Pyrolytic Carbon Implants Research Articles

Proximal interphalangeal (PIP) joint replacements with pyrolytic carbon implants in the hand.

Until the late 1980s, proximal interphalangeal (PIP) joint reconstruction had been almost exclusively performed by the use of monobloc silicone spacers and associated with acceptable to good clinical outcomes.More recently, new materials such as metal-on-polyethylene and pyrocarbon implants were proposed, associated with good short-term and mid-term results.Pyrocarbon is a biologically inert and biocompatible material with a low tendency to wear. PIP pyrolytic implants are characterised by a graphite core, visible on radiographs and covered by a radiolucent outer layer of pyrocarbon.New surgical techniques and better patient selection with tailored rehabilitative protocols, associated with the knowledge arising from the long-term experience with pyrocarbon implants, has demonstrated noteworthy clinical outcomes over the years, as demonstrated by recent studies. Cite this article: EFORT Open Rev 2017;2:21–27. DOI: 10.1302/2058-5241.2.160041

Biological and functional evaluation of a novel pyrolytic carbon implant for the treatment of focal osteochondral defects in the medial femoral condyle: assessment in a canine model.

BackgroundOsteochondral defects continue to be a clinical treatment challenge, and when left untreated, may cause pain and functional impairment. Pyrolytic carbon is a unique isotropic biomaterial used in heart valve and small joint replacements due to its excellent wear properties and biocompatibility with bone and articular cartilage. Therefore, a proposed solution is to utilize a focal pyrolytic carbon hemiarthroplasty implant as an alternative resurfacing treatment strategy for isolated cartilage lesions.MethodsA canine model (n = 9) was used to evaluate the in vivo histologic response and function of a pyrolytic carbon implant replacing a full-thickness osteochondral defect in the medial femoral condyle (MFC) of the knee. The gross appearance and histologic results were compared to an identical cobalt-chromium (Co-Cr) alloy implant placed in a defect in the contralateral MFC and evaluated up to 52 weeks.ResultsExtensive bone incorporation to the stem portion was observed for both implant types. The total mean histologic score for the cartilage of the MFC surrounding the pyrolytic carbon implants was significantly improved compared to that of the Co-Cr alloy implants at all evaluation periods (p < 0.05). Histologic grading and gross observations at 52 weeks for pyrolytic carbon implants were similar to those of Co-Cr alloy implants at 24 weeks. At 24 weeks, the mean total histologic score for Co-Cr alloy implants was 11.6 ± 0.7 (0–16 range point; 16 = normal appearance), while at 52 weeks, the mean total score for the pyrolytic carbon implants was 11.7 ± 1.3. Mean total histologic score of opposing medial tibia cartilage for the pyrolytic carbon implants was superior to that of the Co-Cr alloy group at all evaluation periods and significantly improved over the Co-Cr alloy implant group at 24 weeks (p = 0.001) and 52 weeks (p < 0.001).ConclusionsUse of a pyrolytic carbon implant for reconstruction of a focal cartilage defect demonstrated effective implant fixation and superior in vivo response compared to an identical Co-Cr alloy implant.

Characterization of cell cultures in contact with different orthopedic implants biomaterials

The aim of this study is to identify the role of biological and mechanical constraints (at the cellular level) surrounding living tissues (cartilage and bone) in the presence of different joint implant biomaterials. In this fact, cells cultures in the presence of different types of biomaterials (pyrolytic carbon, cobalt-Chromium, titanium) has been performed. These cell cultures were subjected to biological characterization tests and mechanical characterization. The obtained results correlate with the in vivo observations (a promotion of the creation of a neocartilagical tissue in contact with the Pyrolytic Carbon implants).

