The effect of polytrauma in persons with traumatic spine injury. A prospective database of spine fractures

STUDY DESIGN

A mixed cross-sectional survey and cohort study using a prospectively gathered database of persons with traumatic spine injury.

OBJECTIVES

To identify demographic and injury mechanism factors that predict greater injury severity, and to determine the effect of injury severity on outcomes in traumatic spine fracture.

SUMMARY OF BACKGROUND DATA

Traumatic spine fracture outcome studies have focused on defining type and level of vertebral fracture without considering the severity of associated injuries. In the trauma population, greater injury severity has been shown to be related to worse outcome. No studies have been reported on the effect of injury severity on outcome in the traumatic spine fracture population.

METHODS

Prospectively collected data on 830 persons with traumatic spine injury who were admitted to a trauma hospital were reviewed. Patient demographics; injury mechanism; hospital events; and disability, employment, and pain status at discharge, 1 year, and 2 years after injury were recorded. Associations between these factors and trauma severity (Injury Severity Score) were explored using Pearson's correlation and analysis of variance.

RESULTS

Trauma was more severe in patients who had been married previously, who were involved in a motor vehicle accident, were ejected from the vehicle, had loss of consciousness, had higher-level and multiple complicated vertebral fractures, or had neurologic deficit. Those more severely injured had longer lengths of stay, more surgery, more complications, higher mortality, more disability, and less return to work.

CONCLUSIONS

Persons with traumatic spine injury and polytrauma have poorer short- and long-term outcomes. This high-risk group may require aggressive interventions, more hospital resources, and close follow-up observation after discharge from hospital to optimize outcome.

Localized damage in vertebral bone is most detrimental in regions of high strain energy density

It was hypothesized that damage to bone tissue would be most detrimental to the structural integrity of the vertebral body if it occurred in regions with high strain energy density, and not necessarily in regions of high or low trabecular bone apparent density, or in a particular anatomic location. The reduction in stiffness due to localized damage was computed in 16 finite element models of 10-mm-thick human vertebral sections. Statistical analyses were performed to determine which characteristic at the damage location--strain energy density, apparent density, or anatomic location--best predicted the corresponding stiffness reduction. There was a strong positive correlation between regional strain energy density and structural stiffness reduction in all 16 vertebral sections for damage in the trabecular centrum (p < 0.05, r2 = 0.43-0.93). By contrast, regional apparent density showed a significant negative correlation to stiffness reduction in only four of the sixteen bones (p < 0.05, r2 = 0.47-0.58). While damage in different anatomic locations did lead to different reductions in stiffness (p < 0.0001, ANOVA), no single location was consistently the most critical location for damage. Thus, knowledge of the characteristics of bone that determine strain energy density distributions can provide an understanding of how damage reduces whole bone mechanical properties. A patient-specific finite element model displaying a map of strain energy density can help optimize surgical planning and reinforcement of bone in individuals with high fracture risk.

Differential biomechanical effects of injury and wiring at C1-C2

STUDY DESIGN

An in vitro study compared the biomechanics of the upper cervical spine among three groups of cadaveric specimens, each with a different source of instability: transverse-alar-apical ligament disruptions, odontoid fractures, or odontoidectomies. The responses of the three groups were again compared after a uniform posterior cable and graft fixation was applied to the specimens.

OBJECTIVES

To quantify and compare the effects of different injuries on atlantoaxial stability and to determine whether a single fixation technique effectively treats each injury.

SUMMARY OF BACKGROUND DATA

Previous biomechanical studies of atlantoaxial instability have been focused on mechanisms of injury or on comparison among fixation types.

METHODS

Cables and pulleys applied torques to human cadaveric C0-C6 specimens quasistatically while an optical system tracked three-dimensional angular and translational motion at C0-C1 and C1-C2. Specimens were tested immediately after injury, after posterior cable and graft fixation, and after 6000 cycles of fatigue.

