Does local fat thickness correlate with post-operative infection in open reduction and internal fixation of acetabulum fractures?

PURPOSE: Obesity is an epidemic which increases risk of many surgical procedures. Previous studies in spine and hip arthroplasty have shown that fat thickness measured on preoperative imaging may be as or more reliable in assessment of risk of post-operative infection and/or wound complications than body mass index (BMI). We hypothesized that, similarly, increased local fat thickness at the surgical site is a predictor of wound complication in acetabulum fracture surgery. METHODS: Patients who underwent open reduction and internal fixation (ORIF) of an acetabulum fracture through a Kocher-Langenbeck (K-L) approach at a single institution from 2013 to 2020 were identified. Pre-operative CT scans were used to measure fat thickness from the skin to the greater trochanter in line with the surgical approach. Post-operative infections and wound complications were recorded and associated with fat thickness and BMI. RESULTS: 238 patients met inclusion criteria. 12 patients had either infection or a wound complication (5.0%). There was no significant association with BMI or preoperative fat thickness on post-operative infection or wound complication (p-value 0.73 and 0.86). CONCLUSIONS: There is no statistically significant association of post-operative infection or wound complications in patients with increased soft tissue thickness or increased BMI. ORIF of acetabulum fractures through a K-L approach can be performed safely in patients with large subcutaneous fat thickness and high BMI with low risk of infection or wound complications.

Obstetricians are likely to elect for cesarean section in women with retained pelvic implants: a radiographic survey study.

PURPOSE: Women with a history of pelvic fracture undergo cesarean section (CS) at a higher rate than the general population. The purpose of our study is to query obstetricians on their preferences. METHODS: An electronic survey consisting of 22 radiographs of patients who underwent pelvic fixation was sent to obstetricians at 3 academic medical centers. For each radiograph, a hypothetical scenario was given, and the respondents were asked if they would elect for a vaginal delivery or CS. RESULTS: We collected 58 responses. The overall CS rate was 59%. Respondents were significantly more likely to elect for CS with trans-symphyseal fixation or sacroiliac fixation, independently (p < 0.001). DISCUSSION: Obstetricians are likely to elect for elective CS in the presence of pelvic implants especially in patients with trans-symphyseal and sacroiliac fixation. Based on there is an opportunity for collaboration between orthopedic trauma surgeons and obstetricians.

Use of 3D Fluoroscopy to Assist in the Reduction and Fixation of Pelvic and Acetabular Fractures: A Safety and Quality Case Series.

SUMMARY: Multidimensional fluoroscopy has been increasingly used in orthopaedic trauma to improve the intraoperative assessment of articular reductions and implant placement. Owing to the complex osteology of the pelvis, cross-sectional imaging is imperative for accurate evaluation of pelvic ring and acetabular injuries both preoperatively and intraoperatively. The continued development of fluoroscopic technology over the past decade has resulted in improved ease of intraoperative multidimensional fluoroscopy use in pelvic and acetabular surgery. This has provided orthopaedic trauma surgeons with a valuable tool to better evaluate reduction and fixation at different stages during operative treatment of these injuries. Specifically, intraoperative 3D fluoroscopy during treatment of acetabulum and pelvis injuries assists with guiding intraoperative decisions, assessing reductions, ensuring implant safety, and confirming appropriate fixation. We outline the useful aspects of this technology during pelvic and acetabular surgery and report its utility with a consecutive case series at a single institution. The added benefits of this technology have improved the ability to effectively manage patients with pelvis and acetabulum injuries.

Imaging of Pelvic and Acetabular Trauma: Part 2, Soft-Tissue Findings.

Pelvic ring injuries and acetabular fractures can be complex and challenging to treat. Orthopaedic trauma surgeons scrutinize pelvic radiographs and accompanying CT images for the osseous details that help create a thorough patient-specific preoperative plan. While the osseous details are incredibly important, the surrounding soft-tissue structures are equally as critical and can have a tremendous effect on both the patient and the surgeon. These findings may change surgery timing, dictate the need for additional surgeons or multidisciplinary teams, and determine the treatment sequence. The structures and potential clinical findings reviewed and demonstrated through example images should be sought out during physical examination and correlative preoperative imaging review. Combining all the available osseous and nonosseous information with a detailed approach helps the surgeon predict potential pitfalls and adjust surgical plans before incision. Maximizing the accuracy of the preoperative planning process can streamline treatment algorithm development and ultimately contribute to the best possible clinical patient outcome.

