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Hugh J. L. Garton, Paul Park and Stephen M. Papadopoulos

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Cheerag D. Upadhyaya, Paul Park and Frank La Marca

✓ Chyloretroperitoneum is an uncommon complication following spinal surgery. The authors present the case of a patient in whom conservative treatment and initial surgical measures failed to relieve varied symptoms of postsurgical chyloretroperitoneum. Following attempts at conservative management, a peritoneal window was surgically created to divert lymphatic flow from the retroperitoneal space into the peritoneal space, where it was resorbed. This unique surgical technique provides yet another option in the treatment of refractory chyloretroperitoneum following anterior lumbar spinal surgery. The authors describe their technique and review retroperitoneal lymphatic anatomy along with similar case reports in the literature.

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Paul Park and Kevin T. Foley

Minimally invasive transforaminal lumbar interbody fusion (MI-TLIF) is a relatively new surgical procedure that appears to minimize iatrogenic soft tissue and muscle injury. The authors describe a technique for MI-TLIF that permits the surgeon to reduce spondylolisthesis percutaneously. The results in 40 consecutive patients who underwent MI-TLIF for symptomatic spondylolisthesis utilizing this approach are reviewed. Thirty cases involved a degenerative spondylolisthesis while the remaining 10 were isthmic. The minimum follow-up was 24 months with a mean of 35 months. The mean preoperative Oswestry Disability Index score was 55, decreasing to a mean of 16 postoperatively. The mean leg and back pain visual analog scale scores were 65 and 52, respectively, improving to means of 8 and 15. Reduction of the spondylolisthesis was achieved in all cases, with a mean decrease in forward translation of 76%. The authors conclude that MI-TLIF for symptomatic spondylolisthesis appears to be an effective surgical option with results that compare favorably to open procedures.

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Sangala Jaypal Reddy, Frank La Marca and Paul Park

Heat shock proteins (HSPs) are normal intracellular proteins that are produced in greater amounts when cells are subjected to stress or injury. These proteins have been shown to play a key role in the modulation of the secondary injury that occurs after the initial spinal cord injury (SCI). Heat shock proteins normally act as molecular chaperones and are called protein guardians because they act to repair partially damaged proteins. Normally intracellular, HSPs can also be liberated into the systemic circulation to act as important inflammatory mediators. In the setting of SCI, HSP induction has been shown to be beneficial. These proteins are liberated primarily by acutely stressed microglial, endothelial, and ependymal cells. Heat shock proteins have also been shown to assist in the protection of motor neurons and to prevent chronic inflammation after SCI. In animal models, several experimental drugs have shown neuroprotective effects in the spinal cord and appear to function by modulating HSPs.

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Alexander Vaccaro

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Sangala Jaypal Reddy, Wajd N. Al-Holou, Jean-Christophe Leveque, Frank La Marca and Paul Park

Primary traumatic facet dislocations are unusual in the lumbar spine. Most occurrences have been reported at the lumbosacral junction associated with anterior subluxation. The authors describe 2 cases in which a high impact trauma resulted in lateral subluxation with a unilateral locked facet involving the lumbar spine. In their review of the literature, the authors found no previously reported cases of this type of injury. Both cases described in this report involved significant spinal stenosis, neurological injury, and spinal instability. A posterior surgical approach, with at least partial resection of the locked facet joint in conjunction with pedicle screw fixation, allowed successful reduction and stabilization of the injury.

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Anthony C. Wang, Khoi D. Than, Arnold B. Etame, Frank La Marca and Paul Park

Object

Transcranial motor evoked potential (TcMEP) monitoring is frequently used in complex spinal surgeries to prevent neurological injury. Anesthesia, however, can significantly affect the reliability of TcMEP monitoring. Understanding the impact of various anesthetic agents on neurophysiological monitoring is therefore essential.

Methods

A literature search of the National Library of Medicine database was conducted to identify articles pertaining to anesthesia and TcMEP monitoring during spine surgery. Twenty studies were selected and reviewed.

