The authors would like to acknowledge all those who donate their bodies for research and keep impacting others after they have gone.

The use of deceased human specimens, for the purposes of developing this method, has been approved by the WellStar Research Institute&#39;s institutional review board and conforms with the ethical guidelines established by the institution&#39;s ethics committee. The specimens used in this method were all formalin-fixed, transected at the T12 vertebral body, and had their abdominal organs and viscera removed.
1. Preparation of the cadaveric specimen and surgical field
<ol>
	<li>Place the prev...

<ol>
	<li>Bartolo, D. C., Ebbs, S. R., Cooper, M. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Psoas+abscess+in+Bristol:+a+10-year+review.">Psoas abscess in Bristol: a 10-year review.</a> International Journal of Colorectal Disease. 2, 72-76 (1987).</li><li>Dietrich, A., Vaccarezza, H., Vaccaro, C. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Iliopsoas+abscess:+presentation,+management,+and+outcomes.">Iliopsoas abscess: presentation, management, and outcomes.</a> Surgical Laparoscopy Endoscopy &amp; Percutaneous Techniques. 23, 45-48 (2013).</li><li>Santaella, R. O., Fishman, E. K., Lipsett, P. A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Primary+vs+secondary+iliopsoas+abscess.+Presentation,+microbiology,+and+treatment.">Primary vs secondary iliopsoas abscess. Presentation, microbiology, and treatment.</a> Archives of Surgery. 130, 1309-1313 (1995).</li><li>Yamagami, T., et al. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Percutaneous+drainage+of+psoas+abscess+under+real-time+computed+tomography+fluoroscopic+guidance.">Percutaneous drainage of psoas abscess under real-time computed tomography fluoroscopic guidance.</a> Skeletal Radiology. 38, 275-280 (2009).</li><li>Tabrizian, P., Nguyen, S. Q., Greenstein, A., Rajhbeharrysingh, U., Divino, C. M. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Management+and+treatment+of+iliopsoas+abscess.">Management and treatment of iliopsoas abscess.</a> Archives of Surgery. 144, 946-949 (2009).</li><li>Labrechts, M. J., Wiegers, N. W., Ituarte, F., Shen, F. H., Nourbakhsh, A. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safe+zone+for+irrigation+and+debridement+of+psoas+abscess+through+a+dorsal+spinal+approach.">Safe zone for irrigation and debridement of psoas abscess through a dorsal spinal approach.</a> Surgical and Radiologic Anatomy. 40, 1217-1221 (2018).</li><li>Wilkinson, D. J., Piasecki, M., Atherton, P. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+age-related+loss+of+skeletal+muscle+mass+and+function:+Measurement+and+physiology+of+muscle+fibre+atrophy+and+muscle+fibre+loss+in+humans.">The age-related loss of skeletal muscle mass and function: Measurement and physiology of muscle fibre atrophy and muscle fibre loss in humans.</a> Ageing Research Reviews. 47, 123-132 (2018).</li><li>Aszmann, O. C., Dellon, E. S., Dellon, A. L. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Anatomical+course+of+the+lateral+femoral+cutaneous+nerve+and+its+susceptibility+to+compression+and+injury.">Anatomical course of the lateral femoral cutaneous nerve and its susceptibility to compression and injury.</a> Plastic and Reconstructive Surgery. 100, 600-604 (1997).</li><li>Spivak, J. M., Paulino, C. B., Patel, A., Shanti, N., Pathare, N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Safe+zone+for+retractor+placement+to+the+lumbar+spine+via+the+transpsoas+approach.">Safe zone for retractor placement to the lumbar spine via the transpsoas approach.</a> Journal of Orthopedic Surgery. 21, 77-81 (2013).</li><li>Reid, J. G., Livingston, L. A., Pearsall, D. J. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=The+geometry+of+the+psoas+muscle+as+determined+by+magnetic+resonance+imaging.">The geometry of the psoas muscle as determined by magnetic resonance imaging.</a> Archives of Physical Medicine and Rehabilitation. 75, 703-708 (1994).</li><li>Hanson, P., Magnusson, S. P., Sorensen, H., Simonsen, E. B. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Differences+in+the+iliolumbar+ligament+and+the+transverse+process+of+the+L5+vertebra+in+young+white+and+black+people.">Differences in the iliolumbar ligament and the transverse process of the L5 vertebra in young white and black people.</a> Acta Anatomica. 163, 218-223 (1998).</li><li>Ilayperuma, I., Nanayakkara, B. G., Hasan, R., Uluwitiya, S. M., Palahepitiya, K. N. <a target="_blank" href="http://www.ncbi.nlm.nih.gov/entrez/query.fcgi?db=PubMed&cmd=Search&doptcmdl=Citation&defaultField=Title+Word&term=Coracobrachialis+muscle:+morphology,+morphometry+and+gender+differences.">Coracobrachialis muscle: morphology, morphometry and gender differences.</a> Surgical and Radiologic Anatomy. 38, 335-340 (2016).</li></ol>

