Transforaminal Interbody Research Articles

Positional effects of transforaminal interbody spacer placement at the L5–S1 intervertebral disc space: a biomechanical study

Background contextTransforaminal lumbar interbody fusion (TLIF) is an increasingly used alternative fusion method over anterior and posterior lumbar interbody fusions. There are conflicting results on the optimal positioning of interbody devices. No study has addressed the lumbosacral segment, L5–S1, where the lordotic configuration presents unique challenges. PurposeTo determine if there are biomechanical and/or anatomical advantages related to the positioning of an interbody device at L5–S1, either anterior or posterior to the neutral axis. Study designAn in vitro biomechanical study using human cadaveric lumbar specimens. MethodsLumbar specimens were biomechanically tested using pure moments with and without compressive axial loading. Testing was performed in intact and after TLIF with the implant posterior (TLIF-post) and anterior (TLIF-ant) to neutral axis. Segmental range of motion (ROM) and stiffness were analyzed at the L5–S1 surgical level and the adjacent L4–L5 level. Neuroforaminal height measurements of L5–S1 were analyzed in neutral and end range positions. ResultsCompared with the intact condition, ROM decreased more than 75% at L5–S1 and stiffness increased up to 270% with TLIF. There was no significant difference between anterior or posterior placement for ROM and stiffness. There was a change in L5–S1 neuroforaminal height based on the placement, with posterior placement showing a significant increase compared with anterior placement. There were no relative changes in neuroforaminal height under loading after TLIF. Compressive load did not affect the magnitudes or resulting significance of outcome measures at L5–S1 after either TLIFs. ConclusionsAn interbody spacer with the addition of posterior instrumentation significantly enhances the mechanical stability of L5–S1 regardless of interbody position. There were noticeable increases in terms of construct stability and stiffness after both TLIF-ant and TLIF-post in comparison with the intact condition. A posteriorly placed interbody implant did result in the distraction of the neuroforamin. Positioning an interbody implant at L5–S1 for TLIF with posterior instrumentation should be at the discretion of the surgeon without consequence to biomechanical stability.

Long-term clinical outcomes of selective segmental transforaminal lumbar interbody fusion combined with posterior spinal fusion for degenerative lumbar scoliosis.

The purpose of the current study was to investigate the long-term clinical outcomes of this technique for degenerative scoliosis (DS). The records of 95 consecutive patients with DS who underwent selective segmental transforaminal interbody fusion combined with posterior-instrumented spinal fusion in our department from January 1999 to December 2007 were analysed retrospectively. Average follow-up was 7.8 years. Recorded clinical outcomes included Oswestry Disability Index (ODI), visual analogue scale (VAS) pain scores and overall patient satisfaction. Radiographic measurements included coronal Cobb angle, apical vertebra translation, Nash-Moe grade, lumbar lordosis (LL) and thoracolumbar kyphosis. Comparison of the clinical and radiographic parameters before surgery and at final follow-up was studied. Linear correlation analysis was applied to analyse the relationship between the clinical and radiological results. Average ODI and VAS pain scores were significantly improved at final follow-up compared with baseline (P=0.038; P=0.005). Specifically, the average ODI score was 32.2±8.6 before surgery and 11.1±6.8 at final follow-up; the average VAS score was 8.9±2.0 before surgery and 2.0±1.2 at final follow-up; patient satisfaction was 88.2% (84/95) at final follow-up. In addition, Cobb angle, apical vertebra translation and Nash-Moe grade were all statistically significantly decreased compared with preoperative values (P=0.019; P=0.035; P=0.001). Although LL had significantly increased (P=0.022), thoracolumbar kyphosis did not exhibit a significant change (P=0.64). There was significant correlation between LL and decreased ODI scores (r=0.62, P=0.01). Eleven patients (11.6%) underwent reoperation during the study period. Selective segmental transforaminal interbody fusion combined with posterior-instrumented spinal fusion appears to have reasonable long-term clinical and radiographic outcomes for the treatment of DS.

Biomechanical analysis of various footprints of transforaminal lumbar interbody fusion devices.

