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Biomedical subjects

Michael P Steinmetz

Publications and source records attributed to Michael P Steinmetz.

At least 19 recordsLinked to original sources
PubMed2007

Cervical deformity correction.

Subaxial cervical deformities most often occur in the sagittal plane, primarily as kyphosis. Kyphosis may develop secondary to advanced degenerative disease, trauma, neoplastic disease, or after surgery. Whatever the cause, the development of cervical deformity should be avoided and corrected when appropriate because the greater the deformity, the greater the probability of an associated neurological deficit or chronic pain. Patients usually present with mechanical type cervical pain, with or without neurological deficit (i.e., myelopathy). They may also be relatively asymptomatic. Work-up includes appropriate imaging studies, such as radiographs, including dynamic images, and magnetic resonance imaging or computed tomography myelography. The deformity may be accurately assessed and an appropriate surgical strategy undertaken. Depending on flexibility of the deformity and the presence or absence of facet ankylosis, a dorsal, ventral, or combined approach may be used. All approaches are unique in their ability to correct a deformity and in their associated complications. A comprehensive discussion of each is undertaken.

Cervical Vertebrae↗
PubMed2006

Axially dynamic implants for stabilization of the cervical spine.

OBJECTIVE: Subsidence is a naturally occurring process that is observed during aging and after spine surgery. Rigid cervical spine instrumentation is excellent for stabilizing the spine. These devices, however, also retard subsidence after surgery. Thus, the implant carries much of the axial load, rather than sharing the axial load with the bone graft. This results in an increased incidence of construct failures, pseudoarthrosis, or both, which often occur late in the postoperative course. METHODS: In contrast, dynamic implants allow normal (natural) subsidence to occur, while effectively stabilizing the spine by preventing translation, rotation, and angular deformation. Load sharing, which works with, instead of against, the normal biology of bone healing, occurs with axially dynamic implants, resulting in more robust and earlier fusions. RESULTS: Diminished incidences of construct failures have been reported with dynamic implants. CONCLUSION: Dynamic implants seem to be the system of choice for ventral cervical stabilization in selected patients.

Cervical Vertebrae↗
PubMed2006

Regional instability following cervicothoracic junction surgery.

OBJECT: The cervicothoracic junction (CTJ) is the transitional region between the cervical and thoracic sections of the spinal axis. Because it is a transitional zone between the mobile lordotic cervical and rigid kyphotic thoracic spines, the CTJ is a region of potential instability. This potential for instability may be exaggerated by surgical intervention. METHODS: A retrospective review of all patients who underwent surgery involving the CTJ in the Department of Neurosurgery at the Cleveland Clinic Foundation during a 5-year period was performed. The CTJ was strictly defined as encompassing the C-7 vertebra and C7-T1 disc interspace. Patients were examined after surgery to determine if treatment had failed. Failure was defined as construct failure, deformity (progression or de novo), or instability. Variables possibly associated with treatment failure were analyzed. Statistical comparisons were performed using the Fisher exact test. Between January 1998 and November 2003, 593 CTJ operations were performed. Treatment failed in 14 patients. Of all variables studied, failure was statistically associated with laminectomy and multilevel ventral corpectomies with fusion across the CTJ. Other factors statistically associated with treatment failure included histories of cervical surgery, tobacco use, and surgery for the correction of deformity. CONCLUSIONS: The CTJ is a vulnerable region, and this vulnerability is exacerbated by surgery. Results of the present study indicate that laminectomy across the CTJ should be supplemented with instrumentation (and fusion). Multilevel ventral corpectomies across the CTJ should also be supplemented with dorsal instrumentation. Supplemental instrumentation should be considered for patients who have undergone prior cervical surgery, have a history of tobacco use, or are undergoing surgery for deformity correction.

Adult↗
PubMed2005

Chronic enhancement of the intrinsic growth capacity of sensory neurons combined with the degradation of inhibitory proteoglycans allows functional regeneration of sensory axons through the dorsal root entry zone in the mammalian spinal cord.

