Low Back Pain and Obesity

According Bener et al (2003), obesity was proven to be a risk factor for LBP. The prevalence of obesity is higher in females with LBP than in males with LBP according to their study. To conclude whether there is a causal association between obesity and back pain, it is necessary to consider the weight evidence, both for and against. Overall, there is some evidence in favor of a causal explanation. In general, obesity might be positively associated with LBP either because excessive body weight could have mechanical ill effects on the back caused by excessive weight-bearing or that there could be a biochemical explanation for such a link. In addition, obesity in itself might have some influence on LBP due to poor lifestyle habit and loss of muscle mass. Bener and company came to a conclusion that obesity is moderately positively associated with LBP.

According to Shiri et al (2008), obesity is associated with LBP in women but not in men. In their study, a number or weight-related factors were considered and waist circumference was the strongest determinant of LBP in women. Important to note, waist circumference and BMI measure different aspects of obesity. Waist circumference is a strong predictor of both visceral and subcutaneous adipose tissues (abdominal obesity). They concluded that abdominal obesity was the primary weight-related risk factor for LBP and that obesity may exert its effects on LBP via mechanical stress, metabolic/inflammatory pathways, or interplay of both.

Mirtz et al (2005) performed a literature review using Medline to determine whether obesity is associated with low back pain. They concluded that the available data is still controversial with no clear-cut evidence connecting low back pain with obesity. Although it is true that people with increased BMIs demand more from their musculoskeletal systems, there is still no fine evidence to draw a cause and effect relationship. Furthermore, obesity is more common in women, whereas overweight is more common in men (may help explain the Shiri results). What they feel to be the main concern in linking obesity as a causal factor for LBP is the numerous variables encountered in these people. These include negative self images, sedentary lifestyles, muscular weakness, etc. Being overweight, however, also has a tendency to cause a greater likelihood of developing spondylosis, osteoarthritis, and disc herniation (according to some studies). They end by saying that individuals with a BMI under 30 are at minimal risk of developing LBP while those whose BMI increases to over 30 are at moderates risk of developing LBP (>40 = high risk). Lastly, an important question to think about is does someone become overweight/obese due to back pain, or does obesity cause back pain?

Webb et al (2003) also concluded that obesity (>30 BMI) is a strong predictor of back pain with disability.

Manchikanti (2000), like many of the above articles already presented, agrees that there are several hypotheses relating to a linkage between obesity and LBP: Increased mechanical demands resulting from obesity have been suspected of causing LBP through excessive wear and tear, and it has also been suggested that metabolic factors associated with obesity may be detrimental. Obesity, defined as being 30% over ideal weight, influences normal body mechanics by making it more difficult to sit, stand, and walk and increases the time required to recover from an injury. Fatty tissue is a stress on the body even when a person is not injured, as it decreases blood flow carrying nutrients for healing to the injured area. Since it is well known that too much fat is associated with loss of endurance, it is presumed that obesity also makes rehabilitation more difficult for the low back injury patient since poor endurance and cardiovascular fitness may hinder full participation in therapy.

Some consider obesity a strong contributor to back pain while others consider it only a possible or minor contributor (if any at all). In a systematic review highlighted in this article by Leboeuf-Yde, 32% of all studies reported a statistically significant positive weak association between body weight and low back pain. Due to a lack of overall evidence, however, body weight should be considered as a possible weak risk indicator of back pain.

Several studies do show that lumbar disc herniation symptoms were more common in people who were overweight or who had a larger waist circumference. Lastly, other studies showed that increased BMI scores were associated with more frequent osteophytes at the lumbar spine (recurring themes).

In conclusion, it is quite clear that any positive cause and effect relationship between obesity and LBP is still somewhat controversial. There is some evidence to suggest that obesity does indeed cause LBP, but no scientific evidence exists to hang your hat on.