Fabrication and Testing of Planar Stent Mesh Designs Using Carbon-Infiltrated Carbon Nanotubes

This paper explores and demonstrates the potential of using pyrolytic carbon as a material for coronary stents. Stents are commonly fabricated from metal, which has worse biocompatibilty than many polymers and ceramics. Pyrolytic carbon, a ceramic, is currently used in medical implant devices due to its preferable biocompatibility properties. Micropatterned pyrolytic carbon implants can be created by growing carbon nanotubes (CNTs), and then filling the space between with amorphous carbon via chemical vapor deposition (CVD). We prepared multiple samples of two different stent-like flexible mesh designs and smaller cubic structures out of carbon-infiltrated carbon nanotubes (CI-CNT). Tension loads were applied to expand the mesh samples and we recorded the forces at brittle failure. The cubic structures were used for separate compression tests. These data were then used in conjunction with a nonlinear finite element analysis (FEA) model of the stent geometry to determine Young's modulus and maximum fracture strain in tension and compression for each sample. Additionally, images were recorded of the mesh samples before, during, and at failure. These images were used to measure an overall percent elongation for each sample. The highest fracture strain observed was 1.4% and Young's modulus values confirmed that the material was similar to that used in previous carbon-infiltrated carbon nanotube work. The average percent elongation was 86% with a maximum of 145%. This exceeds a typical target of 66%. The material properties found from compression testing show less stiffness than the mesh samples; however, specimen evaluation reveals poorly infiltrated samples.

Arthroplasty of the Hand: Radiographic Outcomes of Pyrolytic Carbon Proximal Interphalangeal and Metacarpophalangeal Joint Replacements

The purpose of this study was to describe the radiographic outcomes of pyrolytic carbon implants in the proximal interphalangeal (PIP) and metacarpophalangeal (MCP) joints, determine the most common complications, and assess risk factors associated with complications. Retrospective review over a 10-year period was performed to identify patients with pyrolytic carbon implants of the PIP or MCP joint. All available radiographs were reviewed and correlated with clinical information. Statistical analysis included calculation of the complication rate, Phi coefficient for variable association with a complication, and Kaplan-Meier survival. Forty-seven implants in 43 patients were reviewed. There were 30 PIP and 17 MCP implants. The mean age of the patients was 56 years. The mean radiographic follow-up was 17.2 months (range, 1-82 months). The indication for arthroplasty included osteoarthritis (55.3%), trauma (27.7%), rheumatoid arthritis (12.8%), and benign neoplasm (4.26%). Fourteen second surgeries were performed: four for retrieval and 10 for revision. Radiographic abnormalities included subsidence (31.9%); loosening with dorsal or volar tilt of the stem (34.1%); loosening without tilt (6.38%); periprosthetic fracture (8.51%); and ulnar subluxation of joint (4.26%). There was no statistical association (r < 0.001) between 1 mm or less of symmetric lucency around the distal implant with future complications. The sensitivity of radiography for the clinical failure of the implant was 28.6% and specificity, 30.3%. Of the 47 pyrolytic carbon PIP and MCP implants, 14 (29.8%) required surgical revision or retrieval, mostly for extensor tendon contractures. Compared with the clinical survival of the implant, radiographic survival was poorer and did not correlate with clinical survival. Tilt of the proximal stem and subsidence were the more common radiographic complications.

Questions about Implant-Bone Interface with Pyrolytic Carbon

Pyrolytic carbon (pyrocarbon) was hailed at the time of its introduction for use in small joint arthroplasty as an ideal material because of its excellent wear characteristics and biological compatibility with joint tissues. In this article, Sweets and Stern present the longest-term follow-up to date of pyrolytic carbon implants for proximal interphalangeal joint arthroplasty in patients with osteoarthritis. At an average of fifty-five months, with over half the patient cohort followed for more than five years, the authors noted a high rate of failure after proximal interphalangeal joint arthroplasty with pyrolytic carbon implants, including dislocation, subsidence and loosening, implant fracture, and joint contracture, with a reoperation rate of 19%. The literature on the use of pyrolytic carbon implants for the proximal interphalangeal joint has shown mixed results, including a previous study by one of the authors (P.J.S.) that noted …