RESULTS

Odontoidectomies increased C1-C2 angular and translational range of motion significantly more than odontoid fractures or ligament disruptions, especially during flexion-extension. Odontoid fractures produced a slightly larger increase in C1-C2 angular range of motion than ligament disruptions but a smaller increase in C0-C1 range of motion. The different injuries affected the lax zone and the position of C1-C2 axis of rotation differently. Restabilization by posterior cable and graft reduced motion only moderately for each injury type. All three fixated injuries were susceptible to loosening from fatigue.

CONCLUSION

The three different injuries produce different spinal biomechanical responses. To best promote fusion, posterior cable and graft fixation should be used with an adjunctive stabilizing technique to treat all three injuries.

[Correction of posttraumatic deformities. Principles and methods]

The reason for inadequate results after the treatment of spinal lesions may be due to the misinterpretation of the type of lesion thus leading to incorrect therapy. Frequently the bio-functional construction principles of the spine are ignored and biomechanically based reconstruction of the spine is not done. Unsuitable approaches and fusion techniques may result in insufficient stabilisation with predictable failure. In both the first surgery and the salvage procedure, the principles of the load-sharing system as well as the posterior tension band principle must be respected. These principles and the surgery techniques are demonstrated in individual examples. Special attention is drawn to the impact of segmental deformities on the general statics of the spine. Frequently, residual deformities with the typical clinical picture lead to decompensation and the reduction of efficiency only after ten to fifteen years.

[Reliability of functional x-ray analysis of cervical vertebrae flexion and extension]

Functional radiographic analysis of the cervical spine in flexion and extension position is increasingly used as screening method for the diagnosis of segmental functional disorders. The objective of this study was to prove Penning's evaluation method for the metrical recording of segmental angles in the sagittal plane for selectivity, reliability and usability. Passive functional radiographs of the cervical spine in flexion and extension were taken of 20 patients with painful limitation of mobility of the cervical spine and 20 subjects, similar in sex and age, without complaints. The radiographs were duplicated. Five physicians measured the angles of segmental mobility in a blind study. Statistical analysis was conducted using the t-test and calculating the correlation coefficient "r". The results of the study prove that the evaluation method by Penning shows a usable and, for segments C3/C4 to C6/C7, significant selectivity. The selectivity of p < or = 0.05 and p < or = 0.01 is sufficient to distinguish patients from healthy subjects. The correlation between the five reviewers showed good to very good results (0.6 < r < or = 0.8; r > 0.8). The measured values, however, have to be considered, in connection with the appropriate clinical symptoms, as still "normal" or "functionally disordered" in the context of segmental hypo-resp. hypermobility.

Cervical spine evaluation in obtunded or comatose pediatric trauma patients: A pilot study

A uniformly accepted protocol for evaluation and clearance of the cervical spine of pediatric trauma patients with altered mental status does not currently exist. We sought to detect cervical spine injuries in this group with minimal risk. Patients were evaluated with standard three-view cervical spine radiographs and CT when necessary. Those patients without radiographic abnormality and altered mental status underwent flexion-extension of the cervical spine using fluoroscopy with somatosensory evoked potential (SSEP) monitoring. Those with abnormal movement by fluoroscopy or changes in SSEP underwent MRI. Fifteen patients were evaluated with this protocol. Two patients had movement on flexion-extension of the cervical spine and 5 had SSEP changes. Three patients had an MRI with only 1 showing injury. Five patients had residual hemiparesis. Evaluation of the cervical spine in obtunded or comatose pediatric trauma patients can be done safely with flexion-extension under fluoroscopy and SSEP monitoring. Further prospective studies are required to determine the efficacy of SSEP monitoring for cervical spine clearance in this select population.

