Purpose. A change in lumbar lordosis can affect the outcome following lumbar fusion, and intraoperative positioning is a prime determinant of the postoperative lordosis. The purpose of this study is to determine the change in lordosis and sacral slope (SS) following axial lumbar interbody fusion (AxiaLIF). Method. We retrospectively reviewed 81 patients who underwent a 360 lumbar interbody fusion at L4-5/L5-S1 (two-level procedure) or solely at L5-S1 (one-level) for degenerative disc disease and spondylolithesis utilizing the AxiaLIF with posterior segmental instrumentation. For the two-level procedures, 25 patients had the AxiaLIF placed first and 27 had pedicle screws placed first. For the one-level procedures, 11 patients had the AxiaLIF placed first and 18 had pedicle screws placed first. Standing lateral preoperative radiographs were compared to standing lateral postoperative films. Lumbar Cobb angles were measured at L1-S1, L4-S1 and individual lumbar levels. SS was measured for sacral version. Results. Of the 81 patients studied, 29 underwent one-level AxiaLIF, and 52 underwent two-level AxiaLIF. For the two-level population, there were statistically significant changes (P less than 0.05) in Cobb angles pre- vs. postoperative at the L4-S1, L2-3, and L4-5 levels, but none other. The percent lordosis from L4-S1 pre- vs. postoperative was also noted to be significant. The pre- vs. postoperative Cobb angle comparisons for the one-level population were not found to be significant. The percentages having a greater than or equal to 10 degree change in total lordosis and lordosis from L4-S1 in both one- and two-level groups were similar at ∼20%. There was no difference in either group in percentage having a greater than or equal to five degree change at individual lumbar segments although there was a trend at both L5-S1 and the SS towards less change with the pedicle screws placed first. Conclusion. A significant portion of both single and multilevel fusions with AxiaLIF had a statistically significant change at the L4-5 and L4-S1 levels. In general, there is a small decrease in lordosis at the bottom two segments and SS with reciprocal changes at the proximal levels. The percentage of total lordosis from the L4-S1 level decreased significantly in the multilevel group. Roussouly lordosis type three (well-balanced) was relatively protected from change in lordosis. Placing pedicle screws prior to placing the AxiaLIF in one- and two- level procedures may lead to an improved sagittal alignment. Further observation of this cohort will determine if the change in alignment will impact outcomes or accelerate adjacent level disease

Obesity is an increasing public health concern associated with increased perioperative complications and expense in lumbar spine fusions. While open and mini-open fusions such as transforaminal lumbar interbody fusion (TLIF) and minimally invasive TLIF (MIS-TLIF) are more challenging in obese patients, new MIS procedures like oblique lateral lumbar interbody fusion (OLLIF) may improve perioperative outcomes in obese patients relative to TLIF and MIS-TLIF. The purpose of this study is to determine the effects of obesity on perioperative outcomes in OLLIF, MIS-TLIF, and TLIF. This is a retrospective cohort study. We included patients who underwent OLLIF, MIS-TLIF, or TLIF on three or fewer spinal levels at a single Minnesota hospital after conservative therapy had failed. Indications included in this study were degenerative disc disease, spondylolisthesis, spondylosis, herniation, stenosis, and scoliosis. We measured demographic information, body mass index (BMI), surgery time, blood loss, and hospital stay. We performed summary statistics to compare perioperative outcomes in MIS-TLIF, OLLIF, and TLIF. We performed multivariate regression to determine the effects of BMI on perioperative outcomes controlling for demographics and number of levels on which surgeries were operated. OLLIF significantly reduces surgery time, blood loss, and hospital stay compared to MIS-TLIF, and TLIF for all levels. MIS-TLIF and TLIF do not differ significantly except for a slight reduction in hospital stay for two-level procedures. On multivariate analysis, a one-point increase in BMI increased surgery time by 0.56 ± 0.47 minutes (p = 0.24) in the OLLIF group, by 2.8 ± 1.43 minutes (p = 0.06) in the MIS-TLIF group, and by 1.7 ± 0.43 minutes (p < 0.001) in the TLIF group. BMI has positive effects on blood loss for TLIF (p < 0.001) but not for OLLIF (p = 0.68) or MIS-TLIF (p = 0.67). BMI does not have significant effects on length of hospital stay for any procedure. Obesity is associated with increased surgery time and blood loss in TLIF and with increased surgery time in MIS-TLIF. Increased surgery time may be associated with increased perioperative complications and cost. In OLLIF, BMI does not affect perioperative outcomes. Therefore, OLLIF may reduce the disparity in outcomes and cost between obese and non-obese patients

