The anterior supine intermuscular (ASI) approach enables total hip arthroplasty (THA) without dissection of muscles or insertions. This could be beneficial in patient recovery and satisfaction. Study-aim was to assess the learning-curve for the ASI-approach and show short-term results.

Two surgeons performed uncemented THA on 23 (17 and six respectively) consecutive patients. The Taperloc stem, Recap-cup and Magnum head (Biomet, Warsaw, USA) were used. THA was performed without the use of a traction-table. Data was gathered till 3 months follow-up.

Average patient age was 61 years (36–74), ASA-classification was two (one-four). There was a decrease in surgical time from 140 at the beginning to 80 minutes at the end of our series. Average blood-loss was 788 ml. Three patients received erythrocyte-transfusion. Minor non-orthopaedic complications all resolved within 48 hours. Average length of stay was five-and-a-half days. Functional score-lists showed improvement comparing pre-operative scores with scores on 12 weeks follow-up: Harris-Hip-Score from 56 to 94, Oxford-Hip-Score from 43 to 19, Hip-disability-and-Osteoarthritis-Outcome-Score from 109 to 18. On six weeks follow-up 65% and on 12 weeks 100% of patients showed unaided mobilisation. At follow-up we saw one superficial wound-infection, one partial non-disabling sartorius-lesion, one paraesthesia and one transient anaesthesia of the lateral femoral cutaneous nerve area.

ASI-approach for uncemented THA showed good results and rapid patient-mobilisation. This may in part be due to the non-dissecting of muscles or insertions, thus non-compromising the propriocepsis. Off course tissue-damage occurs, though this is likely to be of a fast reversible nature. There were no serious adverse events. We saw a rapid decline in session-duration suggesting a moderate learning-curve. Further research will have to prove the beneficiality of the ASI-approach.

Aseptic loosening of the total TMC joint prosthesis occurs frequently and may depend on the design of the prosthesis. Numerous TMC prosthesis designs are available, and new designs are being developed and tested. One of the problems in the clinical studies of TMC prostheses is identifying and predicting prosthetic loosening at an early stage. Roentgen Stereophotogrammetric Analysis (RSA). allows assessment of three-dimensional micromotion of orthopaedic implants with high accuracy. Early micromotion (in the first two postoperative years) of most prostheses is strongly correlated with the development of aseptic loosening. We studied if RSA assessment was possible after total TMC joint arthroplasty.

In five cadaveric hands the TMC joint was replaced by the SR-TMC prosthesis. Tantalum beads of 0.8 mm were implanted in the trapezium and first metacarpal bone without extending the standard surgical exposure. The metacarpal prosthesis component was provided with 0.5 mm beads. A three-dimensional surface model of the trapezium component of the SR-TMC prosthesis was prepared to facilitate model-based RSA. After the surgical procedure, RSA radiographs were made of all hands in two commonly used positions for imaging of the TMC joint. The number of visually detected markers for each bone/implant was recorded. Of one cadaver hand, RSA radiographs were made in ten different positions to calculate the measurement error of the performed technique.

For the metacarpal bone, all beads were visible in all positions and both (L+R) RSA radiographs. For beads in the polyethylene metacarpal prosthesis component three beads seem sufficient, however in exceptional cases the most proximal placed bead might be invisible due to overprojection by the metal trapezium prosthesis component. Therefore the X-rays should be carefully checked at the radiology department before the patient leaves the ward. Alternatively, an extra bead can be placed in the prosthesis, although this is a lesser option due to possible weakening of the component caused by the placement of the beads. The use of different sizes of beads (0.5/0.8 mm) in the metacarpal bone and metacarpal prosthesis made the interpretation for the analyser easier

The accuracy analysis is currently carried out. First results of these measurements are promising and placement of tantalum beads for RSA analysis during TMC-joint replacement seems feasible.