Sacral Axis Research Articles

Minimally Invasive Postero-Inferior Sacroiliac Joint Fusion: Surgical Technique and Procedural Details.

(1) Background: Minimally invasive sacroiliac joint (SIJ) fusion is the preferred surgical intervention to treat chronically severe pain associated with SIJ degeneration and dysfunction. (2) Methods: This paper details the ten-step surgical procedure associated with the postero-inferior approach using the PsiF™ DNA Sacroiliac Joint Fusion System. (3) Results: The posterior surgical approach with an inferior operative trajectory (postero-inferior) utilizes easily identifiable landmarks to provide the safest, most direct access to the articular joint space for transfixing device placement. Implanting the device through the subchondral bone provides maximum fixation and stabilization of the joint by utilizing an optimal amount of cortical bone-implant interface. Approaching the joint from the inferior trajectory also places the implant perpendicular to the S1 endplate at a "pivot point" near the sacral axis of rotation, which addresses the most significant motion of the joint. (4) Conclusions: Further observational data from real-world clinical use are encouraged to further validate this procedure as the surgical preference for minimally invasive SIJ fusion.

COMPARISON OF ANTERIOR VERSUS POSTERIOR PELVIC TILT ON LUMBAR LORDOSIS

The pelvic girdle and spine vertebral column work as a long chain influenced by pelvic tilt. Spinal deformities or other musculoskeletal conditions may cause patients to compensate with excessive pelvic tilt, producing alterations in the degree of lumbar lordosis and subsequently causing pain. The objective of this study is to assess the effect of open and closed chain anterior or posterior pelvic tilt on lumbar spine kinematics using an in vitro cadaveric spine model.Three human cadaveric spines with intact pelvis were suspended with the skull fixed in a metal frame. Optotrak 3D motion system tracked real-time coordinates of pin markers on the lumbar spine. A force-torque digital gage applied consistent force to standardize the acetabular or sacral axis’ anterior and posterior pelvic tilt during simulated open and closed chain movements, respectively.In closed chain PPT, significant differences in relative intervertebral compression existed between L1/L2 [-2.54 mm] and L5/S1 [-11.84 mm], and between L3/L4 [-2.78 mm] and L5/S1 [-11.84 mm] [p <.05]. In closed chain APT, significant differences in relative intervertebral decompression existed between spinal levels L1/L2 [2.87mm] and L5/S1[24.48 mm] and between L3/L4 [2.94 mm] and L5/S1 [24.48 mm] [p <.05]. In open chain APT, significant differences in relative intervertebral decompression existed between spinal levels L4/L5 [1.53mm] and L5/S1 [25.14 mm] and between L2/L3 [1.68 mm] and L5/S1 [25.14 mm] [p<.05 for both]. Displacement during closed chain PPT was significantly greater than during open chain PPT, whereas APT showed no significant differences.In PPT, open chain pelvic tilts did not produce as much lumbar intervertebral displacement compared to closed chain. In contrast, APT saw no significant differences between open and closed chain. Additionally, results illustrate the increase in lumbar lordosis during APT and the loss of lordosis during PPT.

Minimally Invasive Inferior Intra-Articular Sacroiliac Joint Fusion: Successful Application of Osseous Stabilization Using Allograft Bone.

Minimally invasive sacroiliac joint (SIJ) fusion is the preferred surgical method for managing patients with recalcitrant, chronically severe SIJ pain and dysfunction refractory to conservative medical measures. The primary surgical objective of all minimally invasive SIJ fusion procedures is to provide immediate stabilization within the joint space to support osseous consolidation and the development of a mechanically solid arthrodesis. The intra-articular surgical approach to the SIJ with allograft bone placement utilizes a trajectory and easily identifiable landmarks that allow the surgeon to control the risk of violating important neuro-vascular structures. The intra-articular approach can employ a superior or inferior operative trajectory, with the former restricted to allograft placement in the ligamentous portion of the SIJ. The inferior approach utilizes decortication to surgically create a channel originating in the purely articular portion of the joint space allowing for truly intra-articular implant placement within the osseous confines of the ilium and sacrum. Positioning the implant along the natural joint line and securing it within the underlying sub-chondral bone, mortise and tenon fashion provides stabilization and large surface area contact at the bone implant interface. The inferior, intra-articular approach also places the implant perpendicular to the S1 endplate, near the sacral axis of rotation, which addresses the most significant biomechanical forces across the joint. Short-term, post-surgical observational data from a 57 patient multi-center registry using the inferior, intra-articular approach show uniform and statistically significant improvement in all clinical outcomes (p < 0.001 for all comparisons), including an average 3-point improvement in back pain severity from 6.8 preoperatively to 3.8 at 6 months. Further clinical evaluation with longer-term follow-up of the inferior, intra-articular SIJ fusion procedure is encouraged.

