Abstract
Introduction
Arthrodesis is usually offered to patients in whom a two stage exchange arthroplasty has already failed or is likely to fail because of local factors (such as soft tissue damage, bone loss or poor perfusion), or because of systemic conditions which categorise the patient as a C-host (e.g. immune deficiency, diabetes and malnutrition). In other words arthrodesis is selected for patients with the worst prognosis.
Method
I use an intramedullary nail extending from trochanter to just above the ankle which is locked distally only. The nail is curved with an arc of a 2 meter radius. This conforms to the shape of the femur and when passed through to the straight tibia it ends against the posterior cortex of the distal tibia where the bone is thickest. It creates an angle of between 9° and 11° of flexion at the knee. The nail is bent into 5° of valgus at the point where the femur and tibia meet. This allows the two bones to coapt, dynamise and unite. The procedure is performed in two stages. At the first every effort is made to eradicate the infection by debridement and appropriate local and systemic antibiotics. The nail is inserted at the second procedure and again every effort is made to deal with infection. If infection persists one can easily remove the nail when the knee has fused, and repeat the attempt to eradicate the infection in better circumstances.
I have devised a scoring system in order to evaluate the eradication of infection based on clinical grounds, laboratory investigations and radiological examination. This allows for the fact that cure of an infection is not based on any one parameter
Results
I have performed such an arthrodesis in 99 patients. Fusion occurred in 74% of those who had more than six months follow-up. The affected limb was shortened on average by 4 cm. After nailing, pain was relieved in 80% of patients using a sliding scale.
Using the scoring system, 31% were definitely cured of infection, 34.5% were intermediate and 34.5% definitely failed. 29 patients had their nail removed and the infection was re-addressed. Using the same evaluation system 12 (24%) were definitely cured, 12 (24%) had a probable cure and 5 (18%) remained infected. This gives an overall eradication of infection of 84%.
In 4 patients apparent union of the knee broke down resulting in a jog of movement at the knee. Three of these patients were made comfortable with a gaiter to support the knee. One had his knee re-fixed with a long intramedullary nail. Three nails fractured in situ. In one of these patients the nail had locking screws proximally and distally which prevented dynamisation and union. In the other two non-union was apparent and the nail sustained a fatigue fracture.
NO DISCLOSURES