Early Outcomes of Pyrolytic Carbon Hemiarthroplasty for the Treatment of Trapezial-Metacarpal Arthritis

Pyrolytic carbon implants have been successfully used in the treatment of osteoarthritis of the metacarpophalangeal and proximal interphalangeal joints. Recently, pyrolytic carbon hemiarthroplasties have been proposed for the treatment of osteoarthritis of the trapezial-metacarpal (TM) joint of the thumb. We wished to review our short-term outcomes for this device in the treatment of TM arthritis. Fifty-four arthritic TM joints in 49 patients, with a mean age of 59 years, were treated with use of a pyrolytic carbon hemiarthroplasty procedure. Underlying diagnoses included osteoarthritis in 44 thumbs, rheumatoid arthritis in 8 thumbs, psoriatic arthritis in 1 thumb, and juvenile rheumatoid arthritis in 1 thumb. The patients were followed up clinically as well as radiologically for an average of 22 months postoperatively. The overall 22-month survival rate excluding scaphotrapezio-trapezoidal joint arthritis was 80% according to a Kaplan-Meier analysis. Ten metacarpal subluxations were observed. Seven of these cases were salvaged by increasing the depth of the trapezial cup. A total of 15 reoperations were required in this cohort. No complications were seen in the patients with inflammatory arthritis. Thirty-five patients were pain free at the latest follow-up, and 6 reported mild to occasional pain with repetitive activities. The overall satisfaction rate was 40 of 49 patients (81%). Grip strength recovered to 86% of that of the contralateral side. Apposition key and opposition pinch strength improved to 92% and 95%, respectively, of those of the contralateral hand. Pyrolytic carbon thumb arthroplasty may prove to be an acceptable option for the treatment of TM, although a high complication rate was observed in this early cohort, with many cases of subluxation attributed to the creation of a too shallow trapezial cup. Further comparative studies are warranted. Therapeutic IV.

Preliminary Results of Nonconstrained Pyrolytic Carbon Arthroplasty for Metacarpophalangeal Joint Arthritis

To review early outcomes of arthritic metacarpophalangeal (MCP) joints treated with nonconstrained pyrolytic carbon implants to evaluate efficacy, clinical outcomes, and durability. One hundred forty-two consecutive arthroplasties (61 patients) were retrospectively reviewed. Diagnoses included osteoarthritis (OA), traumatic arthritis, and inflammatory arthritis. One hundred thirty were primary joint replacements, and 12 were prior-silicone revisions. The average patient age was 55 years (range, 21-77 years); 36 patients were women and 25 were men. Average follow-up period was 17 months (range, 3-42 months), and 43 patients were followed up for a minimum of 1 year. For OA patients, according to the analog pain scale used, pain decreased from 73.0 to 8.5 of 100, functionality increased from 20.1 to 86.6 of 100, and appearance improved from 62.7 to 93.6 of 100. The rheumatoid arthritis (RA) group showed decreased pain from 43.1 to 8.9 of 100, functional improvement from 26.7 to 83.3 of 100, and increased appearance from 25.2 to 77.1 of 100. At 1 year, satisfaction was greater than 90% for both groups. Arc of motion for OA patients improved from 44 degrees to 58 degrees . Oppositional pinch increased 126%, and grip strength improved 40%. Rheumatoid arthritis patients increased their MCP joint motion arc from 32 degrees to 45 degrees . Oppositional pinch increased 89%, but grip strength decreased. Radiographs at 1 year demonstrated stable prostheses in all of the OA joints. The RA group overall demonstrated evidence of axial subsidence (10.5% of joints) and periprosthetic erosions (16.4% of joints). In RA joints with greater than 1-year follow-up period, 55.0% had axial subsidence, 95.0% had an increased radiolucent seam, and 45.0% had periprosthetic erosions. The overall implant survivorship is 141 joints to date. The overall minor complication rate was 6%, and major complication rate was 9%. Preliminary results suggest that pyrolytic carbon MCP joint arthroplasty provides good pain relief, patient satisfaction, and functional improvement in managing OA and select cases of RA. Longer follow-up evaluation will help validate these promising early results. Therapeutic IV.

