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Biomedical subjects

A R Vaccaro

Publications and source records attributed to A R Vaccaro.

At least 19 recordsLinked to original sources
PubMed2001

Post-traumatic spinal deformity.

There are approximately 50,000 fractures to the bony spinal column each year in the United States. The vast majority of unstable spinal injuries are recognized early and managed appropriately. Rarely, the initial treatment may have been inadequate, or in less obvious injuries, less aggressive immobilization techniques may have been chosen. This along with continued exposure to physiologic stresses may lead to a gradual post-traumatic deformity that may further impede the functional as well as emotional status of these often already compromised patients. The management of post-traumatic deformity can be extremely challenging. A post-traumatic kyphotic deformity may occur in the cervical, thoracic, thoracolumbar, or lumbar spine, and once appropriate imaging studies are obtained, careful surgical considerations must be undertaken. Surgical intervention is considered if the kyphotic deformity is progressive over time or there is new onset or progression of a neurologic deficit. Surgical procedures include either a posterior or anterior only approach or any variation of a combined anterior or posterior procedure. In most cases a posterior only fusion is often insufficient for optimal correction and stabilization. Although the majority of patients developing a post-traumatic deformity usually occur after spinal column trauma initially treated nonoperatively, several miscellaneous causes of post-traumatic deformity may occur after surgery. These include nonunion, implant failure, Charcot spine, and technical error. The overall outcome after the surgical management of post-traumatic deformity has been satisfactory with better outcomes in the patients treated earlier as opposed to later. Operative complications include the increased risk of neurologic injury because of the draping of the neural elements over the anterior vertebral elements, any pre-existing spinal cord injury, and possible scarring with cord tethering. Trauma to the spinal cord and column is a devastating injury that may be fraught with many complications including post-traumatic deformity. Certainly, the best treatment is prevention with close follow-up and early intervention when needed. Once present, the treatment of post-traumatic deformity follows basic biomechanical principles consisting of re-establishing the integrity of the compromised spinal columns so that spinal stability can be restored.

Diagnostic Imaging↗
PubMed2001

Three-dimensional cartilage formation by bone marrow-derived cells seeded in polylactide/alginate amalgam.

Bone marrow-derived cells are considered as candidate cells for cartilage tissue engineering by virtue of their ability to undergo chondrogenesis in vitro when cultured in high density or when embedded within a three-dimensional matrix in the presence of growth factors. This study evaluated the potential of human bone marrow-derived cells for cartilage tissue engineering by examining their chondrogenic properties within a three-dimensional amalgam scaffold consisting of the biodegradable polymer, poly-L-lactic acid (PLA) alone, and with the polysaccharide gel, alginate. Cells were suspended either in alginate or medium and loaded into porous PLA blocks. Alginate was used to improve cell loading and retention within the construct, whereas the PLA polymeric scaffold provided appropriate mechanical support and stability to the composite culture. Cells seeded in the PLA/alginate amalgams and the plain PLA constructs were treated with different concentrations of recombinant human transforming growth factor-beta1 (TGF-beta 1) either continuously (10 ng/mL) or only for the initial 3 days of culture (50 ng/mL). Chondrogenesis was assessed at weekly intervals with cultures maintained for up to 3 weeks. Histological and immunohistochemical analysis of the TGF-beta 1-treated PLA/alginate amalgam and PLA constructs showed development of a cartilaginous phenotype from day 7 to day 21 as demonstrated by colocalization of Alcian blue staining with collagen type II and cartilage proteoglycan link protein. Expression of cartilage specific genes, including collagen types II and IX, and aggrecan, was detected in TGF-beta 1-treated cultures by reverse transcription-polymerase chain reaction analysis. The initiation and progression of chondrogenic differentiation within the polymeric macrostructure occurred with both continuous and the initial 3-day TGF-beta 1 treatment regimens, suggesting that key regulatory events of chondrogenesis take place during the early period of cell growth and proliferation. Scanning electron microscopy revealed abundant cells with a rounded morphology in the PLA/alginate amalgam. These findings suggest that the three-dimensional PLA/alginate amalgam is a potential candidate bioactive scaffold for cartilage tissue engineering applications.

