Anterior to psoas fusion of the lumbar spine.

Lateral interbody cages have proven useful in lumbar fusion surgery. Spanning both lateral cortical rims while sparing the anterior longitudinal ligament, they restore disc height, improve coronal balance and add stability. The standard approach to their insertion is 90 degrees lateral transpsoas which is bloodless compared to other techniques of interbody cage insertion but requires neuro-monitoring and at L4/5 can be difficult because of iliac crest obstruction or an anterior plexus position. The oblique muscle-splitting approach with the patient in a lateral position, remains retroperitoneal, and on the left side enters the disc space through a window between psoas and the common iliac vein. Reports of this approach are few and none previously have described how to use the large lateral-type cages so effective at restoring spinal alignment. In this video we demonstrate our technique of anterior to psoas fusion of the lumbar spine with a retroperitoneal approach and gentle retraction of the psoas muscle. The video can be found here: http://youtu.be/OS2vNcX9JMA.

Clinical outcome and fusion rates after the first 30 extreme lateral interbody fusions.

INTRODUCTION: The lateral transpsoas approach for lumbar interbody fusion (XLIF) is gaining popularity. Studies examining a surgeon's early experience are rare. We aim to report treatment, complication, clinical, and radiographic outcomes in an early series of patients. METHODS: Prospective data from the first thirty patients treated with XLIF by a single surgeon was reviewed. Outcome measures included pain, disability, and quality of life assessment. Radiographic assessment of fusion was performed by computed tomography. RESULTS: Average follow-up was 11.5 months, operative time was 60 minutes per level and blood loss was 50 mL. Complications were observed: clinical subsidence, cage breakage upon insertion, new postoperative motor deficit and bowel injury. Approach side-effects were radiographic subsidence and anterior thigh sensory changes. Two patients required reoperation; microforaminotomy and pedicle screw fixation respectively. VAS back and leg pain decreased 63% and 56%, respectively. ODI improved 41.2% with 51.3% and 8.1% improvements in PCS and MCS. Complete fusion (last follow-up) was observed in 85%. CONCLUSION: The XLIF approach provides superior treatment, clinical outcomes and fusion rates compared to conventional surgical approaches with lowered complication rates. Mentor supervision for early cases and strict adherence to the surgical technique including neuromonitoring is essential.

Maintenance of Segmental Lordosis and Disk Height in Stand-alone and Instrumented Extreme Lateral Interbody Fusion (XLIF).

STUDY DESIGN: A prospective single-surgeon nonrandomized clinical study. OBJECTIVE: To evaluate the radiographic and clinical outcomes, by fixation type, in extreme lateral interbody fusion (XLIF) patients and provide an algorithm for determining patients suitable for stand-alone XLIF. SUMMARY OF BACKGROUND DATA: XLIF may be supplemented with pedicle screw fixation, however, since stabilizing structures remain intact, it is suggested that stand-alone XLIF can be used for certain indications. This eliminates the associated morbidity, though subsidence rates may be elevated, potentially minimizing the clinical benefits. MATERIALS AND METHODS: A fixation algorithm was developed after evaluation of patient outcomes from the surgeon's first 30 cases. This algorithm was used prospectively for 40 subsequent patients to determine the requirement for supplemental fixation. Preoperative, postoperative, and 12-month follow-up computed tomography scans were measured for segmental and global lumbar lordosis and posterior disk height. Clinical outcome measures included back and leg pain (visual analogue scale), Oswestry Disability Index (ODI), and SF-36 physical and mental component scores (PCS and MCS). RESULTS: Preoperatively to 12-month follow-up there were increases in segmental lordosis (7.9-9.4 degrees, P=0.0497), lumbar lordosis (48.8-55.2 degrees, P=0.0328), and disk height (3.7-5.5 mm, P=0.0018); there were also improvements in back (58.6%) and leg pain (60.0%), ODI (44.4%), PCS (56.7%), and MCS (16.1%) for stand-alone XLIF. For instrumented XLIF, segmental lordosis (7.6-10.5 degrees, P=0.0120) and disk height (3.5-5.6 mm, P<0.001) increased, while lumbar lordosis decreased (51.1-45.8 degrees, P=0.2560). Back (49.8%) and leg pain (30.8%), ODI (32.3%), PCS (37.4%), and MCS (2.0%) were all improved. Subsidence occurred in 3 (7.5%) stand-alone patients. CONCLUSIONS: The XLIF treatment fixation algorithm provided a clinical pathway to select suitable patients for stand-alone XLIF. These patients achieved positive clinical outcomes, satisfactory fusion rates, with sustained correction of lordosis and restoration of disk height.

