High-energy Lateral Compression Type 1 Injuries of the Pelvis: A Spectrum of Injury

Standardization and Reproducibility of Dynamic Stress Testing for Occult Pelvic Ring Instability

INTRODUCTION

Examination under anesthesia (EUA) (stress fluoroscopy) is commonly done after pelvic ring injury to identify occult instability because unstable disruptions may displace causing morbidity. The force applied during EUA for these injuries has not been standardized. The purpose of this study was to examine the forces used during the EUA by experienced orthopaedic trauma pelvic surgeons.

METHODS

Orthopaedic traumatologists performed simulated EUA on a cadaver at two North American pelvis and acetabular courses using internal rotation (IR), external rotation, and push-pull maneuvers while wearing a handheld dynamometer to measure force. All surgeons used a comparable method, and each performed EUA multiple times. Maximum forces were measured in Newton (N).

RESULTS

Eighteen surgeons participated. Four had been practicing for <5 years, six for 5 to 10 years, six for 11 to 20 years, and two for >20 years. Surgeons applied a force ranging from 40.4 to 374.9 N during IR, 72.9 to 338.4 N during external rotation, and 25 to 323 N during push-pull, with notable variability seen between surgeons. Three surgeons (18%) had >50-N variability on serial trials of a single EUA maneuver (IR).

DISCUSSION

This is the first study evaluating the forces applied during pelvic EUA used to assess ring stability. Notable variability existed among surgeons performing EUA and in serial examinations by the same surgeon. Additional study is needed to standardize the displacement measured and threshold for instability that guides management.

Postmobilization Plain Radiography After Lateral Compression Type 1 Pelvic Ring Injury Does Not Affect Treatment

INTRODUCTION

The purpose of this study was to describe the practice of postmobilization radiography after lateral compression type 1 pelvis ring injury. We hypothesized that postmobilization radiographs would be more frequent over time and would not influence treatment.

METHODS

Displacement of pelvis ring injury on initial and final plain radiographs was measured. Frequency of postmobilization radiography was determined, and the impact on treatment and final radiographical outcome were assessed.

RESULTS

Of the 156 patients reviewed, 98 (62.8%) were women and mean age was 60.1 years. Thirty-three of 156 patients (21.2%) had a postmobilization radiograph. Over 5 years, radiographs increased to 67% of presenting patients. None of the patients who received postmobilization plain radiographs (n = 33) had any change in clinical plan afterward; all continued with nonsurgical care. Initial fracture characteristics and alignment were no different for patients with postmobilization radiographs. Final alignment was unchanged in nearly 70%. Overall, 74% of all nonsurgical patients experienced no change in alignment, with similar rates among the patients with postmobilization radiographs.

DISCUSSION

Patients with an lateral compression type 1 fracture demonstrated no changes in care after receiving postmobilization radiographs. However, the frequency of postmobilization radiographs increased over time, denoting opportunities to reduce costs and to improve efficiency and safety.

Comparing Emergency Department Stress of Lateral Compression Type 1 Pelvis Fractures With a Validated Instability Scoring System

INTRODUCTION

Lateral compression type 1 (LC1) pelvic ring injuries represent a heterogeneous group of fractures with controversial surgical indications. Recently, multiple institutions have suggested the safety and reliability of an emergency department (ED) stress to evaluate for occult instability. The purpose of this study was to correlate ED stress examination of LC1 pelvis fractures against a validated fracture instability scoring system.

METHODS

This was a retrospective review of a consecutive series of 70 patients presenting with minimally displaced LC1 fractures at a level 1 academic trauma center. All patients were stressed in the ED radiology suite, and displacement was measured by comparing calibrated stress radiographs with static radiographs (>10 mm displacement defined positivity). ED stress results were compared with radiographic scores assigned according to the validated Beckmann scoring system (score <7: stable-nonsurgical recommendation; score 7 to 9: indeterminant recommendation; and score >9: unstable-surgical recommendation).