Peripherally conditioned sensory neurons have an increased capacity to regenerate their central processes. However, even conditioned axons struggle in the presence of a hostile CNS environment. We hypothesized that combining an aggressive conditioning strategy with modification of inhibitory reactive astroglial-associated extracellular matrix could enhance regeneration. We screened potential treatments using a model of the dorsal root entry zone (DREZ). In this assay, a gradient of inhibitory chondroitin sulfate proteoglycans (CSPGs) stimulates formation of dystrophic end bulbs on adult sensory axons, which mimics regeneration failure in vivo. Combining inflammation-induced preconditioning of dorsal root ganglia in vivo before harvest, with chondroitinase ABC (ChABC) digestion of proteoglycans in vitro allows for significant regeneration across a once potently inhibitory substrate. We then assessed regeneration through the DREZ after root crush in adult rats receiving the combination treatment, ChABC, or zymosan pretreatment alone or no treatment. Regeneration was never observed in untreated animals, and only minimal regeneration occurred in the ChABC- and zymosan-alone groups. However, remarkable regeneration was observed in a majority of animals that received the combination treatment. Regenerated fibers established functional synapses, as demonstrated electrophysiologically by the presence of an H-reflex. Two different postlesion treatment paradigms in which the timing of both zymosan and ChABC administration were varied after injury were ineffective in promoting regeneration. Therefore, zymosan pretreatment, but not posttreatment, of the sensory ganglia, combined with ChABC modification of CSPGs, resulted in robust and functional regeneration of sensory axons through the DREZ after root injury.

Animals↗
PubMed2005

Awake craniotomy for microsurgical obliteration of mycotic aneurysms: technical report of three cases.

OBJECTIVE AND IMPORTANCE: Infectious (mycotic) aneurysms that do not resolve with medical treatment require surgical obliteration, usually requiring sacrifice of the parent artery. In addition, patients with mycotic aneurysms frequently need subsequent cardiac valve repair, which often necessitates anticoagulation. Three cases of awake craniotomy for microsurgical clipping of mycotic aneurysms are presented. Awake minimally invasive craniotomy using frameless stereotactic guidance on the basis of computed tomographic angiography enables temporary occlusion of the parent artery with neurological assessment before obliteration of the aneurysm. CLINICAL PRESENTATION: A 56-year-old woman presented with progressively worsening mitral valve disease and a history of subacute bacterial endocarditis and subarachnoid hemorrhage 30 years previously. A cerebral angiogram revealed a 4-mm left middle cerebral artery (MCA) angular branch aneurysm, which required obliteration before mitral valve replacement. The second patient, a 64-year-old woman with a history of rheumatic fever, had an 8-mm right distal MCA aneurysm diagnosed in the setting of pulmonary abscess and worsening cardiac function as a result of mitral valve disease. The third patient, a 57-year-old man with a history of fevers, night sweats, and progressive mitral valve disease, had an enlarging left MCA angular branch aneurysm despite the administration of antibiotics. Because of their location on distal MCA branches, none of the aneurysms were amenable to preoperative test balloon occlusion. INTERVENTION: After undergoing stereotactic computed tomographic angiography with fiducial markers, the patients underwent a minimally invasive awake craniotomy with frameless stereotactic navigation. In all cases, the results of the neurological examination were unchanged during temporary parent artery occlusion and the aneurysms were successfully obliterated. CONCLUSION: Awake minimally invasive craniotomy for an infectious aneurysm located in eloquent brain enables awake testing before permanent clipping or vessel sacrifice. Combining frameless stereotactic navigation with computed tomographic angiography allowed us to perform the operation quickly through a small craniotomy with minimal exploration.

Aneurysm, Infected↗
PubMed2005

Techniques for the ventral correction of postsurgical cervical kyphotic deformity.

Progressive kyphotic deformity of the cervical spine may be a late sequela of congenital cervical anomalies, degenerative disc disease, neoplasm, cervical trauma, and surgical procedures. Of these, postsurgical kyphosis is the most common and can occur after ventral and dorsal surgeries of the cervical spine. The purpose of this article is to review the causes and clinical presentation of postsurgical cervical kyphosis and to focus on the operative planning and ventral correction techniques.

Cervical Vertebrae↗
PubMed2005

Surgical management of osseous hemangioblastoma of the thoracic spine: technical case report.