A biomechanical finite element modeling study of the human lumbar spine. To evaluate the effects of a transforaminal interbody device's footprint on lumbar spine biomechanics to further examine the potential subtle biomechanical differences not captured in previous studies. In recent years, the evolution of interbody fusion devices has provided the surgeons with a multitude of options. An articulating transforaminal lumbar interbody fusion (TLIF) device is developed to overcome the surgical challenges associated with insertion of a large footprint interbody device through a small incision. A finite element model of the L3-S1 lumbar segment was modified to simulate replacement of various TLIF constructs with different cage designs including an articulating vertebral interbody (AVID) TLIF device and a generic TLIF device placed in different configurations. The instrumented models were subjected to a 400 N follower load along with a 10 N m bending moment at different physiological planes. The kinematics, loads, and stresses were compared among various models. Simulated cage designs provided similar kinematical stability within the treated segments. However, the articulating and double TLIF implants allowed for better load sharing through the anterior column. These implants resulted in lower endplate and pedicle screw stresses and in more homogenous stress distribution across the peripheral region of the endplate. An articulating, large footprint, peripherally placed TLIF device affords substantial biomechanical advantages. This device may be able to reduce the incidence of subsidence because of its ability to reduce and distribute the endplate stresses in the stronger peripheral region. It may also reduce the posterior hardware failure incidence owing to its ability to reduce the screw stresses as compared with traditional TLIF. Although double TLIF has been demonstrated to have similar biomechanical advantages as the AVID, complications associated with double TLIF (ie, larger surgical incision, longer surgical procedure, placement and alignment challenges) support AVID as a better optimized alternative.

Finite element analysis of minimal invasive transforaminal lumbar interbody fusion.

The purpose of our study is to develop and validate three-dimensional finite element models of transforaminal lumbar interbody fusion, and explore the most appropriate method of fixation and fusion by comparing biomechanical characteristics of different fixation method. We developed four fusion models: bilateral pedicle screws fixation with a single cage insertion model (A), bilateral pedicle screws fixation with two cages insertion model (B), unilateral pedicle screws fixation with a single cage insertion model (C), and unilateral pedicle screws fixation with two cages insertion model (D); the models were subjected to different forces including anterior bending, posterior extension, left bending, right bending, rotation, and axial compressive. The von Mises stress of the fusion segments on the pedicle screw and cages was recorded. Angular variation and stress of pedicle screw and cage were compared. There were differences of Von Mises peak stress among four models, but were within the range of maximum force. The angular variation in A, B, C, and D decreased significantly compared with normal. There was no significant difference of angular variation between A and B, and C and D. Bilateral pedicle screws fixation had more superior biomechanics than unilateral pedicle screws fixation. In conclusion, the lumbar interbody fusion models were established using varying fixation methods, and the results verified that unilateral pedicle screws fixation with a single cage could meet the stability demand in minimal invasive transforaminal interbody fusion.

Minimally invasive transforaminal interbody fusion surgery for the old fracture of the thoracolumbar junction.

Retrospective analysis of the clinical outcomes of 15 patients with the old thoracolumbar junction fracture treated by minimally invasive surgery (MIS) transforaminal interbody fusion surgery. To investigate the efficacy and safety of MIS for the old fracture of the thoracolumbar junction in a pilot study. MIS have demonstrated efficacy in the treatment of lumbar degenerative diseases. There is some controversy regarding the ideal management of thoracolumbar fractures, especially those without an associated neurologic deficit. Reports concerning MIS for old thoracolumbar junction fracture with chronic pain are quite rare. A total of 15 MIS fusion, performed between October 2006 and May 2011, were examined in a retrospective study. The clinical and radiological data were collected and analyzed. Fusion levels were T10–T11 (2 patients), T11–T12 (5 patients), T12–L1 (6 patients), L1–L2 (2 patients). Clinical outcome was assessed using the visual analogue scale and the Oswestry disability index. Radiographic evaluation of the lumbar spine was performed at the second day and 12 months postoperatively. The average follow-up period was 26.3 months, with a minimum of 17 months. The mean operating time, intraoperative blood loss, and x-ray exposure time were 125±31 minutes, 226±45 mL, and 47±12 seconds, respectively. At last followup,the visual analogue scale for back pain and the Oswestry disability index decreased significantly postoperatively from 7.4±2.3 to 1.8±0.6 (P<0.01) and from 38.9±7.1 to 13.5±4.5 (P<0.01), respectively. The average Cobb angle was improved from 19.1–15.1 degrees in this series. No significant correction of local kyphosis was found postoperatively (P>0.05). Radiographic evaluation showed satisfactory bony union at the fixed level in all cases except for 2 patients. There were no other major complications at last follow-up. MIS transforaminal interbody fusion is a safe and effective procedure for old thoracolumbar junction fracture with chronic pain. Improvement of kyphosis is limited and occurrence of nonunion is relatively high.