Results

Inhalational anesthetics and neuromuscular blockade have been shown to limit the ability of TcMEP monitoring to detect significant changes. Hypothermia can also negatively affect monitoring. Opioids, however, have little influence on TcMEPs. Total intravenous anesthesia regimens can minimize the need for inhalational anesthetics.

Conclusions

In general, selecting the appropriate anesthetic regimen with maintenance of a stable concentration of inhalational or intravenous anesthetics optimizes TcMEP monitoring.

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Arnold B. Etame, Anthony C. Wang, Khoi D. Than, Frank La Marca and Paul Park

Object

Symptomatic cervical kyphosis can result from a variety of causes. Symptoms can include pain, neurological deficits, and functional limitation due to loss of horizontal gaze.

Methods

The authors review the long-term functional and radiographic outcomes following surgery for symptomatic cervical kyphosis by performing a PubMed database literature search.

Results

Fourteen retrospective studies involving a total of 399 patients were identified. Surgical intervention included ventral, dorsal, or circumferential approaches. Analysis of the degree of deformity correction and functional parameters demonstrated significant postsurgical improvement. Overall, patient satisfaction appeared high. Five studies reported mortality with rates ranging from 3.1 to 6.7%. Major medical complications after surgery were reported in 5 studies with rates ranging from 3.1 to 44.4%. The overall neurological complication rate was 13.5%.

Conclusions

Although complications are not insignificant, surgery appears to be an effective option when conservative measures fail to provide relief.

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Heesuk Kang, Paul Park, Frank La Marca, Scott J. Hollister and Chia-Ying Lin

Object

The goal of this study was to evaluate and compare load sharing of the facet and uncovertebral joints after total cervical disc arthroplasty using 3 different implant designs.

Methods

Three-dimensional voxel finite element models were built for the C5–6 spine unit based on CT images acquired from a candidate patient for cervical disc arthroplasty. Models of facet and uncovertebral joints were added and artificial discs were placed in the intervertebral disc space. Finite element analyses were conducted under normal physiological loads for flexion, extension, and lateral bending to evaluate von Mises stresses and strain energy density (SED) levels at the joints.

Results

The Bryan disc imposed the greatest average stress and SED levels at facet and uncovertebral joints with flexion-extension and lateral bending, while the ProDisc-C and Prestige LP discs transferred less load due to their rigid cores. However, all artificial discs showed increased loads at the joints in lateral bending, which may be attributed to direct impinging contact force.

Conclusions

In unconstrained/semiconstrained prostheses with different core rigidity, the shared loads at the joints differ, and greater flexibility may result in greater joint loads. With respect to the 3 artificial discs studied, load sharing of the Bryan disc was highest and was closest to normal load sharing with the facet and uncovertebral joints. The Prestige LP and ProDisc-C carried more load through their rigid core, resulting in decreased load transmission to the facet and uncovertebral joints.

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William R. Stetler Jr., Paul Park and Stephen Sullivan

Object

Tethering of the spinal cord has been a recognized cause of neurological symptoms in pediatric patients and is increasingly being recognized as a cause of symptoms in adults as well. The pathophysiology surrounding spinal cord tethering has begun to be understood in the pediatric population but is still unclear in adult patients.

Methods

Using a PubMed database literature search, the authors reviewed the pathology and pathophysiology surrounding the tethered spinal cord, focusing particularly on the pathophysiology of adult tethered cord syndrome (TCS).

Results

Experimental data obtained in pediatric patients at surgery and in animal models indicate that spinal cord tethering causes a reduction in spinal cord blood flow and dysfunction of neuronal mitochondrial terminal oxidase. Retrospective analyses of patients undergoing surgery for adult TCS show that many adults developed symptoms following an event that could stretch the spinal cord, while others did not. Many patients also were found to have structural lesions in addition to a tethered spinal cord at diagnosis.

Conclusions

Both adult and pediatric TCSs are likely the result of a relative lack of blood flow to the spinal cord, causing dysfunction in mitochondrial oxidative phosphorylation. The likely reason the syndrome present later and differently in adults is that a secondary threshold of tension or a cumulative effect of repetitive, transient tension is placed on the cord before symptoms are recognized.