Reconstruction of the anterior cruciate ligament with carbon fibres: unsatisfactory results after 8 years.

A total of 37 patients were operated on for anterior cruciate ligament (ACL) insufficiency between 1980 and 1989 using two types of carbon fibre ligament substitutes. The average age of the population was 23.6 years. The carbon fibre prostheses were covered with either a strip of medial joint capsule or lyophilized dura. Follow-up averaged 8.1 years (range 4-13 years), most of the operations being done from 1983 to 1985. Evaluation included a questionnaire, physical examination, Lysholm scoring, radiographs and cruciometer testing. The operated ACLs were looser than those in the contralateral healthy knees. The Lysholm scoring system gave acceptable results (excellent and good) in 43.5%, fair in 31.4% and poor in 24.1% of cases. Acceptable results provided better stability and muscle strength. During the follow-up there was an evident deterioration in stability as well as in Lysholm score. The results between the two types of ligaments did not become statistically different. Osteoarthrosis increased in all the knees examined radiographically (28/37). The results indicate that the ACL reconstructions using these types of carbon fibre prostheses lead to unacceptable results in the long-term follow-up.

Biologic anchorage of cruciate ligament prosthesis. Bone ingrowth and fixation of the Gore-Tex ligament in sheep.

The biologic fixation and strength of fixation of the polytetrafluoroethylene (PTFE) Gore-Tex ligament prosthesis was investigated in sheep knees. The device was inserted to replace the anterior cruciate ligament according to the recommended technique. Histological bone tunnel evaluation together with mechanical tensile studies were done at 6, 12, and 18 months. Already at 6 months the pull-out load of the prosthesis exceeded that of the normal ligament, and this finding persisted up to 18 months postoperatively. At 6 months there was marked fibrous tissue ingrowth into the prosthesis, and at 12 months trabecular bone had replaced the fibrous tissue between the interstices of the filaments; at 18 months bone even penetrated into the individual porous fibers of the prosthesis. The intra-articular part of the prosthesis was surrounded and partly invaded by undifferentiated connective tissue, with no recognizable macrophages or other inflammatory cells. In this experiment, the biocompatibility and porosity of the Gore-Tex prosthesis seemed optimal to permit ingrowth from surrounding fibrous and osseous tissues and firm anchorage into the bone tunnels.

Induction of connective tissue by various alloplastic materials: an experimental study in rats.

The capacity of three alloplastic implant materials to induce connective tissue was tested on the backs of 19 rats. A standardized viscous sponge served as control material. The commercial implant materials studied were carbon fibre and polypropylene ligament prostheses and a sponge composite of polytetrafluorethylene polymer and graphite fibre. Quantitative biochemical analyses (DNA, RNA, hydroxyproline and hexosamines) were done at 3 and 10 d, and 3, 6 and 9 wk post-operatively. Histological studies were done at 3, 6 and 9 wk. During the follow-up all the materials, when implanted subcutaneously, showed some capacity to induce ingrowth of granulation tissue. However, according to both quantitative chemical analyses and histological studies, the inductive capacity was greatest in the control sponge and in the polypropylene ligament prosthesis. In contrast, chemical analyses showed that the amount of granulation tissue developing during the follow-up was least in the rats with carbon fibre ligament implants.

Carbon fiber as a prosthetic anterior cruciate ligament. A biochemical and histological analysis in pigs.

Connective tissue ingrowth into a carbon fiber prosthesis inserted as a substitute for the ACL was biochemically quantified in an experimental pig model with a followup of 16 weeks. During this time, the net collagen amount expressed as hydroxyproline increased to only half that of the normal control ligament. Histological studies revealed relatively few fibroblasts capable of producing collagen inside the alloplastic ligament. When these results are considered in conjunction with those of our earlier report of the disappointing mechanical strength of the carbon fiber substitutes, it seems evident that carbon fiber is not a suitable replacement for the ACL, mainly because of its failure to produce a "neoligament" before it disintegrates.

Collagen types I and III and fibronectin in healing anterior cruciate ligament after reconstruction with carbon fibre.

The presence of the connective tissue components fibronectin and collagen types I and III have been demonstrated by immunohistological methods after reconstruction of the anterior cruciate ligament of pigs with carbon fibre. The carbon fibre ligament prosthesis was covered with pediculated fascia lata. During the initial 16-week period, fibronectin was seen both in the surrounding fascial layer and between the carbon fibres of the substitute. Type III collagen was also found, especially in the fascial layer, but collagen was absent from the carbon fibre prosthesis and was seen only in the fascial layer. Results indicate that the tissue in the 'neoligament' after carbon fibre reconstruction consists mostly of granulation tissue with a high amount of fibronectin, and type III collagen from mesenchymal cells without sufficient amount of type I collagen with tensile strength to withstand subsequent mobilization and rehabilitation.

Tissue reactions around two alloplastic ligament substitute materials: experimental study on rats with carbon fibres and polypropylene.

The early connective tissue reactions around two alloplastic and prosthetic materials, carbon fibre and polypropylene were examined in 30 rats. Each of the materials was implanted into three sites: under the skin, intraperitoneally and into a femoral bone tunnel. Microscopic and scanning electron microscopic findings at 1, 3, 6, 9 and 12 wk post-operatively are described. The amount of granulation tissue around the carbon fibres was more prominent in all the environments, but the connective tissue remained less mature and less organized during the whole follow-up compared to that of the polypropylene. There was no ingrowth of bone between the bundles of the artificial materials in the bony tunnels. The differences in the early cellular reactions and scar tissue maturation in the interstices of these two materials are probably due to the structural differences rather than to the surface properties of the materials.

Reconstruction of anterior cruciate ligament with carbon fiber. An experimental study on pigs.

During a follow-up period of 16 weeks in 18 pigs, macroscopical and histological studies revealed invasion of fibroblasts and mesenchymal cells around the carbon fiber prosthesis inserted to replace the ACL but scarce tissue ingrowth into the prosthesis proper. There was no adherence of the carbon ligament onto the bony channels. The peak tensile strength of the reconstructed ligament was about one third of the paired normal ACL ligament during the 16 week experiment.