Observational study of a new modular femoral revision system.

BACKGROUND

The uncemented Arcos Modular Femoral Revision System (ARCOS) is a new comprehensive, press-fit revision design. The modular design offers a wide range of possible combinations to accommodate different variations of anatomy and bone stock. The ARCOS is made by a proximal body and a distal stem. As probably the only ones worldwide we predominantly use a combination of body and stem which supports proximal fixation and load, since this mimics the concept of the primary total hip arthroplasty with proximal weight-bearing, leading to bone stock preservation and no stress shielding or thigh pain.

AIM

To evaluate the early results after femoral revision in a consecutive series of patients undergoing surgery over 3 years.

METHODS

We included 116 patients in the study. They were operated in the period August 2011 to December 2014 and we got a clinical mean observation time of 4 (0.5-6) years. Clinical and radiographical follow-up included present function of the hip assessed by Harris Hip Score, Oxford Hip Score, and EQ5D (measure of health outcome). Of the 116 patients, 17 died in the interim and were consequently included only in the implant survivorship analysis; 46 patients attended the follow-up control.

RESULTS

In total 6 (5%) hips were re-revised due to infection ( = 3), fracture ( = 2) or subsidence ( = 1). No patient was re-revised due to aseptic loosening. The 1-, 2- and 5-year probability of implant survival (95%CI) were 97% (93%-100%), 97% (93%-100%) and 96% (92%-99%), respectively. In this cohort 95 patients received a combination of a proximal broach and a distal curved and slotted stem (BS), aiming for proximal fixation and load bearing; 21 patients received a different combination. When comparing these two groups the BS-group had a 5-year implant survival probability (95%CI) of 97% (93%-100%) compared with the group of other combinations with a 5-year implant survival probability (95%CI) of 90% (78%-100%) ( = 0.3). Our regression analysis showed that periprosthetic fracture as an indication for the ARCOS operation was the only significant negative outcome predictor. The mean Harris Hip Score result (100 points being best) was 83 (range 5-98). The mean Oxford Hip Score result (48 points being best) was 40 (range 19-48).

CONCLUSION

The early results of the ARCOS are promising compared with similar studies. We encourage the use of the BS combination whenever the bone stock proximally is adequate.