OBJECTIVE AND IMPORTANCE: Spinal hemangioblastomas usually occur as isolated, intramedullary, central nervous system masses, often as a component of von Hippel-Lindau syndrome. They may occasionally occur extradurally and give the appearance of vertebral hemangioma. Rarely, they may be purely osseous lesions. The surgical management of these lesions has not been elaborated. We present a case and discuss the management of multilevel osseous hemangioblastoma of the thoracic spine. CLINICAL PRESENTATION: A 50-year-old woman with a history of thoracic hemangioblastoma 3 years earlier presented with progressive paraparesis. Imaging revealed circumferential tumor involvement of T7 to T9, inclusive. There was severe spinal cord compression. INTERVENTION: The patient underwent surgery via a bilateral lateral extracavitary approach to the tumor. This permitted a complete spondylectomy of T7, T8, and T9; complete tumor removal; and decompression of the spinal cord. Pathological analysis confirmed hemangioblastoma. The spine was reconstructed with an interbody expandable cage and pedicle screw fixation, all placed via the dorsal approach. The patient improved neurologically after the operation. CONCLUSION: Although extremely rare, hemangioblastomas may occur in a purely osseous location. They may resemble vertebral hemangioma. Treatment should include aggressive surgical removal, although arduous, if appropriate. A bilateral lateral extracavitary approach is ideal for complete spondylectomy. With this technique, ventral and dorsal reconstruction of the spine through the same incision is possible.

Female↗
PubMed2005

Effects of age on the perioperative characteristics and short-term outcome of posterior lumbar fusion surgery.

OBJECT: Although advances in patient care have enabled surgeons to perform posterior lumbar decompression and fusion (PLDF), increased age remains a major concern when designing a treatment strategy. The authors conducted a study to evaluate if increased age has any effect on lumbar fusion surgery in terms of perioperative events. METHODS: This retrospective study comprised 129 patients (age range 25-91 years) with spondylolisthesis, lumbar stenosis and/or disc degeneration/herniation with instability, or unsuccessful results after a failed previous PLDF. The patients were stratified by age: those younger than 65 years of age (85 patients) and those at least 65 years of age (44 patients). The parameters reviewed included comorbid conditions, American Society of Anesthesiologists score, instrumentation technique (pedicle screws, a combination of pedicle screw fixation [PSF] and posterior lumbar interbody fusion [PLIF], or noninstrumented fusions), number of fused levels, operative time, estimated blood loss (EBL), complications, and hospital length of stay (LOS). Fusion strategies in the elderly tended to be more conservative. Repeated operations and PSF/PLIF procedures were less frequent in the older age group. Older age did not result in increased complications, EBL, and operative time. Longer hospital LOS was observed in the older age group (7 +/- 3.5 days) compared with the younger age group (5.5 +/- 1.9 days) (p = 0.022). CONCLUSIONS: Complications and perioperative events following PLDF in the elderly are comparable with those observed in younger patients. Withholding lumbar spine fusion solely based on advanced age is not warranted.

Adult↗
PubMed2004

Studies on the development and behavior of the dystrophic growth cone, the hallmark of regeneration failure, in an in vitro model of the glial scar and after spinal cord injury.

We have developed a novel in vitro model of the glial scar that mimics the gradient of proteoglycan found in vivo after spinal cord injury. In this model, regenerated axons from adult sensory neurons that extended deeply into the gradient developed bulbous, vacuolated endings that looked remarkably similar to dystrophic endings formed in vivo. We demonstrate that despite their highly abnormal appearance and stalled forward progress, dystrophic endings are extremely dynamic both in vitro and in vivo after spinal cord injury. Time-lapse movies demonstrated that dystrophic endings continually send out membrane veils and endocytose large membrane vesicles at the leading edge, which were then retrogradely transported to the rear of the "growth cone." This direction of movement is contrary to membrane dynamics that occur during normal neurite outgrowth. As further evidence of this motility, dystrophic endings endocytosed large amounts of dextran both in vitro and in vivo. We now have an in vitro model of the glial scar that may serve as a potent tool for developing and screening potential treatments to help promote regeneration past the lesion in vivo.

Aggrecans↗
PubMed2004

Biomechanics of metastatic spine cancer.

The spine is the most common site of skeletal metastases. Most of these occur within the vertebral body, thereby predisposing patients to pathologic fracture. The risk of fracture is related to the extent of bony destruction, location of the lesion, and inherent bone quality. The regional variation in spine anatomy exposes the cervical,thoracic, and lumbar spines to different forces,resulting in varying fracture types.

Biomechanical Phenomena↗
PubMed2004

Outcome after the treatment of spinal dural arteriovenous fistulae: a contemporary single-institution series and meta-analysis.