The authors declare that they have no competing financial interests.

The most critical steps for finding the safe zone for irrigation and debridement of a psoas muscle abscess through a dorsal approach are 1) careful blunt dissection of the lumbar plexus during the ventral and dorsal approach; 2) preservation of the transverse processes during their isolation, as they can be fragile, for better visualization; and 3) calibrating the ImageJ software with the surgical ruler and taking careful measurements to elucidate the relationship between the TP, LP, and psoas muscle.
<p class="jove_...

A psoas abscess (PA) is a rare diagnosis reported in 0.4&#8211;1 per 10,000 admissions to the hospital1,2. A PA can be caused by hematogenous spread, lymphatic spread from a distant infectious site, or by contiguous spread from adjacent organs3. Currently, percutaneous drainage under real-time computed tomography is a safe and first-line treatment for a PA4. Dietrich et al. found that it has a higher success rate compared to open surgery, offering a lower mortality rate and shorter hospital length of stay2. However, Tabrizian et al. found that 44% of the patients treated with percutaneous drainage underwent open surgery to eradicate the infection5.
Given the rate of open surgeries performed for treatment of psoas abscesses, the aim of the method developed in this study is to find a &#34;safe zone&#34; for irrigation and debridement (I&#38;D) of a psoas abscess via a dorsal approach. An initial ventral approach is taken to identify and isolate key anatomical structures, including the transverse processes (TP), psoas muscle, and lumbar plexus (LP). A dorsal approach is then taken to further isolate the TP and LP from the surrounding structures. Throughout the various steps of dissection, photographs are obtained. Once the dissection is complete, the images are uploaded to ImageJ (1.48v, National Institute of Health) and several measurements are taken to identify the relationship between the TP, LP, and psoas muscle. Finally, using the measurements obtained, a &#34;safe zone&#34; for entering the substance of the psoas and minimizing the risk of lumbar plexus injury is calculated. To our knowledge, this is the first work that uses the transverse processes as reference points for the purpose of finding a safe zone for I&#38;D of a psoas abscess.