Alginates↗
PubMed2001

Magnetic resonance imaging analysis of soft tissue disruption after flexion-distraction injuries of the subaxial cervical spine.

STUDY DESIGN: A retrospective study was performed with the use of magnetic resonance imaging to evaluate the type and degree of soft tissue disruption associated with flexion-distraction injuries of the subaxial spine. OBJECTIVE: To determine what soft tissue structures are injured in flexion-distraction injuries of the subaxial spine. SUMMARY OF BACKGROUND DATA: Prior published reports of unilateral and bilateral cervical facet dislocations have described the analyzed mechanisms and biomechanics of this injury subtype. No retrospective magnetic resonance imaging analysis of associated soft tissue disruption has been documented. METHODS: Magnetic resonance imaging evaluations of the cervical spine were obtained for all patients with a flexion-distraction injury, Stages 2 (unilateral facet dislocation) and 3 (bilateral facet dislocation), between September 1994 and May 1998. Two neuroradiologists, blinded to both clinical and radiographic findings, graded all the soft tissue structures for evidence of attenuation or disruption. The soft tissue structures were graded on a scale of 1 (intact), 2 (indeterminate), or 3 (disrupted). RESULTS: For this study, 48 patients satisfied the inclusion criteria: 25 with unilateral facet dislocation and 23 with bilateral facet dislocation. Disruption to the posterior musculature, interspinous ligament, supraspinous ligament, facet capsule, ligamentum flavum, and posterior and anterior longitudinal ligaments was found in a statistically significant number of patients with bilateral facet dislocation. For most of these structures, disruption was found to be statistically significant in patients with a unilateral facet dislocation, except for the posterior longitudinal ligament, in which significance was not consistently demonstrated using 95% confidence intervals in the binomial testing. In a comparison between unilateral and bilateral facet dislocations using a two-sided Fisher's exact test, it was found that disruption to the anterior and posterior longitudinal ligaments and the left facet capsule were statistically significant, with all three more prominent in bilateral facet dislocation. A multivariate analysis between unilateral and bilateral facet dislocations showed that disruption to the anterior longitudinal ligament was associated significantly with a bilateral facet dislocation. Disc disruption was found to be associated significantly with both injury types, but was more common in bilateral facet dislocation, although this difference in intergroup comparisons was not statistically significant. CONCLUSIONS: Unilateral and bilateral facet dislocations of the subaxial spine are associated with damage to numerous soft tissue structures that provide stability to the lower cervical spine. Damage to the posterior longitudinal ligament did not occur consistently in unilateral facet dislocations. Bilateral facet dislocations were associated significantly with disruption to the posterior and anterior longitudinal ligaments and left facet capsule, as compared with unilateral facet dislocations. Magnetic resonance imaging allows visualization of these disruptions.

Cervical Vertebrae↗
PubMed2001

In vitro genesis of subaxial cervical unilateral facet dislocations through sequential soft tissue ablation.

STUDY DESIGN: In vitro anatomic study investigating the degree of soft tissue disruption required to produce a subaxial cervical unilateral facet dislocation. OBJECTIVES: To develop an understanding of the relative contributions to stability of the subaxial cervical soft tissues and to define an anatomic threshold of injury necessary to produce a unilateral cervical facet dislocation. SUMMARY OF BACKGROUND DATA: The literature at this time is unclear regarding the precise pathomechanics of a cervical unilateral facet dislocation and the required threshold of soft tissue injury necessary for its genesis. Published clinical reports do not make any specific reference to these factors or are unclear in their objectivity. METHODS: Two adjacent vertebra at a time in 10 fresh-frozen subaxial cervical spine specimens (C2-C3 to C6-C7) were transfixed in the coronal plane with 3.5-mm Schanz screws. A steady unilateral vertical distraction force resulting in lateral cervical flexion was applied to these screws as the surrounding cervical soft tissue structures were sequentially ablated. Four experimental models were developed, varying the order of soft tissue disruption. RESULTS: The physiologic coupling of subaxial cervical unilateral distraction and rotation, because of the spatial orientation or inclination of the cervical facet joints, allowed the creation of a unilateral facet dislocation without an additional flexion moment. Disruption of the ipsilateral articular capsule, ligamentum flavum, and more than half of the anulus fibrosus was necessary for the genesis of a unilateral facet dislocation. Disruption of the supraspinous and interspinous ligaments was not necessary but appeared to facilitate or lessen the force required to dislocate a unilateral facet. Disruption of the anterior and posterior longitudinal ligaments and intertransverse ligaments was not necessary to create a unilateral facet dislocation. CONCLUSION: This anatomic study further supports the theory that discontinuity of the anterior and posterior longitudinal ligaments is not necessary for a unilateral facet dislocation to occur. The ipsilateral facet capsule, anulus fibrosus, and ligamentum flavum appear to be the physical soft tissue restraints that need to be disrupted to produce a unilateral facet dislocation.

