Is lumbar spondylosis a cause of urinary retention in elderly women?

OBJECTIVES

Lumbar spondylosis (LS) is a common spinal degenerative disorder which causes various types of lower urinary tract dysfunction (LUTD). However, it is not certain whether LS may cause urinary retention in elderly women.

METHODS

In a period covering the past 3 years, we retrospectively reviewed: a) urodynamic case records of women with urinary retention (post-void residuals, PVR > 100 ml), b) the records of women with LUTD due to LS (cauda equina syndrome and spinal canal narrowing by MRI), and c) uro-neurological features of women who belonged to both a) and b).

RESULTS

a) One-hundred women with a mean age of 58 years had urinary retention. The most common underlying disease was multiple system atrophy [19], followed by multiple sclerosis [13] and cervical/thoracic tumours [8]. LS was the fourth most common [5], with the highest age (71 years) of all diseases. b) Nineteen women with LUTD had LS (12, canal narrowing of 50-70%; 7 > 70 %), with a mean PVR volume of 60 ml. A fourth [5] of them had urinary retention, with severe spinal canal narrowing (all 5 > 70%). c) Thus, 5 women belonged to both a) and b). In 4 of these women, LUTD followed or occurred together with typical cauda equina syndrome symptoms such as sciatica and saddle anesthesia. However, one elderly woman presented with painless urinary retention, and absent ankle reflexes were the sole neurological abnormality. The urodynamic abnormalities underlying urinary retention included an underactive detrusor in all 5, bladder sensory impairment in 3, an unrelaxing sphincter in 2, a low compliance detrusor in one, neurogenic sphincter motor unit potentials in 2 of 4 studied, and cholinergic supersensitivity of the detrusor in one of 3 studied. Surgical decompression ameliorated urinary retention in 1 of 2 women who had surgery.

CONCLUSIONS

In our series, only 5 percent of the women with urinary retention had LS, but LS poses a potential risk for retention, particularly in elderly women with severe spinal canal narrowing. Preganglionic somato-autonomic dysfunctions underlie this condition. It may appear as the sole initial complaint in cases in which no other obvious neurological abnormalities are found.

Scoliosis research society outcome instrument in evaluation of long-term surgical results in spondylolysis and low-grade isthmic spondylolisthesis in young patients

STUDY DESIGN

A retrospective follow-up study of low-grade (slip < or = 50%) isthmic spondylolisthesis after posterior or posterolateral fusion in young patients.

OBJECTIVE

To evaluate the usefulness of the Scoliosis Research Society questionnaire and compare it with Oswestry Disability Index and radiographic parameters in patients with isthmic spondylolisthesis.

SUMMARY OF BACKGROUND DATA

A few studies have examined long-term patient outcome using validated questionnaires or compared it with radiographic parameters after surgery for isthmic spondylolisthesis in young patients. The Scoliosis Research Society questionnaire provides patient-oriented information on back pain, cosmetic aspects, patient satisfaction, and level of activity and might therefore be suitable for evaluation of surgical outcome after isthmic spondylolisthesis in young patients. However, there are no studies assessing the usefulness of the Scoliosis Research Society questionnaire for these patients.

METHODS

One hundred and eight patients treated at a mean (range) age of 15.9 (range, 8.1-19.8) years with posterior (n = 29) or posterolateral (n = 79) in situ fusion for isthmic spondylolisthesis participated in the present study. The follow-up rate was 83% after a mean of 20.8 (range, 15.1-25.9) years. The mean age at follow-up observation was 36.7 years. Radiographs were obtained before surgery, at 2-year follow-up observation, and at final follow-up review. The Scoliosis Research Society and Oswestry Disability Index questionnaires were completed, and a physical examination was performed at the final follow-up visit.

RESULTS

Nonunion after primary operation was found in 10 (34%) patients after posterior fusion and in 10 (13%) patients after posterolateral fusion (P = 0.0017). The mean (range) anterior slip was 25.2% (0-50%) before surgery and 24.2% (0-78%) at final follow-up observation. Lumbosacral kyphosis increased significantly during the follow-up period. The Scoliosis Research Society questionnaire yielded a total of 94.0 (range, 44-114) points. On the Scoliosis Research Society questionnaire, 14 (14%) patients reported back pain often or very often at rest. The Oswestry Disability Index scores averaged 8.2 (range, 0-68). There was a significant correlation between the Scoliosis Research Society total score and the Oswestry Disability Index. The percentage slip showed significant inverse correlations with the scores for appearance in clothes, attractiveness, and self image (Scoliosis Research Society questions 5, 14, and 15).

