Introduction and Aims: A recently reported study and reports in the German lay press have indicated that there may be an increased incidence of limp following Robodoc THR. This paper presents the detailed functional aspects from the first randomised US FDA multicentre trial.

Method: The controlled randomised trial was conducted from 1994–98, with 136 hip replacements performed on 119 patients at three centres. The implants were either AML (Depuy) or Osteoloc (Howmedica). Twenty-eight patients were lost to follow-up at two years. Twenty-four month Harris hip score surveys for the remaining 108 patients – 53 Robodoc and 55 Control – were reviewed and relevant scores were tabulated for limp and use of support aids.

Results: In the Robodoc group, 45 patients had no limp and eight patients had slight to moderate limp. In the control group, 44 patients had no limp, and 11 patients had slight to moderate limp. The average Harris limp score was 10.49 for the Robodoc group and 10.24 for the control group (NS). In the use of supportive aids and canes, at 24 months, there was essentially no difference between the average of the scores. In the Robodoc group,47 patients required no aids, and six required the use of a cane. In the control group, 49 patients required no supportive aids, and six patients required the use of a cane.

Conclusions: In this randomised controlled study no statistically significant difference was found between the Robodoc and the manual method in the incidence of limp and use of supportive aids, following primary Total Hip Arthroplasty. This data is also consistent with other published studies using Robodoc and is in contrast to a recent study from one centre.