Research Review Corner: December 2012

When assessing and managing patients with low back pain (LBP), many chiropractors successfully utilize mechanically based manual interventions, including movement and spinal loading alteration strategies. 

BACKGROUND INFORMATION
When assessing and managing patients with low back pain (LBP), many chiropractors successfully utilize mechanically based manual interventions, including movement and spinal loading alteration strategies.  

In theory, most LBP patients report movements or activities that aggravate (and arguably, may have originally initiated) their LBP. These can be specific motions, postures or external loads that can result in tissue irritation and pain. Some patients also exhibit patterns suggestive of “instability,” characterized by painful “instability catches” during movement (from flexion to neutral standing, for example). It is thought that this type of symptom is a manifestation of poor motor control – suboptimal muscle activation patterns in and around the lumbar spine during movement. Such changes, based on the current state of the literature, could be both causes and consequences of LBP. 

The flip side of this theory is that as clinicians, we may be able to identify exacerbating positions and tasks via provocative testing, tailoring treatment and rehabilitation interventions accordingly with a goal of reducing pain and further tissue insult. Corrective exercises are commonly used in such cases, often immediately reducing or eliminating pain in these patients.

Despite the widespread use of this approach, the mechanism behind how such interventions relieve pain is still largely unknown. Therefore, the aim of this four-patient case series was to examine whether changes in movement and muscle-activation patterns could alter spine stability and stiffness, joint loading, posture and movement. The authors proposed two hypotheses:

1. Coaching/cueing specific movement patterns would immediately alter reported pain in LBP; and (if this hypothesis is true)
2. these changes would quantitatively change stability, joint loading and posture.

CONCLUSIONS AND PRACTICAL APPLICATIONS
In three of the four subjects studied, there was a clinically significant reduction in pain, supporting the authors’ first hypothesis that altering movement and muscle-activation patterns can have an immediate impact on pain levels. But (this is the important part), there does not seem to be one common “critical” biomechanical variable that was dominant in producing the effect. This finding has two important implications: 1) patients are individuals – meaning what works for one person may not work for another. Customizing the movements and cues provided will help your patients obtain optimal pain relief; and 2) the biomechanical variables chosen here are sensitive to pain modulation, but they differ on the basis of the mechanism of pain. 

Overall, the interplay between spinal stiffness/stability and the forces related to pain elimination seems to be patient-specific. This is a crucial take-away from this case series, and implies that although provocative testing helps to identify possible interventions, the intervention needs to be specific to the individual patient to be most effective. 

STUDY METHODS, STRENGTHS AND WEAKNESSES

This was a quantitative biomechanical case series involving four patients with LBP, who were selected for movement causing ‘catches’ of pain during daily activity. Each subject was assessed utilizing provocative testing to identify motions, postures and loads that exacerbated their pain – these tests have been described in detail in Dr. McGill’s textbook.1

Instrumentation
Full-body kinematics were recorded using 14 body markers, placed bilaterally on: medial and lateral malleoli and femoral condyles, greater trochanter, iliac crest, and acromion.  Force plates measured external forces and EMG recordings were taken from 12 bilateral muscle locations: rectus abdominis, internal oblique, external oblique, latissimus dorsi (LD), upper erector spinae, and lower erector spinae.

Procedure
Each subject performed a variety of pain provocation tests to identify their individual exacerbating activities (see below). Subjects performed these tasks while EMG, kinetic, and kinematic data were simultaneously collected.  During these tasks, they also reported pain levels on a Numeric Pain Rating Scale (from 0-10, a change of > 2 was considered clinically significant).  Then, a clinical kinesiologist utilized verbal and manual cues to alter motion and muscle-activation patterns, aiming to immediately reduce or remove the patient’s pain. These techniques included bracing the abdominal wall and/or latissimus dorsi muscle, and using a hip hinge movement technique (see below).

The pain provoking/relieving tasks included (with corresponding positive subjects):

1. Heel drop test 1 (Subjects 1, 2 and 3)
2. Lifting a 45-lb bar from a 45-cm height (Subject 2)
3. Unloaded squat (Subjects 2, 3 and 4)
4. Sit-to-stand (Subject 4)
5. Stand-to-sit (Subject 4)
6. Jump off a 45-cm stool (Subject 3)

Cues:
Abdominal brace: subjects were asked to stiffen their abdomen by “hardening” their abdominal wall musculature with manual cues. The level of activation was “tuned” to find optimal pain reduction.

Latissimus Dorsi (LD): subjects were instructed to depress the shoulders while stiffening the pectoralis and LD muscles in a co-contracted state.

Hip hinge: involved flexing about the hips rather than flexing or
moving the spine when bending over.

Once the subject understood and executed the new technique, the particular task was repeated, recollecting EMG, kinetic, and kinematic data.

Study Strengths

• Unique approach to the case study/series design;
• Results support the notion that patients are unique, and that sub-grouping of LBP patients should be a critical goal in LBP research and clinical care;
• Integration of anatomical, biomechanical and clinical research into patient assessment and treatment.

Weaknesses

• The decision to use 10 per cent as a cut-off for ‘biological significance’ is arbitrary for kinematic and kinetic variables, but the authors discussed this appropriately, stating that muscle activity changes in patients are often imprecise, and that changes < 10 per cent are likely imperceptible to a patient.

ADDITIONAL REFERENCES

1. McGill SM. Low Back Disorders: Evidence-Based Prevention and Rehabilitation. Champa

In addition to practising full time in Toronto, Dr. Shawn Thistle is founder and president of Research Review Service Inc., an online, subscription-based service designed to help busy practitioners integrate current, relevant scientific evidence into their practice (www.researchreviewservice.com). Shawn also recently launched The Epicurean Scholar, which offers continuing education seminars combined with gourmet food and wine events (www.epicureanscholar.com).  Dr. Thistle graduated from CMCC (where he lectures in the Orthopedics Department) and holds an Honours Degree in Kinesiology from McMaster University. He also holds a certificate in Contemporary Medical Acupuncture from McMaster University, and is a Certified Active Release Techniques (ART®) Provider and Functional Range Release®/Functional Anatomical Palpation® instructor and provider.