Modular Versus Monoblock Hemiarthroplasty in Trauma: A 5-Year Retrospective Analysis of Radiographic and Clinical Outcomes

Abstract

Displaced intraarticular neck of femur fractures for low-demand patients are primarily managed with hemiarthroplasty. The optimal implant design for modularity is unclear. Globally and within Australia, the use of monoblock implants varies significantly by location; however, monoblock use is decreasing in Australia in favour of modular systems, with little evidence-based explanation. This study aimed to compare the radiological and clinical outcomes of monoblock and modular hemiarthroplasties. This retrospective cohort study involved patients who underwent hemiarthroplasty for neck-of-femur fractures between 2009 and 2013 at the Gold Coast University Hospital. Leg length and femoral offset were measured from post-operative pelvic radiographs. Revision and mortality rates were extracted from hospital medical records and Australian Joint Registry data. A total of 249 patients were evaluated (112 with modular and 147 with monoblock implants). Patient demographics were comparable between the treatment groups; however, the monoblock group comprised significantly older persons. No between-group differences in leg length discrepancies were identified. Femoral offset was under-restored on average by 5.86mm (p<0.05) compared to the uninjured side within the monoblock group. Mortality rates were significantly higher in the monoblock group (23% vs 12%, P=0.026) at the 1-year mark. No significant between-group differences were found in 30-day mortality, length of stay, or revision rates. Modular hemiarthroplasty was superior for restoring offset in our cohort, but no group differences were noted for leg length. While modular implants seemed better for restoring normal hip anatomy and were associated with a lower 1-year mortality rate, no other advantages were found.