Choice of Approach Does Not Affect Clinical and Radiologic Outcomes: A Comparative Cohort of Patients Having Anterior Lumbar Interbody Fusion and Patients Having Lateral Lumbar Interbody Fusion at 24 Months.

STUDY DESIGN: Retrospective analysis of prospectively collected registry data. OBJECTIVE: This study aimed to compare the clinical and radiologic outcomes between comparative cohorts of patients having anterior lumbar interbody fusion (ALIF) and patients having lateral lumbar interbody fusion (LLIF). METHODS: Ninety consecutive patients were treated by a single surgeon with either ALIF (n = 50) or LLIF (n = 40). Inclusion criteria were patients age 45 to 70 years with degenerative disk disease or grade 1 to 2 spondylolisthesis and single-level pathology from L1 to S1. Patient-reported outcome measures included pain (visual analog scale), disability (Oswestry Disability Index [ODI]), and quality of life (Short Form 36 physical component score [PCS] and mental component scores [MCS]). Assessment of fusion and measurement of lordosis and posterior disk height were performed on computed tomography scans. RESULTS: At 24 months, patients having ALIF had significant improvements in back (64%) and leg (65%) pain and ODI (60%), PCS (44%), and MCS (26%; p < 0.05) scores. Patients having LLIF had significant improvements in back (56%) and leg (57%) pain and ODI (52%), PCS (48%), and MCS (12%; p < 0.05) scores. Fourteen complications occurred in the ALIF group, and in the LLIF group, there were 17 complications (p > 0.05). The fusion rate was 100% for ALIF and 95% for LLIF (p = 0.1948). ALIF added ∼6 degrees of lordosis and 3 mm of height, primarily measured at L5-S1, and LLIF added ∼3 degrees of lordosis and 2 mm of height between L1 to L5. Mean follow-up was 34.1 months. CONCLUSIONS: In comparative cohorts of patients having ALIF and patients having LLIF at 24 months postoperatively, there were no significant differences in clinical outcomes, complication rates, or fusion rates.

Complex Spine Pathology Simulator: An Innovative Tool for Advanced Spine Surgery Training.

Background Technical advancements in spine surgery have made possible the treatment of increasingly complex pathologies with less morbidity. Time constraints in surgeons' training have made it necessary to develop new training models for spine pathology. Objective To describe the application of a novel compound, Stratathane resin ST-504 derived polymer (SRSDP), that can be injected at different spinal target locations to mimic spinal epidural, subdural extra-axial, and intra-axial pathologies for the use in advanced surgical training. Material and Methods Fresh-frozen thoracolumbar and cervical spine segments of human and sheep cadavers were used to study the model. SRSDP is initially liquid after mixing, allowing it to be injected into target areas where it expands and solidifies, mimicking the entire spectrum of spinal pathologies. Results Different polymer concentrations have been codified to vary adhesiveness, texture, spread capability, deformability, and radiologic visibility. Polymer injection was performed under fluoroscopic guidance through pathology-specific injection sites that avoided compromising the surgical approach for subsequent excision of the artificial lesion. Inflation of a balloon catheter of the desired size was used to displace stiff cadaveric neurovascular structures to mimic pathology-related mass effect. Conclusion The traditional cadaveric training models principally only allow surgeons to practice the surgical approach. The complex spine pathology simulator is a novel educational tool that in a user-friendly, low-cost fashion allows trainees to practice advanced technical skills in the removal of complex spine pathology, potentially shortening some of the aspects of the learning curve of operative skills that may otherwise take many years to acquire.

Assessment and classification of subsidence after lateral interbody fusion using serial computed tomography.