CONCLUSIONS

Long-term clinical and radiographic outcomes after posterolateral fusion of low-grade spondylolisthesis were satisfactory. Cosmetic aspects of this deformity should be included as one of the outcome measurements, since cosmetic questions on the Scoliosis Research Society questionnaire showed inverse correlations between the amount of slip at final follow-up observation. The Scoliosis Research Society questionnaire could be used as a primary patient-oriented outcome tool after back surgery in young patients.

[Spondylogenic hypertension of deep veins of the brain]

The cerebral deep veins hypertension criteria using bloodstream in large cerebral vein (Galen's vein) are worked up. An increase in venous pressure was proved to be connected with congenital and acquired pathology of cervical spine and craniovertebral isthmus. The new roentgenologic sign of pathology located in craniovertebral isthmus is determined. It is characterized by abnormal high front arc of the atlas, that hinders the outflow of venous blood from the cranial cavity.

Degenerative disc disease in childhood and adolescence

Degenerative disk disease (DDD) is a common cause of low back pain and leg pain in children and infants. DDD is often unrecognized and under-diagnosed. This paper presents six cases of DDD in children and discusses the clinical presentation and pathophysiology of DDD.

Effect of Postoperative Lumbar Sagittal Alignment on the Development of Adjacent Instability

OBJECTIVE

This study investigated the effect of postoperative lumbar sagittal alignment on the development of adjacent segment instability.

METHODS

The patients were retrospectively divided into two groups (hypolordotic and hyperlordotic) using the lumbar lordosis on lateral lumbosacral view. Diagnosis of adjacent segment instability depended on the dynamic lateral views of the lumbosacral spine.

RESULTS

Thirteen (21.7%) cases developed adjacent segment instability during the 6-year follow-up. The two groups had no significant difference in rates of developing adjacent segment instability.

CONCLUSION

Restoring the lordosis of the lumbar curve during one motion segment fusion does not prevent the development of adjacent instability.

A biomechanical study of lumbar spondylolysis based on a three-dimensional finite element method

Biomechanical analyses under compression only, and for a combination of flexion, extension, rotation, and lateral bending were performed to evaluate the stress of the interarticular portion of the lumbar vertebra using a nonlinear three-dimensional finite element method. A detailed three-dimensional L4-L5 motion segment model was developed that took into consideration the material nonlinearities of ligaments and annular fibers and the contact nonlinearities of facet joints. For a more accurate examination, the separation of cortical bone and cancellous bone for both posterior and anterior elements were also considered. The stress in the pars interarticularis was weakest under compression alone, but stronger under compression with lateral bending loading, with flexion, with rotation, and with extension. Under each loading condition, the region of the stress concentration was consistent with the separated region of the spondylolysis observed in clinical situations. Since the stress in the pars interarticularis was high under extension and rotation in particular, those loadings were suggested to be relatively high risk factors leading to spondylolysis.

Effects of lumbar spinal fusion on the other lumbar intervertebral levels (three-dimensional finite element analysis)

The risk of accelerating the degeneration of adjacent disc levels after lumbar spinal fusion is a controversial issue. A finite element model consisting of L1 to L5 lumbar spines was used to assess the effect on adjacent disc level after lumbar spinal fusion. We compared intact, L4/5 posterior interbody fusion (PLF), and L4/5 posterior lumbar interbody fusion (PLIF) models. The loading conditions applied were compressive force, compressive force plus flexion moment, and compressive force plus extension moment. Evaluations were made for von Mises stress on each vertebral end-plate, Tresca stress of all the annulus fibrosus, and Tresca stress of the annulus fibrosus from the posterior surface of the disc to the neural foramen. As the result, the von Mises stress adjacent to the fusion level was higher than the other nonfusion levels; it was higher under conditions of flexion moment loading plus compression loading [112% (2.59 PMa) in the PLF model and 117% (2.72 Mpa) in the PLIF model] than in the intact model. The Tresca stress of all the annulus fibrosus adjacent to the fusion level was higher than that on other nonfusion intervertebral levels; it was higher under conditions of flexion moment loading plus compression loading [127% (0.57 PMa) in the PLF model and 209% (0.89 Mpa) in the PLIF model] than in the intact model. The Tresca stress of the annulus fibrosus from the posterior surface of the disc to the neural foramen adjacent to the fusion level was higher than that on other nonfusion intervertebral levels; and it was higher under conditions of flexion moment loading plus compression loading [107% (1.48 PMa) in the PLF model and 112% (1.54 Mpa) in the PLIF model] than in the intact model. These findings demonstrate that with lumbar fusion, stresses on the vertebral end-plate and the annulus fibrosus were high adjacent to the fusion level; furthermore, stresses were higher in the PLIF model than in the PLF model. These results suggested that lumbar spinal fusion might bring with it a risk of damage to the annulus fibrosus and the vertebral end-plate adjacent to the fusion level.

