We identified patients with a poor outcome by examining cases where nerve conduction studies had been repeated after surgery. 168 patients were identified in whom two sets of tests had been performed. 28 were excluded as either they had no pre-operative studies or had insufficient clinical information. Our study group was 140 patients (174 hands) in whom NCS had been performed before and after surgery, with adequate clinical information. Information on the clinical outcome was obtained from postal questionnaires and from hospital records. A proportion of the hands in which two tests had been performed turned out to have been retested because of presentation with symptoms in the other hand, after a satisfactory outcome from surgery on the first side. This accounted for 44 of the 174 hands, and these were used as control group. 130 hands in 92 patients were identified as having a poor outcome from surgery. Of these, 39 underwent a further operation; two went on to a third procedure. Logistic Regression Analysis was used to analyze the data (Stastica).

There was a trend for the poor results to be more common in the elderly, but age was not a statistically significant factor, (p< 0.36). The good results were found mainly in grades 2 to 5 and this was statistically significant, (p< 0.01). A poorer outcome was seen grouped in grades 0, 1, 2 and 6 and this was statistically significant. (p< 0.01). The NCS have been validated, are reproducible and cost about £15 per study. In the group with good outcome, the grade of severity of NCS improved or remained unchanged in the majority. Of the 39 re-explorations, 17 were found to have incomplete division of the ligament. Of these, 10 showed clinical improvement after re-operation. Of the 22 with no evidence of incomplete division, 7 were improved, 10 had persistent symptoms and 5 were worse after revision surgery.

We believe that pre-operative NCS are helpful for two reasons: Firstly, they provide as a baseline for comparison if the patient has unsatisfactory result following decompression. Secondly, we have shown that they are of prognostic value.

In a 10-year prospective study, 561 displaced subcapital fractures of the femoral neck in 546 patients were treated with the Hastings bipolar hemiarthroplasty. Within six months of their operations, 148 patients had died. In 322 hips followed up, 243 with adequate serial radiographs separated by more than one year, only 14 (5.6%) showed acetabular erosion. A group of 91 had been reviewed for between three and nine years (mean, 4 years 10 months) and of these, 95% had no pain or slight pain only. Comparison with an earlier series of conventional hemiarthroplasties reported from this institution showed that the clinical results were similar, but that the erosion rate had been halved.

Using dried bones which could be tilted and rotated, we assessed the accuracy of published radiographic methods for measuring the migration of prosthetic acetabular components and compared the results with a new method. The new line linking acetabular margins was significantly more accurate for proximal migration than the teardrop, the sacroiliac line or the sacroiliac-symphysis line. For medial migration, a new line tangential to the brim and through the horizontal mid-point of the obturator foramen was more accurate than Kohler's line, the ilio-ischial line or the iliopubic line. In combination, the two new lines can give a more accurate assessment of acetabular erosion than previous methods, since they are less affected by the differences in rotation commonly found in a series of radiographs.