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Elias Dakwar, Fernando L. Vale and Juan S. Uribe

Object

The minimally invasive lateral retroperitoneal transpsoas approach is increasingly used to treat various spinal disorders. Accessing the retroperitoneal space and traversing the abdominal wall poses a risk of injury to the major nervous structures and adds significant morbidity to the procedure. Most of the current literature focuses on the anatomy of the lumbar plexus within the substance of the psoas muscle. However, there is sparse knowledge regarding the trajectory of the lumbar plexus nerves that travel along the retroperitoneum and abdominal wall muscles in relation to the lateral approach to the spine. The objective of this study is to define the anatomical trajectories of the major motor and sensory branches of the lumbar plexus that are located outside the psoas muscle.

Methods

Six adult fresh frozen cadaveric specimens were dissected and studied (12 sides). The relationship between the retroperitoneum, abdominal wall muscles, and the lumbar plexus nerves was analyzed in reference to the minimally invasive lateral retroperitoneal approach. Special attention was given to the lumbar plexus nerves that run outside of psoas muscle in the retroperitoneal cavity and within the abdominal muscle wall.

Results

The skin and muscles of the abdominal wall and the retroperitoneal cavity were dissected and analyzed with respect to the major motor and sensory branches of the lumbar plexus. The authors identified 4 nerves at risk during the lateral approach to the spine: subcostal, iliohypogastric, ilioinguinal, and lateral femoral cutaneous nerves. The anatomical trajectory of each of these nerves is described starting from the spinal column until their termination or exit from the pelvic cavity.

Conclusions

There is risk of direct injury to the main motor/sensory nerves that supply the anterior abdominal muscles during the early stages of the lateral retroperitoneal transpsoas approach while obtaining access to the retroperitoneum. There is also a risk of injury to the ilioinguinal, iliohypogastric, and lateral femoral cutaneous nerves in the retroperitoneal space where they travel obliquely during the blunt retroperitoneal dissection. Moreover, there is a latent possibility of lesioning these nerves with the retractor blades against the anterior iliac crest.

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Elias Dakwar, Amir Ahmadian and Juan S. Uribe

Object

The thoracolumbar junction (T11–L2) poses an anatomical dilemma, given the presence of the lower rib cage and the diaphragm when performing anterolateral approaches. To circumvent dealing with the diaphragm, a minimally invasive lateral extracoelomic approach has been used to approach the thoracolumbar junction by mobilizing the diaphragm anteriorly. No anatomical studies have described the attachments of the diaphragm and their surgical significance during the lateral approach to the thoracolumbar spine. The objective of this study is to describe the anatomical relationship of the diaphragm in reference to the minimally invasive lateral approach to the thoracolumbar spine and its surgical significance.

Methods

Nine adult fresh-frozen cadaveric specimens were dissected and studied (18 sides). All specimens were placed in the lateral decubitus position, similar to the surgical technique, for the dissections. The relationship between the retroperitoneum, retropleural space, diaphragm, and thoracolumbar spine was analyzed in reference to the minimally invasive lateral approach. Special attention was given to the attachments of the diaphragm and their relationship to the ribs during the early stages of the approach.

Results

All 18 sides were successfully dissected, analyzed, and photographed. The diaphragm is a musculotendinous sheet extending between the thoracic and abdominal cavities. Its attachments can be divided into 3 main categories: 1) sternal or anterior, 2) costal or lateral, and 3) lumbar or posterior. These attachments are described in detail, with specific reference to the lateral approach. When performing the minimally invasive lateral extracoelomic approach to the thoracolumbar spine, the lateral and posterior attachments must be identified and dissected to successfully mobilize the diaphragm anteriorly.

Conclusions

The diaphragm has multiple attachments that can be categorized as anterior, lateral, and posterior. In reference to the minimally invasive lateral extracoelomic approach to the thoracolumbar junction, the surgically significant attachments are primarily to the 12th rib and transverse process of L-1.

