Capsular distension in high-energy femoral shaft fractures is associated with occult femoral neck fracture: a preliminary retrospective comparative study

Michael J Chen; Annelise Chaparro; Michael S Elder Waters; Firoozeh Shomal Zadeh; Majid Chalian; Daphne M Beingessner; David P Barei

doi:10.1007/s00590-023-03696-7

Capsular distension in high-energy femoral shaft fractures is associated with occult femoral neck fracture: a preliminary retrospective comparative study

Eur J Orthop Surg Traumatol. 2024 Jan;34(1):599-604. doi: 10.1007/s00590-023-03696-7. Epub 2023 Sep 3.

Authors

Michael J Chen¹, Annelise Chaparro², Michael S Elder Waters², Firoozeh Shomal Zadeh³, Majid Chalian³, Daphne M Beingessner², David P Barei²

Affiliations

¹ Department of Orthopaedic Surgery, University of Hawaii, 1356 Lusitana Street, 6th Floor, Honolulu, HI, 96813, USA. mchen@islandorthopaedics.com.
² Department of Orthopaedic Surgery, Harborview Medical Center, Seattle, WA, USA.
³ Department of Radiology, University of Washington, Seattle, WA, USA.

PMID: 37660313
DOI: 10.1007/s00590-023-03696-7

Abstract

Objectives: To determine the association between hip capsular distension, the computed tomography (CT) capsular sign, and lipohemarthrosis as they relate to occult femoral neck fracture (FNF) in the setting of ipsilateral femoral shaft fracture (FSF).

Design: Retrospective comparative study.

Setting: Level 1 trauma center.

Patients/participants: Two hundred and forty-two patients with high-energy FSF and no evidence of FNF on preoperative radiographs and pelvis CT. All patients were stabilized with non-reconstruction style nails.

Intervention: Pelvis CT scans were examined for hip capsular distension irrespective of the other side, differing side-to-side measurements of capsular distension (i.e., the CT capsular sign), and lipohemarthrosis.

Main outcome measurements: FNF was observed for on postoperative radiographs. Relative risk (RR), number needed to treat (NNT), sensitivity (SN), and specificity (SP) were determined.

Results: Fifty-eight patients (24.0%) had capsular distension. Forty-two patients (17.4%) had differing capsular measurements (i.e., the CT capsular sign), and 16 (6.6%) had symmetrical distension from bilateral hip effusions. Eight patients (3.3%) had lipohemarthrosis. Four FNFs (1.7%) were identified. Three patients had capsular distension, 2 had CT capsular signs, and 1 had lipohemarthrosis. The last patient had no CT abnormalities. Only capsular distension (RR = 10, CI = 1.001-90, P = 0.049; SN = 75%, SP = 77%; NNT = 22) and lipohemarthrosis (RR = 23, CI = 1.6-335, P = 0.022; SN = 50%, SP = 96%; NNT = 8) were associated with occult FNF.

Conclusions: Capsular distension is associated with FNF irrespective of the contralateral hip. Preemptive stabilization using a reconstruction nail could be considered in the setting of capsular distension or lipohemarthrosis to prevent displacement of an occult FNF.

Level of evidence: Diagnostic Level III.

Keywords: Capsular distension; Femoral neck fracture; Femoral shaft fracture; Hip effusion; Lipohemarthrosis; Occult femoral neck fracture.

MeSH terms

Femoral Fractures* / complications
Femoral Fractures* / diagnostic imaging
Femoral Fractures* / surgery
Femoral Neck Fractures* / complications
Femoral Neck Fractures* / diagnostic imaging
Femoral Neck Fractures* / surgery
Humans
Radiography
Retrospective Studies
Tomography, X-Ray Computed / methods