Sahar Shiraj MD, Presenter: Nothing to Disclose

Carl Scherman Winalski MD, Abstract Co-Author: Institutional research contract, Smith & Nephew plc Contract, Smith & Nephew plc Contract, Johnson & Johnson Contract, sanofi-aventis Group Contract, Bioclinica, Inc Contrast, Axio Research Research Grant, The Procter & Gamble Company Shareholder, NitroSci Pharmaceuticals, LLC Shareholder, Pfizer Inc Shareholder, General Electric Company

Erika Schneider PhD, Abstract Co-Author: Stockholder, General Electric Company Stockholder, Pfizer Inc Stockholder, NitroSci Pharmaceuticals, LLC Research Consultant, Johnson & Johnson

Flavia Aiko Sakamoto MD, Abstract Co-Author: Nothing to Disclose

Jonathan L. Schaffer MD, Abstract Co-Author: Consultant, AcelRx Pharmaceuticals, Inc

Hakan Ilaslan MD, Abstract Co-Author: Nothing to Disclose

Radiographic change in cartilage tumor calcifications is considered a sign of chondrosarcoma. During total knee arthroplasty (TKA) enchondromas may be disrupted by an intramedullary (IM) guide rod. Our purpose was to describe the expected radiographic changes in enchondromas after TKA.

Medical records search between 2000-2013 identified 214 of 9,167 TKA patients seen at our institution with radiographic reports mentioning enchondroma. Study group had enchondromas in the operated knee while the controls had enchondromas in the non-operated knee. Both groups had pre- and postop radiographs. Tumor size, location (eccentric/central), calcification pattern and changes were judged in consensus by 2 MSK radiologists for preop, early postop and longest followup postop radiographs.

Study group was 36 patients (16 men, mean age 72) with 39 enchondromas (31 femur, 8 tibia). 15 controls (6 male, mean age 71) with 15 enchondromas (13 femur, 2 tibia). Mean time (months) between imaging and surgery was: pre-op 3.6; early post-op 1.3; longest followup 28.4. In the study group, 32/39 enchondromas appeared disrupted on early postop images with calcifications appearing more spread out in 18 of 32. Subtle central clearing (5) and partial loss of the calcifications (2) were also seen. Tibial lesions were more often replaced (3) or pushed inferiorly (2) by the component. Median change in calcification length was 0.9cm (max 6.9cm). Of 7 unchanged enchondromas, 3 were eccentric and 3 were so thin that the IM rod likely missed the lesion; in 1 no rod was used. At longer followup, 12/20 showed partial (11) or complete (1) disappearance of calcifications with no change in 8. Control group showed no change in lesion appearance or size.

Changes in radiographic appearance of enchondroma calcifications commonly occur following TKA surgery when an IM guide rod is used. Longitudinal spreading, subtle central clearing or partial loss of the calcifications are most common. When the changes occur at the time of surgery, they should not be misinterpreted as signs of chondrosarcoma. No long term consequence of surgical disruption of enchondromas was identified.

Radiographic changes in femoral and tibial enchondromas after total knee arthroplasty may result from surgical technique. Awareness of this phenomenon may help avoid confusion with malignancy.

Shiraj, S, Winalski, C, Schneider, E, Sakamoto, F, Schaffer, J, Ilaslan, H, Pseudo-chondrosarcomas Following Total Knee Arthroplasty.  Radiological Society of North America 2013 Scientific Assembly and Annual Meeting, December 1 - December 6, 2013 ,Chicago IL. http://archive.rsna.org/2013/13044394.html