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PubMed1993

Motion after metacarpophalangeal joint reconstruction in rheumatoid disease.

The outcome of reconstruction of the rheumatoid metacarpophalangeal joint may deteriorate with time, especially with respect to active motion. This study assesses active finger motion after crossed intrinsic transfer and Swanson implant arthroplasty at increasing durations of follow-up to determine the effect of time. In a total of 58 patients, 21 hands had the crossed intrinsic transfer operation and 49 had the arthroplasty. Follow-up time averaged 6 years for the crossed intrinsic transfers and 21 months for the arthroplasties. Measurement of metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joint active motion at each follow-up interval were analyzed by the univariate repeated measures analysis of variance method. After crossed intrinsic transfer the overall average active range of motion decreased significantly (18 degrees) at the metacarpophalangeal joint. Proximal interphalangeal and distal interphalangeal average range of motion significantly increased during the first 5 years as a result of increases in flexion. After implant arthroplasty, the overall average metacarpophalangeal range of motion analysis at the different follow-up intervals showed that the metacarpophalangeal average range of motion significantly increased during the first 2 years and then gradually declined through the duration of follow-up. Active proximal interphalangeal flexion was also significantly increased during the first 2 postoperative years. The effects of metacarpophalangeal joint reconstruction on active finger joint motion are related to the duration of postoperative follow-up; this concept should be considered when one is planning metacarpophalangeal joint reconstruction in rheumatoid patients.

Arthritis, Rheumatoid↗
PubMed2005

Bone-cement interface of the glenoid component: stress analysis for varying cement thickness.

BACKGROUND: Although shoulder arthroplasty is an accepted treatment for osteoarthritis, loosening of the glenoid component, which mainly occurs at the bone-cement interface, remains a major concern. Presently, the mechanical effect of the cement mantel thickness on the bone-cement interface is still unclear. METHODS: Finite element analysis of a prosthetic scapula was used to evaluate the effect of cement thickness on stresses and micromotions at the bone-cement interface. The glenoid component was all-polyethylene, keeled and flat back. Cement mantel thickness was gradually increased from 0.5 to 2.0 mm. Two glenohumeral contact forces were applied: concentric and eccentric. Two extreme cases were considered for the bone-cement interface: bonded and debonded. FINDINGS: Within cement, stress increased as cement thickness decreased, reaching the fatigue limit below 1.0 mm. Bone stress was below its ultimate strength and was minimum between 1.0 and 1.5mm. Interface stress was close to the interface strength, and also minimum between 1.0 and 1.5 mm. Both the decentring of the load and the debonding of the interface increased the stress. INTERPRETATION: A cement thinning weakens the cement, but also the bone-cement interface, along the back-keel edges. Conversely, a cement thickening rigidifies the cemented implant, consequently increasing interfacial stresses and micromotions. To avoid both excessive cement fatigue and interface failure, an ideal cement thickness has been identified between 1.0 and 1.5 mm.

Bone Cements↗
PubMed2004

Stress analysis of cemented glenoid prostheses in total shoulder arthroplasty.

Glenoid component loosening is the most-frequently encountered problem in the total shoulder arthroplasty. The purpose of the study was to investigate whether failure of the glenoid component is caused by stresses generated within the cement mantle, implant materials and at the various interfaces during humeral abduction, using 3-D FE analyses of implanted glenoid structures. FE models, one total polyethylene and the other, metal backed polyethylene, were developed using CT-scan data and submodelling technique, which was based on an overall solution of a natural scapula model acted upon by all the muscles, ligaments and joint reaction forces. Material interfaces were assumed to be fully bonded. Based on the FE stress analysis, the following observations were made. (1) The submodelling technique, which required a large-size submodel and the use of prescribed displacements at cut-boundaries located far away from the glenoid, was crucial for evaluations on glenoid component. (2) Total polyethylene results in lower-peak stresses (tensile: 10 MPa, Von-Mises: 8.31 MPa) in the cement as compared to a metal-backed design (tensile: 11.5 MPa, Von-Mises: 9.81 MPa). The maximum principal (tensile) stresses generated in the cement mantle for both the designs were below its failure strength, but might evoke crack initiation. (3) The cement-bone interface adjacent to the tip of the keel seemed very likely to fail for both the designs. In case of metal-backed design, this interface adjacent to the tip of the keel appears even more likely to fail. (4) High metal-cement interface stresses for a moderate load might indicate failure at higher load. (5) It appears that both the designs were vulnerable to failure in some ways or the other. A part of the subchondral bone along the longitudinal axis of the glenoid cavity should be preserved to strengthen the glenoid structure and to reduce the use of cement.

