摘要:

AbstractSpinal pain often is thought to be due to degeneration and mechanical failure of the intervertebral disc. Since the mechanical strength of the tissue depends on collagen fibers, the present study was designed to investigate the reactions in collagen metabolism after an experimentally induced disc injury. Five domestic pigs underwent an incision in the anterior part of the annulus fibrosus of disc L4‐L5 through a retroperitoneal approach. The animals were killed 3 months postoperatively, and the injured discs and intact discs (controls) from different animals were removed for chemical analysis. Slices were cut from seven different parts across the disc. The concentration of total collagen (hydroxyproline [Hyp]), the activities of the two key enzymes in collagen biosynthesis (prolyl 4‐hydroxylase [PH]and galactosylhydroxylysyl glucosyltransferase [GGT]), and the concentration of mature collagen crosslinks (hydroxypyridinium [HP]) were determined. In all experimental discs, the morphology had changed considerably: the nucleus pulposus was small, fibrous, and yellowish. The annular lamellar structure was partially destroyed and had been replaced by granulation tissue in the region of the injury. Large osteophytes had formed at the ventral edges of the vertebral bodies. In the nucleus pulposus, the Hyp concentration and the activities of PH and GGT were significantly increased, whereas the water content had decreased. The concentration of HP crosslinks was decreased in the anterior annulus fibro

ISSN:0736-0266    

DOI:10.1002/jor.1100120112

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe mechanical properties of the human lumbar anterior longitudinal ligament were investigated, and the influence of aging, disc degeneration, and vertebral bone density on these properties was determined. Tensile mechanical properties of the vertebra‐anterior longitudinal ligament‐vertebra complex were determined for 16 segments from cadavera of individuals who had been 21–79 years old (mean, 52.1 years) at the time of death. Regional strain patterns associated with three sites across the width and three sites along the length of the anterior longitudinal ligament were measured with use of a video‐based motion analysis system. In the young, normal anterior longitudinal ligament, the elastic moduli of the insertion and substance regions of the ligament were similar (approximately 500 MPa). During aging (21–79 years), the elastic modulus of the substance region increased 2‐fold, whereas the elastic modulus of the insertion decreased 3‐fold; this resulted in an approximately 5‐fold difference in elastic modulus between these regions in the older spine. The strength of the bone‐ligament complex decreased approximately 2‐fold (from 29 to 13 MPa) over this same age range. The outer portion of the anterior longitudinal ligament consistently had the highest peak tensile strains (11.8 ± 2.7%) in all of the specimens examined. Preparations with nondegenerated discs and high bone density were significantly stronger (66%) and failed in the ligament substance; in contrast, segments from older individuals with degenerated discs and lower bone density failed in the ligame

ISSN:0736-0266    

DOI:10.1002/jor.1100120113

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe early changes of the sagittal alignment of the spine and the asymmetry between the posterior and anterior elements were determined on the basis of 134 lateral and 167 anteroposterior radiographs obtained from a control group and from patients with early scoliosis. The radiographs were allocated into four groups according to the degree of the Cobb angle. In thoracic curves with a Cobb angle of more than 8°, the kyphosis and the vertebral sagittal wedge angle decreased in comparison with the control group. The sagittal‐wedge angle of the disc did not change significantly with increasing Cobb angle. The pedicle height in relation to the vertebral height, considered to represent the growth of the posterior element in relation to the growth of the anterior element, was not significantly different in the scoliotic groups as compared with the control group. The results indicate that changes of the sagittal configuration of the spine occur early in idiopathic scoliosis and that they are associated with disturbed growth of the vertebral body but not of the posterior elements. These findings seem to reflect a simulataneous deformation in the coronal and sagittal planes rather than a single growth disturbance in any specific pla

ISSN:0736-0266    

DOI:10.1002/jor.1100120114

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractAn elastomeric intervertebral disc spacer with hydroxyapatite ingrowth surfaces was implanted in a canine model. We studied (a) the mechanical behavior of motion segments at time 0 and at 3, 6, and 12 months and (b) the effect of the interface between the spacer and vertebral bone on implant stability and bone ingrowth. A polymeric spacer was designed with compressive and torsional properties similar to those of the isolated canine lumbar disc. Implantation of the spacer in canine cadaver motion segments permittedin situbiomechanical evaluation at time 0. Anin vivostudy permitted continuous neurological monitoring of animals, with evaluation of mechanical behavior, stability, and ingrowth at 3, 6, and 12 months. Mechanical testing of cadaver motion segments with the spacerin situresulted in decreased compressive and torsional stiffnesses, averaging 25 and 42%, respectively. This decrease was due to a combination of the surgical insult to the annulus and decortication of adjacent vertebral endplates. In thein vivostudy, all 12 animals tolerated the surgery well and none had permanent neurological impairment. The measured parameters indicated that behavior of the spacer‐motion segment composite appeared to return to normal within 3‐6 months. However, despite use of a porous hydroxyapatite on the implant surface, there was no significant bone ingrowth. Instead, a layer of dense fibrous connective tissue was formed at the spacer‐vertebral bone interface. Early migration of five of the 12 spacers resulted in eccentric loading patterns with consistent reactive osteophyte form

