Commonsense design of patella implant: four years of clinical experience with 124 patients.

BACKGROUND: Patella resurfacing in Total knee Arthroplasty still is an issue of controversy, that results from the statistically poor performance of patella implants. Since the basic fault of conventional designs, in our opinion, is the inadequate thickness of the polyethylene, an innovative patella was designed and rules of technique were set to optimize the surgical procedure. METHODS: Since July 1998 we have employed the new patella in 124 consecutive patients undergoing total knee arthroplasty. They had the patella routinely resurfaced with an implant of a special design of a concave undersurface and a convex (dome) articulating surface. The thickness of the entire implant was uniform at all areas of contact. The bony patella was prepared with a concave reamer and shaped into a dome with a shallow central hole. Fixation with cement gave an optimally stable implant to shear forces and resistance to wear. RESULTS: All patients were studied prospectively and followed up to five years. Results were related specifically to performance of the patella as a part of the entire joint. Two patients died from unrelated causes. Four patients had delayed wound healing. One sustained a transverse fracture of the patella already healed with minimal displacement when she came to our attention. One sustained avulsion of the patella tendon from the tuberosity, which underwent surgical reattachment. Rest pain score (10-0) improved from 5.2 to 0.5. Activity pain score (10-0) improved from 9.0 to 1.4. Walking score (0-10) improved from 3.2 to 8.2. Stairs negotiation (0-10) improved from 2.8 to 8.0 and ADL Function (0-10) improved from 4.3 to 8.2. CONCLUSION: The special technique of resurfacing of the patella was developed during a short learning period. The new design of the patella implant, eight mm thick at any point of contact gave excellent and good results in 91%. There were no intra operative complications. During five years of follow up two complication were encountered and treated successfully: a minimally displaced transverse fracture and an avulsion of the patella tendon from the tuberosity. None of the patellae components required replacement. In our opinion the new design of bio-mechanically reliable patella implant will regain confidence of surgeons who presently refrain from patella resurfacing.

Wear pattern of retrieved patellar implants.

The so-called "papillon" pattern of polyethylene wear of 17 patellar components from 5 Kinematic and 12 Total Condylar prostheses, retrieved after an average of 80 months in situ, was studied. The primary diagnosis was osteoarthritis in all cases. Four modes of damage were observed: polishing in 13 cases, delamination in 12, cold flow in 6 and scratching in 3. The median total area of polyethylene damage was 76.5% for polishing, 70.6% for delamination, 35.3% for cold flow and 17.6% for scratching. The importance of the conformity of the Kinematic patellar component in order to decrease contact stresses was confirmed. The average contact stresses on the nonconforming total Condylar patellar component (12.9 kgf/mm2), were significantly higher (p < 0.002) than the average contact stresses on the conforming Kinematic patellar component (2.9 kgf/mm2). The area of wear was smaller for the nonconforming Total Condylar (357.2 mm2) than for the conforming Kinematic patella (439.2 mm2). This difference, however, is not statistically significant. The average weight of the patients with a Kinematic Knee (74.5 kg) was higher than that of patients with a Total Condylar knee (66 kg), but the difference was not significant. The high incidence of significant wear of the patellar components indicates that a basic deficiency is present in the design of patellar implants, and calls for the improvement of two mechanical features: adequate thickness of the polyethylene implant and conforming articulating surfaces.

A comparative biomechanical study of the strength of the bony patella following dome cut or uniplanar cut in total knee arthroplasty.

