Papers by G. Bryan Cornwall, PhD
The safety and efficacy of a resorbable plate and screw implant system for preventing the disloca... more The safety and efficacy of a resorbable plate and screw implant system for preventing the dislocation of autologous tricortical iliac crest graft material in a cervical spine model without additional metallic fixation were evaluated. The resorbable polymer implants were fabricated using an amorphous copolymer, sterilized by e-beam irradiation. A total of 13 adult, female ewes were used in the study. A total of 58 radiographs of the implants were evaluated over 12 month survival period. No displacement of the graft material and implant failure were observed. Biomechanical evaluation demonstrated a significant reduction in motion in all three planes of motion at the survival periods
Spine, 2020
STUDY DESIGN Experimental in-vivo animal study. OBJECTIVE The aim of this study was to evaluate a... more STUDY DESIGN Experimental in-vivo animal study. OBJECTIVE The aim of this study was to evaluate an Artificial Intelligence (AI)-enabled ultrasound imaging system's ability to detect, segment, classify, and display neural and other structures during trans-psoas spine surgery. SUMMARY OF BACKGROUND DATA Current methodologies for intraoperatively localizing and visualizing neural structures within the psoas are limited and can impact the safety of lateral lumbar interbody fusion (LLIF). Ultrasound technology, enhanced with AI-derived neural detection algorithms, could prove useful for this task. METHODS The study was conducted using an in vivo porcine model (50 subjects). Image processing and machine learning algorithms were developed to detect neural and other anatomic structures within and adjacent to the psoas muscle while using an ultrasound imaging system during lateral lumbar spine surgery (SonoVision,™ Tissue Differentiation Intelligence, USA). The imaging system's ability to detect and classify the anatomic structures was assessed with subsequent tissue dissection. Dice coefficients were calculated to quantify the performance of the image segmentation. RESULTS The AI-trained ultrasound system detected, segmented, classified, and displayed nerve, psoas muscle, and vertebral body surface with high sensitivity and specificity. The mean Dice coefficient score for each tissue type was >80%, indicating that the detected region and ground truth were >80% similar to each other. The mean specificity of nerve detection was 92%; for bone and muscle, it was >95%. The accuracy of nerve detection was >95%. CONCLUSION This study demonstrates that a combination of AI-derived image processing and machine learning algorithms can be developed to enable real-time ultrasonic detection, segmentation, classification, and display of critical anatomic structures, including neural tissue, during spine surgery. AI-enhanced ultrasound imaging can provide a visual map of important anatomy in and adjacent to the psoas, thereby providing the surgeon with critical information intended to increase the safety of LLIF surgery.Level of Evidence: N/A.
Orthopedics, 2002
Titanium lumbar interbody spinal fusion devices are reported to be 90% effective for single-level... more Titanium lumbar interbody spinal fusion devices are reported to be 90% effective for single-level lumbar interbody fusion, although radiographic determination of fusion has been debated. Using blinded radiographic, biomechanic, histologic, and statistical measures, researchers in the present study evaluated a radiolucent 70/30 poly(L-lactide-co-D,L-lactide) (70/30 D,L-PLa) interbody fusion device packed with autograft or rhBMP-2 on a collagen sponge in 25 sheep at 3, 6, 12, 18, and 24 months. A trend of increased fusion stiffness, radiographic fusion, and histologic fusion was demonstrated from 3 months to 24 months. Device degradation was associated with a mild to moderate chronic inflammatory response at all postoperative sacrifice times.
Frontiers in Surgery, 2020
Spine surgery (lumbar, cervical, deformity, and entire spine) has increased in volume and improve... more Spine surgery (lumbar, cervical, deformity, and entire spine) has increased in volume and improved in outcomes over the past 50 years because of innovations in surgical techniques and introduction of new technologies to improve patient care. Innovation is described as a process to add value or create change in an enterprise's economic or social potential. This mini review will assess two of three assessments of innovation in spine surgery: scientific publications and patents issued. The review of both scientific publications and issued patents is a unique assessment. The third assessment of innovation: regulatory clearances of medical devices and equipment for spine surgery and their evolution over time, will also be discussed.
