Key Points Summary:
Shortcuts
- Anatomy & Indications
- Anatomy of the Knee
- When is TTO Indicated?
- Preoperative Preparation
- Patient Selection
- Imaging Considerations
- Operative Technique
- Medial Approach & Exposure
- Tuberosity Transfer
- Fixation Methods
- Postoperative Management
- Outcomes & Complications
- References
Tibial Tubercle Transfer (Osteotomy)
Tibial tubercle transfer (TTO), also known as tibial tuberosity osteotomy, is a surgical procedure performed to correct patellofemoral malalignment. This procedure involves surgically repositioning the attachment point of the patellar tendon on the tibia to improve the mechanics of the patellofemoral joint. TTO is commonly used to treat anterior knee pain related to patellofemoral dysfunction, patellar instability, and other conditions associated with abnormal patellar tracking.
Tibial tubercle transfer is frequently performed in combination with MPFL reconstruction when patients have both an elevated TT-TG distance and ligamentous instability. A systematic review by Burnham et al. found that addressing multiple anatomic risk factors simultaneously improves outcomes and reduces redislocation rates in patients with complex patellar instability. In patients with significant trochlear dysplasia, TTO may also be combined with trochleoplasty to address both bony alignment and groove morphology.
Anatomy & Indications
Anatomy of the Knee
The patellofemoral joint is formed by the patella (kneecap) articulating with the femoral trochlea. The patellar tendon attaches the quadriceps muscle group to the tibial tuberosity, a bony prominence on the anterior tibia just below the knee joint. The position of the tibial tuberosity relative to the femoral trochlea determines the Q-angle (quadriceps angle), which is the angle formed between the line of pull of the quadriceps muscle and the patellar tendon. A larger Q-angle results in greater lateral forces on the patella, potentially causing maltracking and patellofemoral pain. Patients with genu valgum (knock knees) may have a naturally increased Q-angle, which contributes to lateral patellar tracking and can be one of the factors considered when evaluating whether tibial tubercle transfer is appropriate.
When is TTO Indicated?
TTO is indicated in patients with:
- Anterior knee pain with patellofemoral malalignment
- Lateral patellar tracking or maltracking
- Elevated Q-angle or TT-TG distance
- Patellar instability unresponsive to conservative treatment
- Chondral damage to the patellofemoral joint secondary to malalignment
Preoperative Preparation
Patient Selection
Careful patient selection is essential for successful TTO outcomes. Ideal candidates are skeletally mature patients (typically over 18 years old) with symptomatic patellofemoral malalignment refractory to conservative treatment. Patients should have realistic expectations and understand the recovery timeline. Contraindications include severe patellofemoral arthritis, significant ligamentous laxity, and patients unable to comply with postoperative rehabilitation.
Imaging Considerations
Comprehensive imaging is crucial for surgical planning. Standard radiographs should include AP, lateral, and skyline views of the knee. Advanced imaging such as CT or MRI is used to measure anatomical parameters:
- Tibial Tuberosity-Trochlear Groove Distance (TT-TG): Measured on axial CT imaging, distances greater than 20 mm are generally considered abnormal.
- Q-angle: Measured on standing AP radiographs, normal values are typically 10-15 degrees in males and 15-17 degrees in females.
- Patellar tilt: Assessed on axial imaging to determine the degree of lateral tracking.
- Articular surface condition: MRI evaluation of chondral surfaces guides the extent of necessary correction.
Operative Technique
Medial Approach & Exposure
The patient is positioned supine under general anesthesia with the operative knee flexed to 90 degrees. A medial longitudinal incision is made over the anterior tibial metaphysis, typically beginning 2-3 cm proximal to the tibial tuberosity and extending distally 3-4 cm. Careful soft tissue dissection and retraction expose the anterior tibial cortex. The tuberosity is then outlined with electrocautery to define the osteotomy margins.
Tuberosity Transfer
An osteotomy is created through the anterior tibial cortex and metaphysis, incorporating the tibial tuberosity. The extent of the osteotomy is determined by preoperative measurements and intraoperative assessment. The tuberosity segment is then transferred medially, distally, or in a combination direction as indicated by the patient’s anatomy and degree of malalignment. The distance of transfer is typically guided by the TT-TG measurement, aiming for a correction to 8-15 mm. Intraoperative imaging or fluoroscopy may be used to verify the position and degree of transfer.
Fixation Methods
Secure fixation is essential to prevent loss of correction during healing. Common fixation techniques include:
- Screw fixation: Cannulated screws placed perpendicular to the osteotomy provide rigid fixation. Typically 2-3 screws are used for adequate stability.
- Plate fixation: Specialized plates designed for tibial tuberosity transfer provide additional support and are preferred in some cases.
- Combined fixation: Use of both screws and plates for maximum stability in cases with extensive transfers or poor bone quality.
Once satisfactory positioning and fixation are confirmed, the soft tissues are closed in layers, and a sterile dressing is applied.
Postoperative Management
Postoperative care focuses on pain management, swelling control, and progressive rehabilitation. Most patients are allowed immediate weight-bearing as tolerated with crutches, transitioning to full weight-bearing within 2-4 weeks. Range-of-motion exercises are initiated early, progressing to strengthening exercises as tolerated. Return to normal activities is typically gradual, with most patients returning to unrestricted activities by 3-4 months post-op. Physical therapy is essential for optimal outcomes.
Outcomes & Complications
When performed on appropriately selected patients with correct surgical technique, TTO provides excellent outcomes. Most patients experience significant improvement in anterior knee pain and functional capacity. Complications are relatively uncommon but can include:
- Infection (superficial or deep)
- Hardware irritation or prominence
- Nonunion or malunion at the osteotomy site
- Overcorrection or undercorrection of malalignment
- Neurovascular injury
- Loss of motion
Long-term studies demonstrate sustained pain relief and functional improvement in 80-90% of appropriately selected patients.