THE ETIOLOGY OF SPONDYLOLISTHESIS

Lumbar multilevel degenerative spondylolisthesis: radiological evaluation and factors related to anterolisthesis and retrolisthesis

Radiographs of 3,259 outpatients with low back disorders were examined for age, gender, level, direction, degree of slip, lumbar lordosis, pedicle-facet (P-F) angle, facet shape, and disc height. Degenerative lumbar spondylolisthesis was found in 284 (8.7%) of the patients, of which 83 were excluded. Single-level spondylolisthesis was present in 132 of the 201 patients studied, including 93 cases of anterolisthesis and 39 of retrolisthesis, the former being predominant at L4 and in women and the latter at L2 and equal between the genders. Multilevel spondylolisthesis in 69 patients included 65 (94%) of two-segment slip, 21 anterior, 25 posterior, and 19 combined, and 4 cases of three-segment retrolisthesis. Factors related to anterolisthesis were increased P-F angle and W-shaped facet joint; statistically, however, no factors were found statistically related to retrolisthesis. Multilevel anterolisthesis was considered to occur from factors similar to those previously reported for single-level anterolisthesis, and the pathomechanism of retrolisthesis is different from that of anterolisthesis.

Spondylolisthesis in osteogenesis imperfecta due to pedicle elongation: report of two cases

STUDY DESIGN

Two cases of spondylolisthesis due to severe elongation of pedicles in osteogenesis imperfecta are reported.

OBJECTIVE

To describe an unusual type of spondylolisthesis and its successful management.

SUMMARY OF BACKGROUND DATA

Spondylolisthesis is known to occur in osteogenesis imperfecta. Reports in the literature are few. Pedicle elongation resulting in spondylolisthesis has only been reported once. There is no report of a successful treatment of this type of spondylolisthesis resulting from pedicle elongation.

METHOD

Two adolescent girls suffering from osteogenesis imperfecta presented with lower back pain and thoracic scoliosis. One of them had high-grade spondylolisthesis of L3-L4, L4-L5, and L5-S1, with a thoracic scoliosis. She was treated with anterior interbody fusion L3 to sacrum without instrumentation. Later, progression of her scoliosis required combined anterior and posterior instrumented fusion T1 to L1. The other girl presented with L5 spondylolisthesis and thoracic scoliosis. She has back pain as well as neurologic symptoms in her legs and is waiting for surgery.

RESULTS

At the 3-year follow-up the operated patient is symptom-free from her spine and there has been no progression of either deformity.

CONCLUSION

High-grade spondylolisthesis due to elongation of pedicle in osteogenesis imperfecta is uncommon. Anterior interbody fusion of all the involved motion segments has produced good pain relief and arrested deformity progression at the 3-year follow-up.

Treatment of congenital spondyloptosis in an 18-month-old patient with a 10-year follow-up

STUDY DESIGN

Case report.

OBJECTIVES

To present the case of a patient with congenital spondyloptosis treated and followed over 10 years.

SUMMARY OF BACKGROUND DATA

The surgical management of spondyloptosis in children is variably reported in the literature. Some authors propose that posterior fusion in situ is a safe and reliable procedure, whereas others suggest that reduction of the slipped vertebra may prevent some of the adverse sequelae of in situ fusion, which include nonunion, bending of the fusion mass, and persistent lumbosacral deformity. Many investigators advocate a combined anterior and posterior fusion using instrumentation.

METHODS

At the time of the first symptoms an 18-month-old boy with congenital spondyloptosis of L5-S1 was referred to the authors' institution. Because of the progression of pain, neurologic disturbance, mild foot deformity, muscle contractures, and lumbosacral kyphosis, surgical intervention was undertaken. Operative intervention began with a resection of the L5 lamina and wide bilateral L5 nerve root decompression. This was followed by anterior subtotal resection of L5 and interbody bone graft of the morcelized vertebral body for fusion from L5 to S1. The next step was reduction of the spondyloptosis and stabilization by posterior instrumentation L2-S1 with a sacral Cotrel-agraffe device.

RESULTS

The procedure achieved almost complete reduction of the spondyloptosis with near-normal restoration of lumbar lordosis allowing more physiologic lumbar spinal biomechanics. There were no neurologic complications. After surgery there was no suggestion of back pain or gait disturbance and no progression of any deformity.

CONCLUSION

In the treatment of severe congenital spondylolisthesis a staged procedure of decompression, reduction, and instrumented fusion is recommended for those cases in which intervention is indicated.

Osteoporotic spondylolisthesis: a case report

STUDY DESIGN

A case of spondylolisthesis caused by osteoporosis is described.

