CT-based evaluation of volumetric bone density in fragility fractures of the pelvis-a matched case-control analysis

Using advanced imaging to measure bone density, compression fracture risk, and risk for construct failure after spine surgery

Low bone mineral density (BMD) can predispose to vertebral body compression fractures and postoperative instrumentation failure. DEXA is considered the gold standard for measurement of BMD, however it is not obtained for all spine surgery patients preoperatively. There is a growing body of evidence suggesting that more routinely acquired spine imaging studies such as computed tomography (CT) and magnetic resonance imaging (MRI) can be opportunistically used to measure BMD. Here we review available studies that assess the validity of opportunistic screening with CT-derived Hounsfield Units (HU) and MRI-derived vertebral vone quality (VBQ) to measure BMD of the spine as well the utility of these measures in predicting postoperative outcomes. Additionally, we provide screening thresholds based on HU and VBQ for prediction of osteopenia/ osteoporosis and postoperative outcomes such as cage subsidence, screw loosening, proximal junctional kyphosis, and implant failure.

Comparison of the zonal distribution of calcium salt density and fat marrow in bone-healthy and osteoporotic sacra: an image data analysis using quantitative computed tomography and magnetic resonance imaging

PURPOSE

Pathogenesis of sacral fragility fractures is not fully understood. This study investigates zonal distribution of calcium salt and fat marrow in intact bone-healthy and osteoporotic pelvis. In addition, in unilateral sacral fractures, the fracture side was compared with the intact side.

METHODS

CT and MRI images of 37 pelves were analyzed. Zonal calcium salt distribution by Hounsfield units (HU) was recorded for each CT dataset. Fat marrow content was measured in MRI mDixon-Quant sequence. The cohort was divided: intact pelves with (PEO, HU < 100, n = 8) and without osteoporosis (PE, HU ≥ 100, n = 14) based on the mean HU value in LWK5. A third group consisted of patients with osteoporosis and unilateral fractures (PEOFx, n = 10).

CONCLUSION

The results suggest that in PEO sacral alae experience disproportionate skeletal rarefaction. This concerns the sacral ala at the S1 level (- 25 ± 55), whereby the calcium salt content is so low that it corresponds to the S3 level of healthy bone (- 20 ± 21 HU). This explains the occurrence of transalar fractures in the load-transmitting zone S1. In PEOFx, the calcium salt density was higher and the fat content was lower on the fractured side than on the intact side, indicating bony compacting due to lateral compression and fat displacement due to hematoma in the accident mechanism. This study makes an important contribution to the understanding of the development of sacral fragility fractures. Furthermore, impaction of the cancellous bone within the fracture can be demonstrated.

Noninvasive Detection of Arytenoid Cartilage Calcification Using Computed Tomography and Prediction of Prognosis in Laryngeal Contact Granuloma

OBJECTIVE

Laryngeal contact granuloma (LCG) is a relatively uncommon disease with chronic inflammatory stimulation, and long-term reflux irritation is a vital factor for arytenoid cartilage calcification. Our investigation compared the severity of ipsilateral arytenoid cartilage calcification with the frequency of recurrence of LCG after surgical treatment.

METHODS

A retrospective chart review of prospectively gathered data over five years from 327 patients, including 153 subjects without laryngeal lesions, were age- and sex-matched normal controls, 103 patients with various other vocal cord lesions were in the laryngeal lesion group and 71 LCG patients met the diagnostic criteria pathologically. All subjects underwent laryngeal high-resolution computed tomography (HRCT) prior to therapeutic interventions. The computed tomography (CT) value and arytenoid cartilage calcification were obtained using image data before surgery, and their clinical significance was further analyzed.

RESULTS

Seventy-one patients with LCG, including sixty-two males, were enrolled in the study. Among these cases, there were 67 patients with unilateral vocal cord lesions. Of the 103 eligible patients in the laryngeal lesion group, 87 had unilateral lesions, which including eighty-seven men. Of the 153 average subjects, 105 were male. The rate of arytenoid cartilage calcification in the LCG group was dramatically higher in the lesion side than in the laryngeal lesions and normal group (P < 0.01). Furthermore, the CT value (P < 0.01) and range of calcification (P < 0.01) were significantly higher in patients with LCG than in those with laryngeal lesions. Importantly, patients with high CT values and the calcification range of lesions in the arytenoid cartilage displayed a greater lesion size and recurrence rate than patients with low CT values and lesion areas (P < 0.01).

