Bone Cysts and Osteolysis in Ankle Replacement

Abstract

Background: Total ankle replacements (TARs) have higher rates of osteolysis than hip or knee replacements. It is unclear whether this is a pathologic immunologic process in response to wear debris, or expansion of pre-existing osteoarthritic bone cysts. We aimed to determine the incidence of bone cysts in patients with end-stage ankle arthritis prior to surgery and review the literature on bone cysts and osteolysis in relation to TAR. Methods: This is a descriptive/prevalence study in which all patients with end-stage ankle arthritis underwent plain radiographic imaging and computed tomographic (CT) scans prior to TAR surgery. Their imaging was assessed for the presence of cysts, measured on sagittal, axial, and coronal slices of the CT scan at the widest diameter. All cysts that would be removed as a result of the bone resection for the implant were excluded using digital analysis software. We assessed 120 consecutive patients with mean age of 63.4 years. Results: Seventeen patients (14%) did not have any bone cysts based on CT images. Ten patients (8%) had cysts that would have been completely removed by surgery, leaving 93 patients for analysis (78%). In 60% of these cases, the cysts were not seen on the plain radiographs. In 39 patients (33%), the cysts were greater than 5 mm in size. The medial (36%) and lateral malleoli (33%) were the most common location for the cysts (mean diameter 4.6±2.0 and 4.2±2.3 mm, respectively). Conclusion: Bone cysts outside of the resection margins for a TAR were present in 78% of patients with ankle arthritis prior to undergoing surgery. In 30% of cases, cysts were greater than 5 mm in size. In 60% of cases, the cysts were not seen on plain radiographs. Preoperative 3-dimensional imaging can provide a foundation to observe and quantify cyst presence, expansion, and time of onset in the postoperative setting. Level of Evidence: Level IIc, diagnostic/prevalence study.

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

“…These early cysts may be preoperative bone cysts rather than procedure-related osteolytic cysts. 47 In our study, the average time of diagnosis was 7.1 years after the TAA procedure, ranging from 3.7 to 9.7 years. These were thus late-onset cysts, which lead us to believe that these cysts would have progressed in size, ultimately leading to mechanical failure.…”

Low Rate of Peri-implant Osteolysis in Trabecular Metal Total Ankle Replacement on Short- to Midterm Follow-up

“…4,8,15,18,38 With progressive cysts, the risk for component revision or conversion to arthrodesis is substantial, and it is generally recommended to closely follow TAR patients with sufficient imaging modality. It has been shown that CT shows osteolytic lesions around TAR significantly better than radiographs, 16,17,30,36 especially on the talar side, 17 and also in the previously mentioned study by Najefi et al, 29 the preoperative cysts were not detected on plain radiographs in 60% of the cases. The radiation dose not cause a major problem as the ankle is located peripherally and the mean effective dose for CT of the ankle is only 0.07 mSv.…”

“…In a series of 120 consecutive patients with end-stage ankle osteoarthritis analyzed with CT prior to TAR, 78% of patients had bone cysts present in the area where they would not have been removed by bone resection at surgery, located mainly in medial and lateral malleoli. 29 The authors concluded that a preoperative 3-dimensional imaging to detect the existence of preoperative cysts in TAR patients would be useful when assessing the cysts postoperatively. 29 In the current study, all the osteolytic lesions detected on CT images developed postoperatively, and none of them were seen on preoperative CT or MRI images.…”

“…29 The authors concluded that a preoperative 3-dimensional imaging to detect the existence of preoperative cysts in TAR patients would be useful when assessing the cysts postoperatively. 29 In the current study, all the osteolytic lesions detected on CT images developed postoperatively, and none of them were seen on preoperative CT or MRI images. Four of the 11 osteolytic lesions were situated in the medial malleolus and 1 in the lateral malleolus, with no direct contact to implant components.…”

“…The radiation dose not cause a major problem as the ankle is located peripherally and the mean effective dose for CT of the ankle is only 0.07 mSv. 6 Therefore, a pre- and postoperative CT scanning has been recommended for TAR patients 16,17,29,30,36 and is adopted as routine in our institute. Although the clinical relevance of the peri-implant osteolytic changes is not clear, the use of CT in the follow-up makes the decision making easier in the cases of such findings.…”