OBJECTIVES

To describe the different etiologies of spondylolisthesis, and to report a new cause of pathologic spondylolisthesis previously unreported in the literature.

SUMMARY OF BACKGROUND DATA

The literature on the etiology of spondylolisthesis is reviewed. Pathologic spondylolisthesis has been described with structural abnormalities, such as Paget's disease and tumors, but not with osteoporosis.

METHODS

A clinical and radiographic interpretation of the reported case is presented.

RESULTS

De Novo development of a spondylolisthesis at L5-S1 occurred by gradual elongation of the pars interarticularis over a period of 3 years.

CONCLUSION

The reported case adds to the literature on spondylolisthesis by describing another etiology for this conclusion. Osteoporotic spondylolisthesis may well be identified more frequently in the future given the high prevalence of osteoporosis in the elderly.

Radiologic assessment of lumbar intervertebral instability and degenerative spondylolisthesis

Despite many efforts, there is no clear and widely accepted definition of lumbar instability because there are no unquestionable and currently applicable clinical or radiologic criteria available for this entity. This article reviews the current concepts of lumbar instability and the different imaging modalities used to make the diagnosis as evident as possible.

Changes of the sacrum in severe spondylolisthesis: a possible key pathology of the disorder

Deficient development of the posterior lumbosacral portion has been thought to be a possible etiology of severe spondylolisthesis. However, the precise causes of the deformity have yet to be revealed. To our knowledge, progression of the disorder has not been discussed in the light of sacral changes on magnetic resonance imaging (MRI). The objectives of the present study were to document changes of the sacrum on MRI scans in patients with severe spondylolisthesis and to discuss the relation of these changes to the progression of deformities. Roentgenograms and MRI scans of 13 patients (10 women and 3 men) with severe spondylolisthesis were retrospectively reviewed. Average age at first MRI examination was 20 years (range, 12 to 50 years). The MRI scans commonly showed a defect at the antero-superior portion of the sacrum. This lesion seems to appear during the period of progression of slipping associated with lumbosacral kyphosis. The defect of the sacrum was considered a unique feature to discriminate this type of olisthesis from others. Taking into consideration the present results, the deformity can be called kyphospondylolisthesis.

Anterior shear of spinal motion segments. Kinematics, kinetics, and resultant injuries observed in a porcine model

STUDY DESIGN

A basic study of 56 porcine specimens in anterior shear loading.

OBJECTIVES

To determine some modulators of the biomechanics of spinal motion segments exposed to acute shear loading and to identify the resultant injuries.

SUMMARY OF BACKGROUND DATA

Most research on spinal injury mechanisms has focused on compressive loading, leaving a void in understanding of the effect of shear loading on origin of injury.

METHODS

Cervical spines (n = 56) of domestic pigs (6 months old) were loaded to failure in a specially designed jig that restricted their motion to primarily the shear plane. The specimens were tested at load rates of 100 N/sec or 10,810 N/sec and either in a flexed or neutral posture. In addition, the function of the individual structures of the motion segment were determined by serial dissection forming three groups: whole specimens, specimens with no posterior ligaments, and specimens with no posterior ligaments or facet joints. Load-deformation curves were collected using analog-to-digital sampling rates of 50 and 100 Hz. The mode of failure was then documented through systematic dissection of the specimen and/or radiology techniques. Modeling approaches were then used to gain insight into the failure mechanisms.

RESULTS

Dynamic loading (10,810 N/sec) and flexion of the specimens were found to increase the ultimate load at failure when compared with quasistatic loading (100 N/sec) and neutral postures. The disc resisted up to 70% of an applied load, with the pars interarticularis responsible for only 30% of the load. Nonetheless, the pars was the primary site of failure. Furthermore, higher load rates also caused endplate avulsion, specifically in the lateral borders of the anulus.

CONCLUSIONS

The porcine model appears to reproduce injuries found in the data available on human lumbar material. Fractures in the pars interarticularis may not greatly weaken the joint, given the dominant role of the disc, but compromise its normal kinematics. Clinically, this may explain the occurrence of pars fractures, without total disability.

Management of spondylolysis and spondylolisthesis in the pediatric and adolescent population

Spondylolysis and low-grade spondylolisthesis are diagnoses that, for most patients, have a benign prognosis and can be managed nonoperatively. For most symptomatic patients for whom this management fails, fusion in situ yields satisfactory and lasting results and remains the gold standard against which other surgical treatment must be compared. Patients with high-grade slips and slip angles may benefit from instrumented fusion in situ or combined anterior/posterior procedures, or may be considered for reduction and fusion. Reduction maneuvers are technically demanding and carry significant risk of neurologic injury. Surgical experience and in-depth understanding of the indications, the complications, and, especially, the limitations of each technique are required.

