Research Review By Demetry Assimakopoulos©

Audio:

Download MP3

Date Posted:

June 2011

Study Title:

The Role of Core Stabilization in Lumbosacral Radiculopathy

Authors:

Kennedy DJ & Noh MY

Author's Affiliations:

Department of Orthopedics and Rehabilitation, University of Florida, USA.

Publication Information:

Physical Medicine and Rehabilitation Clinics of North America 2011; 22: 91-114.

Background Information:

Core strengthening exercises are commonly used for injury prevention and rehabilitation of the injured or dysfunctional lumbosacral spine. The core musculature is required for free movement of the spine throughout its range of motion and acts as a ‘kinetic highway’, connecting the upper and lower extremities. The definition of ‘core musculature’ varies in the literature, but for our purposes here the term will encompass more than just the abdominals and posterior back muscles - the pelvic girdle and shoulder muscles should be included as well. These muscles participate in stabilization through connection to the spine and must not be overlooked in any exercise or rehabilitation program geared toward spinal stability.

The model for spinal stability includes 3 components, as described by Panjabi (3): bones and ligaments (passive subsystem), muscles surrounding the spine (active subsystem) and the neural input (neural subsystem) controlling spinal movement. In this model, it is surmised that bones and ligaments provide passive stiffness, whereas the surrounding musculature provides stability throughout the spine’s range of motion. Further, it is described that the neural input creates activation of the core musculature in both planned and unplanned movements.

While some researchers theorize that only a few muscles are important in spinal stabilization (namely, transversus abdominis and lumbar multifidi), it is abundantly important that the entire concert of muscles in the kinetic chain are included in a rehabilitation protocol designed for restoration in function.

Core Musculature Review:

Local core musculature:

The greatest source of stability comes through activation of the core. The deepest, and consequently the smallest muscles, are the lumbar multifidi, interspinales and intertransversarii muscles. Because of their inherently short moment arms, they do not participate in gross spinal movement. However, their organization suggests a role in stabilization and resisting flexion. Also, they house a dense concentration of muscle spindles, suggesting they are designed specifically for segmental proprioceptive function.

Some researchers opine that transversus abdominis (TA) plays a role in stabilizing the lumbosacral spine. In healthy individuals, the TA and the multifidi are the first fibers to activate when a limb is moved, firing independent of limb movement direction (5). This asserts that these muscles stabilize the core in preparation for limb movement. Also, when activated, these muscles have been shown to stabilize the lumbar spine and sacroiliac joints (4).

Furthermore, TA and the lumbar multifidi can become selectively atrophied and dysfunctional in the presence of low back pain (1, 2). These muscular conformational changes may lead to a physiological transformation of the muscles to a more fatigable muscle fiber. There is some evidence showing that exercise training may reverse the atrophy of the multifidus (6, 7). (EDITOR’S NOTE: As noted in prior reviews, the degree to which the TA a) contributes to LBP pathology, or b) should be the focus of specific rehabilitation protocols remains controversial).

Global musculature:

The erector spinae complex, composed of iliocostalis, longissimus and semispinalis are predominantly thoracic muscles which attach to the iliac crests via the erector spinae aponeurosis and lumbodorsal fascia. The lumbar portions of the longissimus and iliocostalis which originate in the lumbar vertebrae attach on the ilium itself. These muscles are thought to create lumbar extension and increase the lumbar lordosis while contracting bilaterally and create lateral flexion when recruited unilaterally. Individuals with low back pain have been shown to have a decrease in lumbar spine extension endurance and abnormal trunk flexor:extensor strength ratios (8).

The quadratus lumborum (QL), a muscle richly invested into the thoracolumbar fascia, extends from the 12th rib and each lumbar vertebral segment to the ilium. It is thought to provide lumbar extension and lateral bending. Weakness and unilateral shortening can cause mechanical dysfunction. QL is a key muscle in lumbar spine stabilization and can be targeted in a rehabilitation program (10).

Lying anterior to the QL is the psoas muscle. Because of its rich attachment to the anterior TVPs and the intervertebral discs of the thoracolumbar spine and insertion into the femur, it is theorized to contribute to increasing the lumbar lordosis and compressive loads.

The rectus abdominus, lying anterior to the lumbar spine, produces lumbar flexion. The circumferential internal and external oblique muscles create axial rotation and are thought to counter axial rotation. By countering these forces, they also contribute to lumbar stabilization.

The diaphragm and pelvic floor muscles have been shown to create compressive loads (11). It has also been shown that patients with sacroiliac joint pain have impaired recruitment of the diaphragm and pelvic floor (12).

