For certain types of long bone fracture, special inter-medullary nails can be used to secure and stabilise the fracture site. The nails are passed down the length of the ‘hollow’ medulla inside of the bone and secured with screws. Because the medulla is not uniform in diameter along the length, fractures close to the joints cannot be fully stabilised by the nail alone and full alignment cannot be achieved (as illustrated in the picture). Full alignment speeds healing and reduces post-operative complications leading to shorter hospital stays and better long term recovery. Where full alignment and stability is achieved the patient can bear weight on the limb the day after surgery allowing earlier physiotherapy which combats limb wastage and accelerates bone healing.
To combat poor alignment near the joints, the 'blocking' screw method has been developed. These blocking screws are installed at 90-degree to the bone long axis in order to effectively narrow the medulla and hence force alignment when the nail is inserted.
However, the blocking screw method is not widely used because the optimal placing of the screws can be counter intuitive. The aim of this work is to produce models of the nailing process in order to produce evidence about where the blocking screws should be placed to achieve the biomechanical benefits of the technique. A longer term aim is to use this evidence to help train surgeons in the blocking screw method and to work with clinical specialists to quantify and qualify patient and service benefits.
| Dr. Terry Dickerson |
Department of Engineering |
| Mr. Matija Krkovic |
Consultant Orthopaedic Trauma Surgeon, Cambridge University Hospitals NHS Foundation Trust |
