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Technical Forum: Improved Orthotic Low-Back Support for Help with Low-Back Pain

Richard M. Deamer, MD
Robert B. Anderson, MSc

ABSTRACT

This article discusses the postoperative rehabilitation success of a 42-year-old white male patient who underwent discectomy and fusion of the L5-S1 vertebrae in 1989. The operative procedures were a technical success, but the patient continued to suffer from chronic low-back pain symptoms and remained unemployed and on disability. He was particularly sensitive to forward flexed postures and exhibited low tolerance for exercise.

The patient was fitted with a Bending Non-Demand Return (BNDR®) lumbosacral orthosis (LSO) designed specifically for dynamic assistance while in the forward flexed posture. Results were dramatic; back range of motion and mobility were substantially improved with increased tolerance for exercise, resulting in a weight loss of 34 lbs and improved quality of life. The authors believe this to be the first application of a dynamic orthosis to aid in low-back rehabilitation.

Introduction

Residents of the United States spend $20 billion to $24 billion annually for diagnostic procedures and treatment of low-back pain (LBP) (1). Indemnity and lost productivity push the total cost to more than $80 billion annually; it is little wonder that back pain and disability command priority with compensation (2,3). An estimated 93 million workdays may be lost each year as a direct result of LBP (4).

While the majority of individuals affected with LBP will suffer temporarily and recover with conservative management, the remainder will suffer more serious conditions due to herniated discs, displaced vertebrae and other problems that can cause lower-extremity weakness, radiating pain and limited range of motion.

The biomechanics of lumbar-spine loading are well-documented. One dynamic model uses a free-body diagram that quantifies the influence of forward bending (stooping) on developed L5-S1 compressive forces (5#). Correlation also has been found between forward-bending, lumbar-surface electromyographic (EMG) activity and spinal intradiscal pressure (6) while others have related applied lumbar moments to a simple biomechanical model and verified these with EMG (7).

A complex numerical finite element (FE) model also has been developed to yield an optimized solution that predicts intravertebral disc and muscle forces (8). Researchers validated this model with EMG data and correlated the FE calculations with others. Simpler two-dimensional models are available for industrial ergonomic studies (9,10).

These works are by no means all-inclusive; much research has been devoted to understanding the forces within the lumbar musculoskeleton and associated etiologies of LBP (11,12). The data indicate factors such as continued bending, twisting and vibration result in high disc loads, microtears, ligamental strain and muscle fatigue. This sort of biomechanical wear and tear also is thought to contribute substantially to the onset of LBP (13-15).

The following discussion describes a 42-year-old man with L5-Sl spondylolisthesis and disc herniation who failed to respond to conservative pain management; he eventually underwent surgical excision of the disc and a lumbosacral fusion. Although the operative procedure was a technical success, the patient continued to suffer from LBP and found activities of daily living limited, especially those involving forward flexion.

The patient was fitted with a Bending Non-Demand Return (BNDR®) kinetic lumbosacral orthosis (LSO)/exo-skeletal support to assist flexion, thereby enhancing daily mobility. He benefited considerably with improved range of motion in forward flexion and exercise tolerance resulting in dramatic loss of excess weight as well as improved quality of life.

The Subject

When he was 36 years old, the subject in this study (an electronics technician) underwent discectomy and L5-Sl lumbosacral fusion subsequent to a fall in a shower that resulted in spondylolisthesis of L5 over S1 and a herniated disc. Chronic LBP, most likely discogenic, predated the fall. The patient had experienced recurrent pain associated with physical activity and postural changes as well as occasional sharp pain radiating into the left leg and ankle.

The patient was referred to back school, where he learned some helpful relaxation and exercise techniques. However, forward flexion continued to cause a marked exacerbation of pain. He essentially was areflexic in the lower extremities but without significant motor or sensory deficit. Epidural blocks were helpful in the short term but did not provide lasting relief.

After the operation, the patient continued to have significant LBP with a moderate amount of spasm in the paraspinal musculature. Lumbar X-rays revealed no subluxation or dislocation at L5-Sl. One month after fusion, he developed radiating pain in the left leg distal to the heel. Six months later, he was using excessive amounts of pain medication even though the wound had healed well, and he had a reasonably good range of motion. His primary concern, however, was low endurance.

