Flexible Implant Arthroplasty in the Hand

A Systematic Review of Compliant Mechanisms as Orthopedic Implants

Currently available motion-preserving orthopedic implants offer many advantages but have several limitations to their use, including short device lifetime, high part count, loss of natural kinematics, and wear-induced osteolysis and implant loosening. Compliant mechanisms have been used to address some of these problems as they offer several potential advantages - namely, wear reduction, reduced part count, and the ability to achieve complex, patient-specific motion profiles. This article provides a systematic review of compliant mechanisms as orthopedic implants. Based on the PRISMA guidelines for an efficient review, this work identified fourteen implantable orthopedic devices that seek to restore anatomical motion by utilizing mechanical compliance. From reviewing these implants and their results, advantages and consequences for each are summarized. Trends were also identified in how these devices are capable of mitigating common challenges found in orthopedic design. Design considerations for the development of future compliant orthopedic implants are proposed and discussed.

[Revision surgery after total wrist arthroplasty]

BACKGROUND

Wrist arthroplasty is still an exceptional indication in the field of hand surgery. In recent years, it has become increasingly accepted as an alternative to wrist arthrodesis as the ultima ratio for panarthrosis or similar destruction of the wrist. In particular, the patient's desire for functional integrity also plays an important role.

COMPLICATIONS

While there were often complications with earlier prosthesis designs of the older generations and only a short survival rate could be achieved, this has improved, if the indication of the so-called fourth generation prostheses is done properly. Survival rates of over 10 years are no longer uncommon, even without revision operations. Currently, the indication for hemiarthroplasty has been increasing, particularly in the case of post-traumatic destruction. Those who are seriously interested in endoprosthesis should also be able to treat the associated complications. The present article is intended to provide an overview of common or potential complications in the context of wrist arthroplasty and to demonstrate possible solutions by presenting case studies. The basics of primary implantation are, therefore, not discussed. Reference is made to further literature.

Total wrist arthroplasty

This article reviews the history of total wrist arthroplasty as a treatment option for painful, nonfunctional wrists in disease states. Technologic advances in materials, wear properties, and manufacturing now account for increased implant longevity. They may also improve total wrist replacement design, survival, and hence patient function. Also, alternative surgical treatments such as distal radius hemiarthroplasty may serve as a treatment option for patients with higher activity levels and diffuse arthritis. With careful patient selection, soft tissue considerations, and novel implant designs, TWA may become a viable treatment staple for patients with functional wrist disability.

Flexible implant resection arthroplasty of the proximal interphalangeal joint in patients with systemic inflammatory arthritis

Forty proximal interphalangeal joint silicone elastomer flexible implant arthroplasties in 19 patients with systemic inflammatory arthritis were reviewed. The follow-up period averaged 94 months. Before surgery, the average arc of motion was 26 degrees for the 20 digits with boutonniere deformities and 23 degrees for the 16 digits with swan-neck deformities. Eight digits had moderate (grade 2) pain, and four digits had severe (grade 3) pain. After surgery, the deformity was completely corrected in six digits. Digits with a preoperative boutonniere deformity (20 digits) achieved the same (26 degrees) arc of motion after surgery, whereas those with a preoperative swan-neck deformity (16 digits) actually lost 18 degrees. Six digits had moderate pain and one digit had severe pain at the final follow-up evaluation. Thirteen digits (7 patients) with a boutonniere deformity before surgery and a concurrent or previous silastic metacarpophalangeal arthroplasty had significantly better results than those without. Overall, there were 12 good, 18 fair, and 10 poor results. Based on this study, flexible silicone implant arthroplasty has a limited role in the treatment of proximal interphalangeal joints affected by systemic inflammatory arthritis. When performing the arthroplasty, attention should be directed first toward correction of the deformity at the metacarpophalangeal joint.

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.

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.

Silicone synovitis of the wrist

Foreign body giant cell synovitis and focal bony destruction requiring secondary surgery developed in nine patients after carpal and radiocarpal arthroplasty with silicone rubber implants. Synovitis followed silicone rubber replacement of the lunate in four patients, the carpal scaphoid in two patients, and the trapezium in one patient, trapezial resurfacing hemiarthroplasty in one patient, and total wrist arthroplasty in one patient. All the removed implants were deformed. Some had changed in color from clear white at the time of insertion to yellow-white or deep yellow upon removal. Scanning electron microscopy of a silicone rubber implant of the lunate removed from one patient revealed extensive fibrillation in the capitate fossa. Light microscopy of the synovium revealed hyperplasia and hundreds of fragments of silicone particulate debris throughout the tissue adjacent to the implant. The silicone debris was surrounded by multinuclear foreign body giant cells in the eight patients from whom the synovium was studied. All patients required revision surgery. We believe that in the patients studied, synovitis represented a biologic reaction to the silicone fragments found scattered throughout the synovium for the following reasons: The synovitis found was not present before surgery (except in the patient with rheumatoid arthritis); the synovitis found was not associated with the condition for which replacement arthroplasty was performed (except in the patient with rheumatoid arthritis); synovitis subsided after implants were removed; and synovitis was noted histologically in areas of silicone debris and appeared directly related to silicone seeding. Fibrillation, fragmentation, and local seeding of silicone after carpal or radiocarpal arthroplasty appear related to gradual deformation of the implant, which was the result of repeated compressive loading and shearing. Clinically significant complications of rubber carpal or radiocarpal arthroplasty with silicone rubber implants may develop from silicone synovitis.

