Isthmic Spondylolisthesis and Spondylolysis

Steven M. Theiss, MD, Birmingham, Ala, from the Division of Orthopedic Surgery, University of Alabama at Birmingham.

J South Orthop Assoc. 2001;10(3) 

In This Article

Abstract and Introduction

Abstract

Isthmic spondylolisthesis, or spondylolisthesis due to a lesion of the pars interarticularis, is a common source of pain and disability in both the pediatric and adult population. This review examines the current diagnostic and treatment options for patients with this condition. It also reviews the results of the various interventions to facilitate the surgeon in choosing the appropriate treatment option for any given patient.

Introduction

Perhaps no spinal pathology has been the source of as much study and controversy as spondylolisthesis. Although this entity has been the subject of thousands of articles, even today, considerable controversy exists over the best approach to this common problem. The first descriptions of spondylolisthesis were from early obstetricians who reported severe sagittal spine deformities that interfered with normal vaginal delivery. In 1854, Kilian coined the term spondylolisthesis, with spondyl meaning "vertebra" and olisthesis, "to slip." It was soon thereafter that a lesion of the neural arch was recognized as a frequent contributing factor to the slip.[1]

The popular classifications describe the various diseases responsible for the slip. Newman,[1] in 1963, divided the types of spondylolisthesis into five distinct groups, with each subtype emphasizing the lesion in the posterior elements responsible for the slip. The nomenclature for the classification was clarified by Wiltse et al,[2] and this remains the most popular classification system to date. They classified spondylolisthesis as being congenital, isthmic, degenerative, traumatic, and pathologic. Newman[1] later added the classification of iatrogenic spondylolisthesis. While this classification system principally describes the etiology of the spondylolisthesis, it highlights the anatomic lesions responsible for the slip.

The basic lesion in isthmic spondylolisthesis is in the pars interarticularis. Wiltse et al[2] divided this category into three subtypes: lytic, elongated, and acute fracture. The first subtype, the lytic lesion of the pars, is the most common cause of spondylolisthesis and is termed spondylolysis. This defect is present is up to 6% of the population by young adulthood.[3] Numerous authors have postulated both congenital and developmental theories of the origin of pars defects. Developmental fatigue fracture of the pars is suggested by higher incidences of spondylolysis in populations such as football linemen, gymnasts, and weight lifters engaging in excessive or repetitive lumbar extension activities.[4] Conversely, inheritance studies have documented an increased incidence of spondylolysis in first-degree relatives of patients with either congenital or isthmic spondylolisthesis, suggesting a congenital etiology.[5] While spondylolysis is twice as common in males, females are more likely to have a progressive slip.[6] This progression, however, is rare in adulthood.[7] Furthermore, the exact relationship between spondylolysis and back pain is debatable. Natural history studies have shown that a large percentage of patients, even those with significant spondylolisthesis, respond well to nonoperative treatment.[7] The second subtype of isthmic spondylolisthesis -- elongation of the pars interarticularis -- is thought to be due to repetitive microfractures with subsequent healing in an elongated position. Elongation of the pars can also be seen in congenital spondylolisthesis, in which the pars lesion is due to a congenital anomaly of the L5-S1 facet articulation. As the slip progresses, the pars elongates in response to the deformity. Therefore, with an elongated pars, it is important to evaluate the lumbosacral facets to properly classify the lesion. Finally, the third subtype is an acute fracture of the pars, resulting from a single traumatic episode. Wiltse et al[2] suggested that this type of isthmic spondylolisthesis could also be classified as traumatic spondylolisthesis.

Degenerative spondylolisthesis is believed to result from chronic intersegmental instability.[8] Degenerative changes of both the facet joints and the intervertebral disk cause the slip, which is rarely more than a grade I slip. Sagittal orientation of the facet joints and facet tropism also has been related to the development of degenerative spondylolisthesis. Pathologic spondylolisthesis is due to generalized or localized musculoskeletal processes affecting the posterior elements and causing instability. Finally, iatrogenic spondylolisthesis results from excessive removal of the posterior elements after laminectomy.

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