[Clinical studies in health workers employed in the manual lifting of patients: methods for the examination of spinal lesions]

To enable different research groups to make a standardized collection of clinical data on alterations of the lumbar region of the spine, protocols were used for the collection and classification of data that were proposed and thoroughly validated by the authors. The protocols include a clinical/functional examination of the spine, checking for positive anamnestic threshold, for pain on pressure/palpation of the spiny apophyses and paravertebral muscles, for painful movements, in order to classify 1st, 2nd and 3rd grade functional spondylarthropathy (for different regions of the spine). An ad hoc questionnaire was also prepared for the quantitative and qualitative study of true acute low back pain and the ingravescent low back pain controlled at the onset pharmacologically. The results of this questionnaire make it possible to calculate the incidence of acute low back pain (true and pharmacologically controlled).

Cervical collar-induced changes in intracranial pressure

Placement of a protective cervical collar is common in cases of acute head trauma. However, the effect of this collar on intracranial pressure is uncertain. This prospective study examined the change in measured cerebrospinal fluid pressure (CSFP) after the application of a rigid Philadelphia collar in 20 adult patients undergoing lumbar puncture. CSFP averaged 176.8 mm H2O initially and increased to an average of 201.5 mm H2O after collar placement (range 0 to 120). Although this difference of 24.8 mm H2O is statistically significant (P = .001), it is uncertain if this would be clinically important. Nonetheless, this small increment in pressure could be significant in patients who already have an elevated intracranial pressure.

Facet coverage in children on flexion lateral cervical radiographs

STUDY DESIGN

This radiographic study was designed to attempt to develop standards of facet coverage (overlap) on lateral cervical radiographs during voluntary flexion.

OBJECTIVE

To produce normative standards for minimum facet coverage in children.

SUMMARY OF BACKGROUND DATA

Previous studies on normative standards of facet coverage have been performed only in adults.

METHODS

Thirty-six children with minor trauma had lateral flexion-extension radiographs. A standard filming sequence was used in all. Facet joint overlap at each level was divided by the anteroposterior diameter of the upper adjacent cervical body at each level.

RESULTS

On linear regression analysis, these ratios did not vary significantly with age at C2-C3 through C6-C7. Means and standard deviations were determined for C2-C7.

CONCLUSIONS

These ratios may prove useful in evaluation of children with possible ligamentous injury.

The clinical relevance of biomechanics

Most neurologists are familiar with biomechanics but may be unsure of the relevance of this field to their practice. Actually those involved in musculoskeletal problems are undoubtedly using biomechanical principles. This article is limited to the spine, but the basic principles of biomechanics are applicable to other parts of the body. In this article, we describe the spine and trunk as a biomechanical organ, the biomechanical principles behind back injuries and their importance, the role of biomechanical issues in pain, the utility of clinical tests based on biomechanical principles, the effects of aging, and the future directions in spine biomechanical research.

Risk factors for vertebral fractures in renal osteodystrophy

We determined the prevalence of vertebral fractures in hemodialysis (HD) patients, investigated whether low bone mineral density (BMD) is predictive of vertebral fracture, and evaluated the effect of serum intact parathyroid hormone (iPTH) and alkaline phosphatase (ALP) levels on vertebral fracture. One hundred eighty-seven male HD patients were assessed for vertebral fractures, and lumbar-spine and total-body BMD were measured by dual-energy x-ray absorptiometory. Thirty-nine patients (20.9%) had vertebral fractures. Each standard deviation (SD) decrease in lumbar-spine BMD increased the age-adjusted odds ratio of vertebral fracture 2.0 times (95% confidence interval [CI], 1.4 to 2.0) and 1.6 times (95% CI, 1.1 to 1.6) for total-body BMD. The area under the receiver operating characteristic curve for lumbar-spine BMD was significantly greater than that for total-body BMD (P < 0.05). Patients with serum iPTH levels in the lowest tertile had a 2.4-fold greater risk for vertebral fracture than those in the middle tertile and a 1.6-fold greater risk than those in the highest tertile (P < 0.05). When the two criteria of lowest tertile of serum iPTH level and highest tertile of serum ALP level were combined, the prevalence of vertebral fractures was the greatest. Similarly, when the lowest tertile of serum iPTH level and lowest tertile of serum ALP level were combined, the prevalence was the second greatest among the combined groups according to tertiles of serum iPTH and ALP levels. We conclude that low lumbar-spine BMD might be a sensitive predictor of vertebral fracture in HD patients, and patients with relatively low iPTH levels would have a greater risk for vertebral fracture than those with hyperparathyroidism.

