The Audible Pop from Thoracic Spine Thrust Manipulation and Its Relation to Short-Term Outcomes in Patients with Neck Pain

Clinicians routinely consider the success of a thrust manipulation technique based on the presence or absence of an audible pop despite the lack of evidence suggesting that this pop is associated with improved outcomes. The purpose of this study was to determine the relationship between the number of audible pops with thoracic spinal manipulation and improvement in pain and function in patients with mechanical neck pain. In this prospective cohort study, 78 patients referred to physical therapy with mechanical neck pain underwent a standardized examination and thoracic spine manipulation treatment protocol. All patients were treated with a total of 6 thrust manipulation techniques directed to the thoracic spine followed by a basic cervical range of motion exercise. The treating clinician recorded the presence or absence of a pop during each manipulation. Outcomes were assessed at a 2–4 day follow-up with an 11-point numeric pain rating (NPRS), the Neck Disability Index, the patient Global Rating of Change (GROC), and measurements of cervical range of motion (CROM). The relationship between the number of pops and change scores for pain, disability, and CROM was first examined using Pearson correlation coefficients. Individuals were then categorized as having received ≤3 or >3 pops. Repeated measures analyses of variance were used to examine whether achievement of >3 pops resulted in improved outcome. Seventy-eight patients with a mean age of 42 (SD 11.3) years participated in the study. Pearson correlation coefficients revealed no significant correlation existed between the number of pops and outcomes with the exception of 3 of the 6 CROM measurements, which were inversely related. There was no significant interaction for group X time for any of the dependent measures (P>0.05). The odds ratio for patients experiencing dramatic improvement was in favor of the group experiencing ≤3 pops but this was not clinically meaningful (1.3: 95% CI 0.46, 3.7). The results of this analysis provide preliminary evidence for the hypothesis that there is no relationship between the number of audible pops during thoracic spine thrust manipulation and clinically meaningful improvements in pain, disability, or CROM in patients with mechanical neck pain. Additionally, a greater number of audible pops experienced was not associated with a dramatic improvement with manipulation treatment.Key Words: Cavitation, Manipulation, Neck Pain, Audible Pop, Thoracic SpineThe prevalence of neck pain is high, with nearly 70% of individuals experiencing neck pain at some point in their life and with 15–22% of individuals continuing to experience symptoms 5 years after onset^1,2. This results in a substantial economic burden as nearly 1/3 of patients who experience a first-time onset of neck pain will report continued healthcare utilization for their neck pain at a 10-year follow-up³. Additionally, nearly 25% of all visits in outpatient physical therapy practice consists of patients with a primary report of neck pain⁴.Physical therapists utilize a number of interventions in the management of neck pain including joint manipulation (non-thrust and thrust), therapeutic exercise, traction, and a variety of modalities⁵. Recently, evidence has begun to emerge for the use of manual therapy, specifically thrust procedures, directed to the thoracic spine in patients with mechanical neck pain^6–9. Clinicians often believe that an audible pop associated with a thrust manipulation is a criterion for determining the success of the technique¹⁰. However, ultimately the success of an intervention should be based on whether it is associated with improvements in patient-centered outcomes¹¹.Recently Flynn, Fritz, et al¹² reported on a series of 71 patients with non-radicular low back pain (LBP) who received lumbopelvic thrust manipulation. Participants underwent a standardized examination and standardized spinal manipulation treatment program. All patients were treated with a sacroiliac region manipulative technique, and the presence or absence of an audible pop was noted. Similar to the operational definition of an audible pop used in this study, the number of actual pops that may have occurred during one thrust manipulation was not recorded but only whether an audible sound was perceived during one particular manipulation. The subjects were reassessed 48 hours after the manipulation for changes in range of motion (ROM), in pain as measured by the Numeric Pain Rating Scale (NPRS), and in Oswestry (OSW) scores. There were no between-group differences for flexion ROM, NPRS, and OSW scores (P>0.05). The odds ratio (1.2; 95% CI: 0.38–4.04) suggested that the occurrence of a manipulative pop would not improve the odds of achieving a dramatic reduction in symptoms following the manipulation¹². Based on the data, the authors concluded that there was no relationship between an audible pop during sacroiliac region manipulation and improvement in ROM, pain, or disability in individuals with non-radicular low back pain¹².In a follow-up study, Flynn, Childs, et al¹³ examined whether the occurrence of a manipulative pop during lumbopelvic region manipulation was related to the outcome of the intervention over a 4-week period of time rather than the 48-hour follow-up in the earlier study. Seventy patients were randomly assigned to receive thrust manipulation during the first two sessions. Therapists recorded whether the patient or therapist heard either a single or multiple audible pops. Again similar to the operational definition of an audible pop used in this study, the number of actual pops that may have occurred during one thrust manipulation was not recorded. Outcome was assessed with an 11-point NPRS, the OSW, and measurement of lumbopelvic flexion ROM. No differences were detected at baseline or at any follow-up period in the level of pain, the OSW score, or lumbopelvic ROM based on whether a pop was achieved (P>0.05). The odds ratios and 95% confidence intervals for achieving a successful outcome at each of the follow-up periods all approximated a value of 1, suggesting no improvement in the odds of successful outcome among patients in whom an audible pop occurred. The results supported the previous findings that the audible pop was unrelated to changes in patient-centered outcomes for patients with LBP¹³.While previous studies provide evidence that an audible pop accompanying lumbopelvic thrust manipulation is not associated with improved patient-centered outcomes, this has yet to be examined in other spinal regions. Therefore, the purpose of this study was to examine the relationship between the audible pop and patient-centered outcomes in a cohort of patients with neck pain treated with thoracic spine thrust manipulation.