The Estimation of Plasma Phosphatase as a Test Indicative of the Prognosis of Tuberculous Lesions of Bones and Joints

The assessment of activity of tuberculous lesions of bones and joints is at present a matter of combining general impressions with X-ray findings, and the experience of previous similar lesions, as to the time of immobilisation necessary. The red-cell sedimentation rate, which is generally, and very usefully, employed in pulmonary tuberculosis, does not give an equally useful indication as to the activity, or otherwise, of bone or joint lesions. The writer carried out routine blood sedimentation tests in adults and children suffering from bone or joint tuberculosis, who had been under treatment for varying periods. The results were found in many cases to be at complete variance with the clinical signs and, in the few cases which were followed up, sufficient variation was found to indicate that the test was not sufficiently reliable to form an indication as to the degree of healing present. Temperature records and even fairly free exercise and weight bearing have also proved unreliable, in many cases, and the question of when one may consider that a tuberculous lesion of bone is sufficiently quiescent to allow freedom from immobilisation, or to permit of the operative interference, which is sometimes necessary to obtain a good functional result, is one which is at present extremely difficult to answer with any degree of assurance. A clinical test which would bear a similar relation to bone and joint tuberculosis, as that of red-cell sedimentation to pulmonary tuberculosis, would be invaluable. The attention of the writer was drawn to the work which had been carried out in the estimation of plasma phosphatase, especially in cases of generalized bone disease (osteitis fibrosa and osteitis deformans). These pathological conditions are accompanied by variations in the amount of enzyme phosphatase in the blood plasma, and the suggestion was made that estimations of plasma phosphatase should be carried out in the case of children suffering from tuberculosis of bones and joints, and under treatment at the Manchester Sanatorium, Abergele, North Wales. It would obviously be of value if any connection could be established between any variations in the plasma phosphatase and the clinical and radiological evidence of activity, extent and duration of disease. One might reasonably expect that, in cases where destruction of bone had taken place by absorption, an increase in the plasma phosphatase, parallel to that found in die generalized diseases investigated, would be found and, although the variations might be much less with localized lesions, the 400 to 1000% increase found in generalized disease seemed to promise a margin, within the limits of which, sufficient variation might be found to justify investigation. The following work was therefore undertaken to ascertain whether variations from the normal plasma phosphatase were found in tuberculosis of bone, and whether such variations bore a sufficiently close relation to activity, extent, and duration of disease as to warrant the use of the estimation as a test of quiescence of such lesions