Lumbosacral instrumented fusion: analysis of 124 consecutive cases

One hundred twenty-four cases of lumbosacral fusion receiving transpedicular screw fixation were divided into two groups and reviewed retrospectively. The conditions treated include spondylolisthesis, scoliosis, tumor, trauma, and degenerative disc disease. There were 83 males and 41 females in this consecutive series averaging a 45.2-month follow-up. The primary or first-time arthrodesis rate was 91.9%. A learning curve effect as it relates to operative time but not pedicular screw placement was shown. Instrumentation-related and general medical and surgical complications were low. Infection rates were also low; superficial 2.4%, deep 1.6%. Nonunion or delayed union was salvaged in 10 cases, improving the overall fusion rate to 97.6%. The results of this study support the use of lumbosacral transpedicular screw fixation in select spinal conditions.

Risk of early closed reduction in cervical spine subluxation injuries

OBJECT

The authors retrospectively reviewed 121 patients with traumatic cervical spine injuries to determine the risk of neurological deterioration following early closed reduction.

METHODS

After excluding minor fractures and injuries without subluxation, the medical records and imaging studies (computerized tomography and magnetic resonance [MR] images) of 82 patients with bilateral and unilateral locked facet dislocations, burst fractures, extension injuries, or miscellaneous cervical fractures with subluxation were reviewed. Disc injury was defined on MR imaging as the presence of herniation or disruption: a herniation was described as deforming the thecal sac or nerve roots, and a disruption was defined as a disc with high T2-weighted signal characteristics in a widened disc space. Fifty-eight percent of patients presented with complete or incomplete spinal cord injuries. Thirteen percent of patients presented with a cervical radiculopathy, 22% were intact, and 9% had only transient neurological deficits in the field. Early, rapid closed reduction, using serial plain radiographs or fluoroscopy and Gardner-Wells craniocervical traction, was achieved in 97.6% of patients. In two patients (2.4%) closed reduction failed and they underwent emergency open surgical reduction. The average time to achieve closed reduction was 2.1+/-0.24 hours (standard error of the mean). The incidence of disc herniation and disruption in the 80 patients who underwent postreduction MR imaging was 22% and 24%, respectively. However, the presence of disc herniation or disruption did not affect the degree of neurological recovery, as measured by American Spinal Injury Association motor score and the Frankel scale following early closed reduction. Only one (1.3%) of 80 patients deteriorated, but that occurred more than 6 hours following closed reduction.

CONCLUSIONS

Although disc herniation and disruption can occur following all types of traumatic cervical fracture subluxations, the incidence of neurological deterioration following closed reduction in these patients is rare. The authors recommend early closed reduction in patients presenting with significant motor deficits without prior MR imaging.

[Changes in the somatosensory evoked potentials of patients with complicated spinal trauma after an omentomyelopexy operation]

The purpose of the study was to record somatosensory evoked potentials (SSEP) to objectify the results omentomyelopexy in late spinal cord injury. SSEP were recorded in 25 patients in leads of three levels of the somatosensory tract (from the popliteal fossa, from the lumbar enlargement of the spinal cord, and from the surface of the skull in the region of projection of leg presentation in cerebral hemispherical cortex) before and after surgery. The study indicated that there were no pre- or postoperative records of cortical evoked potentials. At the same time there was improvement in the magnitude of SSEP at the level of the lumbar enlargement (36%). In 4 (16%) and 5 (20%) cases of them SSEP changes were clear and unclear, respectively. The assessment of SSEP changes requires consideration of cases with unclear SSEP. Comparison of the results with clinical findings shows a correlation mainly with urological and urodynamic evidence. Thus, there are minor positive changes in the magnitude of SSEP after omentomyelopexy in the lumbar enlargement lead with unclearly pronounced evoked potentials.

