Twenty-year evaluation of meniscal bearing and rotating platform knee replacements.

Clinical results of the initial cemented and cementless series of 373 New Jersey Low Contact Stress total knee replacements in 282 patients surviving at least 10 years were analyzed using a strict knee scoring scale. The study showed excellent, good, fair, or poor results in 68.1%, 29.8%, 2.1%, or 0% of primary posterior cruciate-retaining meniscal bearing knee replacements, 46.7%, 53.3%, 0%, or 0% results in primary cemented rotating platform knee replacements, and 68.1%, 29.8%, 2.1%, or 0% results in primary cementless rotating platform knee replacements, respectively. Radiographic evaluation at minimum 10-year followup showed stable fixation of all components, no gross migration but significant osteolysis requiring bearing exchange and bone grafting in three cementless rotating platform knee replacements (1.8%) in three patients who underwent previous surgeries at an average of 10.2 years from the index surgery. Survivorship of the patients who underwent primary cementless posterior cruciate-retaining meniscal bearing knee replacements with an end point of revision for any mechanical reason was 97.4% at 10 years and 83% at 16 years; using an end point of a poor clinical knee score the survivorship was 98.9% at 10 years and at 16 years. Survivorship of the patients who underwent primary cemented rotating platform knee replacements with end points of revision for any mechanical reason or a poor clinical knee score was 97.7% at 10 years and at 20 years. Survivorship of the patients who underwent cementless rotating platform knee replacements with end points of revision for any mechanical reason or a poor clinical knee score was 98.3% at 10 years and at 18 years.

Combined saphenous vein with free flap reconstruction in the treatment of carotid stenosis.

Revascularization for arterial stenosis in varied anatomic sites exposed to therapeutic radiation has been well described. In most circumstances, symptomatic end organ ischemia has been the indication for surgical intervention. We report the case of a patient who had symptomatic carotid stenosis 40 years after having ipsilateral neck dissection with radiation therapy. We did a saphenous vein graft interposition and free flap reconstruction of the overlying damaged skin.

Titanium nitride ceramic film against polyethylene. A 48 million cycle wear test.

Wear is a major late complication of total joint arthroplasty, particularly for younger, active patients. Many patients could produce > 40 million motion cycles after joint replacement. Based on current experience and testing, typical joint prostheses are likely to wear out, and need revision in such patients. One problem is degradation of the metal (counterface) surface. A harder, more abrasion resistant, counterface surface is needed. This study evaluated the long-term wear of the titanium nitride ceramic film against ultra high molecular weight polyethylene. In this test, 4 47-mm femoral cups with a polished 8-micron-thick titanium nitride coating were run against 4-mm-thick metal-backed polyethylene bearings machined from GUR415 extruded rod in water at 37 degrees C at 5 Hz and a 2200-N fluctuating load. Wear of the counterface and bearing were extremely low. The average maximum reduction in thickness of the polyethylene was < 0.02 mm, and < 2 microns in the ceramic film. The average polyethylene wear rate was only approximately 2% of that found in a similar test using 32-mm cobalt chromium femoral heads. The titanium nitride-polyethylene couple has great potential as a lifetime bearing combination.

Survivorship and clinical evaluation of cementless, meniscal-bearing total ankle replacements.

A porous-coated, cementless, congruent-contact, meniscal-bearing total ankle replacement with a centrally placed trochlear groove and a cylindrical articulating axis representing the lateral talar curvature was developed and used clinically over a 10-year period. An initial clinical series of 40 ankle replacements involved the use of cobalt-chromium-molybdenum tibial and talar components with sintered-bead porous coating of 275-mum pore size and a shallow-sulcus trochlear groove with a central fixation fin for the talar onlay component. The congruent meniscal bearing, made of ultrahigh molecular-weight polyethylene (UHMWPe), was flat superiorly and matched the shallow-sulcus and cylindrical geometry inferiorly. Two bearings in two patients subluxed laterally and required revision within 2 years. The overall cumulative survival at the 10-year interval for this group using revision as an end point was 94.75%. The clinical results, using a strict ankle evaluation scoring scale, demonstrated 85% overall good to excellent results. Three patients required further treatment for intermalleolar exostoses, one patient required a debridement for infection, two ankles had medially subluxed bearings, eight ankles developed talar component subsidence, and two patients suffered from chronic reflex-sympathetic dystrophy. A second clinical series of 14 ankle replacements involved the use of polished titanium-nitride-coated titanium-6 aluminum-4 vanadium tibial and talar components with sintered-bead porous coating of 350-mum pore size and a deep-sulcus trochlear groove with two lateral fixation fins for the talar onlay component. The bearing element was similar to the initial series except that it had a deeper engagement in the trochlear groove to prevent subluxation.(ABSTRACT TRUNCATED AT 250 WORDS)

Evaluation of contact stress in metal-backed patellar replacements. A predictor of survivorship.

