2011 Annual Conference

Kelli Brizzolara, PT, OCS

The purposes of this study were to: 1) compare how compression of the sacroiliac joint (SIJ) affects the thickness of the deep abdominal muscles during an active straight leg raise (ASLR) in healthy subjects and in those with pelvic girdle pain, and 2) determine the between-day intratester reliability of ultrasound imaging for assessing percent change of muscle thickness for the deep abdominals.

Fifteen subjects with unilateral symptoms near the SIJ and 15 age-matched and sex-matched control subjects (28 women, 2 men) were recruited for the study via flyers and word-of-mouth marketing.

An ultrasound machine was used to determine muscle thickness of the transverse abdominus (TrA) and internal oblique (IO).  The muscle thickness of each subject was measured at rest and during the ASLR with and without pelvic compression. The percent change of muscle thickness between rest and during an ASLR was used for data analysis.  To complete the reliability portion of the study, the participants returned 2-4 days later to repeat the procedure.

Two separate two-way (group x pelvic compression) ANOVAs with repeated measures were used to analyze the muscle thickness for the TrA and IO.  The between-day intratester reliability was determined using the Intraclass Correlation Coefficient (ICC_3,3) to assess the consistency in measuring the percent change of the deep abdominal muscle thickness.

The results of the ANOVAs were not significant for either the TrA (p = 0.16) or the IO (p =  0.10).  ICC_3,3 was calculated for each group with and without pelvic compression, respectively.  For those with SIJ pain, intratester reliability for measuring percent change without pelvic compression was fair for the IO (ICC_3,3 = 0.70-0.76) and good to excellent for the TrA (ICC_3,3 = 0.63-0.88).  The reliability for the controls without pelvic compression was excellent for the IO (ICC_3,3 = 0.85-0.89) and fair to good for the TrA (ICC_3,3 = 0.52-0.71).  With pelvic compression, the reliability for those with SIJ pain was good for the IO (ICC_3,3 = 0.61-0.74) and good to excellent for the TrA (ICC_3,3 = 0.77-0.94).  The reliability for the controls during pelvic compression was excellent for the IO (ICC_3,3 = 0.82-0.98) and good to excellent for the TrA (ICC_3,3 = 0.71-0.93).

Pelvic compression did not seem to immediately alter the behavior of the deep abdominal muscles during the ASLR in those with SIJ pain or their age- and sex-matched controls.

This study illuminates the immediate effect of pelvic compression on the behavior of the deep abdominal muscles during an ASLR with compression.  Patients with SIJ pain are commonly given pelvic compression belts and instructed to wear these belts for extended periods of time.  Further research is needed to determine any long-term effect of pelvic compression on the behavior of the deep abdominal muscles, as this will guide physical therapists in prescribing effective therapeutic interventions for a subgroup of patients with low back pain.