Implants designed for finger joints. A roentgenorgraphic study and a study of implant wear and tear

Implant arthroplasty of the hand: retrospective and prospective considerations

Small joint arthroplasty has lagged behind the development of that in large joints because of their small sizes, different shapes, presence within kinetic chains, complex soft tissue investments, presence of adjacent rays, secondary displacement and contracture, and the differing requirements of degenerative and rheumatoid arthritis. Prosthetic development must take into consideration range of motion, stability, tendon moment arms, fixation, ease of implantation, biocompatibility, wear and strength characteristics, and soft tissue reconstruction. The metacarpophalangeal, interphalangeal, and trapeziometacarpal joints each present different problems in the design of kinematic equivalent prostheses. One-piece polymeric designs have advantages in cost, adaptability, and known performance but show degradation of function with time. Total joint designs have the potential of better simulating normal joint function but have shown tendencies to subsidence, loosening, and breakage. The rigidity of hinge joints limits the damping of out-of-plane forces and places greater stress on bone-stem interfaces, whereas global designs have poor constraint features.

Development of a surface replacement arthroplasty for proximal interphalangeal joints

Sixty-six surface replacement proximal interphalangeal prostheses with a CrCo proximal and an ultrahigh-molecular-weight polyethylene distal component were used in the hands of 47 patients (mean age, 58 years) over a 14-year period. There were 37 fingers with degenerative arthrosis, 16 with traumatic arthrosis, and 13 with rheumatoid arthritis. The mean follow-up period was 4.5 years (range, 1-14 years). The results based on pain relief, motion, and deformity were good in 32 fingers, fair in 19, and poor in 15. Poor results occurred primarily in fingers with previous extensive injury or static deformity. Results with a dorsal approach were better than those with a lateral or palmar approach. Component loosening at the bone-cement junction beyond a minimal radiolucent line was seen in one late x-ray. Results in individuals changed little after the first year of follow-up care, but results overall improved during the course of the study, perhaps because of improvements in surgical technique and experience.

Autograft replacement of small joint defects in the hand

Intraarticular injuries to the small joints of the hand with attendant loss of cartilage can result in the development of posttraumatic arthritis with functional disability due to pain and loss of motion. Traditional treatment options often have yielded suboptimal results in terms of functional return, particularly when applied once contracture or arthritic change already has developed. Acute management of cartilage loss by osteochondral reconstruction with restitution of the articular surface may diminish the likelihood or severity of potential post-traumatic degenerative changes.

Materials testing protocol for small joint prostheses

In this article, a protocol for the evaluation of new materials for small joint prostheses is introduced. The testing methods employed in the protocol were developed by reviewing reported clinical failure modes and conditions found in vivo. The methods developed quantitatively evaluates the fatigue, fatigue crack propagation, and wear resistance properties of materials. For this study, a silicone elastomer similar to Dow Corning Silastic HP100, a radiation stable polypropylene, and a copolymer of polypropylene and ethylene propylene-diene monomer (EPDM) are evaluated. None of the materials tested demonstrated the ideal properties that are sought in a self-hinging joint prostheses. The silicone elastomer had excellent wear properties; however, cracks quickly propagated, causing catastrophic failure when fatigued. Conversely, the copolymer showed excellent fatigue crack propagation resistance and less than favorable wear properties. The polypropylene did not perform well in any evaluation.

In vivo experimental analysis of silicone implants on bone and soft tissue

We report experimentally produced silicone microparticles (synovitis) in 47 white rabbits and discuss the implications for clinical practice. Silastic HP100 (Dow Corning Wright, Arlington, TN) finger hinges (size 5) were inserted in 20 rabbit's knees. The upper tibia was replaced with Swanson design great toe implants in another 15 rabbits; articular cartilage was removed and endosteal drilling was performed in 6 animals as a "sham" arthroplasty. Small silicone blocks were inserted in the proximal tibial endosteal canal of 6 others. Animals were followed by monthly x-ray films and killed at 2, 4, 6, 12, and 16 months. Implant wear, bone surfaces, and soft tissue were examined under the operating microscope and by light microscopy; implant surfaces were examined with scanning electron microscopy. X-ray changes included reactive endosteal bone formation around implant stems as early as 1 month postoperatively; at 2-3 months the new bone line was clearest but it became progressively homogeneous and less evident. Extensive cortical erosion around the stems was observed in one third of the animals. Neither ossification nor lysis was observed around the silicone block. Proliferative synovitis was found at post-mortem examination beginning after 4 months; femoral condylar erosions were observed in most animals after 12 months. Wherever there was bone destruction, silicone particles were confirmed by x-ray spectrography.

