Mark D. Brown

Pathoanatomy and Pathophysiology of Nerve Root Compression

The anatomy and physiology of the nerve root complex in the lumbar spine are reviewed, with special reference to the effects of mechanical deformation of nerve roots in association with intervertebral disc herniation and spinal stenosis. Biomechanical aspects of nerve root deformation induced by compression are discussed. The functional changes induced by compression can be caused by mechanical nerve fiber deformation but also may be a consequence of changes in nerve root microcirculation, leading to ischemia and formation of intraneural edema. Nerve root compression can, by different neurophysiologlc mechanisms, induce motor weakness and altered sensibility or pain. Intraneural edema and demyelination seem to be critical factors for the production of pain in association with nerve root compression.

Bone transplantation and human immunodeficiency virus. An estimate of risk of acquired immunodeficiency syndrome (AIDS).

The possibility of transplanting a bone allograft from a donor infected with human immunodeficiency virus (HIV) is remote, provided there is a combination of rigorous donor selection and exclusion, screening for the HIV antigen and antibody, and histopathologic studies of donor tissues. The chance of obtaining a bone allograft from an HIV-infected donor who failed to be excluded by the above techniques is calculated to be one in well over a million, using average estimates. On the other hand, if adequate precautions are not taken (for example, by testing only for antibodies to HIV), the risk might be as high as one in 161.

Familial predisposition for herniation of a lumbar disc in patients who are less than twenty-one years old.

The parents of sixty-three patients who were less than twenty-one years old and who had operatively confirmed herniation of a lumbar disc were interviewed regarding a history of sever back pain, sciatica, and herniated disc, to determine whether aggregation of herniation of a lumbar disc occurs in families of patients in this young age-group. The parents of sixty-three additional patients who had a non-spinal orthopaedic diagnosis (control group) were matched for age and sex with the study group and were given the same interview. Of the patients who had herniation of a lumbar disc and were less than twenty-one years old, 32 per cent had a positive family history for that lesion compared with 7 per cent of the control group. The relative risk of development of herniation of a lumbar disc before the age of twenty-one years is estimated to be approximately five times greater in patients who have a positive family history. The results indicate a familial basis for herniation of a lumbar disc in patients who are less than twenty-one years old.

Intrinsic disc pressure as a measure of integrity of the lumbar spine

Intradiscal pressure and volume measurements were made In 84 fresh cadaveric lumbar spine disc spaces. The nucleus was injected with a roentgenographic contrast agent under fluoroscopic examination. The intrinsic pressure, the pressure at which the agent entered the disc, and the maximum pressure that the disc could hold were measured. The discs were graded for degeneration. The intrinsic and maximum pressures were found to be inversely related to disc degeneration grade, and directly related to each other. Relatively greater degeneration was found at lower levels of the lumbar spine as compared to the upper levels. The intrinsic disc pressure may prove to be a useful clinical tool in the evaluation of spinal integrity.

A Randomized Study of Closed Wound Suction Drainage for Extensive Lumbar Spine Surgery

Study Design. A prospective randomized study. Objectives. To study the risk of infection, hematoma, and neurologic deficits following extensive lumbar spine surgery in patients with or without prophylactic closed wound suction drain placement. Summary of Background Data. One randomized study assessing prophylactic drain placement in one-level lumbar spine surgery suggested that the use of a wound drain is not effective at preventing infection and may actually increase the rate of this complication. Our study was designed to determine the efficacy of closed wound suction drainage in preventing complications after extensive lumbar spine surgery. Methods. Eighty-three consecutive patients undergoing extensive lumbar spine surgery were prospectively randomized to one of two groups. Forty-two patients had a closed wound suction drain placed before wound closure and 41 patients did not have a drain placed. The two groups were then assessed for differences in postoperative infection rate, incidence of hematoma and neurologic deficits, operating room time, estimated blood loss, hemoglobin and hematocrit values, temperature, dressing drainage, and length of hospital stay. Results. No infections, epidural hematomas, or new neurologic deficits were encountered in either group of patients. The only significant finding was a higher temperature in the “no drain” group the first day after surgery (P = 0.0437). Conclusions. Based on the findings in this and other studies, the decision to use or not use a wound drain following lumbar spine surgery should be left to the surgeon’s discretion.

Consensus summary on the diagnosis and treatment of lumbar disc herniation

Clinicians must not simply decide that a patient with symptoms and a positive diagnostic test has a reason for a specific treatment, and likewise clinicians must not decide that a patient with symptoms and a negative test does not have a clinically important problem. We must also consider the sensitivity, specificity and predictive value of the diagnostic test and the individual characteristics of the patient. Treatment outcome depends on many factors. Point of service decisions vs population based decisions are obviously different. Each patient presents to the treating practitioner on a given day, at a given time, and it is this picture upon which a plan of care is formulated.