Cervical spine models for biomechanical research

Biomechanical models have been used for the understanding of the basic normal function and dysfunction of the cervical spine and for testing implants and devices. Biomechanical models can be broadly categorized into four groups: 1) Physical models, made of nonanatomic material (e.g., plastic blocks), are often used for the testing of spinal instrumentation when only the device is to be evaluated. 2) In vitro models consisting of a cadaveric spine specimen are useful in providing basic understanding of the functioning of the spine. Human specimens are more suitable for these models than are animal specimens whenever anatomy, size (for instrumentation), and kinematics are important. Animal specimens are less costly, easier to obtain, and often have less variability but should be used with care because of the absence of anatomic fidelity with the human. 3) In vivo animal models provide the means to model living phenomena, such as fusion, development of disc degeneration, instability, and adaptive responses in segments adjacent to spinal instrumentation. Choosing the appropriate animal is important. The appropriate animal should have spinal loading, kinematics, kinetics, vertebral size, and healing-fusion rates as similar to those in humans as possible. For better interpretation of in vivo animal experimental results, in vitro biomechanical study using the same animal cadaveric specimen is useful but has not been used routinely. 4) Computer models are developed from mathematical equations that incorporate geometry and physical characteristics of the human spine and may be advantageously used for problems that are difficult to model by other means. Examples are the changes in disc and vertebral stresses in response to graded transection of facet joints and the study of changes in endplate loading caused by disc degeneration. Because these models are purely mathematical, their validation is essential. Validation is best achieved by first incorporating high-quality geometry and physical characteristics of the human spine and then comparing the model predictions with experimental observations. Sometimes an enthusiastic researcher may use a computer model beyond its validation boundary, making the model's predictions unreliable. In general, it is important to remember that a biomechanical model, similar to any other model, represents only a certain aspect of the real living human being. The aspect chosen for representation should be selected with great care. The model should be designed to answer specifically the question asked. Its predictions are valid only within the boundaries of assumptions and limitations that it incorporates.

Out-of-hospital cervical spine clearance: agreement between emergency medical technicians and emergency physicians

OBJECTIVE

Determine the level of agreement between emergency medical technicians (EMTs) and emergency physicians (EPs) when applying an existing emergency medical services/fire department protocol for out-of-hospital clinical cervical spine injury (CSI) clearance in blunt trauma patients.

METHODS

Prospective observational study of consecutive blunt trauma patients transported by emergency medical services/fire department during a 3-month study period. The setting was an urban Level I trauma center. Measurement of interrater agreement (kappa) was determined.

RESULTS

Mean age of the 190 patients was 34+/-19 years (range, 6 -98 years). Fifty-nine percent of the patients were male. One hundred forty-six patients (77%) were immobilized by EMTs; 17 of these patients were clinically cleared by EPs. Forty-four patients (23%) were clinically cleared by EMTs and presented without CSI precautions; of these, 61% (27 of 44) were immobilized by EPs and 57% (25 of 44) had cervical spine radiographs obtained. Overall, 141 patients (74%) required radiographic clearance. CSI were detected in five patients (2.6%); all five were immobilized in the out-of-hospital setting. Overall disagreement between EMTs and EPs regarding out-of-hospital CSI clearance occurred in 44 patients (23%) (kappa=0.29; 95% confidence interval, 0.15-0.43; p < 0.01).

CONCLUSION

Significant disagreement in clinical CSI clearance exists between EMTs and EPs. Further research and education is recommended before widespread implementation of this practice.