This study was designed to investigate whether there is a difference in the strength of the bony patella following preparation either with a dome configuration or with a regular uniplanar cut in total knee arthroplasty. For each test 4 cadaveric patellae were used. Two of the 4 patellae were prepared with a regular uniplanar cut and 2 were prepared into a dome shape with a circumferential wall, using a concave reamer. The thickness of each patella after preparation was [figure 1 & 2: see text] 15 mm. The tests were performed using an impact drop weight apparatus. In the first two tests, which tested the resistance of the patella to tensile force and evaluated the strength of the patella by impact load while under tension, the soft tissues were torn, with no harm to the bony patella. In the third test, which evaluated the resistance of the patella without tension against impact load, the force required to fracture the dome-shaped patella was greater than for the traditional uniplanar cut (500 Kg vs 350 Kg). Dome shape with circumferential wall preparations of the bony patella in total knee arthroplasty were stronger in resisting external impact than the conventional uniplanar cut patella. This established the rationale for our use of the dome-shaped patella implant with a concave undersurface.

Histomorphometric analysis of the normal adult patella.

The patellae of 6 male and 2 female, 40 to 70 year-old individuals, who were healthy at the time of their violent death, were assessed by computer-assisted image analysis. The means of the bone density (percentage of bone in the respective field of interest) ranged from approximately 20% to approximately 30% in the central spongiotic zones, from approximately 40% to approximately 80% in the superior and inferior peripheral zones, and approximately 40% to approximately 60% in the subchondral zone. Bone densities were greatest in the lateral parts of the subchondral and spongiotic territories. The bony trabeculae were haphazardly distributed in the central spongiotic zones. They were commonly oriented vertically or parallel to the surface of the patella in the peripheral and subchondral zones. In conclusion, the histomorphometric data presented validate the rationale of reaming the articular aspect of the patella into a dome-shaped configuration with preservation of a circumferential bony bulwark in the preparation for the implantation of a thick polyethylene-based component with a concave undersurface.

The biomechamcal and surgical solutions for patella implant in total knee arthroplasty.

A basic fault in designs of patella implants that calls for a prompt remedy is the inadequate polyethylene thickness in contact areas. The requirement for thickness of patella implants should be similar to the requirement set up by the FDA in 1993 regarding the tibial implants, that is, a minimal thickness of 8 mm. A solution is presented for the optimal design of the patella implant and for the appropriate surgical technique. The implant's undersurface that fixes to bone is concave and has a 1-cm wide but 5 to 6 mm short central peg that does not risk the integrity of the bone. Fixation of the concave aspect to the convex aspect of the bony patella strongly enhances resistance to medio-lateral and supero-inferior shear forces. The circumferential facet of the implant 8 mm thick assures uniform thickness of the entire implant and assures optimal mechanical properties of the polyethylene. The articulating surface is tailored to conform to the corresponding femoral trochlear groove and condyles. It can be made to fit any femoral component of any knee implant.

Morphologic and morphometric study of patellar resurfacing with woven carbon filamentous pads.

Analysis of retrieved woven carbon filamentous pads, used for resurfacing of the patellar joint surface, disclosed a 4-zonal organizational pattern. Zone 1, facing the articular cavity, was devoid of carbon filaments and consisted of fibrous tissue. Foreign body granulation tissue and fibrous tissue occupied about one-third and approximately 50%-60% of the interfilamentous space in zones 2 and 3, respectively. Carbon filaments formed 2%-9% of zone 2 and 14%-16% of zone 3. An interfacial membrane-like zone 4 separated the carbon filamentous pads from a trabecular bony shell. The bone volume within the latter was approximately 25%. Given that the purpose of articular resurfacing with implants is repopulation of the defect by chondrocytes producing a cartilaginous matrix, the woven carbon filamentous pads did not fulfill this expectation. In an environment of an ongoing foreign body-induced granulomatous reaction, the stem cells permeating the interstices of the woven carbon filamentous pad are apparently incapable of maturing into highly differentiated cells (chondrocytes) synthesizing a highly complex (cartilaginous) matrix.

Scintigraphy of posterior tibial tendinitis.