The broad, multilayered thoracolumbar fascia is the anchor for multiple core muscles. It also acts to transfer forces from the lower to upper extremity via the kinetic chain. Because of its attachments to the gluteal muscles inferiorly and latissimus dorsi superiorly, it is important to incorporate functional engaging tasks with the upper and lower extremities in any rehabilitation program for the back. Poor endurance of the gluteal muscles have been seen in individuals with back pain.

Clinical Application & Conclusions:

Spinal Flexibility

There has been a lot of varied research on the role of spinal inflexibility in low back pain. While this is true, the authors of this review conclude that despite the conflicting data on this topic, it is reasonable to advise rehabilitative specialists to focus on areas that are deficient in flexibility. It is also important to advise individuals suffering specifically from radicular pain to avoid aggravating positions and that these positions should be addressed by the clinician upon creation of a core stabilization program.

Generally, it is advised to avoid spinal flexion in the case of a disc herniation, and similarly, lumbar extension in the case of neural foramen compromise by posterior elements. These facts should be considered while prescribing stability and flexibility exercises.

Exercises for the Core

The authors propose the following specific phases of rehabilitation for lumbosacral radiculopathy and goals therein:

Phase 1 (Initial phase): Pain Control
  • Anti-inflammatory medication
  • Physical modalities
  • Peripheral or axial injections
  • Activity modification
Phase 2 (restorative phase): Correcting flexibility and strength deficits
  • Mobilization of soft tissue
  • Stretching exercises to improve trunk and extremity flexibility
  • Strengthening exercises to improve cervical, scapulothoracic or lumbar stability
  • Maintenance of cardiovascular fitness
Phase 3 (integrative phase): Functional Adaptations
  • Normalization of spine mechanics
  • Progression towards functional activities
Phase 4 (final phase): Maintenance
  • Pain free
  • Preinjury range of motion and strength
Core strengthening has not been shown to reduce the duration or intensity of acute low back pain (13). However, research has shown that core strengthening may decrease recurrence of low back pain (2). A brief aerobic program consisting of brisk walking should be performed as a warm-up prior to exercising the core muscles. Of course, the standard alternatives of elliptical training and treadmill walking are perfectly acceptable.

In general, it is not advisable to exercise the core musculature after rising, due to the theoretical increase of hydrostatic pressure of the disc in the morning hours (14). It is also wise to be cognizant of the intensity of the exercises prescribed – care should be taken to not maximally fatigue the affected muscles.

The initial stage of any rehabilitation protocol is to facilitate the patient’s awareness of proper motor patterns in their activities of daily living and to reactivate inhibited muscles. The cat/camel, abdominal hollowing and other pelvic exercises are often effective in the early stages. These can be done prone or supine and should aim to recruit the firing of the TA and multifidi.

Keep in mind that these exercises are not performed in functional positions, so transition to functional positions once the proper muscle activation has occurred is ideal. At this point, these exercises should be performed in a non-painful range of motion in order to increase compliance.

At this point, the therapist can choose to change the rehabilitation protocol from training isolated muscles to training the core globally, namely via McGill’s Big 3 (the partial curl-up, side bridge and bird dog) (9).Specifically, the Bird Dog can advance from a 4-point stance, to a 3-point to a 2-point stance. More advanced patients can use a physioball to perform this exercise as well. It is imperative to coach the patient to exercise with a neutral spinal posture, to ensure safety.

It is also greatly important for the therapist to conduct a thorough physical examination prior to training a client/patient. In addition to a pain based physical examination, a functional assessment of triplanar stability should be performed (sagittal, frontal and transverse planes). The multi-directional reach test, the star-excursion balance test and the single leg squat have all been clinically proven to test transverse and rotation movements with great validity (16, 17).

The results of the physical examination allow the clinician to tailor their treatment program to address the existing weaknesses in any of these planes. An example of this is to utilize a triplanar exercise with weights in a lunge position.

Further, the therapist must ensure that neuromuscular control is enhanced through stability exercises, balance training, proprioceptive training (ie. perturbations, wobble boards, roller boards, physioballs, etc.), plyometrics and sport specific skill training.

Reintegration of Functional Activity

Reintroducing the patient into their functional activities is the final step in the rehabilitative process. This involves increasing the patient’s ability to perform their activities of daily living more effectively and efficiently. This step involves home exercise that focuses on the patient’s goals to ensure self-directed continuance of care. At this stage, work-related postures and movements can be replicated to increase work capacity.