OBJECTIVE: Spinal dural arteriovenous fistulae (Type I spinal AVMs) are the most common type of spinal vascular malformations. The optimal treatment strategy has yet to be defined, and endovascular embolization is being offered with increasing frequency. A 7-year single-institution retrospective review of outcome with surgical management of Type I spinal AVMs is presented along with a meta-analysis of existing literature. METHODS: For the institutional analysis, a retrospective review of all patients who underwent treatment at our institution for Type I spinal AVMs was performed. Between 1995 and the present (the time frame during which endovascular treatments were available), 19 consecutive patients were treated. Follow-up was performed by clinical examination or telephone interview, and functional status was measured by use of the Aminoff-Logue score. For the meta-analysis, a MEDLINE search between 1966 and the present was performed for surgical, endovascular, or combined treatment of spinal dural arteriovenous fistula. These series were included in a meta-analysis to evaluate success and failure rates, complications, and functional outcome. Specifically, embolization and microsurgery were compared. RESULTS: For the institutional analysis, 18 of 19 patients were available for long-term follow-up after surgery. There were no surgical failures, but one complication was seen. Patients demonstrated a statistically significant improvement in gait and bladder function after surgery. For the meta-analysis, 98% of those patients treated with microsurgery had their dural arteriovenous fistulae successfully obliterated after the initial treatment, compared with only 46% with embolization, as judged by radiographic or clinical follow-up. 89% percent of patients demonstrated improvement or stabilization in neurological symptoms after surgical treatment. Few complications were demonstrated with either surgery or embolization. CONCLUSION: At this point, surgery seems to be superior to embolization for the management of spinal dural arteriovenous fistula. The fistula is usually obliterated after the initial treatment, with few clinical or radiographic recurrences. The majority of patients either improve or stabilize after treatment. Few worsen, and the morbidity is minimal. It is reasonable to attempt initial embolization, especially at the time of the initial diagnostic spinal angiogram. The treating physicians and patients should be aware of the high chance of recurrence, and patients may ultimately require surgery or repeat embolization. After endovascular therapy, patients are committed to repeat angiography and probably embolization. For these reasons, it is the authors' opinion that surgery should be used as the first-line therapy for spinal dural arteriovenous fistulae.

Adult↗
PubMed2004

A transcranial approach for direct mechanical thrombectomy of dural sinus thrombosis. Report of two cases.

Cerebral venous sinus thrombosis is often difficult to manage. Treatment options include systemically delivered anticoagulation therapy or chemical thrombolysis. Targeted endovascular delivery of thrombolytic agents is currently a popular option, but it carries an increased risk of hemorrhage. These strategies require significant time to produce thrombolysis, often in a patient with a rapidly deteriorating neurological condition. Rapid mechanical recanalization with thrombectomy is therefore very attractive; this procedure provides rapid recanalization with no increased risk of hemorrhage from use of thrombolytic agents. Nevertheless, the rheolytic catheter is large and stiff and may not be able to navigate tortuous intracranial vascular anatomy. The authors present their experience with direct dural sinus mechanical thrombectomy performed using the rheolytic catheter via a transcranial route. Two patients with dural sinus thrombosis and rapidly deteriorating levels of consciousness underwent unsuccessful attempts at mechanical thrombolysis via the usual transfemoral route. Through a burr hole over the dural sinus, mechanical thrombectomy was subsequently performed using the thrombectomy catheter. Sinus patency was restored following treatment and both patients demonstrated neurological recovery. Hemorrhage or a rapidly deteriorating neurological condition may preclude the use of systemic or locally delivered thrombolytic agents for the treatment of cerebral venous sinus thrombosis. Mechanical thrombectomy may be the treatment of choice in these circumstances. In patients with limited transfemoral access, a transcranial approach may be used to access the cerebral dural sinuses and thrombectomy may be safely and effectively performed. Further evaluation of this therapy is warranted.

Catheterization↗
PubMed2003

Atlantooccipital dislocation in children: presentation, diagnosis, and management.

Atlantooccipital dislocation (AOD) injuries are highly unstable, and usually result in significant neurological injury and death. Recently the postinjury survival period has increased. In a review of the literature the authors found 41 cases in which survival was greater than 48 hours. This is likely due to improved on-scene resuscitation, spinal immobilization, transportation, new diagnostic techniques, and a higher index of suspicion. Diagnosis is usually made with plain cervical radiographs, but there are shortcomings associated with this modality in the pediatric population. Diagnosis is aided by high-resolution computerized tomography and magnetic resonance imaging. Infants and toddlers may undergo orthotic immobilization alone, whereas older children usually undergo early occipital cervical fusion. Those with incomplete AOD may be managed successfully with orthotic immobilization.

Atlanto-Occipital Joint↗
PubMed2003

Ventral correction of postsurgical cervical kyphosis.