Comparison of the results of MIS-TLIF and open TLIF techniques in laborers

Objective: To compare clinical outcomes in laborers who have undergone open transforaminal interbody fusion (TLIF) and minimally invasive transforaminal interbody fusion (MIS TLIF). Methods: 78 patients were submitted to lumbar arthrodesis by the same two spine surgeons partners from January 2008 to December 2012. Forty-one were submitted to traditional open arthrodesis and 37 to the minimally invasive procedure. Three patients were not included because they had already retired from work. The analyzed variables were length of hospitalization, length of follow-up, type of access (TILF or MIS TLIF), need for blood transfusion, percentage of improvement or worsening after surgery, pre- and postoperative VAS scale, time off work, pre-and postoperative Oswestry disability index, and general aspects of the laborers such as age, education, profession, working time, amount of daily weight carried at work, and use or not of personal protective equipment. Results: Time off work was longer in the TLIF group (average of 9.84 months) compared with the MIS TLIF group (average of 3.20 months). Significant improvement in postoperative VAS and Oswestry was achieved in both groups. Average length of hospitalization was 5.73 days for the TLIF group and 2.76 days for the MIS TLIF group. Conclusions: Minimally invasive transforaminal lumbar interbody fusion presents similar results when compared to open TLIF, but has the benefits of less postoperative morbidity, shorter hospitalization times, and faster rehabilitation in laborer patients.

Dilemma in the Surgical Management of Lumbar Canal Stenosis

For a long time wide decompressive laminectomy, direct visualization and decompression of affected nerve roots, foraminotomy and when necessary discectomy had remained the gold standard to operate patients with lumbar canal stenosis. There was confusion in the literature concerning the role of fusion even in the presence of instability in degenerative lumbar canal stenosis due to absence of prospective randomized clinical trials. This has led to uncertainty about the correct choice of surgical strategy as no evidence based recommendations on the role of instrumented PLIF in older patients. Such thoughts have compelled some to try minimally invasive instrumentation with micro decompression, transforaminal interbody fusion and percutaneous pedicle screws. It has the advantage of short incision, less morbidity, shortened bed rest and early ambulation which is so essential in older patients with comorbid conditions. In this study we discuss the pathogenesis of development of spinal conditions and their treatment options through the history of spinal surgery. Also discussed is the dilemma that exists in spinal surgeons regarding the selection of appropriate treatment strategy for stenosis amongst the elderly.

Disc herniation in the thoracolumbar junction treated by minimally invasive transforaminal interbody fusion surgery

Minimally invasive surgery-transforaminal lumbar interbody fusion (MIS-TLIF) has demonstrated efficacy in the treatment of lumbar degenerative diseases. Use of this procedure for thoracolumbar junction disc herniation remains challenging. Reports concerning MIS-TLIF at the thoracolumbar junction are rare. Thus, we performed a retrospective analysis of the clinical outcomes of 10 patients with thoracolumbar junction disc herniation treated by MIS-TLIF between December 2007 and October 2010. The purpose of this study was to investigate the efficacy and safety of MIS-TLIF for disc herniation in the thoracolumbar junction. Clinical and radiological data were collected and analyzed. Fusion levels included T12–L1 (two patients), L1–L2 (four patients) and L2–L3 (four patients). Clinical outcome was assessed using the Visual Analogue Scale (VAS) and Oswestry Disability Index (ODI). The average follow-up period was 39.2months, with a minimum of 24months. The mean±standard error of the mean of the operative time, intraoperative blood loss, and x-ray exposure were 128±36minutes, 204±35mL, and 43±12seconds, respectively. The VAS for back and leg pain decreased significantly postoperatively from 6.4±2.7 to 1.5±0.6 (p<0.01), and from 7.1±2.4 to 1.3±0.4 (p<0.01) respectively, as did the ODI from 39.3±11.2 to 16.5±4.7 (p<0.01). Bone fusion was observed in eight patients. There were no other major complications at last follow-up. MIS-TIF is a safe and effective procedure for disc herniation in the thoracolumbar junction. Occurrence of non-union is relatively high compared to previous findings.