Also, an ergonomic assessment and evaluation of proper lifting techniques should be addressed to prevent re-injury. Sport specific activities can also be introduced to increase performance in recreational sports with the guidance of the therapist.

Comment on the Literature:

Efficacy of Exercises

The evidence of efficacy for the previously outlined exercises for the treatment of lumbar radiculopathy is sparse. Very broadly, studies suggest that a comprehensive, structured strength and conditioning program targeted to the core musculature may be efficacious in the management of spinal injuries.

Training should focus on improving the endurance of the deep muscles of the back (multifidi) along with co-contraction of the abdominal muscles. Despite this recommendation, more high quality studies need to be performed to determine the efficacy of exercise therapy targeted to the tissues of the lumbosacral spine for the purposes of strength training, treatment of injury and injury prevention.

Study Strengths / Weaknesses:

Strengths:
  • Outlines completely the steps of proper rehabilitation, from pain reduction to performance.
  • Inclusion of the relevant rudimentary anatomy and biomechanics.
Weaknesses:
  • There was no real inclusion criteria mentioned in the review that pointed the authors toward the cited research papers. It is interesting how they came to the conclusions they did without a specific process.
  • The authors did not describe how a therapist can ensure that their client/patient is in spinal neutral.
  • Further description of different exercises, such as McGill’s Big 3, is needed to teach therapists how to effectively describe these exercises. Many therapists criticize the clinical efficacy of the Big 3, only because they have not received instruction on how to perform the exercises

Additional References:

  1. Hides JA, Richardson CA, Jull GA. Multifidus muscle recovery is not automatic after resolution of acute, first-episode low back pain. Spine 1996; 21 (23): 2763-9.
  2. Hodges PW. Core stability exercise in chronic low back pain. Orthop Clin North Am 2003; 34 (2): 254-54.
  3. Panjabi MM. The stabilizing system of the spine. Part 1. Function, dysfunction, adaptation and enhancement. J Spinal Disord 1992; (5): 383-9 [discussion: 397].
  4. Richardson CA, Snijders CJ, Hides JA, et al. The relation between the transverses abdominus muscles, sacroiliac joint mechanics and low back pain. Spine 2002; 27 (4): 399-405.
  5. Moseley GL, Hodges PW, Gandevia SC. Deep and superficial fibers of the lumbar multifidus muscle are differently active during voluntary arm movements. Spine 2002; 27 (2): E29-36.
  6. Koumantakis GA, Watson PJ, Oldham JA. Trunk muscle stabilization training plus general exercise versus general exercise only: randomized controlled trial of patients with recurrent low back pain. Phys Ther 2005; 85 (3): 209-25.
  7. Koumantakis GA, Watson PJ, Oldham JA. Supplementation of general endurance exercise with stabilization training versus general exercise only: Physiological and functional outcomes of a randomized controlled trial of patients with recurrent low back pain. Clin Biomech (Bristol, Avon) 2005; 20 (5): 474-82.
  8. Jorgensen K, Nocolaisen T. Trunk extensor endurance: determination and relationto low back trouble. Ergonomics 1987; 30 (2): 259-67.
  9. McGill SM. Low back stability: from formal description to issues of performance and rehabilitation. Exerc Sport Sci Rev 2001; 29 (1): 26-31.
  10. McGill SM. Low back exercises: evidence for improving exercise regimens. Phys Ther 1998; 78 (7): 754-65
  11. McGill, Sharratt MT, Seguin JP. Loads on spinal tissues during simultaneous lifting and ventilator challenge. Ergonomics 1995; 38 (9): 1772-92.
  12. O’Sullivan PB, Beales Dj, Beetham JA, et al. Altered motor control strategies in subjects with sacroiliac joint pain during the active straight leg test. Spine 2002; 27 (1): E1-8.
  13. Hayden JA, van Tulder MW, Malmivaara A, et al. Exercise therapy for treatment of non-specific low back pain. Cochraine Database Syst Rev 2005; 3: CD000335.
  14. Adams MA, Dolan P, Hutton WC. Diural variation in the stresses on the lumbar spine. Spine 1087; 12 (2): 130-7
  15. Kizney Sj, Armstrong CW. The reliability of the star-excursion test in assessing dynamic balance. J Orthop Sports Phys Ther 1998; 4(1): 19-21.
  16. Olmsted LC, Carcia Cr, Hertel J, et al. Efficacy of the star excursion balance tests in determining reach deficits in subjects with chronic ankle instability. J Athl Train 2002; 37 (4): 501-6.