2019 ASEE Annual Conference & Exposition Proceedings
Diego (USD) Shiley-Marcos School of Engineering.Dr. Cornwall's academic background includes a Bac... more Diego (USD) Shiley-Marcos School of Engineering.Dr. Cornwall's academic background includes a Bachelor of Applied Science in mechanical engineering, a Master of Applied Science in material science, and a PhD in mechanical engineering, specializing in Orthopaedic Biomechanics from Queen's University in Kingston, Ontario, Canada. He is registered as a Professional Engineer.
International Journal of Spine Surgery, 2015
Background Expandable cages are gaining popularity in anterior reconstruction of the thoracolumba... more Background Expandable cages are gaining popularity in anterior reconstruction of the thoracolumbar spine following corpectomy as they can provide adjustable distraction and deformity correction. Rectangular, rather than circular, endcaps provide increased resistance to subsidence by spanning the apophyseal ring; however their impact on construct stability is not known. The objective of this study was to investigate the contribution of expandable corpectomy cage endcap shape (round vs. rectangular) and fixation method (anterior plate vs. posterior pedicle screws) to the stability of an L1 sub-total corpectomy construct. Methods Eight fresh-frozen cadaveric specimens (T11-L3) were subjected to multi-directional flexibility testing to 6 N•m with a custom spine simulator. Test conditions were: intact, L1 sub-total corpectomy defect, expandable cage (round endcap) alone, expandable cage (round endcap) with anterior plate, expandable cage (round endcap) with bilateral pedicle screws, expandable cage (rectangular endcap) alone, expandable cage (rectangular endcap) with anterior plate, expandable cage (rectangular endcap) with bilateral pedicle screws. Range-of-motion across T12-L2 was measured with an optoelectronic system. Results The expandable cage alone with either endcap provided significant stability to the corpectomy defect, reducing motion to intact levels in flexion-extension with both endcap types, and in lateral bending with rectangular endcaps. Round endcaps allowed greater motion than intact in lateral bending, and axial rotation ROM was greater than intact for both endcaps. Supplemental fixation provided the most rigid constructs, although there were no significant differences between instrumentation or endcap types. Conclusions These results suggest anterior-only fixation may be adequate when using an expandable cage in a sub-total corpectomy application and choice of endcap type may be driven by other factors such as subsidence resistance.
Motion Preservation Surgery of the Spine, 2008
Spine, 2014
In vitro cadaveric biomechanical study of lateral interbody cages and supplemental fixation in a ... more In vitro cadaveric biomechanical study of lateral interbody cages and supplemental fixation in a degenerative spondylolisthesis (DS) model. To investigate changes in shear and flexion-extension stability of lateral interbody fusion constructs. Instability associated with DS may increase postoperative treatment complications. Several groups have investigated DS in cadaveric spines. Extreme lateral interbody fusion (XLIF) cages with supplemental fixation have not previously been examined using a DS model. Seven human cadaveric L4-L5 motion segments were evaluated using flexion-extension moments to ±7.5 N·m and anterior-posterior (A-P) shear loading of 150 N with a static axial compressive load of 300 N. Conditions were: (1) intact segment, (2) DS simulation with facet resection and lateral discectomy, (3) standalone XLIF cage, (4) XLIF cage with (1) lateral plate, (2) lateral plate and unilateral pedicle screws contralateral to the plate (PS), (3) unilateral PS, (4) bilateral PS, (5) ...
Clinics in plastic surgery, 2004
Resorbable polymer implants have become a compelling option in the treatment of acquired and cong... more Resorbable polymer implants have become a compelling option in the treatment of acquired and congenital craniofacial deformities. The resorbable polylactide (PLa) and polyglycolide (PGa) polymers in particular have demonstrated excellent safety profile sin multiple in vitro, animal, and clinical studies and are currently being used in a wide variety of craniofacial applications. In this article, the authors discuss the biomaterial properties of PLa and PGa resorbable implants and provide an overview of the use of these polymers in craniofacial surgery. They conclude by relating their experience with an ongoing clinical series using MacroPore PLDLa and FRP implants for various applications,including Le Fort osteotomies, midface/monobloc internal distraction, and craniosynostosis reconstruction.