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Elias Dakwar, Rafael F. Cardona, Donald A. Smith and Juan S. Uribe

Object

The object of this study was to evaluate an alternative surgical approach to degenerative thoracolumbar deformity in adults. The authors present their early experience with the minimally invasive, lateral retroperitoneal transpsoas approach for placing interbody grafts and providing anterior column support for adult degenerative deformity.

Methods

The authors retrospectively reviewed a prospectively acquired database of all patients with adult thoracolumbar degenerative deformity treated with the minimally invasive, lateral retroperitoneal transpsoas approach at our institution. All patient data were recorded including demographics, preoperative evaluation, procedure used, postoperative follow-up, operative time, blood loss, length of hospital stay, and complications. The Oswestry Disability Index and visual analog scale (for pain) were also administered pre- and postoperatively as early outcome measures. All patients were scheduled for follow-up postoperatively at weeks 2, 6, 12, and 24, and at 1 year.

Results

The authors identified 25 patients with adult degenerative deformity who were treated using the minimally invasive, lateral retroperitoneal transpsoas approach. All patients underwent discectomy and lateral interbody graft placement for anterior column support and interbody fusion. The mean total blood loss was 53 ml per level. The average length of stay in the hospital was 6.2 days. Mean follow-up was 11 months (range 3–20 months). A mean improvement of 5.7 points on visual analog scale scores and 23.7% on the Oswestry Disability Index was observed. Perioperative complications include 1 patient with rhabdomyolysis requiring temporary hemodialysis, 1 patient with subsidence, and 1 patient with hardware failure. Three patients (12%) experienced transient postoperative anterior thigh numbness, ipsilateral to the side of approach. In this series, 20 patients (80%) were identified who had more than 6 months of follow-up and radiographic evidence of fusion. The minimally invasive, lateral retroperitoneal transpsoas approach, without the use of osteotomies, did not correct the sagittal balance in approximately one-third of the patients.

Conclusions

Degenerative scoliosis of the adult spine is secondary to asymmetrical degeneration of the discs. Surgical decompression and correction of the deformity can be performed from an anterior, posterior, or combined approach. These procedures are often associated with long operative times and a high incidence of complications. The authors' experience with the minimally invasive, lateral retroperitoneal transpsoas approach for placement of a large interbody graft for anterior column support, restoration of disc height, arthrodesis, and realignment is a feasible alternative to these procedures.

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Juan S. Uribe, Nicolas Arredondo, Elias Dakwar and Fernando L. Vale

Object

The lateral retroperitoneal transpsoas approach is being increasingly employed to treat various spinal disorders. The minimally invasive blunt retroperitoneal and transpsoas dissection poses a risk of injury to major nervous structures. The addition of electrophysiological monitoring potentially decreases the risk of injury to the lumbar plexus. With respect to the use of the direct transpsoas approach, however, there is sparse knowledge regarding the relationship between the retroperitoneum/psoas muscle and the lumbar plexus at each lumbar segment. The authors undertook this anatomical cadaveric dissection study to define the anatomical safe zones relative to the disc spaces for prevention of nerve injuries during the lateral retroperitoneal transpsoas approach.

Methods

Twenty lumbar segments were dissected and studied. The relationship between the retroperitoneum, psoas muscle, and the lumbar plexus was analyzed. The area between the anterior and posterior edges of the vertebral body (VB) was divided into 4 equal zones. Radiopaque markers were placed in each disc space at the midpoint of Zone III (middle posterior quarter). At each segment, the psoas muscle, lumbar plexus, and nerve roots were dissected. The distribution of the lumbar plexus with reference to the markers at each lumbar segment was analyzed.

Results

All parts of the lumbar plexus, including nerve roots, were found within the substance of the psoas muscle dorsal to the posterior fourth of the VB (Zone IV). No Zone III marker was posterior to any part of the lumbar plexus with the exception of the genitofemoral nerve. The genitofemoral nerve travels obliquely in the substance of the psoas muscle from its origin to its innervations. It emerges superficially and anterior from the medial border of the psoas at the L3–4 level and courses along the anterior medial fourth of the L-4 and L-5 VBs (Zone I). The nerves of the plexus that originate at the upper lumbar segments emerge from the lateral border of the psoas major and cross obliquely into the retroperitoneum in front of the quadratus lumborum and the iliacus muscles to the iliac crest.

