Mandatory NPO status for 8 hours prior to surgery. Pre-operative assessment including complete blood count, coagulation profile, and cardiovascular clearance. Radiographic planning (full-length weight-bearing standing X-rays) to determine the angle of correction. Prophylactic antibiotic administration within 60 minutes of incision and deep vein thrombosis prophylaxis.
Post-operative management involves strict pain control, early mobilization with physical therapy, and restricted weight-bearing as dictated by the surgeon (usually toe-touch weight-bearing for 6 weeks). Monitoring for neurovascular compromise and surgical site infection is mandatory. Discharge planning includes wound care instructions, venous thromboembolism prophylaxis, and scheduled follow-up radiographs to ensure hardware stability and healing.
Comprehensive Clinical Guide: High Tibial Osteotomy (HTO) for Genu Varum
1. Introduction and Clinical Overview
Genu varum, colloquially known as "bow-leg," is a clinical deformity characterized by the lateral bowing of the tibia and femur, resulting in a knee joint that remains apart even when the ankles are touching. While minor physiological bowing is common in early childhood, persistent or progressive genu varum in adults is a significant clinical concern. It leads to malalignment of the mechanical axis of the lower limb, shifting the weight-bearing load primarily to the medial compartment of the knee.
High Tibial Osteotomy (HTO) is a definitive surgical intervention designed to realign the mechanical axis of the lower extremity. By surgically altering the proximal tibial geometry, the surgeon shifts the weight-bearing forces from the damaged medial compartment to the relatively healthier lateral compartment. This procedure is primarily indicated for active, younger patients who are not yet candidates for total knee arthroplasty (TKA) but suffer from symptomatic medial compartment osteoarthritis secondary to varus malalignment.
2. Technical Specifications and Biomechanical Mechanisms
The primary goal of an HTO is the correction of the mechanical axis (Mikulicz line). In a healthy knee, the mechanical axis passes through the center of the knee joint. In genu varum, this line shifts medially, causing increased contact pressure on the medial tibial plateau.
Biomechanical Principles
- Load Redistribution: By performing an osteotomy, the surgeon creates a controlled fracture (or cut) in the proximal tibia. By opening or closing this space and fixing it with a rigid plate, the limb is placed into a slight valgus position (overcorrection).
- The "Weight-Relieving" Effect: Shifting the mechanical axis to the lateral compartment offloads the medial articular cartilage, potentially slowing the progression of arthritic degeneration and providing significant pain relief.
- Surgical Techniques:
- Medial Opening-Wedge HTO: The most common modern technique. A cut is made on the medial side, the bone is opened, and a bone graft or synthetic wedge is inserted. It is technically simpler and allows for better adjustment of the slope.
- Lateral Closing-Wedge HTO: The lateral cortex is cut, and a wedge of bone is removed. While highly stable, it carries risks of peroneal nerve injury and shortening of the limb.
3. Clinical Indications and Patient Selection
Patient selection is the single most critical factor in the success of an HTO. The ideal candidate is typically under 60, physically active, and has isolated medial compartment disease.
Indications
| Category | Criteria |
|---|---|
| Age | Typically < 60 years |
| Activity Level | High demand (manual laborers, athletes) |
| Pain Profile | Medial knee pain, mechanical symptoms |
| Alignment | Varus deformity < 15 degrees |
| ROM | Knee flexion > 90 degrees |
Contraindications
- Inflammatory Arthritis: Rheumatoid arthritis is a contraindication due to systemic disease.
- Severe Cartilage Loss: If the lateral compartment already shows grade III-IV chondromalacia or if the joint space is obliterated (bone-on-bone).
- Fixed Flexion Deformity: If the patient cannot fully extend the knee.
- Smoking: Nicotine use significantly impairs bone healing and increases the risk of non-union.
4. Pre-Operative Preparation
Preparation involves a multidisciplinary approach to ensure the patient is physiologically primed for major orthopedic surgery.
- Radiographic Assessment: Long-leg standing radiographs (teleroentgenograms) are mandatory to measure the mechanical axis (Hip-Knee-Ankle angle).
- MRI Evaluation: To assess the status of the lateral compartment and the integrity of the menisci.
- Smoking Cessation: Patients must be tobacco-free for at least 6 weeks pre- and post-operatively to ensure adequate bone consolidation.
- Physical Therapy (Pre-hab): Strengthening the quadriceps, hamstrings, and hip abductors is essential to facilitate post-operative rehabilitation.
5. The Procedure: Step-by-Step
Phase I: Access and Preparation
The patient is placed supine on a radiolucent table. A tourniquet is applied to the proximal thigh. A medial longitudinal incision is made over the proximal tibia.
