PubMed Health⌕ Search

Biomedical subjects

R H Wittenberg

Publications and source records attributed to R H Wittenberg.

At least 37 records · Page 2Linked to original sources
PubMed1995

Flexibility and distraction after monosegmental and bisegmental lumbosacral fixation with angular stable fixators.

STUDY DESIGN: In human lumbosacral spines, the flexibility and intersegmental distraction allowed by four monosegmental and bisegmental intrapedicular devices during compression and flexion/compression loading were investigated. OBJECTIVES: To compare the flexibility and intersegmental distraction allowed by four monosegmental and bisegmental intrapedicular, lumbosacral fixation devices applied to destabilized cadaveric spines, and to determine the effect of each device on the flexibility and intersegmental distraction of the motion segment above each fused segment. SUMMARY OF BACKGROUND DATA: The lumbosacral segment is the most mobile region in the lumbar spine, exhibiting the highest range of motion in both flexion and extension. Therefore, the fixation of this and the adjacent segment is of special clinical interest. METHODS: L5-S1 facetectomy or L5 laminectomy procedures were performed on cadaveric human lumbosacral spines. Fixation devices then were applied across one or two levels, and intersegmental motion under flexion/compression or under pure compression loads was monitored. RESULTS: The flexibility and posterior strain allowed by the four implants did not differ significantly between implants. The strain across the stabilized site (monosegmental and bisegmental) was below 10% for all devices tested. The flexibility and distraction were reduced to levels below intact after the fixators were applied. The distraction across the segment above the fusion was not increased because of fixation with these four fixators. CONCLUSIONS: Angular stable fixation devices, such as those described here, provide adequate stabilization of the posteriorly destabilized spine.

Adult↗
PubMed1995

Prostaglandin release from rat femurs after implantation of hydroxylapatite and aluminium oxide ceramics.

The bony reaction after implantation of uncemented ceramics is of special interest. Therefore porous and dense hydroxylapatite and aluminium oxide ceramics were implanted in rat femurs. One group received no surgical manipulation and another with a sham procedure where no ceramics were implanted served as controls. After 6 and 10 days the rat femurs were harvested and the release of PGE2 and 6-keto-PGF1 alpha was measured with specific radioimmunoassays. Decrease in the release of PGE2 from day 6 to day 10 was present in all three implants. In contrast, 6-keto-PGF1 alpha increased from day 6 to day 10. Comparing the ceramic types an increase in 6-keto-PGF1 alpha release was seen in the porous hydroxylapatite group. These prostaglandin (PG) release patterns after ceramic implantation are similar to those of fracture healing, but aluminium oxide seems to be inert, while hydroxylapatite, especially the porous type, stimulates 6-keto-PGF1 alpha release.

Aluminum Oxide↗
PubMed1994

Prostaglandin release from lumbar disc and facet joint tissue.

OBJECTIVES: The authors measured prostaglandin (PG) and leukotriene (LT) release from human disc and lumbar facet joint tissues. SUMMARY OF BACKGROUND DATA: High levels of phospholipase A2 (PLA2) have been measured in the human disc. PLA2 releases fatty acids from lipid membranes. These can be converted to PG and LT, which are potent inflammatory mediators and supposed to be involved in lumbar diseases. METHODS: The tissues were obtained during surgery and incubated in Tyrode's solution. PG and LT release was measured radioimmunologically from the supernatant. RESULTS: Disc (4 ng/g wet weight), cartilage (21 ng/g wet weight), and bone (14 ng/g wet weight) released PGs but no LTs. CONCLUSION: Because PG release from sequestrated disc is rather low, the inflammatory effect might be more because of immunologic reactions.

6-Ketoprostaglandin F1 alpha↗
PubMed1994

A comparison of the effects of automated percutaneous diskectomy and conventional diskectomy on intradiscal pressure, disk geometry, and stiffness.