Conclusions

With respect to prevention of direct nerve injury, the safe anatomical zones at the disc spaces from L1–2 to L3–4 are at the middle posterior quarter of the VB (midpoint of Zone III) and the safe anatomical zone at the L4–5 disc space is at the midpoint of the VB (Zone II–Zone III demarcation). There is risk of direct injury to the genitofemoral nerve in Zone II at the L2–3 space and in Zone I at the lower lumbar levels L3–4 and L4–5. There is also a potential risk of injury to the ilioinguinal, iliohypogastric, and lateral femoral cutaneous nerves in the retroperitoneal space where they travel obliquely, inferiorly, and anteriorly to the reach the iliac crest and the abdominal wall.

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Elias Dakwar, Juan S. Uribe, Tapan A. Padhya and Fernando L. Vale

Object

Delayed esophageal perforation is an uncommon but well-known complication after anterior cervical spine surgery. To the authors' knowledge there is no consensus to the optimal management of these patients in the literature.

Methods

The authors performed a retrospective review of 5 cases involving patients who were referred to their institution for the management of delayed esophageal perforations after undergoing anterior cervical spine surgery for a variety of reasons.

Results

The primary presenting symptom in all 5 patients was dysphagia. All patients initially underwent primary closure of the perforation with a sternocleidomastoid muscle flap. One patient required multiple surgeries to correct the perforation and ultimately required a free flap.

Conclusions

The authors recommend a multidisciplinary approach that involves otolaryngological surgeons as well as spine surgeons. They recommend removal of all anterior hardware and believe that it is essential to the treatment of esophageal perforations. If the patient does not have evidence of fusion at the time of presentation, then posterior cervical instrumentation is a viable alternative.

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Elias Dakwar, Jaypal Reddy, Fernando L. Vale and Juan S. Uribe

✓ Ankylosing spondylitis (AS) is a chronic, progressive inflammatory rheumatic disease involving primarily the sacroiliac joints and the axial skeleton. The main clinical features are back pain and progressive stiffness of the spine. Oligoarthritis of the hips and shoulders, enthesopathy, and anterior uveitis are common, and involvement of the heart and lungs is rare. The current understanding of the pathogenesis of this disorder is limited. Despite the strong association between human leukocyte antigen B27 (HLA-B27) and susceptibility to AS reported over the past 30 years, the exact pathogenic role of HLA-B27 in AS and other spondyloarthropathies has yet to be determined. The authors present a review of the literature pertaining to the pathogenesis of AS over the past several decades.

Ankylosing spondylitis is a polygenic disorder, with HLA-B27 playing a critical causative role in its pathogenesis. Animal studies of the immunobiology of HLA-B27 have provided significant insight into the pathogenic role of HLA-B27. The search for the antigenic peptide to support the “arthritogenic peptide” hypothesis has been disappointing. Over the past decade there has been increasing interest in the critical role of the misfolding and unfolded protein response of the heavy chain HLA-B27 in the modulation of the inflammatory response. Although there have been significant new findings in the understanding of the pathogenesis of AS, the exact mechanisms have yet to be identified. There is considerable optimism that additional susceptibility genes, predisposing factors, and regulators of the inflammatory process will be identified that will provide avenues for future treatment.

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Jaypal Reddy Sangala, Elias Dakwar, Juan Uribe and Fernando Vale

Object

The aim of this study was to review the current evidence-based nonsurgical management strategies of ankylosing spondylitis (AS) for spine surgeons. Whereas surgical management is indicated in a highly selected group, nonsurgical management is itself a useful measure for nearly all patients with AS.

Methods

The authors conducted a literature review of PubMed using relevant search words. All the articles published in English in the last 15 years were reviewed and the level of evidence provided by them was noted.