References
Bener, A., Alwash, R., Gaber, T. (2003) Obesity and Low Back Pain. Collegium Antropologicum. 1: 95-104

Manchikanti, L. (2000) Epidemiology of Low Back Pain. Pain Physician. 3(2): 167-192
Mirtz, T.A., Greene, L. (2005) Is obesity a risk factor for low back pain? An example of using the evidence to answer a clinical question. Chiropractic and Osteopathy. 23(2)

Shiri, R., Solovieva, S., Husgafvel-Pursianen, K. (2008). The association between obesity and the prevalence of low back pain in young adults. American Journal of Epidemiology. 167(9): 1110-119

Webb, R., Brammah, T., Lunt, M. (2003) Prevalence and predictors of intense, chronic, and disabling neck and back pain in the UK General Population. SPINE. 28(11) 1195-1202

 

Pathomechanics of Sub-Acromial Impingement

A basic definition of sub-acromial impingement is when the sub-acromial space becomes narrowed in some fashion causing the pain sensitive structures within that space to become compressed and painful. The first step, is to determine how does the narrowing of the sub-acromial space occur, because by reversing this process, there will be improved shoulder girdle mechanics and function with decreased pain.

Defining the Sub-Acromial Space

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Superior Border – Acromioclavicular joint and the Coracoacromial arch consisting of the coracoid, acromion and coracoacromial ligament. The posterior portion of the coracoacromial arch is where impingement usually occurs.

Inferior Border – Head of the Humerus

Contents – Sub-acromial bursa, supraspinatus tendon, infraspinatus tendon, teres minor tendon, long head of biceps

 

Normal Sub-Acromial Biomechanics

In order to achieve forward elevation above 90 degrees, the rotator cuff must pass under the coracoacromial arc. There will always be contact between the arch and rotator cuff because the sub-acromial space is a relative space. Some studies have even shown rotator cuff contact with the arch at 0 degrees. The contact is at the anterolateral component of the coracoacromial arch. As the arm elevates the contact moves medially. The humerus contacts the undersurface of the supraspinatus in a proximal to distal fashion with forward elevation. During arm movements the primary bursal contact is with the supraspinatus insertion. Sub-acromial bursa lies superior to the rotator cuff muscles and extends from the proximal 1/3 of the humerus (underneath deltoid) to medially beyond the AC joint. Bursa is heavily innervated. The rotator cuff muscles function as a unit to compress the humeral head into the glenoid fossa during movements. This limits the translation of the humeral head on the glenoid and allows for proper rotational movement. Thus the rotator cuff is very important for stability of the GH joint.

Pathomechanics

Problems usually arise during 70-120 degrees of arm elevation. As mentioned before, the subacromial space is not big and the contents within the space can easily become compressed against the coracoacromial arch. Therefore, any excess superior translation of the humeral head means more compression will occur. Extra wear and tear can exist as well with overhead athletes that put their arm through high loads and velocities in an abducted position. When your arm is abducted and taking from ER to IR with high loads and velocities, this can cause wear and tear on the sub-acromial structures. Repetitive unprotected overhead motion leads to insult of tissues in the subacromial space, which causes inflammation and tissue damage which starts the vicious cycle.

Causes of Sub-Acromial Impingment

There are inherent variations with respect to the acromion. Shape of acromion is important. There are three different shape types.2

Type 1 – Flat – 18%

Type 2 – Curved – 41%

Type 3 – Hooked – 41%

It was found that flat acromions were only associated with 3% of full thickness tears whereas hooked acromions were associated with 70% of full thickness tears.

These are different from natural acromion variations. These are adaptive in nature. Anterior acromial spurs are not that common at 14% of cadaveric specimens, but they were associated with 70% of rotator cuff tears. There are several theories as to why there is anterior spur formation. One is that the humerus superiorly migrates and abuts the underside of the acromion causing a reactive bone spur formation. Another theory is that the humerus continually abuts against the coracoacromial ligament leading to slight bowing of this ligament leading to a traction osteophytes being formed at the insertion. In patients with rotator cuff tears it has been found that some of them have thickened, hypertrophied and shortened coracoacromial ligaments.

