Anterior to psoas (ATP) fusion of the lumbar spine: evolution of a technique facilitated by changes in equipment

Abstract

Background: Lateral interbody cages have been proven useful in spinal fusions. Spanning both lateral cortical rims while sparing the Anterior Longitudinal Ligament, the lateral interbody cages restore and maintain disc height while adding stability prior to supplemental fixation. The standard approach for their insertion is by a 90-degree lateral transpsoas method. This is relatively bloodless compared to other techniques although has its limitations, requiring neuro-monitoring and being, at times, very difficult at L4/5 due to iliac crest obstruction or an anterior plexus position. An oblique approach, with the patient in lateral decubitus, passes anterior to the iliac crest, retroperitoneal, and being anterior to psoas, eliminates the need for neuro-monitoring.Methods: Twenty-one consecutive patients underwent surgery for a total of 32 levels instrumented with the ATP technique. Mean age at the time of surgery was 62.4±7.4 years. There was a 6 months minimum clinical follow up, with imaging to assess fusion, at 6 and 12 months. Indications included symptomatic degenerative lumbar spondylosis +/− spondylolisthesis, leg and back pain. All patients were assessed with the Oswestry Disability Index (ODI), Visual Analog Scale 100 mm for back pain (VASb) and for leg pain (VASl) preoperatively, at 3, 6 and 12 months. Last follow-up was at 12 months for 9 patients and the rest had 6 months follow up.Results: Statistical analysis showed significance for the results in ODI, VASb and VASl with improvement in all components except for one patient with worsening VASl. Eight patients had complications related to surgery which were still present at last follow-up including moderate weakness of hip flexion and EHL weakness. Lateral cutaneous nerve (LCN) palsy on the side of the approach was also seen as well as sympathectomy effect related to the mobilization of the sympathetic trunk. One patient, who also suffered from multiple sclerosis, experienced psoas abscess 3 months post op that required drainage. Conclusions:The left sided anterior to psoas approach offers the most natural corridor to the disc space.The novel instruments and method described here allows insertion of large lateral cages between L2 to L5, without the problems associated with the transpsoas approach, particularly at L4/5.

Morphometric anatomy of the lumbar sympathetic trunk with respect to the anterolateral approach to lumbar interbody fusion: a cadaver study

“…No significant association was found between corridor sizes with gender. Indeed, these morphometric studies are in keeping with the clinical experience by initial ATP/OLIF studies (2,6,11), where a left sided approach is preferable to all but L5/S1 disc space, as a right sided approach is more likely to require mobilization of the inferior vena cava. At L5/S1 a right sided approach may be preferred as the right common iliac vein is typically more lateral and unlike the left, rarely adherent to the spine or disc space.…”

“…However, the standard lateral approach, which traverses the psoas muscle (i.e., transpsoas approach), has its own limitations and complications (2)(3)(4)(5)(6). Of most concern is the potential for injury to the lumbar plexus, minimized by using intraoperative neuromonitoring (7).…”

Development and Application of Oblique Lumbar Interbody Fusion

“…In the current reports, the incidences of sympathetic chain injury were varied, ranging from 1.7% to 8.7%. Between the anterior longitudinal ligament as a medial landmark and the psoas muscle as a lateral landmark is the natural “safety” corridor, which is covered by the fibers of the sympathetic chain.…”

“…Javier suggests a tubular stretcher being placed behind the sympathetic chain to decrease the incidence of traction lesions. Gragnaniello demonstrated that the sympathetic trunk has to be mobilized by smooth retractor blades; even sacrifice produces only warming of the affected leg that is unnoticed by patients.…”

Factors Influencing Early Disc Height Loss Following Lateral Lumbar Interbody Fusion

“…Using a lateral approach, interbody cage placement can be conducted either from the front of the psoas muscle (oblique lumbar interbody fusion, OLIF) or through the psoas muscle (direct lateral interbody fusion, DLIF) [8,9]. Both techniques facilitate the insertion of a wide-bodied interbody cage via a minimally invasive approach.…”