Force measurement during spinal mobilisation

Abstract

Spinal mobilisation or manipulation techniques are frequently used by physiotherapists in the treatment of musculoskeletal disorders. Despite the reliance on these techniques in clinical practice, there is little scientific evidence to substantiate their use. A standard mobilisation couch was instrumented to enable measurement of the forces applied to the trunk during mobilisation of the lumbar spine. Six load cells were incorporated into the couch frame and linked to a personal computer to facilitate data collection. The couch allowed the assessment of the magnitude of the mobilisation force, its direction and the variation in applied load over time. The system was found to be reliable and sensitive over the range of forces applied during mobilisation. The system was used to collect data from a sample of 30 experienced therapists to evaluate repeatability and reproducibility during the application of four grades of a posteroanterior mobilisation and an End Feel, on the third lumbar vertebra. Whilst some therapists demonstrated considerable variation in the forces applied both within one measurement session and over a two week period, others were found to be relatively consistent. The range of forces used by different therapists when performing the same technique was substantial ranging between 63 N and 347 N for a Grade IV mobilisation. A study was carried out involving 26 young healthy subjects, to determine the characteristics of a mobilisation force applied to an asymptomatic spine. A further study was undertaken involving a clinical sample of 16 patients, aged between 47- 64 years, to evaluate the effect of age related degenerative changes of the lumbar spine on the application of these techniques. The magnitude of the mobilisation force was found to be similar for the healthy and the patient groups with median forces of 175 N and 171 N during a Grade IV procedure, respectively. However, the forces applied to the patient group exhibited a statistically significantly smaller amplitude and higher frequency of oscillation than the healthy group for the same procedure (p < 0.01). Such measurements are essential for the assessment of the efficacy of these techniques in clinical practice.