Biomedical subjects

Philip S Yuan

Publications and source records attributed to Philip S Yuan.

8 recordsLinked to original sources

PubMed2006

An evaluation of image-guided technologies in the placement of percutaneous iliosacral screws.

STUDY DESIGN: A surgical simulation study in human cadaver spine specimens was conducted to evaluate the accuracy of 3 different surgical navigation systems compared to standard fluoroscopy in the percutaneous placement of iliosacral screws. OBJECTIVES: To compare the accuracy of percutaneous iliosacral screw placement using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance (Medtronic Surgical Navigation Technologies, Louisville, CO), and electromagnetic fluoroscopic image guidance. SUMMARY OF BACKGROUND DATA: Conventional percutaneous sacroiliac screw placement has a malposition rate as high as 15%, as reported in the English-speaking literature (Hinsche et al [Clin Orthop Relat Res 2002;395:135-44] and Templeman et al [Clin Orthop Relat Res 1996;329:194-8]). Iso-C3D and computer-assisted image guidance technologies have been proposed to increase this accuracy rate. METHODS: Two iliosacral screws were placed bilaterally (4 screws) in each of 4 cadavers using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance, and electromagnetic fluoroscopic image guidance. Screw positions were analyzed by computerized tomography after instrumentation and assigned a score based on deviation from ideal screw position. RESULTS: The StealthStation with FluoroNav (Medtronic Surgical Navigation Technologies) appeared to provide the highest accuracy of all guidance techniques. This result was more accurate than standard fluoroscopy. CONCLUSIONS: Computer-assisted fluoroscopy based image navigation appears to be more accurate than standard fluoroscopy in placing these screws. However, errors may occur with all techniques. Further refinement in registration procedures may highly improve the accuracy of percutaneous screw placement in a variety of spinopelvic procedures.

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PubMed2006

The use of computerized image guidance in lumbar disk arthroplasty.

OBJECTIVES: Surgical navigation systems have been increasingly studied and applied in the application of spinal instrumentation. Successful disk arthroplasty requires accurate midline and rotational positioning for optimal function and longevity. A surgical simulation study in human cadaver specimens was done to evaluate and compare the accuracy of standard fluoroscopy, computer-assisted fluoroscopic image guidance, and Iso-C3D image guidance in the placement of lumbar intervertebral disk replacements. METHODS: Lumbar intervertebral disk prostheses were placed using three different image guidance techniques in three human cadaver spine specimens at multiple levels. Postinstrumentation accuracy was assessed with thin-cut computed tomography scans. RESULTS: Intervertebral disk replacements placed using the StealthStation with Iso-C3D were more accurately centered than those placed using the StealthStation with FluoroNav and standard fluoroscopy. Intervertebral disk replacements placed with Iso-C3D and FluoroNav had improved rotational divergence compared with standard fluoroscopy. Iso-C3D and FluoroNav had a smaller interprocedure variance than standard fluoroscopy. These results did not approach statistical significance. Relative to both virtual and standard fluoroscopy, use of the StealthStation with Iso-C3D resulted in improved accuracy in centering the lumbar disk prosthesis in the coronal midline. CONCLUSIONS: The StealthStation with FluoroNav appears to be at least equivalent to standard fluoroscopy and may offer improved accuracy with rotational alignment while minimizing radiation exposure to the surgeon. Surgical guidance systems may offer improved accuracy and less interprocedure variation in the placement of intervertebral disk replacements than standard fluoroscopy. Further study regarding surgical navigation systems for intervertebral disk replacement is warranted.

Aged↗

PubMed2006

Anatomy of the percutaneous presacral space for a novel fusion technique.

