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ABSTRACT: A biomechanical study to evaluate the effects of a biodegradable calcium phosphate (Ca-P) bone substitute on the fixation strength and bending rigidity of vertebral body screws.
To determine if an injectable, biodegradable Ca-P bone substitute provides significant augmentation of anterior vertebral screw fixation in the osteoporotic spine.
Polymethylmethacrylate (PMMA) augmented screws have been used clinically; however, there is concern about thermal damage to the neural elements during polymerization of the PMMA as well as its negative effects on bone remodeling. Injectable, biodegradable Ca-P bone substitutes have shown enhanced fixation of pedicle screws.
Sixteen fresh cadaveric thoracolumbar vertebrae were randomly divided into two groups: control (no augmentation) (n = 8) and Ca-P bone substitute augmentation (n = 8) groups. Bone-screw fixation rigidity in bending was determined initially and after 10(5) cycles, followed by pullout testing of the screw to failure to determine pullout strength and stiffness.
The bone-screw bending rigidity for the Ca-P bone substitute group was significantly greater than the control group, initially (58%) and after cyclic loading (125%). The pullout strength for Ca-P bone substitute group (1848 +/- 166 N) was significantly greater than the control group (665 +/- 92 N) (P < 0.01). Stiffness in pullout for the Ca-P bone substitute groups (399 +/- 69 N/mm) was significantly higher than the control group (210 +/- 51 N/mm) (P < 0.01).
This study demonstrated that augmentation of anterior vertebral body screw fixation with a biodegradable Ca-P bone substitute is a potential alternative to the use of PMMA cement.
Spine 12/2001; 26(24):2679-83. · 2.08 Impact Factor
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ABSTRACT: The existence of diabetes mellitus has been postulated to have a deleterious effect on the outcome following lumbar spine surgery. We retrospectively examined the records and radiographs of 32 diabetic patients (mean age, 60 years) who underwent posterior lumbar fusions using transpedicular instrumentation and iliac crest autograft. Ten patients were insulin-dependent and 22 required oral hypoglycemic agents for at least 1 year prior to surgery. The minimum follow-up time was 2 years after surgery (mean, 2.5 years). Surgical indications included herniated lumbar disk, lumbar spinal stenosis, thoracolumbar trauma, and lumbar pseudarthrosis. Clinical results were evaluated by chart review and/or interview by using Odom's criteria. At follow-up, 75% of patients were graded as excellent or good, and 25% as fair or poor. Twenty-five of 32 patients (78%) had improvement of back pain. Twenty of 27 (74%) patients had improvement of leg pain. Eight of 15 (53%) patients had improvement in motor strength, and 6 of 11 (54%) had improvement in light-touch sensation. Insulin dependence and the presence of polyneuropathy were associated with a poorer outcome. The average time to radiographic fusion was 5 months. Twenty-nine of 32 patients (91%) developed solid fusion by strict radiographic criteria. The three patients with a pseudarthrosis had persistent back pain and a poor result. Ten of 32 (31%) of the patients experienced perioperative complications, including prolonged wound drainage (n = 5), deep wound infection (n = 1), superficial wound infection (n = 1), atrial fibrillation (n = 1), ruptured cerebral aneurysm (n = 1), and ulnar nerve neuropathy (n = 1). We conclude that posterolateral lumbar spinal fusion with internal fixation in diabetic patients yields clinical results comparable to those of nondiabetic patients, with similar risks of perioperative complications.
American journal of orthopedics (Belle Mead, N.J.) 09/2000; 29(8):617-20.
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Instructional course lectures 02/1994; 43:441-9.
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ABSTRACT: A study was conducted to determine the ability of demineralized bone matrix gel to act as an osteoconductive/osteoinductive material to enhance canine spinal fusion. Seven dogs underwent posterior spinal fusion. Four-level fusions were performed with one of four procedures at each level: decortication alone, with gel added, with autograft, or with both gel and autograft. Dogs were killed at 6 weeks and early histologic response was studied. At untreated control sites, little bone formation was evident. Gel-filled sites showed abundant osteoid, with 60% of demineralized particles fused to or surrounded by new bone. Sites filled with autograft had more new bone, but there was more osteoid at gel-treated sites. Autograft augmented with gel showed the most vigorous response, with extensive bridging between demineralized particles, host bone, autograft, and new bone. Significantly less autograft was needed to induce a similar amount of new bone formation when gel was added. Use of the gel as an autograft extender may improve the chance for successful spinal fusion.
Spine 10/1993; 18(12):1634-9. · 2.08 Impact Factor
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ABSTRACT: The bone marrow is a target organ for the human immunodeficiency virus (HIV), but the mechanisms by which suppression of hematopoiesis occurs during the course of HIV infection are not well understood. To study this issue, the effect of several different HIV-1 isolates (monotrophic and lymphotrophic) and one HIV-2 isolate on in vitro colony formation by BFU-E and CFU-GM from normal human marrow were examined. The monotrophic strain AD-87 (M) failed to replicate in marrow cultures as documented by RT, and colony formation by BFU-E and CFU-GM was unaffected by this virus. A derivative of this isolate AD-87 (M-P), which was replicated in peripheral blood lymphocytes (PBL), however, replicated well and markedly inhibited colony formation by BFU-E and CFU-GM. Two additional PBL isolates replicated less efficiently; neither inhibited CFU-GM but one consistently inhibited BFU-E colony formation. Inhibition of colony formation by the HIV-1 isolates was a late event, presumably a secondary lysis of cells, since up to 7 days after inoculation colony numbers were normal but diminished markedly by 10 days, and since only up to 10% of the cells of the monocyte lineage contained detectable virus by in situ, EM, and IFA studies. In contrast, the HIV-2 isolate was so lytic that by 4 days after inoculation the majority of the marrow cells were destroyed.
Virology 07/1992; 188(2):840-9. · 3.35 Impact Factor