Back injuries in young fast bowlers--a radiological investigation of the healing of spondylolysis and pedicle sclerosis

OBJECTIVE

To demonstrate the efficacy of various radiological diagnostic modalities in assessing lower back pain in young fast bowlers.

METHODS

Ten cricketers who presented to either a physiotherapist or a doctor with suspected spondylolysis underwent an X-ray, a single photon emission computed tomography (SPECT) bone scan and a computed tomography (CT) scan to assess the severity of the injury. Three and 12 months after the initial CT scan, second and third CT scans were performed in order to assess whether healing had taken place. After the initial radiological investigation the subjects diagnosed with spondylolysis or pedicle sclerosis underwent prescribed intervention and rehabilitation which included physiotherapy modalities, postural correction, and specific individually graded flexibility, stabilisation, strengthening and cardiovascular programmes.

RESULTS

Radiographs were normal in 8 subjects, while 2 had evidence of sclerosis. The isotope scan showed increased uptake in all of the subjects. The CT scans showed no fracture (N = 3), partial fractures (N = 3), complete fractures (N = 2) and old fractures bilaterally (N = 2). When the follow-up CT scan was carried out at 3 months, 1 of the subjects had developed a partial fracture of the left pars interarticularis on the inferior border, which showed complete union when CT scanned at 12 months. At 3 months the partial and complete fractures showed progressive healing in 2 subjects, with complete healing in all the other cases. Complete healing was achieved in all subjects at 12 months, with the exception of 1 subject who showed near-complete union, with a small area of fibrous union on the inferior border and 2 old bilateral fractures that remained un-united.

RESULTS

From the results it is evident that when a young fast bowler presents with backache after bowling, it would be appropriate to do an X-ray, a bone scan and a CT scan to make the diagnosis. Discontinuing the fast bowling and following an active rehabilitation programme should result in spontaneous resolution and healing of the fractures. If it is not detected early a fibrous or non-union fracture could result.

[Treatment of spondylolysis and spondylolisthesis with posterior STB thoracolumbar transpedicular screw-plate spine fixation system]

OBJECTIVE

To observe the clinical effect of a self-designed posterior STB thoracolumbar transpedicular screw-plate system in the treatment of spondylolysis and spondylolisthesis.

METHODS

This STB screw-plate system is developed with titanium alloy (TC4, Ti6Al4V). During December, 1999 and January, 2001, this system was applied in 51 cases, including lumbar spondylolysis and spondylolisthesis (36 cases), degenerative lumbar instability (15 cases). The patients were aged 22 - 78 years, mean age: 47.5 - years; among them there were 14 male cases, 37 female cases; There were 15 cases degenerative spondylolisthesis with grade I-II slip, 36 cases of spondylolysis and spondylolisthesis, including 34 cases with grade I-II slips and 2 cases with grade III slips; single level of 33 cases, two levels 3 cases. Decompression was performed for the 43 cases with interbody fusion using iliac crest or bilateral-lateral fusion using demineralized bone matrix and 8 cases were fixed with demineralized bone matrix fusion without decompression.

RESULTS

All the operations heeded about 60 - 120 minutes, and during the operations bleeding amounts were 200 - 500 ml. The cases completely recovered to work or normal action after 3 months of surgeries. 46 of all cases were achieved to satisfactorily reduction and clinical effect, 5 cases of grade II-III remained incomplete reduction (grade I slip).

CONCLUSION

This STB system has advantages of biomechanical stability and reduction capability and its effect in clinical application is undoubtedly positive.

The pathogenesis of slippage and deformity in the pediatric lumbar spine: a radiographic and histologic study using a new rat in vivo model

STUDY DESIGN

Rat lumbar spines with posterior destabilizing surgery were evaluated radiographically and histologically.

OBJECTIVES

To create an appropriate rat model showing the vertebral slippage and deformities frequently observed in pediatric patients with spondylolysis, and to clarify their pathogenesis.

SUMMARY OF BACKGROUND DATA

There are controversial hypotheses regarding the pathogenesis of slippage and deformities of the pediatric spine with pars defects. Furthermore, there is no appropriate animal model mimicking those conditions.