Also a common cause of sub-acromial impingement is humerus migration superiorly.  The bursa and tendons abut against the coracoacromial arch leading to pain. When the deltoid fires it causes superior translation of the humerus. If the rotator cuff is not strong enough to provide the stability required during movement then the deltoid forces are not counter balanced, leading to impingement. Also with patients that have GIRD (Glenohumeral internal rotation deficit), sometimes they can get impingement because the posterior capsule tightness will limit IR of GH joint leading to subsequent anterior and superior translation of the humeral head.

Poor scapular mechanics can lead to impingement. Weakness of dorsal scapular stabilizers and tightness of pectoralis minor, short head of biceps and coracobrachialis lead to scapular protraction and anterior tilting. When the scapula is in this position it places the acromion in a more horizontal position, thus there is a relative lowering of the roof of the coracoacromial arch and decrease in the subacromial space. 

References

Wilk K, Reinold M, Andrews J. The Athlete’s Shoulder. 2md ed. Philidelphia: Churchill Livingstone Elsevier; 2009.

 

 

Clinical Effectiveness of Foot Orthotics

Orthotic usage is extremely prevalent in the running population. Orthotics can range from custom-made, custom-fit implements, to off-the-shelf generic insoles.  Their desired purpose allows for wide variety in material, shape, and formation.  Depending on the type of injury, different types of orthotics are thought to provide different functions.  Orthotic intervention can be intended to alleviate symptoms, prevent deformity, and enhance performance.

A review done by Stefanyshyn et al. in 2006, analyzed the effects of foot orthotics on both general and specific running injuries.  Results are summarized in the table below:

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In summary, the above “general” studies found high success rates of orthotic intervention in relieving running injury and pain.  In the studies that directly assessed the effects of orthotics on specific running injuries, relief rates were observed to be generally quite high.  All pain relief rates were above 64% and the average rate was approximately 80%.

Richter et al., performed a systematic review and meta-analysis asking two very important clinical questions regarding foot orthotics: In patients with or at risk for musculoskeletal overuse conditions, do foot orthotics provide clinically meaningful improvements, and are they cost effective? A total of 23 RCTs were included in the systematic review. Overall, the evidence supported the use of foot orthotics to prevent first-time occurrence of lower limb overuse conditions and show no difference between custom and prefabricated foot orthoses.  The evidence was insufficient to recommend foot orthoses for the treatment of lower limb overuse conditions.

A third review by Landorf et al. in 2000, used the following outcome measures to evaluate foot orthotic intervention success: patient satisfaction, pain and deformity, position and motion, muscle activity, oxygen consumption.

 

Patient Satisfaction
– 4 patient satisfaction surveys conducted on foot orthotics

  • In a retrospective study of 180 people with athletic injuries:
    • 70% indicated their orthotics had “definitely helped”
    • 78% felt their “posture had improved”
  • In a retrospective study of 81 people:
    • 91% of patients were satisfied with their orthotics
    • 94% of patients were still wearing their orthotics
  • Gross et al. surveyed 500 long distance runners:
    • 76% reported complete resolution or great improvement of their symptoms
  • It can be concluded that patients are generally very satisfied with their prescribed foot orthotics

 

Pain and Deformity
– Overall, Mixed results. Here is a highlight of the positive studies:

  • Custom fitted foot orthotics with metatarsal padding was shown to relieve sesamoid pain in 8/10 patients.
  • 34/40 patients with plantar fasciitis improved with foot orthotics – also more effective than NSAIDS, and viscoelastic heel cup.
  • Patients with pedal OA wearing prescription orthotics experienced a significantly longer period of pain relief than NSAIDS drug users.
  • Semiflexible functional foot orthotics were significant in reducing symptoms associated with patellofemoral pain syndrome in 102 patients.
  • Foot orthotics significantly decreased plantar callus in people with diabetes and deformity in RA.
  • Functional foot orthotics can prevent and slow the progression of hallux valgus deformity in RA.
  • Military orthotics significantly reduced the incidence of metatarsal stress fractures in low-arched feet and femoral stress fractures in high-arched feet.
  • For patients with OA of the medial knee joint, a wedged insole significantly reduces pain and discomfort.
  • Great results were also yielded with simple inexpensive orthotics: this raises the question of the effectiveness of expensive orthotics versus less expensive methods in reducing symptoms.

