approaches to the lumbar spine

Anterior

transperitoneal
Preparation

·      enema on preoperative night to clean and flatten bowel

·      shave abdomen and pubis

·      insert IDC

Position

·      supine

·      place small of back over flexion crease in table

·      improve exposure wrt abdominal contents

·      break table to hyperextend lumbar spine

·      tilt table to place head down

Incision

Vertical

·      midline incision

·      distal extent

·      3 fingerbreadths above pubis

·      proximal extent

·      L5 – 1 fingerbreadth above umbilicus

·      L4 – 3 fingerbreadths above umbilicus

·      pull umbilicus to right hand side

Transverse

·      another option is curved transverse ‘smile’ incision

·      better cosmetic result

·      involves splitting rectus abdominis

·      alternately can lift skin flaps and divide linea alba vertically as for vertical incision

Approach

·      open linea alba in midline

·      identify and open peritoneum

·      grasp with 2 blunt forceps

·      open with scissors

·      retract abdominal contents

·      bowel loops to right

·      sigmoid colon to left

·      hold with moist sponges

·      one each side

·      one superiorly

·       insert retractors

·      self retainer

·      malleable inferiorly

·      open posterior peritoneum

·      pick up and open carefully with scissors

·      can first inject with saline to dissect off vessels

·      lift retroperitoneal flaps

·      identify structures by palpation

·      sacral promontory and L5-S1 disc

·      aorta and iliac vessels

·      retract vessels

·      start plane just to right of left common iliac artery

·      sweep left common iliac vessels to left

·      use peanuts to clear smaller structures

·      presacral sympathetic plexus pushed to left

·      sacral vessels ligated or pushed to right

·      check level with x-ray

·      needle in L5-S1 disc

·      insert 4 Steinmann pins for retraction

Dangers

Presacral plexus

·      superior hypogastric nerves

·      sympathetic fibres

·      run in front of aorta

·      carry ejaculation fibres from L2 sympathetic ganglion

·      become presacral nerves between iliac vessels

·      may be in one of three configurations

1.   trunkal type - 2 or 3 longitudinal trunks (40%)

2.   plexiform type - 3-5 trunks and numerous anastomoses (40%)

3.   lamellar type – flattened network of fibres (20%)

·      bifurcate to form left and right hypogastric nerves

·      join inferior hypogastric plexus

Prevertebral vessels

Arteries

·      enters abdominal cavity under crus of diaphragm at T12

·      lies to left of vertebral bodies

·      bifurcates into common iliac arteries to left of midline

·      bifurcation variable

·      usually at L4-5 disc

·      thus left common iliac artery more vertical and more short than right common iliac artery

Veins

·      common iliac veins join in front of L5 behind right common iliac artery

·      IVC ascends to right of aorta

·      left common iliac vein lies within aortic bifurcation