Over the last decade Computer Assisted Orthopaedic Surgery (CAOS) has emerged particularly in the area of minimally invasive Uni-compartmental Knee Replacement (UKR) surgery. Image registration is an important aspect in all computer assisted surgery including Neurosurgery, Cranio-maxillofacial surgery and Orthopaedics. It is possible for example to visualise the patient's medial or lateral condyle on the tibia in the pre-operated CT scan as well as to locate the same points on the actual patient during surgery using intra-operative sensors or probes. However their spatial correspondence remains unknown until image registration is achieved. Image registration process generates this relationship and allows the surgeon to visualise the 3D pre-operative scan data in-relation to the patient's anatomy in the operating theatre.

Current image registration for most CAOS applications is achieved through probing along the articulating surface of the femur and tibial plateau and using these digitised points to form a rigid body which is then fitted to the pre-operative scan data using a best fit type minimisation. However, the probe approach is time consuming which often takes 10–15 minutes to complete and therefore costly. Thus the rationale for this study was to develop a new, cost effective, contactless, automated registration method which would entail much lesser time to produce the rigid body model in theatre from the ends of the exposed bones. This can be achieved by taking 3D scans intra-operatively using a Laser Displacement Sensor.

A number of techniques using hand held and automated 3D Laser scanners for acquiring geometry of non-reflective objects have been developed and used to scan the surface geometry of a porcine femur with four holes drilled in it. The distances between the holes and the geometry of the bone were measured using digital vernier callipers as well as measurements acquired from the 3D scans. These distances were measured in an open source package MESHLAB version 1.3.2 used for the interpretation, post-processing and analysis of the 3D meshes. Absolute errors ranging from of 0.1 mm to 0.4 mm and the absolute percentage errors ranging from 0.48% to 0.75% were found. Additionally, a pre-calibrated dental model was scanned using a 650 nm FARO™ Laser arm using the global surface registration approach in Geomagic Qualify package and our 3D Laser scanner. Results indicate an average measurement error of 0.16 mm, with deviations ranging from 0.12mm to −0.13 mm and a standard deviation of 0.2 mm. We demonstrated that by acquiring multiple scans of the targets, complete 3D models along with their surface texture can be developed. The overall scanning process, including time required for the post-processing of the data requires less than 20 minutes and is a cost-efficient approach. Moreover, the majority of that time was used in post processing the acquired data which could be potentially reduced through the use of bespoke application software. This project has provided proof of concept for a new automated, non-invasive and cost efficient registration technique with the potential of providing a quantitative assessment of the articular cartilage integrity during lower limb arthroplasty.

In 2012 collagenase Clostridium histolyticum (Xiapex) was approved by the SMC for restricted use for the treatment of Dupuytren's contracture. Xiapex was approved on a case by case basis for patients with a palpable pretendinous cord, giving rise to MCPJ contracture of greater than 30 degrees. As of September 2012 we began to offer Xiapex injections to patients in Ayrshire who enquired about the injection, and met the SMC criteria.

To date injections have been performed on 3 patients, in a total of 7 digits. Patients were assessed prior to injection and manipulation, with the degree of contracture recorded and DASH scores noted. Each patient then underwent a standard injection of 0.58 mg of Xiapex. 48 hours post injection each patient underwent manipulation under local anaesthetic, with contractures remeasured, pain scored using a visual analogue scale and complications noted. Each patient was then reviewed at 4 weeks post injection where the residual degree of contracture was recorded and a further DASH score completed.

Mean contracture at the MCPJ prior to injection was 57° (range 34–80), and mean DASH score of 20.8 (range 16.7–24.2). Following manipulation mean residual contracture at the MCPJ measured 21° (range 18–28). The average pain score following was manipulation was rated at 1.1. Mild bruising and swelling were reported in all cases following injection, and manipulation resulted in 2 minor skin tears. At the 4 week review prolonged improvement of contracture was achieved with a mean residual contracture of 14° (range −2–40); with a significant improvement in DASH scores – mean 0.6 (range 0–1.8)

Despite small numbers, we have found Xiapex injections to be a successful and well tolerated treatment for moderate Dupuytren's disease. Further follow up is required to assess the longevity of the correction and ensure the cost effectiveness of Xiapex.