Chest Wall Injury Society: Rib Fractures Definitions Consensus Survey – Round 3
Defining Sectors Around the Chest wall - Proposals For Sector Boundaries
Axillary Lines
In Round 2, the use of the anterior and posterior axillary lines was the most popular choice (75% of votes) for the boundaries between of the sectors. We have identified problems with the use of axillary lines as the borders between the sectors. • There is no agreed definition for the axillary lines • It is not easy to identify axillary lines on CT scans • Not all definitions of the axillary lines would give easily reproducible sectors • Not all definitions of the axillary lines would give evenly spaced sectors. A Definition for Axillary Lines • Anterior Axillary Line: Coronal line marked by the anterior axillary fold: it runs down from the point midway between the middle of the clavicle and lateral end of the clavicle
• Posterior Axillary Line: Coronal line marked by the posterior axillary fold Anterior Axillary Line Posterior Axillary Line Axillary Lines
• BUT: – The muscle markings do not run in vertical lines – The muscle markings may be difficult to see on CT scans, particularly at lower levels of the chest • A reproducible definition is required… Anterior Axillary Line Posterior Axillary Line Angles At Which Anatomical Features Lie
• The table above displays how the angles of different anatomical landmarks vary between patients on CT scans. • We have measured angles from the mid-thoracic point to the structure of interest, from the anterior sagittal midline in 96 patients • e.g. the mean angle of the scapula tip was 117o (SD 13.29, range 97-143)
Please consider carefully the advantages and disadvantages of the four proposals, given on the following slides
Note: the costochondral and paravertebral sectors are the same in each proposal: • Costochondral sector is medial to the costochondral junction of each rib • Paravertebral sector is medial to the costo-transverse joint of each rib Proposals
1. Vertical Lines 2. Muscle Borders 3. Angles from the mid-thoracic point 4. Equal Size Sectors
Each will be considered in turn, with explanatory diagrams Proposal 1: Vertical Lines
• Anterior / Lateral Sector boundary: – vertical line from the intersection of the posterior border of Pectoralis Major and the 2nd rib
• Lateral / Posterior Sector boundary: – Vertical line through the tip of the scapula
The following diagrams will provide full explanation Proposal 1: Vertical Lines The Border between the Anterior and Lateral Sectors: Posterior Border of Pectoralis Major
• A commonly accepted definition for the anterior axillary line is the posterior border of Pectoralis Major. • However, the border becomes indistinct and absent below the 6th costal cartilage • Therefore we propose a vertical line, displayed as a green arrow at the intersection of the posterior border of Pectoralis Major and the 2nd rib, which is at the same position on each axial slice Proposal 1: Vertical Lines The Border between the Lateral and Posterior Sectors: The Tip of the Scapula
• We propose using an vertical line through the tip of the scapula, displayed by a yellow arrow in a fixed location on each axial section, for the border between the lateral and posterior sectors • It is acknowledged that the tip of the scapula is not constant between different cases (see slide 6) Proposal 1: Vertical Lines
1 Mobile white arrow - Costochondral Joint (CCJ) 2 Fixed green arrow - posterior border of Pectoralis Major at 2nd rib 3 Fixed yellow arrow - tip of scapula 4 Mobile orange arrow - costotransverse joint
• Imagine “fixing” the position of the yellow and green arrows on the computer screen with Blu- Tack / Power Tack • The fixed arrows (Green and Yellow) are intended to preserve the size of the sectors up and down the chest. • The white arrow (each CCJ) has to be mobile, as the CCJ moves laterally with each successive rib • Orange is mobile (but does not vary much) Proposal 1: Vertical Lines
• Anterior / Lateral Sector boundary: – vertical line from the intersection of the posterior border of Pectoralis Major and the 2nd rib
• Lateral / Posterior Sector boundary: – Vertical line from the tip of the scapula
The following diagrams will provide full explanation Proposal 1 2nd Costochondral Junction Proposal 1 4th Costochondral Junction Proposal 1 6th Costochondral Junction Proposal 1 8th Costochondral Junction
At this level and below, the anterior sector is lost Proposal 1 10th Costochondral Junction
At this level there is no Anterior Sector Proposal 1: Vertical Lines
• Note – the Anterior Sector becomes smaller and disappears at about the 8th Costochondral Joint, because the Costochondral Joints move laterally, further down the chest. – The Lateral Sector becomes smaller below the 8th Costochondral Joint, because the Costochondral Joints move into the Lateral Sector. – The Posterior Sector remains constant Proposal 2: Muscle Border Lines
• Anterior / Lateral Sector boundary: – posterior border of Pectoralis Major
• Lateral / Posterior Sector boundary: – anterior border of Latissimus Dorsi
The following diagrams will provide full explanation Proposal 2 – Muscle Border Lines
1 Mobile white arrow - Costochondral joints 2 Mobile green arrow - posterior border of Pectoralis Major 3 Mobile blue arrow - anterior border of latissimus dorsi 4 Mobile orange arrow - costotransverse joint
