Biomedical subjects

A J Ghanayem

Publications and source records attributed to A J Ghanayem.

11 recordsLinked to original sources

PubMed2000

Load-carrying capacity of the human cervical spine in compression is increased under a follower load.

STUDY DESIGN: An experimental approach was used to test human cadaveric cervical spine specimens. OBJECTIVE: To assess the response of the cervical spine to a compressive follower load applied along a path that approximates the tangent to the curve of the cervical spine. SUMMARY OF BACKGROUND DATA: The compressive load on the human cervical spine is estimated to range from 120 to 1200 N during activities of daily living. Ex vivo experiments show it buckles at approximately 10 N. Differences between the estimated in vivo loads and the ex vivo load-carrying capacity have not been satisfactorily explained. METHODS: A new experimental technique was developed for applying a compressive follower load of physiologic magnitudes up to 250 N. The experimental technique applied loads that minimized the internal shear forces and bending moments, loading the specimen in nearly pure compression. RESULTS: A compressive vertical load applied in the neutral and forward-flexed postures caused large changes in cervical lordosis at small load magnitudes. The specimen collapsed in extension or flexion at a load of less than 40 N. In sharp contrast, the cervical spine supported a load of up to 250 N without damage or instability in both the sagittal and frontal planes when the load path was tangential to the spinal curve. The cervical spine was significantly less flexible under a compressive follower load compared with the hypermobility demonstrated under a compressive vertical load (P < 0.05). CONCLUSION: The load-carrying capacity of the ligamentous cervical spine sharply increased under a compressive follower load. This experiment explains how a whole cervical spine can be lordotic and yet withstand the large compressive loads estimated in vivo without damage or instability.

Cadaver↗

PubMed2000

Iatrogenic lumbar spondylolisthesis: treatment by anterior fibular and iliac arthrodesis.

A retrospective independent radiographic and chart review was undertaken for 17 patients who underwent a unique anterior salvage procedure for iatrogenic and progressive postoperative spondylolisthesis. This one-stage anterior transabdominal discectomy, reduction, stabilization, and arthrodesis was first performed in 1979. Of the 17 patients, all complained of leg pain, 14 of back pain, 11 had neurogenic claudication, and 2 were bedridden preoperatively because of their pain. Of the 17 patients, 7 had no neurologic deficits, 2 had cauda equina syndrome, and the remaining 8 had motor root deficits. The average number of posterior operations before our salvage procedure was 1.8, with a range of 1 to 3. Eight patients had an average of 1.6 attempts at posterior arthrodesis, with a range of 1 to 3 procedures. Two patients had a grade I spondylolisthesis, 11 a grade II, and 4 a grade III. Follow-up was available for 16 patients from 2 years and 3 months to 11 years and 5 months after the index operation (mean, 6 years and 5 months). One patient with severe cardiovascular disease died perioperatively. This anterior procedure was able to restore spinal stability and decompress the neural elements in 13 of 16 patients. Eleven obtained a solid arthrodesis. Three patients required further spinal surgery: two posterior fusions for symptomatic nonunions and one posterior foraminotomy for persistent foraminal stenosis. No patient deteriorated neurologically, the two with cauda equina syndrome recovered, and all but one patient with motor root deficits recovered fully. At latest follow-up, there were six excellent, seven good, and three fair results. There were no poor results. Although technically difficult and troubled by complications, the relative historical merits and principles of this unique anterior salvage procedure probably warrant further consideration, especially in light of evolving anterior surgical technologies.

Adult↗

PubMed1999

Anterior cervical graft and plate load sharing.