Adolescent↗
PubMed2001

Fenestration of the extracranial vertebral artery: review of the literature.

STUDY DESIGN: A case report on fenestration of the extracranial vertebral artery found at forensic autopsy. OBJECTIVE: To describe an extracranial vertebral artery fenestration involving the subaxial cervical region, assessed radiographically and angiographically at forensic autopsy, in a young man. SUMMARY OF BACKGROUND DATA: Duplications or fenestrations of the extracranial course of the vertebral artery are rare and seen almost exclusively as a coincidental finding in angiographic studies. The terms "fenestration" and "duplication" are often incorrectly used synonymously. The former describes the passage of the duplicated vessel within the vertebral foramen transversarium, whereas the latter refers to the duplicated vessel coursing additionally through the spinal canal. The reported cases describing duplication are more common. Only three cases of vertebral extracranial fenestrations, involving only the upper cervical spinal segments, have been described in the literature. RESULTS: Angiography showed a fenestration of the vertebral artery localized between the intervertebral spaces of C2-C3 and C3-C4. At dissection, the vertebral artery appeared as a single vessel in the area of the fenestration. Histologically, a distinct difference in the thickness and composition of the vessel walls was found between the two vessel trunks. At autopsy, no further anomalies were observed in the vessels supplying the brain, which is contrary to the commonly held belief that fenestration is frequently associated with vascular malformations. CONCLUSION: Fenestration of the extracranial course of the vertebral artery is a developmental or congenital anomaly. A review of the literature demonstrated that this is apparently only a coincidental finding and has no pathologic significance.

Adolescent↗
PubMed2001

The cause of neurologic deterioration after acute cervical spinal cord injury.

STUDY DESIGN: A retrospective review was performed to identify patients at risk for secondary neurologic deterioration after complete cervical spinal cord injury. OBJECTIVE: To examine the causes of early neurologic deterioration in patients with complete spinal cord injury at a regional spinal cord injury center. SUMMARY OF BACKGROUND DATA: After complete spinal cord injury, neurologic deterioration occurs in a subgroup of patients. Despite anecdotal reports, no study has clearly identified the subgroups at highest risks. METHODS: One hundred eighty-two patients with complete spinal cord injury were identified among 1904 consecutive patients with acute spinal trauma evaluated from March 1993 through September 1999. Parameters analyzed included demographics, mechanism of injury, American Spinal Cord Injury Association (ASIA) level on admission and during hospital stay, onset of ascension, blood pressure, hemoglobin, febrile episode, heparin administration, and the timing of operation and traction. Radiographs of patients with ascending complete spinal cord injury were reviewed with attention to fracture type and neurologic and vascular injuries. RESULTS: Twelve of 186 patients with ASIA Grade A (6.0%) complete spinal cord injury had neurologic deterioration during the first 30 days after injury. No patients with penetrating injuries had deterioration. A significant association between death and ascension was observed. The onset of ascension of the injury could be categorized into three discrete temporal subsets. Early deterioration (less than 24 hours) was typically related to traction and immobilization. Delayed deterioration (between 24 hours and 7 days) was associated with sustained hypotension in patients with fracture dislocations. Late deterioration (more than 7 days) was observed in a patient with vertebral artery injuries. CONCLUSION: Delayed neurologic deterioration in complete spinal cord injury (ASIA A) is not rare. Specific causes were identified among discrete temporal subgroups. Management of complete spinal cord injury can be improved with recognition of these temporal patterns and earlier intervention.

