Collagen fibers as a temporary scaffold for replacement of ACL in goats.

ACL substitutes made of braided or plied purified collagen fibers and cross-linked with hexamethylenediisocyanate were implanted into a total of 14 adult goats to achieve resorption within 8 to 10 months. Two types of collagen fiber prostheses differing in degree of collagen purification were tested. The implants were harvested 2 to 11 months postimplantation, tested for mechanical strength, and evaluated by morphological methods. In the first group (n = 5), the less purified and less cross-linked collagen fiber ACL implant induced fast connective tissue ingrowth. At 6 months postimplantation, 40 to 60% of the collagen implant was resorbed. No studies on breaking strength were done in this group. In the second group, highly purified and more crosslinked ACL implants were less infiltrated by cells and were resorbed only by 10 to 20%. Still, the breaking strength was decreased to 10% of the original implant strength. In the second group, the fixation of the ACL implant in the bone tunnel with a bone wedge was insufficient (n = 6); however, additional fixation with metal screws was successful (n = 3). We conclude that cross-linked collagen fibers alone cannot be used as a safe ACL substitute as they quickly lose mechanical strength despite limited biodegradation.

Imaging of the pelvis and hip.

Imaging is basic in the orthopedic evaluation of hip disorders. For optimal evaluation of these images, the orthopedic surgeon must not only correlate normal anatomy and pathology with radiographic findings, but must also be familiar with the newer modalities of CT, magnetic resonance imaging and ultrasound and the role and place of these studies in the evaluation of musculoskeletal disorders. This article correlates normal anatomy of the hip with these modalities and discusses the details of these techniques, particularly CT and MRI, that are pertinent to the orthopedic surgeon.

Radiologic reporting of skeletal trauma.

The radiologist's report of skeletal trauma should include accurate, appropriate comments directed to the clinical objectives of the referring physician. An organization of these reports is suggested, addressing general and specific description of fractures with a discussion of pertinent clinical considerations.

Imaging of the elbow with an emphasis on trauma.

This article provides a review of imaging of the elbow with an emphasis on trauma. The pertinent bone and soft-tissue anatomy of the elbow is discussed, with particular attention paid to the soft-tissue anatomy of imaging importance. The pediatric patient is considered and the basic radiographic examination is outlined. Finally, selected problems of elbow trauma are addressed and the various types of fractures are detailed.

Coccidioides immitis osteomyelitis in a 12-month-old child.

The case of a 12-month-old Mexican-American boy with Coccidioides immitis osteomyelitis of the little finger metacarpal and os calcis is presented in which a "cure" was obtained. The child received treatment with high doses of amphotericin B in conjunction with debridement and packing the lesions with calcium sulfate pellets. Recommended treatment for C. immitis infection of the bone would be debridement and packing with graft combined with systemic antifungal medical therapy.

The control of peritendinous adhesions using topical beta-aminopropionitrile base.

The Lindsay chicken foot tendon model was utilized to test the effect of topically applied beta-aminopropionitrile base upon the tensile strength of peritendinous adhesions following tenolysis of a scarified flexor tendon. The agent reduced by one-third the force required to effect tendon gliding and flexion of the joints in the involved digit. The results show that topical beta-aminopropionitrile is effective in the control of peritendinous adhesions and, therefore, achieves sufficient depth of penetration topically to affect the peritendinous location. No adverse effects of the topically applied agent were demonstrated. The principle of topical therapeutics that may have significant benefits to patients with tendon injuries is demonstrated.

The Biomechanical Basis of Growth Plate Injuries.

In brief: Children are at high risk of growth plate injury, contrary to previous research data. Of 134 consecutive growth plate injuries seen at the University of Arizona Hospital in Tucson over a six-year period, 22% occurred in team sports and 20% in activities such as using playground equipment, horseback riding, roller and ice skating, skateboarding, and bicycling. The authors review clinically useful anatomical and biomechanical aspects of the growth plate and its injuries, reflecting their own research as well as other studies. They also discuss prevention and diagnosis of this common source of childhood injury.

Early pathogenesis of hemophilic arthropathy. Evolution of the subchondral cyst.

Observations of the knee joint made at surgical synovectomy in young children with the chronic synovitis stage of hemophilic arthropathy permitted description of the evolution of the subchondral cyst in this disease. Beginning as a subchondral hematoma beneath the load-bearing surfaces of the joint, the subchondral cyst expands, destroys bone and cartilage locally to become an osteochondral cyst, and, finally, presents as an osteochondral defect with discrete vertical margins and a depressed, sclerotic bony base. Since the thickness of articular cartilage around these osteochondral defects is well maintained, however, even weight-bearing radiographs did not reflect the extensive destruction observed at surgery. Radiographic staging of hemophilic arthropathy, while clinically useful, consistently underestimated the extent of damage to the joint surface. The pathogenesis of subchondral cysts demonstrated in the present study correlated with and explained the known radiographically observed changes of condylar flattening and intercondylar notch widening in hemophilic arthropathy.

Identification of the depth of burn injury by collagen stainability.

Heat-denatured collagen in burned skin stains red instead of blue in Masson's trichrome stain. This change in stainability corresponds to the loss of birefringence in slides examined in polarized light. The depth of the abnormal staining of the skin slices was proportional to the time and temperature of the heat exposure. It is concluded that the change in collagen stainability from blue to red relates to the loss of crystallinity or parallel alignment of the collagen fibers. It is further proposed that change in the stainability of collagen in the burns could be used to delineate the depth of the thermal skin injury or the effectiveness of the surgical excision or debridement of the wound by dressing materials.

Microvascular changes in Dupuytren's contracture.

