40 Minimally Invasive Oblique Anterior Lumbar Interbody Fusionss
Summary
Keywords: minimally invasive anterolateral approach oblique lateral interbody fusion lumbar spine spinal fusion
40.1 Introduction
Anterior lumbar interbody fusion has gained increasing attention in the 1990s of the last century because from the biomechanical point of view, 360 or 270 degrees fusion seemed to achieve the highest fusion rates of all fusion techniques.1,2 However, the conventional anterior approaches seemed to be too invasive to justify their use for the treatment of degenerative diseases. The first description of a laparoscopic approach to L5–S1 in 1990 was a kind of starting point for development of a variety of different less invasive or “mini-open” anterior surgical approaches to the lumbar spine.3 Even though laparoscopic surgery seemed to be the least invasive version of approaching the lumbar spine from anterior, it was associated with a number of technical difficulties, pitfalls, and hazards as well as with a long “learning curve” for spine surgeons. This was probably the reason why it never became a “standard” procedure in spine centers around the world.
In 1997, Mayer described two “mini-open” access techniques to the lumbar spine and preliminary results for anterior interbody fusion which he called MiniALIF.4 They were based on the application of microsurgical philosophy to the well-known standard anterior approaches. The approach to the lumbar levels L2–L5 was actually the approach which is nowadays known as oblique lumbar interbody fusion (OLIF) or ante-psoas approach.5,6
40.2 Indications
The approach can be used for anterior lumbar interbody fusion in the following diseases (with or without additional posterior instrumentation):
a)Degenerative disc disease with discogenic low back pain.
b)Degenerative and isthmic spondylolisthesis (in combination with posterior reduction and instrumentation).
c)Spinal stenosis with instability (in combination with decompression and posterior reduction and instrumentation).
d)Foraminal stenosis (as stand-alone anterior interbody fusion with indirect decompression).
e)Failed back surgery syndrome.
f)Fractures.
g)Spondylitis/spondylodiscitis.
h)Pseudoarthrosis following other types of fusion (e.g., posterolateral, posterior lumbar interbody fusion [PLIF], transforaminal lumbar interbody fusion [TLIF]).
40.3 Contraindications
There are no absolute contraindications to this surgical approach; however, the following situations can be relative contraindications:
a)Previous surgery through a retroperitoneal approach (e.g., kidney surgery) on the same side.
b)Extremely lateral course of common iliac vein of the left side covering the lateral aspect of the L4/L5 intervertebral space (rare).
40.4 Preoperative Planning
40.4.1 Patient’s Informed Consent
Whereas the general complications, such as deep venous thrombosis, pulmonary embolism, infection, etc., do not differ from other spine procedures, the patient should be informed about potential specific complications and risks:
1.Denervation of the rectus muscle due to injury of iliocostal nerve.
2.Abdominal postincisional hernia.
3.Lumbar plexus irritation or compression due to forceful or prolonged retraction of the psoas muscle.
4.Groin pain due to compression and irritation of the genitofemoral nerve.
5.Vascular injury in the retroperitoneal space (segmental vessels, ascending lumbar vein, and common iliac vein and artery on the left side) with retroperitoneal hematoma.
6.Nerve and spinal cord injury with incomplete of complete neurological deficits.
7.Dural tears with pseudomeningocele or cerebrospinal fluid (CSF) fistulas.
8.Temperature differences (usually temporary), dysesthesias, disturbance of sweat secretion in the lower extremities due to dissection of the sympathetic trunk.
9.Injury of peritoneum, bowel, ureter, kidney, and spleen leading to infection, hemorrhage, scar tissue, disturbances, and constrictions of the urinary tract.
40.4.2 Anatomical Considerations
The disc spaces L2/L3, L3/L4, and L4/L5 are reached through a left-sided retroperitoneal approach along the medial border of the psoas muscle (“ante-psoas” approach). Topographical anatomy of the anatomic structures anterior and lateral to the target area should be studied carefully on a preoperative magnetic resonance imaging (MRI) (Fig. 40.1a). A special focus is on the size and shape of the psoas muscle as well as on the position and course of the retroperitoneal vessels.7,8,9
For the approach to L4/L5, a focus should be on the common iliac vein as well as on the presence and size of an ascending lumbar vein on the left side (Fig. 40.1b).
Conventional X-rays of the lumbar spine in two planes provide information about the presence of lumbar concavity and also the height of the intervertebral space. The position of the inferior borders of the rib cage is important to notice for the approach at L2/L3 (Fig. 40.1c).
The patients are treated with routine mechanical large-bowel preps to empty the colon starting 24 hours prior to surgery.
The use of a bright headlamp (LED or xenon light source) and optical aids (surgical microscope, loupes) is recommended.
The operation is performed under general anesthesia. Arterial and central venous pressure-lines placement for hemodynamic monitoring is recommended.
40.5 Patient Positioning
The patient is placed in a right lateral position on an adjustable surgical table (Fig. 40.2a). The pelvis is centered over the angulating part of the table to enable a left convex bending of the lumbar spine. This increases the distance between the iliac crest and the inferior border of the rib cage. One advantage of this positioning is that the abdominal contents “fall away” from the surgical field giving way for the approach corridor even in obese patients (Fig. 40.2b).
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