RESULTS

Thirteen patients had a positive ED stress examination, and 57 patients stressed negative. The mean displacement was significantly different between the three groups (Beckmann 5 to 6: 3.31 mm, SD = 2.4; Beckmann 7 to 9: 4.23 mm, SD = 3.2; Beckmann 10+: 12.1 mm, SD = 8.6; P < 0.001). Zero of 18 patients in the stable group stressed positive, and only 3 of 38 patients in the indeterminant group stressed positive (7.9%). Finally, 10 of 14 patients in the unstable group stressed positive (71.4%; P < 0.001). Sacral displacement (P = 0.001), superior ramus location (P < 0.02), and sacral columns (P < 0.001) significantly predicted ED stress positivity in multivariate analysis.

CONCLUSIONS

Comparison of a validated instability scoring system with ED stress examination of minimally displaced LC1 fractures in awake and hemodynamically stable patients showed excellent correlation. This suggests that the ED stress examination is a useful diagnostic adjunct. LC1 fracture characteristics should be analyzed to determine which pelvic fracture characteristics determine occult instability before stress examination.

LEVEL OF EVIDENCE

Level III diagnostic.

Dual-Energy CT and Cinematic Rendering to Improve Assessment of Pelvic Fracture Instability

Background Grading of pelvic fracture instability is challenging in patients with pelvic binders. Dual-energy CT (DECT) and cinematic rendering can provide ancillary information regarding osteoligamentous integrity, but the utility of these tools remains unknown. Purpose To assess the added diagnostic value of DECT and cinematic rendering, with respect to single-energy CT (SECT), for discriminating any instability and translational instability in patients with pelvic binders. Materials and Methods In this retrospective analysis, consecutive adult patients (age ≥18 years) were stabilized with pelvic binders and scanned in dual-energy mode using a 128-section CT scanner at one level I trauma center between August 2016 and January 2019. Young-Burgess grading by orthopedists served as the reference standard. Two radiologists performed blinded consensus grading with the Young-Burgess system in three reading sessions (session 1, SECT; session 2, SECT plus DECT; session 3, SECT plus DECT and cinematic rendering). Lateral compression (LC) type 1 (LC-1) and anteroposterior compression (APC) type 1 (APC-1) injuries were considered stable; LC type 2 and APC type 2, rotationally unstable; and LC type 3, APC type 3, and vertical shear, translationally unstable. Diagnostic performance for any instability and translational instability was compared between reading sessions using the McNemar and DeLong tests. Radiologist agreement with the orthopedic reference standard was calculated with the weighted κ statistic. Results Fifty-four patients (mean age, 41 years ± 16 [SD]; 41 men) were analyzed. Diagnostic performance was greater with SECT plus DECT and cinematic rendering compared with SECT alone for any instability, with an area under the receiver operating characteristic curve (AUC) of 0.67 for SECT alone and 0.82 for SECT plus DECT and cinematic rendering (P = .04); for translational instability, the AUCs were 0.80 for SECT alone and 0.95 for SECT plus DECT and cinematic rendering (P = .01). For any instability, corresponding sensitivities were 61% (22 of 36 patients) for SECT alone and 86% (31 of 36 patients) for SECT plus DECT and cinematic rendering (P < .001). The corresponding specificities were 72% (13 of 18 patients) and 78% (14 of 18 patients), respectively (P > .99). Agreement (κ value) between radiologists and orthopedist reference standard improved from 0.44 to 0.76 for SECT versus the combination of SECT, DECT, and cinematic rendering. Conclusion Combined use of single-energy CT, dual-energy CT, and cinematic rendering improved instability assessment over that with single-energy CT alone. © RSNA, 2022 Online supplemental material is available for this article.

Pelvic ring injuries after alpine ski and snowboard accidents

PURPOSE

The purpose of this study was to analyze the patient/injury characteristics and associated hospital course of patients sustaining traumatic pelvic ring injuries after alpine ski and snowboard accidents at a level one trauma center in the Rocky Mountain region.