CONCLUSION

Our results suggest that most patients with LCG present with calcification of the arytenoid cartilage. The more severe the calcification in the arytenoid cartilage, the greater the risk of granuloma size and recurrence in LCG after surgical treatment. CT and bone density testing of the arytenoid cartilage may be an essential method to evaluate the prognosis of LCG.

Is the conservative treatment of sacral insufficiency fractures still up to date? Retrospective clinical observational study in 46 patients

BACKGROUND

According to current forecasts, our society will grow older and older, so that the proportion of 6% of the German population from 2017 who were 80 years or older will increase further. The frequency of falls in this patient population lead to a further increase of sacral insufficiency fractures.

HYPOTHESIS

The aim of this study is to evaluate the multimodal interdisciplinary conservative therapy regime for sacral insufficiency fractures in geriatric patients, especially on the basis of mobility and the need for assistance.

PATIENTS AND METHODS

A cohort of patients, who were treated as inpatients at the Waldkrankenhaus St. Marien in Erlangen with ICD-10 for sacral fractures S32.1 as the main diagnosis, was retrospectively examined. Only newly diagnosed sacral insufficiency fractures were taken into account. Patients were divided into groups based on the factors hospital stay, fracture location on the sacrum, and location of concomitant pelvic ring injury. The Barthel Index, the Tinetti's Mobility Test and the Timed Up&Go Test were recorded.

RESULTS

46 patients met the inclusion criteria. Using the conservative therapy, improvements were achieved in all patients in terms of need for care, mobility without aids and risk of falling, also patients with an anterior and posterior pelvic ring fracture. Regard a score improvement in the Barthel Index and Tinetti Mobility Test, patients with bilateral sacral insufficiency fracture (n=17, 37.0%) did not differ significantly from patients with unilateral sacral insufficiency fracture (n=22, 47.8%).

CONCLUSION

In geriatric patients, decisions about therapy should always be made on an individual and interdisciplinary basis. The conservative therapy regimen continues to play an important role in this. The collected tests-consisting of Barthel Index, Tinetti Mobility Test and Timed Up&Go Test-are well suited for further reproducible, objective studies with a larger patient collective.

LEVEL OF EVIDENCE

IV.

Treatment and Outcome of Osteoporotic Thoracolumbar Vertebral Fractures With Anterior or Posterior Tension Band Failure (OF 5): Short-Term Results From the Prospective EOFTT Multicenter Study

STUDY DESIGN

Subgroup analysis of a multicenter prospective cohort study.

OBJECTIVE

To analyse surgical strategies applied to osteoporotic thoracolumbar osteoporotic fracture (OF) 5 injuries with anterior or posterior tension band failure and to assess related complications and clinical outcome.

METHODS

A multicenter prospective cohort study (EOFTT) was conducted at 17 spine centers including 518 consecutive patients who were treated for an osteoporotic vertebral fracture (OVF). For the present study, only patients with OF 5 fractures were analysed. Outcome parameters were complications, Visual Analogue Scale (VAS), Oswestry Disability Questionnaire (ODI), Timed Up & Go test (TUG), EQ-5D 5L, and Barthel Index.

RESULTS

In total, 19 patients (78 ± 7 years, 13 female) were analysed. Operative treatment consisted of long-segment posterior instrumentation in 9 cases and short-segment posterior instrumentation in 10 cases. Pedicle screws were augmented in 68 %, augmentation of the fractured vertebra was performed in 42%, and additional anterior reconstruction was done in 21 %. Two patients (11 %) received short-segment posterior instrumentation without either anterior reconstruction or cement-augmentation of the fractured vertebra. No surgical or major complications occurred, but general postoperative complications were observed in 45%. At a follow-up of mean 20 ± 10 weeks (range, 12 to 48 weeks), patients showed significant improvements in all functional outcome parameters.

CONCLUSIONS

In this analysis of patients with type OF 5 fractures, surgical stabilization was the treatment of choice and lead to significant short-term improvement in terms of functional outcome and quality of life despite a high general complication rate.