A new approach to the fixation of a metacarpophalangeal joint prosthesis

A significant problem with rigid prosthetic stems applied in the finger bones, as well as in other bones of the upper and lower extremity, is resorption of bone at the interface. An investigation was carried out using a plastic plug which would more evenly distribute the stresses to the bone, with fine ridges to produce enhanced fixation by bony ingrowth. A total knee prosthesis in the cat was used as the model, radiographic and histological studies being made at up to one year. A finite element analysis identified areas of high interface and material stresses. With a finely grooved plug, bone ingrowth occurred in all regions except for the region near the bone entry, where the finite element analysis showed the highest interface shear stresses and bone material stresses to occur.

Perichondrial arthroplasty in the hand: a case report

A two-stage arthroplasty technique was used to treat an isolated fibrous ankylosis that developed in the index metacarpophalangeal joint of a 14-year-old boy after a rattlesnake bite. The first stage consisted of a minimal joint resection combined with rib perichondrial grafts to resurface the joint. The second stage, performed 5 months later, consisted of a capsulotomy and removal of a silicone membrane left within the joint to separate the grafts. Biopsy of the joint surfaces revealed the presence of hyaline-like cartilage. Nearly normal pain-free motion was restored. Follow-up now exceeds 30 months.

Trapezium implant arthroplasty. Long-term evaluation of 150 cases

Arthritis of the joints at the base of the thumb can be painful and severely disabling, interfering with normal functional activity. The trapezium implant, which acts as a replacement for the removed pathologic bone, must have certain features if it is to be tolerated by the host tissue and be stable and durable. Implant resection arthroplasty of the trapezium, with careful correction of other associated deformities, has resulted in long-term, excellent functional and cosmetic results in this group of cases.

Ligament augmentation with replacement arthroplasty of the carpo-metacarpal joint

A method of ligament augmentation at the time of Swanson silicone replacement arthroplasty of the trapezium is presented. This has effectively solved the problem of prosthetic dislocation. One of the twenty-six patients had a prosthesis dislocate and this was felt to be due to improper positioning of the thumb post-operatively. A successful closed reduction and subsequent prosthetic stability was achieved. All twenty-six patients had stable and pain free thumbs with good range of motion.

Experience with Silastic prostheses in the rheumatoid hand. A 5-year follow-up

Nine patients with rheumatoid arthritis, who had Silastic prostheses (Swanson's) introduced into 34 metacarpophalangeal joints, were reviewed 5 years after surgery. The most important long-term advantage conferred by the introduction of prostheses was pain relief; functional benefit was marginal. The majority of prostheses eventually fractured but this did not necessarily lead to a functional deterioration. Impairment of function was usually the result of loss of flexion at the metacarpophalangeal joints, but it was sometimes due to excessive instability after fracture of the prostheses. It is suggested that Silastic joint replacement may be a worthwhile procedure in rheumatoid patients with moderate destruction or deformity of the metacarpophalangeal joints when pain is a predominant feature. Significant functional improvement can be anticipated only when secondary to pain relief.

The use of the Flatt hinge prosthesis in the rheumatoid thumb

Nine patients with marked destruction in both the metacarpophalangeal and interphalangeal joints of the thumb, were treated with fusion of the interphalangeal joint and insertion of the Flatt hinged metal prosthesis into the metacarpophalangeal joint. Of the nine thumbs treated in this manner, eight had good to excellent results. One prosthesis was removed after it became infected, leaving both joints fused.

Interposition arthroplasty of the carpo-metacarpal joint of the thumb

Nine patients with osteoarthrosis of the carpo-metacarpal joint of the thumb were treated surgically with the metacarpo-trapezial silicone rubber prosthesis designed by Kessler. Patients with pantrapezoidal changes were specifically excluded. All patients at follow-up had chronic synovitis and in five the prosthesis was dislocated. In three patients who had revision operations the previously inserted prostheses were found to be badly torn.