E1663. CT Appearance of Trunnionosis
  1. Faiza Boukerche; Penn State Hershey Medical Center
  2. Cristy French; Penn State Hershey Medical Center
  3. Jonelle Thomas; Penn State Hershey Medical Center
Trunnionosis is a complication of total hip arthroplasty resulting from wear/corrosion of the taper at the femoral head-neck interface. It may result in adverse local tissue reaction (ALTR) and frank hardware failure requiring surgical revision. The majority of studies have described the magnetic resonance imaging and ultrasound characteristics of ALTR. To our knowledge, the computed tomography (CT) appearance of ALTR from trunnionosis has not been described. The purpose of our study was to describe the CT findings of trunnionosis.

Materials and Methods:
A retrospective review of the Picture Archive and Communications System (PACS) was performed to identify patients with total hip arthroplasty and CT examinations of the hip or pelvis. This was cross-referenced with use of the word trunnionosis, trunnion wear, or trunnion in the final radiology report. A fellowship trained musculoskeletal radiologist and medical student reviewed all cases in the PACS to identify presence of ALTR and collection location, size, region of interest Hounsfield units (HU), capsule attenuation, presence of communication with the joint, and any osteolysis or other complications. The medical record was reviewed to obtain gold standard of surgical notes and pathology results describing trunnionosis. Exclusion criteria were patients with prosthetic infection or no surgical follow-up.

14 patients with trunnionosis had CT scans. 8 right THA and 6 left THA were found in 9 women and 5 men. 13 of 14 patients had a periprosthetic soft tissue collection. 1 patient without a collection had osteolysis. 5 collections were located anteromedial, 5 posterolateral, 2 joint centered, and 1 surrounded the entire THA. All collections communicated with the hip joint and had a metal attenuation rim. Mean ROI HUs of the collections was 79.5 HU (range 22-160). Mean size of the collections was 4.11 cm AP x 3.99 cm transverse x 7.2 cm CC diameter. 5 of 13 patients with collections also had either femoral or acetabular osteolysis.

This is the first large series to describe CT findings of surgically proven patients with trunnionosis. As some of these cases may be incidentally found on a routine CT of the abdomen and pelvis prior to development of symptoms, it is important that both musculoskeletal and body imaging radiologists be aware of the typical CT features of trunnionosis.