[The assessment of the dynamics of somatosensory evoked potentials in the surgical and conservative treatment of patients following spinal and spinal cord trauma]

Somatosensory evoked potentials at the cortical and spinal levels were dynamically studied in patients with vertebral column and spinal cord injuries before and after radical reparative surgery. The study showed that quantitative determination of the time course of changes occurring was highly effective in neurological disorders. Most significant were changes in the latent periods and amplitude of the peaks N11, N13, N20, P23 in the activation of n. medianus and N21, N28, P37, N45 in the bilateral stimulation of n. tibialis posterior. There was a correlation of neurophysiological and clinical manifestations in 50-60% of cases. Thus, the neurophysiological studies quantitatively verify the efficiency of surgical treatment for vertebral column and spinal cord injuries.

Effect of age and loading rate on human cervical spine injury threshold

STUDY DESIGN

Statistical analysis of human cadaver cervical spine compression experiments.

OBJECTIVES

To quantify the cervical spine compressive injury threshold as a function of the person's age, gender, and external loading rate.

SUMMARY OF BACKGROUND DATA

Results of epidemiologic studies have indicated that most survivors of cervical spinal cord injury have spinal column fractures and dislocations that result from a compression or compression-flexion force vector. Cervical spinal column injury thresholds are dependent on many factors. Delineation of the injury thresholds according to age, gender, and loading rate is necessary to improve clinical assessments and prevention strategies.

METHODS

Twenty-five human cadaver head-neck compression tests were included in the analysis. Two statistical models were used to quantify the effects of age, gender, and loading rate on the force required to induce failure in the cervical spine. A multiple linear regression model provided a direct equation that quantified the effects of the variables, and a proportional hazards model was used to quantify probability of injury with each factor.

RESULTS

The regression model had a correlation coefficient of 0.87. There was an interactive effect between age and loading rate: Increasing age reduced the effect of loading rate and at approximately 82 years, loading rate had no effect. Men were consistently 600 N stronger than women. The 50% probability of failure for a 50-year-old man at a 4.5-m/sec loading rate was approximately 3.9 kN. Differences in probability curves followed the same trends as seen in the regression model.

CONCLUSIONS

The effects of age on cervical spine injury threshold are coupled with the rate of loading experienced through the external force vector that causes the trauma. Assessment of injury mechanisms and thresholds should be based on the person's age, gender, and loading rate to determine treatment and prevent injuries.

[Possibilities for static and dynamic stabilization of the spine in lesions of the anterior and posterior ligament complex]

Defects of the dorsal and ventral ligament complexes of the lumbar spine results to an instability of the functional spinal unit. For the prognosis of secondary instability due to disko-ligamentous injuries the functional insufficiency of the lasting scars is a larger problem than the primary loss of osseous stability with fast healing tendency. The main goal of the present biomechanical study in vitro was to demonstrate the different grades of instability in the correlation to progressive disko-ligamentous defects as well as stabilisation through dynamic and static procedures. With a transpedicular screw-ringband-system the segmental function was preserved and instability was abolished. After rigid instrumentation with a fixateur intern remained a residual range of motion due to which can result refuse to bending moments without spondylodesis in an implant failure.

Helmet and shoulder pad removal from a player with suspected cervical spine injury. A cadaveric model

STUDY DESIGN

Video fluoroscopy was used to evaluate the motion in an unstable spine during helmet and shoulder pad removal.

OBJECTIVE

To observe the amount of motion that occurs during the removal of helmet and shoulder pads in an injured spine.

SUMMARY OF BACKGROUND DATA

Removal of shoulder pads and helmet from a football player with suspected cervical spine injury can be particularly hazardous. How much flexion occurs at the unstable level during removal of equipment is unknown.

