Comprehensive Knee Osteotomy: HTO, DFO, and TTO

These three osteotomies share one principle — realign the limb so that load is shifted away from a diseased compartment onto a healthy one — but each addresses a different compartment. The operation chosen depends on which compartment is failing and the direction of the deformity.

Contraindications. - Absolute: inflammatory arthritis (rheumatoid, psoriatic — the systemic disease continues), severe tricompartmental OA, active infection, severe peripheral vascular disease, and any patient unable to comply with a protected weight-bearing protocol.

• Relative: age over 65 years (consider arthroplasty), BMI over 35, current smoker (doubles non-union risk), flexion contracture greater than 15°, ligamentous instability (address concurrently), significant patellofemoral arthritis for an HTO/DFO, and unrealistic patient expectations. The correction target — why you operate to a number, not to neutral. Plan on full-length weight-bearing hip-knee-ankle films. Draw the mechanical axis from the centre of the femoral head to the centre of the talus. In varus OA the axis falls medial to the knee centre, through the medial 20–30 percent of the plateau; the Fujisawa point — 62–66 percent of the lateral plateau, equivalent to 3–5° of valgus — is the target for HTO, deliberately shifting load onto the healthier lateral compartment. For a valgus DFO the target is 55–60 percent medial. Undercorrection leaves the diseased compartment overloaded and fails early; excessive overcorrection overloads the opposite compartment. The correction angle is calculated with the Miniaci or Dugdale methods, or with digital planning software (TraumaCad, Orthoview).

The goal: expose the bone through the correct approach for each osteotomy, create a biplanar cut that preserves a 1 cm hinge, open (or close) gradually to the pre-calculated correction, fix with a locking plate, and verify alignment on the table. HTO is the dominant operation and is laid out in full below; the DFO and TTO exposures and cuts follow the same principles on different bones.

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Rehabilitation — protected weight-bearing until healing is confirmed on X-ray (bridging callus, no gap widening). Opening-wedge heals more slowly than closing-wedge because of the larger bone void. | Phase | Timing | Weight-bearing | Milestones | |-------|--------|----------------|------------| | 1 | 0–6 weeks | Non/touch weight-bearing, hinged brace | ROM 0–90° by 2 weeks, full by 6 weeks; X-ray at 6 weeks | | 2 | 6–12 weeks | Progressive partial to full if callus forms | Continue ROM, closed-chain strengthening | | 3 | 3–6 months | Full by 10–12 weeks when healed | Wean brace, stationary bike, swimming | | 4 | 6–12 months | Full | Return to impact 6–9 months, sport 9–12 months | Hardware removal is elective at 12–18 months if symptomatic (medial HTO plates are superficial and often prominent); asymptomatic hardware can be left. Annual X-rays for the first 3–5 years monitor alignment and arthritis progression. Complications — recognition, prevention, management.

Five danger structures — know the location and how to protect each.

Why a knee osteotomy, not an arthroplasty? Knee osteotomy is a joint-preserving "bridge" procedure for young, active patients with isolated unicompartmental OA. In well-selected candidates it relieves pain, improves function and delays arthroplasty by roughly 10–15 years, preserving bone stock and allowing a higher activity level in the interim. Best outcomes favour age under 55 years, Kellgren-Lawrence grade 2–3 disease, accurate correction to the Fujisawa point, a normal BMI, non-smokers, and concurrent treatment of meniscal or ligamentous pathology. It is cost-effective relative to TKA in patients under 55. Most patients eventually require arthroplasty, but at an older age — and an osteotomy is not curative, it is protective. Opening-wedge versus closing-wedge HTO.

Survival and outcomes. | Procedure | 5-year survival | 10-year survival | 15-year survival | |-----------|-----------------|------------------|------------------| | HTO (medial-compartment OA) | 90–95 percent | 70–80 percent | 60–70 percent | | DFO (lateral-compartment OA) | 75–90 percent | 70–80 percent | — | | TTO (patellofemoral) | 70–80 percent good-excellent | — | — | Survival is defined as freedom from progression to arthroplasty or persistent symptoms. DFO has less data than HTO because the procedure is less frequent; both hinge on the accuracy of correction. TTO gives the best results in isolated lateral-facet lesions with maltracking and performs poorly in diffuse or panpatellar arthrosis. The Takeuchi classification of lateral hinge fractures — stratifies risk after an opening-wedge HTO and guides weight-bearing and the need for supplementary fixation.