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Investigation of bone quality of the first and second sacral segments amongst trauma patients: concerns about iliosacral screw fixation.

Salazar D, Lannon S, Pasternak O, Schiff A, Lomasney L, Mitchell E, Stover M - J Orthop Traumatol (2015)

Bottom Line: A statically significant difference in bone quality was found when comparing the first and second sacral segment (p = 0.0001).Age, gender, or smoking status did not independently affect bone quality.In relatively young, otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment.

View Article: PubMed Central - PubMed

Affiliation: The Department of Orthopaedic Surgery and Rehabilitation, Loyola University Health System, 2160 South First Avenue, Maywood, IL, 60153, USA. dsalazar@post.com.

ABSTRACT

Background: Iliosacral screw fixation has become a common method for surgical stabilization of acute disruptions of the pelvic ring. Placement of iliosacral screws into the first sacral (S1) body is the preferred method of fixation, but size limitations and sacral dysmorphism may preclude S1 fixation. In these clinical situations, fixation into the second sacral (S2) body has been recommended. The objective of this study was to evaluate the bone quality of the S1 compared to S2 in the described "safe zone" of iliosacral screw fixation in trauma patients.

Materials and methods: The pelvic computed tomography scans of 25 consecutive trauma patients, ages 18-49, at a level 1 trauma center were prospectively analyzed. Hounsfield units, a standardized computed tomography attenuation coefficient, was utilized to measure regional cancellous bone mineral density of the S1 and S2. No change in the clinical protocol or treatment occurred as a consequence of inclusion in this study.

Results: A statically significant difference in bone quality was found when comparing the first and second sacral segment (p = 0.0001). Age, gender, or smoking status did not independently affect bone quality.

Conclusion: In relatively young, otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment. This study highlights the need for future biomechanical studies to investigate whether this difference is clinically relevant. Due to the relative osteopenia in the second sacral segment, which may impact the quality of fixation, we feel this technique should be used with caution.

Level of evidence: III.

No MeSH data available.


Related in: MedlinePlus

Axial CT sections demonstrating the technique for ROI placement as described in the methods section. a Horizontal reference lines at S1 (blue). b Vertical midline reference line at S1 (green dashed). c Vertical reference line tangential to the medial border of the sacral foramina at S1 (red dashed). d Placement of ROIs at 25 and 75 % of the vertical midline distance and 50 % of the vertical lateral distance at S1 (white). e–h The same technique at S2 (color figure online)
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Fig2: Axial CT sections demonstrating the technique for ROI placement as described in the methods section. a Horizontal reference lines at S1 (blue). b Vertical midline reference line at S1 (green dashed). c Vertical reference line tangential to the medial border of the sacral foramina at S1 (red dashed). d Placement of ROIs at 25 and 75 % of the vertical midline distance and 50 % of the vertical lateral distance at S1 (white). e–h The same technique at S2 (color figure online)

Mentions: Images were viewed using the bone algorithm default windows on picture archiving and communication system (PACS) viewing software. Using axial images, the mid-body location of S1 and S2 was determined for each subject and confirmed by cross-referencing position with coronal and sagittal reconstructions (Fig. 1). To standardize measurement while accounting for normal anatomic variation and optimal iliosacral screw trajectory as described in the literature, four standardized circular voxel regions of interests (ROIs) were drawn at determined mid-body S1 and S2 levels of each subject (Fig. 2). These standardized circular ROIs were drawn with areas ranging from 23.2 to 26.2 mm2. This range was chosen after pilot testing to maximize the area of trabecular bone tested in line with the potential screw trajectory, while limiting overlap of adjacent ROIs. When placing ROIs, one horizontal reference line was drawn tangential to the most anterior points of both sacral foramina (Fig. 2a, e). One transecting vertical reference line was then drawn from the tip of the spinous process through the midpoint of the anterior cortex of the vertebral body (Fig. 2b, f). ROIs were then drawn with their center corresponding to 25 and 75 % of the distance from the anterior cortex to the horizontal reference line. A vertical reference line was then drawn tangential to the most medial point of the sacral foramina (Fig. 2c, g). An ROI was then drawn with the center of the ROI at 50 % of the distance between the anterior cortex and horizontal reference line drawn previously. This method was then repeated on the adjacent side. Figure 2d and h demonstrates the placement of ROIs. Hounsfield unit (HU) density values for each ROI were then collected and averaged to yield the mean value for each segment.Fig. 1


Investigation of bone quality of the first and second sacral segments amongst trauma patients: concerns about iliosacral screw fixation.