Significant wear-through and dissociation failures of metal-backed, point and line contact patellar replacements are associated with excessive contact stresses on the polyethylene-bearing surfaces. Analytical mathematical contact-stress analysis was used to evaluate various patellar component geometries under loading conditions consistent with walking, stair descent, and deep knee bends, respectively. Typical point- and line-contact patellar-surface geometries exceeded the manufacturer's recommended maximum permissible compressive stress level of 10 MPa by a factor greater than three, which also exceeds the yield stress of ultra-high, molecular-weight polyethylene. A metal-backed, rotating-bearing, area contact geometry patellar replacement maintained safe contact stress levels at less than half of the maximum permissible compressive stress level. These contact stress analyses predict early fatigue failure of all-polyethylene or metal-backed, point- and line-contact patellar replacements, while predicting long-term survival of area-contact, rotating-patellar replacements. Clinical evaluation of these various implants support the conclusions of these analyses. Contact stress analysis should precede any clinical use of patellar implants to avoid predictable failure mechanisms.

Meniscal-bearing unicompartmental knee arthroplasty. An 11-year clinical study.

From 1977 through 1987, 21 meniscal-bearing unicompartmental knee arthroplasties (UKAs) were performed on 20 patients in preference to a distal femoral or proximal tibial osteotomy for unicompartmental knee arthritis. Preoperative diagnoses were osteoarthritis (14 cases), posttraumatic arthritis (5 cases), and rheumatoid arthritis (1 case). Eighteen UKAs (7 lateral, 11 medial) were followed for 24 to 132 months (mean, 34). Using the New Jersey Orthopedic Hospital Knee Scoring Scale, good to excellent clinical results were found in 16 (89%) of the UKAs followed for at least two years. These scores represent significant improvement over preoperative evaluation, (paired t test, P less than or equal to .05). No statistical difference was noted in postoperative results between the lateral or medial arthroplasties (Student's t test, P less than or equal to .05).

Use of survivorship and contact stress analyses to predict the long-term efficacy of new generation joint replacement designs. A model for FDA device evaluation.

Long-term investigational device exemption (IDE) clinical trial evaluation, as currently monitored by the Food and Drug Administration (FDA) regulatory process, is time-consuming, burdensome, and extremely costly to the product developers and ultimately to the consumer. Thus, almost all devices introduced in the past decade have not been clinically tested; they have been introduced under a "510k" grandfather provision that does not address the safety and efficacy of the product. As a result, joint replacement devices have been sold and used with serious failure consequences for the consumer. When 10-year survivorship studies are available for specific joints that demonstrate strong evidence of favorable clinical performance with suitable supporting analysis, they can be used as a standard for comparison with newer, similar designs. Additionally, contact stress analysis of the bearing surfaces of these joint replacements can be used to determine their long-term wear characteristics under normal loading conditions and compared to retrieved devices used for 10 years or more. Devices that demonstrate a 90% survivorship over a 10-year interval and have low enough contact stresses to minimize wear failure during the same period can be used as "standard designs" to which newer designs should be compared. Using this methodology, the developers of any new device should cite the standard design that they have improved on and document an improvement in early (1 to 3 years) survivorship studies with a contact stress analysis demonstrating bearing contact stresses equal to or lower than the standard design. Any device that fails more often or wears out faster than a standard design should not be released until design modifications have proved it superior or equal to the standard designs.

Long-term survivorship analysis of cruciate-sparing versus cruciate-sacrificing knee prostheses using meniscal bearings.

