Purpose of Study We present a method of treating these infected humeral shaft non-unions with an open debridement procedure followed by stabilisation with the Ilizarov frame.

Materials Thirteen infected non-unions of the humerus in adult patients have been treated by this method. Ten patients have completed their treatment and three are still undergoing treatment.

The site of the non-union is approached through the pre-existing scar and any remaining metalwork is removed. The ends of the non-union are mobilised and bone is resected from both ends until there is fresh bleeding. The two bone ends are fashioned such that one will fit as a spike inside the medullary cavity of the other. The bone ends are held in position with two temporary K wires until the frame has been applied.

A standard four ring Ilizarov frame is applied with Rancho pins in the proximal humerus and a half ring in the distal humerus. The temporary K wires are removed and the frame is compressed to increase the contact between the bone ends. The routine hospital stay is one week and the patients are given intravenous antibiotics throughout their admission.

They are reviewed in the outpatient clinic at monthly intervals and the frame is used to compress the bone ends by two to three millimetres on each visit. When there are radiographic signs of union the frame is removed under a general anaesthetic.

Results Nine of the ten patients who have completed their treatment have gone on to union in a mean of 8.25 months with a good functional result. Unfortunately three patients had transient radial nerve palsies.

Conclusions This technique has achieved union and eradication of infection in nine out of ten patients in whom all other forms of treatment had failed.

The validation of a new classification of the external fixator screw-bone interface.

Screw loosening significantly affects the stability of an external fixator, however radiographs are normally taken to assess bone healing and not screw loosening. This study was performed to assess the inter and intra-observer reliability of radiographic features of external fixator screw loosening. Eight observers were shown plain radiographs of 120 external fixator bone-screw interfaces on two occasions, and were asked to grade the screws according to the following features.

Solid screw.

The overall kappa value for this study was 0.29, with the component values ranging from 0.15 to 0.41. To determine if the reliability could be improved, two observers classified 192 digitised radiographs of external fixator screws. On the first occasion the radiographs were shown at a size, brightness and contrast equal to the original film. On the second occasion the radiographs were subjected to image enhancement and magnification. This showed improvement in all the kappa values, the overall value increasing to 0.39, with similar improvements in the component parts. Unfortunately no observations were made of loose screws, therefore, two observers were asked to classify 160 digitised images of screws which were selected with a bias in their outcome, to remain solid or become loose. The observers obtained a kappa value > 0.50 for loose screws.

A classification system for the bone-screw interface is of value both in research and clinical practice. Despite the fact that standard radiographic views were used the classification system described shows satisfactory inter and intra-observer reliability and this improved when digital enhancement was applied.