Diskectomy, chemonucleolysis, percutaneous diskectomy, and laser ablation are used to treat patients with sciatica. The effects of percutaneous diskectomy on the intradiscal pressure of the human disk are not known. Our aims were to determine (a) whether removal of nucleus through automated percutaneous diskectomy significantly reduces intradiscal pressure without altering the disk geometry and stiffness, and if so, how much nucleus removal is required to achieve these goals; and (b) whether the effects of conventional diskectomy on these same parameters are equivalent to removal of nucleus through automated percutaneous diskectomy. Cyclic compressive loads of 20-900 N were applied to lumbar disks. Conventional diskectomy or automated percutaneous diskectomy (performed for 40 min with biomechanical measurements made four times at 10-min intervals) was then performed under zero load and the specimens retested under the same cyclic compressive loading. There were significant (p < 0.01) decreases in intradiscal pressure (by 7% under 900 N) after 10 min of automated percutaneous lumbar diskectomy. There were no further significant decreases in pressure during the next 30 min of percutaneous diskectomy. There were also significant decreases in pressure due to a puncture hole made with the Nucleotome trephine alone, without removal of disk material, and there was no difference in pressure after trephining alone and after percutaneous diskectomy. Decreases in disk height were significant, ranging from 5% at 10 min to 7% at 40 min of treatment. There were equivalent decreases in intradiscal pressure and disk height due to removal of similar amounts of nucleus during conventional diskectomy and during 40 min of percutaneous diskectomy.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1993

In vitro release of prostaglandins and leukotrienes from synovial tissue, cartilage, and bone in degenerative joint diseases.

OBJECTIVE: To determine the major source of eicosanoid release in arthritic joint tissues and to examine the modulation of this release by indomethacin and diclofenac. METHODS: Release of prostaglandin E2 (PGE2), 6-keto-PGF1 alpha, leukotriene B4 (LTB4), and LTC4 was measured in supernatants of synovial tissue, cartilage, and bone incubates from patients with osteoarthritis, active rheumatoid arthritis (RA), inactive RA, and pseudogout. Radioimmunoassay (RIA) was used to determine the levels of the eicosanoids. RESULTS: Addition of the divalent cation ionophore A23187 resulted in significant release of all eicosanoids measured from synovial tissue, but not from cartilage, cortical bone, or cancellous bone. PG release was significantly inhibited by the addition of indomethacin or diclofenac at either 10(-5) moles/liter or 10(-7) moles/liter. The amount of LTC4 released from cartilage and bone was only slightly above the detection limit of the RIA, whereas large amounts were released from synovial tissue. Neither indomethacin nor diclofenac had an effect on LTC4 release. LTC4 release from synovial tissue of patients with inactive RA was significantly decreased in comparison with the levels from synovial tissue of patients with the other joint diseases. There was no significant difference in PG release among patients in the various disease groups. CONCLUSION: Synovial tissue appears to be the major source of eicosanoids in synovial fluid. Indomethacin and diclofenac inhibit the release of PG, but not LT, from various joint tissues.

Arthritis↗
PubMed1993

Effect of screw diameter, insertion technique, and bone cement augmentation of pedicular screw fixation strength.

This study investigated (1) the effect of screw diameter and insertion technique in lumbar vertebrae, and insertion site in the sacrum, on the axial pullout force and transverse bending stiffness of pedicle screws, and (2) the effect of bone cement augmentation using polymethylmethacrylate (PMMA) and the biodegradable composite, poly(propylene glycol-fumarate) on axial pullout force and transverse bending stiffness of pedicle screws inserted into lumbar vertebrae. The axial pullout force and transverse bending stiffness of a 6.25-mm Steffee screw and a 6-mm Kluger screw did not differ significantly in vertebral bodies of similar equivalent bone mineral density. The axial pullout force of Schanz screws was significantly increased with a 1-mm increase in screw diameter. However, there was no significant increase in transverse bending stiffness. In the sacrum, an approach through the S1 facet produced significantly higher axial pullout forces and transverse bending stiffness than the approach described by Harrington and Dickson. PMMA and a biodegradable composite bone cement poly(propylene glycol-fumarate) both increased the axial pullout force. PMMA also increased the transverse bending stiffness.

Biomechanical Phenomena↗
PubMed1992

In vitro hyperextension injuries in the human cadaveric cervical spine.