A Case of Fragility Fracture of the Pelvis Initially Diagnosed as Osteoarthritis of the Hip

We present the case of a 58-year-old woman who presented with anterior groin pain, initially diagnosed with hip osteoarthritis (OA), scheduled for total hip arthroplasty, and subsequently diagnosed with an occult fragility fracture of the pelvis (FFP) by preoperative computed tomography (CT) examination. We diagnosed the patient with pre-existing hip OA and a bilateral sacrum and left pubic tubercle fracture that exacerbated the groin pain. We operated on the FFP followed by simultaneous bilateral total hip arthroplasty. Given the high prevalence of hip OA and the increasing incidence of FFP, comorbidity of these 2 entities should be ruled out. Even if hip OA is apparent, plain radiographs are insufficient to rule out FFP, necessitating a thorough clinical examination, followed by a CT examination if an FFP is suspected.

Distribution of hounsfield unit values in the pelvic bones: a comparison between young men and women with traumatic fractures and older men and women with fragility fractures: a retrospective cohort study

Background

The fixation strength of bone screws depends on bone mineral density (BMD), so it is important to evaluate bone strength at fracture sites. Few studies have investigated BMD in the pelvis. The aims of this study were to measure the regional Hounsfield unit (HU) values in the cancellous bone of the acetabulum and pelvic ring and to compare these values between young and older patients.

Methods

This study enrolled young patients with high-energy trauma (aged 20–44 years; young group) and older patients with low-energy trauma (aged 65–89 years; older group). Patients without pelvic computed tomography (CT) scans, those with pelvic bone implants, and those who died were excluded. The HU values on the contralateral (non-fractured) side of the pelvis were measured on CT scans. The CT data were divided into 7 areas: the pubic bone, the anterior and posterior walls and roof of the acetabulum, the ischial tuberosity, the body of the ilium, and the third lumbar vertebra. The HU values in each area were compared between the young and older groups.

Results

Sixty-one young patients and 154 older patients were included in the study. The highest HU value was in the roof of the acetabulum regardless of age and sex. HU values were significantly higher in the ischial tuberosity and body of the ilium and lower in the pubic bone and anterior wall. The HU values in all pelvic areas were significantly lower in the older group than in the young group, especially in the anterior area.

Conclusions

HU values in the 6 pelvic areas were not uniform and were strongly related to load distribution. The HU distribution and age-related differences could explain the characteristic causes and patterns of acetabular fractures in the older and may help in surgical treatment.

The effect of age and sex on pelvic bone density measured opportunistically in clinical CT scans

Unstable pelvic ring fractures are severe and complex injuries, and surgical fixation is challenging and can be complicated by early failure due in part to difficulties with securely fixing screws in low-density bone. There is limited information in the literature about how the density distribution across the pelvic bones changes with age and sex. In this study, we used 60 sets of calibrated bone density measurements obtained opportunistically from clinical computed tomography scans of the pelvis. Three-dimensional models of the innominate bone were produced and the effects of age and sex on cortical bone density modeled. Overall trends and regions where these factors had a significant effect were identified, and the results visualized. Across the entire innominate bone, the mean loss of density was found to be 1.6 mg/cc per year, with several specific areas (pubic body, iliac fossa, posterior ilium, and anterior inferior iliac spine for example) showing significant rates of loss up to three times greater than the rest of the bone. Areas significantly affected by sex included the posterior pubic root, anterior aspect of the pubic body, and iliac crest. Despite overall trends of attenuation, there remains significant variability between individuals. This supports the need to further explore subject-specific planning tools for pelvic fracture repair. Statement of clinical significance: Bone density changes across the innominate bone due to age and sex tend to vary between individuals, although consistent effects were seen at specific regions. This information may help in surgical planning of unstable fracture repairs.

Posterior pelvic ring bone density with implications for percutaneous screw fixation

BACKGROUND

Although the second (S2) and third (S3) sacral segments have been established as potential osseous fixation pathways for screw fixation, the S2 body has been demonstrated to have inferior bone density when compared to the body of the first (S1) sacral segment. Caution regarding the use of iliosacral screws at this level has been advised as a result. As transiliac-transsacral screws traverse the lateral cortices of the posterior pelvis, they may be relying on bone with superior density for purchase, which could obviate this concern. The objective of this study was to compare the bone density of the posterior ilium and sacroiliac joint to that of the sacral body at the first (S1), second (S2), and third (S3) sacral levels.

MATERIALS AND METHODS

A retrospective case series was performed, reviewing the CT scans of 100 patients without prior pelvic trauma. Each CT was confirmed to have available osseous fixation pathways at the first (S1), second (S2), and third (S3) sacral segments. The bone density of the posterior ilium/sacroiliac joint (PISJ) and sacral body (SB) was measured using the embedded standardized Hounsfield units (HU) tool at each sacral level.