Salazar D, Lannon S, Pasternak O, Schiff A, Lomasney L, Mitchell E, Stover M - J Orthop Traumatol (2015)

Axial CT sections demonstrating the technique for ROI placement as described in the methods section. a Horizontal reference lines at S1 (blue). b Vertical midline reference line at S1 (green dashed). c Vertical reference line tangential to the medial border of the sacral foramina at S1 (red dashed). d Placement of ROIs at 25 and 75 % of the vertical midline distance and 50 % of the vertical lateral distance at S1 (white). e–h The same technique at S2 (color figure online)
© Copyright Policy - OpenAccess
Related In: Results  -  Collection

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Fig2: Axial CT sections demonstrating the technique for ROI placement as described in the methods section. a Horizontal reference lines at S1 (blue). b Vertical midline reference line at S1 (green dashed). c Vertical reference line tangential to the medial border of the sacral foramina at S1 (red dashed). d Placement of ROIs at 25 and 75 % of the vertical midline distance and 50 % of the vertical lateral distance at S1 (white). e–h The same technique at S2 (color figure online)
Mentions: Images were viewed using the bone algorithm default windows on picture archiving and communication system (PACS) viewing software. Using axial images, the mid-body location of S1 and S2 was determined for each subject and confirmed by cross-referencing position with coronal and sagittal reconstructions (Fig. 1). To standardize measurement while accounting for normal anatomic variation and optimal iliosacral screw trajectory as described in the literature, four standardized circular voxel regions of interests (ROIs) were drawn at determined mid-body S1 and S2 levels of each subject (Fig. 2). These standardized circular ROIs were drawn with areas ranging from 23.2 to 26.2 mm2. This range was chosen after pilot testing to maximize the area of trabecular bone tested in line with the potential screw trajectory, while limiting overlap of adjacent ROIs. When placing ROIs, one horizontal reference line was drawn tangential to the most anterior points of both sacral foramina (Fig. 2a, e). One transecting vertical reference line was then drawn from the tip of the spinous process through the midpoint of the anterior cortex of the vertebral body (Fig. 2b, f). ROIs were then drawn with their center corresponding to 25 and 75 % of the distance from the anterior cortex to the horizontal reference line. A vertical reference line was then drawn tangential to the most medial point of the sacral foramina (Fig. 2c, g). An ROI was then drawn with the center of the ROI at 50 % of the distance between the anterior cortex and horizontal reference line drawn previously. This method was then repeated on the adjacent side. Figure 2d and h demonstrates the placement of ROIs. Hounsfield unit (HU) density values for each ROI were then collected and averaged to yield the mean value for each segment.Fig. 1

Bottom Line: A statically significant difference in bone quality was found when comparing the first and second sacral segment (p = 0.0001).Age, gender, or smoking status did not independently affect bone quality.In relatively young, otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment.

View Article: PubMed Central - PubMed

Affiliation: The Department of Orthopaedic Surgery and Rehabilitation, Loyola University Health System, 2160 South First Avenue, Maywood, IL, 60153, USA. dsalazar@post.com.

ABSTRACT

Background: Iliosacral screw fixation has become a common method for surgical stabilization of acute disruptions of the pelvic ring. Placement of iliosacral screws into the first sacral (S1) body is the preferred method of fixation, but size limitations and sacral dysmorphism may preclude S1 fixation. In these clinical situations, fixation into the second sacral (S2) body has been recommended. The objective of this study was to evaluate the bone quality of the S1 compared to S2 in the described "safe zone" of iliosacral screw fixation in trauma patients.

Materials and methods: The pelvic computed tomography scans of 25 consecutive trauma patients, ages 18-49, at a level 1 trauma center were prospectively analyzed. Hounsfield units, a standardized computed tomography attenuation coefficient, was utilized to measure regional cancellous bone mineral density of the S1 and S2. No change in the clinical protocol or treatment occurred as a consequence of inclusion in this study.

Results: A statically significant difference in bone quality was found when comparing the first and second sacral segment (p = 0.0001). Age, gender, or smoking status did not independently affect bone quality.

Conclusion: In relatively young, otherwise healthy trauma patients there is a statistically significant difference in the bone density of the first sacral segment compared to the second sacral segment. This study highlights the need for future biomechanical studies to investigate whether this difference is clinically relevant. Due to the relative osteopenia in the second sacral segment, which may impact the quality of fixation, we feel this technique should be used with caution.

Level of evidence: III.

No MeSH data available.


Related in: MedlinePlus