Oblique anterior pelvic external fixator for intraoperative reduction of rotationally unstable pelvic ring injuries.

Incomplete sacroiliac joint injuries are often associated with external rotation and extension deformities on the injured hemipelvis. To appropriately correct this deformity, an oblique reduction force from caudal to cranial and lateral to medial is helpful. These injuries are often associated with traumatic disruption of the pubic symphysis. However, in injuries without traumatic disruption to the pubic symphysis, a two-pin oblique anterior external fixator can be used to obtain and maintain reduction of the sacroiliac joint, while percutaneous fixation is subsequently placed. Through a small case series and three specific patient examples, we demonstrate that the oblique anterior external fixator frame is a simple and effective strategy with the reduction and stabilization process of these multiplanar hemipelvis deformities.

Assessment of sacral osseous fixation pathways for same-level dual transiliac-transsacral screw insertion.

INTRODUCTION: The purpose of this study is to (1) describe a pre-operative planning technique using non-reformatted CT images for insertion of multiple transiliac-transsacral (TI-TS) screws at a single sacral level, (2) define the parameters of a sacral osseous fixation pathway (OFP) that will allow for insertion of two TI-TS screws at a single level, and (3) identify the incidence of sacral OFPs large enough for dual-screw insertion in a representative patient population. METHODS: Retrospective review at a level-1 academic trauma center of a cohort of patients with unstable pelvic injuries treated with two TI-TS screws in the same sacral OFP, and a control cohort of patients without pelvic injuries who had CT scans for other reasons. RESULTS: Thirty-nine patients had two TI-TS screws at S1. Eleven patients, all with dysmorphic osteology, had two TI-TS screws at S2. The average pathway size in the sagittal plane at the level the screws were placed was 17.2 mm in S1 vs 14.4 mm in S2 (p = 0.02). Twenty-one patients (42%) had screws that were intraosseous and 29 (58%) had part of a screw that was juxtaforaminal. No screws were extraosseous. The average OFP size of intraosseous screws was 18.1 mm vs. 15.5 mm for juxtaforaminal screws (p = 0.02). Fourteen millimeters was used as a guide for the lower limit of the OFP for safe dual-screw fixation. Overall, 30% of S1 or S2 pathways were ≥ 14 mm in the control group, with 58% of control patients having at least one of the S1 or S2 pathways ≥ 14 mm. CONCLUSIONS: OFPs ≥ 7.5 mm in the axial plane and 14 mm in the sagittal plane on non-reformatted CT images are large enough for dual-screw fixation at a single sacral level. Overall, 30% of S1 and S2 pathways were ≥ 14 mm and 58% of control patients had an available OFP in at least one sacral level.

Upper sacral segment fixation with converging iliosacral screws: A technical trick for preoperative planning and case series.

INTRODUCTION: There are some situations where pelvic surgeons may want to place iliosacral screws with differing trajectories (Sacroiliac and Sacral styles) but may not be able to because of overlapping trajectories. HYPOTHESIS: Sacroiliac and Sacral style screws can be placed in S1 in select patients by using a preoperative planning technique off the 3D reconstructed surface rendered preoperative CT scan. MATERIALS/METHODS: Retrospective review of all patients receiving iliosacral screws using the described technique. RESULTS: Six patients received iliosacral screws using the described technique. When the preoperative planning technique demonstrated feasibility, all screws were able to be safely placed. DISCUSSION: Placing Sacroiliac and Sacral style screws within S1 may be ideal in some injury patterns. The described technique allows pelvic surgeons facile in iliosacral screw techniques to preoperatively plan for this construct. LEVEL OF EVIDENCE: VI; Retrospective case series.

Superior gluteal artery injury risk from third sacral segment transsacral screw insertion.