To investigate the relationship between the type of hyperextension injuries and the conditions producing them, nine cervical specimens (occiput to T1) were loaded to failure in tension at a fixed extension angle of 30 degrees. Under these loading conditions, specimens failed at average tensile loads and extension moments of 499 +/- 148 (SD) N and 4.0 +/- 3.1 Nm, respectively. Failure occurred at an average tensile displacement of 18.8 +/- 7.7 mm. The anterior longitudinal ligament ruptured and the intervertebral disc failed in at least one level in all specimens. In four specimens, the disc failed at an additional level, leaving the anterior longitudinal ligament intact at that site. With one exception, all injuries occurred in the lower cervical spine (C5-C6 and C6-C7), the region most often injured in vivo. The location of the injuries was associated with the degree of degeneration of the facet joints and the discs. The discs of the lower cervical spine were significantly more degenerated than those at the C2-C3 level. In addition, the degree of disc degeneration in the noninjured discs was significantly less than in the injured discs. These data help quantify the threshold of injury and the patterns of tissue damage resulting from hypertension loading of the cervical spine.

Aged↗
PubMed1992

A biomechanical study of the fatigue characteristics of thoracolumbar fixation implants in a calf spine model.

Clinical failures of internal fixation implants for the treatment of the thoracolumbar spine are generally attributed to fatigue. Few studies, however, have characterized changes in fixation rigidity with time or subjected spine-implant fixation constructs to fatigue loading until failure. Fatigue characteristics of five dorsally applied spinal fixation implants were determined using lumbosacral calf spines, with an L3 vertebrectomy, loaded cyclically in combined compression (maximum 605 N) and flexion (maximum 16 Nm) for up to 100,000 cycles. Displacement transducers monitored motion at the site of instability and at the segment above the implants. Flexibility and strain at these segments were then calculated. A one-way analysis of variance showed that there were no significant differences in flexibility of the five fixation constructs (P greater than .05). A multiple Bonferroni test revealed that the AO and Kluger fixateur interne and Steffee plates, with fixation at L2 and L4, allowed significantly more strain (P less than .01) across the site of instability than did Harrington rods and Luque plates with fixation at L1, L2, L4, and L5. There were no significant differences between fixation constructs in initial strain above the implants. After 10,000 cycles, however, there were significant increases in strain across the segment above the Luque and Harrington implants (P less than .05). Failure of the AO Schanz screw occurred in three of six constructs at a mean of 73,300 cycles. The Steffee screws failed in four of five constructs at a mean of 20,800 cycles. The rods of the Kluger fixateur interne broke in four of five constructs at a mean of 47,800 cycles, and one screw slipped at 11,000 cycles. There were no metal failures in the Harrington or Luque implants.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1992

Heterotopic ossification after spinal cord injury. Epidemiology and risk factors.

From 1981 to 1986 we treated 413 patients for acute spinal-cord injuries. We reviewed 356 patients followed for a minimum of two years of whom 71 (20%) developed heterotopic ossification around one or more joints. Heterotopic ossification occurred more often in male patients (23%) than in female (10%), and was most frequent in the 20- to 30-year age group. It was also more common after injuries of the lower cervical or thoracic spine than after those of the lumbar spine. Patients with severe neurological deficits (Frankel grades A and B) showed significantly more heterotopic ossification but there was no correlation with the number or severity of associated head and limb injuries. Serum calcium levels did not change significantly in either group for 30 weeks after injury, but the erythrocyte sedimentation rate and the alkaline phosphatase level were significantly increased at six weeks in patients with heterotopic ossification.

Age Factors↗
PubMed1992

Surgical treatment of persistent elbow epicondylitis.

From 1978 through 1987, 86 patients with epicondylitis were admitted for surgery after failed conservative treatment. The Wilhelm technique was performed either alone or in combination with an intraarticular procedure. The Wilhelm technique involves denervation of the epicondyle. The intraarticular procedure described by Bosworth or Boyd involves a one-third resection of the orbicular ligament and resection of a synovial fold. Before surgery a local anesthetic was injected at the sore spot of the epicondyle. After almost complete pain relief after injection, a sole Wilhelm procedure was performed at the lateral epicondyle in 34 patients and at the medial epicondyle in 17 patients. For 27 patients in whom the pain persisted after the injection, a combined Wilhelm and intraarticular procedure using the Bosworth or Boyd method was used. Degeneration of the orbicular ligament or a redundant synovial fold was reported in 77% of the intraarticular operation reports. At a follow-up examination, a minimum of two years and an average of four years nine months after surgery, 85% had good and excellent results after lateral and medial Wilhelm and 56% after combined surgeries while the poor results were 3% and 7% respectively. The results of combined surgery worsened from discharge to follow-up examination, and they show fewer good results than those where a sole Wilhelm procedure was performed. Therefore, intraarticular surgery should be considered for patients with incomplete pain relief after a test injection, but it should not routinely be performed.