METHODS

Patient/injury characteristics were obtained from patients presenting with pelvic ring injuries after alpine ski (n = 55) and snowboard (n = 9) accidents. Characteristics and outcomes analyzed included mechanism of injury, pelvic ring classification (Young-Burgess and Tile), hospital admission, physical therapy (PT) clearance, ambulation, length of stay, inpatient morphine milligram equivalents (MME), and discharges to rehabilitation facility.

RESULTS

Snowboarders were more often younger, male, tobacco/substance users, and more likely to be injured by a fall from height than skiers. There were no differences in injury classification or hospital course outcomes between alpine sports. Most common injuries included lateral compression type 1 (LC1) injuries (37.5%), isolated pubic ramus fractures (31.3%), and isolated iliac wing fractures (15.6%). LC1 injuries were unstable in 50% of cases and associated with increased admissions (proportional difference: 47.5%, CI: 23.8-64.5%, p = 0.0002), longer time to PT clearance (median difference(MD): 1.0 day, CI: 0-2.0, p = 0.03), longer LOS (MD: 2.0, CI: 0-2.0, p = 0.02), and increased inpatient MMEs (MD: 197.9 MME, CI: 30.0-420.0, p = 0.02), as compared to other pelvic ring injuries.

CONCLUSION

The majority of pelvic ring injuries from alpine ski and snowboard accidents were LC1 injuries, half of which were unstable, resulting in longer hospital stays, time to PT clearance/ambulation, and opioid use.

Emergency Department Stress Radiographs of Lateral Compression Type-1 Pelvic Ring Injuries Are Safe, Effective, and Reliable

BACKGROUND

Occult instability of lateral compression type-1 (LC1) pelvic ring injuries may be determined with a fluoroscopic stress examination under anesthesia (EUA) performed in the operating room. We hypothesized that LC1 injuries, similar to some fractures of the extremities, could be radiographically stressed for stability in the emergency department (ED). Our primary objective was to determine if stress examination of LC1 fractures could be safely and accurately performed in the ED and could be tolerated by patients.

METHODS

A prospective, consecutive series of 70 patients with minimally displaced LC1 pelvic injuries (<10-mm displacement on presentation) underwent stress examinations performed by the on-call orthopaedic resident in the ED radiology suite. The stress examination series included static 40° inlet, internal rotation stress inlet, and external rotation stress inlet views. Pelvic fractures that had positive stress results (≥10 mm of overlap of the rami) were indicated for a surgical procedure. These fractures also underwent EUA in order for the 2 techniques to be compared.

RESULTS

All patients tolerated the ED stress examination without general anesthetic or hemodynamic instability. Fifty-seven patients (81%) had negative stress results and were allowed to bear weight. All patients with negative stress results who had 3-month follow-up went on to radiographic union without substantial displacement. For the patients with a positive stress result in the ED, the mean displacement was 15.15 mm (95% confidence interval [CI], 10.8 to 19.4 mm) for the ED stress test and 15.60 mm (95% CI, 11.7 to 19.4 mm) for the EUA (p = 0.86). Two patients with a negative ED stress test did not mobilize during their hospitalization and underwent EUA and conversion to a surgical procedure. Thus, a total of 11 patients underwent both stress testing in the ED and EUA; no patient had a positive result on one test but a negative result on the other.

CONCLUSIONS

ED stress examination of LC1 injuries is a safe and reliable method to determine pelvic ring stability. The displacement measured in the ED stress examination is similar to the displacement measured under general anesthesia. Furthermore, a negative ED stress examination predicts successful nonoperative treatment. Given the results of this study, we encourage the use of stress examination in the ED for LC1-type injuries involving complete sacral fractures only. Widescale adoption of this streamlined protocol may substantially diminish cost, anesthetic risk, and potential operations for patients.

LEVEL OF EVIDENCE

Diagnostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Contributions of Pubic Rami Fracture Morphology and Fixation to Pelvic Ring Stability in Type 1 Lateral Compression Injuries: A Biomechanical Cadaveric Study

BACKGROUND

Treatment of lateral compression type 1 (LC-1) injuries has historically been nonoperative with immediate weight-bearing. However, management of these injuries remains controversial, with reports of displacement at follow-up for nonoperatively managed LC-1 fractures. The goal of our study was to determine the effect of superior pubic ramus fracture morphology and fixation construct on pelvic stability.