Clinical results and intramedullary signal changes of posterior decompression with transforaminal interbody fusion for thoracic myelopathy caused by combined ossification of the posterior longitudinal ligament and ligamentum flavum

Background Surgical treatment of thoracic myelopathy caused by ossification of the posterior longitudinal ligament (OPLL) and ossification of the ligamentum flavum (OLF) is technically demanding, and the results tend to be unfavorable. Various operative approaches and treatment strategies have been attempted, and posterior decompression with transforaminal thoracic interbody fusion (PTTIF) may be the optimal method with which the anterior-posterior compression was removed in one step. It is comparatively less traumatic with fewer serious complications. Methods Sixteen patients with thoracic myelopathy due to concurrent OLF and OPLL at the same level underwent PTTIF. We investigated clinical outcomes and neurological improvements. Magnetic resonance imaging (MRI) was performed on all patients preoperatively and postoperatively, and intramedullary signal changes were evaluated. Results The mean operating time was 275 minutes, and the mean operative bleeding amount was 1031 ml. Cerebrospinal fluid leakage occurred in three patients and healed well after repair. Neurological symptom deterioration occurred in one patient, but the patient recovered to nearly the preoperative level after methylprednisolone treatment. The follow-up period ranged from 28 to 47 months. The mean score on the Japanese Orthopedic Association scale improved from 4.3±1.2 preoperatively to 7.3±1.7 at 3 months postoperatively to 8.5±1.5 at the final follow-up (P &lt;0.01), with a recovery rate of (63.6±20.0)%. Postoperative images showed a significant improvement in local kyphosis (P &lt;0.01). Eleven patients (68.8%) showed increased signal intensity (ISI) on preoperative T2-weighted MRI. At the final follow-up, the intramedullary ISI totally recovered in five patients. Neurological improvement was worse in patients with persistent ISI than in the other patients (P &lt;0.05). Conclusions PTTIF is an effective therapeutic option for combined OPLL and OLF and provides satisfactory neurological recovery and stabilized thoracic fusion through a single posterior approach. Intramedullary signal changes do not always indicate a poor prognosis; only irreversible ISI is correlated with a poor clinical result.

Feasibility and biomechanical performance of a novel transdiscal screw system for one level in non-spondylolisthetic lumbar fusion: an in vitro investigation

Background contextThe bilateral pedicle screw system (BPSS) is currently the “gold standard” fusion technique for spinal instability. A new stabilization system that provides the same level of stability through a less invasive procedure will have a high impact on clinical practice. A new transdiscal screw system is investigated as a promising minimally invasive device. PurposeTo evaluate the feasibility of a novel transdiscal screw in spinal fixation as an alternative to BPSS, with and without an interbody cage, in non-spondylolisthesis cases. Study designAn in vitro biomechanical study in lumbar cadaveric spines. MethodsTwelve lumbar cadaveric segments (L4–S1) were tested under flexion-extension (FE), lateral bending (LB), and axial rotation (AR). Six treatments were simulated as follows: (1) intact, (2) bilateral facetectomy at L4–L5, (3) transdiscal screw system, (4) BPSS, (5) BPSS with transforaminal lumbar interbody cage, and (6) transdiscal screws with transforaminal interbody cage. Specimens were randomly divided into two testing groups: Group 1 (n=6) was tested under the first five conditions, in the order presented, whereas Group 2 (n=6) was tested under the first, second, third, fourth, and sixth conditions, with the fourth condition preceding the third. Range of motion (ROM) and neutral zone stiffness (NZS) were estimated and normalized with respect to the intact condition to explore statistical differences among treatments using non-parametric approaches. ResultsSignificant differences in FE ROM were observed in the pedicle screws-cage condition with respect to the facetectomy (p<.01), the pedicle screw (p=.03), and the transdiscal screw (p<.02) conditions. All fixation constructs significantly restricted LB and AR ROM (p<.01) with respect to facetectomy. In terms of stiffness, the pedicle screw and the transdiscal screw systems increased (p<.01) LB and AR NZS with respect to facetectomy. The pedicle screws-cage condition significantly increased flexion and extension stiffness with respect to all other conditions (p<.05). However, LB NZS for the pedicle screws-cage and the transdiscal screws-cage condition could not be explored due to a testing order bias effect. There was not enough evidence to state any difference between the pedicle and transdiscal screw conditions in terms of ROM or NZS. ConclusionsTransdiscal and pedicle screw systems showed comparable in vitro biomechanical performance in the immediate stabilization of a complete bilateral facetectomy. The pedicle screws-cage condition was the most stable in FE motion; however, comparison with respect to the transdiscal screws-cage condition could not be investigated.