OBJECTIVES: Iliosacral (IS) and transsacral (TS) screws are commonly used to stabilize pelvic ring injuries. The course of the superior gluteal artery (SGA) can be close to implant insertion paths. The third sacral segment (S3) has been described as a viable osseous fixation pathway (OFP) but the proximity of the SGA to the S3 screw path is unknown. METHODS: Fifty uninjured patients with contrasted pelvic computed tomograms (CTA) were identified with an S3 path large enough for a 7.0 mm TS screw. Starting sites for S1 IS or TS, S2 and S3 TS screws were located on the volume rendered lateral CTA image and transferred onto the surface rendered 3D CTA with the SGA clearly visible. The distance from screw start sites to the SGA was measured. A distance less than 3.5 mm was considered likely for injury. RESULTS: The average distances from screw start sites to the SGA were 23.0 ± 7.9 mm for S1 IS screws, 14.3 ± 6.4 mm for S2 TS screws and 25.9 ± 6.5 mm for S3 TS screws. No S1 IS screws, 5 S2 TS screws (10%), and no S3 TS screws were projected to cause injury to the SGA. CONCLUSIONS: The osseous start site and soft tissue path for an S3 TS screw is remote from the SGA. The S1 IS and S3 TS pathways are further away from the SGA while the S2 TS pathway is closer and may theoretically pose a higher injury risk in patients with an available S3 OFP.

Posterior Wall Acetabulum Fracture with a Persistent Sciatic Artery: A Case Report.

CASE: We report the case of a patient who sustained a left posterior wall acetabular fracture with an ipsilateral persistent sciatic artery (PSA). The PSA was diagnosed preoperatively on lower extremity computed tomography angiogram. He was treated with open reduction internal fixation through a Kocher-Langenbeck approach. The PSA and sciatic nerve were identified and protected throughout the case. There were no neurovascular complications. CONCLUSION: PSA in the setting of posterior wall acetabulum fractures has not been reported previously. Orthopaedic surgeons who treat these injuries should be aware of PSA anatomic variants so that they can be identified and protected during surgery.

Similar patient reported outcomes at long-term follow-up after external fixation versus internal fixation of the anterior ring component of APC injuries.

PURPOSE: Unstable pelvic ring injuries produced by external rotation of the hemipelvis and a symphyseal disruption are most often treated with internal fixation of the anterior ring, with percutaneous treatment of the posterior ring as needed. In some clinical situations, patients are treated with external fixation for their anterior injuries and the long-term functional outcomes associated with external fixation are not well understood. We ask if there is a difference in functional outcome, between treatment of these injuries with internal versus external fixation, when measured at a minimum of three years after injury. METHOD: This was a retrospective cohort study performed at a level one regional trauma center. Trauma database review identified 128 patients, with 70 subsequently excluded, with unstable anterior posterior compression (APC) pelvic ring injuries (OTA 61B2.3 & 61C1.2) treated with surgery with minimum three years of follow-up. An intervention of internal fixation versus external fixation of anterior pelvic ring was performed, and depending on the injury, supplemented with posterior iliosacral screw fixation. Main outcome was measured with the Majeed functional outcome score (0-100). RESULTS: Patients treated with external fixation reported a Majeed score of 70 (95% CI 28-100) compared to 79 (95% CI 36-100) in those with internal fixation (p-value 0.28). Subgroups of the Majeed score were not significantly different (p value > 0.05). Open fractures, severity of injury, and ISS were worse in those treated with external fixation. There was no differential loss to follow-up. Conclusion Patients with unstable pelvic ring injuries with symphyseal disruptions treated with external fixation as definitive treatment versus internal fixation may fare no different in the long term.

Morbid obesity and short-term complications following acetabular fracture surgery: A comparative cohort study.