Adolescent↗
PubMed2001

The significance of thoracolumbar spinal canal size in spinal cord injury patients.

STUDY DESIGN: A prospective, consecutive case series. OBJECTIVES: To determine the relation between spinal canal dimensions and Injury Severity Score and their association with neurologic sequelae after thoracolumbar junction burst fracture. SUMMARY OF BACKGROUND DATA: There is a relation in the cervical spine between spinal canal dimension and its association with neurologic sequelae after trauma. A similar relation at the thoracolumbar junction has not been conclusively established. METHODS: Forty-three patients with thoracolumbar junction burst fractures (T12-L2),13 with and 30 without neurologic deficit, were included. Computed tomographic scans were used to measure the sagittal and transverse diameters and the surface area of the spinal canal at the level of injury, as well as one level above and one level below the fracture level. Injury severity score was calculated for both groups. Statistical analysis comparing those with a neurologic deficit to those without was performed by Student's t test. RESULTS: The ratio of sagittal-to-transverse diameter at the level of injury was significantly smaller in patients with a neurologic deficit than in those without a neurologic deficit (P < 0.05). The mean transverse diameter at the level of injury was significantly larger in patients with neurologic deficit than in the neurologically intact patients (P < 0.05). The surface area of the canal at the level below the injury was significantly larger in the patients with a neurologic deficit than in those without a deficit (P < 0.05). Patients with a neurologic deficit had a statistically higher Injury Severity Score when admitted than those without a neurologic deficit (P < 0.0001), although the difference became insignificant after the neurologic component of the scoring system was eliminated. CONCLUSION: There are no anatomic factors at the thoracolumbar junction that predispose to neurologic injury after burst fracture. The shape of the canal after injury, however, as determined by the sagittal-to-transverse diameter ratio, was predictive of neurologic deficit.

Adolescent↗
PubMed2001

The risk of foraminal violation and nerve root impingement after anterior placement of lumbar interbody fusion cages.

STUDY DESIGN: Three groups of six embalmed cadaver spines underwent placement of lumbar interbody fusion cages centered either at midline, 10% lateral of midline, or 20% lateral of midline. The spines were evaluated for evidence of neuroforamen violation or nerve root impingement. OBJECTIVES: To determine the potential for foraminal violation or nerve root impingement after correct placement and lateral misplacement of lumbar interbody fusion cages. SUMMARY OF BACKGROUND DATA: Radicular symptoms after anterior cage placement have raised some concern about the potential for inadvertent device-related foraminal violation not adequately appreciated by intraoperative fluoroscopy. METHODS: Preoperative computed tomography scanning and plain radiography was used to measure endplate dimensions at L4-L5 and to template the appropriately sized interbody fusion cages. The cadaveric specimens were randomly divided into three groups of six (Groups I-III) and instrumented at L4-L5 either at midline (I) or 10% (II) or 20% (III) lateral of midline. Postoperative computed tomography and plain radiography was evaluated for evidence of neuroforamen violation, followed by dissection of the specimens. RESULTS: Foraminal violation occurred in one of six spines in group II (10% off midline) and in three of six spines in group III (20% off midline). Two of the three cadavers in group III with foraminal violation also were noted to have nerve root abutment on computed tomography scans and spinal dissection. CONCLUSIONS: Excessive lateral placement of lumbar interbody fusion cages may result in foraminal violation and possible nerve encroachment. The "safe zone" for centering the cages extends approximately 5 mm on either side of midline.

Foramen Magnum↗
PubMed2001

Distraction extension injuries of the cervical spine.