Transforaminal lumbar interbody fusion (TLIF) using an implanted cage is the gold standard surgical treatment for disc diseases such as disc collapse and spinal cord compression, when more conservative medical therapy fails. Titanium (Ti) alloys are widely used implant materials due to their superior biocompatibility and corrosion resistance. A new Ti-6Al-4V TLIF cage concept featuring an I-beam cross-section was recently proposed, with the intent to allow bone graft to be introduced secondary to cage implantation. In designing this cage, we desire a clear pathway for bone graft to be injected into the implant, and perfused into the surrounding intervertebral space as much as possible. Therefore, we have employed shape optimization to maximize this pathway, subject to maintaining stresses below the thresholds for fatigue or yielding. The TLIF I-beam cage (Fig. 1(a)) with an irregular shape was parametrically designed considering a lumbar lordotic angle of 10°, and an insertion angle of 45° through the left or right Kambin's triangles with respect to the sagittal plane. The overall cage dimensions of 30 mm in length, 11 mm in width and 13 mm in height were chosen based on the dimensions of other commercially available cages. The lengths (la, lp) and widths (wa, wp) of the anterior and posterior beams determine the sizes of the cage's middle and posterior windows for bone graft injection and perfusion, so they were considered as the design variables for shape optimization. Five dynamic tests (extension/flexion bending, lateral bending, torsion, compression and shear compression, as shown in Fig. 2(b)) for assessing long term cage durability (10. 7. cycles), as described in ASTM F2077, were simulated in ANSYS 15.0. The multiaxial stress state in the cage was converted to an equivalent uniaxial stress state using the Manson-Mcknight approach, in order to test the cage based on uniaxial fatigue testing data of Ti-6Al-4V. A fatigue factor (K) and a critical stress (σcr) was introduced by slightly modifying Goodman's equation and von Mises yield criterion, such that a cage design within the safety design region on a Haigh diagram (Fig. 2) must satisfy K ≤ 1 and σcr ≤ SY = 875 MPa (Ti-6Al-4V yield strength) simultaneously. After shape optimization, a final design with la = 2.30 mm, lp = 4.33 mm, wa = 1.20 mm, wp = 2.50 mm, was converged upon, which maximized the sizes of the cage's windows, as well as satisfying the fatigue and yield strength requirements. In terms of the strength of the optimal cage design, the fatigue factor (K) under dynamic torsion approaches 1 and the critical stress (σcr) under dynamic lateral bending approaches the yield strength (SY = 875 MPa), indicating that these two loading scenarios are the most dangerous (Table 1). Future work should further validate whether or not the resulting cage design has reached the true global optimum in the feasible design space. Experimental validation of the candidate TLIF I-beam cage design will be a future focus. For any figures or tables, please contact authors directly (see Info & Metrics tab above).

Study design. Prospective randomized study. Objective. Primary aim of this study was to compare clinical and radiological results of transforaminal lumbar interbody fusion (TLIF) with posterolateral (interlaminar) instrumented lumbar fusion (PLF) in adult low grade (Meyerding 1 & 2) spondylolisthesis patients. Background data. Theoretically, TLIF has better radiological result than PLF in spondylolisthesis in most of the studies. Method. 24 patients of low grade adult spondylolisthesis were randomly allocated to one of the two groups: group 1- PLF and group 2-TLIF. Study period was between August 2010 to March 2013. All patients were operated by a single surgeon (CN). Posterior decompression was performed in all patients. Average follow up period was 18.4 months. Quality of life was accessed with Visual analogue scale and Oswestry Low Back Pain Disability Index. Fusion was assessed radiologically by CT scan and X-ray. Result. Though fusion was significantly better in TLIF group, clinical outcome including relief of back pain and neurogenic claudication were better in PLF group. Rate of complication was also lower in PLF group. Conclusion. Considering the low complication rate and similar or better clinical results, posterolateral instrumented lumbar fusion is the better option in low grade adult spondylolisthesis