Results

Nonpharmacological treatments in the form of physical therapy and patient education have Level Ib evidence in maintaining function in AS. There is Level Ib evidence supporting the use of nonsteroidal antiinflammatory drugs (NSAIDs) and coxibs for treatment in patients with symptoms. There is not enough evidence to support the use of conventional disease-modifying antirheumatoid arthritis drugs. Tumor necrosis factor (TNF)α inhibitors (infliximab, etanercept, and adalimumab) are associated with Level Ib evidence in improving spinal pain, function, inflammatory biomarkers, and spinal inflammation detected by magnetic resonance imaging in patients in whom symptom duration has exceeded 3 months.

Conclusions

Physical therapy and patient education are useful for all patients diagnosed with AS. If symptomatic, patients are started with either a course of nonselective NSAIDs or a selective cyclooxygenase-2 inhibitor. The role of NSAIDs as a disease-modifying therapy in the treatment of AS is increasingly being understood. The central role of TNF in the pathogenesis of AS is now known, and the advent of biological treatment in the form of anti–TNFα factors has revolutionized the medical management of AS and is used in patients with axial disease whose symptoms persist despite an adequate dose of NSAIDs.

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Amir Ahmadian, Armen R. Deukmedjian, Naomi Abel, Elias Dakwar and Juan S. Uribe

Object

The minimally invasive lateral transpsoas approach has become an increasingly popular means of fusion. The most frequent complication is related to lumbar plexus nerve injuries; these can be diagnosed based on distribution of neurological deficit following the motor and/or sensory nerve injury. However, the literature has failed to provide a clinically relevant description of these complications. With accurate clinical diagnosis, spine practitioners can provide more precise prognostic and management recommendations to include observation, nerve blocks, neurodestructive procedures, medications, or surgical repair strategies. The purpose of this study was to standardize the clinical findings of lumbar plexopathies and nerve injuries associated with minimally invasive lateral retroperitoneal transpsoas lumbar fusion.

Methods

A thorough literature search of the MEDLINE database up to June 2012 was performed to identify studies that reported lumbar plexus and nerve injuries after the minimally invasive lateral retroperitoneal transpsoas approach. Included studies were assessed for described neurological deficits postoperatively. Studies that did attempt to describe nerve-related complications clinically were excluded. A clinically relevant assessment of lumbar plexus nerve injury was derived to standardize early diagnosis and outline prognostic implications.

Results

A total of 18 studies were selected with a total of 2310 patients; 304 patients were reported to have possible plexus-related complications. The incidence of documented nerve and/or root injury and abdominal paresis ranged from 0% to 3.4% and 4.2%, respectively. Motor weakness ranged from 0.7% to 33.6%. Sensory complications ranged from 0% to 75%. A lack of consistency in the descriptions of the lumbar plexopathies and/or nerve injuries as well as a lack of diagnostic paradigms was noted across studies reviewed. Sensory dermal zones were established and a standardized approach was proposed.

Conclusions

There is underreporting of postoperative lumbar plexus nerve injury and a lack of standardization of clinical findings of neural complications related to the minimally invasive lateral retroperitoneal transpsoas approach. The authors provide a diagnostic paradigm that allows for an efficient and accurate classification of postoperative lumbar plexopathies and nerve injuries.

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Armen R. Deukmedjian, Tien V. Le, Elias Dakwar, Carlos R. Martinez and Juan S. Uribe

Object

The minimally invasive lateral interbody fusion of the lumbar spine through a retroperitoneal transpsoas approach has become increasingly used. Although preoperative imaging is performed supine, the procedure is performed with the patient in the lateral decubitus position. The authors measured the changes in location of the psoas muscle, aorta, inferior vena cava (IVC), iliac vessels, and kidneys with regard to the fixed lumbar spine when moving from a supine to a lateral decubitus position.