Five years after the injury, the patient remained on total disability. He had "given up" on pain medications since side effects made him question the benefits. Unemployment and loss of productivity around his home led to a referral for fitting with the BNDR LSO. The orthotic assessment and prescription were based on the following questions:

  • How debilitating was the chronic pain syndrome, and to what extent was range of motion restricting his activities of daily living?
  • To what extent was exercise intolerance contributing to weight gain and other problems associated with reduced physical activity?
  • To what extent would a novel approach to these problems, using a mechanical brace designed to support the upper body when leaning forward, alleviate his difficulties?
  • And, finally, what would constitute the ultimate end of rehabilitation with this approach?

Method

The authors' initial approach was to fit this now 42-year-old man with a new orthosis designed for protection against the onset of LBP. The BNDR is a spring-loaded dynamic support system that stores energy during flexion and returns it to the musculoskeletal system. This property reduces lumbar loading (spinal compression) and erector spinae usage while performing tasks in the stoop posture.

The BNDR orthosis, depicted in Figure 1 , uses aluminum frame members for distributing loads to the anterior thoracic and quadricep contact points. Nylon-covered foam pads cushion the interface. A pelvic belt attaches to the frame via a unique spring/elastomer (urethane rubber) spool system. The spring itself is a combination torsion/leaf design, arcuate in shape, but left partially open anteriorally for easy mount and dismount of the frame. The frame is mounted by simply "clipping" the arcuate springs over the pliable spools. The belt, which fits at the pelvic girdle level, is nylon/foam construction with a reinforcing insert. The spools typically are adjusted slightly posterior to the iliac crest. Users typically describe BNDR-assisted flexion as "floating" over the task/activity site.

The authors had not tried the BNDR orthosis on individuals with a history of serious back injury requiring surgical intervention and considered the orthosis experimental in this regard. The stability of the patient's back was assessed, and he was informed of the experimental purpose, procedure, possible benefits and risks of participating in the trial before he gave his informed consent. The patient had, on occasion, been wearing a lumbosacral (abdominal compression) belt without much benefit. Others have had success using the BNDR orthosis for acute LBP management and for LBP primary prevention in industrial and agricultural work environments.

Results

There was no doubt this individual was considerably compromised in his activities of daily living. He noted that any bending or lifting exacerbated his LBP to the point of being unable to function. The authors verified this with home visits that allowed a pre- and post-treatment assessment of back function in daily activities.

Within one month of initial fitting with the BNDR, the patient was able to garner self-confidence in his ability to mobilize and flex at the waist. Bending/stooping movements in the past had been impossible due to pain and a psychological fear that he might reinjure himself. While wearing the orthosis, he was able to more frequently perform many activities, such as gardening, and also resumed other activities that encourage back exercise and weight loss.

It is axiomatic that reduced physical activity will lead to a slowing of metabolism with associated weight gain. This man was no exception, and one of the benefits to his use of the orthosis was a reported weight loss of 34 lbs as his physical activity increased. With less weight to carry around, self-image and self-worth increased. Truncal flexion was reported to have become much easier. Back-flexion range-of-motion measurements now possible with the orthosis are 60 to 90 degrees, pain-free.

Discussion

BNDR, a new orthosis for mitigating LBP, is a dynamic LSO that works by supporting the upper truncal body weight while the wearer is in a forward-flexed (or stooped) position. BNDR reduces lumbar loading by displacing the low-back biomechanical loads to the upper torso, pelvis, and left and right quadriceps. As the user flexes, the torsion spring mechanism applies force through the frame, which pushes upward on the torso and downward on the quadriceps. In this fashion, lumbar loads are reduced. A simplified free-body diagram depicting functional operation together with involved forces is shown in Figure 2 , and Figure 3 depicts a person wearing the BNDR orthosis.

Our subject had been suffering from LBP prior to the very serious injury that led to discectomy and spinal fusion. The authors speculate the previous LBP might have contributed to his back injury. Five years after surgery, he was still disabled but obtained considerable improvement in his condition after orthotic intervention. This is consistent with Twomey and Taylor's observation that exercise mobilization should have greater effect on subacute and chronic LBP than acute pain (16). These authors further suggest large spinal movements in the sagittal plane promote enhanced nutrition transfer to the intervertebral discs. Although this would indicate a necessary adjunct to spinal healing, sustained disc loading at full flexion also could lead to disc herniation and LBP (16).

