Original series results

Th e original polished stems were used between November 1970 and the end of 1975. They were rarely used outside Exeter because, in view of their unorthodox design, the manufacturer agreed to limit their use to the Exeter surgeons and those who had trained with them until the clinical behaviour of the device had been followed over 5 years. The cementing technique utilised in this series was crude, involving purely finger packing of Simplex cement in the dough state. The surgery was performed by 16 different surgeons, 13 of them in the training grades.

The results of these procedures were first reported in 1978 9 and then in 1980 10 at the Combined meeting of the British Orthopaedic Association, the Nordisk Orthopaedisk Förening and the Nederlandse Orthopaedische Vereniging in Amsterdam. Subsequently, the results with up to 17 years of follow-up were published in 198811. Satisfactory pain relief and function were obtained in association with benign X-ray appearances with regard to radiolucent lines and resorption of the cut surface of the femoral neck (the ‘calcar’) that was rare, as was focal femoral lysis. Re-operation for aseptic stem loosening was rarely needed. Stem fracture had occurred in 3 cases at the time of the 5-10 year review, and in addition, there had been 14 neck fractures, all occurring amongst a group of 95 stems that had been excessively machined on the superolateral aspect of the base of the neck (Fig.4).

A finding that was unexpected when the device was introduced turned out to be common – namely, subsidence of the stem within the cement (Figs. 5a & 5b), sometimes associated with ‘punch-out’ fractures of the cement mantle. Initially, these appearances gave rise to some anxiety, and consideration was given to abandoning the use of the device. However, it was decided to persist with its use in view of the good clinical results and uniformly benign appearances of the cement-bone interfaces. It was believed at the time that such subsidence was associated with splitting of the cement mantle, following which subsidence of the double tapered stem forced the cement fragments against the wall of the canal and so retained the stability of the stem. No relationship was found between the extent of the subsidence of the stem within the cement and pain, function or the presence of cement-bone interface radiolucent lines11. If there was a visible change of alignment of the stem with subsidence, it was almost always towards valgus (Figs.5a & b). Subsidence into varus for practical purposes was not seen.

The neck fractures (Fig.4) presented a unique opportunity in that it was not often that any surgeon had the chance to explore the femoral neck and the inside of the cement mantle in patients whose hips had functioned hitherto perfectly well and then failed suddenly in a way that did not involve the breakdown of any of the interfaces. In 9 out of the 14 neck fractures, after removal of the stem, a very careful inspection of the inside of the mantle was performed using a fibrelight, and no cracks or splits in the mantle could be found. In these 9 cases, subsidence of the stem within the cement at the time of the neck fracture varied from 0.5 to 6mms. These findings led to a reappraisal of the behaviour of the cement in accommodating the subsidence. Time-dependent viscoelastic deformation of the cement (creep)12 appeared to be the most likely mechanism.