ISSN:0736-0266    

DOI:10.1002/jor.1100120115

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractComposite collagen prostheses are potentially useful for reconstruction of the anterior cruciate ligament (ACL). We evaluated the intraosseous response to composite collagen prostheses to determine if “biological fixation” could be used to secure the prostheses within surgical bone tunnels. The rate of degradation of the prosthesis and the response of the tissue were evaluated, as a function of collagen crosslinking agent and time, in nonloaded bone tunnels in rabbits. Prostheses were fabricated by the alignment of 200 reconstituted type‐I collagen fibers (60 μm in diameter) and the embedding of the fibers within a collagen matrix. The prostheses degraded rapidly within the bone tunnels in comparison with soft‐tissue implantation sites. Dehydrothermal‐cyanamide crosslinked collagen fibers were completely degraded by 8 weeks. Only 10% of glutaraldehyde crosslinked collagen fibers remained intact at 12 weeks. Fibrous tissue and inflammatory cells rapidly infiltrated the prostheses, and new bone surrounded the circumference of the prostheses, advancing toward the center at longer times. At the lateral cortex, where fibrous tissue emerged, the bone/soft‐tissue interface was delineated by a tidemark, similar to that observed in a normal ligament insertion site. Preliminary pull‐out testing of the soft tissue; this suggests rapid incorporation of the prostheses within the bone tunnels. Composite collagen prostheses designed for ACL reconstruction degrade rapidly in bone and induce rapid ingrowth of fibrous tissue and bone. These results suggest that tissue ingrowth in the bone tunnels might provide biological fixation for collagen prostheses used for ACL

ISSN:0736-0266    

DOI:10.1002/jor.1100120116

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractThe question of whether or not load affects the remodeling of a transplanted autogenous free graft was addressed by removal of the patella‐patellar tendon‐tibial tubercle complex from the right knees of 15 New Zealand White rabbits. The tubercle was split, and the tendon was divided with each half trimmed to an equal width. The autograft complex was transplanted into a subcutaneous tunnel on the back of the rabbit. Controlled cyclic loads were applied via transcutaneous sutures to half of the graft, while the other half remained unloaded. The mechanical stiffness and strength and the cell density of loaded and unloaded halves of the autograft were measured in nine animals at 3 weeks and in six animals at 6 weeks. Five autografts from four additional rabbits served as unimplanted controls. An analysis of variance showed that the loaded portions of the autografts had a significantly higher failure strength (mean of 90%) and were significantly stiffer (mean of 62%) than the unloaded halves at 3 and 6 weeks. Failure strength was significantly greater (mean of 90%) at 3 weeks than at 6 weeks. The autografts were less stiff and had a lower failure strength than the unimplanted controls, with the greatest difference occurring in the unloaded segments at 6 weeks. Histology revealed that both loaded and unloaded segments demonstrated an increase in cellularity at 6 weeks compared with 3 weeks. This report introduces a model for the study of the effect of load on soft‐tissue grafts and demonstrates that loading affects the remodeling process of a transferred auto

ISSN:0736-0266    

DOI:10.1002/jor.1100120117

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

摘要:

AbstractTo determine if articular cartilage contains structurally distinct populations of proteoglycan aggregates, we extracted and purified proteoglycans from canine knee cartilage under associative conditions. Equilibrium density gradient centrifugation separated three proteoglycan populations, on the basis of differences in sedimentation velocity, into groups of 21, 106, and 270 S. Electron microscopic examination showed that the 21 S samples contained free aggrecan molecules and clusters of aggrecan molecules, with a mean of five aggrecan molecules per cluster. The 106 and 270 S samples contained proteoglycan aggregates consisting of central hyaluronan filaments with multiple attached aggrecan molecules. The two populations of aggregates did not differ in mean aggrecan length or in the spacing of aggrecan molecules along the hyaluronan filaments, but the slower sedimenting aggregates (106 S) had significantly shorter hyaluronan filaments as measured by electron microscopy (mean hyaluronan length, 400 compared with 1,162 nm) and one‐third as many aggrecan molecules per aggregate (mean number of aggrecan molecules per aggregate, 15 compared with 44). This study shows that articular cartilage contains aggrecan clusters and two structurally distinct populations of proteoglycan aggregates. The differences between the two types of aggregate, in particular the number of aggrecan molecules per aggregate, may reflect differences in their assembly, stability, or turnover and give them different mechanical and biological propertie

ISSN:0736-0266    

DOI:10.1002/jor.1100120118

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY

ISSN:0736-0266    

DOI:10.1002/jor.1100120101

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1994

数据来源: WILEY