Assessment of Cervical and Lumbar Kinematics in Simulated Open and Closed Kinetic Chain.

The pelvic girdle and spine vertebral column work as a long chain influenced by pelvic tilt. This study aims to assess the effect of open and closed chain anterior pelvic tilt (APT) or posterior pelvic tilt (PPT) on cervical and lumbar spine kinematics using an in vitro cadaveric spine model. Three human cadaveric spines with intact pelvis were suspended with the skull fixed in a metal frame. Optotrak 3-dimensional motion system captured coordinates of pin markers at 24 different points for real-time tracking of cervical and lumbar regions. Additional geometric parameters were measured to calculate pelvic incidence and pelvic tilt. A force-torque digital gauge applied consistent force to standardize the acetabular or sacral axis' APT and PPT during simulated open- and closed-chain movements, respectively. In closed-chain PPT, significant differences in relative intervertebral decompression were noted between spinal levels C2/C3 (4.85 mm) and C5/C6 (1.26 mm), while compression was noted between L1/L2 (-2.54 mm) and L5/S1 (-11.84 mm) and between L3/L4 (-2.78 mm) and L5/S1 (-11.84 mm) (P < 0.05). Displacement during closed-chain PPT was significantly greater than during open-chain PPT for cervical and lumbar spines. In closed-chain APT, significant differences in relative intervertebral decompression were noted between spinal levels L1/L2 (2.87 mm) and L5/S1 (24.48 mm) and between L3/L4 (2.94 mm) and L5/S1 (24.48 mm) (P < 0.05). Pelvic incidence remained the same as the pelvis tilted anterior and posterior. In PPT, open-chain pelvic tilts did not produce as much cervical and lumbar intervertebral displacement compared with closed-chain pelvic tilts. In contrast, APT saw fewer differences between open- and closed-chain tilting. There was a reciprocal relationship between pelvic tilt and sacral slope, producing a constant pelvic incidence throughout all pelvic tilt angles. The results of this study may help determine how a patient's pelvic tilt is causing pain and using that knowledge to guide rehabilitation of stabilizing muscles. The data produced here may also be helpful in determining which rehabilitation exercises may be more difficult or prone to injury for patients with either excessive anterior or posterior pelvic tilt.

Motion capture evaluation of sagittal spino-pelvic biomechanics after lumbar spinal fusion.

The spine and pelvis coexist as a dynamic linked system in which spinal and pelvic parameters are correlated. Investigation of this system can inform the understanding and treatment of spinal deformity. Here, we demonstrate the use of motion capture technology to measure spine biomechanical parameters using a novel testing apparatus. Three complete cadaveric spines with skull and pelvis were mounted into a biomechanical testing apparatus. Each lumbar vertebra was monitored by motion capture cameras as the spines underwent maximal anterior and posterior pelvic tilts about two sagittal axes at a controlled speed and applied force. These axes were defined as the sacral axis which passes transversely through the ilium and S1, and the acetabular axis which passes transversely through both acetabula. The experiments were repeated after L4-L5 fusion, and then, after both L4-L5 and T12-S1 fusion with pedicle screw instrumentation. Data were collected for total range of motion and for coupled translation at each functional spinal unit (FSU). Total range of motion and coupled translation within functional spinal units (FSUs) was decreased after spinal fusion. The displacement of each individual FSU was captured and summarized along with the observed patterns under each experimental condition. Lumbar fusion decreases spinal motion in the sagittal plane in both overall ROM and individual coupled translations of lumbar vertebrae. This was demonstrated using motion capture technology which is useful for quantifying the translations of individual FSUs in a multisegmental spinal model.