Clinical control study on MiTLIF and open-TLIF for treatment of lumber degenerative diseases

Objective To investigate the clinical outcomes and complications of minimally invasive transforaminal lumber interbody fusion (MiTLIF) and open-TLIF for lumber degenerative diseases.Methods Between March,2010 and June,2012,75 patients of lumber degenerative diseases were operated in neurosurgical department of Sichuan Provincial People,s Hospital.MiTLIF and open-TLIF was performed in 32 and 43 patients,respectively.MiTLIF was done by using expandable working tubes (Quadrant)and percutaneous pedicle screws(Sextant).Operative time,intraoperative blood loss,length of hospital-stay,and complications were collected.Visual analog scale (VAS) scores were recorded to evaluate clinical outcomes.Interbody fusion was evaluated via dynamic radiographs,and with thin CT scan reconstructions.Results The total complication rate was 19％ (6/32) in the MiTLIF group and 21％ (9/ 43) in the open-TLIF,P =0.12.The operative time was (1.5 ± 0.3) h for MiTLIF and (1.6 ± 0.5) h for open procedures,P =0.56.The intraoperative blood loss for the MiTLIF (136.0 ± 43.0) ml was significantly lower than the open-TLIF(292.0 ± 112.0) ml,P ＜ 0.0001.The mean length of hospital-stay in the MiTLIF (4.5 ± 2.7) d was significantly shorter than the open-TLIF (7.2 ± 4.6) d,P =0.0015.The mean change in VAS scores postoperatively was no statistical difference in the two groups(5.4 vs.5.2 P =0.9).The interbody fusion rate at last follow-up in the MiTLIF group (94％,30/32) was comparable with that in the open-TLIF (98％,42/43),P =0.22.Conclusions MiTLIF technique may provide equivalent clinical outcomes compared to open-TLIF for lumber degenerative diseases.The benefits of MiTLIF includes reduced blood loss,short length hospital-stay,and decreased severe complications. Key words: Transforaminal lumber interbody fusion; Minimally invasive surgery; Degenerative lumber disease

Relationship between Surgical Technique and the Incidence of Adjacent Level Pathology in Lumbar Spine Fusion: Open Traditional Approach (OTA) Versus Minimally Invasive Transforaminal Interbody Fusion and Percutaneous Screws (MIS TLIF/PPS)

Large Skin incision, significant muscle retraction, and bone removal associated with traditional fusion procedure are known to lead to a long recovery time, postoperative complications. Adjacent Level disease (ALP) refers to the degeneration of the segment above and/or below the fused vertebrae. Many factors as disturb of the facet joints and posterior ligament complex lead to a biomechanical alterations. MIS procedures may decrease or prevent ALP from occurring.

Reamed Transacral Interbody Fusion for L5–S1 Pseudoarthrosis

A retrospective cohort study. To present the technique, radiographic, and clinical outcomes of a series of patients who underwent a novel method for revision L5-S1 interbody fusion. Pseudoarthrosis at L5-S1 is a relatively common problem after long fusion to the sacrum. Revision approach to L5-S1 for cage or graft removal by anterior lumbar interbody fusion, posterior lumbar interbody fusion, or transforaminal interbody fusion is challenging and potentially dangerous which makes salvage by a posterior reamed transacral technique appealing. Consecutive patients with symptomatic pseudoarthrosis at L5-S1, who underwent posterior reamed fluoroscopically guided fusion were identified over a 3-year period. Operative notes, medical records, preoperative and postoperative plain radiographs, computed tomography scans, Visual Analog Scores (VAS) (lower extremity and low back) preoperatively, and at most recent follow-up were studied. Ten patients (age, 53±2.8 y) with prior lumbar spinal operations (mean, 3.5±0.6) met the inclusion criteria. Prior procedures at L5-S1 were anterior lumbar interbody fusion (n=4), posterior lumbar interbody fusion (n=3), and posterolateral fusion (n=3). Mean Meyerding grade was 1.41 (range, 0-4). Reaming was performed between the S1 and S2 (n=9) or S2 and S3 (n=1) nerve roots and allowed fragmentation/removal of polyetheretherketone interbody grafts (n=3) or femoral ring allografts (n=3). Transacral Harms cage (n=8) or autograft (n=1) was passed through the reamed channel or a carbon fiber-reinforced polyetheretherketone directly into the interspace (n=1). VAS scores lower extremity (P=0.003) and low back (P=0.001) were improved at a mean follow-up of 13.5±3.6 months. No neurologic sequelae occurred and solid fusion was achieved in 9/10 (90%). We report a series of patients who underwent a novel revision technique for symptomatic lumbosacral pseudoarthrosis. Despite the small numbers in this cohort, a salvage technique is presented that permitted fusion as confirmed by computed tomography scan and improved VAS scores in the majority of patients. The data suggest that this technique should be considered as an alternative to the revision anterior or posterior approaches to L5-S1 and merits further investigation.