METHODS

After posterior destabilizing surgery, the lumbar spines of young (4-week-old) and adult (26-week-old) rats were radiographically examined at weekly intervals during 3 weeks, and histologically 3 weeks after the surgery.

RESULTS

Slippage occurred in the young rats, but not in the adult rats. In the young rats, 7.2% slippage was observed 1 week after the surgery, whereas the slippage in the adult rats was 0%. The difference in percentage of slippage between the two groups was significant (P < 0.05). Lumbar deformity also was seen in the young rats, but not in the adult rats. The lumbar index of L6, as an indicator of L6 rounding, was 91.7% immediately after surgery. It had decreased to 87.7, 84.6, and 74%, respectively, 1, 2, and 3 weeks after surgery. Histologic examination showed growth plate injury in the young group and pronounced disc degeneration in the adult group.

CONCLUSIONS

The young rat with posterior destabilizing surgery was an appropriate animal model, mimicking the slippage and deformities radiographically seen in pediatric patients with spondylolysis. The histologic examination indicated that vertebral growth plate impairment was the basic lesion causing such slippage and deformities in pediatric spines.

Spondylolysis of L2 in identical twins

OBJECTIVE

To discuss the presence of spondylolysis at L2 in identical twins.

CLINICAL FEATURES

Twin 61-year-old brothers reported insidious low back pain (LBP) of relatively recent onset. Both engaged in running as their main form of exercise. One had spondylolisthesis and history of significant traumatic incident; the other had no spondylolisthesis but a much more strenuous running regimen.

INTERVENTION AND OUTCOME

Both patients underwent a course of chiropractic treatment for mechanical LBP and reported a 50% overall improvement in symptoms.

CONCLUSIONS

Spondylolysis at L2 is uncommon, and although a familial component regarding weakness of the pars interarticularis has been demonstrated in the literature, spondylolysis at L2 in twins is extremely rare. Questions remain regarding the cause of spondylolisthesis in patients.

The biomechanical effects of spondylolysis and its treatment

STUDY DESIGN

Biomechanical analysis of the level above pars defects was performed using calf lumbar spines.

OBJECTIVES

To evaluate whether complete spondylolysis contributes to the pathology of the upper adjacent motion segment to the pars defect.

SUMMARY OF BACKGROUND DATA

It is well recognized that patients with spondylolysis show a higher incidence of spondylolisthesis or degenerative disc changes at the level of the pars defects. However, some authors have referred to the fact that disc damage may occur at the level above the defect and give rise to symptoms. However, no previous studies have been directed to the kinematic influence on the upper adjacent segment to pars defects.

METHODS

Nine fresh-frozen calf lumbar spines were used for this study. The bony defects were created on the L4 pars articularis bilaterally. Three linear extensometers and one specially designed angular extensometer were mounted across the L3-L4 and L4-L5 motion units. Nondestructive static loads, including axial compression, flexion-extension, and axial rotation, were applied on the specimens in four different conditions as follows: 1) intact spine; 2) bilateral pars defects on the L4 laminae; 3) pars defect repair with Buck technique; and 4) pedicle screw-rod fixation at L4-L5 after removal of the interarticular screws. Testing was performed on a material testing machine (MTS 858 Bionix test system, Minneapolis, MN), and load-displacement curves were recorded with the extensometers. Each test was performed for over five full sinusoidal loading cycles, and data from the fifth cycle were collected and analyzed.

RESULTS

After creating the pars interarticularis defects at L4, mobility at both the L3-L4 and L4-L5 motion units were increased in all loading conditions. The normalized range of motion (% ROM) as compared with the intact specimens showed that the pars defects increased the mobility at the upper adjacent level (L3-L4) to 106.4% in flexion-extension and to 120.1% in axial rotation; the differences were significant (P < 0.01). Consequently, the increased mobility was stabilized by applying Buck screws through the defects on both sides; however, the effect was not statistically significant. Furthermore, pedicle screw-rod fixation applied at the L4-L5 segment increased the intervertebral motion at the upper adjacent level, and % ROM in axial rotation was significantly increased to 119.2% of the intact spine (P < 0.05). Comparing the treatments' effects on the L3-L4 segment and that on L4-L5, the Buck screws restored the stability of both segments to the level of the intact spine, whereas the pedicle screw system limited the motion of L4-L5 motion and, on the contrary, increased the L3-L4 motion.

CONCLUSIONS

This biomechanical study exhibited that bilateral pars interarticularis defects increased the intervertebral mobility, not only at the involved level but also at the upper adjacent level to the lysis. The increased mobility at the upper segment was reduced by the Buck screw technique. However, this was increased again by the pedicle screw system applied on the involved segment. If clinically applicable, fixation of the pars defect alone appears to cause less adjacent level mechanical stress than pedicle screw-rod motion segment fixation.