OBJECT: Cervical kyphotic deformation may develop after surgery involving either the ventral or dorsal approach. Regardless of the cause, the development of a cervical kyphotic deformity should be avoided, if possible, and corrected if present, when appropriate. The authors describe their experience with a technique for the ventral correction of iatrogenic (postoperative) cervical kyphosis. METHODS: A retrospective review of cases involving correction of postoperative iatrogenic cervical kyphosis via an ventral approach was performed. The authors conducted an ventral approach to kyphosis correction. The procedure required specific head positioning (in extension), convergent distraction pins, and an ventrally placed implant (axially dynamic when appropriate) with multiple points of fixation including at least one point of intermediate fixation. The pre- and postoperative sagittal angle and clinical status were evaluated. During a nearly 14-month period, 12 patients met the inclusion criteria. Ten patients underwent a minimum of 6 months of follow up. They comprised the study population. Most patients presented with mechanical neck pain as part of their symptom profile. The mean magnitude of deformity correction (pre- to postoperative) was 20 degrees of lordosis. The mean postoperative sagittal angle was 6 degrees of lordosis. The mean change in the sagittal angle during the follow-up period was 2.2 degrees of lordosis. CONCLUSIONS: The ventral approach to correction of cervical deformity led to the achievement of lordosis in all but one patient. This posture was effectively maintained during the follow-up period. All patients exhibited improvement postoperatively; three experienced complete resolution of their preoperative symptoms. When symptoms are related to postsurgical kyphosis, deformity correction should be considered. Such a procedure may be performed effectively via an ventral approach in most circumstances.

Adolescent↗
PubMed2002

Dual-strap augmentation of a halo orthosis in the treatment of atlantooccipital dislocation in infants and young children. Technical note.

Two children who were 13 months and 3 years old and who had suffered traumatic atlantooccipital dislocation were each treated by being placed in a halo orthosis for 10 weeks. Because of a continued loss of reduction due to the poor fit of the halo vest, a dual-strap augmentation was developed. This strap augmentation allowed consistent reduction to be maintained. Both children were therefore successfully treated nonsurgically with a halo vest. One child remained neurologically intact and the other had improvement in motor strength. There were no complications from the use of strap augmentation for halo vest fixation.

Atlanto-Occipital Joint↗
PubMed2002

Preliminary experience with the DOC dynamic cervical implant for the treatment of multilevel cervical spondylosis.

OBJECT: Despite the wide use of anterior cervical instrumentation in the management of multilevel cervical spondylosis, the incidences of pseudarthrosis and instrument-related failure remain high. The use of a dynamic implant may aid in the prevention of these complications. The purpose of this study was to evaluate the DOC dynamic cervical implant in the treatment of multilevel cervical spondylosis. METHODS: The authors evaluated 34 cases in which anterior multilevel cervical decompression and fusion were performed using the DOC Ventral Cervical Stabilization System. Postoperatively, and at each follow-up visit, the sagittal angle and the degree of subsidence that developed were measured. Fusion rates and clinical outcomes were also evaluated. The mean postoperative sagittal angle was 14 degrees of lordosis. The mean change in the sagittal angle during the follow-up period was 0.4 degrees of lordosis. By 6 months postoperatively some subsidence had occurred in most patients, with no subsidence occurring in only 15%. By 3 months greater than or equal to 2 mm of subsidence was demonstrated in 61% of cases. The overall fusion rate was 91%. In the majority of patients (79%) symptoms were judged to be improved or resolved. CONCLUSIONS: The DOC dynamic cervical implant permitted controlled subsidence and prevented progression of kyphotic deformity. There was one construct failure (related to a motor vehicle accident) and an overall fusion rate of 91%. The DOC implant is a safe and effective cervical construct for multilevel spondylotic disease.

Cervical Vertebrae↗
PubMedDate not supplied

Cervical laminoplasty.

Laminoplasty was developed to treat multilevel pathology of the cervical spine, namely ossification of the posterior longitudinal ligament and cervical spondylotic myelopathy. Laminoplasty was popularized in the 1980s, and since then many variations on the theme have been developed. All are similar in that they expand the cervical canal while leaving the protective dorsal elements in place. Advocates claim that this prevents the formation of the "postlaminectomy" membrane, maintains spinal alignment, and should aid in maintaining cervical range of motion. The aforementioned are all potential shortcomings of laminectomy or laminectomy and fusion. The procedure has proven to be essentially equal to other cervical decompressive procedures in the neutral or lordotic spine, and outcome has been shown to be durable.

Cervical Vertebrae↗