Anterior discectomy and fusion with an interbody bone graft and anterior plate is a common procedure in cervical spine surgical management. However, the graft may be shielded from some mechanical loading by the plate. Mechanical testing was performed on six cadaveric calf spines that were subjected to a simulated anterior cervical discectomy and fusion with an interbody bone graft alone and with an anterior plate to determine the amount of load sharing between the graft and plate. The load-displacement data were used to compute the amount of load sharing between the graft and the plate as a continuous function of the applied axial compression load. Although the percent load transmitted through the graft decreased (53 to 41%) as the axial load increased (45 to 90 N), the magnitude of load transmitted through the graft increased (24 to 37 N), with corresponding intervertebral strains <6%. In a single-level procedure, an anterior cervical plate serves as a load-sharing device rather than a load-shielding device, enabling graft consolidation as observed in clinical studies.

Animals↗

PubMed1998

Cervical interbody fusion cages. An animal model with and without bone morphogenetic protein.

STUDY DESIGN: The Alpine goat model for multilevel anterior cervical discectomy and fusion was used to analyze the use of an intervertebral fusion device to promote an arthrodesis after anterior cervical discectomy. Comparisons were drawn with biomechanical, histologic, and radiographic data. OBJECTIVES: To analyze the use of an intervertebral fusion device, with and without a bone graft substitute, to promote an arthrodesis anterior cervical discectomy. SUMMARY OF BACKGROUND DATA: In previous studies, the goat cervical spine has proven to be an excellent model for examining the healing of fusions using bone grafts, instrumentation, or bone substitutes. METHODS: Three-level anterior cervical dissectomies were performed on 21 mature Alpine goats. Three treatment groups of seven goats each were used. Group I used a standard titanium cervical BAK device filled with autogenous bone graft. Group II used a hydroxyapatite-coated BAK device filled with autogenous bone graft. Group III used a BAK device filled with recombinant human bone morphogenetic protein-2. RESULTS: Radiographically, no cages became displaced. Lucencies were seen around 3 of the 21 cages in Group 1, 4 cages in Group II, and none in Group III. Fluorochrome analysis revealed that the recombinant human bone morphogenetic protein-2-filled cages had an accelerated rate of bone growth around and through each cage-vertebral body interface at 3 weeks. A successful arthrodesis was also more likely with a recombinant human bone morphogenetic protein-2-filled cage (95%) than the hydroxyapatite-coated (62%) or the standard (48%) cage. Biomechanical stiffness testing did not reveal any statistically significant differences between the three groups. There was a tendency for successfully arthrodesed interspaces to be stiffer than those that were not. CONCLUSIONS: The use of a threaded intervertebral fusion cage, with or without hydroxyapatite coating, filled with autogenous bone graft provides a fusion rate that is slightly better than those previously reported using autogenous interbody bone grafts with or without plate stabilization. Recombinant human bone morphogenetic protein-2-filled cages resulted in a much higher arthrodesis rate and accelerated bone formation compared with either autogenous bone-filled BAK devices, or autogenous interbody bone grafts with or without plate stabilization.

Animals↗

PubMed1997

Biomechanical comparison of posterior lumbar interbody fusion cages.

STUDY DESIGN: Cadaveric human and bovine lumbar spine models simulating the acute postoperative period were used to compare the biomechanical properties of two designs of intervertebral body threaded fusion cages. The instrumented spines were compared with intact spines and with spines with resected posterior elements, representing a revision case. OBJECTIVE: To determine the relative biomechanical performance of these competing devices. SUMMARY OF BACKGROUND DATA: These cages are currently under clinical investigation, and basic biomechanical data are needed. METHODS: Insertion torques and maximum pushout loads were measured for each cage. Intact spines, posteriorly instrumented spines (posterior lumbar interbody fusion), and spines with resected posterior elements were loaded in axial compression, flexion and extension bending, and axial torsion. Stiffness comparisons were made between the different configurations. RESULTS: Insertion torques and pushout loads were similar for the cages. Both cages significantly increased stiffnesses above those of the intact spines and the resected spines. The BAK-instrumented spines were more stiff in axial compression, while the Threaded Interbody Fusion Device spines were more stiff in extension. CONCLUSIONS: This study revealed the two cages to have similar biomechanical characteristics immediately after posterior insertion and warrant further clinical studies.

Animals↗

PubMed1997

Anterior instrumentation in the management of thoracolumbar burst fractures.