METHODS

Ten fresh-frozen cadaveric were transected into hemi-pelvises. Incomplete Denis type 1 sacral fractures were made. Hemi-pelvises were randomized to receive a transverse-type or oblique-type superior pubic ramus fracture with the contralateral hemi-pelvis receiving the opposing morphology. A lateral load to 135N was applied with an Instron materials testing machine and lateral displacement of the hemi-pelvis was recorded. Deflection and stiffness were calculated. Statistical analysis was conducted using a t test assuming unequal variances with an alpha = 0.05.

RESULTS

Oblique-type superior pubic ramus fractures allowed more deflection compared with transverse-type fractures in the absence of fixation (P = 0.018). The posterior-only and combined anterior and posterior fixation configurations on average reduced deflection more than no fixation or anterior fixation only. In all fixation configuration cases, the average deflection for transverse-type fractures was less than that of the oblique-type fractures.

CONCLUSIONS

Our findings suggest that displacement of LC-1 pelvic injuries may be related to pubic rami fracture morphology. When looking at initial injury imaging, oblique-type pubic rami fractures may suggest an increased potential for displacement over time. In such cases, we recommend an examination under anesthesia to evaluate for underlying instability and consideration for fixation.

LEVEL OF EVIDENCE

Therapeutic Level V.

Unstable minimally displaced lateral compression type 1 (LC1) pelvic ring injuries have a similar hospital course as intertrochanteric femur fractures

INTRODUCTION

The purpose of this study was to evaluate how the hospital course of minimally displaced LC1 fractures, with and without occult instability, compares with that of intertrochanteric femur fractures.

PATIENTS AND METHODS

Retrospective comparative cohort analysis at an urban level one trauma center of 40 consecutive patients with an isolated LC1 pelvic ring injury and 40 age/sex matched patients with an isolated intertrochanteric femur fracture was performed. Medical records and radiographs were reviewed for patient and injury characteristics, including demographics, displacement, time to surgery, ambulation, physical therapy (PT) clearance, hospital length of stay (LOS), and inpatient morphine milligram equivalents (MME).

RESULTS

The LC1 pelvic ring injury group included 26 (65%) patients with ≥ 10 mm of displacement on lateral stress radiographs. The unstable LC1 group, compared to the stable LC1 group, had a greater LOS (median difference (MD): 2 days, 95% confidence interval (CI): 1 to 4, p = 0.0004), longer time to ambulate 15 feet (MD: 1 day, CI: 1 to 2, p = 0.0002), longer time to clear PT (MD: 2 days, CI: 1 to 3, p = 0.0003), and more inpatient MMEs (MD: 386 MME, CI: 225.8 to 546.7, p = 0.0002). The unstable LC1 and intertrochanteric fracture groups had no detectable differences in LOS (p = 0.24), days to ambulate 15 feet (p = 0.46), days to clear PT (p = 0.95), and inpatient MMEs (p = 0.06).

CONCLUSION

Patients with minimally displaced unstable LC1 injuries had worse hospital courses than stable LC1 injuries and similar hospital courses as intertrochanteric femur fractures. These findings emphasize the associated morbidity of unstable LC1 injuries.

LEVEL OF EVIDENCE

Level III, Retrospective cohort study.

The morphological mapping of lateral compression type 1 pelvic fracture and pelvic ring stability classification: a finite element analysis

Purpose

This finite element analysis assessed lateral compression (LC-1) fracture stability using machine learning for morphological mapping and classification of pelvic ring stability.

Methods

Computed tomography (CT) files of LC-1 pelvic fractures were collected. After morphological mapping and producing matrix data, we used K-means clustering in unsupervised machine learning to classify the fractures. Based on these subtypes, we manually added fracture lines in ANSYS software. Finally, we performed a finite element analysis of a normal pelvis and eight fracture subtypes based on von Mises stress and total deformation changes.

