Background: Quantitative sensory testing (QST) conventionally identifies threshold elevation as reflecting sensory deficit. A major disadvantage of the technique is its inability to distinguish organic from feigned sensory deficit, as both are characterized by an elevated threshold.

Aim: To distinguish organic from feigned sensory deficit.

Method: Vibratory thresholds and their variances were measured, at foot L4, L5 and S1 sites, in 14 patients with low back pain (LBP) suspected of non-organic sensory loss by clinical criteria of Waddell, 14 patient controls with abnormal neurological examination and CT of the low back, and 20 healthy controls.

Results: Thresholds of non-organic patients and of patient controls were elevated to a similar extent compared to those of healthy controls. Variances, however, were higher for non-organic patients (6.7–10.5 for the various test sites) than for either patient controls (0.39–0.80, p: 0.001–0.05) or for healthy controls (0.20–0.54, p: 0.001–0.02). Of non-organic patients with high thresholds who would otherwise be identified as pathological, 30–67% were ‘spared’ the misdiagnosis and correctly identified as non-organic because of the inclusion of the variance criterion.

Conclusion: Variance evaluation is therefore suggested for inclusion into QST methodology, together with threshold itself, as a quality assurance parameter.

Aim: To evaluate the clinical and radiological results of hydroxyapatite stem in primary total hip replacement.

Method: A prospective review was performed on 22 osteoporotic patients (Singh index 1–3) with hydroxyapatite-coated total hip replacements. These results were compared with a control group (Singh index 4–6) of 45 patients (48 hips) with respect to clinical and radiographic data. Surgery was performed over a six year period (1991–1996) and the time to follow-up evaluation averaged 5 years (range 2–7 years). Clinical evaluation was based on the Harris Hip score and radiographic evaluations using Engh’s criteria.

Results: There was no significant difference between the final average Harris hip score in the osteoporotic bone group which was 87 points and that for the control group which was 91 points (p> 0.05). Radiographic evaluation demonstrated confirmed bone ingrowths in all patients except for one patient in each group, each with suspected bone ingrowth. There were no stems revised for aseptic loosening and no endosteal lysis was found. Progressive bone formation was seen around the femoral stem proximally. The acetabular components demonstrated no sign of mechanical loosening or osteolysis. Bone formation was found in most patients in zone I, and less in zone III.

Conclusion: The basis of the results of this study, it is believed that osteoporotic bone as a factor by itself should not compromise the early results of hydroxyapatite total hip arthroplasty and hopefully give as good results n the long term.