# Improved clinical outcomes when maintaining a neutral joint line obliquity at high tibial osteotomy and subsequent total knee arthroplasty

## TL;DR

Maintaining a neutral joint line angle during knee surgeries improves patient outcomes and reduces stiffness.

## Contribution

The study shows that preserving a neutral joint line obliquity during HTO and TKA leads to better clinical results.

## Key findings

- Patients with neutral joint line obliquity had better WOMAC scores and less stiffness post-TKA.
- Proximal joint line obliquity post-TKA was more common in those with pre-TKA proximal obliquity.
- No significant difference in revision rates was found among joint line obliquity groups.

## Abstract

The primary aim was to study the impact of joint line obliquity (JLO) on clinical outcomes and survivorship in patients undergoing total knee arthroplasty (TKA) after a previous high tibial osteotomy (HTO). The secondary aim was to study how maintaining neutral JLO at both HTO and TKA affected clinical outcomes of TKA.

A retrospective review of patients undergoing TKA following valgus‐producing HTO, having a minimum 1‐year follow‐up, was performed. Using the coronal plane alignment of the knee (CPAK) classification, three groups of JLO were formed: distal JLO (<177°), neutral JLO (177–183°) and proximal JLO (>183°). Clinical outcomes were assessed using the Western Ontario and McMaster University Osteoarthritis Index (WOMAC). The level of significance was 0.05.

The study included 110 TKA (mean follow‐up: 5.8 years). Prevalence of a proximal JLO post‐TKA was higher (p < 0.05) in those with a proximal JLO pre‐TKA (40%) as compared to those with a neutral JLO pre‐TKA (13%). The odds ratio of having a proximal JLO post‐TKA was 4 (95% confidence interval: 1.4–11.1, p < 0.05) in those having a proximal JLO pre‐TKA. Revision rate in the proximal JLO post‐TKA, neutral JLO post‐TKA and distal JLO post‐TKA groups was 20%, 8% and 4% respectively, with no statistical difference (p > 0.05). Post‐TKA, the stiffness, function and total WOMAC were significantly better (p < 0.05) in patients with a neutral JLO pre‐TKA and neutral JLO post‐TKA as compared to those with a proximal JLO pre‐TKA and proximal JLO post‐TKA or a proximal JLO pre‐TKA and neutral JLO post‐TKA.

While a proximal JLO after conversion TKA did not show a statistically higher revision rate, maintaining a neutral JLO during HTO and at the time of subsequent TKA was associated with higher post‐operative clinical scores. However, further research in different and larger populations is needed to confirm these findings.

Level IV.