INTRODUCTION: Obesity is an epidemic facing the United States affecting nearly 40% of the population (93.3 million adults). The objective of this study was to compare early perioperative complications in patients with a normal BMI to patients who are pre-obese, obese, and morbidly obese. MATERIALS AND METHODS: The study was conducted at a Level-I trauma center. Patients were separated into 4 groups based on their BMI. Group 1 had a BMI < 25 (normal), Group 2 had a BMI between 25-29.9 (pre-obesity), Group 3 had a BMI between 30-39.9 (obese), and Group 4 had a BMI ≥40 (morbidly obese). Outcome variables included total operative time (OT), estimated blood loss (EBL), length of stay (LOS), and early medical and surgical complications. A comparison between groups was performed for each outcome variable and surgical complication. RESULTS: We identified 333 patients and the number of patients in Groups 1-4 were 86, 96, 121, and 30, respectively. The average BMI for Groups 1-4 was 22.3, 27.3, 35.9, and 44.9, respectively (p < 0.001). OT, EBL, and LOS did not differ between groups or between the surgical approach utilized. There were no significant relationships when comparing complication rates between groups. Patients in Group 4 experienced significantly more PE compared to patients in Group 2 (p=0.01). Additionally, patients in Group 4 experienced a significantly more PE than patients in Groups 1 and 2 combined (p<.01). The relative risk of having a PE if BMI is ≥40, compared to a BMI <30 is 18.40 (95% CI = 1.98 - 171.13). The PEs were not fatal in all cases. CONCLUSIONS: In the treatment of the obese and morbidly obese with acetabular fractures, we find that these cohorts are not at a greater risk of wound complications or infection. The higher rate of pulmonary embolism seen in the morbidly obese should be considered when evaluating these patients for appropriate thromboembolic prophylaxis.

Improving the Diagnosis of Ipsilateral Femoral Neck and Shaft Fractures: A New Imaging Protocol.

BACKGROUND: Despite increased awareness of ipsilateral femoral neck fractures in patients with high-energy femoral shaft fractures and advanced imaging with thin-cut high-resolution computed tomography (CT), failure of diagnosis remains problematic. The purpose of the present study was to determine if the preoperative diagnosis of ipsilateral femoral neck fractures in patients with high-energy femoral shaft fractures can be improved with magnetic resonance imaging (MRI) compared with radiographic and CT imaging. METHODS: In response to delayed diagnoses of femoral neck fractures despite thin-cut high-resolution CT, our institutional imaging protocol for acute, high-energy femoral shaft fractures was altered to include rapid limited-sequence MRI to evaluate for occult femoral neck fractures. All patients received standard radiographic imaging as well as thin-cut high-resolution pelvic CT imaging upon presentation. Rapid limited-sequence MRI of the pelvis was obtained to evaluate for an occult femoral neck fracture. RESULTS: Thirty-seven consecutive patients with 39 acute, high-energy femoral shaft fractures resulting from blunt trauma were included. The average age of the patients was 29.1 years (range, 14 to 82 years). Ten (25.6%) of the 39 femoral shaft fractures were open. Two femoral shaft fractures (5.1%) were associated with ipsilateral femoral neck fractures that were detected on radiographs, and no MRI was performed. None of the remaining 37 femoral shaft fractures were associated with a femoral neck fracture that was identified on CT imaging. Thirty-three (89.2%) of 37 patients underwent pelvic MRI to evaluate the ipsilateral femoral neck. Four (12.1%) of those 33 patients were diagnosed with a femoral neck fracture (2 complete, 2 incomplete) that was not identified on thin-cut high-resolution CT or radiographic imaging. CONCLUSIONS: Rapid limited-sequence MRI of the pelvis for patients with femoral shaft fractures identified femoral neck fractures that were not diagnosed on thin-cut high-resolution CT in 12% of our patients. Our results suggest that the frequency of femoral neck fractures may be underrepresented on CT imaging; rapid limited-sequence MRI was feasible without delaying definitive treatment even in polytraumatized patients. LEVEL OF EVIDENCE: Diagnostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Surgery for Unilateral Sacral Fractures: Are the Indications Clear?

