Quantitative power measurement of extensor hallucis longus. A simple objective test in evaluation of low-back pain with neurological involvement

Abstract

Clinical evaluation of a patient with low-back problem is based mainly upon the subjective impressions of the physician. Accuracy in neurologic evaluation and follow-up of these patients depends upon objective and quantitative procedures. A handy instrument, simple to use by the clinician in his office, was developed in our laboratory and tested on healthy volunteers and patients with low-back problems. The instrument measures or records the power of the extensor hallucis longus. Weakness of this muscle represents the vast majority of root involvement in discogenic lesions. The measurement is compared with the result obtained on the contralateral side. The instrument includes a mobile mechanical spring gauge of 100-2000-gr range and a leg splint. A single channel polygraph can be connected to record the measurement. The technique was tested on healthy volunteers and good reproducibility and accuracy were found. Seventy-five patients were examined and the power of EHL measured. The patients were divided into three groups according to the nature of their back problems: 1) acute discogenic; 2) chronic low back problems with acute exacerbations; and 3) acute trauma. The quantitative measurements of EHL were of great help in evaluating and following treatment of patients with discogenic lesions and in deciding further surgical treatments. The test was valuable in evaluating malingeres and compensation cases. Eight of the patients with chronic, recurrent low-back problems were found to have weakness of EHL; further investigations showed root pressure mostly due to osteophytes pressing on the nerve roots. After acute trauma, the EHL power test also revealed weakness in patients with higher lumbar injuries, probably because of spreading.