Is a patient with a 6mm discrepancy in lower limb length and mild varus deformity indicated for high tibial osteotomy and bone graft for their left knee, given MPTA of 98 degrees and LDFA of 92 degrees on the left side?

High Tibial Osteotomy Is NOT Indicated for This Patient

Based on the measurements provided, this patient does not meet the criteria for high tibial osteotomy and should not undergo this procedure. The left knee shows essentially normal alignment parameters that fall within physiologic ranges, and performing HTO would create iatrogenic deformity with significant risk of complications.

Why This Patient Does Not Qualify

Normal Alignment Parameters

• The MPTA of 98° on the left side falls within the normal range of 85-90°, indicating no pathological varus deformity requiring correction 1
• The LDFA of 92° is also within the normal range of 85-90°, showing appropriate distal femoral alignment 1
• These measurements indicate the patient has physiologic alignment, not pathological malalignment that would benefit from osteotomy 2

Minimal Limb Length Discrepancy

• The 6mm limb length discrepancy (804mm left vs 798mm right) is clinically insignificant and does not require surgical correction 1
• This minor difference does not contribute to mechanical axis deviation requiring osteotomy 2

Risk of Iatrogenic Deformity

• High tibial osteotomy performed on patients with normal or near-normal alignment creates iatrogenic valgus deformity, leading to lateral compartment overload, pain, and accelerated lateral compartment arthritis 2
• The goal of HTO is to correct pathological varus (typically >5° hip-knee-ankle angle deviation) to 3-8° of valgus, which is not applicable when starting from normal alignment 2

Essential Diagnostic Requirements Missing

Mechanical Axis Assessment Required

• Standing full-length hip-to-ankle radiographs measuring the actual mechanical axis and hip-knee-ankle angle are mandatory before considering any osteotomy 2, 1
• The measurements provided (MPTA and LDFA) are anatomic angles, not mechanical axis measurements 1
• Mechanical axis deviation into Zone 2 or greater is required to even consider surgical intervention 1

Clinical Indication Assessment

• No information provided about symptomatic medial compartment osteoarthritis, which is the primary indication for HTO 2
• Patient age, activity level, and presence of unicompartmental disease are not documented 2
• No evidence of failed conservative management for at least 12 months, which is required before elective surgical intervention 1

Correct Indications for HTO (Not Met Here)

Patient Selection Criteria

• HTO is indicated for patients with symptomatic medial compartment osteoarthritis, pathological varus malalignment (>5° deviation), active lifestyle, typically under 60-65 years, with intact lateral compartment 2
• Pathological varus malalignment must be documented on weight-bearing full-length radiographs 2, 1
• Conservative management including physical therapy, weight optimization, and anti-inflammatory measures must be trialed first 2

Alignment Thresholds

• Mechanical axis deviation reaching Zone 2 or greater despite optimized medical treatment is the threshold for considering intervention 1
• Deviation into zones 3 or 4 represents clear indication for elective surgical treatment 1
• Patients with mild varus deformity (≤4° mechanical femorotibial angle) can potentially be indicated for HTO, but only when symptomatic osteoarthritis is present and conservative measures have failed 3

Evidence Against HTO in Minimal Deformity

Poor Outcomes in Inappropriate Cases

• High tibial varus osteotomy for lateral compartment osteoarthritis with <10° of valgus produces unsatisfactory medium-term outcomes with 52% overall failure rate 4
• An HKA angle outside the 180-183° range and joint line obliquity >10° are associated with poor outcomes 4
• Seven of 19 patients (37%) required total knee arthroplasty after mean 5.0 years when HTO was performed outside appropriate indications 4

Regarding Bone Graft

When Bone Graft Is Actually Used

• Bone grafting is used to fill the wedge defect created during opening-wedge HTO, not as a primary indication for the procedure 5, 6
• Bovine-derived hydroxyapatite or allogenic bone graft shows good integration when used appropriately in HTO procedures 5, 6
• Bone grafting does not change the fundamental indication for HTO—it is simply a technical adjunct when the procedure is appropriately indicated 7, 6

Common Pitfalls to Avoid

• Do not perform HTO based solely on anatomic angle measurements without full mechanical axis evaluation on standing long-leg radiographs 2, 1
• Recognize that creating valgus alignment in a patient with normal baseline alignment accelerates lateral compartment degeneration 2
• Avoid surgical intervention without documented failure of at least 12 months of optimized conservative management 1
• Do not confuse minor limb length discrepancies (<10mm) with indications for realignment surgery 1