INTRODUCTION

Simulation plays an important role in surgical education and the ability to perfect surgical performance. Simulation can be enhanced by adding various layers of realism to the experience. Haptic feedback enhances the simulation experience by providing tactile responses and virtual reality imagery provides an immersive experience and allows for greater appreciation of three-dimensional structures. In this study, we present a proof-of-concept haptic simulator to replicate key steps of a cervical laminoplasty procedure. The technology uses affordable components and is easily modifiable so that it can be used from novice through to expert level. Custom models can be easily added ensuring the simulator can be used in a wide range of orthopaedic applications from baseline education through to day of surgery pre-operative simulation.

Non-seated ceramic inserts have recently been identified as a common phenomenon in one popular modular ceramic system (16.4% of cases in Langdown et al. 2007. JBJS 89B (3):291–295). A preliminary audit at Tauranga Hospital demonstrated the same issue. However, most X-rays didn’t allow confirmation or exclusion of the problem.

A preliminary review of post-operative films of patients receiving modular ceramic acetabular implants at Tauranga Hospital was undertaken. A radiolucent jig was constructed to take images of three different modular ceramic acetabular systems. Images isocentered on the implants (seated & non-seated) were taken with variation in view given of the cup (rotation and plane of the X-ray beam relative to the implant face). Registrars & consultants were tested on their ability to detect non-seating on these images.

Two out of three acetabular systems showed non-seating in patients. Most films reviewed did not allow definitive decisions to be made about ceramic insert seating. The true incidence of non-seating in the arthroplasty population receiving modular ceramic implants is thus unknown. The images of the three systems taken in the radiolucent jig show the ability to detect non-seating is multifactorial. Implant specific differences in the shell and liner systems radiologic profile influence detection and education of surgeons may improve the chances of detection. The presence of the head of the femoral component limits detection of non-seating. The plane of the X-ray beam relative to the face of the cup along with the rotation of the non-seated region relative to the beam strongly influence detection. The plane of the X-ray beam relative to the face of the inserted acetabular component can be altered in post-operative films.

Typical post-arthroplasty hip films fail to consistently identify the occurrence of non-seating of modular ceramic acetabular inserts. Suggesting the true incidence remains unknown. Standard post-operative imaging needs to change to be confident of exclusion of this phenomenon in patients receiving modular ceramic implants.

An experimental study was performed in order to investigate methods of preparation and mechanical properties of a potential bone graft substitute. This new composite material consists of porous hydoxyapatite coated with oxidised cellulose.

Porous hydoxyapatite has excellent osteoconductive properties and promising strength characteristics. Drawbacks include its lack of osteoinductive properties and its brittle nature. Oxidised cellulose can be functionalised to provide binding sites for proteins, drugs and cells, which would allow for increased osteoinductive activity. It has good tensile strength. By creating a composite of these two substances, it was proposed that a graft substitute could be created.

Hydroxyapatite samples were formed by processing and sintering bovine cancellous bone. A method was devised by which cellulose was brought into solution and infiltrated into hydoxyapatite samples. The cellulose was then regenerated (cured) and oxidised.

Infrared spectrometry confirmed the desired chemical reactions took place and that oxidised cellulose was formed. Scanning electron microscopy confirmed that the three-dimensional structure of the hydroxyapatite was satisfactorily coated. Crush testing showed that infiltrated samples were less brittle and more likely to hold their shape than control samples.

Further development and testing is required to assess this composite material for its biological activity and potential as a bone graft substitute.