Arthroplasty, Replacement↗
PubMed2005

Silicone implant arthroplasty in patients with idiopathic osteoarthritis of the metacarpophalangeal joint.

PURPOSE: The outcome of silicone metacarpophalangeal (MCP) joint implant arthroplasty in the osteoarthritic patient population has not been well established. Typically patients with idiopathic osteoarthritis have no history of underlying systemic disease and may respond well to treatment with MCP joint implant arthroplasty. This study examined the efficacy of silicone MCP joint implant arthroplasty for patients with idiopathic osteoarthritis for whom nonsurgical treatment had failed. METHODS: Of 14 patients (15 arthroplasties) who had silicone MCP joint implant arthroplasty for idiopathic osteoarthritis 12 (13 arthroplasties) returned for follow-up evaluation at an average of 40 months after surgery. There were 9 index finger and 4 middle finger arthroplasties. The average age at the time of surgery was 62 years. Patients completed a subjective questionnaire and were examined by a certified therapist. Range of motion and strength were recorded and the Jebsen-Taylor examination was administered to assess function. Range of motion values at final follow-up evaluation were compared with preoperative and early postoperative values. Radiographs were taken at final follow-up evaluation and compared with preoperative and early postoperative films to assess joint position, wear, and radioulnar alignment. RESULTS: At final follow-up evaluation excellent (9 patients) and good (3 patients) overall improvement were reported. Nine patients (10 implants) reported greater than 75% functional improvement. A notable increase was seen in MCP joint flexion. Grip and lateral pinch strengths were below age-matched normative data. Of the 11 patients (12 implants) who came in for follow-up evaluation 7 performed all tasks of the Jebsen-Taylor examination within the allotted time. At final follow-up evaluation all silicone implants were located and showed no signs of subluxation. Radiographic radioulnar alignment was maintained. One implant was revised at 35 months secondary to fracture. CONCLUSIONS: Silicone implant arthroplasty is a motion-sparing procedure that provides good pain relief and maintenance of function at intermediate follow-up evaluation in patients with idiopathic osteoarthritis of the MCP joint.

Aged↗
PubMed2005

Comparison of Swanson and Sutter metacarpophalangeal arthroplasties in patients with rheumatoid arthritis: a prospective and randomized trial.

PURPOSE: To perform a prospective and randomized comparison of the clinical outcome of patients with rheumatoid arthritis who had Swanson or Sutter implant replacement arthroplasty of the metacarpophalangeal joints. METHODS: There were 45 patients (3 men, 42 women) and 49 hands; a total of 75 Swanson and 99 Sutter implants were inserted. The mean time between surgery and the final follow-up control visit was 58 months (range, 37-80 mo). Preoperative and postoperative measurements were performed including active extension and flexion, correction of ulnar deviation, and strength. RESULTS: There was no statistically significant difference between groups with regard to active extension deficit correction. Mean active flexion decreased less in the Sutter group than in the Swanson group but difference between the groups was statistically significant in only the index finger. At the final follow-up examination no significant differences existed between the groups in the correction of ulnar deviation or arc of motion. Grip strengths, chuck pinch, and thump-to-fingertip grip strengths did not improve in either of the groups. CONCLUSIONS: In this study clinical results showed no significant difference between the groups with the single exception of the amount of index finger metacarpophalangeal joint flexion.

Arthritis, Rheumatoid↗
PubMedDate not supplied

Proximal humeral anatomy in shoulder arthroplasty: Implications for prosthetic design and surgical technique.