UNLABELLED: Our goal was to describe the typical scintigraphic pattern of posterior tibial tendinitis. METHODS: Bone scintigraphs were reviewed to study the scintigraphic characteristics of posterior tibial tendinitis in nine patients with posterior tibial tendinitis related to generalized rheumatic disease and in eight patients with isolated posterior tibial tendinitis. RESULTS: The scintigraphic pattern of posterior tibial tendinitis is elongated increased uptake in the blood flow and blood-pool phase along the anatomical course of the tibialis posterior tendon at the medial aspect of the ankle (malleolus region). Static images demonstrate increased focal abnormal uptake at the medial malleolus and in the navicular bone. CONCLUSION: Bone scintigraphy depicts a characteristic pattern of posterior tibial tendinitis. It is useful for the early diagnosis of idiopathic- or rheumatic-related posterior tibial tendinitis.

Resurfacing of goat articular cartilage by chondrocytes derived from bone marrow.

The feasibility of using cartilaginous implants containing bone marrow derived chondrocytes in biological resurfacing procedures for correcting defects in articular cartilage was examined in goats. The experimental protocol included bone marrow aspiration, mesenchymal cell culturing, cell proliferation, favorable conditions inducing chondrogenic differentiation, and implantation of autogeneic and allogeneic cells. Autogeneic implant transplantations proved to be the best source for regeneration and repair of defective articular surfaces with use of densitometric computed image analysis of histochemical and immunohistochemical parameters on tissue sections. Allogeneic chondrocyte enriched cultures derived from bone marrow evoke a typical immune response in the host, expressed by the formation of fibrosis and progressive joint arthrosis. In the current study, a biological resurfacing procedure is described in detail for large mammals of similar weight and size as humans. Autogeneic mesenchymal cells derived from a bone marrow aspiration are the best cell source and when embedded in hyaluronic acid based adhesive glue make an excellent cartilaginous implant. The reparative regenerated cartilaginous tissue outcome within the defects appear different than neighboring normal articular cartilage shortly after surgery. Whether in the long term the cartilaginous remodeling process will shape the cartilage such that it more closely resembles the original articular cartilage is not known.

Histologic analysis of the periprosthetic tissues of long-term surviving cemented total hip arthroplasties.

Qualitative and semiquantitative features of the interfacial membranes of five long-term (> 16 years) surviving cemented total hip arthroplasties (four revision cases and one autopsy case) were compared with those of thirty short-term surviving (< 15 years) cemented hip prostheses. Cement granulomas, micron-sized polyethylene particles-induced giant-celled granulomas, sheets of submicron-sized polyethylene particles-laden macrophages, and aggregated, metallic particles-laden macrophages were scattered in the fibrous tissue of all interfacial membranes. Quantitatively, characteristics of the interfacial membranes of the two groups differed from one another. The dominant species of prosthetic debris in the interfacial membranes of the short-term surviving joint replacements was derived from the polyethylene acetabular socket, and, correspondingly, giant-celled granulomas and macrophagic sheets predominated. Metallic particles and the macrophagic reaction thereto dominated in the interfacial membranes of the long-term surviving arthroplasties, and large cement and polyethylene chunks typically were incorporated in the fibrous tissue of the membranes without an accompanying macrophagic response. In long-term surviving hip arthroplasties, metallic particles may be at least as important as polymeric detritus in stimulating the formation of the bone-resorbing, granulomatous interfacial membrane, which is the hallmark of aseptically loosened arthroplasties. Differences in mechanical settings may account for unlike modes and rates of generation of prosthetic breakdown products, explaining the disparate survivorship of different patients' artificial joints.

Bone scintigraphy findings in Lisfranc joint injury.

Three-phase bone scintigraphy diagnosis of Lisfranc injury in a patient after foot trauma is discussed. Early diagnosis of Lisfranc joint injury is frequently missed and radionuclide bone scintigraphy may show a specific pattern where the x-rays are inconclusive.

The relativity of biocompatibility. A critique of the concept of biocompatibility.