OBJECTIVES: To evaluate unilateral sacral fractures and compare those treated operatively versus nonoperatively to determine indications for surgery. DESIGN: Prospective, multicenter, observational study. SETTING: Sixteen trauma centers. PATIENTS/PARTICIPANTS: Skeletally mature patients with pelvic ring injury and unilateral zone 1 or 2 sacral fractures and without anteroposterior compression injuries. MAIN OUTCOME MEASUREMENTS: Injury plain anteroposterior, inlet, and outlet radiographs and computed tomography scans of the pelvis were evaluated for fracture displacement. RESULTS: Three hundred thirty-three patients with unilateral sacral fractures and a mean age of 41 years with a mean Injury Severity Score of 15 were included. Ninety-two percent sustained lateral compression injuries, and 63% of all fractures were in zone 1. Thirty-three percent of patients were treated operatively, including all without lateral compression patterns. Operative patients were more likely to have zone 2 fractures (54%) and to have posterior cortical displacement (29% vs. 6.2%), both with P < 0.001. Over 60% of all patients had no posterior displacement. Mean rotational displacements comparing the injured side versus the intact side were no different for patients treated operatively compared with those treated nonoperatively. CONCLUSIONS: Most unilateral sacral fractures are minimally or nondisplaced. Many patients with radiographically similar fractures were treated operatively and nonoperatively by different surgeons. This suggests an opportunity to develop consistent indications for treatment. LEVEL OF EVIDENCE: Prognostic Level II. See Instructions for Authors for a complete description of levels of evidence.

Treatment of Pediatric and Adolescent Pelvic Ring Injuries With Percutaneous Screw Placement.

BACKGROUND: Pediatric and adolescent pelvic ring injuries are frequently treated without surgery. In patients with unstable injuries to the pelvic ring, surgical stabilization aids in resuscitation, provides pain relief, and allows for mobilization. Percutaneous pelvic screw fixation is commonly performed in adult patients for unstable pelvic ring injuries, but a paucity of literature exists regarding their use in pediatric patients. The purpose of this study is to review the use, outcome, and management of percutaneous posterior pelvic screws in pediatric patients with unstable pelvic ring injuries. METHODS: A retrospective review of a prospectively collected orthopaedic trauma database was performed over a 7-year period at a regional level-1 trauma center. All patients between the ages of 7 and 17 who sustained an injury to the pelvic ring and were treated with percutaneous fixation of the posterior pelvic ring were identified. We evaluated the frequency of this technique in the described patient population, incidence of nerve injury, infection, loss of fixation, and need for hardware removal. RESULTS: A total of 238 pediatric patients who sustained a pelvic ring injury were initially identified; following application of study criteria, 67 (28.1%) patients were included in the study. Additional anterior ring fixation was performed in 33 (49.2%) patients. There were no iatrogenic nerve injuries, no infections, and surgical blood loss was <50 mL in all cases. Clinical and radiographic follow-up averaged 33 weeks. No loss of reduction was observed. Eight patients (13%) reported persistent low back pain at last follow-up. Elective hardware removal was performed in 3 patients. CONCLUSIONS: The majority of pediatric pelvic ring injuries can be treated without surgery. In the setting of instability, percutaneous pelvic screw fixation can be performed safely. A computed tomography scan is used to evaluate the available osseous pathways for screws and intraoperative fluoroscopy is used to safely perform this technique. Screw removal should be discussed in select patients. LEVEL OF EVIDENCE: Level IV.

Acetabular Fractures in the Senior Population- Epidemiology, Mortality and Treatments.