Journal of Applied Biomaterials, 1995
A quantitative method of reporting surface degradation of the ultra-high molecular weight polyeth... more A quantitative method of reporting surface degradation of the ultra-high molecular weight polyethylene (UHMWPE) tibial component from retrieved total knee replacements (TKR) was developed. Specific features include a qualitative assessment expressing the patterns in which the damage was detected as well as a quantitative summary of the observed degradation mechanisms. In addition, a method of measuring lower limb alignment changes with time is described and related to the observed damage patterns. Two case studies are presented. One case illustrated that changes in alignment resulted from factors other than wear. The damage observed on the tibial plateau appeared to occur subsequent to the changes in alignment. The second case illustrated that the wear of the UHMWPE tibial insert lead to the changes in the overall lower limb alignment. The methods described provide additional information regarding TKR failure mechanisms compared to reporting methods currently available. In particular, the collection of temporal alignment data at clinical follow-up visits enhanced the assessment of the retrieved TKR.
Motion Preservation Surgery of the Spine, 2008
The Spine Journal, 2004
There was no case of implants breakage, but mild anterior migration of mesh was noted in 2 patien... more There was no case of implants breakage, but mild anterior migration of mesh was noted in 2 patients who were not fixed with posteior pedicle screws. Nonunion of graft was not experienced. Preoperative Frankel grades were B in 1 patient, C in 3, D in 4, and E in 9. At final follow-up, 11 of 17 patients were recovered completely to Frankel E and only two patients showed D. CONCLUSIONS: Stabilizing the spine with pedicle screws and titanium mesh in tubercuous spondylitis effectively prevented development of kyphotic deformity and provided immediate postoperative ambulation. Metallic implants did not prohibit control of infection when combined with radical debridement and anti-tuberculous chemotherapy.
Spine, 2010
Study Design. Biomechanical study and the review of literature on lumbar interbody fusion constru... more Study Design. Biomechanical study and the review of literature on lumbar interbody fusion constructs. Objective. To demonstrate the comparative stabilizing effects of lateral interbody fusion with various supplemental internal fixation options. Summary of Background Data. Lumbar interbody fusion procedures are regularly performed using anterior, posterior, and more recently, lateral approaches. The biomechanical profile of each is determined by the extent of resection of local supportive structures, implant size and orientation, and the type of supplemental internal fixation used. Methods. Pure moment flexibility testing was performed using a custom-built 6 degree-of-freedom system to apply a moment of Ϯ7.5 Nm in each motion plane, while motion segment kinematics were evaluated using an optoelectronic motion system. Constructs tested included the intact spine, stand-alone extreme lateral interbody implant, interbody implant with lateral plate, unilateral and bilateral pedicle screw fixation. These results were evaluated against those from literature-reported biomechanical studies of other lumbar interbody constructs. Results. All conditions demonstrated a statistically significant reduction in range of motion (ROM) as a percentage of intact. In flexion-extension, ROM was 31.6% standalone, 32.5% lateral fixation, and 20.4% and 13.0% unilateral and bilateral pedicle screw fixation, respectively. In lateral bending, the trend was similar with greater reduction with lateral fixation than in flexion-extension; ROM was 32.5% stand-alone, 15.9% lateral fixation, and 21.6% and 14.4% unilateral and bilateral pedicle screw fixation. ROM was greatest in axial rotation; 69.4% stand-alone, 53.4% lateral fixation, and 51.3% and 41.7% unilateral and bilateral pedicle screw fixation, respectively. Conclusion. The extreme lateral interbody construct provided the largest stand-alone reduction in ROM compared with literature-reported ALIF and TLIF constructs. Supplemental bilateral pedicle screw-based fixation provided the overall greatest reduction in ROM, similar among all interbody approach techniques. Lateral fixation and unilateral pedicle screw fixation provided intermediate reductions in ROM. Clinically, surgeons may evaluate these comparative results to choose fixation options commensurate with the stability requirements of individual patients.