Resurfacing Arthroplasty Versus Silicone Arthroplasty for Proximal Interphalangeal Joint Osteoarthritis

To compare the outcomes of silicone proximal interphalangeal joint (PIPJ) arthroplasties to pyrolytic carbon implants in patients with osteoarthritis. This study is a retrospective review of 41 arthroplasties in 22 patients with severe PIPJ osteoarthritis performed by a single surgeon. There were 13 patients and 22 joints in the silicone group with an average follow-up of 45 months. There were 9 patients and 19 joints in the pyrolytic carbon group with an average follow-up of 19 months. Clinical assessment included range of motion, grip strength, and deformity. Radiographs were evaluated for alignment, subsidence, and implant fracture. Patients filled out a subjective questionnaire with respect to pain, appearance of the finger, and satisfaction. Complications were recorded. In the silicone group, the average preoperative PIPJ range of motion (ROM) was 11 degrees /64 degrees (extension/flexion) and the average postoperative ROM was 13 degrees /62 degrees . In the pyrolytic carbon group, the average preoperative PIPJ ROM was 11 degrees /63 degrees and the average postoperative ROM was 13 degrees /66 degrees . Eleven of 20 joints in the silicone group and 4 of 19 joints in the pyrolytic carbon group had a coronal plane deformity as defined by angulation of the PIPJ > or =10 degrees . The average coronal plane deformity was 12 degrees in the silicone group and 2 degrees in the pyrolytic carbon group. The difference was statistically significant. In the silicone group, 3 of 22 joints required additional surgery. Two implants in one patient were removed and the PIPJ fused, and one implant was permanently removed for sepsis. In the pyrolytic carbon group, 8 of 19 joints squeaked, and there were 2 early postoperative dislocations and 2 implants with radiographic loosening. To date, there has been no revision surgery. Both groups had good pain relief. Patients were generally satisfied with the appearance of their joints in the pyrolytic carbon arm; however, satisfaction with appearance was variable in the silicone group. Nine of 13 patients in the silicone group and 6 of 7 patients in the pyrolytic carbon group would have the procedure again. Both implants provide excellent pain relief and comparable postoperative ROM. Complications were implant specific. The results of this series show promise for the pyrolytic carbon PIPJ resurfacing arthroplasty but did not clearly demonstrate superiority compared with the silicone implant.

Pyrolytic Carbon Proximal Interphalangeal Joint Resurfacing Arthroplasty

To evaluate the clinical results of a pyrolytic carbon resurfacing proximal interphalangeal joint (PIPJ) arthroplasty in patients with osteoarthritis. A retrospective review of 18 PIPJ arthroplasties in 8 women with severe osteoarthritis performed by a single surgeon was completed with an average follow-up period of 13 months. Clinical assessment included range of motion (ROM), stability, and deformity. Radiographs were reviewed for evidence of loosening, subsidence, fracture, and osseointegration. Six patients, representing 16 joints, answered a questionnaire regarding pain relief, appearance, and overall satisfaction with the arthroplasty. Complications also were recorded. The average preoperative ROM was 10 degrees to 63 degrees, and the average postoperative ROM was 18 degrees to 71 degrees. Although the average arc of motion was unchanged, 9 joints had an increase in ROM and 9 joints had a decrease in ROM. All joints were stable laterally. Radiographic review indicated 2 joints with loosening at 4 months after surgery. Complications included 8 squeaky joints, 5 joint contractures, and 2 dislocations. Pain was relieved completely in 8 joints, and the pain rating on a visual analog scale was 3.6 out of 10 for the 8 patients who had residual pain. Patients were satisfied completely with the results of 9 joints. Although there was residual deformity in 4 joints, patients believed that 15 of 16 joints had improved in appearance. Five of 6 patients responded that they would have the surgery again. There have been no secondary procedures performed by us. The insertion of pyrolytic carbon implants for PIPJ arthroplasty is a technically demanding procedure, but it has the potential to achieve pain relief, stability, satisfactory ROM, and correction of the deformity; however, the results in this review were unpredictable and may not be superior to those achieved with other methods of arthroplasty. Therapeutic, Level IV.

