The development of a novel implant: induction of a non-rigid and self-renewing anchorage of artificial implants to bone.

Artificial implants currently used in orthopaedic surgery and dentistry are anchored to the surrounding bone by rigid mechanical fixation. Long-term studies indicate that the rate of implant failure due to loosening increases steeply after 10 years of function. The loosening is attributed to the micro-movements occurring at the bone implant interface. Non-rigid, self-renewing ligamentous anchorage is nature's solution to the problem of micro-movements. An excellent example of this type of anchorage is the tooth-bone system, where the tooth is anchored to the bone by a fibrous connective tissue. A novel artificial implant, bearing on its surface a unique biological substrate (BS), was designed to induce a ligamentous anchorage of implant to bone. The implant consists of a metallic core to which the BS is bound. The BS is a composite of plastic material and a collagen mesh which is partly incorporated into the plastic material and partly freely extended from its outer surface as artificial Sharpey's fibers. BS fabrication did not affect the capacity of the collagen to withstand non-specific degradation in vitro. Non-weight-bearing implants implanted into the femoral bone of rats induced and maintained a ligament-like tissue up to 4 months. The collagen fibers of the ligament-like tissue were spliced with the artificial BS Sharpey's fibers and were also anchored as Sharpey's fibers into the surrounding bone. Examination of control plastic implants (without the BS) revealed bone formation in close approximation to the implant surface.(ABSTRACT TRUNCATED AT 250 WORDS)

Heparan sulfate and fibronectin improve the capacity of collagen barriers to prevent apical migration of the junctional epithelium.

The objective of the present study was to assess the effect of bilayered/collagen barriers enriched with fibronectin and heparan sulfate on the prevention of apical migration of the epithelium during the initial stage of periodontal wound healing. Experimental osseous defects were produced on the labial aspect of maxillary canines in dogs. Experimental sites were treated with either bilayered enriched collagen barriers or with non-enriched bilayered collagen barriers, using the guided tissue regeneration technique. Control sites were treated with monolayered collagen barriers that were not enriched with fibronectin and heparan sulfate. Histologic and histomorphometric examinations performed on specimens obtained 20 days post-operative indicate the formation of a short junctional epithelium in the experimental sites treated with enriched collagen barriers. In this group, 95% of the occlusal-apical length of the defects was repopulated by connective tissue cells. In the other 2 groups, a long junctional epithelium developed with only 65% of the occlusal-apical length of the defects being repopulated by connective tissue cells. These findings suggest that the enrichment of collagen barriers with fibronectin and heparan sulfate may be important to enhance the repopulation of exposed root surfaces by connective tissue cells and prevent the apical migration of the epithelium during the initial stages of periodontal wound healing.

Blood levels of vitamin D metabolites in gonarthrosis.

The blood levels of the active metabolites of vitamin D3 25-hydroxycholecalciferol [25(OH)D3]. 1,25-dihydroxycholecalciferol [1,25(OH)2D3], and 24,25-dihydroxycholecalciferol [24,25(OH)2D3] were determined in 27 patients suffering from arthrosis of the knee, including 4 patients with non-insulin-dependent diabetes mellitus. The blood level of 24,25-dihydroxycholecalciferol was found to be significantly lower in patients with gonarthrosis than in patients with coxarthrosis. With the exclusion of the diabetic patients, the mean value for this metabolite was lower than in the coxarthrosis group, but the difference was not significant statistically.

Blood levels of active metabolites of vitamin D3 in fracture repair in humans. A preliminary report.

Blood levels of the active metabolites of vitamin D3, 25-hydroxycholecalciferol [25(OH)D3], 1,25-dihydroxycholecalciferol [1,25(OH)2D3] and 24,25-dihydroxycholecalciferol [24,25(OH)2D3] were determined in seven patients. Two subjects suffered from delayed union of tibial fractures; one showed a delayed union after a proximal tibial osteotomy; one patient suffered from bilateral femoral neck fractures, of which one failed to unite and the other united late; two patients had multiple fractures that united normally; and one patient exhibited staged bilateral femoral neck fractures whose occurrence was separated by a short interval and which united without undue delay. The blood levels of 25(OH)D3 were within the normal range. A relative decrease in 24,25(OH)2D3 values was noted in all patients, whereas in three subjects the decrease was absolute, to non-detectable levels. A decrease in 1,25(OH)2D3 levels was noted in only two patients. We postulate that these changes reflect the consumption of these metabolites during healing at the fracture site.

Collagen membranes prevent apical migration of epithelium and support new connective tissue attachment during periodontal wound healing in dogs.