Posterior stabilization of degenerative lumbar spondylolisthesis with a Leeds-Keio artificial ligament. A biomechanical analysis in a porcine vertebral model

STUDY DESIGN

The biomechanical characteristics of the Leeds-Keio artificial ligament (Neoligament LTD, England) were assessed in the posterior stabilization of degenerative lumbar spondylolisthesis in a porcine vertebral model.

OBJECTIVES

To evaluate the biomechanical properties of this nonrigid system immediately after instrumentation and during cyclic loading.

SUMMARY OF BACKGROUND DATA

Mochida et al reported an innovative method of posterior stabilization in which the Leeds-Keio artificial ligament was used as a nonrigid instrument. Since 1990, this system has been used successfully to treat a select group of patients with degenerative lumbar spondylolisthesis.

METHODS

Five porcine motion segments (L4-L5) were tested in the intact, destabilized, and Leeds-Keio-instrumented conditions. Specimens were loaded in flexion and extension, and construct stiffness was measured during the initial loading cycle and at 250 cycle intervals for 1500 cycles.

RESULTS

Biomechanical stability in the model of degenerative lumbar spondylolisthesis was inferior to that in the controls. The instability in the Leeds-Keio group significantly improved immediately after placement and after 1500 cycles.

CONCLUSIONS

This system is effective in initially stabilizing an unstable degenerative lumbar spondylolisthesis model and maintains its stabilizing effect during cyclic loading. Therefore, it can offer patients with degenerative lumbar spondylolisthesis in the late static stage several advantages over other treatment methods.

Lumbar olisthesis and lower back symptoms in elderly white women. The Study of Osteoporotic Fractures

STUDY DESIGN

A Cross-sectional study.

OBJECTIVES

To determine the prevalence of lumbar olisthesis among white women aged 65 years and older and its relation to low back pain and back function.

BACKGROUND

Degenerative changes in the lumbar spine of elderly individuals may affect spinal stability, causing olisthesis (subluxation) of the lumbar spine. Neither the prevalence of this condition in the United States nor its relation to back symptoms has been studied previously.

METHODS

Lateral radiographs of the lumbar spine for 788 women aged 65 years and older who were enrolled in the Study of Osteoporotic Fractures were digitized. Olisthesis (antero- and retro-) was assessed at L3-L4, L4-L5, and L5-S1. Back pain and function also were assessed.

RESULTS

When olisthesis was defined as subluxation of 3 mm or more at any of the three levels studied, the overall prevalence of anterolisthesis was 29% and that of retrolisthesis was 14%. In 90% of women with anterolisthesis and 88% of women with retrolisthesis, subluxation occurred at a single vertebral level. The prevalence of anterolisthesis and retrolisthesis did not vary by smoking status, presence of diabetes, or history of oophorectomy. Anterolisthesis was not associated with the presence of back symptoms. Only retrolisthesis at L3-L4 was associated with a statistically significantly increased likelihood of lower back pain, greater severity of back pain, and impairment of back function.

CONCLUSIONS

Anterolisthesis of 3 mm or more in the lower lumbar spine is relatively common among elderly women but is not correlated with back problems. Retrolisthesis at L3-L4 is associated with increased back pain and impaired back function.

Anatomic considerations of the lumbar isthmus

STUDY DESIGN

A morphometric study of lumbar isthmus from L1 to L5 on 30 dried lumbar spines was conducted.

OBJECTIVE

To provide anatomic data about the lumbar isthmus and to quantitatively evaluate structural features of the lumbar isthmus and its relationship to adjacent anatomic structures.

SUMMARY OF BACKGROUND DATA

There are very few anatomic studies about the lumbar isthmus, and no study describes the relationship of the lumbar isthmus to its adjacent structures.

METHODS

Direct measurements using digital calipers and a goniometer were taken from 30 dried lumbar spines. Anatomic evaluation focused on the lumbar isthmus and its related structures, the isthmus pedicle, and superior and inferior facets. Seven linear and four angular parameters of the lumbar isthmus were determined.

