Mechanical Testing of Instrumentation: A Test of Mechanics
Ian A. Stokes

Spinal instrumentation has a primarily mechanical function, but mechanical testing procedures are designed more by expediency than by their ability to evaluate whether instrumentation will produce a good clinical outcome. Researachers should focus on determining the mechanical requirements of instrumentation, the biologic response to the presence of pathology, and how this information can assist surgeons in selecting instrumentation in individual cases.

Prenatal Development of the Normal Human Vertebral Corpora in Different Segments of the Spine
Dorrit Nolting, Birgit Fischer Hansen, Jean Keeling, and Inger Kjær

The normal prenatal development of the human vertebral column during a 10-24-week period of gestation was mapped by radiography, histology, and immunohistochemistry. The location of the notochord in the cartilaginous corpora and its disappearance at the onset of ossification were described. The sequence in which the vertebral corpora ossify and the location and morphology of the ossified corpora were mapped. Marked differences occurred in the different segments of the spine. The developments described can serve as morphologic standards for the future evaluation of human prenatal spine malformations.

The Pathogenesis of Schmorl's Nodes in Relation to Acute Trauma: An Autopsy Study
V. Fahey, K. Opeskin, M. Silberstein, R. Anderson, and C. Briggs

Seventy thoracolumbar spines from individuals killed in motor vehicle accidents were examined for pathologic and radiologic evidence of injury, including the occurrence of acute Schmorl's nodes. The study demonstrates a direct causal relationship between Schmorl's nodes and acute trauma.

Preventive Measures of Back Muscle Injury After Posterior Lumbar Spine Surgery in Rats
Yoshiharu Kawaguchi, Hisao Matsui, Ryuichi Gejo, and Haruo Tsuji

During posterior spine surgery, a 5-minute release of back muscle retraction after 1 hour or after each 40-minute period protected severe muscle injury after surgery. Intermittent back muscle retraction produced prompt muscle regeneration and a low incidence of neurogenic muscle changes compared with continuous retraction.

Assessment of Scoliosis Correction in Relation to Flexibility Using the Fulcrum Bending Correction Index
Keith D. K. Luk, Kenneth M. C. Cheung, D. S. Lu, and John C. Y. Leong

A new method of describing frontal plane correction in scoliosis based on accurate flexibility assessment by the fulcrum bending radiograph is described. Descriptions of corrections that take curve flexibility into account allow comparisons to be made between different series.

Results and Morbidity in a Consecutive Series of Patients Undergoing Spinal Fusion for Neuromuscular Scoliosis
Eric R. Benson, Jeffrey D. Thomson, Brian G. Smith, and John V. Banta

The authors retrospectively reviewed 50 consecutive spinal fusions for neuromuscular scoliosis performed between 1990 and 1994 at an experienced center in an effort to compare the current results and complication rate for this procedure with those of the mid 1980s. With a minimum 24-month follow-up period, the authors' early data showed improved technical results with fewer complications than have been reported previously. The authors believe that these better outcomes are a result of technical improvements and experience with perioperative treatment of these fragile patients.

Predicting Return to Work: A Long-Term Follow-Up Study of Railroad Workers After Low Back Injuries
Stephen J. Hunter, Steven Shaha, Douglas Flint, and Diane M. Tracy

Long-term follow-up study of back-injured railroad employees who had undergone intense physical rehabilitation was conducted. Pre- and postrehabilitation measures of strength, range of motion, pain, and self-perception of disability were gathered. Physical/medical, self-reported, employment, and financial data were also collected. Employment and financial factors were most predictive of long-term retention at work.

Health Care and Indemnity Costs Across the Natural History of Disability in Occupational Low Back Pain
David A. Williams, Michael Feuerstein, David Durbin, and John Pezzullo

Health care and indemnity costs for occupational low back pain disability were studied. Consistent with findings of earlier studies, total payments for health care and indemnity increased over time despite a substantial reduction in the number of cases remaining disabled over time. The present findings illustrate how investigation of detailed health care costs across the disability continuum can facilitate critical analyses of utilization patterns and stimulate suggestions for innovative alternatives to existing care.

Cumulative Incidence of Lumbar Disc Diseases Leading to Hospitalization up to the Age of 28 Years
Paavo Zitting, Paula Rantakallio, and Heikki Vanharanta

Lumbar disc diseases are most prevalent in adults. This study shows, however, that the first cases requiring hospitalization appear in patients at the age of approximately 15 years, and the incidence rises more sharply after the age of 19. It might be useful to try to identify risk factors during childhood, i.e., before the age of onset of low back diseases.

Early Active Training After Lumbar Discectomy: A Prospective, Randomized, and Controlled Study
Gunilla Kjellby-Wendt and Jorma Styf

Fifty-two patients with lumbar disc herniation were randomly allocated into an early active treatment program or a control group. Two years after surgery, more patients were satisfied in the early active treatment group.

Pseudarthrosis of the Lumbar Spine: Outcome After Circumferential Fusion
Stanley D. Gertzbein, Michael R. Hollopeter, and Sally Hall

Circumferential fusion in the management of lumbar pseudarthrosisis was highly successful in producing a fusion (100%). However, in this group of patients who are difficult to rehabilitate, the successful clinical outcome regarding pain and return to gainful employment is only slightly better than 50%.

William Jason Mixter (1880-1958): Ushering in the "Dynasty of the Disc"
Robert C. Parisien and Perry A. Ball

William Jason Mixter was one of the key figures in the development of the understanding of sciatica. His 1934 article published with J. S. Barr is widely regarded as one of the reports that markedly increased the popularity of lumbar discectomy for the management of sciatic pain.

Behavioral Responses to Examination: A Reappraisal of the Interpretation of "Nonorganic Signs"
Chris J. Main and Gordon Waddell

Waddell signs in low back pain have been in use for 20 years but are commonly misused, both clinicallly and medicolegally. Behavioral responses to examination provide useful clinical information but need to be interpreted with care and understanding.