Nowadays many new minimally invasive techniques are experienced to perform lower lumbar interbody fusion in attempt to decrease the complications related to open anterior approach. AxiaLIF (axial lumbar interbody fusion) system is a percutaneous transacral approach that exploits the virtual presacral retroperitoneal space to perform annulus-sparing discectomy and interbody instrumented fusion of lower lumbar disc spaces. Additioning posterior percutaneous instrumentation, a robust axial construct is placed which restores disc height, sagittal balance and lordosis with minimal muscle dissection, blood loss and postoperative pain. Via fluoroscopically-guided approach, AxiaLIF procedure creates a presacral retroperitoneal corridor in the midline through a paracoccigeal skin incision of 2-3 cm. This space is void of neuro-vascular major elements. A safe working cannula is put in and docked in the S1-S1 entry level and a transacral channel is realized gaining the central space of the disc. A 360° annulus-sparing radial discectomy is performed with special cutters even in case of collapsed disc space and the bone graft is inserted. The following screwing of AxiaLIF rod restores disc height via distraction if necessary, decompresses the neural foramen indirectly and undertakes instantaneous rigid fixation of adjacent vertebral bodies. Using the same incision point and trajectory through the presacral space as AxiaLIF, it is possible to realized a similar procedure L4-S1 vertebral fusions called AxiaLIF 2L. Between february 2009 and may 2010 25 patients (16F:9M) affected by degenerative disc disease (17) and grade 1 or 2 spondylolisthesis (8) were included in this study. Evaluated outcomes were the amount of bleeding, the presence of presacral hematoma, the functional recovery time, the surgery time rate, the x-ray time rate, the complication rate (infection, pelvic visceral injury, postoperative pain). 21 of 25 patients underwent AxiaLIF L5-S1 procedures, 4 of these with a stand alone implant and 17 followed by posterior instrumentation. In the remaining 4 patients, a AxiaLIF 2L L4-S1 procedures is performed. 4 of 25 patients had a perioperative suction drenage. Mean operative time for L5-S1 AxiaLIF procedure was 49 minutes. A 2. nd. p.o.d. CT pelvic scan of undrained and drained groups showed a mean presacral hematoma of 45 cc and 17 cc respectively reduced one month later to a mean value of 19 cc and 3 cc. Hemoglobin rate mainly reduced of 1,7 g/dL between pre and postoperative time. At one month all patients improved their quality of life significantly but one had a gluteal pain. No patient had perioperative infections or pelvic visceral injuries or required blood transfusions. This study seems to assess that AxiaLIF procedure is a minimally invasive lower spine techique actually. The presacral hematoma presence seems to have no side effect and it may be prevented by perioperative drainage. More large studies are needed to confirm our results

Background. It is known that severe cases of intervertebral disc (IVD) disease may lead to the loss of natural intervertebral height, which can cause radiating pain throughout the lower back and legs. To this point, surgeons perform lumbar fusion using interbody cages, posterior instrumentation and bone graft to fuse adjacent vertebrae together, thus restoring the intervertebral height and alleviating the pain. However, this surgical procedure greatly decreases the range of motion (ROM) of the treated segment, mainly caused by high cage stiffness. Additive manufacturing can be an interesting tool to reduce the cage's elastic modulus (E), by adding porosity (P) in its design. A porous cage may lead to an improved osteointegration since there is more volume in which bone can grow. This work aims to develop a finite element model (FEM) of the L4-L5 functional spinal unit (FSU) and investigate the loss of ROM induced by solid and porous cages. Materials and Methods. The Intact-FEM of L4-L5 was created, which considered the vertebrae, IVD and ligaments with their respective material properties. 1. The model was validated by comparing its ROM with that of other studies. Moments of 10 Nm were applied on top of L4 while the bottom of L5 was fixed to simulate flexion, extension, lateral bending and axial rotation. 2. The lumbar cages, posterior instrumentation and bone graft were then modelled to create the Cage-FEMs. Titanium was chosen for the instrumentation and cages. Cages with different stiffness were considered to represent porous structures. The solid cage had the highest modulus (E. 0. =110 GPa, P. 0. =0%) whereas the porous cages were simulated by lowering the modulus (E. 1. =32.8 GPa, P. 1. =55%; E. 2. =13.9 GPa, P. 2. =76%; E. 3. =5.52 GPa, P. 3. =89%; E. 4. =0.604 GPa, P. 4. =98%), following the literature. 3. The IVD was removed in Cage-FEMs to allow the implant's insertion [Fig. 1] and the previous loading scenarios were simulated to assess the effects of cage porosity on ROM. Results. The Intact-FEM presents acceptable ROM according to experimental and numerical studies, as shown by the red line in Figure 2. After insertion, lower ROM values in Cage-FEMs are measured for each physiological movement [Fig. 3]. In addition, highly porous cages have greater ROM, especially in axial rotation. Discussion. Significant reduction of ROM is expected after cage insertion because the main goal of interbody fusion is to allow bone growth. As such, the procedure's success is highly dependent on segmental stability, which is achieved by using cages in combination with bone graft and posterior instrumentation. Furthermore, higher cage porosities seem to affect the FSU. In fact, ROM increases more as the cage modulus approaches that of the cancellous bone (E. canc-bone. =0.2 GPa. 1. ). Next step will be to assess the effects of cage design on the L4-L5 FSU mechanical behavior and stress distribution. To conclude, additive manufacturing offers promising possibilities regarding implant optimization, being able to create porous cages, thus reducing their stiffness. For any figures or tables, please contact the authors directly

