The use of pMRI to validate the identification of palpated bony landmarks

Accurate palpation of lumbar spinous processes (SPs) is a key component of spinal assessment. It is also vital for the accurate measurement of spinal motion when using external skin marker-based measurement systems, which are being increasingly used to understand low back disorders and their management. The aim was to assess the accuracy of lumbar spinous process (SP) palpation using positional magnetic resonance imagery (MRI) (pMRI). Two experienced manual therapists palpated the L4 SP of nine pain-free participants in standing and prone lying. For each position, an MRI marker was attached over the SP and pMRI scanning was conducted. The position of the marker in relation to L4 on the MRI images was visually inspected, and measurements (mm) of the vertical distance from the superior/inferior aspect of the marker to the superior/inferior aspect of the L4 SP were used to determine palpation accuracy. 71% of Markers were correctly placed over the L4 SP. The magnitude of error for incorrectly placed markers was small, with the largest median distance of 2.7 mm (interquartile range (IQR) 0-3.6) recorded for one of the therapists palpating in prone lying. 100% of markers were correctly placed either on L4 or within one SP in height. pMRI is useful for investigating the accuracy of SP palpation in positions relevant to clinical and research practice.