In vivo experimental analysis of silicone implants used with titanium grommets

This study evaluated the titanium grommets recommended to reduce breakage by protecting hinge implants from bone edges. Silastic HP-100 (Dow Corning Wright, Arlington, TN) flexible finger implants (size 5) were used to replace one knee of 10 rabbits, and implants plus titanium grommets were used in another 10. X-ray films were taken monthly; deaths from each group were 1 animal at 2 and 4 months, 2 animals at 6, and 3 each at 12 and 16 months. X-ray films revealed that 4 of 10 implants from each group had fractured. Silicone fractures occurred identically at the proximal stem-hinge junction in both groups, destruction was always most pronounced at the dorsal surface of the proximal stems. The time from surgery to x-ray film evidence of implant fracture without grommets was an average of 9 months and with grommets 13 months. Although grommets delayed x-ray film evidence of fracture onset, after 14 months all implants in both groups of animals fractured. These findings do not support the hypothesis that grommets prevent silicone hinge implant wear or fracture in this experimental model.

Metacarpophalangeal joint prostheses: a review of past and current designs

The anatomy and biomechanics of the metacarpophalangeal (MCP) joint are briefly described. Hinge, flexible and surface designs of past and current MCP prosthetic joints are reviewed, outlining their respective advantages and disadvantages. Although existing prostheses can restore cosmetic appearance and relieve pain, none can equal the stability and versatility of the natural joint. Delayed reconstructive surgery may be partly responsible for the mediocre results experienced, since the later the surgery the worse will be the condition of the muscles and ligaments surrounding the joint. These are the structures responsible for strength, movement and stability of the joint. From a mechanical viewpoint it may be desirable to operate at an earlier stage of the disease than is currently indicated, but this is a clinical decision. Some design aspects, namely fixation and wear, require a different approach when designing an MCP prosthesis from that adopted in the case of prosthetic hips and knees.

Osteochondral metatarsophalangeal autografts for traumatic articular metacarpophalangeal defects: a preliminary report

Five consecutive patients with saw injuries to the dorsal portion of the index metacarpophalangeal joint and resultant partial osteochondral defects underwent articular reconstruction using contoured metatarsophalangeal osteochondral autografts. At an average follow-up period of 33 months, all patients achieved full metacarpophalangeal extension, with 74 degrees of flexion and grip strength equal to 86% of the contralateral hand. Discomfort was minimal, with crepitus present in one patient. X-ray films revealed joint space narrowing or articular step-off of 1 mm or less.

Segmental metacarpal replacement with bone cement and a silicone joint prosthesis: a case report

The replacement of the distal half of the third metacarpal and the metacarpophalangeal joint with bone cement and a silicone implant is reported. Eight years after surgery, x-ray and clinical examination revealed no evidence of instability or material failure. The active and passive range of motion in the reconstructed metacarpophalangeal joint was 35 degrees, and the hand was free of pain.

Pathologic fractures: a complication of microparticulate synovitis

We report seven cases of pathologic fracture in adult patients that were seen an average of 5 years (range from 33 to 114 months) after silicone wrist (three) and trapezial (four) arthroplasty. All patients had initially done well after their operation. At return, all had radiographic evidence of generalized implant and intramedullary bone destruction, the latter always including endosteal scalloping and widening from cortical resorption. These radiographic changes may be less striking than the discrete osteolytic lesions seen after degeneration of carpal implants. Our patients represent examples of pathologic fracture as the end stage of untreated microparticulate synovitis, a consequence of prosthetic wear. Our experience suggests that careful and continuous follow-up justified after insertion of stemmed silicone implants, and that patients should be informed of the potential late complications of this procedure, including pathologic fracture.