RESULTS

The average S2 PISJ bone density (320.1) was significantly higher than the S1 (286.5) and S3 (278.9) PISJ (p < 0.0001) and S1 and S3 PISJ was not statistically different. The S1 sacral body bone density (231.1) was significantly higher than the S2 (182.1) and S3 (126.8) bone density (p < 0.0001). The PISJ bone density is greater than the sacral body at every sacral level (p < 0.0001).

CONCLUSION

The S2 PISJ bone density is significantly greater than S1. The S1, S2, and S3 PISJ bone density is greater than the sacral body at all sacral levels, and the S1 body has higher bone density than the S2 and S3 bodies. These differences in bone density may have implications for the stability of posterior pelvic ring fixation constructs with regard to screw purchase.

LEVEL OF EVIDENCE

Level III-Case cohort series.

Use of Hounsfield units of S1 body to diagnose osteoporosis in patients with lumbar degenerative diseases

OBJECTIVEThe aim of this study was to evaluate the use of Hounsfield unit (HU) values of the S1 body to diagnose osteoporosis in patients with lumbar degenerative diseases.METHODSThe records of 316 patients of ages ≥ 50 years and requiring surgery for lumbar degenerative diseases were reviewed. The bone mineral density (BMD) of the S1 body and L1 was measured in HU with preoperative lumbar CT. Circular regions of interest (ROIs) were placed on midaxial and midsagittal images of the S1 body. Dual-energy x-ray absorptiometry (DXA) and the criterion of L1 HU ≤ 110 HU were used to diagnose osteoporosis. The area under the receiver operating characteristic curve (AUC) was calculated to assess the use of HUs of the S1 body to diagnose osteoporosis.RESULTSThe interobserver and intraobserver reliability of measuring HU of the S1 body was excellent with intraclass correlation coefficients over 0.8 (p < 0.001). The correlation between HUs of the S1 body and average T-score of L1-4 was significant with Pearson correlation coefficients ≥ 0.60 (p < 0.001). The AUCs for using HUs of the S1 body to diagnose osteoporosis were 0.86 and 0.88 for axial HU and sagittal HU, respectively (p < 0.001). The HU thresholds with balanced sensitivity and specificity for diagnosing osteoporosis were 202 HU for axial HU (sensitivity: 76%; specificity: 76%) and 185 HU for sagittal HU (sensitivity: 80%; specificity: 80%).CONCLUSIONSBoth sagittal and axial HUs of the S1 body are useful tools for assessing BMD and diagnosing osteoporosis. Measuring HUs of the S1 body preoperatively from lumbar CT may help with surgical planning for patients with lumbar degenerative diseases.

The impact of degenerative disc disease on regional volumetric bone mineral density (vBMD) measured by quantitative computed tomography

BACKGROUND CONTEXT

It has been reported that degenerative disc disease (DDD) is associated with higher spinal bone mineral density (BMD) based on previous studies that used dual X-ray absorptiometry (DXA). However, DDD is often associated with proliferative bone changes and can lead to an overestimation of BMD measured with DXA. Trabecular volumetric BMD (vBMD) in the vertebral body measured with quantitative computed tomography (QCT) is less affected by those changes and can be a favorable alternative to DXA for patients with degenerative spinal changes.

PURPOSE

The purpose of this study is to investigate the effect of DDD on regional trabecular vBMDs in the vertebral body measured by QCT.

STUDY DESIGN/SETTING

Cross-sectional observational study at a single academic institution.

PATIENTS SAMPLE

Consecutive patients undergoing posterior lumbar spinal fusion between 2014 and 2017 who had a routine preoperative CT scan and magnetic resonance imaging (MRI) within a 90-day interval.

OUTCOME MEASURES

Regional trabecular vBMDs in the vertebral body by QCT.

METHODS

QCT measurements were conducted in L1-S1 vertebral trabecular bone. Any apparent sclerotic lesions that might affect vBMD values were excluded from the region of interest. The vBMDs of each level were defined as the average vBMD of the upper and lower vertebrae. To evaluate DDD, Pfirrmann grade, Modic grade, total end plate score, and vacuum phenomenon were documented. Univariate regression analysis and multivariate analyses with a linear mixed model adjusted with individual variability of segmental vBMDs were conducted with vBMD as the response variable.