 

Position and Motion
– Greatest area of attention in past studies:

  • Functional foot orthotics have been shown to significantly reduce the amount and rate of pronation in walking and running.
  • Other studies have been shown to decrease internal tibial rotation
  • A recent study found that semirigid rearfoot posting significantly changed patella alignment (with the patella moving medially) in participants with excessive rearfoot pronation.
  • Lateral forefoot wedges decreases strain in the plantar fascia.

 

Muscle Activity
– Only one study to date on the effects of orthotics on EMG activity of muscles in the leg. There was a statistically significant increase in the duration of tibialis anterior activity following heel strike in the orthotic condition, and no change in peroneus longus and gastrocnemius.

  • Further research is required.

Oxygen Consumption
– A number of studies have been performed on the effect of orthotics and oxygen consumption.

  • Although the results are mixed, most studies show a negative effect when walking or running in association to oxygen consumption. This confers with research on limb mass and footwear, which shows an overall increase in the weight of a limb causes an increase in oxygen consumption.  The improvement in biomechanical efficiency with the foot orthotics in these studies was outweighed by the negative effect of the weight of the orthotics themselves.

Although several of these studies summarized assessed orthotic usage in conjunction with other treatment modalities, results still look promising.  Although orthotics do, however, appear to have a positive effect on running injuries, a conclusive statement directly linking orthotics to decreasing running injuries is not possible to make based on the current research.  It is more accurate to state that the use of orthotics is associated with a relief from running injuries!

Now for a look at the proposed biomechanical mechanisms at how foot orthotics exert their therapeutic effects upon the body (a few were highlighted in aforementioned studies):

Skeletal Alignment
– Extreme positions of foot varus or valgus are thought to lead to excessive loading conditions during running and subsequent injuries. Excessive eversion during running combined with increased tibial rotation has been proposed to result in overuse injuries.  To only name a few, a wide variety of running injuries including patellofemoral pain, plantar fasciitis, shin splints (medial tibial stress syndrome), achilles tendonitis and stress fractures have been linked to these aforementioned biomechanical risk factors.  With that being said, a primary focus of orthotic intervention is to address foot alignment.  Several studies in the past have shown mixed results regarding whether or not orthotic intervention in runners actually alters foot alignment and indirectly, also skeletal alignment.  Further research is required in this field.

Cushioning of Impact Forces
– Increasing cushioning with the use of orthotics attempts to decrease the magnitude and rate of loading of the external impact forces during heel strike. Large impact forces have been traditionally proposed to be associated with running injuries, but like the idea of decreasing pronation, results from studies have been mixed.  Several studies showed that custom-molded foot orthotics significantly reduce the vertical impact loading rate, while others studies have yielded contrasting results.

Decreasing Muscle Activity
– Several authors have proposed that orthotics should functionally support the preferred movement path of the lower extremities during running. As an example, rather than aligning the skeleton, orthotics may help guide and support the skeleton to most efficiently follow its own preferred path.  If achieved, muscle activity would be reduced since the orthotics would partially replace the function of the muscles in supporting this preferred path.  This, evidently, would yield reduced fatigue and a potential reduction in running injuries.

Reduced Joint Loading
– Another proposed mechanism of orthotics is to attempt to reduce the loading of the ankle and knee joint during running. Internal ankle inversion moments and resultant knee joint moments have been associated with lower extremity running injuries.  Several studies have shown that medial posting has been found to systematically decrease ankle inversion moments.  Like many of these proposed mechanisms, further studies are required in fully understanding these associations.

Other Proposed Orthotic Functions
– It is proposed that orthotics change the lever arm of the ground reaction force about the subtalar joint, influencing the joint power and ultimately work at the joint. An increased sensory feedback under the plantar surface of the foot has also been proposed during running.