Silastic Replacement of the Trapezium for Arthrosis—A Twelve Year Follow-Up Study

Thirty-three patients with 39 Swanson silastic trapezium implants have been studied. Three years after operation no dislocation or evidence of implant wear was found, but re-examination at an average of 12 years after operation revealed dislocations and implant wear in about half of the cases. Cyst formation in surrounding carpal bones was found in twenty cases. The result in terms of pain relief and thumb function was good and comparable to the three-year follow-up. A significant correlation was found between weakness of the pinch grip and dislocation of the implant. No correlation was found between pain and dislocation of the implants, nor between pain and presence of intraosseous cysts.

Reactive synovitis after silicone arthroplasty

A number of patients with silicone rubber implants performed by us and other surgeons initially had excellent results; however, they returned with swelling and discomfort. We studied 18 patients ranging in age from 16 years to 57 years who presented 8 to 78 months (average, 31.7 months) after silicone arthroplasty (four scaphoid, six lunate, one scapholunate, four finger, two wrist, one trapezium, and one ulnar head for metacarpal hemiarthroplasty). Erosive osteolysis was seen on x-ray films, with progressive destruction evident in patients followed serially. None of the patients' conditions responded to conservative care. The severity of the proliferative, inflammatory synovitis and the foreign material in the multinucleated giant cells correlated with the interval since arthroplasty. Implant surface analysis by scanning electron microscope and x-ray spectrometer showed that silicone microparticles were the result of implant degeneration and erosion. All joint cultures were negative. Silicone particulate synovitis and destruction were arrested by the removal of the implant, a synovectomy, and curettage of the lytic lesions at salvage (resection arthroplasty or arthrodesis). Patients who have had silicone arthroplasties should be followed indefinitely, at regular intervals, by x-ray films and clinical examination.

Swanson implant arthroplasty of the wrist in rheumatoid arthritis

Sixty rheumatoid wrists operated with Swanson implant arthroplasty were evaluated after a mean observation time of thirty-three months. Grip function in daily living improved in 60%, pain decreased in 88%, range of motion increased in 83% and grip strength increased in 69% of operated wrists. Significantly impaired function was found in wrists with implant fracture (12%) and in cases with pronounced bone resorption around the implant (23%). Ulnar deviation and carpal collapse were commonly found but did not impair the function significantly. In seven patients the contralateral wrist had been fused and was compared to the arthroplasty. The merits and indications of arthroplasty are discussed.

Re-alignment procedure for ulnar drift of the metacarpophalangeal joint in rheumatoid arthritis

An operation for correcting ulnar deviation in rheumatoid arthritis, by employing local tendon transfers at an early stage in the developing deformity, is described. The pathology, clinical staging and results in 103 joints are presented.

Metacarpophalangeal joint implants. II. Roentgenographic study of the Niebauer--Cutter Metacarpophalangeal Joint Prosthesis

A roentgenographic study was carried out on 41 Niebauer -- Cutter Metacarpophalangeal Joint Prosthesis from 1 to 36 months postoperatively, a total of 105 examinations. The examinations were performed in the AP-projection and in the lateral projection by tomography in maximum active extension and flexion. The tomographic examinations revealed implant damage of three kinds: cracking within the midsection; fragmentation of the midsection; fracture of the hinge. Cracking within the midsection was found in 8 implants between 6 and 12 months postoperatively and in 1 implant later than 12 months. Later examinations revealed fragmentation of the midsection in 2 implants previously showing cracks. Hinge fracture was observed in 22 implants. Implant damage was found in a total frequency of 26/41. Bone reaction was found on the tomograms in all the operated joints, and could not be evaluated on the AP-projections. A bony spur was found to develop on the metacarpal bone volarly at the site of the osteotomy in 35 joints. In 2 of these the bony spur reached the base of the proximal phalanx, causing anchylosis. Bone resorption was found in 23 joints, constantly dorsally in the metacarpal bone and volarly in the proximal phalanx. The mechanism of the implant damage is discussed with respect to the shearing forces in the joint and the two materials of differing elasticity constituting the implant. The bone reaction is discussed with respect to the intended fixation of the intramedullary stems.