Abstract
Introduction
Ankle arthrodesis is a common treatment for destroyed ankle arthrosis with sacrificing the range of motion. On the other hand, total ankle arthroplasty (TAA) is an operation that should develop as a method keeping or improving range of motion (ROM); however, loosening and sinking of the implant have been reported in especially constrained designs of the implant. The concept of FINE TAA is the mobile bearing system (Nakashima Medical Co., Ltd, Okayama Japan) that can reduce stress concentration to implants. The purpose of this study is to evaluate the short-term results of FINE TAA.
Objectives and Methods
We performed FINE TAA for osteoarthritis (OA) (2 ankles of 2 patients) and rheumatoid arthritis (RA) (4 ankles of 3 patients). All patients were female. The mean age of the patients was 71.4 years old at the operation. The mean follow-up period was 32.6 (range, 18–55) months. All patients were assessed for Japan Orthopedic Association (JOA) score and ROM in plantar flexion and dorsiflexion at the point of pre-operation and final follow-up. We evaluated radiolucent line, subsidence, and alignment of implants at the latest follow-up.
Results
JOA score improved from 34.8 to 72.2 on average. ROM improved from 4.0 ± 5.5 º to 7.0 ± 4.5 º on average in plantar flexion and from 21.0 ± 17.0 º to 31.0 ± 16.0 º in dorsiflexion. One case underwent an ankle arthrodesis because of the implant loosening. This failed case was very obese (70 kg of body weight, 31.0 of Body Mass Index) and her activity was relatively high. One ankle showed radiolucent line around the components with no symptoms. The alignment of implants was slightly varus and anteversion (the mean values of alpha angle was 88.0 ± 1.2º, beta angle was 84.0 ± 9.2º, and gamma angle was 2.1 ± 0.2º).
Discussion
The ankle joint is highly loaded up to five times body weight on small surface of contact area during walking. Therefore, the poor results have been published after TAA with using fixed-bearing 2-component prostheses compared to ankle arthrodesis. On the other hand, FINE TAA was designed as 3-component mobile bearing system that can reduce stress concentration compared to conventional TAA. We experienced implant failure in one obese case but short-term results of other cases were acceptable. Good clinical results can be expected with FINE TAA except for the obese case. We should pay careful attention to the surgical indication.
Conclusion
Our short term results of FINE TAA were acceptable except for one obese case. We should evaluate further mid- and long- clinical results.