Although there are several proposed mechanisms for which orthotics exert their positive effects upon the body, a great deal of them still require further study.  For the time being, it is important that orthotics, do indeed decrease patient pain and increase functionality – the exact mechanism remains to be fully understood.

References

Landorf, K.B., Keenan, A.M. (2000).  Efficacy of foot orthoses – what does the literature tell us?  Journal of the American Podiatric Medical Association.  90(3):  149-158

 Richter, R.R., Austin, T.M., Reinking, M.F. (2011) Foot orthoses in lower imb overuse conditions: a systematic review and meta-analysis.  Journal of Ahtletic Training.   46(1) 103-106

 Stefanyshyn, D.J., Hettinga, B.A.  (2006)  Running injuries and orthotics.  International SportsMed Journal.  7(2): 109-119

 

 

Risk Factors of Neck Pain for the Office Worker

Computer use and neck pain in the office are two continuously growing trends, I thought I would investigate the possible risk factors and predictors towards this seemingly causal relationship. Posture plays a large role in workplace ergonomics and decreased prevalence of musculoskeletal complaints and there are a large number of other contributing variables that largely impact neck pain occurrence in the office.

Cagnie, B., Danneels, L., Van Tiggelen, D.  (2007) Individual and work related risk factors for neck pain among office workers: a cross sectional study.  European Spine Journal. 16: 679-686

 The purpose of this study was to estimate the one-year prevalence of neck pain among office workers and to determine which physical, psychological and individual factors are associated with neck pain. 512 office workers filled out an approved in-depth online questionnaire. Dependent variables tracked in the questionnaire involved the presence of neck pain during the preceding 12 months. Independent variables were broken down into the following categories: individual (gender, age, height/weight, marital status, education, smoking, sleeping hours, leisure time), work-related physical factors (duration of employment, physical tiredness at end of day, physical workload, computer use, breaks during work, climatological conditions), and work-related psychological factors (mental tiredness at end of day, work variation, job satisfaction, and social support).

What they found was that the etiology of work-related neck disorders are multi-dimensional and are associated and influenced by a complex array of individual, physical, and psychological factors.

Key Points:

  • 12-month prevalence of neck pain was 45.5% (18.1% of workers still had continuous pain).
  • 3% of workers reported that there was a relation between their current job and neck complaints
  • 2% reported that their neck complaints started during their current job.
  • 2% went on sick leave due to their neck complaints.
  • Highest prevalence of neck pain in the age group between 40-49 years old.
  • Interestingly enough, hours of sleep at night were not linked to the likelihood of subsequent neck pain.

 

Risk Factor Odds Ratios: Individual Factors

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Risk Factor Odds Ratio: Work-Related Physical Factors

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Risk Factor Odds Ratio: Work-Related Psychosocial Factors

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Some possible explanations towards the strongest risk factors

  • Sex difference: Smaller female stature and lower strength of shoulder musculature (In this study, 18% of females, and 11% of males reported neck pain).
  • Age: Increased neck pain prevalence with increased age may be explained by the increasing degeneration of the cervical spine.
  • Leisure: Stimulation of physical activity may constitute one of the methods of reducing musculoskeletal morbidity in the working sedentary population
  • Positive relation between neck flexion and neck pain – proven to be an increased risk of neck pain in workers who spend a high percentage of their working time with neck flexion.
  • Stationary positions: When performing work with hands/fingers muscles of the neck and shoulders must act as stabilizers (ie: static contraction of the shoulder musculature to keep arms at right angles during computer use, etc). Sitting for long periods of time is normally also accompanied by curvature of the spine and increased pressure on the discs, ligaments and muscles.

Stress: consistent evidence that stress is highly associated with chronic neck pain.

Breaks permit a reduction in exposure but more importantly, also permit muscle relaxation.

