Comparison of trunk stiffness provided by different design characteristics of lumbosacral orthoses

Abstract

Background: Lumbosacral orthoses (LSOs) are class I medical devices that are used in conservative and postoperative management of low back pain. The effectiveness of LSOs depends on their design aimed at enhancing trunk stiffness. Therefore, the purpose of this study was to compare two lumbar supports: extensible (made of neoprene and lycra) and non-extensible (made of polyester and nylon).

Methods: Trunk stiffness and damping was estimated from trunk displacement data in response to a quick force release in trunk flexion, extension, and lateral bending. Fourteen male and 6 female subjects performed five trials at each experimental condition: (1) No LSO, (2) extensible LSO, (3) non-extensible LSO, (4) non-extensible LSO with a small rigid front panel, and (5) non-extensible LSO with a large rigid front panel. Testing order was randomized and the LSOs were cinched to a pressure of 70 mmHg (9.4 kPa) measured between posterior aspect of the iliac crest and the orthosis.

Findings: The non-extensible LSO reduced trunk displacement by 14% and increased trunk stiffness by 14% (P<0.001). The extensible LSO did not result in any significant change in trunk displacement or stiffness. The addition of rigid front panels to the non-extensible LSO did not improve its effectiveness. The trunk damping did not differ between the LSO conditions.

Interpretation: A non-extensible LSO is more effective in augmenting trunk stiffness and limiting trunk motion following a perturbation than an extensible LSO. The rigid front panels do not provide any additional trunk stiffness most likely due to incongruence created between the body and a brace.

Copyright (c) 2009 Elsevier Ltd. All rights reserved.

Figures

Figure 1

A subject positioned in a multidirectional, quick force release apparatus. (A) Flexion, (B) extension and (C) lateral bending load application and release.

Figure 2

(A) An extensible (Adjustable Back Brace, Mueller Sports Medicine, Inc., Prairie du Sac, WI, USA) and (B) a non-extensible (Quick Draw Pro, Aspen Medical Products Inc., Long Beach, CA, USA) LSOs were compared. Also shown, are the (C) small and (D) large front panels that attach to the non-extensible LSO.

Figure 3

The effects of various LSO designs on the trunk displacement following quick force release. The brackets indicate significant differences in post-hoc pairwise comparisons (p ≤ 0.05).

Figure 4

The effects of various LSO designs on the effective trunk stiffness estimated from kinematic data following quick force release. The brackets indicate significant differences in post-hoc pairwise comparisons (p ≤ 0.05).

Figure 5

Material properties (force-elongation) of the Aspen and Mueller LSOs. By a comparison, they can be referred to as a non-extensible and an extensible orthosis, respectively. A horizontal line at 150N indicates the approximate tension required to achieve a pressure of 70 mmHg (9.4 kPa) between posterior aspect of the iliac crest and the orthosis.