Purpose. Degenerative changes of the lumbar motion segment often lead to stenosis of the spinal canal or neuroforamen. Axial lumbar interbody fusion (AxiaLIF) is intended to indirectly increase and stabilize foraminal dimensions by restoring disc height in patients with degenerative disc disease, thereby relieving axial and radicular pain. Therefore, this study investigated the effects of AxiaLIF on anterior disc height, posterior disc height, foraminal height and foraminal width as well as to determine the effectiveness of this minimally-invasive technique for indirect decompression and restoration of disc height. Method. Eighty-one patients who underwent a 360 degree lumbar interbody fusion at L4-S1 and L5-S1 with AxiaLIF between November 2008 and May 2010 and satisfied all inclusion criteria were included. The preoperative and three-month postoperative digital radiographs were reviewed and analyzed. Disc heights were measured in the planes of the anterior and posterior surfaces of the adjacent vertebral bodies. Foraminal height was measured as the maximum distance between the inferior margin of the pedicle of the superior vertebra and the superior margin of the pedicle of the inferior vertebra. Foraminal width was measured as the shortest distance between the edge of the superior facet of the caudal vertebra and the posterior edge of inferior endplate of the cranial vertebra. Potential magnification error between pre- and post-operative radiographs was corrected using the anterior vertebral height of L5 vertebra. Results. Our study shows that there is a mean increase of 42.0% in posterior disc height (PDH) at L4-5 and 21.5% in anterior disc height (ADH) at L4-5 and PDH mean increase of 33.6% and 16.3% in ADH at L5-S1 in two-level AxiaLIF cases. Similarly the mean change in foraminal height (FH) was 12.6% at L4-5 and 10.8% at L5-S1 in 2-levels AxiaLIF. The mean change in foraminal width (FW) at L4-L5 was 19.9% and 29.1% at L5-S1 in 2-levels AxiaLIF. In the single level AxiaLIF group, the mean change in PDH was 43.1%, the ADH change was 17.5%, the average change in FH was 14.4%, and mean change in FW was 25.3%. The change is reflected as a percentage of the preoperative value. All changes from preoperative to postoperative values were statistically significant. Conclusion. AxiaLIF appears to be an effective minimally invasive device to increase disc height and neuroforaminal area. Our findings appear equivalent to anterior lumbar interbody fusion and transforaminal lumbar interbody fusion in terms of indirect decompression and increase in disc height. This, in combination with the added benefit of preserving the annulus, anterior longitudinal ligament, and posterior longitudinal ligament, suggests the AxiaLIF is an excellent alternative for this patient population. However, additional follow-up studies are necessary to confirm the long-term ability of the implant to maintain fusion and preserve the improvements in disc and foraminal area

Aims

The aim of this paper is to describe the impact of COVID-19 on spine surgery services in a district general hospital in England in order to understand the spinal service provisions that may be required during a pandemic.