Adult↗
PubMed1991

Physical and mechanical properties of calf lumbosacral trabecular bone.

The physical and mechanical properties of calf lumbar and sacral trabecular bone were determined and compared with those of human trabecular bone. The mean tissue density (1.66 +/- 0.12 g cm-3), equivalent mineral density (169 +/- 36 mg cm-3), apparent density (453 +/- 89 mg cm-3), ash density (194 +/- 59 mg cm-3), ash content (0.6 +/- 0.05%), compressive strength (7.1 +/- 3.0 MPa) and compressive modulus (173 +/- 97 MPa) of calf trabecular bone are similar to those of young human. There were moderate, positive linear correlations between apparent density and equivalent mineral density, ash density, and compressive strength; and between compressive strength and equivalent mineral density (R2 ranging from 0.35 to 0.48, p less than 0.001). Apparent density, ash density, and equivalent mineral density did not differ significantly in different regions. In contrast to humans, the compressive strength increased from posterior, near the facet, to the anterior vertebral body. These comparisons of physical and mechanical properties, as well as anatomical comparisons by others, indicate that the calf spine is a good model of the young non-osteoporotic human spine and thus useful for the testing of spinal instrumentation.

Animals↗
PubMed1991

Biomechanical properties of resorbable poly-L-lactide plates and screws: a comparison with traditional systems.

Poly-L-lactide (PLA) plates and screws were tested in vitro in porcine ribs for uniaxial pullout and four-point bending strength. Results were compared to conventional systems (stainless steel and titanium). The biomechanical testing suggests that PLA screws have properties suitable for fixation of sagittal split osteotomies. Poly-L-lactide plates have indications in areas of low stress and noncompressive load.

Animals↗
PubMed1991

Importance of bone mineral density in instrumented spine fusions.

The effect of equivalent mineral density on pedicular screw fixation strength was investigated. The equivalent mineral density of human vertebral bodies was correlated highly with the pullout force of Kluger screws (r2 = 0.61, P less than 0.02). A moderate to high correlation existed between density and vertical force (r2 = 0.42 for Kluger screws, r2 = 0.55 for Steffee screws, P less than 0.02). In calf vertebral bodies of higher density (146 +/- 14 mg/cc), the forces were significantly higher than in the human vertebral bodies (P less than 0.05). Human lumbosacral spines were instrumented with three different fixators: Steffee plates, AO fixateur interne, and Kluger fixateur interne. Of five specimens with a mean density of 88 +/- 11 mg/cc, one screw loosened. More than one screw loosened in six specimens with a mean density of 63 +/- 12 mg/cc, and no screw loosened in four specimens with a mean density of 114 +/- 38 mg/cc. Measurement of equivalent mineral density correlates with the fixation strength of the intrapedicular screws in vitro and should be considered in patients with signs of osteopenia before using pedicular screws for spinal fusions. It is also concluded that calf spines are a good model for testing implants because they tend to focus failure processes in the implant rather than in the implant-bone interface.

Aged↗
PubMed1991

Release of prostaglandins from bone and muscle after femoral osteotomy in rats.

