Is a bidirectional proximal tibia osteotomy indicated for a patient with a mild varus deformity of the right knee, given an L (Lateral Distal Femoral Angle) DFA of 86.5 and an MPTA (Medial Proximal Tibial Angle) of 83.5, both slightly below the normal range of 88-90?

Bidirectional Proximal Tibia Osteotomy for Mild Varus Deformity

A bidirectional (double-level) osteotomy is likely indicated for your patient, as isolated high tibial osteotomy (HTO) alone would be appropriate in less than two-thirds of varus knees when attempting to avoid excessive overcorrection of the MPTA beyond 95°. 1

Understanding Your Deformity Pattern

Your measurements reveal a combined tibial and femoral deformity:

• LDFA of 86.5° (normal 88-90°): This indicates a femoral contribution to the varus deformity 1
• MPTA of 83.5° (normal 88-90°): This indicates a tibial contribution to the varus deformity 1
• Both angles are below normal, suggesting bifocal deformity requiring correction at both levels 1

Why Isolated Tibial Osteotomy Is Insufficient

Only 28% of patients with mechanical varus ≥3° have an isolated tibial deformity. 1 In your case, with both abnormal LDFA and MPTA values, attempting isolated HTO would result in:

• Excessive MPTA overcorrection beyond 95° if trying to achieve proper mechanical axis alignment 1
• Oblique joint line that compromises long-term outcomes 1
• Risk of creating lateral compartment overload from excessive tibial correction 2, 3

Surgical Decision Algorithm

If anatomic correction is the goal (MPTA ≤90°):

• Only 12% of varus knees can be corrected with isolated HTO 1
• 63% require double-level osteotomy 1
• Your case falls into this category given both abnormal angles

If slight overcorrection is acceptable (MPTA ≤95°):

• 57% can be corrected with isolated HTO 1
• 33% still require double-level osteotomy 1
• Your combined deformity likely still necessitates bifocal correction

Recommended Approach

Perform bidirectional osteotomy addressing both the distal femur and proximal tibia to:

• Correct the femoral component (LDFA 86.5° → target ≥85°) 1
• Correct the tibial component (MPTA 83.5° → target ≤90-95°) 1
• Achieve mechanical axis alignment of approximately 2° valgus without creating an oblique joint line 2
• Avoid excessive correction at either single level that would compromise joint biomechanics 1

Critical Technical Considerations

Target alignment should be 183-186° hip-knee-ankle angle (equivalent to 0-3° valgus), as this range provides:

• Best long-term pain relief 2
• No progression of arthritis in either compartment 2
• Angles >186° cause progressive lateral compartment degeneration 2
• Angles <183° lead to recurrent varus and medial compartment progression 2

Avoid undercorrection, which leads to:

• Recurrence of varus deformity at an average of 7 years 2
• Progressive medial compartment arthritis 2
• Only 45% good results at 10 years with inadequate correction 2

Important Pitfalls

• Do not attempt isolated HTO when both LDFA and MPTA are abnormal, as this creates excessive MPTA values and oblique joint lines 1
• Precise preoperative planning with weight-bearing full-leg radiographs is mandatory 4, 2
• Slight overcorrection is preferable to undercorrection for durability 5, 3
• If valgus deformity exceeds 12° or tibial articular surface tilt would exceed 10°, consider supracondylar femoral osteotomy instead 3