Resection Of Posterior Elements Research Articles

Biomechanical effects of laminectomies in the human lumbar spine: a finite element study

Previous studies have analyzed the effect of laminectomy on intervertebral disc (IVD), facet-joint-forces (FJF), and range of motion (ROM), while only two have specifically reported stresses at the pars interarticularis (PI) with posterior element resection. These studies have been performed utilizing a single subject, questioning their applications to a broader population. We investigate the effect of graded PI resection in a three-dimensional manner on PI stress to provide surgical guidelines for avoidance of iatrogenic instability following lumbar laminectomy. Additionally, quantified FJF and IVD stresses can provide further insight into the development of adjacent segment disease. Biomechanical finite element (FE) method investigation of the lumbar spine. FE models of the lumbar spine of three subjects were created using the open-source finite element software, FEBio. Single-level laminectomy, two-level laminectomy, and ventral-to-dorsal PI resection simulations were performed with varying degrees of PI resection from 0% to 75% of the native PI. These models were taken through cardinal ROM under standard loading conditions and PI stresses, FJF, IVD stresses, and ROM were analyzed. The three types of laminectomy simulated in this study showed a nonlinear increase in PI stress with increased bone resection. Axial rotation generated the most stress at the PI followed by flexion, extension and lateral bending. At 75% bone resection all three types of laminectomy produced PI stresses that were near the ultimate strength of human cortical bone during axial rotation. FJF decreased with increased bone resection for the three laminectomies simulated. This was most notable in axial rotation followed by extension and lateral bending. IVD stresses varied greatly between the nonsurgical models and likewise the effect of laminectomy on IVD stresses varied between subjects. ROM was mostly unaffected by the laminectomies performed in this study. Regarding the risk of iatrogenic spondylolisthesis, the combined results are sufficient evidence to suggest surgeons should be particularly cautious when PI resection exceeds 50% bone resection for all laminectomies included in this study. Lastly, the effects seen in FJF and IVD stresses indicate the degree to which the remainder of the spine must experience compensatory biomechanical changes as a result of the surgical intervention.

Two-Stage Procedure Planning for the Surgical Correction of Severe Congenital Kyphosis: A Technical Case Report

Congenital kyphosis is a less common spinal malformation, which can progress and cause neurological deficits. The treatment of severe cases is complicated. There are several techniques of surgical intervention for the correction of kyphosis, but the selection of surgical methods is entirely dependent on the patient’s condition. This article reports a 14-year-old girl with severe congenital kyphosis, who underwent hemiepiphysiodesis at age 2. Last year, her neurological deterioration began and led to paraplegia over a couple of months. To treat her, we performed 2-stage multi-level vertebral column resection (Schwab type 6). First, she underwent anterior T12-L1-L2 complete corpectomy and cord decompression. Then, the resection of posterior elements from T12 to L2 and posterior fusion with instrumentation from T8 to L5 were performed. However, concerning this kind of severe deformity, we suggest using 3D planning, which facilitates the operation.

A Mouse Intervertebral Disc Degeneration Model by Surgically Induced Instability.

An experimental study to develop a mouse model of lumbar intervertebral disc degeneration (IDD). The aim of this study was to develop a mouse lumbar IDD model using surgically induced instability and to compare the findings of this model to those in human IDD. Previously, various kinds of inducers have been used to reproduce IDD in experimental animals; however, there is yet no standard mouse lumbar IDD model without direct injury to intervertebral disc. A total number of 59 C57BL/6J male mice at 8 weeks old were used. Instability of lumbar spine was induced by surgical resection of posterior elements, including facet joints, supra- and interspinous ligaments. We then analyzed time course changes in radiographical (n = 17) and histological analyses (n = 42), and compared these findings with those in human IDD. Radiographical analyses showed that the disc height began to decrease in the first 2 weeks after the surgery, and the decrease continued throughout 12 weeks. Bone spurs at the vertebral rims were observed in the late stage of 8 and 12 weeks after the surgery. Histological analyses showed that the disorder of the anterior anulus fibrosus (AF) was initially obvious, followed by posterior shift and degeneration of the nucleus pulposus (NP). Proteoglycan detected in inner layer of AF and periphery of NP was decreased after 8 weeks. Immunohistochemistry displayed the increase of type I and X collagen, and matrix metalloproteinase 13 in the anterior AF. Surgical resection of posterior elements of mouse lumbar spine resulted in reproducible IDD. Because the present procedure does not employ direct injury to intervertebral disc and the radiological and histological findings are compatible with those in human IDD, it may contribute to further understanding of the native pathophysiology of IDD in future. N/A.