 Hush, JM., Michaleff, Z., Maher, CG., et al. (2009).  Individual, physical, and psychological risk factors for neck pain in australian office workers: a 1-year longitudinal study.  European Spine Journal.  18: 1532-1540

 The goal of this study was to prospectively evaluate a range of risk factors for neck pain in office workers as well as to attain an estimate of its 1-year incidence. 53 office workers without neck pain at baseline were studied and followed for one year. Individual, physical, workplace and psychological factors were measured at baseline.

The following predictors were used in this study:

  • Individual factors (age, gender, exercise)
  • Physical factors (C-spine ROM, cervical spine posture, endurance of cervical extensor muscles)
  • Workplace factors (total duration of sitting, sitting time between breaks, psychosocial workplace factors assessed using the job content questionnaire and job dissatisfaction subscale).
  • Psychological distress (anxiety, depression, etc).

What they found after one year was the following:

  • 26 of the 53 office workers (49%) reported an episode of neck pain during the 1-year follow up. (35% received chiropractic / physiotherapy during that time)
  • Major risk factors for neck pain include the female gender, decreased cervical flexion-extension motion, a sedentary lifestyle, depression, anxiety, and psychological stress
    • 3x more likely to develop neck pain in the office if female
    • Exercising more than 3x/week = 1.5x less likelihood of developing neck pain
    • Increased range of C-spine flexion and extension was protective indicating that office workers with a total range >120 degrees were 2.3x less likely to develop neck pain.
    • Office workers with high psychological stress had, on average, 1.6x greater probability of developing neck pain

Conclusive remarks: The female gender and high psychological stress may increase the risk of developing neck pain, whereas a greater mobility of the cervical spine and frequent exercise may be protective mechanisms for the office worker.

Risk Factors for Neck Pain in the Office

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Eltayeb, S., Staal, JB., Hassan, A., et al.  (2009). Work related risk factors for neck, shoulder and arm complaints: a cohort study among Dutch computer office workers. Journal of Occupational Rehabilitation.  19: 315-322

The purpose of this study was to investigate the relationship between work-related physical and psychological characteristics and complaints of the neck, shoulders, and forearms. Data was used from a prospective cohort study among 264 computer office workers with a follow-up period of 2 years. Similar to the 2 studies above, questionnaires were completed and potential risk factors were divided into work-related physical and work-related psychological factors. Potential confounders taken into consideration were age, sex, and previous histories of neck complaints.

After two years of following these office workers, it was concluded that neck complaints had the highest prevalence at 31%. The four main predictors of neck pain in office workers are the following:

  • Irregular head and body postures
  • Task Difficulty / Job Demands
  • Number of working hours per day at a computer
  • Previous history of neck complaints (Odds Ratio of 7.2)

 Conclusion:

The lifetime prevalence of neck pain is over 70%, and point prevalence is between 12% and 34%.  Needless to say, these numbers are even higher for the office worker. From a physiological point of view, the first study by Cagnie et. al. came up with a great explanation for this: “Selective and sustained activation of Type 1 motor units can be seen as the most influential hypothesis for the development of muscle damage due to sustained low-intensity tasks (ie: a desk job). This may lead to calcium accumulation in the active motor units and other homeostasis disturbances due to limitations in local blood supply and metabolite removal in muscle compartment with larger number of active motor units”. A desk job often places continual stress and demands as well as constant contraction on neck/shoulder musculature, and if not kept to a minimum through ergonomic intervention, frequent breaks, and psychosocial health practices, neck pain generally ensues.

From these studies, it is fairly obvious to see that neck pain is a common issue in office workers (especially those with extensive computer use). It is also important to understand that these overlying musculoskeletal neck complaints are often multi-factorial in nature and can occur due to individual, psychosocial, physical, and work-related predictors. In patients presenting with a neck complaint, it is therefore, important to obtain a comprehensive history regarding their day-to-day duties at work. Identifying these factors that predispose individuals to persistent neck problems may contribute to primary and secondary prevention. With that being said, chiropractors can play an imperative role in understanding these above workplace risk factors and educate their patients by gaining awareness and assisting them in minimizing/eliminating these contributing factors at their desks on a daily basis.