A Repeatable Ex Vivo Model of Spondylolysis and Spondylolisthesis

Beadon, K; Johnston, James D.; Siggers, Kevin; Itshayek, Eyal; Cripton, Peter A.

doi:10.1097/brs.0b013e318184e775

Cited by 16 publications

(10 citation statements)

References 34 publications

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“…In addition, laminectomy as well as removal of posterior elements substantially reduces spinal strength in shear loading [11, 19, 20]. In vitro experiments have also shown that shear loading can lead to bony failure of the posterior elements of the spine, with fracturing of the pars interarticularis most often reported [1]. Therefore, it is quite likely that decreased resistance to shear loading after laminectomy plays a crucial role in the incidence of postoperative complications, i.e.…”

Section: Introductionmentioning

confidence: 99%

The impact of bone mineral density and disc degeneration on shear strength and stiffness of the lumbar spine following laminectomy

et al. 2011

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PurposeLaminectomy is a standard surgical procedure for elderly patients with symptomatic degenerative lumbar stenosis. The procedure aims at decompression of the affected nerves, but it also causes a reduction of spinal shear strength and shear stiffness. The magnitude of this reduction and the influence of bone mineral density (BMD) and disc degeneration are unknown. We studied the influence of laminectomy, BMD, and disc degeneration on shear force to failure (SFF) and shear stiffness (SS).MethodsTen human cadaveric lumbar spines were obtained (mean age 72.1 years, range 53–89 years). Laminectomy was performed either on L2 or L4, equally divided within the group of ten spines. BMD was assessed by dual X-ray absorptiometry (DXA). Low BMD was defined as a BMD value below the median. Intervertebral discs were assessed for degeneration by MRI (Pfirrmann) and scaled in mild and severe degeneration groups. Motion segments L2–L3 and L4–L5 were isolated from each spine. SFF and SS were measured, while loading simultaneously with 1,600 N axial compression.ResultsLow BMD had a significant negative effect on SFF. In addition, a significant interaction between low BMD and laminectomy was found. In the high BMD group, SFF was 2,482 N (range 1,678–3,284) and decreased to 1,371 N (range 940–1,886) after laminectomy. In the low BMD group, SFF was 1,339 N (range 909–1,628) and decreased to 761 N (range 561–1,221). Disc degeneration did not affect SFF, nor did it interact with laminectomy. Neither low BMD nor the interaction of low BMD and laminectomy did affect SS. Degeneration and its interaction with laminectomy did not significantly affect SS.ConclusionsIn conclusion, low BMD significantly decreased SFF before and after lumbar laminectomy. Therefore, DXA assessment may be an important asset to preoperative screening. Lumbar disc degeneration did not affect shear properties of lumbar segments before or after laminectomy.

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Section: Introductionmentioning

confidence: 99%

The impact of bone mineral density and disc degeneration on shear strength and stiffness of the lumbar spine following laminectomy

et al. 2011

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“…Several in vitro studies of isolated human lumbar and porcine cervical FSUs have consistently demonstrated that the predominant injury occurring from shear loading is a bilateral fracture of the cranial vertebra's pars interarticularis (Cripton et al 1995;van Dieën et al 2006;Beadon et al 2008;Gallagher et al 2010;Howarth and Callaghan 2012). One early study had found that pars interarticularis fractures were initiated at the anterior-caudal aspect when forces were directly applied to the facet of an isolated vertebra (Cyron et al 1976).…”

Section: Computer Methods In Biomechanics and Biomedical Engineering 551mentioning

confidence: 97%

“…Previous in vitro studies have clearly shown that the pars interarticularis is the primary site of vertebral failure under acute (Cyron et al 1976;Cripton et al 1995;van Dieën et al 2006;Gallagher et al 2010;Howarth and Callaghan 2012) as well as repetitive shear loading (Cyron and Hutton 1978;Beadon et al 2008). The proposed mechanism for this fracture is a bending moment generated about the pars interarticularis caused by contact between the articulating inferior and superior facets of the vertebral joint's respective cranial and caudal vertebrae (Cyron and Hutton 1978;.…”

Section: Introductionmentioning

confidence: 94%

A finite element evaluation of the moment arm hypothesis for altered vertebral shear failure force

Howarth

Karakolis

Callaghan

2013

Computer Methods in Biomechanics and Biomedical Engineering

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The mechanism of vertebral shear failure is likely a bending moment generated about the pars interarticularis by facet contact, and the moment arm length (MAL) between the centroid of facet contact and the location of pars interarticularis failure has been hypothesised to be an influential modulator of shear failure force. To quantitatively evaluate this hypothesis, anterior shear of C3 over C4 was simulated in a finite element model of the porcine C3-C4 vertebral joint with each combination of five compressive force magnitudes (0-60% of estimated compressive failure force) and three postures (flexed, neutral and extended). Bilateral locations of peak stress within C3's pars interarticularis were identified along with the centroids of contact force on the inferior facets. These measurements were used to calculate the MAL of facet contact force. Changes in MAL were also related to shear failure forces measured from similar in vitro tests. Flexed and extended vertebral postures respectively increased and decreased the MAL by 6.6% and 4.8%. The MAL decreased by only 2.6% from the smallest to the largest compressive force. Furthermore, altered MAL explained 70% of the variance in measured shear failure force from comparable in vitro testing with larger MALs being associated with lower shear failure forces. Our results confirmed that the MAL is indeed a significant modulator of vertebral shear failure force. Considering spine flexion is necessary when assessing low-back shear injury potential because of the association between altered facet articulation and lower vertebral shear failure tolerance.

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“…In the skeletally immature athlete, this problem is caused by repetitive flexion, extension shear, and cyclic loading of the lumbar spine 31,32 and is more common in sports such as ballet, gymnastics, figure skating, football, and diving. This injury more commonly occurs in the lumbar spine at L5.…”

Section: Posterior Spine Injuries Spondylolysismentioning

confidence: 99%

Back Pain in Adolescent Athletes

Young

d’Hemecourt

2011

The Physician and Sportsmedicine

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Back pain in the young athlete is a common complaint and often perceived as a challenging problem. A well-directed approach will usually provide the practitioner with a higher comfort zone. The etiology of back pain in the pediatric and adolescent population is different from that of the adult population due to the presence of open physes and increased linear growth velocity. In addition, the frequency and intensity of sports participation in children continues to increase, leading to more overuse injuries. This review article will discuss the anatomy and physiology of the spine and pelvis, as well as focus on the chronic and overuse causes of back pain in the young athlete.

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A Repeatable Ex Vivo Model of Spondylolysis and Spondylolisthesis

Abstract: Cyclic shear loading with intermittent impulse loads can reliably create fracture in the pars interarticularis in ex vivo porcine spine segments. Subsequent cyclic anterior motion of the superior vertebra results in clinically-relevant spondylolysis and spondylolisthesis.

Cited by 16 publications

References 34 publications

The impact of bone mineral density and disc degeneration on shear strength and stiffness of the lumbar spine following laminectomy

The impact of bone mineral density and disc degeneration on shear strength and stiffness of the lumbar spine following laminectomy

A finite element evaluation of the moment arm hypothesis for altered vertebral shear failure force

Back Pain in Adolescent Athletes

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