Two consecutive series of patients who had cementless, porous-coated, congruent-contact, mobile-bearing total ankle replacements were evaluated during a 20-year interval using the New Jersey Orthopaedic Hospital ankle scoring scale to determine clinical outcome and overall implant survivorship with revision as an end point. The initial series of 38 patients (40 ankle replacements) using a shallow-sulcus design had diagnoses of: osteoarthritis, seven (17.5%); rheumatoid arthritis, nine (22.5%); posttraumatic arthritis, 21 (52.5%); and failed fusion, three (7.5%). Clinical results after 2-20 years, (mean, 12 years) were 28 (70%) good to excellent, two (5%) fair, and 10 (25%) poor. Postoperative ankle motion ranged from 10°-47°total arc (mean, 25°total arc). The 20-year overall survivorship for the shallow-sulcus design was 74.2%. A second series of 74 patients (75 ankle replacements) using a deep-sulcus design had diagnoses of: osteoarthritis, eight (11%); rheumatoid arthritis, nine (12%); osteonecrosis, three (4%); and posttraumatic arthritis, 55 (73%). Clinical results after 2-12 years, (mean 5 years) were 66 (88%) good to excellent, four (5%) fair, and five (7%) poor. Postoperative ankle motion ranged from 10°-50°t otal arc (mean, 29°total arc). The 12-year overall survivorship for the deep-sulcus design was 92%.Improved total ankle replacement results using mobile bearings have been reported. 3,4,7,16,24 It is postulated that these results have been produced by allowing normal kinematic function of the bones and ligaments as seen in gait analysis 20 and load-bearing cineradiographic studies. 17 Allowing distal fibular rotation to optimize lateral ligamentous function during dorsiflexion and planter flexion motion is an ideal goal. Such rotation can average 2.2°(range, 1.4°-4.8°). 13 Fixed-bearing devices that attempt to eliminate or minimize this fibular motion or restrict axial rotation can be subjected to torsional loads that can loosen tibial component fixation 1,10,11,15,21,25,26 or result in nonunion of the syndesmosis. 12,23 The current study involves the use of rotationally unconstrained mobile bearings that articulate with a flat tibial plate superiorly and a biconcave trochlear talar component surface inferiorly (Fig 1). The surface geometry remains fully congruent, even during inversion and eversion motions to reduce contact stresses below the medical load limit for UHMWPE of 5 MPa. 8 Inversion and eversion congruity is essential to prevent edge-loading wear and deformation, which has been reported with flat-on-flat knee replacement designs. 19 Deepening the trochlear sulcus angle tends to center the meniscal bearing and prevent bearing subluxation under normal load-bearing conditions. 7 The improved stability of the deep-sulcus geometry over the shallow-sulcus geometry has been reported in the short term. 7 Our study reflects longer-term use of both designs with more detailed analysis. MATERIALS AND METHODSTwo consecutive series of patients with cementless, porouscoated, congruent-contact, mobile-bea...

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A porous-coated, cementless, congruent-contact, three-piece, meniscal-bearing total ankle replacement was developed and used clinically over a 2- to 10-year period for patients with disabling ankle arthritis. Polished titanium-nitride ceramic-coated Ti6Al4V tibial and talar components with a deep-sulcus trochlear groove and two lateral fixation fins for the talar onlay component were used. The ultra-high-molecular-weight polyethylene (UHMWPe) meniscal bearing congruently conformed to the flat upper tibial component surface and the deep sulcus and cylindrical geometry of the lower talar component surface. Fifty deep-sulcus (Buechel-Pappas) total ankle replacements were implanted in 49 patients. Diagnoses were 8 osteoarthritis (16%), 7 rheumatoid arthritis (14%), 2 avascular necrosis (4%), and 33 post-traumatic arthritis (66%). Ages ranged from 26 to 71 years (mean 49 years). Clinical results using a strict ankle scoring system demonstrated good/excellent results in 88% of cases. Postoperative ankle motion ranged from 12 degrees to 46 degrees total arc (mean 28 degrees), which was similar to the preoperative motion. Revision for malalignment was necessary in two cases (4%). Mechanical complications included one case of meniscal bearing wear (2%) in a patient with post-traumatic arthritis with component malalignment and one case of talar component subsidence (2%) in a patient with avascular necrosis of the talus. No tibial component loosening was seen. Cumulative survivorship using an end point of revision of any component for any reason was 93.5% at 10 years (confidence interval 61-100%).

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.

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.

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