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Object: There are reports that fusion is the standard treatment of choice for cases of lumbar degenerative spondylolisthesis (LDS) associated with lumbar spinal canal stenosis with a large degree of slippage. The reasons why, however, have not been clarified. On the other hand, it is known that the progress of slippage decreases and restabilization occurs over the natural course of LDS. Therefore, if minimally invasive decompression could be performed, there would be little possibility of it influencing the natural course of LDS, so it would not be necessary to include preoperative percentage slip in the criteria for the selection of fusion. This study examined the course of LDS cases more than 5 years after treatment with minimally invasive decompression to determine whether pre- and postoperative slippage and disc changes influence the clinical results., Methods: A total of 51 intervertebral segments in 51 cases with the chief complaint of radicular or cauda equina symptoms due to lumbar spinal canal stenosis were examined after prospective treatment with minimally invasive decompression for LDS. The mean age of the patients at the time of surgery was 66.7 years and the mean follow-up period was 7 years 4 months. Minimally invasive decompression was performed regardless of the degree of low-back pain or percentage slip. The outcome variables were clinical results and changes in imaging findings., Results: Over the follow-up period, postoperative percentage slip increased and disc height decreased, but the Japanese Orthopaedic Association score improved. Regardless of the preoperative percentage slip, disc height, or degree of intervertebral disc degeneration or segmental instability, the clinical results were favorable. In the high preoperative percentage slip group, low disc height group, and progressive disc degeneration group, there was little postoperative progress of slippage. In the group with a postoperative slippage increase of more than 5%, slippage increased significantly at postoperative year 2, but no significant difference was observed at the final follow-up., Conclusions: When minimally invasive decompression was performed to treat LDS, the postoperative change in slippage was no different from that during the natural course. Furthermore, regardless of the degree of preoperative slippage or intervertebral disc degeneration, the clinical results were favorable. Also, the higher the preoperative percentage slip and the more that disc degeneration progressed, the more the progress of postoperative slippage decreased. Because the postoperative progress of slippage decreased, it is believed that even after minimally invasive decompression, restabilization occurs as it would during the natural course. If minimally invasive decompression can be performed to treat LDS, it is believed that preoperative percentage slip and intervertebral disc degeneration do not have to be included in the appropriateness criteria for fusion.

Object: Spinopelvic alignment is crucial in assessing an energy-efficient posture in both normal and disease states, such as high-displacement developmental spondylolisthesis (HDDS). The overall effect in patients with HDDS who have undergone local surgical correction of lumbosacral imbalance for the global correction of spinal balance remains unclear. This paper reports the progressive spontaneous improvement of global sagittal balance following surgical correction of lumbosacral imbalance in patients with HDDS., Methods: The records of 15 patients with HDDS who underwent surgery between 2005 and 2010 were reviewed. The treatment consisted of L4-sacrum reduction and fusion via a posterior approach, resulting in complete correction of lumbosacral kyphosis. Preoperative, 6-month postoperative, and final follow-up postoperative angular measurements were taken from full-spine lateral radiographs obtained with the patient in a standard standing position. Radiographic measurements included pelvic incidence, sacral slope, lumbar lordosis, and thoracic kyphosis. The degree of lumbosacral kyphosis was evaluated by the lumbosacral angle. Because of the small number of patients, nonparametric tests were considered for data analysis., Results: Preoperative lumbosacral kyphosis and L-5 anterior slip were corrected by instrumentation. Transient neurological complications were noted in 5 patients. Statistical analysis showed a significant increase of thoracic kyphosis on 6-month postoperative and final follow-up radiographs (p < 0.001). A statistically significant decrease of lumbar lordosis was noted between preoperative and 6-month control radiographs (p < 0.001) and between preoperative and final follow-up radiographs (p < 0.001)., Conclusions: Based on the authors' observations, this technique resulted in an effective reduction of L-5 anterior slip and significant reduction of lumbosacral kyphosis (from 69.8° to 105.13°). Due to complete reduction of lumbosacral kyphosis and anterior trunk displacement associated with L-5 anterior slipping, lumbar lordosis progressively decreased and thoracic kyphosis progressively increased postoperatively. Adjusting the sagittal trunk balance produced not only pelvic anteversion, but also reciprocal adjustment of lumbar lordosis and thoracic kyphosis, creating a satisfactory level of compensated global sagittal balance.