The concept of biocompatibility of the materials used in surgical reconstruction of joints, ligaments, and tendons is controversial, as evinced by the conflicting definitions proposed by the many authors who have studied the host reaction to the presence of implants and their breakdown products. We propose that biocompatibility of contemporary medical implants is not a property of the chemical composition of the biomaterials but depends rather on their physical attributes. The histological reaction patterns of tissue to the presence of polyethylene in diverse physical states are described. The inflammatory response evoked by the implants is laudable in so far as it precedes and accompanies the adequate tissular incorporation of the devices used. On the other hand, the granulomatous reaction induced by small, irregularly shaped and edgy breakdown products adversely affects the life span of the implants. Thus the manner in which the host handles the biomaterials is determined primarily by the physical state of the biomaterials (rather than their chemical composition), which in turn determines the success or failure of reconstructive surgery. It logically follows that biocompatibility constitutes a relativistic concept.

Remodeling of the calcaneus apophysis in the growing child.

Radiography and computer-aided analysis of tomography of the os calcis in 35 children with Sever's disease and of 52 control children were concurrently evaluated with histologic appearance of six calcanei of victims of road accidents, which were radiographically compatible with the same syndrome. Histology showed abrupt interruption in continuity of the apophysis of perpendicular fibrous plates with evidence of an ongoing reparative process. Computer-aided analysis of orientation of the "fragmentation" lines and histologic data both support the hypothesis of a stress remodeling process owing to excessive bending forces acting on the calcaneal apophysis.

The histologic features of the interfacial membrane of intramedullary nails.

Thirty-six interfacial membranes collected at the time of removal of intramedullary L316 stainless steel nails were studied histologically. The membranes consisted of bland fibrous tissue in a minority of cases. Most often, the nails were enclosed within a synovial-like membrane. Palisading macrophages and fibroblasts abutted on the metallic surface of the nails. Foreign body giant-celled granulomas were scattered in the midzone of the membranes, mono- and polykaryonic macrophages having phagocytozed small metallic particles, necrotic bony debris, and, sometimes, lipidic compounds. Aggregates of hemosiderin-containing macrophages occasionally marked the sites of previous hemorrhages. When present in the retrieved specimen, the bone underlying the membrane was undergoing remodeling. Interfacial motion, consequent on dissimilar stiffness of the bone and nail, as well as deposition of metallic and bony debris, are likely responsible for the formation of the synovial-like interfacial membrane.

[Stabilization double osteotomy of the knee].

Stabilization osteotomy of the knee is a single or double 1-stage osteotomy done to correct ligamentous deficiency of the knee. The concept of stabilization osteotomy depends on the residual ligamentous and capsular tissues which envelope the circumference of the joint. The technique relies on open wedge osteotomy to restore alignment of the joint. Satisfactory results in 6 patients who underwent stabilization osteotomy as a salvage procedure during the past 5 years encouraged us to publish the principles of this concept.

The nature of the bone-implant interface. The lessons learned from implant retrieval and analysis in man and experimental animal.

The morphological appearances of the interface between the bone and the components of arthroplasties depend on multiple factors. Present-day biomaterials being biocompatible when in bulk form, a host reaction consequent upon untoward effects of the implants as such is not expected. Thus, osseointegration, i.e., the direct apposition of bone to the surface of a foreign material at the light microscopical level, occurs, under favorable biomechanical circumstances, irrespective of the chemical composition of the implant. Osseointegration is a multifaceted phenomenon. First and foremost, it evolves when an initially rigid fixation of the component is surgically attained. Interfacial motions are associated with resorption of the bony bed, macrophagic activation and production of wear particles, the close bone-implant apposition is lost and the formation of an interfacial membrane (IM) ensues. The histological features of the IM coincide with the context of its formation and evolution. The quiescent IM is composed of a thin layer of fibrous tissue and its occurrence is compatible with the biofunctionality of the implant. The aggressive or lytic IM (LIM) develops when tissue-irritating, small, irregularly shaped and edgy breakdown products are deposited at the interface. The thick LIM consists of an inflamed fibrous tissue, scattered within which are myriad granulomas, and its surface facing the implant displays a synovial-like aspect. The mono- and polykaryonic macrophages, constituting the granulomatous response, ingest and abut on the wear particles. Amongst the intermediary substances of inflammation elaborated by the lymphocytes and macrophages of the LIM, factors which stimulate the osteoclasts play the pivotal role in as much as progressive bone resorption is associated with progressive growth of the IM and, hence, with incremental interfacial motion, interfacial deposition of wear particles and inflammatory-granulomatous response. The ensuing vicious circle culminates in aseptic loosening of the arthroplasty. The morphological features of the LIM, though characterized by a stereotypical reaction pattern, are, in their details, closely linked with the nature of the diverse components of the composite joint replacement. The histological appearances of the bone-implant interface of stable and loose arthroplasties, the tissular reactions to polymethylmethacrylate, polyethylene, polyacetal, metals and hydroxyapatite as well as the characteristics of cemented and cementless porous-coated, press-fit and hydroxyapatite-coated prostheses are described.