RESULTS

The length of the superior edge of the isthmus gradually increased from L2 to L5 (from 8.22 +/- 1.43 mm at L2 to 10.44 +/- 1.90 mm at L5), and that of its inferior edge progressively decreased from L2 to L5 (from 8.67 +/- 1.76 mm at L2 to 6.34 +/- 1.74 mm at L5). The superoinferior diameter of the isthmus decreased from L3 to L5 (from 13.87 +/- 1.77 mm at L3 to 13.26 +/- 2.49 mm at L5). The superior edge of the isthmus was the thinnest at L4 (1.62 +/- 0.58 mm), and its thickness inferiorly increased from L1 to L5 (from 6.71 +/- 1.47 mm at L1 to 7.76 +/- 1.08 mm at L5). The medial and caudal inclination of the isthmus with respect to the pedicle gradually increased from L1 to L5 (from 112.3 degrees +/- 13.8 degrees at L1 to 119.2 degrees +/- 11.2 degrees at L5 medial inclination and from 132.5 degrees +/- 8.8 degrees at L2 to 139.0 degrees +/- 12.1 degrees at L5 caudal inclination, respectively). The dimensions of the lumbar isthmus were positively correlated to dimensions of the pedicle and orientations of the facets.

CONCLUSIONS

This study provides detailed anatomic data of the lumbar isthmus. Anatomic parameters of the lumbar isthmus are related to the vertebral levels and have a significant correlation with the angles of the facets and the dimensions of the pedicles. The vulnerability of the pars interarticularis of the fifth lumbar vertebra has been anatomically confirmed.

Screw placement in the lumbar vertebral isthmus

Anatomic parameters of the isthmus from L1 to L5 were measured in 30 dried lumbar spines. All measured parameters were fairly constant from L1 to L5. The mean values of the core length, thickness of the superior and inferior borders of the isthmus, superoinferior diameter and posterior and medial inclinations of the lumbar isthmus at L5 were 39.9 +/- 2.3 mm, 2.0 +/- 0.9 mm, 8.9 +/- 1.0 mm, 13.2 +/- 2.5 mm, 35.9 degrees +/- 5.7 degrees and 31.8 degrees +/- 6.3 degrees, respectively. This study shows that a 40 mm long, 4 to 5 mm diameter screw should be inserted in the lumbar vertebral isthmus at an angle of 30 degrees laterally and anteriorly.

Clinical outcomes and radiological instability following decompressive lumbar laminectomy for degenerative spinal stenosis: a comparison of patients undergoing concomitant arthrodesis versus decompression alone

One hundred twenty-four patients with degenerative lumbar stenosis underwent decompression with fusion (32 patients) and without fusion (92 patients) during a 30-month period between 1986 and 1988. Patient-reported satisfaction at a mean follow-up period of 5.8 years (range 4.6-6.8 years) revealed a 79% good or fair outcome and a 21% poor outcome (26 patients). Seven patients (6%) developed lumbar instability, three patients (2%) developed new stenosis at an adjacent unoperated level, and three patients (2%) developed a new disc herniation between 2 and 5 years after surgery. Progressive postoperative spondylolisthesis occurred in 31% of patients with normal preoperative alignment (mean 7.8 mm, range 2-20 mm) and in 73% of patients with preoperative subluxation (mean 5.1 mm, range 2-13 mm) in whom fusion was not attained. Radiological progression did not correlate well with patient-reported outcome. The major conclusions from this study are the following: 1) the majority of patients respond well to this surgery, but complication (22%) and late deterioration (10%) rates are not insignificant; 2) radiological instability is common after decompression for degenerative lumbar spinal stenosis, but this correlates poorly with clinical outcome; 3) there are no definitive clinical or radiological factors that preoperatively predict patients at risk for a poor outcome; 4) post-operative radiological instability is more likely to occur when the following criteria are present: preoperative spondy-degenerated L-4 or a markedly degenerated L-3 disc; and when a radical and extensive decompression greater than one level is planned; and 5) the group at greatest risk for a poor outcome consists of those patients with normal preoperative alignment who do not suffer slippage following surgery.

Direct pediculo-body fixation in cases of spondylolisthesis with advanced intervertebral disc degeneration

In inveterate cases of grade 2-3 spondylolisthesis (degenerative or spondylolytic), segmental mobility may be reduced by radiologically confirmed disc resorption. Fusion may be indicated in patients with persistent pain. A simple technique for fusion without reduction of the spondylolisthesis is presented. Fixation of the segment is achieved by two cancellous bone screws inserted bilaterally through the pedicles of the lower vertebra into the body of the upper slipped, vertebra. The cases of 16 patients with an average follow-up of 31 months (range 24-27 months) treated with this direct pediculo-body fixation are presented. Clinical evaluation showed significant decrease in pain and, in patients with concomitant spinal stenosis, walking distance without pain improved from between 500 and 1000 m to more than 3000 m. Radiologically, fusion was observed in all cases. The presented technique of internal fixation of a slipped segment in the degenerative lumbar spine represents a simple minimally traumatic procedure with successful clinical and radiological outcome. Additional procedures, such as decompression of the spinal canal, may be performed.