Patients presenting with stenosis associated with a spondylolisthesis will often describe signs and symptoms consistent with neurogenic claudication, radiculopathy, and/or low-back pain. The primary objective of surgery, when deemed appropriate, is to decompress the neural elements. As a result of the decompression, the inherent instability associated with the spondylolisthesis may progress and lead to further misalignment that results in pain or recurrence of neurological complaints. Under these circumstances, lumbar fusion is considered appropriate to stabilize the spine and prevent delayed deterioration. Since publication of the original guidelines there have been a significant number of studies published that continue to support the utility of lumbar fusion for patients presenting with stenosis and spondylolisthesis. Several recently published trials, including the Spine Patient Outcomes Research Trial, are among the largest prospective randomized investigations of this issue. Despite limitations of study design or execution, these trials have consistently demonstrated superior outcomes when patients undergo surgery, with the majority undergoing some type of lumbar fusion procedure. There is insufficient evidence, however, to recommend a standard approach to achieve a solid arthrodesis. When formulating the most appropriate surgical strategy, it is recommended that an individualized approach be adopted, one that takes into consideration the patient's unique anatomical constraints and desires, as well as surgeon's experience.

Interbody fusion techniques have been promoted as an adjunct to lumbar fusion procedures in an effort to enhance fusion rates and potentially improve clinical outcome. The medical evidence continues to suggest that interbody techniques are associated with higher fusion rates compared with posterolateral lumbar fusion (PLF) in patients with degenerative spondylolisthesis who demonstrate preoperative instability. There is no conclusive evidence demonstrating improved clinical or radiographic outcomes based on the different interbody fusion techniques. The addition of a PLF when posterior or anterior interbody lumbar fusion is performed remains an option, although due to increased cost and complications, it is not recommended. No substantial clinical benefit has been demonstrated when a PLF is included with an interbody fusion. For lumbar degenerative disc disease without instability, there is moderate evidence that the standalone anterior lumbar interbody fusion (ALIF) has better clinical outcomes than the ALIF plus instrumented, open PLF. With regard to type of interbody spacer used, frozen allograft is associated with lower pseudarthrosis rates compared with freeze-dried allograft; however, this was not associated with a difference in clinical outcome.

Recombinant human bone morphogenetic protein-2 (rhBMP-2) promotes the induction of bone growth and is widely used in spine surgery to enhance arthrodesis. Recombinant human BMP-2 has been associated with a variety of complications including ectopic bone formation, adjacent-level fusion, local bone resorption, osteolysis, and radiculitis. Some of the complications associated with rhBMP-2 may be the result of rhBMP-2 induction of the inflammatory host response. In this paper the authors report on a patient with prior transforaminal lumbar interbody fusion (TLIF) using an interbody cage packed with rhBMP-2, in which rhBMP-2 possibly contributed to vascular injury during an attempted anterior lumbar interbody fusion. This 63-year-old man presented with a 1-year history of worsening refractory low-back pain and radiculopathy caused by a Grade 1 spondylolisthesis at L4-5. He underwent an uncomplicated L4-5 TLIF using an rhBMP-2-packed interbody cage. Postoperatively, he experienced marginal improvement of his symptoms. Within the next year and a half the patient returned with unremitting low-back pain and neurogenic claudication that failed to respond to conservative measures. Radiological imaging of the patient revealed screw loosening and pseudarthrosis. He underwent an anterior retroperitoneal approach with a plan for removal of the previous cage, complete discectomy, and placement of a femoral ring. During the retroperitoneal approach the iliac vein was adhered with scarring and fibrosis to the underlying previously operated L4-5 interbody space. During mobilization the left iliac vein was torn, resulting in significant blood loss and cardiac arrest requiring chest compression, defibrillator shocks, and blood transfusion. The patient was stabilized, the operation was terminated, and he was transferred to the intensive care unit. He recovered over the next several days and was discharged at his neurological baseline. The authors propose that the rhBMP-2-induced host inflammatory response partially contributed to vessel fibrosis and scarring, resulting in the life-threatening vascular injury during the reoperation. Spine surgeons should be aware of this potential inflammatory fibrosis in addition to other reported complications related to rhBMP-2.