This approach also makes sense for postoperative rehabilitation where the same spinal unloading feature may promote healing and improve back mobility. Such mobility, in turn, may provide an option for patient "return-to-back" therapeutic exercise.

The BNDR orthosis also may be considered a dynamic system, unlike traditional back orthoses, which operate through immobilization principles. This means that in the BNDR, forces are applied throughout a range of motion, not just statically. This principle continues to be explored via surface EMG studies. A comprehensive laboratory protocol is the subject of a Phase I Small Business Innovative Research grant currently underway.

Conclusion

The results of this case offer good reasons for further exploration of BNDR orthosis efficacy in rehabilitative roles. We can hypothesize the orthotic function promotes a more ideal therapeutic measure by allowing back exercise while at the same time alleviating potentially dangerous mechanical loads. This orthosis approach also appears uniquely qualified to provide support dynamically.

It should be noted the patient had tried many of the corset and belt supports over the previous five years without significant impact on the course of his disability. The BNDR orthosis, on the other hand, offered relatively pain-free mobility and improved range of motion with associated exercise tolerance and weight loss.

There are considerable economic factors as well; over the seven years of disability from the original injury and only partial recovery with the operative procedures, the patient estimated a cumulative case cost of roughly $500,000, including loss of income. Such costs are not atypical for chronic back disability cases; we can only speculate what costs might have been spared through earlier intervention.

The patient did not receive physical or occupational therapy and did not persist with back school. He was dealing with severe depression, related in part to his back injury, and could not develop the motivation for these treatments. He enthusiastically embraced the BNDR, however; and the authors' concerns that his use of the orthosis might exacerbate his injury and add to his painful condition proved unfounded.

The authors postulate the orthosis allowed a gentle support of paralumbar musculature while trunk flexion/extension freed-up postoperative adhesions. Whatever the reason for his improvement, the BNDR orthosis seems to have played a significant role in this patient's rehabilitation.


References:

  1. Purvis A. Is there a method to manipulation? Time Sept. 23, 1991;60-1.
  2. Frymoyer JW, Cats-Baril WJ. Overview of the incidence and costs of low-back pain. Orthop Clin of North America April 1991;22:263-72.
  3. Webster BS, Snook SH. The cost of 1989 workers' compensation low-back claims. Spine 1994;16:10:1111-5.
  4. Saunders D. For your back, self-help manual. Eden Prairie, Minn.: Viking Press, 1990;2-3.
  5. Jager M, Luttmann A. Biomechanical analysis and assessment of lumbar stress during load lifting using a dynamic 19-segment human model. Ergonomics 1989;32:1:93-112.
  6. Ortengren R, Andersson GBJ, Nachemson AL. Studies of relationships between lumbar disc pressure, myoelectric back muscle activity and intra-abdominal pressure. Spine 1981;6:1:98-103.
  7. Seroussi RE, Pope MH. The relationship between trunk muscle electromyography and lifting moments in the sagittal and frontal planes. J Biomech 1987;20:2:135-46.
  8. Goel VK, et al. A combined finite element and optimization investigation of lumbar spine mechanics with and without muscles. Spine 1993;18:11:1531-41.
  9. Chaffin DB. A computerized biomechanical model-development of and use in studying gross body actions. J Biomech 1969;2:429-41.
  10. Andersson GBJ, Chaffin DB. Occupational biomechanics. New York: John Wiley and Sons Inc., 1984.
  11. Ladin Z, et al. The effects of external bending moments on lumbar muscle force distribution. J Biomech Eng August 1991;113:284-94.
  12. Pope MH, Frymoyer JW, Andersson GBJ. Occupational low-back pain. New York: Praeger Publishers, 1984.
  13. Andersson GBJ. Epidemiologic aspects of low-back pain in industry. Spine 1981;6:1:53-60.
  14. Ayoub MA. Ergonomic deficiencies: I. pain at work. J Occup Med 1990; 32:1:52-7.
  15. Walsh NE, Schwartz RK. The influence of prophylactic orthosis on abdominal strength and low-back injury in the workplace. Am J Phys Med 1990;69:5:245-50.
  16. Twomey L, Taylor J. Spine update: exercise and spinal manipulation in the treatment of low-back pain. Spine 1995;20: 5:615-9.