Resurfacing arthroplasty of the glenohumeral joint has been established for several decades as a means to restore comfort and function of the shoulder for many afflictions that derange the normal anatomy. Rigorous study of shoulder anatomy in terms relevant to prosthetic geometry, however, did not begin until the 1990s. It has become apparent that normal anatomy is highly variable from individual to individual and that it is aligned somewhat differently than the early modular prosthetic devices. Multiple studies have shown that retroversion is markedly variable, not only between individuals but also between the left and right sides of the same individual, ranging from 0 degrees to 55 degrees . The inclination of the proximal humeral articular surface relative to the shaft (head shaft angle) is also variable, ranging from 30 degrees to 55 degrees. The center of rotation is variably offset in 3 dimensions. The radius of curvature ranges from 20 to 30 mm and is smaller in women than in men. The thickness of the articular surface, head height, is equally variable but shows a striking proportionality to the radius of curvature. The last decade has seen a proliferation of humeral implants aiming to serve a better understanding of shoulder anatomy and function. A modern understanding of shoulder anatomy and contemporary design features is paramount for surgeons performing shoulder arthroplasty. Head size selection is dependent on multiple factors, the most important of these, other than the patient's original head size, are the osteotomy performed by the surgeon and the inclination angle(s) of the prosthetic system. Systems with variable inclination angles instruct the surgeon to resect the humeral head along the anatomic neck as best possible and then provide either adjustable or variable prosthetic geometries to match the resultant inclination angle. Other prosthetic systems have a fixed inclination angle somewhere within the normal range and instruct the surgeon to make an osteotomy at this inclination, adjusting the fit with additional preparation of the canal and revising the osteotomy as necessary. Over the last decade, most systems have offered heads that are offset by 3 to 4 mm, allowing the surgeon to dial in the most suitable position for the head on the stem. Component design and surgical technique are inextricably intertwined. Most surgeons with experience using modern systems feel a greater sense of predictability in achieving their surgical goals when using these systems as compared with earlier ones. How these developments impact implant longevity will only be known with time and further follow-up.

Arthroplasty, Replacement↗
PubMedDate not supplied

Total shoulder arthroplasty: glenoid component design.

Although Charles Neer's original glenoid component underwent several modifications, the all-polyethylene, keeled component with a radius of curvature that conformed to the humeral radius of curvature and that was implanted with cement became the glenoid implant of choice. Neer reported approximately a 30% incidence of radiolucent lines; however, only 2 of 615 glenoids were revised for loosening. Other surgeons have reported radiolucent lines in up to 90% of glenoid components and have correlated symptoms with increasing radiolucencies. This has led to the development of alternative glenoid components for unconstrained total shoulder arthroplasty. Variations in component design include component shape, articular conformity, method of fixation, and material composition. The purposes of this presentation are to review the performance of the original Neer design, as well as other more recent glenoid designs, to identify factors that may influence the performance of glenoid components, and to provide a rationale for future changes in glenoid component design.

Arthroplasty, Replacement↗
PubMedDate not supplied

Biomechanical evaluation of a novel glenoid design in total shoulder arthroplasty.

The amount of articular curvature mismatch providing optimal performance in total shoulder arthroplasty (TSA) is unknown. The objectives of this study were to quantify glenohumeral joint mechanics before and after TSA and to compare the performance of 3 glenoid components: (1) nonconforming, (2) conforming, and (3) a novel design featuring a conforming center extending into a nonconforming periphery. Six fresh-frozen cadaveric shoulders (mean age, 43 years) were mechanically tested on a custom apparatus by use of simulated muscle forces and a coordinate-measuring machine to determine joint kinematics. B-spline models of the natural and prosthetic articular surfaces were generated, and joint contact was computed by use of a proximity criterion. During both centered ( P = .02) and eccentric ( P = .05) loading protocols, glenoid contact migrated posteriorly in conforming implants. No statistical differences in kinematics and contact were found among the nonconforming design, the new design, and the natural joint. Therefore, adding a central region of conformity does not compromise the ability of nonconforming TSA components to reduce rim loading.

Adult↗
PubMed2006

Long-term results of uncemented humeral components in shoulder arthroplasty.

The purpose of this study was to determine the long-term results of uncemented humeral components in shoulder arthroplasty. We reviewed 37 shoulder arthroplasties with press-fit humeral components with a mean follow-up of 9.2 years (range, 5.8-13.6 years). The mean Constant score was 57 points (range, 16-95 points), and the results in 70% of the patients remained satisfactory. No complications or revisions occurred related to the uncemented humeral component. On radiographic analysis, none of the humeral components showed subsidence. Of the components, 22 (59%) showed radiolucency, 12 (32%) had endosteal erosion, and 5 (14%) had tilted. Of the humeral components, 7 (19%) were judged to be at risk for loosening. The prevalence of an at-risk humeral component was not associated with increasing pain or deteriorating function. This study shows favorable results with the use of uncemented humeral components in shoulder arthroplasty, with a low prevalence of clinical loosening at long-term follow-up.

