Intermediate to Long Term Follow Up of Hintegra Total Ankle Replacements

Abstract

Category: Ankle, Ankle Arthritis Introduction/Purpose: The optimal management of severe ankle arthritis is still debated. Some maintain that arthrodesis is the reference standard. However, with appropriately selected patients modern Total Ankle Replacements (TAR) can offer good to excellent patient reported outcomes. First generation TARs were highly constrained and prone to accelerated wear, loosening and subsidence and failure. Subsequent reincarnations have led to the development of reduced constraint, mobile bearing prostheses with reliance on ligamentous balancing. New generation TARs report 10-year survival of up to 89%, however many studies are from design centres and not uniformly replicated elsewhere. The largest long-term Hintegra TAR study is from a designer’s centre, reporting 84% survival at 10 years. This paper reports multicentre results on the intermediate (6 years +) outcomes of the Hintegra TAR. Methods: TARs performed by two senior consultant surgeons from 30/03/2004-18/01/2013 were reviewed. Prospective review of patients included; review of current and or new symptoms, an updated past medical history, AOFAS Hindfoot scores and radiological imaging. We used the AOFAS hindfoot score for our functional assessment as it validated and also the most frequently cited scoring system in the literature. Radiographs were reviewed for loosening and this was defined by a validated assessment method with a suitably low inter-observer variability. In our study all images were reviewed by at least two authors for a consensus opinion. The Charlson Comorbidity Index (CCI) was utilised to evaluate and risk stratify co-morbidities and their influence on other illnesses and surgical outcomes. This study was considered to be service evaluation by our local research and ethics department and approved in accordance with General Data Protection Regulation guidelines. Statistical analysis was performed using SPSS software. Results: 62 TARs were performed on 58 patients. Excluding the deceased (n=9) and patients lost to follow up (n=1), mean follow up was 12years 3months. AOFAS score did not decline with age of TAR (Spearman Rho co-efficient 0.339). During the first 4 years Hintegra TARs were performed 11/23 (48%) patients underwent additional surgery highlighting the already published learning curve with TAR. 5-year and 10-year survival was 84% (52/62) and 71% respectively (27/38). Predictors for revision included obesity with a BMI>30 versus those with a BMI of 18.5-25 (Chi-Sq P-value 0.006) and previous smoking history (Chi-Sq P-value 0.027). No association was found between CCI scores and revision (One-way ANOVA P-value 0.4). Interestingly lower ASA scores were significantly more likely to require revision (One-way ANOVA P-value 0.034). Conclusion: The Hintegra Total Ankle Replacement offers good sustained pain relief and function. 71% of implants were retained with an average AOFAS score of 78 (36-100 range) after 10 years. We do recommend caution in patients who are obese, smokers, ex-smokers and those with a high functional demand. We stress the importance of achieving correct alignment of the TAR to maximise longevity. There is a steep learning curve when performing a TAR and we would suggest operating with another experienced surgeon for at least the first 20 cases.