Body perception at the pelvic girdle with the two-point estimation measure: a reliability and validity study

Introduction: Body perception disturbances have been evidenced in low back pain using the two-point estimation (2-PE) measure. The 2-PE has been studied with a method suitable for the assessment unilateral pain, not included a pain-free group, nor examined it at the pelvic girdle (PG).

Methods: 2-PE was tested with a digital calliper (two points 120mm apart), in-person and remotely, using two methods at the PG: a lateral and central measure (two points crossing the mid-line). Reliability and agreement (in-person versus remote) was assessed with Intraclass Correlation Coefficients (ICC) and Bland Altman plots. Validity of the 2-PE at the PG was evaluated comparing data from two populations (pain-free women and women with PPGP).

Results: 22 healthy pain-free participants and 13 participants with chronic (PPGP) were recruited. Intra-rater reliability of the 2-PE (in-person) at the PG was good (central measure - ICC=0.89 95%CI 0.73-0.95) to excellent (lateral measure - ICC=0.91 95%CI 0.78-0.96). Inter-rater reliability was good for all measures (in-person (ICC=0.79-0.80) and remote (ICC=0.90). There was satisfactory agreement between in-person and remote 2-PE measure; lateral (mean difference -3.20), central (PG, mean difference 8.09). Women with PPGP were more accurate in their estimation with both methods but did not reach statistical significance: Estimation error difference=18.22 (95%CI -2.69 - 39.14), p=0.08 (Central - PG); 7.21 (95%CI -34.46 - 48.89), p=0.69 (Lateral).

Conclusion/Discussions: The 2-PE is a reliable measure for assessing perceptual disturbances at the PG. The difference in estimation errors may indicate that women with bilateral pain experience greater perceptual disturbances.