Chronic and Acute Low Back Pain and Its Relationship to the Sacral X-Axis, Leg Length Changes, Sciatica, Abdominal Pain, Idiopathic Scoliosis, and Incontinence

Several interactive pelvic axes occur during activities of weight-bearing and ambulation. Flexion and extension of the symmetrical innominates occur on the sacral x-axis with weight-bearing. Normal asymmetric innominate rotation occurs on the innominate axis at the pubic symphysis during weight-bearing with normal ambulation. Oblique sacral movement occurs on an oblique sacral axis concurrent with asymmetric innominate movement. Acute and chronic low back pain is commonly caused by a bilateral symmetrical or oblique anterior innominate rotation on the sacrum on an acetabular axis, usually while lifting, bending, lowering, shoveling, sweeping, a pendulous abdomen, during pregnancy, or with a postural forward head. The innominates are caused to sublux slightly cephalad and laterally on the sacral x-axis at the posterior inferior iliac spine (PIIS). This is a measurable movement that puts a rotational shear on the bilateral sacral x-axis and separates the sacral origins of both the gluteus maximus and the piriformis from their ileal origins resulting in pain across the mid-buttocks into the trochanter, down the tensor fascia lata into the lateral knee causing piriformis syndrome, pain across the buttock from the PIIS to the trochanter, a sciatic neuritis or a pseudosciatica. In all probability, true sciatica is probably not from the disc but rather caused where the sciatic nerve exits just below or sometimes through the compromised piriformis. A specific abdominal pain may also accompany acute or chronic low back pain as may an idiopathic scoliosis. An associated posterior movement of the ischial tuberosities can approximate the distal sacrum, loosen muscles of the pelvic floor, decrease kinetic tension on the sacrotuberous ligaments, and cause some degree of incontinence. Dysfunction is all initiated at the sacral x-axes. This is corrected effectively simply with a manual bilateral posterior innominate rotation that reverses all and various symptoms leaving the patient free of pain. Many areas of dysfunction are described, but not all.

Combination of degenerative lumbar spinal stenosis and spinal deformity. Literature review

The study objective is to analyze currently available publications on spinal deformity in patients with degenerative lumbar spinal stenosis.Materials and methods. We analyzed 90 manuscripts published between 1980 and 2017.Results. We describe the parameters used to assess spinal deformity and evaluate their role for predicting the course of degenerative spinal disease. We provide the results of latest studies assessing the impact of spinal deformity on the outcome of surgical treatment in patients with degenerative lumbar spinal stenosis. We identified the following risk factors for scoliosis progression: wedge-shaped intervertebral disc in the frontal projection, low middle sacral axis, lateral spondylolisthesis, small L vertebral body, vertebral rotation, Cobb angle &gt;20°, and sagittal imbalance.Conclusion. We recommend decompressive interventions with facet joint preservation in patients with spinal deformity and degenerative lumbar spinal stenosis with no risk factors for scoliosis progression and radicular symptoms only (without pronounced low back pain). In patients with no risk factors for scoliosis progression, radicular symptoms, and low back pain, it is advisable to combine decompression with short fixation. For individuals at risk of scoliosis progression, we recommend supplementing decompression with long fixation exceeding scoliosis curve.

Die Architektur der Ka-Anlage Pepis I. in Tell Basta

The ancient city of Bubastis is shaped by an urban and sacral axis in its central area. The eastern part of this axis leads through the Great Temple while the western part ends in the Ka-enclosure of Pepi I. This Ka-enclosure contains a sanctuary, which is surrounded by a big yard. The measuring unit used for the planning and building of this construction was the royal cubit. Performed analyses suggest that the royal cubit was used for the shaping of the yard, the erecting of the sanctuary and for other parts of the construction. Based on the analysis of the measurements, reconstruction of the sanctuary was possible. The latter consists of a portal, an inner courtyard, a double portico and additional five small rooms. The structure of the Ka-enclosure suggests that the valley temple of the Bent Pyramid in Dahshur has been used as a model. Additional considerations of the plans of Habachi indicate that the sanctuary was reconstructed several times. At a later stage, the site was predominantly used for economic purposes. Since the time of the Saitic dynasty, the site also included a cemetery.

