Published online Mar 18, 2020. doi: 10.5312/wjo.v11.i3.167
Peer-review started: November 11, 2019
First decision: November 22, 2019
Revised: December 2, 2019
Accepted: March 1, 2020
Article in press: March 1, 2020
Published online: March 18, 2020
The uncemented ArcosTM 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.
With this study we wanted to evaluate the early results after femoral revision with the new ARCOS in a consecutive series of patients who underwent surgery over a period of 3 years. We also found it very interesting to find out whether a specific ARCOS combination is performing superiorly compared to the most widely used to date.
In the 1990’s Denmark, we had a scare scenario with bone cement not tested on humans before clinical implementation. It became an arthroplasty-scandal and led to financial compensation to thousands of patients. We became fearfully aware how essential it is to evaluate the efficacy of new technology or new design. With this study we aimed to evaluate the early results after surgery with ARCOS, focusing on reoperation rate and clinical results.
In this retrospective observational study with clinical and radiographical follow-up, we included 116 patients. 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. The only reason for follow up shorter than 2 years was death.
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). Compared to the post-surgery X-rays in two planes, the most recent anterior-posterior X-ray was classified as: Stationary conditions, subsidence, fracture, re-revision or clearing in the Gruen Zones.
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. Statistics: Non-parametric statistics was used for risk factors between the re-revision-group and the no-re-revision-group. Competing risk and Kaplan Meier survival analysis were used for the ARCOS stem combination(s). For preoperative factors multivariate cox method was used to estimate stem failure.
In total 6 (5%) hips were re-revised due to infection (n = 3), fracture (n = 2) or subsidence (n = 1). No patient was re-revised due to aseptic loosening. The 1-, 2- and 5-year probability of implant survival (95%CI) was 97% (93%-100%), 97% (93%-100%) and 96% (92%-99%) respectively. I 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%) (P = 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 being best) was 83 (range 5-98). The mean Oxford Hip Score result (48 being best) was 40 (range 19-48).
Perioperatively the bone stock was classified according to Saleh et al and we found 48% with type II, 34% with type I, 14% with type III and 2% with type IV and V respectively. At the radiographical evaluation we found 84 hips with stationary conditions, 6 were re-revised, 2 had a cup-revision, 16 had some subclinical subsidence or clearing, 2 had a healed fracture and 6 patients had no X-rays for comparison.
Our study describes short-term results and the primary outcome parameter being evaluated is the failure rate. Our findings support the hypothesis that an ARCOS combination with proximal load-bearing and fixation reduces the reoperation rate. Of course it is interesting to further investigate how the long-term outcome with these prostheses is, especially since the tendency worldwide is to use the concept of distal fixation.
We find survival of the ARCOS prosthesis of 96% in total after 5 years very satisfying. We encourage surgeons to consider using the combination for proximal load and fixation for better preservation of bone stock, less stress shielding and less thigh pain in order to obtain a situation as close to a primary total hip as possible. It is essential to evaluate the efficacy of new technology or new designs. The ARCOS stem is functioning well and has the character of a so-called “safe procedure”. Proximal fixation and load-bearing is desirable in both primary total hip arthroplasty and in revision total hip arthroplasty to reduce the incidence of stress shielding and thigh pain, and preserve bone stock.
The ARCOS is an uncemented stem design for revision hip arthroplasty. It is combined by a proximal body and a distal stem and in theory more than 200 combinations of proximal body and distal stem exist. In reality two combinations or concepts apply for the majority of revision cases. These are: (1) A broach proximal body + a distal slotted and curved stem (proximal load and fixation) and (2) A cone proximal body + a distal STS (distal load and fixation). The ARCOS is performing above acceptable. We recommend a differentiated use of the various concepts depending on the individual bone quality and bone stock.
We ask surgeons to consider using the ARCOS combination for proximal load and fixation that mimics the primary total hip arthroplasty whenever bone stock is adequate. We are currently investigating how other ARCOS-populations in other hospitals are doing and what combinations of proximal body and distal stem they have received. A randomized controlled trial would be lovely, and it might be possible with a multicenter study setup.