Results

A total of 218 consecutive cases were analyzed. According to the three main factors—zone of sacral injury and completion, pubic ramus injury side, and the sagittal rotation of the injured hemipelvis—the LC-1 injuries were classified into eight subtypes (I–VIII). No significant differences in stress or deformation were observed between unilateral and bilateral public ramus fractures. Subtypes VI and VIII showed the maximum stress while subtypes V–VIII showed the maximum deformation in the total pelvis and sacrum. The subtypes did not differ in superior public ramus deformation.

Conclusions

Complete fracture of sacrum zones 2/3 may be a feature of unstable LC-1 fractures. Surgeons should give surgical strategies for subtypes V–VIII.

Functional outcomes of the anterior subcutaneous internal pelvic fixator (INFIX) technique for pelvic ring injuries: A case series

INTRODUCTION

Anterior external fixation is a well-established technique for treating pelvic ring injuries, but many complications are associated with it. The subcutaneous anterior internal fixator (INFIX) technique is associated with reduced complication rates and is less uncomfortable for patients.

OBJECTIVE

This study evaluated functional outcomes among patients with pelvic ring injuries treated using the INFIX method.

PATIENTS AND METHODS

In this retrospective case series, patients treated using the INFIX technique were reviewed for functional outcomes, using the Iowa Pelvic Score (IPS). Thirty-four patients, of mean age 39.2 years, were evaluated after a mean follow-up of 1.2 years.

RESULTS

Twenty-three of the 34 patients experienced reduction classified as excellent, and eleven as good, with no instances of moderate or poor reduction. One patient developed implant exposure and infection during follow-up. Twenty-six ultimately experienced an excellent or good functional result. The average final IPS was 79.4 (range: 48-100).

CONCLUSION

Our results reinforce prior evidence that the INFIX method is safe for fixating pelvic ring lesions. Most of our patients also experienced excellent or good functional recovery, suggesting that this technique is a viable option for treating certain pelvic ring injuries.

Bladder incarceration within a displaced pelvic ring nonunion

Pelvic ring injuries can be challenging to manage and may have a range of associated injuries. When bladder injuries occur in combination with pelvic ring fractures, a multidisciplinary approach may be required to plan the best course of treatment. Acute entrapment or injury to the urinary bladder after a pelvic fracture is well reported. Here, we present an interesting case of chronic bladder incarceration within a lateral compression pelvic ring injury nonunion after failed nonoperative management of the initial pelvis fracture. Treatment of the nonunion was complicated by an incidental diagnosis of lymphoma.

Lateral compression type 1 (LC1) pelvic ring injuries: a spectrum of fracture types and treatment algorithms

Lateral compression type 1 (LC1) fractures are the commonest pelvic ring injury. However, they represent a heterogenous spectrum of injury mechanisms and fracture patterns, resulting in a lack of strong evidence for a universally agreed treatment algorithm. Although consensus exists that LC1 fractures have a preserved posterior ligamentous complex and are vertically stable, controversy persists around defining internal rotational instability. As such, treatment strategies extend from routine non-operative management through to dynamic imaging such as examination under anaesthetic (EUA) or stress radiographs to guide fixation algorithm. Multiple protocols sit between these two, all with slightly different thresholds for advocating surgery or otherwise, exemplifying a broad lack of consensus that is not seen for other, more severe, grades of pelvic ring injury. In the following review we discuss the evolving concepts of pelvic ring instability and management, starting from a historical perspective, through to current trends and controversies in LC1 fracture treatment. Emerging directions for research and emerging pharmacological and surgical treatments/technologies are also considered and expert commentary from 3 leading centres provided. The distinction is made between LC1 fracture arising from high-energy trauma and those following low-energy falls from standing height (so-called fragility fractures of the pelvis-FFP), since these two patient groups have different functional requirements and medical vulnerabilities. Issues pertaining to FFP are considered separately.