<table border="1" fo:keep-together.within-page="1" fo:keep-with-next.within-page="always">
	<tbody>
		<tr>
			<td>Blunt ended dissecting scissors</td>
			<td></td>
			<td></td>
			<td>To cover the specimens</td>
		</tr>
		<tr>
			<td>Camera</td>
			<td>Sony a7 III</td>
			<td>ILCE-7</td>
			<td></td>
		</tr>
		<tr>
			<td>Cobb elevator</td>
			<td>Sklar</td>
			<td>40-6950</td>
			<td>For isolation of TP and general dissection</td>
		</tr>
		<tr>
			<td>Dissection table</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Formalin fixed cadavers</td>
			<td>Restore Life USA</td>
			<td>N/A</td>
			<td>Transected at T12 with abdominal organs removed</td>
		</tr>
		<tr>
			<td>Hemostats</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Retractors</td>
			<td></td>
			<td></td>
			<td>For blunt dissection</td>
		</tr>
		<tr>
			<td>Rongeur</td>
			<td>Sklar</td>
			<td>40-4085</td>
			<td></td>
		</tr>
		<tr>
			<td>Scissors</td>
			<td>Sklar</td>
			<td>15-2555</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical absorbent pads</td>
			<td></td>
			<td></td>
			<td>Placed under the cadaver to absorb fluids</td>
		</tr>
		<tr>
			<td>Surgical blades/scalpels</td>
			<td>Dynarex</td>
			<td>4110</td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical drape/blanket</td>
			<td></td>
			<td></td>
			<td>For blunt dissection</td>
		</tr>
		<tr>
			<td>Surgical gauze sponges</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical lights</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Surgical Ruler</td>
			<td>Aspen Surgical Products</td>
			<td>42182702</td>
			<td></td>
		</tr>
		<tr>
			<td>Tissue forceps</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
		<tr>
			<td>Tool tray</td>
			<td></td>
			<td></td>
			<td></td>
		</tr>
	</tbody>
</table>

posterior approach for debridement of the psoas abscess

This method focuses on outlining a safe zone for irrigation and debridement of a psoas abscess through a posterior approach. Initially, an anterior approach to the spine was performed to ensure that the anterior longitudinal ligament and the psoas muscle could be visualized. All the abdominal organs were removed. Subsequently, a posterior approach was performed to remove the paraspinal muscles from L1&#8211;L5. The transverse processes, pars interarticularis and lamina of L1&#8211;L5 were identified. The exiting nerve root was identified between the transverse processes and followed into the substance of the psoas muscle. Using the anterior and posterior approach, the lumbar plexus was isolated from the substance of the psoas muscle. Before and after various steps of dissection, digital photographs were obtained. These images were uploaded into ImageJ and multiple measurements, including the distance between the lateral superior and inferior tip of each TP to the most lateral region of the plexus, the distance between the lateral superior and inferior tip of the TP to the lateral edge of the psoas, and the width of the lumbar plexus were recorded. The safe zone for entering the substance of the psoas muscle was defined between the lateral edge of the psoas muscle and the lateral edge of the lumbar plexus. The relationship of this interval to the tip of the transverse process at each level was measured and reported.

Eleven formalin-fixed cadavers were included, with an average age of 80.5 years6. Two cadavers had damaged lumbar vertebrae on the right side and were removed. Thus, a total of 20 measurements were included, 13 female and 7 male. The medial border of the safe zone, defined by the most lateral aspect of the lumbar plexus, was found to be approximately 1 cm medial to the tip of the TP at L1&#8211;L3, but narrowed down to approximately 6 and 1 mm at L4 and L5, respect...

Watch this Scientific Journal Video about Posterior Approach for Debridement of the Psoas Abscess at JoVE.com

Posterior Approach for Debridement of the Psoas Abscess

This is a cadaveric study investigating the landmarks for the posterior approach for irrigation and debridement of the psoas abscess. The interval between the transverse processes (TP) was used to access the substance of the psoas muscle.

This method focuses on outlining a safe zone for irrigation and debridement of a psoas abscess through a posterior approach. Initially, an anterior ...