BACKGROUND: Management of acetabular fractures in the senior population can be one of the most challenging injuries to manage. Furthermore, treating surgeons have a paucity of information to guide the treatment in this patient population. THE PURPOSE OF THIS STUDY WAS TO DETERMINE: (1) demographic and epidemiologic data, (2) mortality rates for nonoperative compared to operative management at different time points, (3) common fracture configurations, and (4) fracture fixation strategies in senior patients treated with acetabular fractures. METHODS: Retrospective review of prospectively gathered data at a Level I trauma center over a five-year period. 1123 acetabular fractures were identified. 156 of them were for patients over the age of 65 (average age of 78). RESULTS: Falls and motor vehicle accidents accounted for the two most common mechanisms of injury. 82% of patients had significant medical comorbidities. 51 patients (33%) died within one year, in which 75% of them died within 90 days of their acetabular fracture. 84% of the deceased patients, i.e. from the group of 51 patients, had non-operative treatment. For patients treated with traction alone, there was a 79% one-year mortality and 50% mortality rate within 90 days. Within the entire cohort, 70% had either an associated both-column (ABC) or anterior column/posterior hemitransverse (AC/PHT) fracture pattern. Fifty-seven patients (36.5%) underwent open reduction and internal fixation using standard reduction techniques and surgical implants via two main surgical exposures of ilioinguinal (69%) and Kocher-Langenbeck (29%). CONCLUSION: Geriatric patients with acetabular fractures are uncommon accounting for only 14% of all acetabular fractures. Patients who undergo surgery show lower mortality rates. ABC and AC/PHT fracture patterns are the two most common fracture patterns. Routine fixation constructs and implants can be used to manage these challenging fractures. Most patients are unable to return to their homes and instead require skilled nursing facility during their convalescence.

Intra-operative multi-dimensional fluoroscopy of guidepin placement prior to iliosacral screw fixation for posterior pelvic ring injuries and sacroiliac dislocation: an early case series.

PURPOSE: Traditional fluoroscopic techniques during percutaneous fixation of the posterior pelvic ring at times cannot adequately visualize errant or malpositioned iliosacral screws. Intra-operative fluoroscopic techniques have been advanced using multi-dimensional fluoroscopy to generate computed tomography-like images. This provides the surgeon not only the ability to assess iliosacral screw placement, but also the opportunity to assess reduction. We present a case series of four patients in which the Ziehm RFD multi-dimensional fluoroscopy was used to assess reduction and guidepin placement prior to definitive iliosacral screw fixation. METHODS: Four patients at our university level 1 trauma center with posterior pelvic ring disruptions were treated with percutaneous iliosacral screw fixation. Traditional fluoroscopic techniques were used during guidepin placement. Multi-dimensional fluoroscopy was performed using the Ziehm RFD 3D to assess guidepin placement and reduction prior to definitive iliosacral screw fixation. RESULTS: Our case series highlights two patients in which multi-dimensional fluoroscopy was utilized to ensure safe placement of iliosacral screws. In one of these two patients, a change was made after reviewing the imaging as a guidepin was found to be intruded into bilateral S2 neural tunnels. We also present two patient examples in which multidimensional fluoroscopy was used to assess reduction achieved by less invasive methods, precluding the need for direct visualization using more extensive open approaches. CONCLUSIONS: This retrospective case series demonstrates the direct impact that the Ziehm RFD 3D technology provides in surgical management of patients with complex posterior pelvic ring injuries.

Early failure of symphysis pubis plating.

INTRODUCTION: Operative fixation of a disrupted symphysis pubis helps return alignment and stability to a traumatized pelvic ring. Implant loosening or failure has been demonstrated to commonly occur at some subacute point during the postoperative period. The purpose of this study is to report on a series of patients with traumatic pelvic ring disruptions to determine the incidence and common factors associated with early postoperative symphyseal plate failure before 7 weeks. MATERIALS AND METHODS: 126 patients retrospectively identified with unstable pelvic injuries treated with open reduction and plate fixation of the symphysis pubis and iliosacral screw fixation. Preoperative and postoperative radiographs, computed tomography (CT) images, and medical chart were reviewed to determine symphyseal displacement preoperatively and postoperatively, time until plate failure, patient symptoms and symphyseal displacement at failure, subsequent symphyseal displacement, incidence of additional surgery, and patient weight bearing compliance. RESULTS: 14 patients (11.1%) sustained premature postoperative fixation failure. 13 patients had anteroposterior compression (APC)-II injuries and 1 patient had an APC-III injury. Preoperative symphyseal displacement was 35.6 millimeters (mm) (20.8-52.9). Postoperative symphyseal space measurement was 6.3mm (4.7-9.3). Time until plate failure was 29days (5-47). Nine patients (64.2%) noted a pop surrounding the time of failure. Symphyseal space measurement at failure was 12.4mm (5.6-20.5). All patients demonstrated additional symphyseal displacement averaging 2.6mm (0.2-9.4). Two patients (14.2%) underwent revision. Four patients (28.5%) were non-compliant. CONCLUSION: Premature failure of symphysis pubis plating is not uncommon. In this series, further symphyseal displacement after plate failure was not substantial. The presence of acute symphyseal plate failure alone may not be an absolute indication for revision surgery. Making patient education a priority could lead to decreased postoperative non-compliance and potentially a decreased incidence of implant failure. Posterior pelvic ring fixation aides overall pelvic ring stability and may help minimize further displacement after early postoperative symphyseal plate failure. Further functional outcome and biomechanical studies surrounding early symphyseal plate failure are needed.