RESULTS

Of 143 patients and 715 disc levels, 125 patients and 596 discs met our inclusion criteria. Mean vBMD (±standard deviation [SD]) of all levels was 119.0±39.6 mg/cm³. After adjusting for all covariates, Pfirrmann grade was not an independent contributor to vBMD, but the presence of any Modic change (type 1, β=6.8, p≤.001; type 2, β=6.7, p<.001; type 3, β=43.6, p<.001), high TEPS (score 10-12, β=14.2, p<.001), or vacuum phenomenon (β=9.0, p<.001) was shown to be independent contributors to vBMD.

CONCLUSIONS

Our results showed that the presence of certain end plate lesions (Modic changes and high TEPS) on MRI was significantly associated with increased regional QCT-vBMDs in the vertebral body, but no significant association was observed with disc nucleus pathology, unless it was associated with a vacuum phenomenon. When end plate lesions with Modic changes and high TEPS are present at the measuring level, care must be taken to interpret vBMD values, which might be overestimations even if the trabecular area appears normal.

Assessment of bone quality at the lumbar and sacral spine using CT scans: a retrospective feasibility study in 50 comparing CT and DXA data

PURPOSE

Computed tomography (CT) is a standard diagnostic tool for preoperative screening for many indications in spinal and pelvic surgery. The gold standard for diagnosing osteoporosis is standard dual-energy X-ray absorptiometry (DXA). The aim of the present study was to compare the accuracy of Hounsfield unit (HU) measurements not only at the lower lumbar, but also at the sacral spine using standard CT scans.

PATIENTS AND METHODS

Main inclusion criterion for this retrospective analysis in 50 patients was the availability of both a CT scan of the lumbar and sacral spines and a DXA scan. HUs were measured in intact vertebral bodies L4, L5 and S1. Results of the HU in CT scan were compared to the T-score and bone mineral density in DXA. A group with normal bone density (T-score higher - 1, n = 26) was compared with a group with impaired bone density (T-score lower - 1, n = 24).

RESULTS

A multivariant binary logistic regression analysis showed significant results for HU measurement in L4 (p = 0.009), L5 (p = 0.005) and S1 (p = 0.046) with respect to differentiation between normal and impaired bone quality. Cutoffs between normal and impaired bone density values for trabecular region of interest attenuation for L4, L5 and S1 are presented. In L4 100% sensitivity to detect normal bone was reached when HU was higher than 161, HU higher than 157 in L5 and HU higher than 207 in S1.

CONCLUSIONS

HU measurements in CT scans have proven to be a feasible tool to additionally assess bone quality at the lumbar and sacral spine with good sensitivity, when compared with the gold standard DXA.

LEVEL OF EVIDENCE

III. These slides can be retrieved under Electronic Supplementary Material.

[Hounsfield units as a measure of bone density-applications in spine surgery]

Despite today's good diagnostic and therapeutic options for osteoporosis, the number of unidentified cases is very high and therapy is therefore usually inadequate. Frequently, the diagnosis of osteoporosis is made only after the occurrence of a fracture. The reason for this, apart from the costs incurred as well as the additional radiation exposure of the diagnostics, is certainly the limited availability of dual energy X‑ray absorptiometry (DEXA) as well as quantitative computed tomography (q-CT). In search of an alternative technique, Hounsfield units (HU) of the clinical CT examination proved to be ground-breaking: the results of previous investigations demonstrated a reliable correlation between the T values of the DEXA measurement and the HU of the same vertebral body. Due to the widespread use of clinical CT scans of the thorax and the abdomen for a variety of indications, it is expected that the number of unidentified cases of osteoporosis can be significantly reduced-without additional costs and radiation exposure associated with osteoporosis screening. In addition to osteoporosis diagnostics, the calculated HU may also provide better preoperative planning as well as predicting the further course of the disease. Thus, the risk for vertebral body fractures, screw loosening and cage sintering after ventral fusion operations can be sufficiently predicted. In this way, preoperative modifications to the surgical procedure can be made to reduce the risk of implant failure.