SRS-Schwab Grade 4 osteotomy for congenital thoracolumbar kyphosis: a minimum of 2 years follow-up study.

Several osteotomy techniques including pedicle subtraction osteotomy and vertebral column resection have been employed in the correction of congenital kyphosis (CK) and satisfying outcomes have been demonstrated. However, the Scoliosis Research Society (SRS)-Schwab Grade 4 osteotomy, defined as resection of posterior elements, partial vertebral body, and superior adjacent disc, is rarely reported in the treatment of CK. The present study aimed to evaluate the efficiency and safety of SRS-Schwab Grade 4 osteotomy in patients with CK, and to propose its optimal indication. This is a retrospective analysis of clinical and radiographic outcomes of patients with CK undergoing SRS-Schwab Grade 4 osteotomy. Patients with thoracolumbar CK undergoing SRS-Schwab Grade 4 osteotomy from January 2010 to May 2015 followed up for at least 2 years were retrospectively reviewed. The thoracic kyphosis, lumbar lordosis, segmental kyphosis (SK), sagittal vertical axis (SVA), pelvic incidence, pelvic tilt, and sacral slope were measured on lateral spinal x-rays. Patients were required to fulfill the SRS-22 questionnaire at preoperation and the last follow-up. The sagittal spinal-pelvic parameters were assessed at preoperation, postoperation, and last follow-up. The comparison between preoperation and postoperation was performed by paired samples t test. A total of 38 patients with CK (17 male and 21 female) with an average age of 16.5±9.9 years were included. The mean operating time was 242.7±88.1 minutes and blood loss was 634.5±177.8 mL. The mean follow-up was 38.8±20.3 months. The SK was 49.5±11.7° at preoperation, 6.8±7.4° at postoperation (p<.001), and 8.0±8.1° at the last follow-up. No significant correction loss during follow-up was found in SK (p=.125). The SVA was improved from -36.0±18.3 mm at preoperation to 3.7±17.8 mm at postoperation (p<.001), and the correction was well maintained during follow-up (p=.113). Compared with preoperation, the mean postoperative scores of each domains of SRS-22 questionnaire improved at different levels. Intraoperative complications included one case with incidental dural tear and another with transient root injury. Proximal junctional kyphosis occurred in three patients at 6 months after operation and remained stable during the follow-up. At the last follow-up, all patients were identified to have achieved solid bony fusion. The SRS-Schwab Grade 4 osteotomy, if selected appropriately, could provide satisfying correction of congenital kyphosis. The correction could be well maintained during the longitudinal follow-up.

Sagittal Plane Correction Using Lateral Transpsoas Approach: Effect of Cage Angulation and Surgical Technique on Segmental Lordosis

IntroductionLordotic cage insertion through lateral transpsoas approach is being used increasingly for restoration of sagittal alignment. However, the degree of correction achieved by varying cage angle as well as ALL release and posterior element resection is not well defined. The objective of this study is to determine the degree of segmental correction which could be achieved through lateral transpsoas approach by varying cage angle as well as adding anterior longitudinal ligament (ALL) release and posterior element resection. Material and MethodsThirteen human cadaveric lumbar motion segments between L1 and L5 were dissected into single motion segments. Segmental angles and disk heights were measured under both 50N and 500N loads under the following conditions: Intact specimen, discectomy (collapsed disk simulation), insertion of parallel cage, 10° cage, 30° cage with ALL release, 30° cage with ALL release and spinous process (SP) resection, 30° cage with ALL release, SP resection, facetectomy and compression with pedicle screws. ResultsSegmental lordosis was not increased by with either parallel or 10° cages as compared with intact disks, and contributed small amounts of lordosis when compared with the collapsed disk condition. Placement of 30° cages with ALL release increased segmental lordosis by 10.5°. Adding SP resection increased lordosis to 12.39°. Facetectomy and compression with pedicle screws further increased gains in lordosis to 26.4° in the 50N group and 25.8° in the 500N group. Neither group experienced a decrease in either anterior or posterior disk height. ConclusionInsertion of parallel or 10° cage has little effect on lordosis. 30° cage insertion and ALL release resulted in an increase of lordosis by ~10.5°. The addition of SP resection and facetectomy allowed increases in correction of up to 26.4°. No interventions resulted in decrease in either anterior or posterior disk height suggesting gains were achieved without causing foraminal stenosis.