Intra-individual variation in lumbar bone mineral density as a measure of spondylotic deformity in the elderly

In an attempt at quantitative assessment of spondylotic deformity, the intra-individual variation in L(1)-L(4) bone mineral density (BMD) was calculated, as the standard deviation (SD) and coefficient of variation (CV), obtained by dividing the SD by mean L(1)-L(4) BMD, in 463 subjects. The subjects ranged in age from their second to tenth decades. Dual-energy X-ray absorptiometry (DXA), using the Lunar DPX-L, was employed to assess the BMD. The SD of lumbar (L)BMD increased with advancing age in males, but not in females, whereas the CV of LBMD increased with age in both males and females, along with the radiographically assessed degree of severity of spondylosis deformans. Both the intra-individual SD and CV of L(1)-L(4) BMD showed a highly significant correlation with the radiological degree of severity of spondylosis deformans, and SD, but not CV, showed a strong dependence on the mean L(1)-L(4) BMD on a multiple regression test. Multiple regression test revealed no significant correlation between on body height, weight, fracture, and intra-individual variation in L(1)-L(4) projected area, reflecting compression fracture, one hand and SD or CV of L(1)-L(4) BMD on the other. Intra-individual variation in lumbar bone mineral density, expressed as a coefficient of variation, is suggested as an index of spondylotic deformity.

New strategies in the management of low back injuries in gymnasts

Low back pain is an extremely common complaint in competitive gymnasts, and these athletes are at risk for multiple potential structural injuries to the spine. Of particular concern among gymnasts is spondylolysis. Unfortunately, there are no published, controlled trials on the diagnosis or treatment of spondylolysis in adolescent athletes. However, based on the current literature, there would appear to be little role for the use of plain radiography in the diagnosis of symptomatic spondylolysis; nuclear imaging with single photon emission computed tomography (SPECT) appears to represent the best screening tool for diagnosis. Given the limited specificity of nuclear imaging in the spine, it is generally best to follow any positive study with a limited thin-cut computed tomography scan of the region of concern on the SPECT. Treatment should be based on the radiographic stage of the lesion. Relative rest is an essential component of care. Although the rehabilitation of gymnasts with lumbar injuries is poorly studied, the related literature would support incorporating the concepts of dynamic lumbar stabilization and sport-specific training into their rehabilitation programs.

Spondylolysis: returning the athlete to sports participation with brace treatment

Between 1988 and 1995, 73 adolescent athletes treated with the Boston Overlap Brace for spondylolysis were reviewed to evaluate improvement in pain score and activity level. A favorable clinical outcome was achieved in 80%. Girls and boys who participated in high-risk sports were five times more likely to have an unfavorable clinical outcome than those who participated in low-risk sports (odds ratio = 5, 95% confidence interval = 2.4-7.5, P = .003). In addition, acute onset of pain and hamstring tightness were associated with a worse outcome. Athletes with symptomatic spondylolysis treated with an antilordotic brace can expect improvement in their clinical course and return to sports participation in 4-6 weeks.

Normal and spondylolytic pediatric spine movements with reference to instantaneous axis of rotation

STUDY DESIGN

A radiologic study of lumbar kinematics in the pediatric spine was conducted.

OBJECTIVES

To clarify the kinematic alteration in the pediatric spine with pars defects by measuring the location of the instantaneous axis of rotation.

SUMMARY OF BACKGROUND DATA

Vertebral slippage and deformities such as wedging of L5 are observed frequently in pediatric patients with spondylolysis. However, the kinematics of pediatric lumbar spine with pars defects has not yet been well documented.

METHODS

Radiographs of 70 pediatric patients (57 boys and 13 girls) with low back pain were examined. The control group (without spondylolysis) consisted of 22 patients (15 boys and 7 girls; mean age, 14.6 years; range, 10-18 years), and the lysis group (with spondylolysis at L5) consisted of 48 patients (42 boys and 6 girls; mean age, 14.5 years; range, 11-18 years). The lysis group was further divided into four subgroups according to the stage of defects and existence of slippage: Group 1 (early stage defect), Group 2 (progressive stage defect), Group 3 (terminal stage defect without slippage), and Group 4 (terminal stage defect with slippage of more than 5%; olisthesis). The instantaneous axis of rotation at L4-L5 and L5-S1 from the extended to the flexed position was measured on lateral dynamic radiograms taken in with the subject in the recumbent position. The relation between lumbar index and the site of instantaneous axis of rotation at L5-S1 also was analyzed.