Previous studies of certain fibrotic lesions (hypertrophic scar, keloid, pseudotendon) have revealed pervasive microvascular occlusion. Lowered oxygen tension is considered to be a stimulus to excessive collagen production and, hence, the scar. Because its characteristics are similar to those of other lesions, Dupuytren's contracture appeared to be a good model in which to confirm the presence of occluded microvessels. Six cases were examined by light, electron, and polarizing microscopy. Most of the microvessels from the precontracture band area throughout the periphery of the body of the nodules were occluded by a bulging of the endothelial cells into the lumen. The microvessels were surrounded by extensive layers of basal laminae. The nodules were essentially avascular. The presence of another fibrotic lesion in which pervasive microvascular occlusion occurs is suggestive of an underlying biologic principle concerning the generation of all fibrotic lesions.

Collagenous architecture of the growth plate and perichondrial ossification groove.

The orientation of collagen fibers in the growth plate and contiguous structures of a growing long bone was demonstrated by polarized light microscopy. Five major groups of collagen fibers were demonstrated: transphyseal (longitudinal), perichondrial-periosteal (longitudinal), epiphyseal (radial), perichondrial ring (circumferential), and metaphyseal bone (circumferential). Transphyseal collagen fibers extend from spicules of calcified cartilage in the metaphysis across the growth plate and into the epiphyseal cartilage and secondary ossification center. The transphyseal fibers interdigitate with radially oriented epiphyseal fibers which lie between the secondary ossification center and the zone of resting cells. A radial columnar alignment of cells, similar to the longitudinal cell columns of the growth plate, was correlated with the radial epiphyseal collagen fibers. Collagen fibers that are longitudinally oriented predominate in the perichondrium-periosteum. In the primary spongiosa, bone collagen is oriented obliquely and circumferentially on the longitudinal septa of calcified cartilage. A marked abundance of circumferentially oriented collagen fibers is seen within the perichondrial groove and in the perichondrium-periosteum directly over the groove. The perichondrial rings is the largest and most prominent of these circumferential groups.

1 alpha, 25-Dihydroxyvitamin D3 a metabolite of vitamin D that promotes bone repair.

1 alpha, 25-dihydroxyvitamin D3, the hormonal form of vitamin D3 that mediates calcium translocation in intestine and bone, was tested for its ability to promote fracture repair. Chicks were raised on a vitamin D-deficient diet supplemented with 1 alpha, 25-dihydroxyvitamin D3 for 3 weeks. Following fracture of the humerus, those chicks that did not receive continued 1 alpha, 25-dihydroxyvitamin D3 supplementation showed prolonged fracture healing, abnormal enchondral bone formation delayed remodeling of woven bone and osseous union, but normal formation of callus. Fracture repair in chicks receiving 1 alpha, 25-dihydroxyvitamin D3 was normal. These data indicate that 1 alpha, 25-dihydroxyvitamin D3 promotes bone repair in the absence of vitamin D3, 25-hydroxyvitamin D3, and 24,25-dihydroxyvitamin D3.

The John Charnley Award Paper. Experimental epiphysiolysis: etiologic models slipped capital femoral epiphysis.

The several anatomic features that permit the growth plate to resist shear forces were identified. Specific variations in these anatomic features were correlated with pathologic factors known to be associated with epiphysiolysis, including clinical correlations with slipped capital femoral epiphysis. Two models of epiphysiolysis representing different pathogenetic pathways were established in the pig and compared to clinical slipped capital femoral epiphysis in the human. Both experimental models and other models reported in the literature bear similarities mechanically and histologically to the human disease. Available evidence suggests that slipped capital femoral epiphysis may not be a single disease but a final mechanical event that occurs as a result of a variety of disease processes. These disease processes reduce by different mechanisms the ability of the growth plate to resist shear forces.

Biological effects of residual glutaraldehyde in glutaraldehyde-tanned collagen biomaterials.

Glutaraldehyde is commonly used to control physical and biological properties of collagen structure by means of intramolecular and/or intermolecular crosslinking of collagen molecules. Solubility, antigenicity, and biodegradation of naturally occurring or reconstituted collagenous matrices are effectively reduced by glutaraldehyde treatment. Adverse biological reactions to glutaraldehyde have been limited to infrequent contact dermatitis and to biocidal effects which are exploited in chemical sterilization media. In the present study of glutaraldehyde-tanned collagen sponge, the presence of glutaraldehyde was correlated with cytotoxic effects upon fibroblasts in tissue culture and foreign body giant cell reaction to bioimplants of the sponge. Fibroblast growth in tissue culture is 99% inhibited at media concentrations of 3.0 ppm glutaraldehyde. Extracts of glutaraldehyde collagen sponge in aqueous media at pH 7 and 4.5 yielded 6 micrograms and 65 micrograms glutaraldehyde per gram of collagen sponge, respectively. The yield increased tenfold at pH 4.5. Observations indicate that leaching of the glutaraldehyde from glutaraldehyde-tanned collagen sponge is sufficient to produce potentially adverse cellular effects both in vivo and in vitro.

Physiological importance of vitamin D metabolism.

1,25(OH)2D3 and 24,25(OH)2D3 are biosynthesized from 25(OH)D3 in kidney. A cytosol receptor for 1,25(OH)2D3, but not 24,25(OH)2D3, is detected in kidney as well as bone and gut. The function of 1,25(OH)2D3 in kidney is probably to enhance calcium-binding protein and mineral reabsorption and to induce vitamin D-24-OHase enzyme. Receptors for 1,25(OH)2D3 are present also in endocrine sites such as parathyroid, pancreas, pituitary, and placenta, possibly to mediate central control of mineral homeostasis. Finally, 1,25(OH)2D3 elicits normal bone mineralization and fracture healing, contrary to other reports that 24,25(OH)2D3 is uniquely required for such physiologic vitamin D actions.