critical injuries, often occurring in middle-aged males with degenerative tendon changes or in high-energy trauma.

Classification & Diagnosis

Decision-Making Algorithm

Non-Operative Management

Indicated for nondisplaced fractures (<2 mm displacement, <3 mm articular step-off) with intact extensor mechanism and ability to perform straight leg raise. Immobilization in extension for 4-6 weeks followed by gradual mobilization.

Operative Management

Indications include displaced fractures (>2 mm step-off), extensor mechanism disruption, inability to perform straight leg raise, open fracturesand comminuted fractures compromising extensor function.

Surgical Approach and Implant Selection

• Transverse fractures: Tension band wiring converts tensile forces to compression; preferred for simple patterns.
• Comminuted fractures: Partial patellectomy with tendon repair or low-profile plating if fragments are reconstructible.
• Inferior pole fractures: Often require fragment excision and patellar tendon repair with augmentation (e.g., cerclage or suture anchors).
• Extensor mechanism ruptures: Primary tendon repair with nonabsorbable sutures; augmentation with autograft or synthetic material in chronic cases.

Surgical Mastery & Pearls

Step-by-Step Conceptual Overview

1. Exposure: Midline longitudinal incision centered over the patella; careful dissection to preserve retinacular integrity.
2. Fracture Reduction: Achieve anatomic articular congruity; provisional fixation with K-wires.
3. Fixation: Apply tension band wiring with figure-of-eight stainless steel wire over two parallel K-wires; ensure wires are flush to prevent soft tissue irritation.
4. Comminuted Fractures: Consider low-profile plates or partial patellectomy; maintain extensor mechanism continuity.
5. Extensor Mechanism Repair: Use Krackow or Bunnell sutures with strong nonabsorbable material; secure to bone via transosseous tunnels or suture anchors.
6. Intraoperative Red Flags: Avoid overtightening tension bands causing patellar tilt; confirm full knee extension without gapping; inspect retinacula for tears requiring repair.
7. Closure: Layered closure with retinacular repair to restore medial-lateral stability.

Evidence-Based Synthesis

Recent randomized controlled trials and meta-analyses reinforce tension band wiring as the standard for simple transverse fractures, demonstrating superior functional outcomes and lower reoperation rates compared to screw fixation alone. However, emerging evidence supports the use of low-profile locking plates in comminuted fractures to reduce hardware irritation and improve fixation stability. The role of partial patellectomy remains controversial, with data suggesting that preserving patellar length correlates with better extensor strength and knee function.

For extensor mechanism ruptures, early surgical repair within 2 weeks yields superior outcomes compared to delayed intervention. Augmentation techniques, including autografts or synthetic scaffolds, show promise in chronic or revision cases but lack high-level evidence for routine use.

Rehabilitation protocols emphasizing early controlled motion have demonstrated improved range of motion without compromising repair integrity, challenging traditional prolonged immobilization.

Master Class Pro-Tip

Meticulous restoration of the extensor mechanism’s anatomic length and tension is paramount. Intraoperative assessment of patellar height using the Insall-Salvati ratio under fluoroscopy guides tensioning of repairs and fixation constructs. Over-tensioning leads to restricted flexion and anterior knee pain, while undertensioning results in extensor lag and instability. Mastery lies in balancing these forces dynamically during surgery, tailoring fixation and repair to the individual’s anatomy and injury pattern for optimal functional restoration.

Last Updated on September 6, 2026 by OrthoNet AI