Anterior instrumentation in the treatment of thoracolumbar fractures has progressed significantly during the past 2 decades. These fixation systems have evolved to meet the anatomic, biomechanical, and imaging challenges associated with internal fixation of the thoracolumbar spine. The evolution of these devices will be reviewed, and from this, the indications and surgical techniques necessary for the safe and effective use of the device will be discussed. This study also reports the authors' initial clinical experience using the Z plate anterior thoracolumbar plating system in the treatment of thoracolumbar burst fractures. The study consists of 12 consecutive adult patients who underwent a 1-stage anterolateral decompressive and stabilization procedure for burst fractures from T9-L3. The indications for surgery included neurologic deficits, deformity, progressive kyphosis, and late pain. Ten of the 12 patients maintained their postoperative sagittal alignment or a significant portion of their kyphosis reduction. Two patients with severe kyphotic deformities greater than 50 degrees lost 10 degrees and 20 degrees of their reduction at last followup. All 3 patients with neurologic deficits recovered. There were no neurologic or perioperative complications. Eleven of the 12 patients obtained a good or excellent functional outcome. Anterior arthrodesis using instrumentation stabilization after a 1-stage anterolateral decompression and reduction procedure can yield successful clinical results in the treatment of thoracolumbar burst fractures.

Adolescent↗

PubMed1996

Osteoarthrosis of the atlanto-axial joints. Long-term follow-up after treatment with arthrodesis.

We evaluated the results for fifteen patients in whom symptomatic osteoarthrosis of the atlanto-axial joints had been treated with an atlanto-axial or occipitocervical arthrodesis between 1973 and 1990. Thirteen patients had long-term follow-up (average duration, seven years and two months; range, four years and two months to nineteen years and two months). The two remaining patients had died: one, four days postoperatively, from a cardiopulmonary arrest, and the other, one year and eight months postoperatively, from complications related to bladder cancer. Preoperatively, all fifteen patients reported pain in the occipitocervical region that increased with any attempt at rotation of the neck and was unresponsive to immobilization with a collar and to analgesics. The average duration of the symptoms before the arthrodesis was three years. One patient had acute quadriparesis. All patients had radiographic evidence of oesteoarthrosis involving the lateral atlanto-axial articulations. Four patients had atlanto-axial instability with an average of five millimeters (range, three to ten millimeters) of motion at the anterior atlanto-odontoid interval. Six patients had an associated spontaneous subaxial fusion, which was secondary to osteoarthrosis in five; three of the five also had atlanto-axial instability. Fourteen patients were managed with a posterior arthrodesis and one, with an anterior transoral arthrodesis. The procedures were performed to relieve pain, to stabilize the atlanto-axial joints, and to restore neurological function. Of the fourteen patients who were followed, thirteen had a solid fusion and one had a stable pseudarthrosis. The patient who had quadriparesis recovered. At the latest follow-up evaluation, thirteen patients had an excellent result and one had a fair result as determined with use of a modification of the criteria of Robinson et al. There were no poor results. Atlanto-axial arthrodesis can effectively relieve occipitocervical pain and correct atlanto-axial instability secondary to osteoarthrosis.

Aged↗

PubMed1996

Cervical spine infections.

Cervical spine infections arise from a variety of etiologies including postsurgical, iatrogenic, and hematogenous routes. Clinical history, physical examinations, and diagnostic studies all play an integral role in the diagnosis and treatment of these infections. Successful treatment depends on a proper and timely diagnosis, understanding the etiology, and defining the extent to which the infectious process involves the spinal supporting and neurologic elements. Surgical treatment is required when there is abscess formation, instability, progressive kyphosis secondary to vertebral body collapse, or canal compromise with neurologic deficits.

Adult↗

PubMed1995

The effect of laparotomy and external fixator stabilization on pelvic volume in an unstable pelvic injury.

