Surgical fixation of patellar fractures yields predictable bony union rates of 85% to 92%. However, due to the subcutaneous location of the patella and the high tensile loads delivered by the extensor mechanism, specific hardware-related and articular complications can arise. Understanding their incidence and management helps distinguish expected postoperative recovery from issues requiring urgent clinical intervention.
Overview of Potential Complications
| Complication | Estimated Incidence | Primary Contributing Factors |
|---|---|---|
| Symptomatic Hardware Prominence | 30–50% | Thin overlying soft tissue; prominent K-wire or Cerclage wire ends |
| Post-Traumatic Osteoarthritis | 20–30% | Baseline chondral damage, residual articular incongruity ($\text{step-off} > 2\text{ mm}$) |
| Arthrofibrosis / Knee Stiffness | 5–15% | Prolonged immobilization, delayed passive range-of-motion (ROM) rehabilitation |
| Anterior Knee Pain | 15–25% | Retropatellar friction, quadriceps weakness during stair ambulation |
| Fixation Failure / Displacement | 2–5% | High comminution, osteoporotic bone, unprotected early deep flexion |
| Surgical Site Infection (SSI) | 2–5% | Uncontrolled diabetes, compromised soft-tissue envelope in open fractures |
| Delayed Union / Non-Union | 2–5% | Impaired vascular supply, mechanical instability, heavy nicotine use |
| Deep Vein Thrombosis (DVT) | 1–3% | Postoperative immobility, non-compliance with chemical thromboprophylaxis |
Early Postoperative Risks (Weeks 0–6)
- Superficial Wound Infection & Hematoma: Localized wound hematomas occur in 5–8% of patients. Superficial infections (2–5%) are managed with oral antimicrobials; deep joint sepsis (<1–2%) requires urgent arthroscopic or open irrigation and debridement.
- Early Hardware Failure: Loss of reduction or wire breakage (<3%) typically stems from unexpected falls or early unbraced weight-bearing before callus formation.
- Hypoesthesia: Numbness across the anterior knee due to injury of small infrapatellar cutaneous nerve branches occurs in 10–15% of cases and resolves gradually.
Late Complications (Months 3–18)
- Prominent Hardware: The most frequent late complication. K-wires or screws often cause localized skin impingement and pain during kneeling or deep flexion. Elective hardware removal after solid radiographic union (6–12 months post-surgery) resolves symptoms in $>95\%$ of cases.
- Arthrofibrosis: Fibrous intra-articular adhesions reduce knee flexion. Early closed manipulation under anesthesia (MUA) within the first 3 months restores functional motion in 75–90% of affected knees.
- Non-Union: Arrest of bony bridging after 6 months requires revision internal fixation paired with autologous bone grafting (75–85% success rate).
Complication Prevention Protocols
- Anatomical Reduction: Restoring the articular surface with $<2\text{ mm}$ step-off significantly decreases the incidence of post-traumatic patellofemoral arthritis.
- Implant Optimization: Utilizing low-profile anatomical plates or cannulated screws instead of traditional K-wires reduces symptomatic hardware irritation to $<5\text{–}10\%$.
- Strict Early Protection: Locking the hinged knee brace at $0^\circ$ of extension during ambulation protects the construct from excessive tensile forces.
- Guided Early Mobilization: Initiating gentle passive ROM and manual patellar mobilizations within the first 2 weeks prevents arthrofibrosis.
- Systemic Risk Factor Management: Smoking cessation (nicotine increases non-union risk) and strict glycemic control ($\text{HbA1c} < 7.5\%$) to promote bone healing and prevent infection.
When to Seek Immediate Medical Evaluation
Contact your orthopedic team or seek emergency care if you develop:
- Body temperature $> 38.3^\circ\text{C}$ accompanied by rigors.
- Spreading wound erythema, local skin breakdown, or purulent drainage.
- Hardware eroding through or tenting the skin surface.
- Sudden loss of active knee extension following a slip or fall.
- Unilateral calf pain, tenderness, and asymmetric edema (suspected DVT).
Frequently Asked Questions About Complications of Quadriceps Tendon Repair Surgery
What is the overall complication rate associated with quadriceps tendon repair surgery?
Quadriceps tendon repair surgery is an established and predictable orthopedic procedure. The overall complication rate is relatively low, typically documented between 2% and 6%. Major complications—such as construct failure, re-rupture, or deep joint infection—occur in fewer than 1% to 3% of patients when accurate anatomical tensioning and structured postoperative rehabilitation protocols are implemented.