Orientation of the lumbar facet joints: association with degenerative disc disease

The orientation of the lumbar facet joints was studied with magnetic resonance imaging in 140 subjects to determine if there is an association between facet tropism and intervertebral disc disease or between the orientation of the facet joints and degenerative spondylolisthesis. The 140 subjects were divided into four groups: sixty-seven asymptomatic volunteers, forty-six of whom did not have a herniated disc on magnetic resonance scans (Group I) and twenty-one who did (Group II); forty-six symptomatic patients who had a herniated disc confirmed operatively (Group III); and twenty-seven patients who had degenerative spondylolisthesis at the interspace between the fourth and fifth lumbar vertebrae (Group IV). Axial scans were made at each lumbar level and digitized, and the facet joint angle was measured by two independent observers with use of image analysis software in a personal computer. The technique of measurement of the facet angles on magnetic resonance scans was validated with a subset of subjects who also had computed tomography scans made. Similar values were obtained with the two methods (r = 0.92; p = 0.00001). For the forty-six asymptomatic volunteers who did not have a herniated disc on the magnetic resonance scans (Group I), the median facet tropism was 5 to 6 degrees and was more than 10 degrees in 24 per cent (eleven) of the subjects. There was no association between increased facet tropism and disc degeneration. At the level of the fourth and fifth lumbar vertebrae, the median facet tropism was 10.3 degrees in the symptomatic patients who had a herniated disc at the same level and 5.4 degrees in the asymptomatic volunteers (Group I) (p = 0.05). The mean orientation of the lumbar facet angles relative to the coronal plane was more sagittal at all levels in the patients who had degenerative spondylolisthesis. The greatest difference was at the level of the fourth and fifth lumbar vertebrae (p = 0.000001). The mean facet angle was 41 degrees (95 per cent confidence interval, 37.6 to 44.6 degrees) in the asymptomatic volunteers and 60 degrees (95 per cent confidence interval, 52.7 to 67.1 degrees) in the patients who had degenerative spondylolisthesis. Furthermore, both the left and the right facet joints were more sagittally oriented in the patients who had degenerative spondylolisthesis. An individual in who both facet-joint angles at the level of the fourth and fifth lumbar vertebrae were more than 45 degrees relative to the coronal plane was twenty-five times more likely to have degenerative spondylolisthesis (95 per cent confidence interval, seven to ninety-eight times). The increase in facet angles at levels other than that of the spondylolisthesis suggests that increased facet angles represent variations in anatomy rather than a secondary result of spondylolisthesis.

Pathogenesis of sports-related spondylolisthesis in adolescents. Radiographic and magnetic resonance imaging study

We reviewed radiographs and magnetic resonance images of 77 young athletes with spondylolysis and spondylolisthesis (more than 5% vertebral slip) (slip group). The results were compared with similar studies in 88 patients with spondylolysis only (nonslip group). Endplate lesions were found in all patients in the slip group and in 60 (68%) of those in the nonslip group. Slippage between the osseous and cartilaginous endplates was identified in the T1-weighted sagittal magnetic resonance images and categorized according to the type of slippage: total slip of L-5 or S-1, partial slip of L-5 or S-1, or a combination of these (mixed type). In a study of 31 patients whose slippages progressed, no slippage was associated with the early stage of a pars interarticularis defect. Most vertebral slippages developed or progressed in the cartilaginous or apophyseal stage of the lumbar skeletal age. Wedging of the L-5 vertebral body and rounding of the sacrum progressed as the slippage developed; these did not occur in the nonslip group. These results indicate that the advanced stage of a pars interarticularis defect in an immature spine is a risk factor for spondylolisthesis. The deformities of the lumbosacral spine are thought to be the secondary changes caused by vertebral slippage.

The relationship between isthmic and degenerative spondylolisthesis and the configuration of the lamina and facet joints

Advanced degenerative change in the facet joints leads to displacement of the vertebral body, and the configuration of facet joints and lamina is closely related to the development of degenerative spondylolisthesis. For this study 103 patients and 25 controls were examined with respect to the configuration of the lamina, anteroposterior diameter of the vertebral canal, interarticular distance, interlaminar distance, disc degeneration, and degree of arthritic changes of facet joint, all as shown of plain radiography, and facet angle, interfacet distance, and contour of the canal side of the inferior articular process and lamina, as shown on computed axial tomography. The results of this study showed that those patients with a narrow facet angle were more likely to have developed degenerative spondylolisthesis. If the sum of both facet angles was less than 77.9 degree, the risk of development of degenerative spondylolisthesis was 2.5 times higher than if the sum was greater than 77.9 degree. Those with type N lamina, detected on plain radiographs, were especially likely to have developed degenerative spondylolisthesis. This suggested that degenerative spondylolisthesis may be due to the less effective check mechanism preventing a vertebra from slipping forward on the vertebra below. We recommend fusion of the degenerated spinal segments when operation is considered in cases of acute facet angle with symptoms.