The capacity of collagen membranes to prevent the apical migration of epithelium and to support new connective tissue attachment was assessed in experimental periodontal defects in dogs. Experimental periodontal defects were produced in 8 mongrel dogs by removing the alveolar bone and the periodontal ligament over the most coronal 5 mm of the labial aspect of the maxillary canines. Experimental defects associated with the right canine and its surrounding bone were covered by collagen membranes prepared by air drying gels of rat type I fibrillar collagen. Flaps were repositioned and sutured. The contralateral control defects were sham-operated without using collagen membranes. Animals were killed, 10 and 30 days after surgery, 4 at each time point. The experimental and control sites were processed for histologic and histomorphometric evaluation. At 10 d, the average distance between the apical margin of the epithelium and the apical level of the defect (EA) sites was 3.20 +/- 0.55 mm for the experimental sites and 0.73 +/- 0.18 mm for the controls. The experimental root surfaces apical to the epithelium and the collagen membranes were covered by connective tissue cells. At 30 d, the EA for experimental and control sites were 2.55 +/- 0.36 mm and 0.47 +/- 0.30 mm, respectively. In the experimental sites healing by long junctional epithelium was observed in the coronal 40% of apico-occlusal dimension of the defect and new connective tissue attachment with inserting fibers in the apical 55% of the defect length. No new bone formation was observed. In the control sites, pocket formation was found in the most coronal one-third of the defect.(ABSTRACT TRUNCATED AT 250 WORDS)

Active metabolites of vitamin D in patients with coxarthrosis and with aseptic loosening of total hip endoprostheses.

The blood levels of the active metabolites of vitamin D--25-hydroxycholecalciferol (25(OH)D), 1,25 dihydroxycholecalciferol (1,25(OH)2D), and 24,25 dihydroxycholecalciferol (24,25(OH)2D)--were determined in 15 patients suffering from arthrosis of the hip and in 13 patients with aseptic loosening of total hip endoprostheses. Normal values were found in all but one patient with aseptic loosening, in whom 24,25(OH)2D was not detectable. The difference between the two groups of patients was not statistically significant.

Partial regeneration of periodontal tissues using collagen barriers. Initial observations in the canine.

The capacity of collagen membranes to support guided regeneration of periodontal tissues in the dog was assessed. The mesiolabial, labial and distolabial aspects of the mesial root of the second and third mandibular premolar were surgically exposed in three beagle dogs. Collagen membranes, 0.5 to 0.7 mm thick, prepared from a purified solution of rat-Type I collagen were interposed between the gingival flap and the exposed root surfaces of the right premolars. The left premolars were sham-operated without the use of collagen membranes. Animals were killed one month after surgery. Tissue blocks, including the surgical sites, were removed and prepared for histological and histometric examination. Long epithelial attachment was the modality of healing in the control sites. The apical level of the junctional epithelium was located either at, or close to, the apical level of the defect. The experimental sites exhibited a combination of three healing modalities: (1) partial regeneration of periodontal tissues (new bone, periodontal ligament and cementum) occurred in the apical half of the defect, (2) long epithelial attachment developed in the coronal quarter of the defect and (3) connective tissue adhesion developed between the two. Pocket depth was similar in both the control and experimental sites. Collagen membranes could not be identified at the time of examination. The results indicate that: (1) collagen membranes have the capacity to support regeneration of periodontal tissues and (2) collagen membranes are either incorporated within the healing tissues or degraded by these during the healing process. These findings suggest that collagen membranes may be of value in reconstructive periodontal therapy.

Disruption of the symphysis pubis and fatigue fractures of the pelvis in a patient with rheumatoid arthritis. A case report.

A 40-year-old woman, who suffered from severe rheumatoid arthritis causing avascular necrosis of the femoral head and protrusio acetabuli of the right hip, developed a severe spontaneous disruption of the symphysis pubis concomitant with a stress fracture of the left ilium adjacent to the left sacroiliac joint. After successful total hip arthroplasty, the symphysiolysis improved, but a new stress fracture of the left superior pubic ramus developed. Fourteen months after operation both stress fractures are healed. Altered hip and pelvic girdle mechanics acting on osteoporotic bone may account for this sequence of events.

Lateral patellar release and bone grafting of the tibial plateau in total condylar knee arthroplasties. A technical note.

In a review of 50 primary total condylar knee arthroplasties in 25 female and in 14 male patients the factors affecting the necessity of lateral patellar release and bone grafting of the medial tibial plateau were established. Lateral patellar release was performed in 18 of 33 arthroplasties in female patients, in only two of 17 operations in male patients, and on all but one of the knees with preoperative valgus deformity. Bone grafting of the medial tibial plateau was necessary mainly in small knees, i.e., for six of 18 small prostheses in contrast to one of 15 standard-sized implants in female patients and in none of the operated knees in males.