OBJECTIVE: Determine if laparotomy further destabilizes an unstable pelvic injury and increases pelvic volume, and if reduction and stabilization restores pelvic volume and prevents volume changes secondary to laparotomy. DESIGN: Cadaveric pelvic fracture model. MATERIALS AND METHODS: Unilateral open-book pelvic ring injuries were created in five fresh cadaveric specimens by directly disrupting the pubic symphysis, left sacroliac joint, and sacrospinous and sacrotuberous ligaments. Pelvic volume was determined using computerized axial tomography for the intact pelvis, disrupted pelvis with both a laparotomy incision opened and closed, and disrupted pelvis stabilized and reduced using an external fixator with the laparotomy incision opened. MEASUREMENTS AND MAIN RESULTS: The average volume increase in the entire pelvis (from the top of the iliac crests to the bottom of the ischial tuberosities) between a nonstabilized injury with the abdomen closed and then subsequently opened was 15 +/- 5% (423 cc). The average increase in entire pelvic volume between a stabilized and reduced pelvis and nonstabilized pelvis, both with the abdomen open, was 26 +/- 5% (692 cc). The public diastasis increased from 3.9 to 9.3 cm in a nonstabilized pelvis with the abdomen closed and then subsequently opened. Application of a single-pin anterior-frame external fixator reduced the pubic diastasis anatomically and reduced the average entire and true (from the pelvic brim to the ischeal tuberosities) pelvic volumes to within 3 +/- 4 and 8 +/- 6% of the initial volume, respectively. CONCLUSIONS: We believe that the abdominal wall provides stability to an unstable pelvic ring injury via a tension band effect on the iliac wings. Our results demonstrate that a laparotomy further destabilized an open-book pelvic injury and subsequently increased pelvic volume and pubic diastasis. This could potentially increase blood loss from the pelvic injury and delay the tamponade effect of reduction and stabilization. A single-pin external fixator prevents the destabilizing effect of the laparotomy and effectively reduces pelvic volume. These data support reduction and temporary stabilization of unstable pelvic injuries before or concomitantly with laparotomy.

Aged↗

PubMed1995

Emergent treatment of pelvic fractures. Comparison of methods for stabilization.

The emergent care of an unstable pelvic ring disruption in the patient who is hemodynamically unstable includes rapid application of military antishock trousers or an external fixator in an attempt to control bleeding and hemodynamically stabilize the patient. However, use of the military antishock trousers is limited in that it restricts access to the abdomen and lower extremities. The external fixator is limited at many institutions by the need to apply it in the operating room. Two experimental devices have been developed to provide emergent pelvic fracture reduction and temporary stabilization in the trauma room, while maintaining access to the abdomen and lower extremities. This study compared the efficacy of pelvic fracture reduction and stabilization in a cadaveric model using an external fixator with the efficacy of 2 experimental devices, the pelvic stabilizer and the pelvic c-clamp. Based on their ability to restore pelvic volume and reduce pubic diastasis and their application time, the 3 devices performed similarly. Complications in applying each device were noted but were of less clinical significance for the external fixator. Surgeon practice on cadavera before clinical use will help ensure safe application of either experimental device in the trauma room.

Aged↗

PubMed1994

Transient paraplegia from intraoperative intercostal nerve block after transthoracic discectomy.

OBJECTIVE: To present two patients with transient paraplegia from intercostal nerve blocks after transthoracic discectomy. METHODS: The preoperative, intraoperative, and postoperative courses of two patients who underwent transthoracic discectomies were reviewed. A literature review of complications from thoracic disc excisions and intercostal nerve blocks also was conducted. RESULTS: Two patients experienced transient paraplegia from intercostal nerve blockade after thoracotomy for thoracic discectomies. Although transient paraplegia (or regional anesthesia) after intercostal nerve blocks has been reported and is consistent with the clinical course seen in our two patients, it has not been reported after thoracotomy for decompression of the spinal cord. CONCLUSION: Because of the inherent risk of neurologic injury after thoracic discectomy, the authors discourage the use of intercostal nerve blocks for relieving postoperative pain after transthoracic discectomy.

Aged↗