Hip offset parameters and functional outcomes following total hip arthroplasty: association with performance, strength, and patient-reported outcomes

Hip offset parameters and functional outcomes following total hip arthroplasty: association with performance, strength, and patient-reported outcomes

Background
Restoring native hip offset is considered important for optimizing function following total hip arthroplasty (THA), yet the relationships between offset parameters and postoperative outcomes remain inconsistently reported. This study investigated the associations between femoral offset (FO), acetabular offset (AO), and global offset (GO) with functional mobility, hip abductor strength, and postoperative pain.

Methods
A total of 69 patients (mean age: 69.6 years) with unilateral THA were assessed at an average follow-up of 3.3 years. Offset parameters were measured radiographically and classified as decreased, restored, or increased relative to the contralateral hip. Functional outcomes were assessed using the Timed Up and Go (TUG) test and the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC). Hip abductor strength was measured via manual dynamometry, and pain was evaluated using a visual analog scale (VAS).

Results
No significant associations were found between offset parameters and TUG or WOMAC scores. However, patients in the decreased GO group exhibited significantly reduced hip abductor strength in the operated limb, with this asymmetry persisting over time. Additionally, both FO and AO in the non-operated hip were significantly associated with VAS pain scores, and their combined effect appeared to amplify pain perception. These relationships also changed over time during the follow-up period.

Conclusions
While offset restoration did not relate to global functional tests such as TUG or WOMAC, patients with decreased global offset exhibited persistent abductor weakness, and contralateral offset parameters were associated with pain perception. These findings highlight the complexity of the relationship between offset and functional recovery and emphasize the importance of accurate offset restoration and bilateral biomechanical assessment in optimizing long-term outcomes following THA.