Abstract
History and Background: The HINTEGRA® Total Ankle Prosthesis was designed in 2000 by Dr. B. Hintermann (Basel, Switzerland); Dr. G. Dereymaeker (Pellenberg, Belgium); Dr. R. Viladot (Barcelona/Spain); and Dr. P. Diebold (Maxeville, France), and is manufactured by Newdeal SA in Lyon, France.
Design Features: The HINTEGRA® Total Ankle Prosthesis is a non-constrained, three-component system that provides inversion/eversion stability. Axial rotation and normal flexion/extension mobility are provided by a mobile bearing element. Limits of motion are dependent on natural soft-tissue constraints: no mechanical prosthetic motion constraints are imposed for any ankle movement with this device. The HINTEGRA® ankle uses all available bone surface for support. The anatomically shaped, flat tibial and talar components essentially resurface the tibia and talar dome, respectively, and wings hemiprosthetically replace degenerate medial and lateral facets (a potential source of pain and impingement). No more than 2 to 3 mm of bone removal on each side of the joint is necessary to insert the tibial and talar components. On the tibial side, most importantly, the bony architecture remains intact, and in particular, the anterior cortex is preserved. Perfect apposition with the hard subchondral bone is achieved by the flat resection of the bone and the flat surface of the component. Primary stability for coronal plane motion is provided by two screws inserted into the anterior shield, in the upper part of oval holes so that the settling process of the component is not hindered by axial loading. On the talar side, additional anterior support is provided by a shield, and pressfit is provided by the slightly curved wings. Two pegs facilitate the insertion of the talar component and provide additional stability, particularly against anterior-posterior translation. Another advantage of this concept is the instrumentation that allows reliable implantation of components.
Technique: The prosthesis is implanted through an anterior approach. In the case of malalignment, ligamentous instability, and concomitant osteoarthrosis of the distal joints, additional surgeries are considered before prosthetic implantation.
Complications: In the beginning, a major concern was the positioning of the talar component, which tended to slide too posteriorly while impacting and press fitting. With the addition of two talar pegs, the current design may resist such translational forces during press fitting.
There is evidence that positioning of the talar component too posteriorly may cause pain and limit dorsiflexion of the foot (probably because the posterior aspects of the deltoid ligament are over-tensioned), thereby the intrinsic forces are also increased which may cause unacceptable high shear forces at the bone-implant interface and/or component instability. In all but one of the seven revised talar components (out of the author’s first 400 cases), the component was positioned too posteriorly.
There is a potential risk for dislocation of the meniscal component either laterally or medially as long as no appropriate alignment and/or ligament balancing have been achieved during surgery. The author encountered this problem only in two of the first twenty cases; thereafter, no such complications occurred probably because of better understanding alignment and balancing the ankle.
A potential concern in uncemented resurfacing prostheses is the use of screws that may create stress shielding. The HINTEGRA® ankle, however, uses oval holes on the tibial side so that some settling of the component during osteointegration is possible. As screw fixation is located eccentric to the load transfer area, the potential for stress shielding is in addition minimized.
Salvage of Complications: Special revision implants are available for salvage of failed components. On tibial side, components with a thicker plateau may serve to replace loosed bone stock and to get firm bony support more proximally, thereby preserving the original joint line (that means, the ankle ligaments are supposed to be properly used for stabilizing and guidance of the joint). On talar side, components with a flat undersurface allow flat resection of the talus, thus providing a wide area of bone support to the revision component.
Results: Between 05/2000 and 12/2006, 340 primary TAA were performed in 322 patients (females, 165; males, 157, age 57.3 ± 13.4 years). Underlying diagnosis was posttraumatic osteoarthritis in 272 ankles, primary osteoarthritis in 26 ankles and inflammatory arthritis in 42 ankles. All patients were clinically and radiologically assessed after 6.2 (1.1–7.5) years, and survivorship analysis was calculated. Revision of a metallic implant or conversion into ankle arthrodesis was taken as the endpoint.
The AOFAS Hindfoot Score improved from 42.1 (14–61) points preoperatively to 78.6 (44–100) points at follow-up. 205 ankles (60.5%) were completely pain free. The average range of motion was clinically 32.2° (range, 15° to 55°), and under fluoroscopy (that is, true ankle motion) 30.4° (range, 7° to 62°). Four ankles were revised to TAA (component loosening, 3; pain, 1), and 2 ankles (component loosening and recurrent misalignment, 1; pain, 1) were revised to ankle arthrodesis. Overall survivorship at 6 years was 98.2%, being 97.9% for the talar component and 98.8% for the tibial component.
Four ankles (1.2%) were successfully revised, and the obtained result at latest follow-up did not differ from those ankles without complications. Whereas, 2 ankles (0.6%) were revised to ankle arthrodesis.
In another series of 37 patients (37 ankles: STAR, 26 ankles; HINTEGRA, 3 ankles; AGILITY, 3 ankles, Büchel-Pappas, 2 ankles; MOBILITY, 2 ankles; SALTO, 1 ankle) with failed total ankle arthroplasty, revision arthroplasty was performed with the HINTEGRA® ankle. All but one surgery were successful. At a mean follow-up of 3.6 (1.2–6.4) years, 29 patients (78.4%) were satisfied with the obtained result. The AOFAS Hindfoot Score improved from 39.2 (23–58) points pre-operatively to 72.8 (54–95) points. All but on implants were radiographically stable; in one case, the tibial component showed, at one year, still a radioluscency which may be considered as loosening. As the patient is completely pain free, no revision surgery was done.
In another series of 29 patients (30 ankles), a painful ankle fusion was taken down and ankle arthroplasty was performed with the HINTEGRA® ankle. All surgeries were successful. At a mean follow-up of 3.4 (2–7.6) years, 24 patients (80%) were satisfied with the obtained result. The AOFAS Hindfoot Score improved from 34.1 (18–47) points preoperatively to 69.4 (48–90) points. The obtained motion for dorsi-/plantar flexion was clinically 23.5° (10°–40°) [52.6% of contra lateral ankle), and radiographically (“true ankle motion”) 24.5°(8°–24°) [54.4% of contra lateral ankle].
The author’s overall experience: more than 750 replacements with the HINTEGRA® ankle in the last 8 years. The learning curve was rather long as some adjustments had to be performed, and there was need of some time to understand “ligament balancing” in ankle replacement in more detail. However, since then, an extremely high satisfaction rate was obtained, and most patients are doing very well. The revision rate has also turned down to < 2% despite, with increased experience, more complex cases may have been considered for ankle replacement.
Conclusion: Obviously, TAA using a current anatomic design of 3-component prosthesis (HINTEGRA) have evolved to a safe procedure with reliable results at mid- to long-term. These encouraging results support our belief that TAA has become a viable alternative to ankle arthrodesis even for younger patients and more difficult conditions, as often the case in posttraumatic osteoarthritis.
Correspondence should be addressed to ISTA Secretariat, PO Box 6564, Auburn, CA 95604, USA. Tel: 1-916-454-9884, Fax: 1-916-454-9882, Email: ista@pacbell.net