The Stiffness of Human Apophyseal Articular Cartilage as an Indicator of Joint Loading

The stiffness and thickness distribution of healthy lumbar apophyseal cartilage was measured in 25 lumbar motion segments (L1–4). The cartilage indentation and needling techniques of Swann and Seedhom (37) were suitably altered to cope with the low modulus and small size of the joint surfaces. A load of 3.12 ± 0.19 N (mean ± s.d.) was applied to the cartilage through a hemispherical indenter of 4.756 mm diameter. The stiffness was calculated using the displacement and instantaneous load 150 ms and 2 s after the indenter first contacted the surface, and using the equations of both Waters (46) and Hayes et al. (47). The mean stiffness of apophyseal joint cartilage was 2.8 M Pa ± 4 per cent (mean ± 95 per cent confidence limit), and thickness 1.02 mm ± 3 per cent. Peripheral apophyseal joint cartilage was softer than central cartilage. The stiffnesses of the centres of the superior and inferior joint surfaces were 3.01 MPa ± 12 per cent and 3.55 MPa ± 11 per cent. Inferior surfaces had a mean thickness of 0.93 mm ± 5 per cent and stiffness of 2.88 MPa ± 7 per cent. Superior surfaces had a mean thickness of 1.10 mm ± 4 per cent and stiffness of 2.74 MPa ± 5 per cent. It was found that the stiffness of cartilage calculated according to the formula of Hayes et al. (47), based on a constitutive analysis of a thin isotropic elastic layer, was directly proportional to both the stiffness calculated using the semi-empirical formula of Waters (46), derived to describe indentation of thin rubber sheets, and the nominal compressive creep modulus calculated by dividing the mean contact stress by the strain at the deepest point of indentation. The creep modulus calculated 2 s after contact was directly proportional to the creep modulus calculated 150 ms after indenter contact, implying that deformation behaviour was uniform between these points despite variation of cartilage stiffness.

The R-zero line: a new kinematic concept of the lumbar spine

A new kinematic concept is described that relates to the notion that the lumbar spine behaves as a complete structure. This concept is called the "R-zero line" and represents kinematically the neutral position of the lumbar spine between anteflexion and retroflexion. The clinical significance of this parameter is evaluated in normal individuals and in patients with a symptomatic herniated disc at L4-5, with a symptomatic herniated disc at L5-S1, and with spondylolysis/spondylolisthesis. The results of this study show that the R-zero line has a characteristic configuration in all four test groups.

Specific pattern of ruptured annulus fibrosus in lumbar degenerative spondylolisthesis

In order to study the antepriori etiologic factors of degenerative spondylolisthesis, the discograms and CTD were analyzed and the rate of disc slipping and disc indices wer evaluated in 30 cases with degenerative spondylolisthesis. (1) The characteristic S-shaped image which extended from anteroinferior to posterosuperior up to the posterior margin of a vertebral body was observed in 89.7% of slipped discs in lateral discograms. CTD revealed that this image represented a circular splitting in the external and intermediate annulus fibrosus. (2) Discographic degeneration of the discs adjacent to a slipped disc was relatively mild, and their disc indices were not significantly different from those of controls. (3) A negative correlation with r = -0.434 was found between the slipping rate and the disc index. From these results, it was postulated that the site and direction of the circular splitting in laminae of the annulus fibrosus, and the direction of the load applied to an intervertebral disc are important etiologic factors of degenerative spondylolisthesis.

Occupational spondylolysis and spondylolisthesis

Spondylolysis and spondylolisthesis are not uncommon causes of low back pain and sciatica among the general population. Symptoms from these complaints also appear to be increasing in frequency among those who participate in competitive sports, especially those resulting in heavy pressures on the lumbar spine. Neural arch dysplasia is often a predisposing factor and there is evidence that genetic factors may play a role. Isthmic spondylolysis and mild spondylolisthesis not exceeding 10 mm can be satisfactorily cured by a simple operation involving screwing of the defect. Younger patients have better results and the operation permits the patient to withstand double loading on the lumbar spine so that most can return to work, including heavy manual labour, and to their previous sporting activities.