Initial-impression diagnosis using low-back pain patient pain drawings

Patient pain drawings were blindly selected from five lumbar spine disorder categories. The drawings were classified by low-back physicians, discriminant analysis, and several computerized artificial neural network configurations. The purpose was to determine the reliability of the patient pain drawing when diagnosing low-back disorders and to delineate the pain mark patterns particular to each disorder by comparing physicians with computerized methods. The physicians averaged 51% accuracy with individual preferences for certain disorder groups. The computerized methods demonstrated comparable accuracy (48%) and more agreement in classification. Associations were found between the predicted pain patterns for each diagnostic group made by an expert and the patterns generated by computerized methods. Variances in these associations are instructive to clinicians for making accurate predictions of diagnosis from pain drawings.

Surgery for Lumbar Disc Herniation During Pregnancy

Study Design The case reports of three pregnant patients with lumbar disc herniation causing cauda equina syndrome or severe neurologic deficits are presented to illustrate that disc surgery during gestation is a safe method of management. Objective To emphasize the importance of recognizing and definitively treating lumbar disc displacement causing neurologic deficits during pregnancy. Summary of Background Data The advent of magnetic resonance imaging and modern surgical techniques for treatment of lumbar disc displacement allows safe management of this condition at any stage of gestation. A review of the literature on the risks of nonobstetric surgery and the risks of delaying disc surgery until delivery shows that operating at any stage during gestation for severe neurologic deficit secondary to lumbar disc displacement is justified. Methods A review of the literature on the use of magnetic resonance imaging scan and nonobstetric surgery during pregnancy was performed. Three case reports of the authors’ patients who had lumbar disc displacement with cauda equina syndrome or severe neurologic deficit are presented. Patients were placed prone on a four-poster frame, and an epidural anesthetic agent was administered. A one-level hemilaminectomy, partial facetectomy, and disc excision were performed in all three cases. Results The methods used for diagnosis and surgical treatment of three patients with disc herniation during pregnancy resulted in a satisfactory outcome for both mother and child. The medical literature supports surgical intervention in pregnant patients with cauda equina syndrome and severe and/or progressive neurologic deficit(s) from lumbar disc displacement at any state of gestation. Conclusion Although extremely rare, cauda equina syndrome and severe and/or progressive neurologic deficit caused by lumbar disc displacement can occur during pregnancy. The prevalence of symptomatic lumbar disc herniation during pregnancy may be on the increase because of the increasing age of patients who are becoming pregnant. These cases showed, and the literature confirms, that pregnancy at any stage is no contraindication to magnetic resonance imaging scan, epidural and/or general anesthesia, and surgical disc excision.

MEASUREMENT OF CADAVER LUMBAR SPINE MOTION SEGMENT STIFFNESS

Study Design. Prospective. Objectives. To measure lumbar spine motion segment stiffness and relate it to the degree of disc degeneration. Summary of Background Data. The association between the instability of the lumbar spine motion segment and disc degeneration remains unclear. The traditional method for determining motion segment instability at the time of decompressive surgery is a manual test performed by the surgeon. To quantify instability of the lumbar spine, a vertebrae distractor was developed in the authors’ laboratory to measure motion segment stiffness by applying a defined load at a constant rate. Methods. Lumbar stiffness was measured by subjecting cadaver lumbar spine motion segments to a constant rate flexion–traction load and recording the magnitude of the resistance to distraction versus the range of motion. Disc degeneration was measured by pressure–volume discography and by grading of disc morphology. Results. Motion segment stiffness decreased with the initial stages of disc degeneration and then increased with severe disc degeneration. This measure of motion segment stiffness correlated well with a manual stiffness measure. Conclusions. The observed results follow an accepted hypothesis of motion segment instability associated with disc degeneration.

Differential Diagnosis of Hip Disease Versus Spine Disease

Many clinicians find it difficult to differentiate between symptoms caused by a spine disorder or a hip disorder. If surgery is indicated, the order in which these operations take place is an important factor in the patient’s long-term outcome. A prospective evaluation and retrospective chart review of patients with lower extremity pain was performed at the principal investigator’s clinic to determine which signs and symptoms best predict the primary source of pain in patients with hip and spine disorders. Medical histories, physical examinations, and diagnostic tests were done on 97 patients with lower extremity pain to determine which signs and symptoms were the best predictors of a primary source of the pain (a hip or a spine disorder). The presence of a limp, groin pain, or limited internal rotation of the hip significantly predicted the diagnosis of a disorder as originating primarily from the hip, as opposed to originating from the spine. Patients with a limp were seven times more likely to have a hip disorder only or a hip and spine disorder than a spine only disorder. Similarly, patients with groin pain or limited internal rotation of the hips were seven and 14 times, respectively, more likely to have a hip disorder only or a hip and spine disorder than a spine only disorder. These variables are of primary importance to the clinician when making a differential diagnosis between hip disease and spine disease.