In rats after nonstabilized femoral osteotomies, the changes in the release of prostaglandins (PGs) during bone healing (from bone and surrounding muscle tissue) were determined for PGE2, PGF2 alpha, 6-keto-PGF1 alpha, and thromboxane B2. A unilateral osteotomy, with contralateral soft-tissue dissection, was performed. After 4 or 10 days, the rats were killed and soft tissue and femoral bone were incubated, and the release of PGs was measured with specific radioimmunoassays. The release of PGs from rat femurs without previous surgery and from the sham-operated on side did not differ after 180 minutes' incubation. The release of PGE2, 6-keto-PGF1 alpha, and thromboxane-B2 from the osteotomy site was increased for bone on Day 4 and for muscle on Day 10 when compared with the controls. The release of PGF2 alpha from bone and muscle was about the same on both days, but increased as compared with the controls on Day 10 for bone. On Day 10, the other PGs for muscle and bone tissue were decreased as compared with Day 4. The most pronounced release of PGs occurred during the early healing phase after osteotomy; as early as 10 days after surgery, most of the PGs were not increased when compared with the sham-operated on side.

6-Ketoprostaglandin F1 alpha↗
PubMed1990

Compressive strength of autologous and allogenous bone grafts for thoracolumbar and cervical spine fusion.

The selection of the bone graft type for stabilization of spinal fusion depends on availability, the clinical situation, and the desired mechanical stability. The authors determined the potential immediate postoperative compressive strength of various types of bone grafts under axial compression on a material testing machine. The fibular strut graft (5,070 +/- 3,250 N, mean +/- standard deviation [SD]) was significantly stronger (P less than 0.05) than the anterior (1,150 +/- 487 N) and posterior (667 +/- 311 N) iliac crest grafts, and the rib grafts (452 +/- 192 N). Hydroxyapatite grafts with a pore size of 200 mu were significantly stronger (P less than 0.05) than those with a pore size of 500 mu (1,420 +/- 480 N versus 338 +/- 78 N). Ethylenoxide sterilization had no significant effect on the immediate compressive strength. Bicortical and tricortical Bailey-Badgley and Cloward bone grafts also were compared. Results showed that all cervical graft types may be sufficiently strong to support sizable loads.

Aged↗
PubMed1990

Magnetic resonance imaging and computer tomography of acute spinal cord trauma.

Spinal cord lesions are not detectable on roentgenograms and computed tomography (CT) scans. Magnetic resonance images (MRIs) are able to make soft-tissue lesions visible. Interpretations of MRIs, CT scans, and roentgenograms were compared in 25 patients and three postmortem specimens with spinal cord injuries. In 14 patients and one specimen with normal roentgenograms and CT scans, the MRI demonstrated ten soft-tissue injuries as minimal displacement of the vertebral bodies or as a high signal intensity in the disc space, indicating a hematoma. Seven of the ten patients demonstrating soft-tissue injuries also had an intramedullary lesion, while in five of the 15 patients with normal CT scans, only a medullary lesion was present on MRI. In 11 patients and two postmortem specimens, fractures were seen on roentgenograms and CT scans. In these patients, the CT was superior to the MRI in detecting small bony fragments, but the medullary lesions were visible only on the MRIs. An intramedullary low signal intensity corresponded to macroscopically visible hemorrhages in the three postmortem specimens. The MRI provided important information in patients with neurologic deficits. No obvious pathologic changes were evident on the roentgenograms and CT scans. The MRI also demonstrated intramedullary and extramedullary soft-tissue lesions and was useful in establishing a diagnosis and in choosing appropriate therapy. CT, on the other hand, was superior in detecting small bony fragments and fracture lines.

Acute Disease↗
PubMedDate not supplied

[Intermediate-term follow-up of surgically managed tendinosis calcarea (calcifying subacromion syndrome--SAS) of the shoulder joint].

PURPOSE: Investigation of clinical und ultrasonographical results after operatively treated calcifying tendinitis. METHODS: 131 patients with calcifying tendinitis were treated by surgical decompression and, if necessary and possible, calcific deposit removal. 93% of these patients were clinically and ultrasonographically examined after an average time of 4 years and 5 months. RESULTS: Pain rating on a visual analogue scale 0-no pain to 10-maximum pain was 8.7 before surgery and 1.4 at follow-up. 88% of the patients rated the operation excellent or good. The Constant Score results corresponded to the average results of a normal population (100.3). At the time of examination in 16.4% of the cases new calcific deposits could be discovered. CONCLUSION: According to the clinical results operative treatment shows good and excellent results in a high degree even after unsuccessful non-operative therapy.

Acromion↗