Twenty-four consecutive patients with cervical distraction extension injuries were retrospectively reviewed to study the safety and efficacy of various treatment protocols in this type of cervical spine injury. Sixteen of 24 patients with cervical distraction extension injuries underwent surgical stabilization. All patients undergoing surgical stabilization were noted to have a stable fusion at their latest follow-up. There were three instances of surgically related neurologic deterioration as a result of over-distraction of the anterior column interspace at the time of graft placement. The overall mortality rate was 42% in this aged patient population. Anterior reconstruction of the cervical spine with an anterior cervical graft and plate acting as a tension band is the ideal treatment method for stabilization of acute distraction extension injuries involving primarily the soft tissue structures (anterior longitudinal ligament and intervertebral disc). Type 2 injuries, depending on the degree of displacement and the adequacy of closed reduction, may need to be approached initially posteriorly to obtain adequate alignment, followed by an anterior reconstructive procedure. Great care should be taken during anterior graft placement to avoid over-distraction of the spine. If nonsurgical intervention is selected, close regular radiographic follow-up is necessary to detect early vertebral malalignment, which may predispose to spinal cord dysfunction. Older patients sustaining this injury have a high mortality rate.

Adult↗
PubMed2000

The effects of staged static cervical flexion-distraction deformities on the patency of the vertebral arterial vasculature.

STUDY DESIGN: Thirty-five fresh frozen cervical spine specimens underwent vertebral artery cannulization and angiography to determine the static influence of the four stages of subaxial flexion-distraction injuries as described by Allen et al on vertebral artery patency. OBJECTIVES: To evaluate the degree of vertebral vessel deformation and potential injury in staged static flexion-distraction deformities of the cervical spine. SUMMARY AND BACKGROUND DATA: Asymptomatic vertebral artery injury is found in up to 19% of all patients who incur trauma to the lower cervical spine. This incidence increases in flexion-distraction deformities. It is unclear as to the individual contributions of various force loads and resultant deformity on the etiology of these injuries. RESULTS: No significant deformation in vertebral artery flow was noted in the flexion-distraction Stage I injuries within the physiologic range of cervical flexion. Flexion-distraction Type II and III injuries (unilateral and bilateral facet dislocations, respectively) demonstrated considerable impairment to vertebral artery dye flow in proportion to the degree of vertebral deformity. Manipulating the dislocated vertebral segments into a localized lordosis (flexion-distraction Stage II) further impaired vertebral vessel patency. Coexistent rupture of the vertebral radicular vessels was a constant finding in Stage II and III injuries. Longitudinal stretch deformities of the vertebral artery were limited primarily to the injured vertebral segment. Stage IV injuries resulted in irreversible disruption of vertebral dye flow. CONCLUSION: The static deformity of flexion-distraction Stage II to IV subaxial cervical injuries results in significant objective compression of the vertebral vasculature. The precise contribution of static cervical malalignment related to advanced staged flexion distraction injuries on irreversible vertebral vessel flow disruption is presently uncertain.

Adolescent↗
PubMed2000

Placement of pedicle screws in the human cadaveric cervical spine: comparative accuracy of three techniques.