• Green (posterior border of Pec. major) is mobile – moves medially at each lower level. • White (CCJ) is mobile as the CCJ moves laterally lower down the chest • Blue (anterior border of Lat. dorsi) is mobile – moves posteriorly at each lower level • Orange is mobile (but does not vary much) Proposal 2 2nd Costochondral Junction
*
* Is a fracture here, in the posterior sector, really posterior? Proposal 2 4th Costochondral Junction Proposal 2 6th Costochondral Junction
The border of Pec. Major only extends to the 6th Costal Cartilage At this level and below, there is no anterior sector Proposal 2 th Proposal 1 8 th Costochondral Junction 8 Costochondral Junction
The border of Pec. Major only extends to the 6th Costal Cartilage – there is no anterior sector at this level Proposal 2 10th Costochondral Junction Proposal 2 – Muscle Border Lines
• Note – The Anterior Sector is very small, due to the origin of Pec. Major from the upper 6 costal cartilages. – The Lateral Sector runs obliquely, moving slightly more posteriorly at lower levels – The Posterior Sector is larger than the Anterior and Lateral Sectors combined, and quite “anterior” at higher levels. It becomes smaller as the anterior border of Lat. Dorsi moves posteriorly down the chest Proposal 3 – Angle from Mid-Thoracic Point
• Using angles from the anterior midline, measured from the mid thoracic point • Mid Thoracic point is the mid point from the anterior table of the sternum (or linear alba) and the posterior aspect of the vertebral spinous process
The following diagrams will provide full explanation Proposal 3 – Angle from Mid-Thoracic Point
• Anterior / Lateral Sector boundary: – 60 degree angle
• Lateral / Posterior Sector boundary: – 120 degree angle – The mean angle of the scapula tip in 96 cases was 117o (SD 13.29, range 97-143) CCJ Thoracic Proposal 3 Midline Costo- 2nd Costochondral chondral 60 0 Anterior Junction
Lateral
Mid Thoracic Pont
120 0
Posterior
Paravertebral CTJ
60 o and 120o angles from the midline divides the chest into 3 sectors, but the Costochondral and Paravertebral sectors “take priority” CCJ Thoracic Midline Proposal 3 Costo- th chondral 4 Costochondral 60 0 Anterior Junction
Lateral
Mid Thoracic Pont
120 0
Posterior
CTJ Paravertebral Thoracic CCJ Midline Proposal 3 Costo- chondral 6th Costochondral 0 60 Anterior Junction
Lateral
Mid Thoracic Pont
120 0
Posterior
CTJ Paravertebral Thoracic Midline Proposal 3 Costo- 8th Costochondral chondral 60 0 Junction
CCJ
Lateral
Mid Thoracic Pont
120 0
Posterior
CTJ Paravertebral No anterior sector at this level. Thoracic Midline Proposal 3 10th Costochondral
60 0 Costo- Junction chondral
CCJ
Mid Thoracic Pont Lateral
120 0
Posterior
CTJ Paravertebral Proposal 3 – Angle from Mid-Thoracic Point
• Note: – The Anterior Sector is small, and it disappears completely at about the 7th or 8th Costochondral Junction – The Lateral Sector remains the same size, until the CCJ moves into it at about the 8th CCJ, then it becomes smaller – The Posterior Sector is constant in size and about the same as most of the Lateral Sector Proposal 4: Equal Size Sectors
• Anterior / Lateral Sector boundary: – 1/3rds of the circumference between the costochondral junction and the costotransverse joint
• Lateral / Posterior Sector boundary: – 2/3rds of the circumference between the costochondral junction and the costotransverse joint
The following diagrams will provide full explanation
Costo- Proposal 4 chondral 2nd Costochondral Junction
Anterior
Lateral
Posterior
Paravertebral The three sectors remain equal in size, although all become smaller at lower levels All three sectors are present at each level Costo- Proposal 4 chondral 4th Costochondral Junction
Anterior
Lateral
Posterior
Paravertebral Proposal 4 Costo- chondral 6th Costochondral Junction
Anterior
Lateral
Posterior
Paravertebral Proposal 4 Costo- 8th Costochondral chondral Junction
Anterior
Lateral
Posterior
Paravertebral Proposal 4 10th Costochondral Junction Costo- chondral
Anterior *
Lateral
Posterior
Paravertebral
* Is a fracture here, in the anterior sector, really anterior? Proposal 4 – Equal size sectors
• Note: – At each level, the sectors are equal in size – The borders between sectors become more lateral and then posterior at lower levels – The sectors lie obliquely on the chest wall – Even the “anterior” sector lies “posterolaterally” at the level of the 10th CCC Summary slide of advantages and disadvantages of each Proposal
Proposal 1: Proposal 2: Proposal 3: Proposal 3: Vertical Lines Muscle Borders Measured Angles Equal Size Sectors Anterior Sector Small Smaller than Approximately the The same size as Absent below 8th Proposal 1 same as Proposal 1 Lateral and CCC Absent below 6th Absent below 8th Posterior CCC CCC Anterior/Lateral Fixed and easy to Can be difficult to Fixed. 60 degrees Runs obliquely: is Sector Boundary define see. Absent below is easy to estimate “lateral” at 8th CCC 6th CCC Lateral Sector Constant size until Runs obliquely Constant size until The same size as 8th CCJ, Scapula CCJ Anterior and position not fixed Posterior Lateral/Posterior Fixed and easy to Runs obliquely Fixed. 120 degrees Runs obliquely Sector Boundary define is easy to estimate Posterior Sector Constant size Very large Constant Size The same size as compared to Anterior and others Lateral