A comprehensive, interchangeable, low-contact-stress, mobile-bearing knee prosthesis system was developed and used over a 12-year period with both cemented and cementless fixation. Individual components of the system included a bicruciate-retaining meniscal bearing, a posterior cruciate-retaining meniscal bearing, and a cruciate-sacrificing, rotating-platform tibial component mated to the same femoral and rotating patellar components. Survivorship analysis of each implant type was performed to identify specific failure modes and trends for long-term survival of the implants in a wide variety of primary knee arthroplasties. Clinically, there were 46 prostheses of the bicruciate type followed for up to 12 years, 57 prostheses of the posterior-cruciate type followed for up to six years, and 108 prostheses of the rotating-platform type followed for up to ten years. All knees in this study had rotating-bearing patellar prostheses. Cumulative survivorship analysis using an end point of implant revision or a poor knee score revealed a small early failure rate of each implant in the first three years, associated with technical positioning or undersizing errors. This study indicates a predictable long-term survival of both cruciate-retaining and cruciate-sacrificing mobile-bearing knee prostheses as well as rotating-bearing patellar prostheses when used in primary knee arthroplasties that minimized technical errors of insertion.

A metal-backed, rotating-bearing patellar prosthesis to lower contact stress. An 11-year clinical study.

A congruent-contact, metal-backed, rotating-bearing patellar prosthesis has been used clinically over an 11-year period. The features of this implant include a congruent-contact, rotating bearing attached to a thin metallic anchoring plate fixed to the bone by cruciate fixturing fins. The device was initially used with methylmethacrylate and later used as a cementless, porous-coated, ingrowth fixation implant. The benefits of congruent contact with mobility to adjust its tracking position during flexion and extension help to eliminate axial shear stresses at the bone-prosthesis interface and lower the contact stresses at the bearing-metal interface to improve wear properties. Prostheses were implanted in 515 knees over a period of six months to 11 years. Of these 515 knees, 331 patellar prostheses have been followed for 24 to 132 months (mean, 73 months). Of that group of 331 implants, 141 were cemented and 190 were cementless. Specific complications involving the use of this implant were as follows. One intraoperative vertical midpatellar fracture in a cemented case went on to uneventful healing with an excellent result. Two displaced postoperative transverse midpatellar fractures (0.39%) occurred in two revision total knee arthroplasties that involved major lateral releases. One of those was a cemented revision and required removal of the implant and a partial patellectomy to gain an excellent result. In the other, a noncemented revision, the patient lacks 45 degrees of quadriceps extension and has a poor result following traumatic fracture at three years postsurgery. One patellar dislocation (0.19%) occurred in a 270-pound, osteoarthritic man in whom undersized components were used. No polyethylene wear-through, separation from the metal anchoring plate, or implant breakage was seen in this series. Overall, the performance of this congruent-contact, metal-backed, rotating-bearing patellar prosthesis indicates the prosthesis can provide long-term function and stability with few short-term or long-term complications.

New Jersey low contact stress knee replacement system. Ten-year evaluation of meniscal bearings.

A metal-backed, interchangeable, meniscal bearing knee replacement system has been designed to combine low constraint forces with low contact stresses (LCS) to allow nearly normal joint articulation and loading as well as long-term wear resistance of the implants. System components allow unicompartmental, bicompartmental, tricompartmental, and revision knee arthroplasties. In this prospective comparison study, the early series of cases used methyl methacrylate for prosthesis-to-bone fixation, whereas the more recent series of knee replacements used sintered-bead porous coating to allow tissue ingrowth stabilization of all implants. Overall results in the first 149 cemented cases with 2- to 10-year follow-up (mean 7.6 years) were good to excellent in 85.2 per cent, fair in 3.4 per cent, and poor in 11.4 per cent using a strict knee scoring scale. Fair and poor results were seen predominantly in multiply operated and implant revision cases. The best cemented results were noted in primary cases, 95.1 per cent of which had good to excellent results. Overall results in the first 208 cementless cases with 2- to 7-year follow-up (mean 4.4 years) were good to excellent in 91.8 per cent, fair in 2.4 per cent, and poor in 5.8 per cent. Fair and poor results were also seen predominantly in multiply operated and implant revision cases. The best cementless results were noted in primary cases, 98.2 per cent of which had good to excellent results. Of 140 meniscal bearing implants in the entire series, one dislocation occurred (0.7 per cent) which required open bearing replacement. Of 217 rotating platform bearing implants in the entire series, 7 dislocations occurred (3.2 per cent), which required open bearing replacement or revision of components for malposition. These dislocations were seen predominantly in revision cases involving insufficient flexion stability; 6 of the 7 cases were revisions. This study demonstrates the efficacy of mobile bearing elements for use in knee replacement arthroplasty. It is essential that flexion and extension gaps be controlled to maintain contact pressure on such bearings to avoid problems of subluxation or dislocation.

