DISCUSSION
The vacuum sign (of Knuttson) is an important early radiographic finding.1 Essentially, this represents collections of nitrogen gas in nuclear and annular fissures and presents as an area of linear radiolucency in the disc space.2  Studies have shown this to be a common sign of disc aging and degeneration, with an incidence of two to three percent in the general population.2 The collection of nitrogen in the discal fissures is thought to originate from adjacent extracellular fluid. 

In movements of the spine that produce a lowered pressure in the disc, such as in extension, nitrogen is released from the adjacent extracellular fluid and, due to the pressure gradient, accumulates in the discal fissures.  On Magnetic Resonance imaging, the disc shows diminished signal intensity due to dehydration, and a signal void at the vacuum site.  This collection of gas can be made to disappear with spinal flexion and reappear with spinal extension.1,2  Disc infections do not demonstrate this sign, due to fluid collections in the fissures.1,2 Central vacuum phenomena correspond to fissuring of the nucleus pulposus, while peripheral lesions represent rim lesions where the annulus fibrosus has been disrupted from its attachment to the vertebral body margin.2

In the peripheral joints, especially the hip, shoulder, and knee, a vacuum sign does not denote degenerative joint changes.2  This is produced as an accompanying physiologic phenomenon, usually induced by the position of the patient in a position of traction when the exposure was made.  Gas in the symphysis pubis is a normal finding during pregnancy and up to three weeks postpartum and may be seen as a vertical, thin radiolucency.

As the disease process progresses in the disc, the degenerative signs become more severe.  Subluxation phenomena are more readily recognizable, and lateral, anterior, and posterior vertebral body displacements of a measurable degree occur.  Flexion/extension films usually reveal decreased motion in these displaced segments.  Disc height is markedly diminished, with greater than twenty-five percent loss of its vertical dimension.  Loss of disc height can also be due to infection, which should be excluded by careful scrutiny for the loss of the vertebral body endplates.2

Dr. Terry R. Yochum is a second generation chiropractor and a Cum Laude Graduate of National College of Chiropractic, where he subsequently completed his radiology residency.  He is currently Director of the Rocky Mountain Chiropractic Radiological Center in Denver, Colorado, and Adjunct Professor of Radiology at the Southern California University of Health Sciences, as well as an instructor of skeletal radiology at the University of Colorado School of Medicine, Denver, CO. Dr. Yochum can be reached at 303-940-9400 or by e-mail at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

Dr. Chad J. Maola is a 1990 Magna Cum Laude Graduate of National College of Chiropractic.  Dr. Maola is a Chiropractic Orthopedist and is available for post-graduate seminars.  He may be reached at 303-690-8503 or e-mail This e-mail address is being protected from spambots. You need JavaScript enabled to view it .

History and Presenting Symptoms

A 37-year-old female describes a history of occasional pain in her lower back region, most noticeable on the left side.  She states that her low back pain “just seems to come and go,” with no obvious triggering activities.  Her pain is localized to the posterior hip region, and does not extend below the pelvis.  She is a recreational runner who usually enjoys hiking, snowboarding, and occasional soccer games with friends, but she denies any specific injury or trauma to her lower back.  On a 100mm Visual Analog Scale, she rates the pain in her lower back and pelvic region as varying from 30mm to 50mm.  She takes over-the-counter NSAID’s when the pain in her lower back interferes with her daily activities or her job duties as the manager of the local library.

Exam Findings

Vitals.  This active female weighs 162 lbs. which, at 5’10’’, results in a BMI of 23—she is not overweight or obese.  She reports that she works out regularly on the resistance machines at a local exercise center, and runs at least twelve miles each week.  She is a non-smoker, drinks wine moderately, and her blood pressure and pulse rate are within normal ranges (BP: 118/76 mmHg; pulse rate: 64 bpm).

Posture and gait.  Standing postural evaluation finds evidence of a lower iliac crest on the right, but the greater trochanters are level.  The left ilium is rotated forward, with prominence of the left ASIS.  Her knees and ankles are well aligned, but there is obvious medial bowing of both Achilles tendons, with pes planus and hyperpronation bilaterally.  During gait, both feet demonstrate a moderate toe-out.  Inspection of her shoes finds scuffing and wearing at the lateral aspect of both heels.

Chiropractic evaluation.  Motion palpation identifies limitations in segmental motion at the left SI joint, with localized tenderness.  The left SI joint demonstrates loss of end range mobility, and pain is reported during motion testing.  Gaenslen’s and Yeoman’s tests for SI joint dysfunction both cause increased pain when performed on the left side.  Lumbar ranges of motion are within expected norms, and neurologic testing is negative for sensory, motor, and reflexive disorders.

Imaging

A lumbopelvic series (AP and lateral lumbopelvic views) is taken in the upright position during relaxed standing.  The sacral base angle is 38° and the lumbar lordosis measures 46°.  There is no significant discrepancy in femur head or iliac crest heights, and no lateral listing or lateral curvature is noted.

Clinical Impression

Moderate lumbopelvic misalignment, with chronic mechanical dysfunction of the left sacroiliac joint.  Poor biomechanical support is noted in the lower extremities, which exacerbates her lumbopelvic dysfunction syndrome.

Treatment Plan

Adjustments.  Specific chiropractic adjustments for the lumbosacral and sacroiliac joints were provided as needed.  Side-posture adjustments were well-tolerated and resulted in good articular releases.

Support.  She was fitted with custom-made, flexible stabilizing orthotics, based on foot imaging in mid-stance.  The inserts were designed to provide support for her arches and decrease the biomechanical stress on her pelvis and sacroiliac joints during the entire gait cycle.

Rehabilitation.  She was instructed in a daily core strengthening program at home using elastic exercise tubing.  The focus was on activation of her transverse abdominis musculature, for improved spinal-pelvic stability.

Response to Care

This patient responded well to her spinal adjustments, and she adapted very quickly to her orthotics.  She performed her daily home exercise program regularly, and demonstrated good exercise performance at her weekly rehab review sessions.  After eight weeks of adjustments (twelve visits) and daily home exercises, she was released to a self-directed maintenance program.

Discussion

This patient had a chronic pelvic misalignment, which was associated with pronation and biomechanical dysfunction in the lower extremities.  Her chiropractic treatment plan included orthotics to support her strained lower extremities, and specific exercises to improve her core pelvic stability.  She responded well to her adjustments, but also needed support from the orthotics and professional guidance for her corrective exercises.

Dr. John J. Danchik is the seventh inductee to the American Chiropractic Association Sports Hall of Fame.  He is the current chairperson of the United States Olympic Committee’s Chiropractic Selection Program and lectures extensively in the United States and abroad on current trends in sports chiropractic and rehabilitation.  Dr. Danchik is an associate editor of the Journal of the Neuromusculoskeletal System.  He can be reached by e-mail at This e-mail address is being protected from spambots. You need JavaScript enabled to view it .