Accuracy Analysis of Pedicle Screw Placement in Posterior Scoliosis Surgery

The accuracy of pedicle screw placement was evaluated in posterior scoliosis surgeries with or without the use of computer-assisted surgical techniques. In this retrospective cohort study, the pedicle screw placement accuracy in posterior scoliosis surgery was compared between conventional fluoroscopic and computer-assisted surgical techniques. There has been no study systemically analyzing the perforation pattern and comparative accuracy of pedicle screw placement in posterior scoliosis surgery. The 45 patients who received posterior correction surgeries were divided into 2 groups: Group C, manual control (25 patients); and Group N, navigation surgery (20 patients). The average Cobb angles were 73.7 degrees and 73.1 degrees before surgery in Group C and Group N, respectively. Using CT images, vertebral rotation, pedicle axes as measured to anteroposterior sacral axis and vertebral axis, and insertion angle error were measured. In perforation cases, the angular tendency, insertion point, and length abnormality were evaluated. The perforation was observed in 11% of Group C and 1.8% in Group N. In Group C, medial perforations of left screws were demonstrated in 8 of 9 perforated screws and 55% were distributed either in L1 or T12. The perforation consistently occurred in pedicles in which those axes approached anteroposterior sacral axis within 5 degrees . The average insertion errors were 8.4 degrees and 5.0 degrees in Group C and Group N, respectively, which were significantly different (P < 0.02). The medial perforation in Group C occurred around L1, especially when pedicle axis approached anteroposterior sacral axis. This consistent tendency was considered as the limitation of fluoroscopic screw insertion in which horizontal vertebral image was not visible. The use of surgical navigation system successfully reduced the perforation rate and insertion angle errors, demonstrating the clear advantage in safe and accurate pedicle screw placement of scoliosis surgery.

The Inverted Napoleon's Hat Sign

Spondylolisthesis is the anterior displacement of one vertebra with respect to another and frequently occurs at the lumbosacral junction. The inverted Napoleon’s hat sign is produced when a severely subluxed L5 vertebral body (the dome of the hat) projects end-on and overlaps the sacrum, with the superimposition of images appearing as an inverted Napoleon hat (Fig 2). In the absence of a spondylolysis pars interarticularis defect or spondylolisthesis, the presence of a marked hyperlordosis at the lumbosacral junction may also simulate the appearance of the inverted Napoleon hat. The anterior slip of the L5 vertebra on S1 and the resulting L5-S1 kyphosis are counterbalanced by hyperlordosis of the lumbar spine and increased verticalization of the sacrum resulting from a compensatory hamstring contracture and uprighting of the pelvis around the hip joints (2). These factors contribute to deformities seen in spondylolisthesis and are accompanied by the potential over time to develop a pressure erosion of the anterior aspect of S1 and the posterior portion of the L5 vertebral body. In the standing position, the center of gravity normally passes through the lumbosacral joint, causing the vertebral column to slide anteriorly on the intervertebral disk at this level. The lumbosacral junction resists anterior dislocation because of the stabilization provided by the anterior longitudinal ligament, the posterior bands of the iliolumbar ligaments, and the articular facet joints (3). The facet joint anatomy normally helps prevent slippage on the anteroinferiorly directed sacral promontory at the lumbosacral junction by means of the inferior articular facets of L5, which are anteriorly oriented and engage the posteriorly directed S1 articular facets (3). An approximately 140° angle normally exists between L5 and the sacral axis, along with a 40° angle of the S1 body from the horizontal, thereby contributing to the large amount of force imposed onto the superior articular processes of S1 (3). Notable disruption of any of these stabilizing forces may result in depiction of the inverted Napoleon’s hat sign.

Radiologic usefulness of hysterosalpingography after bladder filling.

Berlin,Germany) was slowly injected, routine spot radiographs (anteroposterior.both oblique and latera] views) were obtained with fluoroscopic guidance. An additional anteroposterior view was obtained after instillation of 200 ml of saline solution into the bladder through a Foley catheter. For data analysis.the patientswere arbitrarily divided into two groups: anterior and posterior. The anteriorgroup was defined as the patients whose uterine axis was anterior to the sacral axis on the lateral view, and the posterior group was defined as the patients whose uterine axis was posterior to the sacral axis. Hysterosalpingograms before and after bladder filling were comparedfor changein uterine heightandchangein conspicuity of uterine abnormalities. Uterine height was measured from the fundus to the cervicoisthmic junction of the uterus on the anteroposterior view. Change in uterine height was assigned a uterine height ratio (after bladder