What are the primary causes and risks of quadriceps tendon re-rupture after repair?
Re-rupture of the repaired tendon is an uncommon event (<2%–4%), typically driven by specific mechanical or biological factors:
- Accidental stumbles, slips, or sudden forced eccentric knee flexion during the first 6 weeks before bone-to-tendon biological union is established.
- Walking or bearing weight without the hinged knee brace locked in full extension (0°).
- Compromised tissue vascularity and collagen healing due to end-stage renal disease, uncontrolled diabetes mellitus, or chronic corticosteroid exposure.
- Premature return to athletic running, jumping, or heavy resistance training before tissue maturation.
Why does knee stiffness (arthrofibrosis) occur and how can it be prevented?
Postoperative joint stiffness and restricted terminal flexion stem from excessive fibrous scar tissue and capsular adhesions (arthrofibrosis). This is most commonly seen when the knee is immobilized in a rigid brace for excessive periods without controlled movement. Prevention relies on initiating early, supervised passive flexion exercises (gradually progressing from 0°–30° up to 90° by week 6) and regular patellar mobilizations to maintain soft tissue compliance.
What is an extension lag (extensor lag) and why does it happen after surgery?
An extension lag is defined as the inability to actively achieve terminal knee extension during a straight leg raise despite possessing full passive extension. It is caused by profound quadriceps arthrogenic muscle inhibition, rapid muscle atrophy, or minor construct elongation during healing. It is addressed through focused neuromuscular electrical stimulation (NMES), biofeedback, and progressive isometric quadriceps strengthening.
What are the hallmark signs and symptoms of a surgical site infection?
While superficial and deep infections occur in fewer than 1% of cases, prompt recognition is vital. Contact your surgical team if you experience:
- Persistent fever exceeding 38.3°C (101°F) or unexplained rigors and chills.
- Spreading redness, localized heat, and tense induration around the anterior knee incision.
- Continuous serosanguinous or purulent wound drainage.
- A progressive, throbbing increase in resting knee pain that is unresponsive to analgesics.
How is deep vein thrombosis (DVT) prevented after quadriceps tendon repair?
Because postoperative immobilization and reduced mobility elevate venous thromboembolism risks, standard prevention includes:
- Strict adherence to prescribed anticoagulant medications (such as low-molecular-weight heparin or oral factor Xa inhibitors) for 2 to 4 weeks.
- Performing active ankle pump exercises (20–30 repetitions every waking hour) to stimulate calf muscle venous pumping.
- Wearing graduated compression stockings on both lower extremities.
- Early protected weight-bearing with crutches in a locked brace as cleared by your surgeon.
Can transosseous patellar drilling cause an iatrogenic patellar fracture?
Iatrogenic patellar fractures are rare (<1%) but can occur when drilling vertical transosseous tunnels across the patella. Drilling multiple large tunnels or positioning holes too close to the anterior cortex creates focal stress risers, particularly in osteoporotic bone. Modern techniques using suture anchors or small-diameter drills with adequate cortical spacing significantly mitigate this complication.
What causes persistent anterior knee pain after tendon repair?
Residual anterior knee pain or discomfort during stair descent may arise from pre-existing chondromalacia or patellofemoral cartilage wear unmasked after surgery. It can also stem from altered patellofemoral biomechanics due to prolonged quadriceps weakness, or localized numbness and dysesthesia caused by stretching the infrapatellar branch of the saphenous nerve during surgical exposure.
How do smoking and chronic systemic diseases increase surgical complications?
Nicotine causes peripheral microvascular constriction and reduces local tissue oxygenation, impairing collagen synthesis and elevating tendon-to-bone nonunion and wound breakdown risks by over 30%. Poorly controlled diabetes impairs leukocyte function, markedly raising surgical site infection risks. Complete smoking cessation and tight glycemic control are critical throughout the perioperative phase.
What crucial steps should patients follow to minimize post-surgical complications?
To secure a safe and durable functional recovery, patients should:
- Ensure the hinged knee brace remains locked at 0° extension during all walking, standing, and sleeping for the first 6 weeks.
- Never force aggressive knee flexion beyond the degrees designated for each rehabilitation phase.
- Attend regular physical therapy sessions focusing on patellar mobility and early isometric quadriceps reactivation.
- Refrain from unbraced weight-bearing, heavy manual lifting, or pivoting sports until cleared by functional testing (typically 6 to 9 months postoperatively).