Object: It is not known whether adding fusion to lumbar decompression is necessary for all patients undergoing surgery for degenerative lumbar spondylolisthesis with symptomatic stenosis. Determining specific radiographic traits that might predict delayed instability following decompression surgery might guide clinical decision making regarding the utility of up-front fusion in patients with degenerative Grade I spondylolisthesis., Methods: Patients with Grade I degenerative lumbar spondylolisthesis (3-14 mm) with symptomatic stenosis were prospectively enrolled from a single site between May 2002 and September 2009 and treated with decompressive laminectomy without fusion. Patients with mechanical back pain or with gross motion (> 3 mm) on flexion-extension lumbar radiographs were excluded. The baseline radiographic variables measured included amount of slippage, disc height, facet angle, motion at spondylolisthesis (flexion-extension), and sagittal rotation angle. Data were analyzed using multivariate forward selection stepwise logistic regression, chi-square tests, Student t-test, and ANOVA., Results: Forty patients were enrolled and treated with laminectomy without fusion, and all patients had complete radiographic data sets that were available for analysis. Reoperation was performed in 15 (37.5%) of 40 patients, with a mean follow-up duration of 3.6 years. Reoperation was performed for pain caused by instability at the index level in all 15 cases. Using multivariate stepwise logistic regression with a threshold p value of 0.35, motion at spondylolisthesis, disc height, and facet angle were predictors of reoperation following surgery. Facet angle > 50° was associated with a 39% rate of reoperation, disc height > 6.5 mm was associated with a 45% rate of reoperation, and motion at spondylolisthesis > 1.25 mm was associated with a 54% rate of reoperation. Patients with all 3 risk factors for instability had a 75% rate of reoperation, whereas patients with no risk factors for instability had a 0% rate of reoperation (p = 0.14)., Conclusions: Patients with motion at spondylolisthesis > 1.25 mm, disc height > 6.5 mm, and facet angle > 50° are more likely to experience instability following decompression surgery for Grade I lumbar spondylolisthesis. Identification of key risk factors for instability might improve patient selection for decompression without fusion surgery.

Object: Lumbar spinal stenosis (LSS) is a common condition that leads to significant disability, particularly in the elderly. Current therapeutic modalities for LSS have certain drawbacks when applied to this patient population. The object of this study was to define the 12-month postoperative outcomes and complications of pedicle-lengthening osteotomies for symptomatic LSS., Methods: A prospective, single-treatment clinical pilot study was conducted. A cohort of 19 patients (mean age 60.9 years) with symptomatic LSS was treated by pedicle-lengthening osteotomy procedures at 1 or 2 levels. All patients had symptoms of neurogenic claudication or radiculopathy secondary to LSS and had not improved after a minimum 6-month course of nonoperative treatment. Eleven patients had a Meyerding Grade I degenerative spondylolisthesis in addition to LSS. Clinical outcomes were measured using the Oswestry Disability Index (ODI), Zurich Claudication Questionnaire (ZCQ), 12-Item Short-Form Health Survey (SF-12), and a visual analog scale (VAS). Procedural variables, neurological outcomes, adverse events, and radiological imaging (plain radiographs and CT scans) were collected at the 1.5-, 3-, 6-, 9-, and 12-month time points., Results: The pedicle-lengthening osteotomies were performed through percutaneous approaches with minimal blood loss in all cases. There were no operative complications. Four adverse events occurred during the follow-up period. Clinically, significant improvement was observed in the mean values of each of the outcome scales (comparing preoperative and 12-month values): ODI scores improved from 52.3 to 28.1 (p < 0.0001); the ZCQ physical function domain improved from 2.7 to 1.8 (p = 0.0021); the SF-12 physical component scale improved from 27.0 to 37.9 (p = 0.0024); and the VAS score for leg pain while standing improved from 7.2 to 2.7 (p < 0.0001). Imaging studies, reviewed by an independent radiologist, showed no evidence of device subsidence, migration, breakage, or heterotopic ossification. Thin-slice CT documented healing of the osteotomy site in all patients at the 6-month time point and an increase in the mean cross-sectional area of the spinal canal of 115%., Conclusions: Treatment of patients with symptomatic LSS with a pedicle-lengthening osteotomy procedure provided substantial enlargement of the area of the spinal canal and favorable clinical results for both disease-specific and non-disease-specific outcome measures at the 12-month time point. Future studies are needed to compare this technique to alternative therapies for lumbar stenosis.

