Implementation of a novel MRI protocol for diagnosing femoral neck fractures in high energy femoral shaft fractures: One year results

MRI characteristics of radiographically occult femoral neck fractures in trauma patients with ipsilateral femoral shaft fractures

PURPOSE

Ipsilateral femoral neck fractures can be seen alongside femoral shaft fractures in high-velocity trauma patients. These neck fractures are often occult on radiographs and CT, and can have a significant impact on patient outcomes if not treated promptly. Limited protocol pelvic MRI has been used to increase sensitivity for these occult fractures. Detailed characterization of these fractures on MRI is lacking.

METHODS

427 consecutive trauma patients presenting to our emergency department who had known femoral diaphyseal fractures but no ipsilateral femoral neck fracture on radiographs or CT were included in this study. These patients were scanned using a limited protocol MRI with coronal T1 and coronal STIR sequences. Presence of an ipsilateral femoral neck fracture and imaging characteristics of the fracture were obtained.

RESULTS

31 radiographically occult ipsilateral femoral neck fractures were found, representing 7% of all cases. All neck fractures were incomplete. All fractures originated along the lateral cortex of the femoral neck and extended medially towards the junction of the medial femoral neck and the lesser trochanter. 58% (18/31) were vertical in orientation. 61% (19/31) did not demonstrate any appreciate edema on STIR images.

CONCLUSION

Implementation of limited protocol MRI protocol increases sensitivity for detection of femoral neck fractures in the setting of ipsilateral femoral shaft fractures not seen on radiograph or CT imaging. We describe the characteristic MR imaging features of these fractures.

Femoral shaft displacement and Winquist classification provide predictive characteristics for combined femoral neck and femoral shaft fractures

OBJECTIVES

The goal of this study is to establish radiographic features and characteristics of patient injury in cases of femoral shaft fractures that predict the presence of ipsilateral femoral neck fractures (IFNFs).

METHODS

Patient data was retrospectively assessed from a single level I trauma center through the electronic health record using (Current Procedural Terminology) CPT codes for both isolated and combined ipsilateral femoral shaft and neck fractures. Demographic information, injury characteristics, and independently reviewed radiographic features were collected and compared against the same information from a group of isolated femoral shaft fractures. Multivariable logistic regression was performed to identify risk factors for concomitant IFNFs and their respective odds ratios. A probability algorithm for assessing ipsilateral femoral neck fractures based on independent multivariate predictors was constructed and used.

RESULTS

A total of 113 patients with either isolated femoral shaft fractures or combined femoral shaft and IFNF (n = 33) met inclusion criteria and were identified for this study. Fracture displacement was most strongly associated with increased risk of combined injury with an aOR of 25.64 (95 %CI = 5.96-110.28) for every 100 % displacement. Motorcycle crash (MCC) was the mechanism associated with the highest risk of combined injury, with an aOR of 9.85 (95 % CI = 1.99-48.74). Combined injury was also correlated with lower Winquist score and presentation with a closed fracture, with aORs of 0.38 (95 %CI = 0.21 - 0.68) and 11.61 (95 %CI = 1.93-69.94), respectively. Presence of at least 3 of the statistically significant variables produced a positive predictive value (PPV) of ≥ 89 % for combined femoral shaft and IFNF.

CONCLUSIONS

Identification of combined femoral shaft and IFNF is of critical importance when caring for orthopedic trauma patients. While diagnosis remains a challenging task, MCC mechanism, >100 % fracture displacement, and lower Winquist classification were found to be associated with combined injuries. The combination of these variables might assist in predicting the probability of combined injury and potentially guide decision making on the appropriateness of obtaining single sequence MRI or implementing prophylactic femoral neck fixation.

LEVEL OF EVIDENCE

Level III.

High-energy Femoral Neck Fractures in Young Patients

Femoral neck fractures in physiologically young patients typically occur from high-energy axial loading forces through the thigh with the hip in an abducted position. These fractures have a high rate of associated head, chest, abdominal, and musculoskeletal injuries. High-energy hip fractures differ from traditional geriatric hip fractures regarding incidence, mechanism, management algorithms, and complications. After adequate resuscitation, goals of treatment include anatomic reduction and stable fixation while maintaining vascularity of the femoral head, which can be achieved through a variety of different techniques. Prompt recognition and treatment of these fractures is crucial to achieve a successful outcome because these injuries are often associated with complications such as osteonecrosis, fixation failure, and nonunion.