Methods

Unenhanced lumbar MRI scans were performed using a 3T magnet in 10 skeletally mature volunteers in the supine, left lateral decubitus (LLD), and right lateral decubitus (RLD) positions. Positional changes in the aorta, IVC, iliac vessels, and kidneys were then analyzed at all lumbar levels when moving from supine to RLD and supine to LLD. Values are presented as group means.

Results

When the position was changed from supine to RLD, both the aorta and the IVC moved up to 6 mm to the right, with increased movement caudally at L3–4. The aorta was displaced 2 mm anteriorly at L1–2, and the IVC moved 3 mm anteriorly at L1–2 and L2–3 and 1 mm posteriorly at L3–4. The left kidney moved 22 mm anteriorly and 15 mm caudally, while the right kidney moved 9 mm rostrally.

When the position was changed from supine to LLD, the aorta moved 1.5 mm to the left at all levels, with very minimal anterior/posterior displacement. The IVC moved up to 10 mm to the left and 12 mm anteriorly, with increased movement rostrally at L1–2. The left kidney moved 3 mm anteriorly and 1 mm rostrally, while the right kidney moved 20 mm anteriorly and 5 mm caudally.

The bifurcation of the aorta was an average of 18 mm above the L4–5 disc space, while the convergence of the iliac veins to form the IVC was at the level of the disc space. The iliopsoas did not move in any quantifiable direction when the position was changed from supine to lateral; its shape, however, may change to become more flat or rounded. When the position was changed from supine to RLD, the right iliac vein moved posteriorly an average of 1.5 mm behind the anterior vertebral body (VB) line (a horizontal line drawn on an axial image at the anterior VB), while the other vessels stayed predominantly anterior to the disc space. When the position was changed from supine to LLD, the right iliac vein moved to a position 1.4 mm anterior to the anterior VB line. There was negligible movement of the other vessels in this position.

Conclusions

The authors showed that the aorta, IVC, and kidneys moved a significant distance away from the surgical corridor with changes in position. At the L4–5 level, a left-sided approach may be riskier because the right common iliac vein trends posteriorly and into the surgical corridor, whereas in a right-sided approach it trends anteriorly.

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Elias Dakwar, Stephen I. Rifkin, Ildemaro J. Volcan, J. Allan Goodrich and Juan S. Uribe

Minimally invasive spine surgery is increasingly used to treat various spinal pathologies with the goal of minimizing destruction of the surrounding tissues. Rhabdomyolysis (RM) is a rare but known complication of spine surgery, and acute renal failure (ARF) is in turn a potential complication of severe RM. The authors report the first known case series of RM and ARF following minimally invasive lateral spine surgery.

The authors retrospectively reviewed data in all consecutive patients who underwent a minimally invasive lateral transpsoas approach for interbody fusion with the subsequent development of RM and ARF at 2 institutions between 2006 and 2009. Demographic variables, patient home medications, preoperative laboratory values, and anesthetic used during the procedure were reviewed. All patient data were recorded including the operative procedure, patient positioning, postoperative hospital course, operative time, blood loss, creatine phosphokinase (CPK), creatinine, duration of hospital stay, and complications.

Five of 315 consecutive patients were identified with RM and ARF after undergoing minimally invasive lateral transpsoas spine surgery. There were 4 men and 1 woman with a mean age of 66 years (range 60–71 years). The mean body mass index was 31 kg/m2 and ranged from 25 to 40 kg/m2. Nineteen interbody levels had been fused, with a range of 3–6 levels per patient. The mean operative time was 420 minutes and ranged from 315 to 600 minutes. The CPK ranged from 5000 to 56,000 U/L, with a mean of 25,861 U/L. Two of the 5 patients required temporary hemodialysis, while 3 required only aggressive fluid resuscitation. The mean duration of the hospital stay was 12 days, with a range of 3–25 days

Rhabdomyolysis is a rare but known potential complication of spine surgery. The authors describe the first case series associated with the minimally invasive lateral approach. Surgeons must be aware of the possibility of postoperative RM and ARF, particularly in morbidly obese patients and in procedures associated with prolonged operative times.