The cortical strains on the femoral neck and proximal femur were measured before and after implantation of a resurfacing femoral component in 13 femurs from human cadavers. These were loaded into a hip simulator for single-leg stance and stair-climbing. After resurfacing, the mean tensile strain increased by 15% (95% confidence interval (CI) 6 to 24, p = 0.003) on the lateral femoral neck and the mean compressive strain increased by 11% (95% CI 5 to 17, p = 0.002) on the medial femoral neck during stimulation of single-leg stance. On the proximal femur the deformation pattern remained similar to that of the unoperated femurs.

The small increase of strains in the neck area alone would probably not be sufficient to cause fracture of the neck However, with patient-related and surgical factors these strain changes may contribute to the risk of early periprosthetic fracture.

We studied 51 patients with osteo-articular tuberculosis who were divided into two groups. Group I comprised 31 newly-diagnosed patients who were given first-line antituberculous treatment consisting of isoniazid, rifampicin, ethambutol and pyrazinamide. Group II (non-responders) consisted of 20 patients with a history of clinical non-responsiveness to supervised uninterrupted antituberculous treatment for a minimum of three months or a recurrence of a previous lesion which on clinical observation had healed. No patient in either group was HIV-positive. Group II were treated with an immunomodulation regime of intradermal BCG, oral levamisole and intramuscular diphtheria and tetanus vaccines as an adjunct for eight weeks in addition to antituberculous treatment. We gave antituberculous treatment for a total of 12 to 18 months in both groups and they were followed up for a mean of 30.2 months (24 to 49). A series of 20 healthy blood donors served as a control group.

Twenty-nine (93.6%) of the 31 patients in group I and 14 of the 20 (70%) in group II had a clinicoradiological healing response to treatment by five months.

The CD4 cell count in both groups was depressed at the time of enrolment, with a greater degree of depression in the group-II patients (686 cells/mm³ (sd 261) and 545 cells/mm³ (sd 137), respectively; p < 0.05). After treatment for three months both groups showed significant elevation of the CD4 cell count, reaching a level comparable with the control group. However, the mean CD4 cell count of group II (945 cells/mm³ (sd 343)) still remained lower than that of group I (1071 cells/mm³ (sd 290)), but the difference was not significant. Our study has shown encouraging results after immunomodulation and antituberculous treatment in non-responsive patients. The pattern of change in the CD4 cell count in response to treatment may be a reliable clinical indicator.

A retrospective series of 45 cases of chronic osteomyelitis collected over a period of 14 years was histologically classified into tuberculous osteomyelitis (25) and chronic non-granulomatous osteomyelitis (20). The tuberculous osteomyelitis group was divided into three subgroups: a) typical granulomas (13 cases); b) ill-defined granulomas (seven cases), and c) suspected granulomas (five cases). An in-house polymerase chain reaction amplifying the 245 bp nucleotide sequence, and capable of detecting 10 fg of DNA of Mycobacterium tuberculosis, was used on the DNA extracted from the paraffin blocks. The polymerase chain reaction was positive in 72% of cases (18) of tuberculous osteomyelitis, but when typical cases of tuberculous osteomyelitis with confirmed granulomas were considered (13), this increased to 84.6% (11). The chronic non-granulomatous osteomyelitis group gave positive polymerase chain reaction results in 20% of the cases (4).

Our preliminary study on tuberculous osteomyelitis shows that the polymerase chain reaction can be a very useful diagnostic tool, since a good correlation was seen between typical granulomas and polymerase chain reaction with a sensitivity of 84.6% and a specificity of 80%. In addition, our study shows that tuberculous osteomyelitis can be diagnosed in formalin-fixed paraffin-embedded tissues in the absence of typical granulomas.