Comparison of Exeter stem offset size for total hip arthroplasty between males and females: A retrospective series of 780 hips.

Background: Many orthopaedic surgeons use a 'standard' stem offset length, typically 37.5 mm and 44 mm for females and males respectively, in total hip arthroplasty. With increasingly personalized surgery, 'standard' one-size-fits-all stem lengths may be outdated. This study aims to test whether pre-operative templating affects stem length choice and whether 'standard' stem sizes are therefore outdated.

Methods: We performed a retrospective chart review of all total hip arthroplasty patients using Stryker's Exeter cemented femoral hip system in our centre between 2016 and 2020. Demographic and surgical data were collected. Data from surgeons who templated pre-operatively were compared to data from those who did not.

Results: 780 patients were included (309 male, 471 female), average age 71.4 years (range 23-96). We found a significant difference between male and female offset lengths; more males had an offset length of 44 mm and more females had an offset length of 37.5 mm (p = 0.004). Among surgeons who did not template pre-operatively, 20.6% of female patients and 10.3% of male patients had other 'non-standard' offset lengths. Among surgeons who did template pre-operatively, the proportion of both female and male patients who had other 'non-standard' offset lengths was significantly higher (43.1% and 23.4%, respectively p < 0.05).

Conclusions: The difference between templating and non-templating surgeons' stem choice revealed significant individual variability between males and females. 'Standard' offset lengths for males and females were still used in the majority of our cohort. However, with the emergence of mainstream robotic arthroplasty, we feel that pre-operative templating has become a minimum standard.