Mini-open transforaminal lumbar interbody fusion

The potential advantages of a mini-open transforaminal interbody fusion (TLIF) operation are reduced blood loss, shorter length of stay, and less soft-tissue trauma compared to the standard open technique. Prior reports from our group and others have demonstrated successful outcomes using MIS techniques in lumbar fusion surgery. In this 3D video, we demonstrate the key steps of the mini-open technique for a transforaminal lumbar interbody fusion using an expandable tubular retractor and contralateral percutaneous screw fixation for the treatment of a multiple recurrent disc herniation. The video demonstrates patient positioning, surgical opening with development of the Wiltse plane, placement of the tubular retractor, pedicle screw placement through both a percutaneous technique and a mini-open technique, decompression of the neural elements, graft insertion, and wound closure. The video can be found here: http://youtu.be/LYRU9lbBdNg.

Experience with transforaminal interbody fusion in corrective surgery for adolescent idiopathic scoliosis

One of the surgical goals during the treatment of adolescent idiopathic scoliosis (AIS) is to preserve segments and thus mobility while achieving a well-balanced spine on all planes. The transforaminal interbody fusion (TLIF) technique allows for a significant degree of rotational correction and thus may allow for preservation of more mobile segments. This retrospective study analyzed the use of TLIF in AIS patients who underwent surgery between 2006 and 2009 at a single center, and discusses the degree of curve correction, complications and outcomes. All curves were classified using the Lenke classification system. Standing posterior-anterior Cobb angle, sagittal and coronal balance, percent correction, and end/stable/neutral/apical vertebra were determined on preoperative, postoperative and follow-up radiographs. Nine patients were identified (eight women and one man) ranging in age from 11.6–18years. All TLIF procedures were performed at the L2/3 level. Lenke curves included 5CN (n=5), 5BN (n=2), and 6CN (n=2). Average follow-up was 27.4months (range, 12–57months). Average postoperative curve correction was 79%. One patient underwent revision surgery. All patients remained stable from a clinical and radiographic standpoint on their last follow-up visit. TLIF is an important adjunct in the surgical management of select AIS patients. By allowing for greater rotational correction, it may be possible to preserve one more mobile segment without decompensation or overcorrection. To our knowledge, this is the first report on the role of TLIF in AIS. Future studies are warranted in determining those who will maximally benefit from this technique.

Properties of an interspinous fixation device (ISD) in lumbar fusion constructs: a biomechanical study

BackgroundSegmental fixation improves fusion rates and promotes patient mobility by controlling instability after lumbar surgery. Efforts to obtain stability using less invasive techniques have lead to the advent of new implants and constructs. A new interspinous fixation device (ISD) has been introduced as a minimally invasive method of stabilizing two adjacent interspinous processes by augmenting an interbody cage in transforaminal interbody fusion. The ISD is intended to replace the standard pedicle screw instrumentation used for posterior fixation. PurposeThe purpose of this study is to compare the rigidity of these implant systems when supplementing an interbody cage as used in transforaminal lumbar interbody fusion. Study designAn in vitro human cadaveric biomechanical study. MethodsSeven human cadaver spines (T12 to the sacrum) were mounted in a custom-designed testing apparatus, for biomechanical testing using a multiaxial robotic system. A comparison of segmental stiffness was carried out among five conditions: intact spine control; interbody spacer (IBS), alone; interbody cage with ISD; IBS, ISD, and unilateral pedicle screws (unilat); and IBS, with bilateral pedicle screws (bilat). An industrial robot (KUKA, GmbH, Augsburg, Germany) applied a pure moment (±5 Nm) in flexion-extension (FE), lateral bending (LB), and axial rotation (AR) through an anchor to the T12 vertebral body. The relative vertebral motion was captured using an optoelectronic camera system (Optotrak; Northern Digital, Inc., Waterloo, Ontario, Canada). The load sensor and the camera were synchronized. Maximum rotation was measured at each level and compared with the intact control. Implant constructs were compared with the control and with each other. A statistical analysis was performed using analysis of variance. ResultsA comparison between the intact spine and the IBS group showed no significant difference in the range of motion (ROM) in FE, LB, or AR for the operated level, L3–L4. After implantation of the ISD to augment the IBS, there was a significant decrease in the ROM of 74% in FE (p<.001) but no significant change in the ROM in LB and AR. The unilat construct significantly reduced the ROM by 77% compared with FE control (p<.001) and by 55% (p=.002) and 42% (p=.04) in LB and AR, respectively, compared with control. The bilat construct reduced the ROM in FE by 77% (p<.001), LB by 77% (p=.001), and AR by 65% (p=.001) when compared with the control spine. There was no statistically significant difference in the ROM in FE among the stand-alone ISD, unilat, and bilat constructs. However, in both LB and AR, the unilat and the bilat constructs were significantly stiffer (reduction in the ROM) than the ISD and the IBS combination. The ISD stability in LB and AR was not different from the intact control with no instrumentation at all. There was no statistical difference between the stability of the unilat and the bilat constructs in any direction. However, LB and AR in the unilat group produced a mean rotation of 3.83°±3.30° and 2.33°±1.33°, respectively, compared with the bilat construct that limited motion to 1.96°±1.46° and 1.39°±0.73°. There was a trend suggesting that the bilat construct was the most rigid construct. ConclusionsIn FE, the ISD can provide lumbar stability comparable with Bilat instrumentation. It provides minimal rigidity in LB and AR when used alone to stabilize the segment after an IBS placement. The unilat and the more typical bilat screw constructs were shown to provide similar levels of stability in all directions after an IBS placement, though the bilat construct showed a trend toward improved stiffness overall.

