Summit 631

Lumbosacral Orthoses Reduce Trunk Muscle Activity in a Postural Control Task

Cholewicki, J; Reeves, NP; Everding, VQ; Morrisette, DC
Department of Orthopaedics and Rehabilitation, Yale University School of Medicine, P.O. Box 208071, New Haven CT 06520 8071, USA. jacek.cholewicki@yale.edu
Published in J Biomech. 2007;40(8):1731-6. Epub 2006 Oct 18.

Abstract

Biomechanical modeling estimated that trunk muscle activity during various tasks could be reduced by 1-14% without the loss of spine stability when a lumbosacral orthosis (LSO) is worn [Cholewicki, J., 2004. The effects of lumbosacral orthoses on spine stability: what changes in EMG can be expected? Journal of Orthopedic Research 22, 1150-1155]. The present study experimentally tested these theoretical predictions in an unstable sitting task. This task required subjects to balance on a seat supported by a plastic hemisphere (slashed circle=30cm) and placed on a force plate that tracked the center of pressure (CoP). The average CoP velocity quantified subjects' performance. Healthy subjects (12 males, 11 females) balanced for 20s in 3 trials performed with and without the LSO in random order. EMG was recorded bilaterally from rectus abdominis (RA), external oblique (EO), thoracic (TES) and lumbar erector spinae (LES), and expressed as the % of maximum voluntary activation (%MVA). There was no difference in the balance performance with and without the LSO (p=0.13). However, EMG averaged across the trials was significantly lower in the LSO, as compared to the No LSO condition, for TES (5.8+/-3.2 vs. 6.4+/-3.7%MVA, p=0.02) and LES (3.7+/-1.5 vs. 5.9+/-3.9%MVA, p=0.01). No significant differences were present in the abdominal muscle activity. These results agree with earlier spine modeling simulations, which predicted the greatest reduction in muscle activity due to LSO to occur in TES and LES. It was hypothesized that such a reduction in muscle co-contraction could benefit patients with low back pain, who exhibit elevated muscular activity during postural tasks such as walking, standing and sitting.

Selected Quotations

“…Abdominal belts and LSOs increase trunk stiffness and enhance spine stability by making the entire trunk more robust to perturbations.”

(Pg. 1732)

“…in postural control tasks, where the trunk muscle activity does not usually exceed 3% of maximum voluntary activation (%MVA (Cholewicki et al., 1997), the added stiffness from an LSO could contribute significantly to spine stability.”

(Pg. 1732)

“…a small reduction in muscle co-contraction could prevent muscle fatigue in patients with LBP, who exhibit elevated muscular activity during postural tasks such as walking, standing, and sitting (van Dieen et al., 2003). It is known that static contractions sustained above 5%MVA can lead to muscle fatigue and pain.”

(Pg. 1732)

Discussion
“…patients with LBP could benefit from wearing LSOs, which permit a slight reduction in trunk muscle co-contraction while maintaining spine stability. In turn, LSOs may prevent muscle fatigue and pain from compounding the existing pathology.”

(Page 1734)

The Effects of Lumbar Orthoses on the Range of Motion of the Lumbar Spine
During Fifteen Activities of Daily Living

Christopher Miller, MD; Jesse Bible, MD; Debdut Biswas; Peter Whang, MD; Jonathan Grauer, MD
Yale University School of Medicine, New Have, CT, USA
Poster Presented at NASS 24^th Annual meeting. Published in The Spine Journal 9 (2009) 200S.

Abstract

BACKGROUND CONTEXT: Lumbar braces are fequently considered for patients suffering from acute and chronic low back pain, postoperatively, and in other situations. There are a variety of options for lumbar braces ranging from generic, soft corsets to rigid, custom fit orthoses. Previous studies have demonstrated that the range of motion (ROM) reduction from lumbar braces varies greatly from subject to subject based on body habitus and type of brace. They also have shown that the overall reduction in full, active motion is often quite modest. However, there has been little date to date exploring how lumbar braces affect the ROM used during activities of daily living (ADLs).

PURPOSE: The purpose of this study was to evaluate the relative efficacies of a soft corset, a semi-rigid off the shelf LSO, and a rigid, custom molded LSO for restricting both the full, active and functional ranges of motion (ROM) of the lumbar spine during 15 activities of daily living (ADLs).

STUDY DESIGN/SETTING: Prospective cohort study. PATIENT SAMPLE: Ten subjects with no history of lumbar spine pathology and no current back pain or disability.

OUTCOME MEASURES: Full, active functional ROM of the lumbar spine.

METHODS: In this investigation, a previously validated electrogoniometer device was employed to quantify both the full, active ROM of ten subjects as well as the functional ROM during a series of 15 ADLs in the sagittal and coronal planes. For each individual, these ROM measurements were repeated without a brace (No Brace) and after the application of a soft corset (Corset), a semi-rigid off the shelf brace (Semi-Rigid), a custom LSO brace (Custom).

RESULTS: The Corset, Semi-Rigid and Custom braces restricted mean (± 95% CI) full, active motion in the sagittal plane by 24.1 ± 7.9%, 46.8 ± 7.1%, and 64.7 ± 8% compared to No Brace (p < 0.008 for each), respectively. In the lateral plane, they restricted full, active motion by 33.9 ± 8.8%, 51 ± 9.4%, and 49.1 ± 11.8% compared to No Brace (p < 0.008 for each), respectively. There was no difference in ROM between No Brace and any of the braces for seven of the ADLs in the sagittal plane and nine of the ADLs in the lateral plane. In the sagittal plane, there was a greater restriction of full, active motion with the Custom compared to the Semirigid brace (p < 0.01). However, there was no difference between these two braces for the ROM used during any of the ADLs (pO0.325 for all activities). There were 4 ADLs for the Custom brace and 1 ADL for the Semi-rigid brace for which the respective brace provided better sagittal motion than the soft Corset (p < 0.021 for all). In the lateral plane, there were no differences observed in motion restriction between any of the braces (pO0.116 for all).

CONCLUSIONS: We found that all fo the braces provided some restriction of full, active ROM. The custom brace provided the most restriction followed by the Semi-Rigid brace and then the Corset. For functional ROM, we found that the Custom and Semi-Rigid braces provided significantly better restriction during some of the ADLs compared to the Corset. However, there were no differences between these two braces for ROM during any of the ADLs. Thus, depending on the clinical goal of bracing, this study suggests that the Custom LSO may no always be superior to less expensive generic models, which may suffice for providing restriction during many daily activities.

Selected Quotations

Summary: Functional ROM
“…[There was] no difference in functional ROM for Semi-Rigid LSO (Contour^™ by Aspen) and Custom LSO braces for any ADLs in any plane.”

Clinical Significance
“…For Trauma, the Semi-Rigid LSO (Contour^™ by Aspen) and Custom braces provide excellent reductions in full, active and functional ROM.”