Modification in Surgical Technique for Posterior Vertebral Column Resection

Introduction Surgical treatment of severe and rigid spinal deformities is usually difficult and challenging to perform. The goal of surgical treatment is to obtain a satisfactory balance both in sagittal and coronal planes. In rigid deformities, the osteotomies are usually insufficient; vertebral column resection is the only option of treatment. To reduce the operation time and complications, a single stage, posterior vertebral column resection (PVCR) is defined by Suk et al. It enables rotational and translational correction of spinal column and provides an opportunity for manipulation of anterior and posterior column simultaneously. In the original PVCR, posterior elements of resection side were removed first and then the anterior part removed and correction was performed. The authors decided to make a modification in PVCR as performing the posterior total laminectomy, facetectomy, and pediclectomy after vertebral body resection. This method has two major advantages; minimization of the blood loss from epidural veins after laminectomy and protection of the neural elements from direct injury during vertebral body resection. Patients and Methods A total of 11 patients between the age of 3 and 63 years, diagnosed with severe spinal deformity with limited flexibility, who underwent modified PVCR were reviewed. The average follow-up was 2 years (range, 5 months–3 years). There were six female and five male patients with a mean age of 18 years. Severe congenital scoliosis was found in seven patients, congenital kyphosis in two patients, neurofibromatosis in one patient, and posttraumatic kyphosis in one patient. The surgery consisted of temporary fixation of vertebral column, resection of vertebral body first then resection of posterior elements, followed by deformity correction and fusion. Results The mean estimated blood loss was 1,072 mL (range, 350–2,000 mL). Overall, 39.45% (range, 33–50%) of total blood loss occurred after vertebral body resection, 60.91% (range, 50–67%) occurred after posterior elements removal. The ratio of estimated blood loss to estimated body blood volume was 26% (range, 19–52%). The deformity correction was 60% in the coronal plane. No neurological complications were encountered. Conclusion The PVCR is a complicated, technically demanding procedure with possible risks for major complications. All correction attempts must be performed under direct inspection, palpation of tension in the spinal cord by a highly experienced surgeon. Spinal cord neuromonitoring is a must to prevent neurological injuries. The authors modified the original technique defined by Suk and performed by various surgeons. The authors believe that making vertebral body resection before laminectomy would decrease the blood loss and protect the spinal cord. The validity of this new modified technique should be demonstrated in a prospective, randomized, controlled study with a larger patient population allowing comparison of age-matched subgroups.

A Radiographic Assessment of the Ability of the Extreme Lateral Interbody Fusion Procedure to Indirectly Decompress the Neural Elements

Prospective nonrandomized clinical study on the decompressive effect of the extreme lateral interbody fusion (XLIF) procedure. This study evaluates the results of interbody distraction from a lateral retroperitoneal approach for the treatment of lumbar degenerative conditions inclusive of central and/or lateral stenosis. Traditional treatment for symptomatic lumbar stenosis has been by direct posterior decompression (i.e., removal of ligamentum flavum, laminotomy/laminectomy, facetectomy, as needed). Stenotic symptoms may also be alleviated indirectly, through correction of intervertebral and foraminal height and correction of spinal alignment. Anterior-only spinal procedures rely on this indirect decompression when used in patients with radicular symptoms. Consecutive patients presenting with degenerative conditions that included concomitant lumbar stenosis were consented and treated via stand-alone XLIF. Pre- and postoperative radiographic measurements were made from plain lateral radiographs and sagittal and axial magnetic resonance imaging views by an independent radiologist using medical imaging software. Measurements included disc height, foraminal height, foraminal area, and canal diameter. In all, 7 male and 14 female patients (mean age, 67.6 years; range, 40-83) underwent XLIF at 43 lumbar levels in an average operative time of 47 minutes and with an average 23 mL estimated blood loss per level. There were no intraoperative complications. Mean hospital stay was 29.5 hours. Transient postoperative psoas weakness occurred in 3 (14.3%) of the cases. Substantial dimensional improvement was evidenced in all radiographic parameters, with increases of 41.9% in average disc height, 13.5% in foraminal height, 24.7% in foraminal area, and 33.1% in central canal diameter. Two patients (9.5%) required a second procedure for additional posterior decompression and/or instrumentation. The XLIF procedure provides the necessary decompression for the treatment of central and/orlateral stenosis in a minimally disruptive way, avoiding, in most cases, the need for the direct resection of posterior elements and associated morbidities. Indirect decompression may be limited in cases of congenital stenosis and/or locked facets. Its effect may also be reduced by postoperative subsidence and/or loss of correction.