OBJECTIVES: Lumbar fusion has been widely used to treat unstable spinal disorders. Methods are evolving from open procedures to less invasive methods to avoid soft tissue trauma. Recently, a soft tissue sparing method to access the axial lumbosacral spine has been developed. It is crucial to determine structures potentially at risk for injury during this fusion technique. The anatomy of the presacral space and safety of the paracoccygeal approach were evaluated through cadaveric dissection and radiographic studies. The objective was to evaluate the safety of a paracoccygeal approach to the axial lumbosacral spine and determine structures that could potentially be injured. METHODS: The paracoccygeal approach was performed on two cadavers, followed by dissection. Distances from the midline trajectory of the approach to surrounding vascular structures were determined. Similar distances were also measured on computed tomography (CT) and magnetic resonance imaging (MRI) of 12 patients, as well as CT images of two additional patients. A "safe zone" was determined using the sagittal length of the presacral space and the distance between the most medial internal iliac vessel on the right and left, respectively. RESULTS: The coronal safe zone averaged 6.9 and 6.0 cm on MRI and CT, respectively. The mean distance from the anterior sacral margin to the rectum at the S3-S4 level was 1.2 and 1.3 cm on MRI and CT, respectively. CONCLUSION: In this study, we defined the "coronal safe zone" within the presacral space. This "safe zone" may guide surgeons when utilizing the percutaneous paracoccygeal approach.

Cadaver↗

PubMed2005

An evaluation of image-guided technologies in the placement of anterior thoracic vertebral body screws in spinal trauma: a cadaver study.

BACKGROUND: Image guidance provides additional anatomic information to the surgeon, which may allow more accurate insertion of spinal implants. Imprecise placement of anterior thoracic screws places the spinal cord and paraspinal structures at risk for injury. Image guidance may afford a safety benefit to patients when anterior thoracic screws are required in the setting of spinal stabilization after trauma. OBJECTIVES: To compare the accuracy of anterior thoracic screw placement using standard fluoroscopy, computer-assisted fluoroscopic image guidance, Iso-C3D image guidance, and electromagnetic fluoroscopic image guidance. STUDY DESIGN: A surgical simulation study in human cadaver spine specimens. METHODS: After an open thoracotomy approach, anterior thoracic screws were placed by experienced spine surgeons using 4 different image-guided techniques in 4 human cadaver thoracic spines. Screws were placed in the 9th, 10th, and 11th thoracic vertebrae of each specimen. The specimens were then examined with thin-cut computed tomography (CT) scans, and with sagittal and coronal reconstructions. Measurements included the distance of the screw from the spinal canal, the angle of the screw path in relation to a perpendicular to a line that bisects the spinous process, and the angle of screw divergence from the superior endplate. RESULTS: There was no evidence of spinal canal penetrance with any of the image-guided techniques used to place anterior thoracic vertebral body screws. Screws inserted with standard fluoroscopy tended to aim anterolaterally by 18 degrees. The image-guidance systems allowed more accurate placement of anterior thoracic screws in the transverse plane compared with standard fluoroscopy. There was no statistically significant difference in coronal plane screw angulation (angle of divergence with the superior endplate) between any of the imaging methods. CONCLUSIONS: Spinal image-guidance systems may allow spine surgeons to place anterior thoracic screws more precisely, particularly in the axial plane. The improved accuracy of spinal implant insertion could ultimately provide a benefit to patient safety, especially in the setting of malaligned vertebral bodies after trauma.

Aged↗

PubMed2005

Nonsurgical and surgical management of lumbar spinal stenosis.

The symptoms associated with lumbar spinal stenosis can decrease quality of life and may cause patients to seek treatment. Except in rare cases of rapid neurologic progression or cauda equina syndrome, nonsurgical modalities should be the initial treatment choice. Activity modification, a variety of medications, epidural steroid injections, and other methods are recommended for pain reduction. A formal physical therapy program, which focuses on flexion-based exercises, may lead to improved patientfunction. Surgery is indicated in patients who remain symptomatic despite a course of nonsurgical therapy and who have advanced imaging studies that correspond to existing .symptoms. Adequate decompression of the neural elements and maintenance of bony stability are necessary for a good surgical outcome for patients with spinal stenosis. Laminectomy has long been the method of choice for thorough lumbar decompression. Preserving at least the lateral half of the facet joints bilaterally and bone in the area of the pars interarticularis minimizes the potential for iatrogenic instability. Numerous other decompression techniques have been described, including multilevel laminotomies, fenestration, distraction laminoplasty, and microscopic decompression. Arthrodesis, either with or without instrumentation, is also indicated in some patients. Several studies report that surgical treatment produces better outcomes than nonsurgical treatment in the short term; however, the results tend to deteriorate with time. Lumbar decompressive surgery can be complicated by epidural hematoma, deep venous thrombosis, dural tear, infection, nerve root injury, and recurrence of symptoms.