Enhancement of the fixation of pyrolytic carbon implants by using atomic oxygen texturing

The purpose of this study was to examine the effect on the biocompatibility and biologic fixation of atomic oxygen-textured pyrolytic carbon. The implants consisted of unalloyed pyrolytic carbon rods, with half the length of the rod textured by atomic oxygen, and the other half retaining the as-deposited surface that normally occurs during the manufacturing process. The rods were implanted transcortically across the distal portion of the femurs of 6 adult male rabbits for 8 weeks. The implants were assessed mechanically by measuring the interface strength between the implant and the bone. The implant-bone interface was also examined by light microscopy. No adverse reaction to either the as-deposited or the textured pyrolytic carbon was seen. Percent bone apposition was greater for textured implants than for the as-deposited implants; however, it was not significant. The bone apposition efficiency factor, calculated by dividing the interface strength by the fraction of bone apposition, was greater for the textured implants than for the as-deposited implants. This indicates that the fixation obtained was more effective for the textured implants. The findings of this study suggest that biologic fixation of pyrolytic carbon implants can be enhanced by surface texturing by using direct exposure to atomic oxygen, without compromising its biocompatibility.

Mechanical and histological fixation of hydroxylapatite-coated pyrolytic carbon and titanium alloy implants: a report of short-term results.

Historically, pyrolytic carbon has been a material for cardiovascular applications, but it has several properties suited for orthopedic uses as well. Pyrolytic carbon has an elastic modulus similar to bone and is highly fatigue resistant, but has not been used in orthopedics because of poor fixation to bone. Plasma sprayed hydroxylapatite (HA) has significantly improved the bonding of bone to titanium alloy implants. The effect of plasma-sprayed HA on pyrolytic carbon implants was investigated in this study. Cylindrical samples were implanted through a single cortex in Beagle femurs. The animals were sacrificed after 8 weeks, and a mechanical push-out test was performed on the implants immediately after explantation. Samples were microradiographed, stained for histology, and examined histomorphometrically. Interface strength for each type of implant was calculated. Pyrolytic carbon showed almost no attachment strength with an average strength value of 1.59 MPa. HA-coated pyrolytic carbon (8.71 MPa) yielded the same interfacial strength as HA-coated titanium (8.71 MPa). Histology revealed that bone was in direct apposition to all implants, both HA coated and noncoated. Failures occurred between the core material and the coating, or within the coating, but not at the bone/HA interface. Histomorphometry results confirmed that the two types of HA-coated implants had more bone apposition than the uncoated pyrolytic carbon implants. It was concluded that a plasma sprayed HA coating significantly improves the bone fixation of pyrolytic carbon.

The effect of surface treatments on the interface mechanics of LTI pyrolytic carbon implants.

A mechanical and histological evaluation of LTI pyrolytic carbon implants was undertaken to determine the effect of various surface treatments on the retention characteristics of the implants. Five types of surfaces were evaluated, including as-deposited, fine grit-blasted, coarse grit-blasted, ground, and plasma oxygenated. The four surface treatments were chosen in an attempt to emulate the morphology of the as-deposited implants. The implants were evaluated in vivo by placement transcortically in the femora of adult mongrel dogs for periods of 12 to 24 weeks. Although the as-deposited implants exhibited the greatest interface strength at 12 weeks the results of mechanical testing after 24 weeks implantation indicated no statistically significant difference among the interface strength values or among the interface stiffness values of the implants. The histologic response of the implants was similar; while all implants exhibited areas of direct implant-bone apposition, the as-deposited implants exhibited this behavior to the greatest extent. Thus the ability to duplicate the biological response to the as-deposited LTI carbon surface appears possible by one or more of the treatments evaluated.