Phase II: The Osteotomy
Using fluoroscopic guidance, the surgeon identifies the osteotomy site, typically 2–3 cm below the joint line. A guide wire is placed to ensure the cut is parallel to the joint surface and directed toward the tip of the fibular head.
Phase III: The Cut
A bone saw is used to make the transverse cut. In an opening-wedge procedure, the medial cortex is opened gradually using specialized chisels/spreaders until the desired mechanical axis is achieved on the C-arm.
Phase IV: Fixation
A low-profile locking plate (specifically designed for HTO) is applied to the medial aspect of the tibia. Bone graft or a porous metal wedge is inserted into the gap to maintain the correction.
Phase V: Closure
The wound is irrigated, layers are closed, and a sterile compression dressing is applied.
6. Post-Operative Recovery Protocol
Recovery from an HTO is a marathon, not a sprint. Bone healing typically takes 3–6 months.
- Weeks 0–6: Partial weight-bearing (usually 10-20kg) with crutches. Continuous Passive Motion (CPM) or early range-of-motion exercises to prevent stiffness.
- Weeks 6–12: Gradual progression to full weight-bearing as radiographic evidence of bone consolidation appears. Focus on quadriceps reactivation.
- Month 3–6: Return to low-impact activities (cycling, swimming).
- Month 6+: Return to higher-impact activities as tolerated.
7. Risks and Complications
Despite high success rates, HTO is a major surgical procedure with inherent risks.
- Non-Union/Delayed Union: Failure of the bone to heal at the osteotomy site.
- Neurovascular Injury: The peroneal nerve is at risk during lateral-side dissection or if the bone is over-corrected.
- Infection: Superficial or deep surgical site infection (SSI).
- Over/Under-Correction: Failure to achieve the exact mechanical alignment, leading to recurrence of symptoms or secondary lateral compartment wear.
- Hardware Irritation: The medial plate may be prominent under the skin, requiring removal after the bone has fully healed.
8. Alternative Treatments
Before opting for HTO, clinicians often exhaust conservative management:
1. Offloader Bracing: Valgus-producing braces that shift weight away from the medial compartment.
2. Viscosupplementation: Intra-articular hyaluronic acid injections to improve joint lubrication.
3. Weight Loss: Significant reduction in BMI to decrease the compressive forces across the knee.
4. Unicompartmental Knee Arthroplasty (UKA): A partial joint replacement, often preferred in older patients with limited activity demands.
9. Frequently Asked Questions (FAQ)
1. How long does the correction last?
HTO is designed to delay, not eliminate, the need for total knee replacement. Most patients experience 10–15 years of symptomatic relief.
2. Is the procedure painful?
Post-operative pain is managed with multimodal analgesia, including nerve blocks and scheduled anti-inflammatories.
3. Will my leg be perfectly straight after surgery?
The goal is a slight valgus (knock-kneed) alignment to ensure the weight-bearing axis passes through the lateral compartment.
4. Can I play sports after an HTO?
Yes, once the osteotomy is fully consolidated. Low-impact sports are encouraged; high-impact sports (running, contact sports) should be discussed with your surgeon.
5. Do I need to remove the metal plate?
Not necessarily. If the plate is not causing skin irritation or pain, it is common to leave it in place.
6. What happens if the bone doesn't heal?
Non-union is rare but may require a secondary procedure, such as bone grafting or revision of the hardware.
7. How much weight can I put on my leg immediately?
Usually, patients are limited to "toe-touch" or partial weight-bearing for the first 6 weeks to protect the osteotomy site.
8. Is HTO better than a Knee Replacement?
For younger, active patients, HTO preserves the natural joint and allows for higher activity levels than a total knee replacement.
9. Will I need physical therapy?
Yes, physical therapy is mandatory and is the most important factor in a successful outcome.
10. Does smoking affect the surgery?
Smoking is a major risk factor for non-union. Most surgeons will refuse to perform an elective HTO on a patient who currently smokes.
10. Conclusion
Tibial Osteotomy remains the gold standard for the younger, active patient population suffering from medial compartment genu varum. By correcting the mechanical axis, this procedure effectively delays the need for arthroplasty, allowing patients to maintain a high quality of life and athletic function. However, success is strictly predicated on careful patient selection, precise surgical execution, and a disciplined post-operative rehabilitation program. As orthopedic technology advances, the use of patient-specific instrumentation (PSI) and 3D-printed wedges continues to improve the accuracy and outcomes of this life-changing procedure.