CT-guided infiltration of the ischiofemoral space in young patients with ischiofemoral impingement is an effective diagnostic tool.

Objectives: To present our technique of diagnostic CT-guided ischiofemoral space injection and report on pain response, complications, and associated imaging findings in young patients with ischiofemoral impingement (IFI).

Methods: Retrospective case series of patients with a clinical diagnosis of IFI that underwent CT-guided IFS injection with local anesthetic in a prone position with the feet in maximum internal rotation between 06/2019 and 04/2021. The response was evaluated using maximum subjective pain evaluation on a 0-10 visual analog scale (VAS) during a standardized pre- and postinterventional clinical examination. Patient charts and radiographic imaging data were reviewed to report associated imaging findings and subsequent surgeries.

Results: Eleven patients (13 hips, 9 females) with a median age of 31 years (interquartile range; IQR: 25-37 years) were included. Median baseline VAS was 7 points (IQR: 5-8) with a pain reduction of 5 points (IQR: 5-7 points, p = 0.001) after the injection. One patient reported transient ischial nerve paresthesia, otherwise, no complications occurred. Quadratus femoris muscle edema was present in 85% (11 of 13 hips). Excessively high femoral torsion (11/13 hips, 85%) and cam deformities (8/13 hips, 62%) were the most common osseous deformities. Eight of 13 hips (62%) underwent subsequent surgery for IFI.

Conclusion: CT-guided diagnostic injection of the ischiofemoral space is safe and feasible. In young IFI patients, diagnostic IFS injections have the potential to improve the differential diagnosis of hip pain and to inform decision-making with regard to a possible benefit of joint-preserving hip surgery.

Critical relevance statement: In young patients with hip pain, diagnosis of IFI can be challenging due to concomitant pathologies. Furthermore, surgical treatment in these patients is controversial. In this context, CT-guided diagnostic infiltrations of the ischiofemoral space may facilitate not only the initial diagnosis of IFI, but could also improve surgical decision-making.

Key points: CT-guided diagnostic injection of local anesthetic in the ischiofemoral space is safe. In young patients with IFI, it leads to subjective pain reduction. In young patients with concomitant osseous deformities, it may improve surgical decision-making.