METHODS

Six fresh cadavers were used in the study. In three, an unstable C1-C2 segment was created by transoral osteotomy of the base of C2. In the remaining three, instability was created at C5-C6 by a posterior release. Under fluoroscopic recording, the helmets were removed by first removing the chin strap, face mask, and ear pieces. With the neck stabilized, the helmet was carefully removed. The shoulder pads were carefully removed, with the head stabilized. Angulation, distraction, and space available for the cord were measured at C1-C2. Translation, angulation, distraction, and change in disc height were measured in the specimens with unstable C5-C6.

RESULTS

In cadavers with C1-C2 instability, the mean change in angulation was 5.47 degrees, and space available for the cord was 3.91 mm. Shoulder pads were removed while the head was stabilized. The mean change in angulation at C1-C2 was less during removal of shoulder pads than during helmet removal at 2.9 degrees. Space available for the cord was 2.64 mm. Distraction was also greater during helmet removal (2.98 mm) than during shoulder pad removal (1.76 mm). In the unstable spine, the change in displacement in translation was greater during shoulder pad removal (3.87 mm), than during helmet removal (0.41 mm). Disc height change was similar. Distraction of the spinous processes was greater during helmet removal (3.68 mm) than during shoulder pad removal (1.37 mm). Angulation was similar in both maneuvers.

CONCLUSIONS

Helmet and shoulder pad removal in the unstable cervical spine is a complex maneuver. In the unstable C1-C2 segment, helmet removal causes more angulation in flexion, more distraction, and more narrowing of the space available for the cord. In the lower cervical spine (C5-C6), helmet removal causes flexion of 9.32 degrees, and during shoulder pad removal the neck extends 8.95 degrees, a total of approximately 18 degrees. Disc height changes from 1.24 mm of distraction to 1.06 mm of compression during helmet removal and shoulder pad removal for a total 2.3-mm change. Translation, which correlates with the change in the space available for the cord, is greater at C5-C6 during shoulder pad removal. Because most of the cadavers had C5 anteriorly displaced on C6 to begin with, the extension force during shoulder pad removal caused a 3.87-mm change in reduction of C5 on C6. Because of the motion observed in the unstable spine, helmet and shoulder pad removal should be performed in a carefully monitored setting. They should be removed together by at least three, preferably four, trained people.

An animal model for the neuromodulation of neurogenic bladder dysfunction

OBJECTIVE

To develop an animal model to examine the pathophysiology by which S3 sacral root electrostimulation alters the micturition reflex in patients with bladder hyper-reflexia.

MATERIALS AND METHODS

Chronic sacral nerve root electrostimulation was applied to spinally transected rats; 21 animals were divided into four groups. The spinal cord was completely transected at the T10-11 level and stainless-steel electrodes implanted into the sacral foramen in 17 animals; these animals were subsequently divided into two groups (1 and 2). Six rats in group 1 underwent sacral root elctrostimulation for 2 h/day and five in group 2 for 6 h/day, for 21 days. The sham group (group 3, six rats) received no stimulation and four rats were used as healthy controls (group 4). Voiding frequency was recorded and each animal was evaluated cystometrically at the end of the stimulation period. The results were compared with the sham and control groups.

RESULTS

Spinal cord transection resulted in bladder areflexia and complete urinary retention; 7-9 days after the injury, the bladder recovered its activity. Twenty-one days after transection all animals had evidence of uninhibited bladder contractions. The mean (SD) hourly frequency of urination was 0.66 (0.18) in healthy controls, 0.83 (0.21) in group 1, 0.87 (0.34) in group 2 and 1.1 (0.31) in group 3. There was a significant decrease in eh cystometric signs of bladder hyper-reflexia in groups 1 and 2 when compared with group 3.

CONCLUSIONS

This work reports and initial study showing that chronic electrostimulation of sacral nerve roots can reduce the signs of bladder hyper-reflexia in the spinally injured rat. To our knowledge, this is the first report describing the rat as an animal model to determine the effects of chronic electrostimulation on the micturition reflex.