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Orthopaedic Clinic

Para rectus anterior Lumbar approach
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Relevant Anatomy:

 

Anterior musculature: The rectus femoris is a long flat-paired muscle that spans the length of the anterior abdomen. The rectus muscle on either side is separated by the linea alba, a relatively avascular fibrous band. The muscle is supplied by inferior epigastric artery in its lower half. The artery may be injured during a para-median incision, however if injured the vessel can be tied off.  The injury to this vessel may be a cause of significant morbidity while performing the laparoscopic procedures. The injury may cause leaking of blood in the operative field, postoperative bruising and significant blood loss that may go un recognized until after the procedure.

Anterior vessels: The aorta and common iliac vein divide into the right and left common iliac vessels in front of the L4 vertebral body. Here the aorta and vena cava are firmly attached to the prevertebral sheath. Mobilizing these large vessels proximally may require ligation or mobilization of some of their branches. Since the veins that are present on right side of arteries, are thin walled and fragile, a left sided dissection is preferred.

The median sacral artery has its origin from the aorta at L4 level, and it runs down in front of sacral promontory to the sacral hollow. The ascending lumbar vein is inconstant in its origin; most commonly it originates at the lateral sacral region from the common iliac vein. It ascends between the psoas major and the roots of lumbar transverse processes passing behind the median arcuate ligament at the T 12 level from whereon it combines with different sub costal vessels to form the azygos vein on the right side and the hemi azygos vein on the left side.

Sympathetic nervous system: A diffuse plexus of the sympathetic nerves known as presacral plexus runs directly below the bifurcation of the aorta to the anterior surface of the sacral promontory. Injury to this plexus is associated with retrograde ejaculation in males.

 

Ureters: The ureters course down the posterior abdominal wall anterior to the psoas muscle. The surgeon can identify the ureters by their muscular wall, and the presence of peristalsis upon being stimulated.

 

Positioning:

 

The patient is positioned supine on a radiolucent table. Peripheral nerve and bony prominences are well padded . The arms are abducted 90 degrees and placed on arm boards on either side, ensuring that they do not impede movement of the fluoroscopy machine

 

Exposure:

 

The location and the extent of the incision are determined by the pathology, the size of the patient, and the preference of the approach by the surgeon. A vertical Para median incision  allows more flexibility in addressing the underlying pathology. A horizontal incision however may be more cosmetic. The L5-S1 disc space is generally situated one to two-finger breadths above the symphysis pubis, while the L4-5 disc space is between the symphysis and the umbilicus. Generally a left sided vertical incision is used for the open approach.

 

After incising the skin and subcutaneous tissue the anterior rectus sheath  is visualized. The anterior rectus sheath is incised, and the rectus abdominis muscle  retracted towards the midline to expose the posterior rectus sheath. The posterior rectus sheath, the transversalis fascia, and the anterior peritoneum  are often indistinguishable. The transversalis fascia should be carefully separated from anterior peritoneum to prevent creating a rent in the peritoneum and incised to enter the retro-peritoneum (The pre-peritoneal fat and the peritoneum are retracted towards midline to expose the retroperitoneal space. The first structure seen is the left psoas muscle and the genito - femoral nerve that lies on this muscle and should be protected

 

To expose the L4 - L5 disc space the common iliac vein is retracted medially while the ureters and the illio psoas muscle are retracted laterally . The ascending lumbar veins that arises from the left iliac vein ascends up in a posterolateral direction, should preferably be ligated as it may potentially get torn during the retraction of common iliac vein medially. Dissection in the midline is best carried out bluntly, using a limited bipolar electro-cautery. Uni polar electrocautery should not be used in the midline while exposing the disc space, as they may damage the presacral plexus and result in retrograde ejaculation or impotence in males. A radiographic confirmation with a needle placed in the disc space may be done before proceeding with surgery.

To approach the L5 S1 disc space, the dissection is carried between the iliac vessels. The median sacral artery and vein arise at the bifurcation of common iliac vessels; these should be isolated, and transected between the ligatures.  The prominent sacral promontory provides a rough confirmation of the level, but it is prudent to place a needle in the disc space and obtain a radiographic confirmation.

 

 

Potential Complications:

 

                 Uncontrolled hemorrhage / exsanguinations from injury to large vessels or major branches.

                 Damage to presacral plexus of sympathetic nerve leading to retrograde ejaculation and impotence in men.

                 Injury to ureter resulting in urinoma in retroperitoneal space / fistula / infections.

                 Peritoneal tears may occur while dividing the transversalis fascia, these must be repaired using an absorbable suture; care should be taken so as not to damage the viscera by the suture needle (it is preferable to use round body needle for the repair).

 

 

 

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