Bone defect healing in the absence and presence of a plastic catheter: an experimental study in the rabbit.

The healing pattern of small, round, cortical defects, drilled in the upper tibial diaphysis of rabbits, was studied histologically and histomorphometrically. Group I rabbits were not further handled. In groups II and III animals, a polyethylene catheter was introduced into the medullary cavity by way of a second cortical hole and driven forward until its tip was close to the first cortical defect. Group II rabbits were not further handled. The cortical defect of group III animals was irradiated from a diode source via a fiber optic cable in the catheter. Assessment of the osseous healing of the cortical defects revealed neither qualitatively nor quantitatively significant differences among the three groups. The morphological catheter, which abuts on a cortical defect, does not hinder the normal progression of osseous bridging of the gap.

Studies on a novel anterior cruciate ligament polyethylene fiber prosthesis: the histomorphological pattern of organization and bony anchorage of a polyethylene fiber prosthesis in the stifle of the goat.

The anterior cruciate ligament of goats was substituted by a high-tensile polyethylene fiber prosthesis. The animals were sacrificed after 6-12 months. Histologically, the implants were separated from a newly formed bony shell by a thick fibrous interface membrane, which was anchored to the bone by Sharpey-like fibers. Within the joint cavity, the implants were enclosed in thick fibrous sheaths, which were continuous with the intra-osseous interface membranes. While the inner granulomatous layer of the interface membrane extended in between the polyethylene fibrils for a short distance, the bulk of the prosthesis was poorly organized. A thick central fibrous band accompanied the intra-osseous and intra-articular portions of the implants throughout their entire lengths. Oblique fibrous tracks linked the interface membranes with the central fibrous bands. The intra-osseous tunnels were considerably expanded when compared to the initially drilled tunnels.

Implants composed of carbon fiber mesh and bone-marrow-derived, chondrocyte-enriched cultures for joint surface reconstruction.

The current study integrates two distinct approaches in joint resurfacing into a combined type of implant, composed of carbon fiber mesh impregnated and coated with a hyaluronic-acid-based delivery substance containing cultured cells. Rabbit autogeneic chondrocyte-enriched cultures obtained from mesenchymal stem cells (chondroprogenitor cells) derived from adult rabbit bone marrow were grown in vitro under conditions favoring chondrogenesis. The improvement in quality of repair when a combined implant containing both cells and a carbon scaffold was used, in comparison to the utilization of carbon fiber mesh alone, was clearly demonstrated using clinical, histological, biochemical, and biomechanical examinations. Evaluations of the joints were performed at 6 weeks and 6 months after implantation. The repair tissue in the cell-implanted joints consisted of a typical hyaline cartilage, which was more cellular and thicker than the repair tissue in the hyaluronic-acid-impregnated carbon-fiber-implanted control joints. The hyaline cartilage in the experimental group formed a superficial layer above the carbon fibers, flush with the joint surface. In the controls, in which carbon fiber and the delivery substance alone were implanted, a histologically and biochemically fibrous tissue that was inferior biomechanically to the new cartilage was formed by the cells containing implants.