RESULTS

The site of instantaneous axis of rotation at L5-S1 and L4-L5 in the control group was not located in the rotating cranial vertebra. In 1 of the 11 patients in the early-stage subgroup, the instantaneous axis of rotation at L5-S1 was found in the cranial vertebra. In 4 of the 11 patients in the progressive stage, 11 of the 16 patients in the terminal stage, and in 7 of the 10 patients in the olisthesis subgroup, the instantaneous axis of rotation was located in the cranial vertebra. Cranial deviation in the instantaneous axis of rotation was observed more frequently in the vertebra with severe deformity less than 80% of the lumbar index than in the vertebra with milder deformity.

CONCLUSIONS

The instantaneous axis of rotation deviated cranially as the stage of pars defects advanced, and as the wedge deformity increased. Kinematic alteration of the lumbar spine in pediatric patients with spondylolysis may affect chondrocytes of the endplate, perhaps contributing to the consequent spine deformities occurring secondarily to spondylolysis.

Slippage mechanism of pediatric spondylolysis: biomechanical study using immature calf spines

STUDY DESIGN

This study analyzed the skeletal-age-dependent strength of the lumbar growth plate to resist anterior shearing forces using the MTS system in the immature calf spine with pars defects.

OBJECTIVE

To clarify the pathomechanism of the skeletal-age-dependent incidence of slippage in pediatric patients with pars defects by comparing the strength of the lumbar growth plate among three skeletal age groups.

SUMMARY OF BACKGROUND DATA

Isthmic spondylolisthesis occurs and progresses more frequently during the growth period, whereas it is rare afterward. However, little evidence has been demonstrated to elucidate the etiology.

METHODS

For this study, 15 lumbar functional spine units were divided into three groups according to their skeletal ages. Five were from neonates (Group 1), five from calves approximately 2 months old (Group 2), and five from calves about 24 months old (Group 3). An anterior shearing force was applied to each specimen until failure, after bilateral pars defects were created. Failure load (newtons) and displacement at failure (millimeters) were calculated from the load-displacement curve. The site of failure was confirmed by plain radiograph.

RESULTS

All 15 functional spine units failed at the growth plate. The failure load was 242.79 +/- 46.05 N in Group 1, 986.40 +/- 124.16 N in Group 2, and 2024.54 +/- 245.53 N in Group 3. Statistically significant differences were found among the three groups (P < 0.05). The displacement at failure was 7.52 +/- 1.84 mm in Group 1, 11.10 +/- 2.30 mm in Group 2, and 8.15 +/- 2.66 mm in Group 3. There were no significant differences among the groups.

CONCLUSIONS

The results indicate that the strength of the growth plate, the weakest link in this model, against anterior shearing forces depends on the skeletal maturity, and that the biomechanical weakness of the growth plate plays an important role in the slippage mechanism.

The pathomechanism of spondylolytic spondylolisthesis in immature primate lumbar spines in vitro and finite element assessments

STUDY DESIGN

Immature Chacma baboon (Papio ursinus) spine specimens were used to determine load-displacement behavior as related to disc injury. This was accomplished through the application of A-P shear force until failure of FSUs with pars defects. Several finite element models (FEMs) of the FSU were developed to study the mechanism of slippage in immature baboon lumbar spines.

OBJECTIVES

The purpose was to show that spondylolisthesis (olisthesis) always occurs through the growth plate using a model similar to immature human lumbar spines. Using FEMs, the roles of facet orientation, pars interarticularis thickness, and a weak growth-plate in producing slippage were examined.

SUMMARY OF BACKGROUND DATA

Progression from spondylolysis (lysis) to olisthesis occurs, most often, during the adolescent growth spurt. The biomechanical literature dealing with the slippage mechanism in the immature lumbar spine does not provide a clear understanding and is sparse.

METHODS

Several groups of FSUs were subjected to A-P shear force until failure. The results provided displacement at failure as a function of disc injury and flexion-extension fatigue. A bilateral pars defect was created in each specimen prior to application of A-P shear force using an MTS machine. Failure sites were assessed radiographically and histologically. A nonlinear 3-D FEM of the intact L4-L5 was created from CT scans. The model was modified to predict the effects of a pars fracture, a thin pars, a weak growth plate, and facet orientation on the shear load through the growth plate and stresses in the pars.

