3D, Weightbearing Topographical Study of Periprosthetic Cysts and Alignment in Total Ankle Replacement

Abstract

Background: We investigated the association between hindfoot residual malalignment assessed on weightbearing computed tomography (WBCT) images and the development of periprosthetic cysts (PPCs) after total ankle replacement (TAR). We hypothesized that PPCs would be found predominantly medially in the varus configuration and laterally in the valgus configuration. Methods: Cases of primary TAR with available WBCT imaging of the ankle were included in this retrospective study. The location of the PPC was marked and the following volumes were calculated: total (TCV), medial (MCV), central (CCV), and lateral (LCV) cyst volumes. Hindfoot alignment was measured as Foot and Ankle Offset (FAO), with 95% confidence intervals (95% CIs) calculated to define varus (<95% CI) and valgus (>95% CI) groups. Cyst volumes were compared between these 2 groups. The American Orthopaedic Foot & Ankle Society (AOFAS) score at the time of the WBCT was also retrieved. Receiver operating characteristic (ROC) curves were used to determine FAO thresholds for predicting an increased risk of PPC. Results: Forty-eight TARs (mean follow-up, 44.6 months) were included, 81% of which had at least 1 PPC. The mean FAO was 0.12% (95% CI, –1.12 to 1.36). Patients with greater residual malalignment ( P < .001) and those with longer follow-up ( P < .001) presented with increased TCV. In varus cases, the MCV was greater than the LCV ( P = .042), with a threshold FAO value of −2.75% or less predicting an increased MCV. In valgus cases, the LCV was greater than the MCV ( P = .049), with a FAO threshold value of 4.5% or more predicting an increased LCV. Conclusion: In this series, the PPC volume after primary TAR significantly correlated with postoperative hindfoot malalignment and longer follow-up. Level of Evidence: Level III, retrospective comparative series.

Three-Dimensional Biometrics to Correlate Hindfoot and Knee Coronal Alignments Using Modern Weightbearing Imaging

“…Three-dimensional biometrics will bring us more insights about the effect of corrective foot and ankle surgeries (calcaneus and supramalleolar osteotomies, triple arthrodesis) on the lower limb or for patients who experienced complications (pain, accelerated degenerative process) that are not explained solely by the condition of the ankle joint (periprosthetic cysts in ankle replacement). 10 Beyond a better understanding of alignment (including rotation) in basic science, the ultimate goal remains to detect and/or to monitor patients who are at risk to decompensate after additional elective surgeries of the lower limb.…”

Intermediate-term Patient-Reported Outcomes and Radiographic Evaluation Following Intramedullary- vs Extramedullary-Referenced Total Ankle Replacement

“…Previous studies have shown that progressive periprosthetic cysts lead to implant instability and poor implant survivorship. 20,26,27,30 One potential cause for the increased incidence of progressive cyst formation for the STAR TAR is that it uses a mobile-bearing polyethylene liner that is susceptible to medial edge-loading and polyethylene wear if alignment and tracking are not optimal. 45 We chose to elucidate the incidence of progressive cyst as an important complication because these are the ones that should be closely monitored with serial radiographs and potentially bone grafted to prevent implant compromise.…”

Weight-Bearing Cone Beam Ct Scans and Its Uses in Ankle, Foot, and Knee: An Update Article

“…The total cystic volume was positively correlated with residual malalignment, measured by the absolute FAO values, with the varus alignment presenting a more medially positioned cyst and the valgus alignment a laterally positioned cyst. 48…”