Background: Although the prevalence of sacroiliac joint (SIJ) pain is relatively high (15 - 30%), there is no unambiguous reference standard to diagnose SIJ pain. Pressure tenderness in the SIJ region is used for diagnostic purposes, but the clinimetric properties of this procedure remain to be determined.
Objectives: The aim of this study is to determine the reliability of pain pressure threshold (PPT) measurements in the SIJ region and the difference in PPTs in the SIJ region between healthy volunteers and PPTs in patients with SIJ pain.
Study design: Prospective cohort study.
Setting: Outpatient pain clinic VU University Medical Center.
Methods: Forty-one healthy volunteers and 31 patients diagnosed with SIJ pain were included. PPTs were obtained from 5 measurement points in the region of the SIJ with a pressure pain algometer using a standardized protocol. The inter-rater reliability of this method was calculated by means of the Intraclass Correlation Coefficients (ICC) of individual assessment performed by 2 individual raters of SIJs of healthy volunteers on both sides. PPTs of healthy volunteers were compared to those of the affected side in patients with SIJ pain.
Results: PPT measurement showed moderate to good inter-rater reliability (ICC 0.6 - 0.82).The median PPTs of 5 points was comparable for both sides in healthy volunteers (right: 8.5 kg/cm2 [IQR 6.0 - 10.0]; left 8.3 kg/cm2 (5.8 - 10.0]). Median PPTs for the affected sides of patients with SIJ pain were significantly lower compared to the same side of healthy volunteers (right: 2.4 kg/cm2 [IQR 2.2 - 3.2, n = 15]; left: 2.5 kg/cm2 [2.3 - 3.2, n = 16]; P < 0.001 for both sides).
Limitations: Only the SIJ on one side of was measured in patients with SIJ pain, where both sides would be desirable.
Conclusions: Pressure pain algometry appears to be a reliable method to establish differences in PPTs between healthy volunteers and patients with SIJ pain. The diagnostic accuracy of this test should be investigated further.