RESULTS

Experimentally, failures always occurred through the growth-plate in the disc intact and disc-incised groups. In the intact FEM, the growth plate carried21% of the applied A-P shear force. The load increased when the facets were more sagittally oriented. The effect of thin pars and/or weaker growth plate was an increase in stresses in the pars. Changes in the load through the growth plate were minimal.

CONCLUSIONS

The weakest link in immature baboon lumbar functional spinal units (FSUs) with lysis during an A-P shear load was the growth plate, between the cartilaginous and osseous end plates. Surgeons may assess this lesion on MRI views, thereby predicting the possible development and preventing progression of olisthesis. Finite element model results predict that more sagittally orientated facets and/or a pars fracture are prerequisites for olisthesis to occur.

[Biomechanics in the pathogenesis of spondylosis and spondylolisthesis]

The etiology and predisposing factors of spondylolysis and spondylolisthesis, which are summarized in the first part of this article, have received considerable attention, but there biomechanics is little published. The goal of this article is to show a biomechanical model for the development of spondylolysis and spondylolisthesis. With mechanical equations it has been established, the pars interarticularis and the ligaments resist together the tensile and shear force, the bending moment if the pars interarticularis is uncracked. If the tensile stress in the pars interarticularis reaches its strength, crack occurs and the spondylolysis is developed. The cracked pars interarticularis is no longer capable of sustaining tension, the tensile force is transferred to the ligament. When the compressive strain of the pars interarticularis reaches its strain limit, the spondylolisthesis does not develop, because the vertebra can not slip with the unbroken ligaments. If the loading on the pars interarticularis would be decreasing, the cracks close and the pars interarticularis can ossify. If the tensile stress in the ligament reaches its strength and the ligament breaks, the pars interarticularis cracks through, the vertebra slips and the spondylolisthesis develops. In the last part of the article the methods of the conservative and operative treating are summarized.

Global spinal motion in subjects with lumbar spondylolysis and spondylolisthesis: does the grade or type of slip affect global spinal motion?

STUDY DESIGN

This was a prospective pilot study to investigate the global motion characteristics of the spondylolysis and spondylolisthesis populations.

OBJECTIVES

The aim of this study is to determine the influence of a spondylolisthesis or a spondylolysis on global spinal motion and to establish whether this is dependent on the cause of the slip or the degree/grade of the slip.

SUMMARY OF BACKGROUND DATA

The condition of spondylolisthesis has been extensively discussed in the literature with respect to its etiology and management. However, the mechanics and movement of the spine in relation to pathology and the effect of this condition on function have received scant attention.

METHODS

The motion of the lumbar spine was investigated in 31 patients (19 men, 12 women, mean age 47.7 +/- 17.8 years) who were diagnosed as having either a lumbar spondylolysis or a spondylolisthesis. These patients were compared with a preexisting database of 203 normal subjects (100 men, 103 women, mean age 39.8 +/- 13.4 years). Patients were graded according to the type of spondylolisthesis or spondylolysis they had, and the extent of slip was rated using Meyerding's classification (1932) and measured directly using methods of Boxall et al (1979) and Wiltse et al (1983).

RESULTS

Direct measurements of the extent of slip using Boxall et al (1979) and Wiltse et al (1983) methods were found to have no significant correlation with the resultant range of motion (ROM) or the speed of movement. This study suggests that motion parameters are influenced by the grade of slip in patients with spondylolisthesis, and the type of spondylolisthesis i.e., whether isthmic or degenerative. In the A-P flexion-extension plane, the results indicate that subjects with a defect only, i.e., a spondylolysis, and thus no slip present with a spinal hypermobility (P < 0.01). Subjects with an isthmic slip tend to be either slightly hypermobile or within the anticipated range of motion, whereas those subjects with a degenerative slip tend to be hypomobile (P < 0.05). Movements into lateral flexion were restricted in both the isthmic and degenerative spondylolisthesis patients, whereas rotation was only influenced by the level at which the defect occurred. In terms of degree of displacement, in higher grades of displacement, there was a trend towards hypermobility.

CONCLUSIONS

The findings of this study suggest that the grade and type of spondylolisthesis do influence global motion parameters. This information may be useful in the clinical assessment of this patient group.

Spondylolysis: a critical review

AIM

To provide an understanding of the current concepts in the natural history, pathophysiology, diagnosis, and treatment of spondylolysis based on the available medical literature.

METHODS

Articles were selected for review by the following methods: (a) MEDLINE searches with review of abstracts to select relevant articles; (b) review of multiple textbooks considered likely to contain information on spondylolysis; (c) review of references in articles identified by (a) and (b). Over 125 articles were ultimately reviewed fully. Publications were selected for inclusion in this article on the basis of perceived scientific and historical merit, particularly as thought to be relevant to achieving the stated purpose of this review. As no controlled clinical trials were identified, this could not be used as an inclusion criterion.

