Purpose

The ‘ideal’ hip-knee-ankle (HKA) angle following high tibial osteotomy (HTO) is estimated to be 3-6° valgus. It remains unclear whether the achieved correction angle correlates with functional outcomes and whether failing to achieve 3-6° valgus post-operatively impacts these outcomes. This systematic review addressed these gaps in the literature.

Methods and Materials

Ovid MEDLINE, Embase, and Web of Science were systematically searched (between database inception and 2020). Studies investigating valgus-producing HTO for osteoarthritis were eligible if they reported at least one biomechanical variable of the knee or gait, and the HKA or femorotibial angle (FTA) pre- and post-operatively. The quality of included studies was reviewed using the National Institute of Health Quality Assessment Tool. Spearman correlations were performed where appropriate to investigate the relationship between variables. PROSPERO ID: CRD42019135467.

Results

Forty-six studies reporting 58 cohorts were included. Knee range of motion (ROM) was reported in 35 studies, at least one kinematic variable of gait in 5, at least one spatio-temporal parameter of gait in 10, and at least one kinetic variable of gait in 8.

The HKA and FTA angles were corrected from 7.5±2.4° and 2.5±2.4° varus to 2.5±2.5° and 8.5±2.4°valgus, respectively.

Many variables trended towards non-pathological values post-operatively. Greater changes in alignment after HTO was associated with larger improvements in walking speed and peak knee valgus during gait (r = 0.72 & r = 1.00). Limb alignments that were of greater valgus degrees also showed lower peak external knee adduction moments post-operatively (r = -0.85).

Conclusion

The average cohort included in this review did not achieve the ‘ideal correction’ of 3-6° valgus post-operatively, but HTO resulted in sufficient knee ROM for activities of daily living and improved gait biomechanics. This suggests the ‘ideal correction’ of HTO with respect to functional outcome is more flexible than 3-6°.