Why bifocal osteotomy is needed in certain knee deformities
When a lower-limb deformity involves two distinct bone segments (for example, femoral and tibial components), a single-level correction may leave residual misalignment or create undesirable joint-line obliquity. This chapter argues the case for bifocal osteotomy (correction at two levels) to restore joint geometry and optimise load distribution.
How to analyse complex deformity for bifocal correction
The authors outline a rigorous approach:
- Use full-length standing radiographs to assess the mechanical axis and segmental angles (mLDFA for femur; MPTA for tibia).
- Identify joint line convergence angle (JLCA) to factor in intra-articular and soft-tissue contributions.
- Determine whether correction must occur at one or two levels: if both mLDFA and MPTA deviate >3° of normal, a bifocal osteotomy is indicated.
- Plan hinge locations, sequence of cuts, and fixation strategy accordingly.
What the technique involves in practice and what outcomes are achieved
Bifocal osteotomies are technically more demanding:
- Surgical exposure and instrumentation must allow two osteotomies in the same limb (distal femur + proximal tibia).
- Precise sequencing is critical: correction at one level influences the other; planning must account for interdependence.
- Early literature suggests that when properly executed, bifocal osteotomy improves alignment, joint-line orientation, and may enhance longevity of correction.
- Complication risks are higher compared to monofocal osteotomy—hinge fracture, non-union, neurovascular exposure at femoral level demand careful technique.
How this influences surgical decision-making and patient management
Selecting between monofocal vs bifocal osteotomy requires:
- Recognising the origin of deformity: femoral, tibial, or combined.
- Acknowledging that simpler interventions (one-level correction) may suffice for mild, isolated deformities, but not for combined ones.
- Understanding that bifocal correction aims not only for improved alignment but for preserving optimal joint-line orientation and biomechanical load distribution.
- Ensuring that patients are advised of increased complexity, potential for longer rehab and slightly higher risk—but also potentially better anatomical restoration.
Key take-away messages for clinicians
- When both femoral and tibial segments show significant deformity, a bifocal osteotomy may provide superior anatomical correction compared to single-level approaches.
- Pre-operative deformity analysis must include segmental angles (mLDFA, MPTA), JLCA, and hinge planning to determine correct surgical strategy.
- While technically demanding, bifocal osteotomy may enhance joint-preservation outcomes in younger, active patients when executed properly.
- Surgical teams should ensure the required skills, instrumentation and rehabilitation protocols are in place before choosing this option.
