German Total Ankle Replacement Register of the German Foot and Ankle Society (D. A. F.) - presentation of design and reliability of the data as well as first results

INTRODUCTION Even though arthroplasty of the ankle joint is considered to be an established procedure, only about 1,300 endoprostheses are implanted in Germany annually. Arthrodeses of the ankle joint are performed almost three times more often. This may be due to the availability of the procedure - more than twice as many providers perform arthrodesis - as well as the postulated high frequency of revision procedures of arthroplasties in the literature. In those publications, however, there is often no clear differentiation between revision surgery with exchange of components, subsequent interventions due to complications and subsequent surgery not associated with complications. The German Orthopaedic Foot and Ankle Association's (D. A. F.) registry for total ankle replacement collects data pertaining to perioperative complications as well as cause, nature and extent of the subsequent interventions, and postoperative patient satisfaction. MATERIAL AND METHODS The D. A. F.'s total ankle replacement register is a nation-wide, voluntary registry. After giving written informed consent, the patients can be added to the database by participating providers. Data are collected during hospital stay for surgical treatment, during routine follow-up inspections and in the context of revision surgery. The information can be submitted in paper-based or online formats. The survey instruments are available as minimum data sets or scientific questionnaires which include patient-reported outcome measures (PROMs). The pseudonymous clinical data are collected and evaluated at the Institute for Evaluative Research in Medicine, University of Bern/Switzerland (IEFM). The patient-related data remain on the register's module server in North Rhine-Westphalia, Germany. The registry's methodology as well as the results of the revisions and patient satisfaction for 115 patients with a two year follow-up period are presented. Statistical analyses are performed with SAS™ (Version 9.4, SAS Institute, Inc., Cary, NC, USA). RESULTS About 2½ years after the register was launched there are 621 datasets on primary implantations, 1,427 on follow-ups and 121 records on re-operation available. 49 % of the patients received their implants due to post-traumatic osteoarthritis, 27 % because of a primary osteoarthritis and 15 % of patients suffered from a rheumatic disease. More than 90 % of the primary interventions proceeded without complications. Subsequent interventions were recorded for 84 patients, which corresponds to a rate of 13.5 % with respect to the primary implantations. It should be noted that these secondary procedures also include two-stage procedures not due to a complication. "True revisions" are interventions with exchange of components due to mechanical complications and/or infection and were present in 7.6 % of patients. 415 of the patients commented on their satisfaction with the operative result during the last follow-up: 89.9 % of patients evaluate their outcome as excellent or good, 9.4 % as moderate and only 0.7 % (3 patients) as poor. In these three cases a component loosening or symptomatic USG osteoarthritis was present. Two-year follow-up data using the American Orthopedic Foot and Ankle Society Ankle and Hindfoot Scale (AOFAS-AHS) are already available for 115 patients. The median AOFAS-AHS score increased from 33 points preoperatively to more than 80 points three to six months postoperatively. This increase remained nearly constant over the entire two-year follow-up period. CONCLUSION Covering less than 10 % of the approximately 240 providers in Germany and approximately 12 % of the annually implanted total ankle-replacements, the D. A. F.-register is still far from being seen as a national registry. Nevertheless, geographical coverage and inclusion of "high-" (more than 100 total ankle replacements a year) and "low-volume surgeons" (less than 5 total ankle replacements a year) make the register representative for Germany. The registry data show that the number of subsequent interventions and in particular the "true revision" procedures are markedly lower than the 20 % often postulated in the literature. In addition, a high level of patient satisfaction over the short and medium term is recorded. From the perspective of the authors, these results indicate that total ankle arthroplasty - given a correct indication and appropriate selection of patients - is not inferior to an ankle arthrodesis concerning patients' satisfaction and function. First valid survival rates can be expected about 10 years after the register's start.

Einleitung: Jährlich werden in Deutschland nur rund 1300 Sprunggelenkendoprothesen implantiert, aber rund 3600 Arthrodesen durchgeführt. Dies beruht u. a. auf der besseren Verfügbarkeit der Arthrodese sowie den publizierten Häufigkeiten der Revisionseingriffe, oftmals nicht differenziert zwischen Wechseleingriffen, komplikationsabhängigen und komplikationsunabhängigen Folgeeingriffen. Auswertungen des Sprunggelenkendoprothesenregisters der Deutschen Assoziation für Fuß und Sprunggelenk e. V. ermöglichen neben dieser Differenzierung auch Aussagen über die Patientenzufriedenheit. Material und Methode: Erhebungsinstrumente liegen als Minimaldatensatz oder wissenschaftliche Fragebögen vor. Speicherung und Auswertung der pseudonymisierten klinischen Daten erfolgt am Institut für Evaluative Forschung in der Medizin der Universität Bern/Schweiz, die patientenbezogenen Daten verbleiben auf dem Modulserver der D. A. F. in Nordrhein-Westfalen. Dargestellt wird die Methodik des Registers und die Ergebnisse zu Revisionen sowie zur Patientenzufriedenheit für die 115 Patienten mit einem Follow-up von 2 Jahren. Ergebnisse: 621 Datensätze zu Primärimplantationen, 1427 zu Nachuntersuchungen und 121 zu Reoperation liegen vor. Über 90 % der Primäreingriffe verliefen komplikationslos, Folgeeingriffe wurden insgesamt für 13,5 % (84), Wechseleingriffe für 7,6 % der Patienten erfasst. 89,9 % der Patienten bewerten das Ergebnis als exzellent oder gut, 9,4 % als mäßig und nur 0,7 % als schlecht. Die medianen AOFAS-AHS-Score-Werte stiegen von 33 Punkten präoperativ auf konstant über 80 Punkte an 3 Monate bis 2 Jahre postoperativ. Schlussfolgerung: Geografische Abdeckung sowie die Erfassung von „High-“ und „Low-Volume-Operateuren“ machen das Register trotz seiner der geringen Abdeckung repräsentativ. Die akzeptable Revisionsrate und hohe Patientenzufriedenheit machen die OSG-Endoprothetik im Hinblick auf die ersten funktionellen Ergebnisse der Arthrodese nicht unterlegen. Erste belastbare Ergebnisse zu Standzeiten können erst nach einem 10-Jahres-Follow-up erwartet werden.