The effect of an interspinous process implant on facet loading during extension

Facet loading parameters of lumbar cadaver spines were measured during extension before and after placement of an interspinous process implant. The study was undertaken to quantify the influence of an interspinous implant on facet loading at the implanted and adjacent levels during extension. Facet...

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Bibliographic Details
Published in:	Spine (Philadelphia, Pa. 1976) Vol. 30; no. 8; pp. 903 - 907
Main Authors:	WISEMAN, Craig M, LINDSEY, Derek P, FREDRICK, Amy D, YERBY, Scott A
Format:	Journal Article
Language:	English
Published:	Philadelphia, PA Lippincott 15-04-2005 Hagerstown, MD
Subjects:	Biological and medical sciences Cadaver Cerebrospinal fluid. Meninges. Spinal cord Endocrinopathies Equipment Design Humans Hypothalamus. Hypophysis. Epiphysis (diseases) Lumbar Vertebrae - physiopathology Lumbar Vertebrae - surgery Medical sciences Movement Nervous system (semeiology, syndromes) Neurology Neuropharmacology Neuroprotective agent Non tumoral diseases. Target tissue resistance. Benign neoplasms Pharmacology. Drug treatments Pressure Prostheses and Implants Weight-Bearing lumbar Nervous system diseases Vertebral canal Implant Lumbar spine Low back pain Diseases of the osteoarticular system Spine disease Joint neurogenic intermittent claudication interspinous process decompression Osteoarticular system Pain back pain Dorsalgia Intermittent Central nervous system disease Rachialgia Dorsal spine facet joint Spinal cord disease Facet
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Summary:	Facet loading parameters of lumbar cadaver spines were measured during extension before and after placement of an interspinous process implant. The study was undertaken to quantify the influence of an interspinous implant on facet loading at the implanted and adjacent levels during extension. Facet loading is increased during extension and decreased during flexion. Previous studies have demonstrated that interspinous process decompression relieves disc pressure at the implanted level and does not alter disc pressure at the adjacent levels. Facet joints are believed to play a key role in back pain, especially in patients with collapsed discs and increased motion segment mobility resulting in increased facet loading. Seven cadaver spines (L2-L5) were loaded to 15 Nm of extension and 700 N compression with and without an interspinous process implant (X STOP) placed between the L3-L4 spinous processes. Pressure-sensitive film was placed in the facet joints of the implanted and adjacent levels. After loading, the film was digitally analyzed for peak pressure, average pressure, contact area, and force. These values were compared between the intact and implanted specimens at the adjacent and implanted levels using a paired t test (P < 0.05). The implant significantly reduced the mean peak pressure, average pressure, contact area, and force at the implanted level. The mean peak pressure, average pressure, contact area, and force at the adjacent levels were not significantly different between the intact and implanted specimens with the exception of contact area at the L2-L3 level. Interspinous process decompression will unlikely cause adjacent level facet pain or accelerated facet joint degeneration. Furthermore, pain induced from pressure originating in the facets and/or posterior anulus of the lumbar spine may be relieved by interspinous pro-cess decompression. Clinical results from patients with a component of lower back pain suggest that this is a valid conclusion.
Bibliography:	ObjectType-Article-1 SourceType-Scholarly Journals-1 ObjectType-Feature-2 content type line 23
ISSN:	0362-2436 1528-1159
DOI:	10.1097/01.brs.0000158876.51771.f8