Adult↗
PubMed2004

[Primary Swanson metacarpophalangeal joint arthroplasty in major hand traumas. A report of two cases at 14 years follow-up].

In major hand injuries, destroyed joints may be treated by joint transfer, arthroplasty or fusion with or without temporary external fixation. Four immediate digital metacarpophalangeal joint Swanson implants in two patients with amputation or devascularizated near-amputation were reviewed with a 14 years follow-up. No infection was noted. Prostheses were stable with a 31 degrees active range of motion and grip strength was 42% of the opposite side. Functional results were "useful" with patients satisfaction. In one patient, heavy manual worker, implants were replaced fourteen years after trauma because of recent pain on one joint and implants fragmentation. The other patient was painless. Immediate Swanson arthroplasty in major hand injuries may be an alternative in metacarpophalangeal joints destruction.

Adult↗
PubMed1983

Surgical implants. Physiological response.

Following the surgical insertion of all prosthetic implants, an identical sequence of events occurs, although the magnitude of each response is variable. Initially, to maintain hemostasis, the coagulation system is stimulated and platelet activation occurs. Within minutes, leukocytes accumulate in an attempt to neutralize the foreign body. Although these phagocytic cells are generally unsuccessful at breaking down the biomaterials comprising an implant, macrophages coalesce and wall-off the foreign body from surrounding tissues. Once the inflammatory response is quiescent, fibroblasts invade the granuloma, lay down connective tissue and contract to minimize the volume occupied by the implant. Although most implant patients experience uneventful recoveries, complications resulting from chronic activation of the inflammatory response or the mechanisms involved in maintaining hemostasis can occur.

Breast↗
PubMed1988

Enhancement of rehabilitation by use of implantable adjuncts with vascularized bone grafts for mandible reconstruction.

Restoration of mandibular continuity after trauma or cancer by means of vascularized bone grafts, as described by Taylor and coworkers in 1979, has become an established method of oral rehabilitation. Still considered by some an endpoint in reconstruction, we have found that the judicious application of newly described dental prosthetic materials can provide the patient with improved appearance and function associated with a fully restored mandible. Twelve patients who underwent vascularized bone grafting for mandibular reconstruction had adjunctive implantation to improve either dentition or to reconstruct the temporomandibular joint. Nine patients had dental implants to restore permanent stable dentition either by placement of the mandibular bone staple plate or osseointegrated implants. Three additional patients underwent placement of metallic condylar head prostheses placed on the vascularized bone graft at the time of transfer. These patients demonstrated good mastication and an excellent incisal opening which was maintained in the late postoperative period. Vascularized bone transfer for restoration of continuity of the mandible should not be considered an endpoint in and of itself. By using implantable dental devices to restore dentition and condylar head prostheses to improve both the aesthetic result and function of the mandible to complement the vascularized osteocutaneous flap, we can bring our patients closer to the goal of total rehabilitation. The majority of these patients would otherwise never have been offered a chance at restoration of dentition. All had beneficial effects with regard to mastication and the majority also had improved speech.

Biomechanical Phenomena↗
PubMed1998

Humeral technique in total shoulder arthroplasty.

Humeral head replacement arthroplasty has been performed for more than 40 years. As the technique has been refined and advances have been made in joint arthroplasty of the lower extremity, the indications and success of shoulder arthroplasty have greatly improved. The humeral component in a shoulder arthroplasty can be implanted with either cement or press fit fixation. Both techniques are precise and demand meticulous attention to detail to achieve optimum results for the patient. Press fit fixation, with or without porous coating for biologic ingrowth, can be considered for a patient with good bone stock, if it is felt that a stable interface can be obtained. In patients with abnormal bone, such as those with rheumatoid arthritis who are on corticosteroids and those with osteoporosis, the use of cement can provide stable long-term fixation.

Adrenal Cortex Hormones↗