Does CT improve the accuracy of predicting implant fixation status for periprosthetic fractures around uncemented femoral components?

Abstract

Aims: Periprosthetic femoral fractures (PPFFs) around total hip arthroplasty (THA) stems are challenging. Typically, loose stems are revised, while well-fixed implants undergo fracture open reduction and internal fixation. Determining implant fixation status preoperatively is important. The purpose of this study was to define the accuracy of predicting the status of preoperative stem fixation using radiography and CT.

Methods: A total of 24 patients with Vancouver B-type PPFF with preoperative radiography and CT scans were included. Patients with obviously loose implants (detached or subsided stem), fractures that occurred within 90 days of index THA, and cemented femoral components were excluded. Two fellowship-trained adult reconstruction surgeons and two traumatologists reviewed radiographs and predicted stem fixation status. They then evaluated CT scans, and fixation status was reassessed. Each surgeon undertook two evaluations one month apart. The correct response was determined by intraoperative findings. Interobserver and intraobserver reliability values were calculated, as well as validity.

Results: Overall, 15 implants (62.5%) were well-fixed and nine (37.5%) were loose. Radiography alone predicted correct fixation status in 53.1% of cases (102/192). When adding CT, correct predictions improved to 54.7% (105/192). Fixation status predictions were changed in 18.2% of cases (35/192) after reviewing CT scans: 8.3% (16/192) from correct to incorrect, and 9.9% (19/192) from incorrect to correct. Interobserver reliability ranged from poor to moderate agreement, and intraobserver reliability demonstrated moderate agreement for all raters. No difference in accuracy was noted between adult reconstruction or trauma surgeons.

Conclusion: The ability to predict fixation status for PPFFs around uncemented femoral components remains challenging. The addition of preoperative CT did not significantly improve accuracy. Intraoperative testing of femoral component fixation status is essential to determine if revision or fixation is appropriate. Preoperative CT for Vancouver B PPFF does not significantly improve accuracy in assessing stem fixation status compared with plain radiography.