OBJECT Intervertebral cage settling during bone remodeling after lumbar lateral interbody fusion (LIF) is a common occurrence during the normal healing process. Progression of this settling with endplate collapse is defined as subsidence. The purposes of this study were to 1) assess the rate of subsidence after minimally invasive (MIS) LIF by CT, 2) distinguish between early cage subsidence (ECS) and delayed cage subsidence (DCS), 3) propose a descriptive method for classifying the types of subsidence, and 4) discuss techniques for mitigating the risk of subsidence after MIS LIF. METHODS A total of 128 consecutive patients (with 178 treated levels in total) underwent MIS LIF performed by a single surgeon. The subsidence was deemed to be ECS if it was evident on postoperative Day 2 CT images and was therefore the result of an intraoperative vertebral endplate injury and deemed DCS if it was detected on subsequent CT scans (≥ 6 months postoperatively). Endplate breaches were categorized as caudal (superior endplate) and/or cranial (inferior endplate), and as ipsilateral, contralateral, or bilateral with respect to the side of cage insertion. Subsidence seen in CT images (radiographic subsidence) was measured from the vertebral endplate to the caudal or cranial margin of the cage (in millimeters). Patient-reported outcome measures included visual analog scale, Oswestry Disability Index, and 36-Item Short Form Health Survey physical and mental component summary scores. RESULTS Four patients had ECS in a total of 4 levels. The radiographic subsidence (DCS) rates were 10% (13 of 128 patients) and 8% (14 of 178 levels), with 3% of patients (4 of 128) exhibiting clinical subsidence. In the DCS levels, 3 types of subsidence were evident on coronal and sagittal CT scans: Type 1, caudal contralateral, in 14% (2 of 14), Type 2, caudal bilateral with anterior cage tilt, in 64% (9 of 14), and Type 3, both endplates bilaterally, in 21% (3 of 14). The mean subsidence in the DCS levels was 3.2 mm. There was no significant difference between the numbers of patients in the subsidence (DCS) and no-subsidence groups who received clinical benefit from the surgical procedure, based on the minimum clinically important difference (p > 0.05). There was a significant difference between the fusion rates at 6 months (p = 0.0195); however, by 12 months, the difference was not significant (p = 0.2049). CONCLUSIONS The authors distinguished between ECS and DCS. Radiographic subsidence (DCS) was categorized using descriptors for the location and severity of the subsidence. Neither interbody fusion rates nor clinical outcomes were affected by radiographic subsidence. To protect patients from subsidence after MIS LIF, the surgeon needs to take care with the caudal endplate during cage insertion. If a caudal bilateral (Type 2) endplate breach is detected, supplemental posterior fixation to arrest progression and facilitate fusion is recommended.

Lateral extent and ventral laminar attachments of the lumbar ligamentum flavum: cadaveric study.

BACKGROUND CONTEXT: Cadaveric descriptions of the deep layer of the lumbar ligamentum flavum (LF), extending between contiguous borders of adjacent laminae and into the lateral spinal canal region are limited. PURPOSE: To provide detailed descriptions of the lumbar LF. STUDY DESIGN: Cadaveric dissection. METHODS: The deep ligamentum flava of 14 formalin-fixed human cadaver lumbar spines (140 levels) were examined to assess their laminar attachments and lateral extents in relation to the intervertebral foramen. RESULTS: The variable attachment of the deep layer of the LF with respect to the cephalad and caudad laminae was identified and described. At each successive caudal level of the lumbar spine, the deep layer appeared to become a more prominent feature of the posterior vertebral column, lining more of the laminae to which it is attached and encroaching further into the posteroinferior region of the intervertebral foramen at its lateral margins. CONCLUSIONS: We describe our observations of the deep LF in the human lumbar spine. These observations have clinical relevance for the interpretation of radiologic imaging and the performance of adequate decompression in the setting of spinal stenosis.

Early postoperative dislocation of the anterior Maverick lumbar disc prosthesis: report of 2 cases.