STUDY DESIGN: This investigation was conducted in two parts. In the first part, a morphometric analysis of critical cervical pedicle dimensions were measured to create guidelines for cervical pedicle screw fixation based on posterior cervical topography. In the second part of the study, a human cadaver model was used to assess the accuracy and safety of transpedicular screw placement in the subaxial spine using three different surgical techniques: 1) using surface landmarks established in the first part of the study, 2) using supplemental visual and tactile cues provided by performing laminoforaminotomies, and 3) using a computer-assisted surgical guidance system. OBJECTIVE: To assess the accuracy of transpedicular screw placement in the cervical spine using three surgical techniques. SUMMARY OF BACKGROUND DATA: A three-column fixation device implanted to secure an unstable cervical spine can be a valuable tool with a biomechanical advantage in the spine surgeon's armamentarium. Despite this advantage, concerns over surgical neurovascular complications have surfaced. Cadaver-based morphometric measurements used to guide the surgeon in the placement of a pedicle screw show significant variability, raising legitimate concerns as to whether transpedicular fixation can be applied safely. METHODS: Precise measurements of 14 human cadaveric cervical spines were made by two independent examiners of pedicle dimensions, angulation, and offset relative to the lateral mass boundaries. On the basis of this analysis, guidelines for pedicle screw placement relative to posterior cervical topography were derived. In the second part of the study, 12 human cadaveric cervical spines were instrumented with 3.5-mm screws placed in the pedicles C3-C7 according to one of three techniques. Cortical integrity and neurovascular injury were then assessed by obtaining postoperative computed tomography scans (1-mm cuts) of each specimen. Cortical breaches were classified into critical or noncritical breaches. RESULTS: Linear measurements of pedicle dimensions had a wide range of values with only fair interobservercorrelation. Angular measurements showed similarangulation in the transverse plane (40 degrees ) at each level. With respect to the sagittal plane, both C3 and C4 pedicles were oriented superiorly relative to the axis of the lateral mass, whereas the C6 and C7 pedicles were oriented inferiorly. The dorsal entry point of the pedicle on the lateral mass defined by transverse and sagittal offset had similar mean values with wide ranges, although there often was excellent correlation between observers. There were no significant interlevel, right/left, or male/female differences noted with respect to offset. Using one of three techniques, 120 pedicles were instrumented. In group 1 (morphometric data): 12.5% of the screws were placed entirely within the pedicle; 21.9% had a noncritical breach; and 65. 5% had a critical breach. In group 2 (laminoforaminotomy), 45% of the screws were within the pedicle; 15.4% had a noncritical breach; and 39.6% had a critical breach. In group 3 (computer-assisted surgical guidance system), 76% of the screws were entirely within the pedicle; 13.4% had a noncritical breach; and 10.6% had a critical breach. Regardless of the technique used, the vertebral artery was the structure most likely to be injured. CONCLUSIONS: On the basis of the morphometric data, guidelines for cervical spine pedicle screw placement at each subaxial level were derived. Although a statistical analysis of cadaveric morphometric data obtained from the cervical spine could provide guidelines for transpedicular screw placement based on topographic landmarks, sufficient variation exists to preclude safe instrumentation without additional anatomic data. Insufficient correlation between different surgeons' assessments of surface landmarks attests to the inadequacy of screw insertion techniques in the cervical spine based on such specific topographic guide

Aged↗
PubMed2000

Health outcome assessment before and after anterior cervical discectomy and fusion for radiculopathy: a prospective analysis.

STUDY DESIGN: A prospective assessment, performed using the Health Status Questionnaire, of the outcomes for 28 patients with cervical radiculopathy treated with one- or two-level anterior cervical discectomy and fusion. OBJECTIVE: To assess patient outcome using the Health Status Questionnaire after one- or two-level anterior cervical discectomy and fusion. SUMMARY OF BACKGROUND DATA: Although outcomes for many types of surgical procedures already have been evaluated, few have focused on the results of cervical surgery. METHODS: Before and after anterior cervical discectomy and fusion for cervical radiculopathy, 28 patients filled out the Health Status Questionnaire. The average follow-up interval was 21.8 months. There were 10 men and 18 women, with an average age of 44 years. All outcome instruments were graded for individual scores of general health, physical function, role limitation because of physical health problems, role limitation because of emotional problems, social function, mental health, bodily pain, and energy. Data were analyzed using the age (< 55 vs. > 55), worker's compensation status, and education status of the patient. Preoperative and postoperative scores were compared for each subscale. RESULTS: Statistically significant improvements were found in postoperative scores for bodily pain (P < 0.001), vitality (P = 0.003), physical function (P = 0.01), role function/physical (P = 0.0003), and social function (P = 0.0004). No significant differences were found before and after surgery for three health scales: general health, mental health, and role function associated with emotional limitations. Age, educational status, and history of compensation litigation did not appear to affect outcome measures. CONCLUSIONS: Although this is a preliminary report involving 28 patients, it would appear, based on the results of the Health Status Questionnaire, that anterior cervical discectomy and fusion performed on appropriately selected patients is a highly reliable surgical procedure for the management of cervical radiculopathy. Additional disease-specific questions may provide more sensitivity in evaluating radiculopathy after surgical and nonsurgical intervention.

Adult↗