The automatic pelvic floor muscle response to the active straight leg raise in cases with pelvic girdle pain and matched controls.

Stuge G, Saetre K, Hoff BI: Manual Therapy (2013), http://dx.doi.org/10.1016/j.math.2012.12.004.

Ann Dunbar PT, DPT, MS, WCS

Primary Aim:  (1) To compare the automatic PFM contraction (PFMC) to rest;  (2) To compare voluntary and automatic PFMC during the Active Straight Leg Raise (ASLR) with and without compression; (3) To examine whether there are differences in PFMC between women with and without clinically diagnosed pelvic girdle pain (PGP) during ASLR

 Subjects: 49 pairs of women ages 34.9 ± 4.8 for cases and 35.0 ± 4.8 for controls

Study Design: Cross-sectional study with one-to-one matched cases to control (matched by age ±5 yrs, no. of vaginal deliveries, and age of children ±5 years for those > 1 yr and  ± 1 mo. for those < than 1 yr)

Methods:

• Inclusion criteria:  PGP located lateral or distal to L5-S1 area in buttocks or in symphysis; pain onset during pregnancy or within 3 weeks after delivery
• Controls: without PGP and had to be at least 6 months since delivery, no radiating LBP, and no previous PFM surgery
• Diagnostic criteria: P4 test, ASLR test (0 to 5 scale), pain provocation of long dorsal ligament and of symphysis
• P4 or ASLR with score of at least 3 and at least one of the other tests needed to be positive
• Demographic information gathered via questionnaire
• ASLR performed with uniform instructions; manual compression applied in random group of 22 cases and controls

Ultrasound measurements

• Used previously validated methods (Dietz, 2004) to measure PFM length at rest, with a voluntary contraction, and during the ASLR
• Muscle length reduction can be measured in millimeters using US imaging.  For the PFM the measurement is made assessing the reduction in the levator hiatus area (bordered by pubovisceral m, symphysis and inferior pubic ramus in axial plane)
• Angle of axial plane changes with movement therefore researchers tilted the axial plane when going from assessment at rest to assessment during maximum contraction. Axial plane also tilted around sagittal axis as pelvis might rotate with ASLR.
• To assure accuracy, US images were previewed and excluded unless complete inner border of levator ani muscle was visible

Statistical analysis

• For categorical data: reported as frequencies and percentages
• For continuous data: reported as means with 95% confidence intervals
• Differences between groups analyzed by chi-square tests
• Assumed that 25% reduction in size of hiatus from rest to contraction would be considered clinically important
• For 80% power and a 5% significance level, determined 47 women needed for each group
• Authors also list statistics needed for test-retest intra-tester reliability

Results

• Demographics: see Table 1

• ASLR versus rest: all women automatically contracted levator, narrowing hiatus during ASLR except one woman each cases and controls. Changes in size of hiatus and m. length comparing rest vs. contraction were statistically significant.
• ASLR versus voluntary contraction: significantly larger reduction of m. length during ASLR than voluntary contraction with tendency toward automatic contraction during ASLR being stronger. Authors found positive correlation between automatic PFMC and voluntary.
• ASLR with and without compression: PFM were less contracted when compression applied during ASLR and size of levator hiatus increased.
• ASLR measurements between PGP cases and controls: area of hiatus significantly smaller during ASLR in women with PGP.  Reduction in hiatus area from rest to ASLR not significant between groups.
• Reliability: See table 4. Testing demonstrated very good repeatability.

Discussion

• Levator hiatus smaller in women with PGP:  at rest, during voluntary contraction and during ASLR.
• Automatic PFMC in ASLR tests: Other studies demonstrate variability of response to ASLR but usually a downward movement of the PFM was observed.
• Stronger PFMC during ASLR: surprising aspect of study was that PFM shortened more during ASLR test than during active contraction of PFM.
• Compression reduced PFMC during ASLR: duplicated in other studies. Authors suggest compression might reduce demand for other muscles to better stabilize. Varied responses to compression during ASLR in PGP population may reflect variations in underlying mechanisms contributing to PGP.
• No Differences between cases with PGP and controls: Automatic activation of PFMC same for women with and without PGP whether ASLR test was negative or positive. Results of this study consistant w/ Stuge et al study, 2012, that women with PGP demonstrate smaller levator hiatus suggesting increased PFM activity in this population (not a problem of PFM weakness).  Contraction of PFM contributes to counter-nutation of sacrum. This bracing effort could contribute to stress on SI joint and supporting ligaments leading to pain.
• Measurements: limitation of study was that it did not include measurement of intra-abdominal pressure. Studies have demonstrated decreased diaphragmatic motion with increased intra-abdominal pressure. Authors note they would have expected increased IAP however, no PFM descent was noted. More research is needed.

Methodological Considerations:

Measurement techniques found valid and reliable. Did test-restest analysis. They were blinded to background of subjects and group allocation.  

Clinical Application

1) Do you use the ASLR test for patients to assess load transfer across pelvis?  What helpful clinical information does it give you?

2) Do you consider the role of the PFM when treating women with SI joint dysfunction?

For women with poor PFM strength, do you think using activities shown to activate the PFM via automatic firing would be beneficial? What about the IAP the activities could generate if the PFM are weak?