Variations in sacral morphology and implications for iliosacral screw fixation.

Posterior pelvic percutaneous fixation following either closed or open reduction is a popular procedure. Knowledge of the posterior pelvic anatomy, its variations, and related imaging is critical to performing reproducibly safe surgery. The dysmorphic sacrum has several key characteristics. The upper portion of the sacrum is relatively colinear with the iliac crests on the outlet radiographic view. Other characteristics include the presence of mammillary bodies (ie, underdeveloped transverse processes) at the sacral mid-alar area, anterior upper sacral foramina that are not circular, residual upper sacral disks, an acute alar slope oriented from cranial-posterior-central to caudal-anterior-lateral on the outlet and lateral views of the sacrum, a tongue-in-groove sacroiliac joint surface visualized on CT, and cortical indentation of the anterior ala on the inlet radiographic view. The surgeon must be knowledgeable about individual patient anatomy to ensure safe iliosacral screw placement.

Quantification of the upper and second sacral segment safe zones in normal and dysmorphic sacra.

OBJECTIVES: To quantify the obliquity and dimensions of the upper and second sacral segment iliosacral screw safe zones and to determine the differences between normal and dysmorphic sacral morphology. DESIGN: Retrospective cohort. SETTING: University Level I trauma center. PATIENTS/PARTICIPANTS: Fifty patients with pelvic computed tomography scans. INTERVENTION: All sacra were characterized as normal or dysmorphic based on plain pelvic radiographs and previously described criteria. Multiple computed tomography scan reconstructions were viewed and manipulated simultaneously with 6 degrees of freedom to allow for custom visualization in any plane. MAIN OUTCOME MEASUREMENTS: In each patient, a unique reconstruction plane was created perpendicular to the safe zone axis. The narrowest safe zone cross-sectional area was measured. Next, on simulated pelvic outlet and inlet views, safe zone obliquity and width were measured. Finally, the space available for a transverse screw was assessed. Measurements were performed for both upper and second sacral segment. Values for normal and dysmorphic safe zones were compared. RESULTS: Sacral dysmorphism was identified in 22 patients. In these sacra, the upper sacral segment safe zone cross-section was 36% smaller than in normal sacra (P < 0.001). No transverse screws could be placed, but accommodating for the caudal to cranial obliquity (30° versus 21° in normals, P < 0.001) and posterior to anterior obliquity (15% versus 4% in normals, P < 0.001) of the safe zone, an iliosacral screw at least 75 mm in length could be placed safely in 91% of patients. A transverse screw could be placed in 75% of normal sacra. In the second segment safe zone, the cross-sectional area was more than twice as large in dysmorphic sacra compared to normals (220 mm versus 109 mm, P < 0.001). The obliquity was not different on either the inlet or outlet views between groups. A transverse screw could be placed at this level in 95% of those with dysmorphic sacra and in only 50% of normal sacra. CONCLUSIONS: Sacral dysmorphism occurred in 44% of patients in this consecutive series. Many anatomic differences were consistently found between the two morphologies with clinical relevance to iliosacral screw placement. Specifically, the dysmorphic upper sacral segment safe zone is significantly smaller and more obliquely oriented but is still large enough to accommodate an iliosacral screw in nearly all patients. The second sacral segment safe zone is approximately transversely oriented in both sacral types but is more than twice as large in dysmorphic sacra. This segment may be a primary fixation opportunity in patients with sacral dysmorphism.