Introduction

Valgus producing high tibial osteotomies (HTOs) realign the tibia to off-load the medial compartment of the knee and relieve symptoms of osteoarthritis. The ‘ideal’ hip-knee-ankle (HKA) angle is estimated to be 3-6° valgus. However, up to 10% of procedures fail to come within 20% of the intended correction. Nevertheless, it remains unclear whether failing to achieve a correction of 3-6° valgus impacts the patient outcome. The aim of this systematic review was to determine whether correction angle correlates with patient reported outcome following HTO for medial knee OA.

Methods

Ovid MEDLINE, Embase, and Web of Science were systematically searched using the search terms ‘Osteoarthritis OR Knee Osteoarthritis [All Fields] AND Osteotomy OR Osteotomy OR Tibia osteotomy OR Femur Osteotomy OR Tibia proximal osteotomy [All Fields]’. Identified titles and abstracts were reviewed by two individuals. Full-text reviews were then completed by the same reviewers. Eligible studies included patients who had undergone a HTO for medial knee OA, reported pre- and post-operative HKA, and included one of the following PROMs: Oxford knee score (OKS), visual analogue score (VAS), knee osteoarthritis outcome score (KOOS), and EQ-5D. The quality of included studies was reviewed using the National Institute of Health Quality Assessment Tool. Finally, all pertinent data from eligible studies were extracted for synthesis and analysis. Spearman correlations were carried out where appropriate to investigate the relationship between variables. PROSPERO ID: CRD42019135467.

Results

Thirty-nine articles fulfilled the inclusion criteria. Eleven articles compared two cohorts of HTO patients, resulting in a total of 50 cohorts (2,341 patients) with a mean follow-up of 46.8 months. VAS was reported in 22 studies (56.4%), OKS in 9 (23.1%), KOOS in 12 (30.8%) and EQ-5D in 2 (2.6%). Most studies were of Fair quality (56.4%). None were of Poor quality.
The mean pre-operative HKA angle was 7.1±1.7° varus. This was corrected to 2.3±1.7° valgus at final follow-up.
On average, all PROM scores increased with clinical and statistical significance post-operatively. Spearman correlations revealed a weak relationship between HKA alignment and post-operative VAS (r = 0.11). However, greater changes in knee alignment led to larger improvements in VAS and OKS scores (r = 0.50 & r = 0.33, respectively). Patients exhibiting greater degrees of valgus alignments post-operatively were also shown to score better in the OKS scores (r = 0.48), and in all KOOS domains except for KOOS Activity and KOOS Sports. However, those who experienced greater changes in alignment were found to show larger improvements in the Activity and Sports domains.

Conclusion

The average patient included in this review did not achieve the ‘ideal correction’ of 3-6° valgus post-operatively. Nevertheless, statistical and clinical improvements in PROM scores were consistently reported in the literature. This suggests that the ‘ideal correction’ may be more flexible than 3-6°. However, our correlation analyses infer that patients who experienced greater changes in alignment following HTO showed larger improvements in scores post-operatively, especially in pain and activity domains.