Object: In situ transsacral fusion in the treatment of low-grade isthmic spondylolisthesis has rarely been reported. The authors treated 13 cases of L-5 Grade 2 isthmic spondylolisthesis associated with collapsed disc space and osteoporosis by using transsacral fusion and fixation, and compared its clinical and radiological outcomes with the results of transforaminal lumbar interbody fusion (TLIF) and instrumental reduction in 21 patients., Methods: The authors retrospectively analyzed 21 patients in Group A who were treated with reduction and TLIF, and 13 patients in Group B who were treated with transsacral cage fusion. Oswestry Disability Index and visual analog scale scores of back and leg pain were used to evaluate clinical outcomes. Radiological parameters for assessment included the percentage of slippage, whole lumbar lordosis, and lumbosacral angle. Operative data, fusion rate, and perioperative complications were recorded as well., Results: The mean operation time and blood loss in Group B was less than that in Group A. Both groups realized good recovery from previous symptoms. The decrease in back and leg pain after surgery was significant within each group, without much difference between the 2 groups. No significant differences were found in lumbosacral angle, whole lumbar lordosis, visual analog scale score, and Oswestry Disability Index score between the 2 groups after surgery. The solid fusion rate was 95.2% in Group A and 92.3% in Group B. In Group A, 2 patients suffered from graft site pain, 1 had a superficial infection, and 1 had screw loosening; in Group B, dural tears were found in 2 patients, transient S-1 paresthesia in 2, and extensor hallucis longus muscle weakness in 1., Conclusions: For patients with a collapsed disc space and poor bone quality, posterior in situ transsacral cage fusion may be used as an alternative to the TLIF procedure. The short-term clinical and radiological outcomes in the transsacral cage group were comparable with those in the TLIF group, although with a relatively higher neurological complication rate.

Object: The aim of this study was to correlate the degree of L4-5 spondylolisthesis on plain flexion-extension radiographs with the corresponding amount of L4-5 facet fluid visible on MR images., Methods: Patients underwent evaluation at the Neurosurgical Spine Clinics of Stanford University Medical Center and National Health Insurance Medical Center (Goyang, South Korea) between January 2006 and December 2007. Only patients who were diagnosed with L4-5 degenerative spondylolisthesis (DS) and who had both lumbosacral flexion-extension radiographs and MR images available for review were eligible for this study. Each patient's dynamic motion index (DMI) was measured using the lateral lumbosacral plain radiograph and was the percentage of the degree of anterior slippage seen on flexion versus that seen on extension. Axial T2-weighted MR images of the L4-5 facet joints obtained in each patient was analyzed for the amount of facet fluid, using the image showing the widest portion of the facets. The facet fluid index was calculated from the ratio of the sum of the amounts of facet fluid found in the right plus left facets over the sum of the average widths of the right plus left facet joints., Results: Fifty-four patients with L4-5 DS were included in this study. Of these 54 patients, facet fluid was noted on MR images in 29 patients (53.7%), and their mean DMI was 6.349 +/- 2.726. Patients who did not have facet fluid on MR imaging had a mean DMI of 1.542 +/- 0.820; this difference was statistically significant (p < 0.001). There was a positive linear association between the facet fluid index and the DMI in the group of patients who exhibited facet fluid on MR images (Pearson correlation coefficient 0.560, p < 0.01). In the subgroup of 29 patients with L4-5 DS who showed facet fluid on MR images, flexion-extension plain radiographs in 10 (34.5%) showed marked anterolisthesis, while the corresponding MR images did not., Conclusions: There is a linear correlation between the degree of segmental motion seen on flexion-extension plain radiography in patients with DS at L4-5 and the amount of L4-5 facet fluid on MR images. If L4-5 facet fluid in patients with DS is seen on MR images, a corresponding anterolisthesis on weight-bearing flexion-extension lateral radiographs should be anticipated. Obtaining plain radiographs will aid in the diagnosis of anterolisthesis caused by an L4-5 hypermobile segment, which may not always be evident on MR images obtained in supine patients.