The authors report on 2 cases of anterior dislocation of the Maverick lumbar disc prosthesis, both occurring in the early postoperative period. These cases developed after experience with more than 50 uneventful cases and were therefore thought to be unrelated to the surgeon's learning curve. No similar complications have been previously reported. The anterior Maverick device has a ball-and-socket design made of cobalt-chromium-molybdenum metal plates covered with hydroxyapatite. The superior and inferior endplates have keels to resist translation forces. The patient in Case 1 was a 52-year-old man with severe L4-5 discogenic pain; and in Case 2, a 42-year-old woman with disabling L4-5 and L5-S1 discogenic back pain. Both patients were without medical comorbidities and were nonsmokers with no risk factors for osteoporosis. Both had undergone uneventful retroperitoneal approaches performed by a vascular access surgeon. Computed tomography studies on postoperative Day 2 confirmed excellent prosthesis placement. Initial recoveries were uneventful. Two weeks postoperatively, after stretching (extension or hyperextension) in bed at home, each patient suffered the sudden onset of severe abdominal pain with anterior dislocation of the Maverick prosthesis. The patients were returned to the operating room and underwent surgery performed by the same spinal and vascular surgeons. Removal of the Maverick prosthesis and anterior interbody fusion with a separate cage and plate were performed. Both patients had recovered well with good clinical and radiological recovery at the 6- and 12-month follow-ups. Possible causes of the anterior dislocation of the Maverick prosthesis include the following: 1) surgeon error: In both cases the keel cuts were neat, and early postoperative CT confirmed good placement of the prosthesis; 2) equipment problem: The keel cuts may have been too large because the cutters were worn, which led to an inadequate press fit of the implants; 3) prosthesis fault: Both plates of the dislocated implants looked normal and manufacturer analysis reported no fault; 4) patient factors: Both dislocations happened early in the postoperative period, after hyperextension of the spine while the patient was supine in bed. Bracing would not have reduced hyperextension. Dislocation of a lumbar spinal implant represents a life-threatening complication and should therefore be considered and recognized early. Radiographic and CT studies of both the lumbar spine (for prosthesis) and the abdomen (for hematoma) should be performed, as should CT angiography (for vessel damage or occlusion). Any anterior lumbar revision surgery is hazardous, and it is strongly advisable to have a vascular surgeon scrubbed. In cases of dislocation or extrusion of a lumbar interbody prosthesis, the salvage revision strategy is fusing the segment via the same anterior approach. Surgeons should be aware of the risk of anterior dislocation of the Maverick prosthesis. Keel cutters should be regularly checked for sharpness, as they may be implicated in the loosening of implants. Patients and their physical therapists should also avoid lumbar hyperextension in the early postoperative period.

Results of a prospective randomized study comparing a novel retractor with a Caspar retractor in anterior cervical surgery.

BACKGROUND: Retraction injury might explain the soft tissue complications seen after anterior cervical surgery. A novel retractor system (Seex retractor system [SRS]) that uses a principle of bone fixation with rotation has been shown to reduce retraction pressure in a cadaveric model of anterior cervical decompression and fusion. OBJECTIVE: To compare the conventional Cloward-style retractor (CRS) with the SRS in a prospective randomized clinical trial. METHODS: After ethics and study registration (ACTRN 12608000430336), eligible patients were randomized to either the CRS or SRS before 1- or 2-level anterior cervical decompression and fusion. The pressure beneath the medial retractor blade was recorded with a thin pressure transducer strip. Postoperative sore throat, dysphagia, and dysphonia were assessed after 1, 7, and 28 days. RESULTS: Twenty-six patients were randomized. There were no serious complications. Complication rates were low with a trend favoring SRS that was not statistically different. Average retraction pressure with SRS was 1.9 mm Hg and with CRS was 5.6 mm Hg (P < .001 on F test; P = .002 on 2-tailed t test). Mean average peak retraction pressure with the SRS was 3.4 mm Hg and with the CRS was 20 mm Hg (P < .001 on F test; P = .005 on 2-tailed t test). CONCLUSION: The new retractor is safe, and statistically similar complication rates were observed with the 2 systems. The SRS generated significantly less retraction pressure compared with the CRS. This difference can be explained by the different principles governing the function of these retractors. Bone fixation gives stability and rotation reduces tissue pressure, both desirable in a retractor.

An anterior cervical retractor utilizing a novel principle.

