Reproducibility and repeatability: errors of three groups of physiotherapists in locating spinal levels by palpation

Location of spinal levels by palpation is an essential part of physiotherapy assessment and treatment of spinal musculoskeletal conditions. This study aimed to (i) investigate the reproducibility and repeatability of three groups of physiotherapists in locating three randomly selected spinal levels by palpation, (ii) explore whether these groups were palpating similar points at each level, and (iii) investigate whether there were differences in palpation across the spinal levels tested. Reproducibility was estimated using a convenience sample of 30 physiotherapists: 13 undergraduate students, 10 clinicians, and seven manual therapists (MTs). Repeatability was investigated using six physiotherapists (two students, two clinicians and two MTs). Each therapist palpated the spinous processes (C5, T6, L5) once for reproducibility, and 10 times for repeatability, on each asymptomatic model. The skin overlying the spinal levels was marked with an invisible pen. Using an ultra-violet light, marks were transcribed onto transparent plastic strips for analysis, and the distances were measured with an electronic caliper. Repeated measures analyses of variance (ANOVA) indicated poor reproducibility across therapists at all spinal levels (F=18.43, P=0.001), but good repeatability within therapists (F=2.09, P=0.161). Students produced different mean locations of their palpatory marks from the other two groups in two spinal levels. Clinicians and MTs were more reproducible than students, and located similar levels. Palpation of L5 spinous process presented the most difficulty, for all groups. Further research is needed to compare different methods of palpation and explore whether reproducibility can be improved.