Vertebral displacement in spondylolisthesis

The causes of sagittal displacement in 162 patients with isthmic spondylolisthesis and 81 with degenerative spondylolisthesis have been assessed. The slip ratio was compared with joint mobility, the presence of spina bifida, the lumbosacral angle, a self-assessment of previous athletic ability at school and childhood injuries. There was a correlation between the slip ratio and the lumbosacral angle in isthmic spondylolisthesis ( = 0.39, p < 0·01); but this may be secondary. Metacarpophalangeal joint hyperextension correlated with slip ratio (r = 0·26, p < 0·05). There was no significant difference in slip ratio between the patients with and without spina bifida. Those patients with a childhood injury before 11 years of age had greater displacement than those with a later injury, but this did not reach statistical significance. Many patients with degenerative spondylolisthesis rated their athletic ability at school as 'poor'.

Degenerative spondylolisthesis with unilateral spondylolysis. A case report

Degenerative spondylolisthesis has a different aetiology to that of spondylolisthesis due to bilateral spondylolysis. To our knowledge, a combination of degenerative spondylolisthesis with unilateral spondylolysis has not been described. We report such a case and focus attention on the different mechanisms of spondylolisthesis. The clinical and radiological features of both conditions are clearly illustrated and discussed.

Lateral mass fusion for lower back pain

Forty patients who underwent Wiltse's lateral mass fusion by two different surgeons for spondylolisthesis or degenerative disc disease have been independently reviewed. It was found at follow-up (mean 22 months +/- S.D. 14 months) that factors that affected the final result were the age of the patient, the presence of preoperative nerve root symptoms, previous disc surgery, and incomplete fusion. The duration of symptoms, length of follow-up, preoperative spondylolysis, and the extent of the fusion did not appear to affect the result. This series confirms the previous reports that Wiltse's mass fusion is a good technique for relieving pain in the majority of patients.

Lumbar spondylolysis and spondylolisthesis in college football players. A prospective study

A prospective study was done on Indiana University freshman football players to determine if the incidence of lumbar spondylolysis and spondylolisthesis followed the pattern of previous studies. Using x-ray film evaluation, 145 freshman players were followed through their careers from 1978 to 1983. As in previous studies, a higher percentage (15.2%) of the defect was found than exists in the general population. However, only 2.4% of these players developed the problem in college, a much lower figure than previously found. Affected team members played a variety of positions. In addition to spondylolysis, some other problems, such as spina bifida occulta, were found. Theories on the cause of spondylolysis and spondylolisthesis are reviewed, and preventive suggestions such as more careful training and weight lifting are presented.

The radiographic distinction of degenerative slippage (spondylolisthesis and retrolisthesis) from traumatic slippage of the cervical spine

In a review of 42 cases of degenerative arthritis of the cervical spine and 22 cases of cervical spine trauma with an observed anterior slippage (spondylolisthesis) or posterior slippage (retrolisthesis) of the vertebral bodies of 2 mm or more, characteristic features were observed which allowed distinction between degenerative and traumatic slippage of the cervical spine. In degenerative slippage the shape of the articular facets and width of the facet joint space may remain normal; however, in most cases the articular facets become "ground-down" with narrowing of the facet joint space and the articular facets themselves becoming thinned or ribbon-like. In traumatic slippage the articular facets will either be normally shaped or fractured and the facet joint space will be abnormally widened. Plain radiographs will usually allow this distinction to be made; however, in difficult cases polytomography may be required.

CT in low back and sciatic pain due to lumbar canal osseous changes

In a consecutive series of 600 patients scanned by CT for various spinal diseases, those with low back and sciatic pain without disc herniation were selected for study. The causes proved to be joint facet degeneration (32 cases), stenosis of the neural foramina (13 cases), stenosis of the spinal canal (13 cases), lateral recess stenosis (6 cases) and spondylolisthesis (6 cases). The predominance of joint facet pathology as the underlying cause of low back and sciatic pain in the absence of disc herniation is confirmed. CT scanning of the soft tissues as well as of the skeletal structures is crucial to the aetiological diagnosis of the condition under study and hence to the proper planning of treatment.

Intact arch spondylolisthesis. A review of 50 cases and description of surgical treatment

Over the past 11 years, the authors have treated 50 cases of intact arch spondylolisthesis. There were 38 female and 12 male patients, and all but 11 were older than 60 years of age. Almost all had severe low-back pain made worse by standing or walking. Other common manifestations were unilateral leg pain, numbness or weakness of the leg, and evidence of mild cauda equina compression. Severe cauda equina compression was rare. Myelography invariably showed an extradural dorsal compression. A waist deformity was characteristic in many patients, but 12 had a complete block. In 15 patients (30%) the myelographic impression was that of a herniated intervertebral disc. Most subluxations were of L-4 on L-5. At operation, the facets were found to be thickened, distorted, and irregular. All patients were treated with a wide decompression and laminectomy, which included a medial facetectomy of the inferior and superior facets. An intervertebral disc was removed in 10 patients. Follow-up monitoring of 41 patients (for an average period of 36 months) showed that 26 (63%) were pain-free, 11 had less pain, and four were unimproved. Five other patients with short follow-up periods (average 5 months) were all improved.

