The Interexaminer Reproducibility and Prevalence of Lumbar and Gluteal Myofascial Trigger Points in Patients With Radiating Low Back Pain

OBJECTIVE: To determine the interexaminer reproducibility for judging the presence, number, and location of leg-pain referring myofascial trigger points, and their prevalence in patients with low back pain with and without concomitant leg pain referral. DESIGN: An interexaminer reproducibility study. SETTING: An outpatient public Hospital Spine Centre in Southern Denmark. PARTICIPANTS: Examiners: experienced examiners (N=2), a chiropractor and a physiotherapist, respectively. Subjects: a case mix of patients with low back pain (N=32) with and without leg pain referral. INTERVENTIONS: A standardized palpation examination protocol of 4 bilateral lumbosacral muscles performed by each examiner. MAIN OUTCOME MEASURES: Reproducibility on presence (measured in Cohen’s κ), number (difference and limits of agreement), location (distance between matching marks placed by examiners), and prevalence of myofascial trigger points. RESULTS: Kappa values of the examined muscles were as follows: quadratus lumborum (κ=0.42), gluteus medius (κ=0.83), gluteus minimus (κ=0.74), and piriformis (κ=0.62), with a mean of all examined muscles of kappa=0.66, assessed as substantial agreement. The mean difference in number of trigger points was 0.8, with limits of agreement ranging from −6.4 to 4.9. Mean distance between trigger point locations was 12.9 mm, with 57% only being identified by a single examiner. The prevalence of trigger points was 82.7%, highest in the gluteal region of the painful side. CONCLUSIONS: Inadequate standardization and multiple trigger point sites complicate interexaminer reproducibility on location and number of patients with low back pain and leg pain referral. Nevertheless, substantial interexaminer reproducibility for the trigger point presence appears achievable. Implemented routinely, this relatively simple clinical evaluation procedure could meaningfully enhance diagnostic triage and eventual management.