Object: Although posterior lumbar interbody fusion (PLIF) is an excellent procedure to attain circumferential decompression, it is technically demanding and can lead to various surgical complications. The authors retrospectively reviewed consecutive patients with nonisthmic spondylolisthesis who underwent PLIF to reveal the incidence and risk factors for perioperative complications of PLIF., Methods: A total of 240 patients underwent PLIF. The fusion level was at L4-5 in 220, L3-4 in 18, and L5-S1 in 2. The medial walls of the fusion segment's facet joints were resected, and the VSP Spine System was used for the pedicle screw instrumentation. The operations were performed by 7 surgeons, who were divided into 4 groups according to their level of experience with spinal surgery., Results: The average operation time was 175 +/- 49 minutes, and the estimated blood loss was 746 +/- 489 ml. A total of 90 patients (37.5%) experienced complications; 41 (17%) experienced transient neurological complications, and 18 (7.5%) experienced permanent neurological complications. The mean neurological score according to the Japanese Orthopaedic Association improved from 14.3 +/- 3.8 to 24.7 +/- 4.0 in the patients without complications and from 14.8 +/- 3.6 to 24.0 +/- 3.9 in the patients with complications. Multivariate analysis concerning the relationship between complications and risk factors (operation time, estimated intraoperative blood loss, and surgeon experience) revealed that operation time was the only significant risk factor for complications., Conclusions: Perioperative complications of PLIF were more frequent in this homogeneous study group than in other studies of various implants. Total excision of the facet joints might preclude neurological complications.

Object: In vivo quantitative measurement of lumbar segmental stability has not been established. The authors developed a new measurement system to determine intraoperative lumbar stability. The objective of this study was to clarify the biomechanical properties of degenerative lumbar segments by using the new method., Methods: Twenty-two patients with a degenerative symptomatic segment were studied and their measurements compared with those obtained in normal or asymptomatic degenerative segments (Normal group). The measurement system produces cyclic flexion-extension through spinous process holders by using a computer-controlled motion generator with all ligamentous structures intact. The following biomechanical parameters were determined: stiffness, absorption energy (AE), and neutral zone (NZ). Discs with degeneration were divided into 2 groups based on magnetic resonance imaging grading: degeneration without collapse (Collapse[-]) and degeneration with collapse (Collapse[+]). Biomechanical parameters were compared among the groups. Relationships among the biomechanical parameters and age, diagnosis, or radiographic parameters were analyzed., Results: The mean stiffness value in the Normal group was significantly greater than that in Collapse(-) or Collapse(+) group. There was no significant difference in the average AE value among the Normal, Collapse(-), and Collapse(+) groups. The NZ in the Collapse(-) was significantly higher than in the Normal or Collapse(+) groups. Stiffness was negatively and NZ was positively correlated with age. Stiffness demonstrated a significant negative and NZ a significant positive relationship with disc height, however., Conclusions: There were no significant differences in stiffness between spines in the Collapse(-) and Collapse(+) groups. The values of a more sensitive parameter, NZ, were higher in Collapse(-) than in Collapse(+) groups, demonstrating that degenerative segments with preserved disc height have a latent instability compared to segments with collapsed discs.

Object: A primary consideration of all spinal fusion procedures is restoration of normal anatomy, including disc height, lumbar lordosis, foraminal decompression, and sagittal balance. To the authors' knowledge, there has been no direct comparison of anterior lumbar interbody fusion (ALIF) with transforaminal lumbar interbody fusion (TLIF) concerning their capacity to alter those parameters. The authors conducted a retrospective radiographic analysis directly comparing ALIF with TLIF in their capacity to alter foraminal height, local disc angle, and lumbar lordosis., Methods: The medical records and radiographs of 32 patients undergoing ALIF and 25 patients undergoing TLIF from between 2000 and 2004 were retrospectively reviewed. Clinical data and radiographic measurements, including preoperative and postoperative foraminal height, local disc angle, and lumbar lordosis, were obtained. Statistical analyses included mean values, 95% confidence intervals, and intraobserver/interobserver reliability for the measurements that were performed., Results: Our results indicate that ALIF is superior to TLIF in its capacity to restore foraminal height, local disc angle, and lumbar lordosis. The ALIF procedure increased foraminal height by 18.5%, whereas TLIF decreased it by 0.4%. In addition, ALIF increased the local disc angle by 8.3 degrees and lumbar lordosis by 6.2 degrees, whereas TLIF decreased the local disc angle by 0.1 degree and lumbar lordosis by 2.1 degrees., Conclusions: The ALIF procedure is superior to TLIF in its capacity to restore foraminal height, local disc angle, and lumbar lordosis. The improved radiographic outcomes may be an indication of improved sagittal balance correction, which may lead to better long-term outcomes as shown by other studies. Our data, however, demonstrated no difference in clinical outcome between the two groups at the 2-year follow-up.