Predictive Factors for the Use of Autologous Cell Saver Transfusion in Lumbar Spinal Surgery

Retrospective review. To identify risk factors for cell saver transfusion in lumbar spinal surgery and determine if cell saver transfusions affected intraoperative or postoperative transfusion rates. Cell saver has been used to minimize allogeneic blood transfusion in lumbar spinal surgery. Conflicting reports exist, which call into question the efficacy of cell saver use. We reviewed medical records of randomly selected patients who underwent posterolateral fusion with or without transforaminal interbody fusion from July 2010 to June 2011. Transfusion rates and transfusion-related complications were determined. Binary logistic regression was performed to identify risk factors for use of autologous cell saver transfusion. There were 178 females and 107 males, with a mean age of 57.2 years. Of the 285 cases, 39 had no cell saver available, 147 had cell saver available but no autologous blood was recovered or transfused and 99 had an autologous cell saver transfusion. Patients who had cell saver transfusion had a higher rate of intraoperative allogeneic blood transfusion (52%) compared with those who did not (22%). There was no significant difference in the rate of postoperative transfusions or transfusion-related reactions between patients who did and did not have cell saver transfusion. Patient's age, smoking status, American Society of Anesthesiologists grade, use of anticoagulants preoperatively, primary or revision surgery, iliac crest bone graft harvest, anesthesiologist, or surgeon had no significant effect on cell saver infusion. Body mass index (odds ratio [OR] = 1.06), number of posterolateral fusion levels fused (OR = 2.50), and number of transforaminal interbody fusions performed (OR = 2.41) were independent risk factors for the use of autologous cell saver transfusion. Body mass index, multi-level fusion and transforaminal interbody fusion result in increased use of autologous cell saver transfusion in lumbar spinal surgery. Use of autologous cell saver transfusion did not reduce the requirement for intraoperative or postoperative allogeneic blood transfusion. 2.

Effects of an Optimized Automated Disc Preparation on Clinical and Radiological Outcome of Minimally Invasive Transforaminal Interbody Fusion Procedure

Objective: In minimally invasive techniques for transforaminal lumbar interbody fusion (MIS TLIF) access to the disc and by consequence, the extension of the discectomy can be reduced. Insufficient disc removal and endplate violation can lead to non-unions, subsidence and pseudoarthroses. In this study, we compare the quality of disc preparation, volume of bone graft and clinical results in a group of patients who underwent MIS TLIF with discectomy and endplate preparation aided by an automated discectomy device, the enSpireTM Flex MIS Surgical Discectomy System (study group) to a control group with classical, manual instrumentation for disc preparation. Materials and methods: Twenty-seven consecutive patients were enrolled in the study group and 33 patients in the control group. All patients received similar mixture of autologous bone and cadaver allograft. Disc volume and the quantity of graft placed in the disc space was measured on the discharge CT scan and compared in a blinded, independent radiology review. Clinical outcomes assessed using the Visual Analog Scale (VAS) for leg and low back pain and the Oswestry Disability Index (ODI) were compared at 12 months postoperative. Results: The mean volume of bone graft placed and the ratio bone graft/nucleus was higher in the study group (6.21 cm3 vs. 4.39 cm3 ; p<0001 and 76.8% vs. 57.8%; p<0.0001). The mean Patient Satisfaction Index (PSI) of the EnSpire group was statistically higher than the control group (4.6 ± 0.6 vs. 3.9 ± 0.7). Conclusion: In the challenging MIS TLIF approach, we demonstrate that by using the enSpire™ Flex MIS Surgical Discectomy System, we can optimize the extension and quality of the discectomy, increase the volume of bone graft, and achieve better clinical outcomes.

