B. Hintermann, A. Barg, M. Knupp, and V. Valderrabano reply:
We thank Dr. Kini for his interest and comments on our study, and we are grateful for the opportunity to make the following comments.
At the time of the latest follow-up, any persisting pain laterally was localized to periarticular soft tissues. This finding can be best explained by the fact that most of the patients included in this study had had an average of 3.3 previous operations (range, zero to nine previous procedures). To exclude the possibility of subtalar arthritis or arthritis in other adjacent joints as the cause of pain, we recommend performing single photon emission computed tomography (SPECT-CT)1. In seven patients, pain was mainly localized in the medial aspect of the ankle at the time of the latest follow-up. The origin of this pain was irritation of periarticular soft tissues and not osseous impingement at the medial side of the ankle in patients in whom the mechanical axis had been restored. It is imperative that the tibial component and the heel are properly aligned with the mechanical axis of the leg. If the tibial component is implanted in a varus position, and/or the heel is in valgus, osseous impingement in the medial gutter was seen to occur.
In this group, all patients were allowed full weight-bearing in the cast. However, for some patients, we recommend non-weight-bearing for eight weeks postoperatively. During the first clinical and radiographic follow-up at six weeks postoperatively, we found the range of motion to be slightly less in patients who were non-weight-bearing as compared with those who were fully weight-bearing; however, the difference was not significant. At the next follow-up (four months postoperatively), we did not detect any difference in range of motion between these patient groups.
Newer gait-analysis studies have shown that a nearly normal gait pattern is present in terms of joint kinematics of the knee, ankle, and foot after uneventful mobile-bearing total ankle replacement2. Dr. Kini stated in his letter that if 10° of dorsiflexion is not obtained during the middle portion of the stance phase, the gait will be similar to what is observed following ankle arthrodesis3. However, we believe that the ankle mobility gained after this arthroplasty, even in patients with <10° of dorsiflexion, can decrease the stress forces in the adjacent joint, which may slow down the development of osteoarthritis as reported in patients managed with ankle fusion4,5.
Indeed, malleolar fracture has been reported as a common intraoperative complication, with a prevalence of as high as 10%6,7. In this study, we observed five fractures of the malleoli (including a medial malleolar fracture in three ankles, a lateral malleolar fracture in one ankle, and a bimalleolar fracture in one ankle). Therefore, we now use prophylactic pinning in cases in which the malleoli seem to be at risk of fracture.
These letters originally appeared, in slightly different form, on . They are still available on the web site in conjunction with the article to which they refer.