High dislocation cumulative risk in THA versus hemiarthroplasty for fractures.

BACKGROUND: Although not all elderly patients with femoral neck fractures are candidates for THA, active, mentally competent, independent patients achieve the most durable functional scores with THA compared with hemiarthroplasty. However, a relatively high frequency of early or late dislocation could reduce the potential benefits with THA.

QUESTIONS/PURPOSES: We asked whether the incidence of first-time, recurrent dislocation, and revision differed in patients with hip fractures having THA or hemiarthroplasty.

PATIENTS AND METHODS: We retrospectively reviewed 380 patients with hip fractures (380 hips) who underwent THAs between 1995 and 1999, and compared them with 412 patients with hip fractures (412 hips) who underwent hemiarthroplasties between 1990 and 1994. The mean followup was 8 years (range, 1-20 years).

RESULTS: THA had a higher early risk of first-time dislocation and a higher late risk: 19 (4.5%) of the 412 hips treated with hemiarthroplasty had at least one dislocation whereas 30 (8.1%) of the 380 hips treated with THA had at least one dislocation. The cumulative number of dislocations at the most recent followup (first time and recurrent dislocations) was 58 (13%) for the 380 THAs and 22 (5%) for the 412 hemiarthroplasties. At the 10-year followup, eight THAs (2%) had revision (six recurrent dislocations, two loosenings), and 42 hemiarthroplasties (10%) had revision (40 acetabular protrusions, one recurrent dislocation).

CONCLUSIONS: The risk of revision for recurrent dislocation increases with THA, but it remains lower than the risk of revision for wear of cartilage and acetabular protrusion in hemiarthroplasty.

LEVEL OF EVIDENCE: Level III, therapeutic study. See the Guidelines for Authors for a complete description of levels of evidence.