Axial loading of the wrist results in carpal pronation, which loads the scapholunate ligament (SLL). ECRL and FCR are carpal supinators and ECU is a carpal pronator. In this study we aim to show differential activity in the ECRL and ECU as a protective mechanism for the SLL in simulated falls.

Eight healthy volunteers were recruited for a simulated fall situation. Surface EMG was used to record muscle activity in the six major muscles that control wrist movement (FCU, FCR, ECRL, ECU, APL, ECRB) in the right forearm. The forearm skin was prepared in a standard fashion and the electrodes placed following an established protocol. Recordings were made using zero wire (Noraxon) surface EMG equipment. The data was exported and analysed using MyoResearch XP. Recordings were rectified and mean value, peak value, area under the curve and frequency were compared. Recordings were divided into five time periods from rest to post-impact.

ECRL has the most predictable and consistent response to impact of the wrist on the ground. Immediately following impact there is inhibition of the extensors and no change in flexor activity. The next phase is characterised by a ‘spike’ in ECRL activity with a less marked increase in ECRB and minimal change in ECU activity. There is decrease activity in the flexors during the ECRL peak.

The pre-peak period lasts between 5 to 10 ms. The ECRL peak period lasts between 20 to 30 ms.

We have identified that ECRL is active post fall and this response takes less than 10 ms from the time of impact. The time response is in the order of a spinal proprioceptive reflex. We were unable to identify a stretch response in the flexors that could act to trigger the ECRL response.

Introduction and Aims: Unilateral joint destruction in small joints of the hand presents a difficult challenge, particularly in younger patients. Pyrocarbon has a number of properties which may render it more suitable than metal for hemiarthroplasty in selected circumstances. We reviewed the results of our experience with PIP and MCP hemiarthroplasty utilising pyrocarbon implants to evaluate the clinical outcome in each case.

Method: Since December 2001, 10 pyrocarbon hemiarthroplasties were implanted in 10 patients. Eight were implanted into the PIP joint and two into the MCP joint. The average patient age was 34.5 years (range 19–65). Nine procedures were for trauma and one for arthrosis. The decision to implant was taken when other reconstructive options were not considered possible and the patient would otherwise have been offered arthrodesis or amputation or total joint arthroplasty. The patients were reviewed clinically to establish their range of motion, pain control and satisfaction with surgery. Radiographic review was undertaken.

Results: After an average follow-up of 13 months (range three to 23 months) all joints remain in-situ. The average arc of motion is 50.5 degrees. Average extension was minus eight degrees (range 0–20) and average flexion was 58.5 (range 15–90). There was no evidence of loosening. Erosion of the intact side of the joint was noted in only one patient. One patient was not satisfied with the final outcome.

Conclusion: The short-term results of PIP and MCP hemiarthroplasty with a pyrocarbon prosthesis show reasonable promise and this procedure merits further evaluation of its role in the treatment of unilateral joint destruction. It may be preferable to either total joint arthroplasty or fusion, particularly in the younger patient.