New Jersey low contact stress total ankle replacement: biomechanical rationale and review of 23 cementless cases.

A congruent contact, unconstrained, multiaxial ankle replacement has been developed for use without cement. A talar onlay component with a trochlear surface and central fixation fin uses a cylindrical articulating axis that reproduces the lateral talar curvature. A tibial inlay component with a 7 degree anteriorly inclined short fixation stem uses a flat loading plate, recessed anatomically into the distal tibia to distribute tibial loads to the ankle joint. For both components, made of cast cobalt-chromium-molybdenum, a 275-micron pore-size, sintered-bead, porous coating is used to allow tissue ingrowth stabilization. A congruent ultra-high molecular weight polyethylene bearing is inserted between the metallic implants. Its upper surface is flat, whereas its lower surface conforms to the trochlear surface, thereby providing unconstrained, sliding cylindrical motion with low contact stress on the bearing surfaces. Contact pressure and collateral ligaments maintain ankle stability during both static and dynamic loading conditions. Clinically, 23 total ankle arthroplasties were performed in 21 patients. The follow-up period ranged from 24 months to 64 months with a mean of 35.3 months. Diagnoses included rheumatoid arthritis, 6 patients (26.1%); osteoarthritis, 4 patients (17.4%); post-traumatic arthritis, 10 patients (43.5%); avascular necrosis of the talus, 2 patients (8.7%), and painful ankle fusion, 1 patient (4.3%). Pain was the primary reason for surgery in all cases. Postoperatively, 87% of ankles had no pain or, at most, mild pain. Postoperative complications included poor wound healing in four ankles, reflex sympathetic dystrophy in two ankles, deep infection in one ankle, and one bearing subluxation. No ankle replacements were removed and no fusions were performed for failed implants, although one bearing was exchanged without disrupting the metallic elements. In this report, the suggestion is made that total ankle arthroplasty may have an improved application in various arthritis disorders when used with biologic fixation and unconstrained mobile bearings.

The New Jersey Low-Contact-Stress Knee Replacement System: biomechanical rationale and review of the first 123 cemented cases.

A mobile-bearing element, metal-backed, interchangeable knee replacement system has been designed to combine low constraint forces with low contact stresses (LCS), allowing nearly normal joint articulation and loading as well as long-term wear resistance of the implants. The system is versatile, including a large number of component options in variable sizes, and it may be used in both primary and revision arthroplasties. The overall results in the first 123 cemented cases (97 patients) with 2- to 7-year follow-up (average 3.7 years) were good to excellent in 88.6%, fair in 3.3%, and poor in 8.1%. Fair and poor results were seen predominantly in multiply operated and implant revision cases. The best results were noted in primary cases, 97.4% of which had good to excellent results. There have been no mechanical implant failures and no meniscal bearing dislocations in this series. Pain relief and restoration of function have been very gratifying with this system.

"Floating-socket" total shoulder replacement: anatomical, biomechanical, and surgical rationale.

A prosthesis based on a new concept of gleno-humeral motion has been developed and clinically tested for the past 2 years. The "floating-socket" total shoulder replacement contains a nondislocatable, dual spherical bearing system consisting of a small sphere within a larger sphere with their centers offset to provide the physiologic "floating fulcrum" for mechanically advantageous motion. This geometric configuration allows a prosthetic range of motion in excess of anatomical limits to allow soft tissue structures to limit motion rather than mechanical impingement. The device is constructed from Co--Cr--Mo alloy and RCH-1000 polyethylene such that no metal--metal contact can occur. Experimental results in a 112-lb adult male chimpanzee and six clinical cases have revealed superior fixation strength of both glenoid and humeral components, as well as functional adaptation of the prosthesis without fracture of fixturing bone or prosthetic dislocation.