The alarmingly high soft-tissue complication rates after anterior cervical surgery suggests that the design of current retractors is inadequate. A review of retractor design and consideration of new designs is worthwhile. The author reviewed the literature and the 7 described devices (Cloward, Caspar, Thompson-Farley, Tresserras, Ozer, Takayasu, and Oh devices). With the exception of Cloward/Caspar and Thomson-Farley systems, the author's search of the literature failed to disclose any independent review or investigations of the other retractors, suggesting that the use of these devices is limited. The Cloward/Caspar-style retractors depend for stability on small teeth at the ends of the blades that impale and stretch the longus colli muscle. For stability this self-retaining design requires equal tissue counterpressure. These devices are thus ill suited for a wound with substantially greater pressure from the medial structures and are prone to migration. The Thomson-Farley type of systems use arms with mechanical joints fixed to a table-mounted frame. The releasable joints allow adjustability and independent relaxation. Their limitations include bulk causing obstruction to the surgeons and radiographs, increased setup time, and ease with which excessive force can be applied. The author describes a new anterior cervical retractor that is based on a novel principle. The principle is that bone fixation can be used to provide the retractor blade an axis of rotation inside the wound. This gives improved retractor blade stability with the mechanical advantage of a lever. The stable rotation produced allows adjustable retraction and tissue relaxation without compromise in stability. To the author's knowledge, there are no previously described retractors with this ability. The system consists of a small 2-piece sliding frame fixed to the spine with the distraction screws. Bone fixation is preferable to sharp teeth and longus colli dissection because it works better and heals without scarring. Surgery is carried out through the frame, which slides during distraction. Independent retractor blades are attached to the sides of the frame, which provides a stable craniocaudal axis inside the wound. The blades rotate to provide retraction or relaxation as required. Intermittent relaxation of tissues under retractors has been shown to be beneficial. Another advantage, compared with systems that maintain wounds with vertical sides, is the ease with which an oblique approach can be used. The mechanical advantage has 3 benefits. First, bulky external mechanisms for retraction are avoided, which improves access. Second, numerous blade lengths are unnecessary, reducing inventory. Third, radiolucent polymers can be used with "snap-fit" properties. The improved stability over conventional systems reduces the need for skilled assistance and avoids surgeon frustration after retraction migration. Over a 3-year period, 100 anterior cervical operations have been performed. Anecdotally, operations are quicker mainly because the retractors do not slip. Prospective clinical studies with independent evaluation are underway.

Comparison of retraction pressure between novel and conventional retractor systems--a cadaver study.

OBJECT: Sore throat, dysphagia, and dysphonia are very common after anterior cervical surgery; clinical studies show an incidence of up to 60% or more. Neural, mucosal, or muscular injuries during dissection or retraction are regularly discussed, but investigations are few. Retraction pressure causing ischemia might explain these complications. A new anterior cervical retractor system (Seex retractor) using novel principles has been introduced to surgical practice. There are isolated reported investigations comparing different anterior cervical retractors. Therefore, the purpose of this study was to measure retraction pressure on the aerodigestive tract in cadavers during the anterior surgical approach for cervical spine operations performed using either the conventional (Cloward) retractor system or the Seex retractor system. The goal was to find the significance of the shape of the retraction blades (flat vs curved) in retraction pressures. METHODS: In cadavers, the anterior cervical spine was approached surgically at the C3/4, C4/5, C5/6, and C6/7 levels. A simulated anterior discectomy procedure was performed using a Cloward retractor with curved blade, a Seex retractor with curved blade, and a Seex retractor with flat blade at each level. For each retractor application, an online pressure transducer (Tekscan pressure measurement system) is applied between the rear side of the medial retractor blade and medial soft-tissue complex. Retraction pressures are recorded twice for both retractors at each level. Average retraction pressure (ARP), average peak retraction pressure (APRP), pressure distribution along the area of retraction, pressure difference at the edge and surface of the retractor blades, pressure variation with flat and curved blades, and so on were determined and compared. One-way ANOVA and Tukey honestly significant difference tests were used for statistical evaluation. RESULTS: Forty sets of pressure recordings were made in 5 cadavers. The Cloward retractor system showed higher average contact pressure than the Seex retractor system in 36 sets. In 32 sets, the Cloward retractor system showed higher peak retraction pressure than the Seex retractor system. None of the recordings showed uniform pressure distribution over the retracted area. With the Seex retractor itself, the flat blade generated more peak retraction pressure than the curved blades in 28 sets of measurements; it was the reverse in 3 sets; and in 9 sets the peak pressure was almost the same. Higher retraction pressure was noted along the edges of retractor blades in general, and along the convexity of a curved blade. Those parallel bands corresponded to the edges of the retractor blades. The Seex retractor with a curved blade generated the lowest average retraction pressure and average peak retraction pressure (p < 0.01, ANOVA). CONCLUSIONS: Retraction pressure was found not to be uniform all over the retracted surface. Higher retraction pressure was noted along the edges of retractor blades in general, and along the convexity of a curved blade. The conventional retractor system with a curved blade generated significantly higher retraction pressures than the novel Seex retractor with a curved blade.