CONCLUSIONS

Isthmic spondylolysis is considered to represent a fatigue fracture of the pars interarticularis of the neural arch. There is a relatively high incidence of radiographically identified spondylolysis in the general population, but the vast majority of these lesions probably occur without associated symptoms. Symptomatic pars lesions appear to be particularly a clinical problem in adolescents, especially adolescent athletes. The optimal diagnostic and treatment algorithms are not well identified in the current literature. Multiple imaging studies may have a role in the diagnosis of a pars lesion, and treatment seems likely to require at least relative rest and physical rehabilitation with consideration of bracing or, rarely, surgical intervention depending on the clinical context.

Back injuries and the fast bowler in cricket

Here, I review research that has investigated the aetiology of injuries experienced by adolescent and adult fast bowlers. Mechanical factors play an important role in the aetiology of degenerative processes and injuries to the lumbar spine. This is particularly so in fast bowling, where a player must absorb vertical and horizontal components of the ground reaction force that are approximately five and two times body weight at front-foot and rear-foot impact, respectively. Attenuated forces are transmitted to the spine through the lower limb, while additional forces at the lumbo-sacral junction are caused by trunk hyperextension, lateral flexion and twisting during the delivery stride. Fast bowlers are classified as side-on, front-on or mixed. The mixed action is categorized by the lower body configuration of the front-on action and the upper body configuration of the side-on technique. This upper body configuration is produced by counter-rotation away from the batsman in the transverse plane about the longitudinal axis of the body of a line through the two shoulders. Counter-rotations of 12-40 degrees during a delivery stride have predicted an increased incidence of lumbar spondylolysis, disc abnormality and muscle injury in fast bowlers. During the delivery stride, the mixed bowling action also shows: more lateral flexion and hyperextension of the lumbar spine at front-foot impact, and a greater range of motion of the trunk over the delivery stride when compared with the side-on and front-on techniques. The pars interarticularis of each vertebra is vulnerable to injury if repetitive flexion, rotation and hyperextension are present in the activity. Fast bowlers should reduce shoulder counter-rotation during the delivery stride to reduce the incidence of back injuries. When a player is required to bowl for extended periods irrespective of technique, overuse is also related to an increased incidence of back injuries and must be avoided.

Spondylolysis

Spondylolysis is a relatively common incidental radiographic finding that, most frequently, is asymptomatic. Isthmic spondylolysis with a lesion in the pars interarticularis may be a significant cause of pain in a given individual, particularly in adolescent athletes involved in sports with repetitive spinal motions. The pars lesion likely represents a stress fracture of the bone caused by the cumulative effect of repetitive stress imposed by physical activity. The lesion frequently presents as focal LBP and can often be identified on plain radiography. Advanced imaging with SPECT, CT, and MR imaging may be needed to ascertain the acuity of the lesion, assist in identifying a particular pars lesion as potentially symptomatic, and to exclude other spinal pathology that may be present. Conservative treatment is usually successful in controlling symptoms and restoring function; only a small percentage of patients require surgical intervention for pain or progressive spondylolisthesis. Based on current evidence, treatment requires activity restriction (i.e., temporary discontinuation of the aggravating sport or activity) and may require bracing to achieve treatment goals, although healing, pain relief or both may occur without brace application. A full understanding of spinal biomechanics and pathophysiology, the role of diagnostic imaging, and treatment options is needed to care for these patients.

Biomechanical functions of the iliolumbar ligament in L5 spondylolysis

Abiomechanical study of the functions of the iliolumbar ligament in L5 spondylolysis was performed. Five fresh cadaveric specimens were used. The bilateral ilia and sacrum were fixed. Four kinds of pure moments (10 Nm) were applied to the specimens at the top (L4) vertebra: flexion, extension, and right and left axial rotations. The three-dimensional position of the L5 vertebra was measured after serial transections in: (1) the intact condition; (2) bilateral pars interarticulares of L5 transected; (3) anterior bands of the iliolumbar ligaments transected; and (4) posterior bands of the iliolumbar ligaments transected. In L5 spondylolysis, flexion and axial rotation of L5 on S1 are significantly regulated by the anterior and posterior bands of the iliolumbar ligaments (especially by the posterior bands of the ligaments). The integrity of the ligament may determine the stability of the lumbosacral junction and the amount of forward slipping of the L5 vertebra.