Decompression, Surgical↗

PubMed2003

Asynchronous functional, cellular and transcriptional changes after a bout of eccentric exercise in the rat.

Thirty eccentric contractions (ECs) were imposed upon rat dorsiflexors (n = 46) by activating the peroneal nerve and plantarflexing the foot ~40 deg, corresponding to a sarcomere length change over the range 2.27-2.39 microm for the tibialis anterior and 2.52-2.66 microm for the extensor digitorum longus. Animals were allowed to recover for one of 10 time periods ranging from 0.5 to 240 h, at which time muscle contractile properties, immunohistochemical labelling and gene expression were measured. Peak isometric torque dropped significantly by ~40 % from an initial level of 0.0530 +/- 0.0009 Nm to 0.0298 +/- 0.0008 Nm (P < 0.0001) immediately after EC, and then recovered in a linear fashion to control levels 168 h later. Immunohistochemical labelling of cellular proteins revealed a generally asynchronous sequence of events at the cellular level, with the earliest event measured being loss of immunostaining for the intermediate filament protein, desmin. Soon after the first signs of desmin loss, infiltration of inflammatory cells occurred, followed by a transient increase in membrane permeability, manifested as inclusion of plasma fibronectin. The quantitative polymerase chain reaction (QPCR) was used to measure transcript levels of desmin, vimentin, embryonic myosin heavy chain (MHC), myostatin, myoD and myogenin. Compared to control levels, myostatin transcripts were significantly elevated after only 0.5 h, myogenic regulatory factors significantly elevated after 3 h and desmin transcripts were significantly increased 12 h after EC. None of the measured parameters provide a mechanistic explanation for muscle force loss after EC. Future studies are required to investigate whether there is a causal relationship among desmin loss, increased cellular permeability, upregulation of the myoD and desmin genes, and, ultimately, an increase in the desmin content per sarcomere of the muscle.

Animals↗

PubMedDate not supplied

Nucleus pulposus replacement: an emerging technology.

Debilitating low back pain as a result of symptomatic lumbar disc degeneration places a significant burden on an industrial society. Traditionally surgical treatment involving fusion of the anterior and posterior spinal elements has resulted in unpredictable and frequently irreproducible results, especially with regard to return to work rates. A new surgical method of managing symptomatic disc degeneration recalcitrant to nonoperative measures involves the partial or complete removal of the intervertebral disc with replacement with a motion-sparing device. A review of the English-speaking literature will be discussed evaluating the historical development, design considerations, animal models, basic science studies, cadaveric research, and clinical outcomes of the partial removal of the intervertebral disc (nucleus pulposus) and replacement with a motion-sparing implant. An overview of traditional methods of surgical management of lumbar degenerative disc disease will then be followed by an introduction to the concept of motion-sparing implants (nucleus pulposus replacement) intended to remove the pain generator without the associated morbidity of a surgical fusion.

Biocompatible Materials↗

PubMedDate not supplied

Compartment syndrome following intramedullary fixation of pediatric forearm fractures.

This study was designed to evaluate the incidence of compartment syndrome (CS) resulting from the treatment of both-bone forearm fractures in children. A retrospective analysis of 285 consecutive children who presented with both-bone forearm fractures was performed. Of 235 closed injuries, 205 were treated with closed reduction and casting; none of these patients developed CS. Thirty of the closed injuries were treated with closed reduction and intramedullary fixation; three of these patients (10%) developed CS. Fifty patients sustained open fractures and were treated with debridement and open reduction with intramedullary pinning; CS developed in three of these patients (6%). The eighty patients treated with intramedullary fixation had an increased incidence of CS compared with the 205 patients treated with closed reduction and casting (P < 0.001). Within the group of patients who had surgery, patients with longer operative times and more use of intraoperative fluoroscopy were at higher risk of developing CS.

Adolescent↗