Is a left medial lateral distal femoral angle (mLDFA) of 88 and a left medial medial proximal tibial angle (mMPTA) of 83 an indication for unilateral partial osteotomy, specifically high tibial osteotomy with bone graft?

High Tibial Osteotomy for Left mLDFA 88 and Left mMPTA 83

Based on the radiographic measurements provided (left mLDFA of 88 and left mMPTA of 83), a unilateral partial osteotomy, specifically high tibial osteotomy (HTO) with bone graft, is appropriate for correction of this knee deformity.

Analysis of Deformity Parameters

The key measurements to consider in this case are:

• mLDFA (mechanical lateral distal femoral angle): 88° (normal range 85-90°)
• mMPTA (medial proximal tibial angle): 83° (normal range 85-90°)

These values indicate:

• The femoral component (mLDFA) is within normal limits
• The tibial component (mMPTA) shows varus deformity (below normal range)

Surgical Decision Algorithm

1. Identify the primary deformity location:

   • mLDFA 88° = normal femoral alignment
   • mMPTA 83° = tibial varus deformity
   • Conclusion: Deformity is primarily tibial

2. Determine appropriate osteotomy type:

   • When deformity is primarily tibial (low mMPTA) with normal femoral alignment (normal mLDFA): HTO is indicated 1
   • When deformity is primarily femoral or combined: consider distal femoral osteotomy (DFO) or double-level osteotomy

3. Evaluate correction goals:

   • Target mMPTA: 87-90° (anatomic correction)
   • Avoid overcorrection of mMPTA >95° as this creates joint line obliquity 1
   • Maintain mLDFA within 85-90° range 2

Evidence-Based Rationale

Recent research demonstrates that isolated HTO is appropriate when the deformity is primarily tibial in nature. According to a study by Hinterwimmer et al. 1, when the mMPTA is below normal range (as in this case at 83°) while the mLDFA is within normal range (as in this case at 88°), a tibial osteotomy is the preferred approach.

Importantly, research shows that overcorrection of the mLDFA (>90°) in varus realignment osteotomies leads to inferior clinical outcomes 2. Since this patient's mLDFA is already normal at 88°, maintaining this angle while correcting the tibial deformity is optimal.

Surgical Considerations

• Bone graft: Recommended to promote healing at the osteotomy site
• Fixation method: Locking plate fixation provides stable fixation for the osteotomy
• Correction amount: Target correction of approximately 4-7° to achieve normal mMPTA (87-90°)

Potential Pitfalls and Complications

1. Overcorrection risk: Avoid excessive correction of mMPTA >95° as this creates joint line obliquity and poorer outcomes 1
2. Undercorrection risk: Insufficient correction may lead to persistent symptoms and accelerated osteoarthritis
3. Joint line obliquity: Must be avoided for optimal clinical outcomes 2
4. Delayed union: More common in smokers and patients with metabolic disorders

Conclusion

The radiographic parameters (mLDFA 88° and mMPTA 83°) indicate a primarily tibial varus deformity with normal femoral alignment. This pattern is ideally treated with a unilateral partial osteotomy, specifically high tibial osteotomy with bone graft. This approach addresses the deformity at its anatomical source while avoiding unnecessary femoral correction, which would risk creating joint line obliquity and inferior clinical outcomes.