Characteristics of Femoral Shaft Fractures That Predict Ipsilateral Femoral Neck Fractures

INTRODUCTION

This study aims to characterize radiographic features and fracture characteristics in femoral shaft fractures with associated femoral neck fractures, with the goal of establishing predictive indicators for the presence of ipsilateral femoral neck fractures (IFNFs).

METHODS

A retrospective cohort was collected from the electronic medical record of three level I trauma centers over a 5-year period (2017 to 2022) by current procedural terminology (CPT) codes. Current CPT codes for combined femoral shaft and IFNFs were identified to generate our study group. CPT codes for isolated femur fractures were identified to generate a control group.

RESULTS

One hundred forty patients comprised our IFNF cohort, and 280 comprised the control cohort. On univariate, there were significant differences in mechanism of injury (P < 0.001), Orthopedic Trauma Association (OTA)/Arbeitsgemeinshaft fur Osteosynthesefragen (AO) classification (P = 0.002), and fracture location (P < 0.001) between cohorts. On multivariate, motor vehicle crashes were more commonly associated with IFNFs compared with other mechanism of injuries. OTA/AO 32A fractures were more commonly associated with IFNFs when compared with OTA/AO 32B fractures (adjusted odds ratio = 0.36, P < 0.001). Fractures through the isthmus were significantly more commonly associated with IFNFs than fractures more proximal (adjusted odds ratio = 2.52, P = 0.011).

DISCUSSION

Detecting IFNFs in femoral shaft fractures is challenging. Motor vehicle crashes and motorcycle collisions, OTA/AO type 32A fractures, and isthmus fractures are predictive of IFNFs.

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

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.

Do All Pediatric Femoral Shaft Fractures Need a Computed Tomography Scan of the Ipsilateral Femoral Neck? Calculating the Incidence of Concomitant Femoral Neck and Shaft Fractures

BACKGROUND

In adults, the incidence of ipsilateral femoral neck fractures in the setting of femoral shaft fractures is reported to be as high as 9%; however, scant literature exists on the same clinical scenario in pediatric/adolescent populations. Therefore, the purpose of this study was to investigate the incidence of ipsilateral femoral neck fracture in the setting of femoral shaft fractures in children and adolescents treated in pediatric hospitals across the United States.

METHODS

The Pediatric Health Information System database was queried for patients aged 18 years or younger who were treated for a femoral neck, femoral shaft, and pertrochanteric femur fractures through an emergency department, inpatient, ambulatory surgery, or observation visit. Patients were identified using ICD-9 and ICD-10 diagnosis codes. Data from 49 pediatric hospitals between the years 2002 and 2020 were included. Incidence was calculated as the number of cases including the event divided by the total number of cases.

RESULTS

A total of 90,146 records were identified from a cohort of 55,733,855 (0.16%). Distal femur fractures, pathologic fractures, and periprosthetic fractures were excluded, resulting in 65,651 unique cases. Of the 65,651 cases, 7104 (11%) were identified as isolated neck fractures. The combined incidence of femoral neck or pertrochanteric femur fractures in the setting of a femoral shaft fracture was 82.3 per 10,000 cases (0.82%). Only 283 cases of concomitant femoral neck and shaft fractures were found among 55,169 femoral shaft fractures (0.5%).

CONCLUSIONS

The incidence of ipsilateral femoral neck or pertrochanteric femur fractures in the setting of a femoral shaft fracture is 82.3 per 10,000 patients (0.82%) based on data from Pediatric Health Information System-participating institutions. The incidence of femoral neck/pertrochanteric femur fractures and femoral shaft fractures in children and adolescents is more than 10 times lower than reported for adults; therefore, the routine use of advanced diagnostic imaging in pediatric patients with femoral shaft fractures should be considered cautiously.

LEVEL OF EVIDENCE

Level IV; cross-sectional analysis.