An Evaluation of Skeletal Attachment to LTI Pyrolytic Carbon, Porous Titanium, and Carbon-coated Porous Titanium Implants

Porous titanium, carbon-coated porous titanium, and low-temperature isotropic (LTI) pyrolytic carbon transcortical implants were placed in the femora of mongrel dogs. Mechanical and histologic analyses were performed in specimens that remained in situ for six months. Qualitative histologic results indicated that the bone formed a direct appositional interface with as-deposited LTI carbon. The bone tissue response to the two systems with porous coatings was similar. Both systems showed little fibrous tissue interposition and a high degree of mineralized bone ingrowth. The ingrown bone was well organized. However, there was some evidence that the ingrown bone mineral differed significantly from the bulk bone mineral. The only difference between carbon-coated and uncoated porous systems was a significant increase in the percentage of bone ingrowth, with carbon-coated specimens having a 4% increase in bone volume. The strength of appositional attachment to LTI carbon was shown to be at least one order of magnitude weaker than bone ingrowth attachment to the porous systems. The interface shear stiffness of the two porous systems was equivalent; however, the attachment shear strength of bone growth into carbon-coated porous titanium was significantly increased compared with that of bone growth into the uncoated porous titanium. Correlation of the percentage of bone ingrowth and pushout strength was also found to be statistically significant, suggesting that the presence of the carbon coating enhanced bone ingrowth, which resulted in significantly increased shear strengths.

Radiographic and histologic evaluation of intramedullary implants intended for biological fixation.

Three mechanisms of direct biological attachment of implants to bone were examined using femoral intramedullary implants. The implant systems studied were; low temperature isotropic (LTI) pyrolytic carbon, carbon coated porous Co-Cr-Mo alloy and 45S5 bioglass coated Co-Cr-Mo alloy. A detailed radiographic examination revealed that all three implant systems caused significant remodeling of the femurs resulting in an hour-glass appearance. The implants were also associated with a densification of cancellous bone proximal and distal to the ends of the implant. Histologically, all three implant systems exhibited a direct bone-implant bond at the majority of the interfaces. The LTI pyrolytic carbon implants were associated with a higher incidence of fibrous tissue encasement in the proximal cancellous bone region. Active bone remodeling was observed within the pores of the porous Co-Cr-Mo alloy implants even after 8 months in situ.

Comparative study of vitreous carbon, pyrolytic carbon, pyrolytic graphite/silicon-carbide, and titanium implants in rabbit mandibles

Comparative study of vitreous carbon, pyrolytic carbon, pyrolytic graphite/silicon-carbide, and titanium implants in rabbit mandibles

Comparative study of vitreous carbon, pyrolytic carbon, pyrolytic graphite/silicon-carbide, and titanium implants in rabbit mandibles

For some time, metals, plastics, and ceramics have been used for the construction of dental endosseous implants. Recently, vitreous carbon has been used, and the results have been encouraging. In a limited study using twelve New Zealand albino rabbits, vitreous carbon, pyrolytic carbon, and pyrolytic graphite/silicon-carbide implants were placed into the inferior borders of the rabbit mandibles. Titanium was used as a control, and each rabbit mandible received one each of the four materials. The experimental animals were then killed in groups of four at 14, 45, and 90 days, and the tissues surrounding the implants were evaluated histologically. All specimens revealed fibrous connective tissue capsules of varying thicknesses. Macrophages were present in some specimens, with evidence of those macrophages having phagocytized carbon particles. The conclusion reached was that none of the materials employed in this study was completely compatible with the rabbit mandibular tissues.