MPTA Values of 83-84° Are NOT Indications for High Tibial Osteotomy
MPTA (Medial Proximal Tibial Angle) values of 83° and 84° represent normal to near-normal tibial alignment and are contraindications for high tibial osteotomy, not indications for it. Performing HTO on these patients would create iatrogenic valgus deformity with serious complications 1.
Understanding Normal MPTA Values
- Normal MPTA is 85-90°, with pathological varus malalignment defined as MPTA <85° 2
- Your patient's bilateral MPTA values of 83° (right) and 84° (left) fall just below the normal threshold but do not represent the severe deformity that warrants surgical correction 1
- These values indicate minimal varus alignment, not the pathological varus that HTO is designed to correct 1
Why HTO Is Contraindicated Here
High tibial osteotomy is specifically NOT indicated for patients with normal or near-normal alignment angles 1. The American Academy of Orthopaedic Surgeons explicitly warns that:
- HTO in patients without pathological varus creates iatrogenic valgus deformity 1
- This leads to lateral compartment overload, pain, and accelerated lateral compartment arthritis 1
- The procedure shifts load from medial to lateral compartment—inappropriate when alignment is already near-normal 1
Actual Indications for HTO
High tibial osteotomy requires ALL of the following criteria 1:
- Symptomatic medial compartment osteoarthritis with intact lateral compartment 1
- Pathological varus malalignment (typically >5° varus on hip-knee-ankle angle measurement) 1
- Active lifestyle, typically age <60-65 years 1
- Goal correction to 3-8° of valgus, not applicable when starting from near-normal alignment 1
Regarding Bone Grafting
The question about bone grafting is moot since HTO is not indicated, but for completeness:
- Opening-wedge HTO without bone graft is recommended for gaps up to 14mm, avoiding unnecessary morbidity 3, 4
- Meta-analysis shows no significant difference in complications or clinical outcomes between autograft, allograft, or no graft 4, 5
- Autograft promotes higher union rates but doesn't improve functional outcomes 6
- The International Journal of Surgery recommends autogenous bone graft when osteotomy IS indicated, particularly for complex deformity corrections 2
Critical Pitfall to Avoid
Do not confuse MPTA measurement with the indication for surgery. The presence of a slightly low MPTA value does not automatically warrant correction 1. You must have:
- Standing full-length hip-to-ankle radiographs to measure actual mechanical axis 1
- Clinical symptoms from medial compartment disease 1
- Failed conservative management including physical therapy and weight optimization 1
- Pathological varus deformity (not borderline values) 1
Recommended Action
- Obtain standing full-length hip-to-ankle radiographs to measure the complete mechanical axis and hip-knee-ankle angle 1
- Assess for presence and location of osteoarthritis to determine if any pathology exists 1
- Evaluate ligamentous stability and meniscal integrity 1
- Trial conservative management if osteoarthritis is present 1
- Do not proceed with HTO based solely on MPTA values of 83-84° 1