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Low Back Pain

I. Prevalence

A. 70-80% of people will experience low back pain at some time (second only to a "cold" as most common human affliction).

B. Represents 1/3 of rheumatic complaints in primary care office

C. One year prevalence approximately 15-20%

D. Major cause of loss of time at work and most common cause for those less than 45 years old

E. Workdays lost are reported to be 1400 per year per thousand workers in US and 2600 in Great Britain

II. Acute Low Back Pain

A. Generally less than 6-12 weeks

B. Most common are muscle strain and HNP

C. Onset usually post traumatic event or increased exertion

1. Mechanical Low Back Pain

a. Nachemson has suggested that 90% have mechanical etiology

(1) Mechanical low back pain - defined as pain secondary to overuse of a normal anatomic structure (muscle strain) or pain secondary to trauma or deformity of an anatomic structure (herniated nucleus pulposus).

b. Characteristics exacerbated by certain physical activities (eg lifting) relieved by others (such as assuming supine position).

c. Remaining 10% of adults with back pain have the symptom as manifestation of a systemic illness.

d. Muscle strain: acute back pain limited to the lumbosacral area without radiation below the posterior thigh PE reveals limited range of motion of LS spine with paraspinous muscle contraction.

e. Rx includes modified physical activity, NSAIDs and poss. Muscle relaxants. 

f. Px: 90% will return to baseline in less than 12 weeks.

g. HNP: nerve impingement that radiates from LS spine to below the knee in the anatomic distribution of the affected nerve.

h. Usually occurs with sudden physical effort when trunk flexed or rotated.

i. Increased pain with sitting, driving, walking, coughing, sneezing, straining.

j. PE reveals radicular pain with any method that creates tension on affected nerve. +SLR test.

k. Rx with modified activity, NSAIDs and occasionally muscle relaxants for concomitant spasm. Epidural steroid injections can be helpful.

l. 95% return to baseline in 12 weeks

m. If persistent, radiographic/MR evaluation and possible surgical excision of fragment 

2. Non-mechanical causes of acute LBP

a. Epidural abscess - usually associated with fever, progressive neurologic findings, localized tenderness over affected bone 

(1) MRI localizes

b. expanding abdominal aneurysm - can cause sudden severe tearing pain that radiates from back into legs with increasing intensity 

(1) exam reveals abdominal pulsatile mass

c. vertebral compression fractures - acute localized pain at damaged bone

(1) patients prefer to remain motionless can be identified by x-ray or bone scan.

IV. Differential diagnosis

A. Approach according to presenting symptom

1. Back and leg pain with standing

2. Most common related to degeneration of osseous, articular and ligamentous structures (OA or DDD of spine)

3. Spinal stenosis results when tissues/bony structures narrow canal and impinge neural elements

4. Spinal stenosis symptoms most commonly result from spinal claudication 

a. Pain otherwise similar to OA elsewhere 

b. Morning stiffness of short duration 

c. Pain increased by the end of the day 

d. Limitation in motion may only be mild

e. as severity increases, pain occurs for longer periods and increased 

f. By extension of the spine pain may radiate (referred pain) to other tissue of similar embryologic development

g. paraspinous muscles, posterior thigh (exacerbated by ipsilateral bending to osteoarthritic side - facet syndrome).

h. spinal stenosis may have negative exam unless symptoms present (may have abnormal neurologic exam that may normalize with relief of symptoms).