Proceedings of the Institution of Mechanical Engineers, Part H: Journal of Engineering in Medicine, 2001
It is known that wear mechanisms differ between the ultra-high molecular weight polyethylene (UHM... more It is known that wear mechanisms differ between the ultra-high molecular weight polyethylene (UHMWPE) components of total hip replacement (THR) and total knee replacement (TKR). The difference in relative contact position or ‘kinematic conditions of contact’ between the metal and polymer components is thought to contribute to the contrast in observed wear mechanisms.A reciprocating wear tester was used to evaluate three basic kinematic contact conditions: sliding, in which the relative contact position on the polymer remains stationary; gliding, where the contact position on the polymer reciprocates; and rolling, where the contact position on the polymer varies and the relative velocities of both components are equal.All static load tests used cast Co—Cr alloy and irradiated Chirulen®UHMWPE in a 37 °C environment lubricated with bovine serum albumin. UHMWPE test sample wear was measured gravi-metrically at intervals of 600000 cycles. The results indicated a difference in wear factor...
Neurosurgical Focus, 2004
Object An in vivo study was conducted in an ovine model to investigate the biomechanical changes ... more Object An in vivo study was conducted in an ovine model to investigate the biomechanical changes after the animals underwent single-level anterior cervical discectomy followed by fusion in which autologous tricortical graft was used and implantation of cervical plates for which bioresorbable polymer screws and plates were used. The specific aims of the study were to evaluate whether implant failure or screw backout would occur over time and to measure the change in stiffness at the treated level at various postoperative time periods (3, 6, and 12 months). Methods A total of 58 x-ray films were evaluated over the 12-month survival period. No screw breakage or displacement was observed in any animal during the temporal radiographic analysis. Radiographically confirmed fusion appeared to be complete at all time periods longer than 6 months. The biomechanical testing demonstrated dramatic reductions in range of motion at the fusion level in the animals allowed to survive for 6 and 12 mo...
Neurosurgical Focus, 2004
Object The purpose of this study was to evaluate the performance of a resorbable polylactide film... more Object The purpose of this study was to evaluate the performance of a resorbable polylactide film in the sheep posterior spine in the presence of a combined laminectomy and durotomy defect. Methods A resorbable polylactide film was used to cover the combined defects in the eight sheep used in this study. Two surgical levels were performed in each animal, with randomly assigned control and treated sites. Each surgical level consisted of a full laminectomy followed by a needle-induced durotomy. The treated levels received a resorbable polylactide film cut to size and tucked in under the laminar defect. At 8 to 10 weeks postoperatively, results of myelography and visual dye infiltration showed complete healing of the durotomies for all sites. In addition, evaluation of gross dissection based on volume and tenacity scores as well as histological findings indicates decreased posterior dural adhesions for sites treated with resorbable polylactide film. Conclusions The results of this inve...
Journal of Neurosurgery: Spine, 2012
Object Traditional posterior pedicle screw fixation is well established as the standard for spina... more Object Traditional posterior pedicle screw fixation is well established as the standard for spinal stabilization following posterior or posterolateral lumbar fusion. In patients with lumbar spinal stenosis requiring segmental posterior instrumented fusion and decompression, interlaminar lumbar instrumented fusion (ILIF) is a potentially less invasive alternative with reduced morbidity and includes direct decompression assisted by an interlaminar allograft spacer stabilized by a spinous process plate. To date, there has been no biomechanical study on this technique. In the present study the biomechanical properties of the ILIF construct were evaluated using an in vitro cadaveric biomechanical analysis, and the results are presented in comparison with other posterior fixation techniques. Methods Eight L1–5 cadaveric specimens were subjected to nondestructive multidirectional testing. After testing the intact spine, the following conditions were evaluated at L3–4: bilateral pedicle scr...
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Papers by G. Bryan Cornwall, PhD