Technical Advances in Minimally Invasive Surgery

Literature review, technique overview, prospective and retrospective data analysis. To review current minimally invasive surgery (MIS) methods of decompression for lumbar spinal stenosis and present a decompression technique using a flexible microblade shaver system. Several MIS decompression techniques for stenosis have been developed to minimize damage to soft tissues and reduce the amount of posterior element resection. Decompression using linearly configured instruments may not be able to adequately address stenosis in the neural foramen. A flexible microblade shaver system is able to traverse the foramen, removing bone and ligament, using a ventral to dorsal approach, rather than medial to lateral. This enables it to effectively decompress the lateral recess and neural foramen while sparing posterior structures. Brief literature review of current MIS decompression techniques is presented. MIS decompression using a flexible microblade shaver system is described with 1 year outcomes from a small pilot study and a retrospective chart review at 2 centers. A small postmarket pilot study (n = 9) with 1 year results showed positive patient outcomes using Visual Analog Scale (decrease by 73%), Oswestry Disability Index(50% improvement), Zurich Claudication Questionnaire physical function and symptom severity (improved by 72% and 31%, respectively), and Short-Form 36 (SF-36) Physical Component Score (36% improvement). Sixty-seven patients from a retrospective chart review at 2 centers had an average of 2 levels per patient decompressed using a flexible microblade shaver system. No patient has returned for additional surgery and there have been no cases of neurologic impairment. Current decompression techniques may result in inadequate decompression of the neural foramen or excessive resection of the facet joint. MIS decompression using a flexible microblade shaver system represents a way to perform an effective, facet-preserving decompression for patients with lumbar spinal stenosis.

Treatment of symptomatic spondyloptosis in an adult previously treated with in situ fusion and instrumentation by L5 vertebrectomy and L4–S1 instrumented reduction

One traditional treatment for spondylolisthesis is fusion. However, for high-grade spondylolisthesis and spondyloptosis, posterior fusion has had high rates of nonunion, progression, and persistent physical deformity. Thus, some surgeons have recommended reduction and instrumentation. One such technique (Gaines procedure) entails a two-stage procedure: L5 vertebrectomy anteriorly, followed by resection of the L5 posterior elements and instrumented reduction of L4 onto S1. However, to our knowledge, there is no report of reversing the fusion and deformity reduction in a symptomatic patient with previous solid fusion of the spondyloptosis at L5-S1. To present the first reported revision via the Gaines procedure for failed fusion secondary to spondyloptosis. Patient report. A 24-year-old woman, who had undergone multiple procedures for L5-S1 spondylolisthesis and a final fusion and instrumentation attempt, presented with continued urinary retention, leg and back pain, and inability to stand. She subsequently underwent posterior hardware removal, followed by anterior L5 vertebral body resection. In the second stage, she had posterior osteotomy of the previous L5-S1 fusion, resection of the posterior elements of L5, and reduction and instrumentation of L4 to S1. At the 2-year follow-up, she had full resolution of symptoms, full return of motor strength, and resolution of urinary retention. The Gaines procedure has been performed successfully in patients without previous fusions at the level of spondylolisthesis or spondyloptosis. Patients for whom the traditional posterior fusion fails still may be candidates for this procedure, albeit at increased risk of neurologic injury.

Unilateral Lumbar Fusion

Unilateral fusion of the lumbar spine is rarely necessary or indicated. However, in patients with a "far-out syndrome" requiring decompression or in cases where unilateral posterior element resection is necessary for any reason, it may be both necessary and indicated. This unilateral destabilization effectively removes one leg of the tripod, rendering that intervertebral joint potentially unstable. The charts and radiographs of 13 patients (seven men, six women) with an average age of 60 years (range, 25 to 76) who underwent unilateral fusion were retrospectively reviewed. Follow-up time ranged from 12 1/2 to 2 years with a median follow-up of 8 years. Eleven of the fusions were at one level, and two were at two levels. Seven patients had a far-out syndrome secondary to degenerative scoliosis; four were secondary to spondylolisthesis. Two patients had an osteoid osteoma involving a pedicle. A paraspinal approach was used in the majority of patients. Autologous bone graft was used in all patients. Unilateral pedicle screw fixation was used in the last patient in the series. The fusion rate was 85% (11/13). Three patients were smokers, two of whom developed pseudarthrosis. Disc space height did not appear to affect fusion rate. There was no progression of slip noted in any of the patients. One complication was noted in this group: a moderate postoperative infection, which cleared spontaneously.

The Surgical Treatment of Spondylolisthesis by Posterior Element Resection

The Surgical Treatment of Spondylolisthesis by Posterior Element Resection