This method uses the transverse processes, psoas muscle, and lumbar plexus to calculate a safe zone for entering the psoas muscle through a dorsal-spinal approach. The main advantage of this technique is that it improves patient safety by providing the measurements for calculating a safe zone for the irrigation and debridement of a psoas abcess. Before beginning the procedure, place the previously thawed cadaveric specimen on the surgical table in the supine position and illuminate the field with surgical lights, then cover the specimen with a blanket, sparing the upper and lower abdomen.For the isolation and identification of key anatomical structures using a ventral approach, use a blade to make a midline cranial to caudal incision down to the hypogastric region and directly perpendicular to the anterior superior iliac spines. Make a transverse cut between the anterior superior iliac spines and use a surgical blade and scissors to reflect and remove the abdominal musculature and fascia to improve visualization and to aid in measurement accuracy. Identify the transverse processes, laminae, pars interarticularis of the lumbar vertebrae, psoas muscles, and the nerve roots of the lumbar plexus exiting the neuroforamina.Once all of the key anatomic structures have been identified as undamaged and intact, carefully turn over the specimen to begin the dorsal approach. With the specimen in the prone position, use a surgical blade, scissors, Cobb Elevator, and other surgical tools to resect the latissimus dorsi and paraspinal muscles, starting sequentially from the posterior spinous process to the transverse processes. Use the Cobb Elevator and other surgical tools as appropriate to isolate the transverse processes from any remaining soft tissue attachments to aid in visualization and accurate measurements.With the paraspinal muscles now removed, place a surgical ruler parallel to the surgical field to obtain digital photographs of the intact psoas muscle to demonstrate its relationship to the transverse processes at each vertebral level. When a sufficient number of good quality images have been acquired, turn the specimen back to the supine position, use a surgical blade to strip the psoas muscle from its medial attachment at each lumbar body and use blunt-edged scissors to carefully expose the entire lumbar plexus and to reflect the psoas muscle laterally. With a surgical ruler placed parallel to the surgical field, take additional photographs to capture the relationship of the lumbar plexus to the transverse process at each level.Finally, turn the specimen on its side and obtain additional photographs to demonstrate the relationship of the transverse processes to the lumbar plexus in the sagittal plane. For calibration of the tissue measurements, open the image to be analyzed in ImageJ and use the magnifying glass tool to zoom into the surgical ruler in the photograph. Use the line-drawing tool to carefully draw a straight line between the margins of a one-millimeter segment on the ruler and, under Analyze, select Set Scale to set the known distance to one and the unit of length to one millimeters, then place a check in the box next to Global and click OK.The measurements will be calibrated according to the number of pixels per millimeter on the ruler.To calculate the maximal irrigation and debridement and safe zone, use the line-drawing tool to draw a straight line between the lateral superior tip of each transverse process to the lateral edge of the psoas at the same level. When all of the lines have been drawn, select Measure from the Analyze menu. A new Results window will open and the measurements will appear in millimeters in the new window in the Length column in the order that they were obtained, then repeat the calculation for each of the measurements indicated in the table.The area for maximum medial to lateral irrigation and debridement in the coronal plane is determined by measuring the distance from the superior and inferior tips of the transverse processes to the lateral edge of the psoas muscle at the corresponding vertebral level. On average, the maximal extent of lateral debridement can be performed 5.5 and 5.7 millimeters medial to the inferior and superior tips of the transverse processes at L1, 4.7 and 5.1 millimeters medial at L2, 1.8 and 2.5 millimeters medial at L3, 0 and 0.4 millimeters medial at L4, and 3.8 and 3.7 millimeters lateral at L5.In the sagittal plane, the lumbar plexus is typically approximately 15 to 20 millimeters anterior to the transverse processes. Remember to be careful when working around the transverse processes as they can be fragile and any damage would disqualify any measurements obtained in relation to these landmarks.

posterior-approach-for-debridement-of-the-psoas-abscess

Research

JoVE Journal

Medicine

10.6K Views.  WellStar Atlanta Medical Center. This method uses the transverse processes, psoas muscle, and lumbar plexus to calculate a safe zone for entering the psoas muscle through a dorsal-spinal approach. The main advantage of this technique is that it improves patient safety by providing the measurements for calculating a safe zone for the irrigation and debridement of a psoas abcess. Before beginning the procedure, place the previously thawed cadaveric specimen on the surgical table in the supine position and illuminate the field ...