Posterior Approach for Debridement of the Psoas Abscess

Summary

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.

Abstract

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–L5. The transverse processes, pars interarticularis and lamina of L1–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.

Introduction

A psoas abscess (PA) is a rare diagnosis reported in 0.4–1 per 10,000 admissions to the hospital^1,2. 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 ....

Protocol

The use of deceased human specimens, for the purposes of developing this method, has been approved by the WellStar Research Institute's institutional review board and conforms with the ethical guidelines established by the institution'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

1. Place the previously thawed cadaveric specimen on the surgical table in the supine position and illuminate the field with surgical lights. Cover the specimen with a....

Results

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–L3, but narrowed down to approximately 6 and 1 mm at L4 and L5, respectively........

Discussion

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.

Materials

List of materials used in this article

Name	Company	Catalog Number	Comments
Blunt ended dissecting scissors			To cover the specimens
Camera	Sony a7 III	ILCE-7
Cobb elevator	Sklar	40-6950	For isolation of TP and general dissection
Dissection table
Formalin fixed cadavers	Restore Life USA	N/A	Transected at T12 with abdominal organs removed
Hemostats
Retractors			For blunt dissection
Rongeur	Sklar	40-4085
Scissors	Sklar	15-2555
Surgical absorbent pads			Placed under the cadaver to absorb fluids
Surgical blades/scalpels	Dynarex	4110
Surgical drape/blanket			For blunt dissection
Surgical gauze sponges
Surgical lights
Surgical Ruler	Aspen Surgical Products	42182702
Tissue forceps
Tool tray