OBJECTIVE: The purpose of this study was to determine from which side of the spine the popping sound (PS) emanates during side-lying, rotatory high-velocity low-amplitude (HVLA) thrust manipulation directed to the L5-S1 articulation using a time-frequency analysis. Secondary aims were to calculate the average number of PSs, the duration of lumbar thrust manipulation, and the duration of a single PS.
METHODS: Thirty-four asymptomatic participants received 2 lumbar HVLA thrust manipulations targeting the right and left L5-S1 articulations. Two high sampling rate accelerometers were secured bilaterally 25 mm lateral to the midline of the L5-S1 interspace. For each manipulation, 2 audio signals were extracted and singularly processed via spectrogram calculation to obtain the release of energy over time on each side of the lumbosacral junction.
RESULTS: During 60 HVLA thrust manipulations, it was measured a total of 320 PSs. Of those PSs, 176 occurred ipsilateral and 144 occurred contralateral to the targeted L5-S1 articulation; that is, the PS was no more likely to occur on the upside than the downside facet after right or left rotatory L5-S1 HVLA thrust manipulation. Moreover, PSs occurring on both sides at the same time were detected very rarely (ie, 2% of cases) with the lumbar HVLA thrust manipulations. The mean number of audible PSs per lumbosacral HVLA thrust manipulation was 5.27 (range 2-9). The mean duration of a single manipulation was 139.13 milliseconds (95% confidence interval: 5.61-493.79), and the mean duration of a single PS was 2.69 milliseconds (95% confidence interval: 0.95-4.59).
CONCLUSION: Based on our findings, spinal manipulative therapy practitioners should expect multiple PSs that most often occur on the upside or the downside facet articulations when performing HVLA thrust manipulation to the lumbosacral junction (ie, L5-S1). However, whether the multiple PSs found in this study emanated from the same joint or adjacent ipsilateral or contralateral facet joints remains unknown. A single model may not necessarily be able to explain all of the audible sounds during HVLA thrust manipulation.
Author keywords: Manipulation, Spinal, Lumbosacral Region
Author affiliations: FM, JD: Escuela Internacional de Doctorado, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain; FM, JD, CFP: Department of Physical Therapy, Occupational Therapy, Rehabilitation and Physical Medicine, Universidad Rey Juan Carlos, Alcorcón, Madrid, Spain; FM, JD, RB: American Academy of Manipulative Therapy Fellowship in Orthopaedic Manual Physical Therapy, Montgomery, Alabama; FM: Poliambulatorio Physio Power, Brescia, Italy; AZ: Information Engineering Department, Università di Pisa, Pisa, Italy; RI: Koinè Physiotherapy, Florence, Italy; RB: Research Physical Therapy Specialists, Columbia, South Carolina.; NZ: Osteopractic Physical Therapy of the Carolinas, Fort Mill, South Carolina;
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