Jogger's fracture and other stress fractures of the lumbo-sacral spine

The posterior rings of the lower lumbo-sacral vertebrae are subject to stress fractures at any part - pedicle, pars, or lamina. The site of fracture is apparently determined by the axis of weight bearing. The three illustrative clinical examples cited include a jogger with a laminar fracture, a ballet dancer with pedicle fractures, and a nine-year-old boy with fractures of pars and lamina. Chronic low back pain is the typical complaint with stress fractures of the lower lumbo-sacral spine. Special imaging techniques are usually needed to demonstrate these lesions, including vertebral arch views, multi-directional tomography, and computed tomography (CT).

Myelography in severe lumbosacral spondylolisthesis

The radiological and myelographic appearances of 14 patients with severe lumbosacral spondylolisthesis have been reviewed in relation to compression of the cauda equina and their clinical symptomatology. Patients could be separated into two groups as defined by the position of the L5 neural canal. In Group 1, the arch was displaced downwards and the cauda equina compression was due to pressure from the L5/S1 disc and was related to the degree of listhesis. L5 root sheath abnormalities predominated in this group. In Group 2 the neural arch maintained a more normal position and the compression, which was unrelated to the degree of slip, occurred between the arch and the posterior aspect of the sacrum. S1 root lesions occurred in these patients due to pressure from the arch. Clinical symptoms and signs were also more prominent in this group.

Functional myelograhy in spondylolisthesis

Flexion and extension radiographs in myelography in preoperative spondylolisthesis patients were studied. Dural sac motion at the level of the mid-vertebral bodies was essentially anterior in extension. At the level of the intervertebral disc, the motion is obstructed by the disc bulging posteriorly in extension. Axial motion is variable and not linearly correlated with spinal column length change. The dural sac undergoes a localized narrowing at the level of the spondylolisthesis. This becomes more prominent during extension. In 21 cases studied completely, no disc herniation was encountered myelographically of surgically. The anterior epidural space is of a greater value at the level of the spondylolisthesis than reported normal values. The change in this space from dorsiflexion to ventral flexion is much less at the level of olisthesis than either the adjacent areas of a comparable adjacent intervertebral level.

Strain on the interarticular stress distribution. Measurements regarding the development of spondylolysis

In discussion the aetiology of spondylolysis, attention has been increasingly directed to the biomechanics of the lumbar vertebral column and the lumbo-sacral transition. The theory of a traumatic induction of spondylolysis was tested with stress distribution measurements on the vertebral column of cadavers. Using stretch measuring strips it was possible to investigate, the strain exerted upon the interarticular portion of the intact lumbar vertebral column preparation. A particular strain upon the pars interarticularis occurs through hyperextension, axial stress and torsion of the lumbar vertebral column. It is worth to be mentioned that force transmission within the vertebral arch structures is influenced by the positioning of the vertebral arch joints. Sagittaly positioned vertebral arch joints lead to a greater strain exerted upon the interarticular portion. Our results have to be compared with those of others, who are of the opinion that spondylolysis is a condition resulting from a fatique fracture.

Spondyloysis. The role of the posterior elements in resisting the intervertebral compressive force

Compressive tests were carried out on cadaveric lumbar intervertebral joints, before and after the neural arch was fractured. The results show that although the neural arch can play some part in resisting the intervertebral compressive force, there is no bony contact between the downward projecting tips of the inferior articular processes and the laminae of the vertebra below.

Familial occurrence of lumbar spondylolysis and spondylolisthesis

In a Finnish kindred consisting of 192 descendants from two marriages of a male ancestor born in 1868, the lumbar spines of 105 of the 170 living members were X-rayed. Spondylolysis was found in 22 individuals. In addition, six of them had spondylolisthesis, four had spina bifida occulta, and two had a transitional lumbar/sacral vertebra. Seven members of the kindred without spondylolysis had spina bifida occulta and 10 had transitional lumbar vertebrae. The pedigree is consistent with autosomal dominant inheritance and incomplete (about 75%) penetrance for spondylolysis. It raises the question of a common aetiology for several congenital disturbances in the formation of lumbar vertebrae and possibly supports the concept of variable expressivity of a "spondylolysis gene".