Letter Regarding: CT Scan Assessment and Functional Outcome of Periprosthetic Bone Grafting After Total Ankle Arthroplasty at Medium-term Follow-up

Dear Editor:

We read with great interest the article by Naude et al ¹ on the management of periprosthetic cysts after total ankle arthroplasty. The optimal treatment of large cysts, especially when asymptomatic, is still up for debate, with little in the literature to guide decision making. We commend the authors for describing their valuable experience in this area, as well as FAI for recognizing the importance of this topic.

However, we would like to express our reservations on one of the key conclusions made in the article. The authors write, “We recommend that periprosthetic cysts greater than 1.75 cm³ be prophylactically grafted.” The authors are basing this recommendation on their experience treating 93 patients, only 8 of whom were treated surgically for periprosthetic cysts. There is no scientific basis provided for this recommendation, with the critical number of 1.75 cm³ seemingly decided upon arbitrarily by the authors. Interestingly, they make this recommendation in spite of the fact that almost all of the surgically treated patients in their series had cysts much larger than 1.75 cm³, with a mean volume of 8.16 cm³.

Orthopaedics has long been plagued by arbitrary guidelines, based on weak or no evidence, that persist for decades. We are all aware of the consequences of numeric thresholds and pronouncements made in the literature and how they can be propagated and misused by surgeons, researchers, patients, and insurance payors. Although we think that the authors’ case series provides useful information on their experience treating periprosthetic cysts, we do not believe that their concluding treatment recommendations are warranted.

Defining a threshold for grafting asymptomatic cysts in total ankle arthroplasty has been challenging. In some cases, smaller cysts may threaten fixation and stability of lower-profile implants, whereas in other cases, larger cysts may be better tolerated based on location and fixation features of the implants. The establishment of rigorous criteria for the operative treatment of periprosthetic cysts will require further investigation using hypothesis-driven methods and greater numbers of patients, with the outcomes of both nonoperative and operative treatment reported. Given the small number of patients treated in this (and most) series, this is an area ripe for multi-institution collaboration. We look forward to future publications in FAI on this topic in the years to come.

Sincerely,

Elizabeth A. Cody, MD

Jensen K. Henry, MD

Scott J. Ellis, MD

Constantine A. Demetracopoulos, MD

Hospital for Special Surgery

New York, NY, USA

codye@hss.edu

Supplemental Material

sj-pdf-1-fai-10.1177_10711007221118566 – Supplemental material for Letter Regarding: CT Scan Assessment and Functional Outcome of Periprosthetic Bone Grafting After Total Ankle Arthroplasty at Medium-term Follow-up

Supplemental material, sj-pdf-1-fai-10.1177_10711007221118566 for Letter Regarding: CT Scan Assessment and Functional Outcome of Periprosthetic Bone Grafting After Total Ankle Arthroplasty at Medium-term Follow-up by Elizabeth A. Cody, Jensen K. Henry, Scott J. Ellis and Constantine A. Demetracopoulos in Foot & Ankle International