Bone loss and biomechanical reduction of appendicular and axial bones under ketogenic diet in rats

A ketogenic diet (KD) is composed of low-carbohydrate, high-fat and adequate levels of protein. It has been used for decades as a method to treat pediatric refractory epilepsy. However, recently, its side effects on the bones have received increasing attention. In order to comprehensively evaluate the effect of KD on the microstructures and mechanical properties of the skeleton, 14 male Sprague-Dawley rats were equally divided into two groups and fed with a KD (ratio of fat to carbohydrate and protein, 3:1) or a standard diet for 12 weeks. Body weight, as well as blood ketone and glucose levels, were monitored during the experiment. Bone morphometric analyses via micro-computerized tomography were performed on cortical and trabecular bone at the middle L4 vertebral body, the proximal humerus and tibia. The compressive stiffness and strength of scanned skeletal areas were calculated using micro-finite element analysis. The KD led to higher ketone levels and lower glucose levels, with reduced body weight and total bone mineral density (TBMD). After 12 weeks, the diet reduced the bone volume fraction, the trabecular number of cancellous bone, cortical thickness, total cross-sectional area inside the periosteal envelope and the bone area of cortical bone in the tibia and humerus, while increasing trabecular separation. However, KD may not affect the L4 vertebral body. The serum calcium or phosphate concentrations in the blood remained unchanged. In addition, bone stiffness and strength were clearly decreased by the KD, and significantly correlated with the BMD and bone area at all scanned sites. In conclusion, KD led to significant bone loss and reduced biomechanical function in appendicular bones, with a lesser impact on axial bones.

Single-level vertebral kyphoplasty is not associated with an increased risk of symptomatic secondary adjacent osteoporotic vertebral compression fractures: a matched case-control analysis

This matched case-control study compared the rate of symptomatic adjacent-level vertebral compression fractures (VCF) within 1 year in patients operatively treated with kyphoplasty to a control group of non-operatively treated VCFs. The adjacent-level fracture rate did not show a significant difference between groups.

PURPOSE

To compare the rate of new symptomatic adjacent-level fractures within 1 year after an isolated osteoporotic vertebral compression fracture (VCF) treated by either kyphoplasty or non-operative treatment.

METHODS

Patients aged ≥ 50 years with an isolated, fresh, and symptomatic osteoporotic VCF who were treated by kyphoplasty were compared to patients of similar age, gender, vertebral segment, and bone mineral density who were treated non-operatively (n = 98). A matched case-control analysis was conducted by retrospective chart review, and the rate of new adjacent-level symptomatic vertebral fractures, defined as occurring within two segments of the index fracture, within the first year was determined.

RESULTS

Ninety-eight patients (66 female, aged 73.5, SD 9.7 years) were analyzed in this matched case-control study. The adjacent fracture rate within 1 year was not different between the kyphoplasty group and the non-operative group (20.4 vs 18.4%; McNemar, p = 1.0). The time to a new adjacent fracture after the index fracture was significantly shorter in the kyphoplasty (7, SD 8 weeks) versus non-operative group (22, SD 13 weeks).

CONCLUSIONS

Patients with osteoporotic VCFs treated with kyphoplasty did not show an increased rate of additional symptomatic adjacent-level VCFs when compared to a non-operative control group matched for age, gender, fracture level, and bone mineral density.

LEVEL OF EVIDENCE

Level III.

Fragility fractures of the sacrum occur in elderly patients with severe loss of sacral bone mass

INTRODUCTION

Patients suffering from osteoporosis-associated fragility fractures of the sacrum (FFS; also termed sacral insufficiency fractures) are increasingly observed. They have typical fracture patterns with fracture lines located in the sacral ala. When treating these patients operatively, iliosacral screw loosening is not uncommon. We aimed to study the sacral bone mass in patients presenting with a FFS using 3D statistical models.

MATERIALS AND METHODS

3D models of averaged Hounsfield units (HU) were generated based on CT scans from 13 patients with a unilateral FFS (mean age 79.6 years; 11 females, 2 males). The control group without fractures consisted of 28 males and 32 females (mean age of 68.3 years). A virtual bone probe along the trans-sacral corridors S1 and S2 was taken.

RESULTS

The bone mass distribution in the fractured sacra was similar to the control group, however, with overall lower HU. Large zones of negative HU were located in the sacral ala. In the fractured sacra, the HU in the sacral ala was significantly lower on the non-injured side when comparing to the fractured side (p < 0.001) as well as compared to the non-fractured group (p < 0.001). Low bone mass was observed in sacral body S1 (40 HU) and S2 (20 HU).

CONCLUSIONS

The extensive area of negative HU may explain the fracture location in the sacral ala. The low HU in the sacral bodies advocates the use of trans-sacral implants or augmented iliosacral screws to enhance the strength of fracture fixation. The increased HU in the fractured ala could be explained by fracture-asssociated hemorrhage and can be used as a diagnostic tool.