Preliminary Results of Minimally Invasive Decompression, TLIF and Percutaneous Pedicle Screw Insertion in Stenotic Spondylolisthesis with Severe Facet Joint Osteoarthritis

Object: Minimally invasive spine (MIS) procedures are increasingly being recognized as equivalent to open procedures with regard to clinical and radiographic outcomes. These techniques are also believed to result in less pain and disability in the immediate postoperative period. There are, however, little data to assess whether these procedures in combination with minimally invasive transforaminal interbody fusion (MI-TLIF) and percutaneous pedicle screw insertion are effective in complex cases of stenotic degenerative spondylolisthesis with severe facet joint osteoarthritis (FJO). Methods: This study retrospectively reviewed all patients who underwent lumbar instrumentation, fusion and decompression for degenerative spondylolisthesis with severe stenosis and facet joint osteoarthritis (FJO) between June 2010 and June 2011. Blood loss, operative time and intraoperative complications were assessed in all surgically treated patients who were treated with MIS decompression, MI-TLIF and percutaneous transpedicular instrumentation. Clinical outcome was measured using the Oswestry Disability Index (ODI) and Visual Analogue Scale (VAS) for back pain, leg pain, and activity level. Satisfaction was assessed with VAS for satisfaction. Radiological follow-up includes x-ray films, computed tomography and in some cases magnetic tomography scan. Results: Twenty four cases with severe stenotic changes accompanied by severe FJO were treated with minimally invasive procedure. The minimum follow-up was 6 months with a mean of 8 months. The mean preoperative ODI score was 46.8, decreasing to a mean of 23 postoperatively. The mean VAS leg and back pain scores were 67.5 improving to means of 25.8. Twenty one out of 24 cases experienced a clinical benefit according to VAS for satisfaction and ODI. Complications included wound healing disturbance (4%), CSF fistula (4%) and contralateral radiculopathy due to articular bone spurs (8%). The accuracy of pedicle screws was high and only one revision surgery was performed. Conclusion: MIS for severe stenotic spondylolisthesis leads to adequate and safe decompression of lumbar stenosis and results in a highly significant reduction of symptoms and disability. MIS-TLIF and percutaneous pedicle screw insertion constitute a promising treatment alternative for patients with severe stenosis and facet joint osteoarthritis.

Slip Reduction Rate between Minimal Invasive and Conventional Unilateral Transforaminal Interbody Fusion in Patients with Low-Grade Isthmic Spondylolisthesis.

ObjectiveTo compare the slip reduction rate and clinical outcomes between unilateral conventional transforaminal lumbar interbody fusion (conventional TLIF) and unilateral minimal invasive TLIF (minimal TLIF) with pedicle screw fixation for treatment of one level low-grade symptomatic isthmic spondylolisthesis.MethodsBetween February 2008 and April 2012, 25 patients with low-grade isthmic spondylolisthesis underwent conventional TLIF (12 patients) and minimal TLIF (13 patients) in single university hospital by a single surgeon. Lateral radiographs of lumbar spine were taken 12 months after surgery to analyze the degree of slip reduction and the clinical outcome. All measurements were performed by a single observer.ResultsThe demographic data between conventional TLIF and minimal TLIF were not different. Slip percentage was reduced from 15.00% to 8.33% in conventional TLIF, and from 14.15% to 9.62% in minimal TLIF. In both groups, slip percentage was significantly improved postoperatively (p=0.002), but no significant intergroup differences of slip percentage in preoperative and postoperative were found. The reduction rate also not different between conventional TLIF (45.41±28.80%) and minimal TLIF (32.91±32.12%, p=0.318).ConclusionConventional TLIF and minimal TLIF with pedicle screw fixation showed good slip reduction in patients with one level low-grade symptomatic isthmic spondylolisthesis. The slip percentage and reduction rate were similar in the conventional TLIF and minimal TLIF.