The study aim was to simulate oblique spinous process abutment (SPA) in cadaveric spines and determine how this affects coupled motion in the coronal plane. L4-S1 spinal segments from thirteen cadavers were loaded on a materials testing machine in pure compression at 1kN for 10 minutes. Reflective markers on the vertebral bodies were used to assess coronal motion using a motion analysis system. Oblique SPA was simulated by attaching moulded oblique aluminium strips to the L4 and L5 spinous processes. In each specimen, both a right- and left-sided SPA was simulated, in random order, and compression at 1kN was again applied. All tests were then repeated after endplate fracture. Coronal plane motion at baseline was compared with values following simulated SPA using Mann Whitney U-tests. Pre-fracture, SPA increased coronal motion by 0.28° and 0.34° on right and left sides respectively, compared to baseline, only the former was significant (P=0.03). Post-fracture, SPA decreased coronal motion by 0.36° and 0.46° on right and left sides respectively, only the latter was significant (P=0.03). Simulated oblique SPA in the intact spine initiated an increase in coronal motion during pure axial loading. These findings provide limited evidence that oblique SPA may be causative in DLS

Hip instability is one of the most common causes for total hip arthroplasty (THA) revision surgery. Studies have indicated that lumbar fusion (LF) surgery is a risk factor for hip dislocation. Instrumented spine fusion surgery decreases pelvic tilt, which might lead to an increase in hip motion to accommodate this postural change. To the best of our knowledge, spine-pelvis-hip kinematics during a dynamic activity in patients that previously had both a THA and LF have not been investigated. Furthermore, patients with a combined THA and LF tend to have greater disability. The purpose was to examine spine-pelvis-hip kinematics during a sit to stand task in patients that have had both THA and LF surgeries and compare it to a group of patients that had a THA with no history of spine surgery. The secondary purpose was to compare pain, physical function, and disability between these patients. This cross-sectional study recruited participants that had a combined THA and LF (n=10; 6 females, mean age 73 y) or had a THA only (n=11; 6 females, mean age 72 y). Spine, pelvis, and hip angles were measured using a TrakSTAR motion capture system sampled at 200 Hz. Sensors were mounted over the lateral thighs, base of the sacrum, and the spinous process of the third lumbar,12th thoracic, and ninth thoracic vertebrae. Participants completed 10 trials of a standardized sit-to-stand-to-sit task. Hip, pelvis, lower lumbar, upper lumbar, and lower thoracic sagittal joint angle range of motion (ROM) were calculated over the entire task. In addition, pain, physical function, and disability were measured with clinical outcomes: Hip Disability Osteoarthritis Outcome Score (pain and physical function), Oswestry Low Back Disability Questionnaire (disability), and Harris Hip Score (pain, physical function, motion). Physical function performance was measured using 6-Minute Walk Test, Stair Climb Test, and 30s Chair Test. Angle ROMs during the sit-to-stand-to-sit task and clinical outcomes were compared between THA+LF and THA groups using independent t-tests and effect sizes (d). The difference in hip ROM was approaching statistical significance (p=0.07). Specifically, the THA+LF group had less hip ROM during the sit-to-stand-to-sit task than the THA only group (mean difference=11.17, 95% confidence interval=-1.13 to 23.47), which represented a large effect size (d=0.83). There were no differences in ROM for pelvis (p=0.54, d=0.28) or spinal (p=0.14 to 0.97; d=0.02 to 0.65) angles between groups. The THA+LF group had worse clinical outcomes for all measures of pain, physical function, and disability (p=0.01 to 0.06), representing large effect sizes (d=0.89 to 2.70). Hip ROM was not greater in the THA+LF group, and thus this is unlikely a risk factor for hip dislocation during this specific sit-to-stand-to-sit task. Other functional tasks that demand greater excursions in the joints should be investigated. Furthermore, the lack of differences in spinal and pelvis ROM were likely due to the task and the THA+LF group had spinal fusions at different levels. Combined THA+LF results in worse clinical outcomes and additional rehabilitation is required for these patients

We describe the clinical results of a technique of direct pars repair stabilised with a construct that consists of a pair of pedicle screws connected with a modular link that passes beneath the spinous process. Tightening the link to the screws compresses the bone grafted pars defect providing rigid intrasegmental fixation. 20 patients aged between 9 and 21 years were included in this prospective study. Each of the patients had high activity levels and suffered from significant back pain without radicular symptoms or signs. Patients had either no or grade I spondylolisthesis. Definitive pseudoarthrosis and fracture were confirmed via computerize tomography (CT). Magnetic resonance imaging was performed in every patient to assess the adjacent disc spaces which demonstrated normal signal intensity. A midline incision was used for surgery. The pars interarticularis defect was exposed and filled with autologous iliac crest bone graft prior to screw insertion. After screw insertion, a link was contoured to fit, and placed just caudal to the spinous process, deep to the interspinous ligament of the affected level, and attached to each pedicle screw. There was early mobilization post-operatively without a brace. The average inpatient stay was 3 days. Post-operative complications included 1 superficial wound haematoma and two superficial wound infections which responded to antibiotic treatment. Follow-up was at 6 weeks, 6 months and at 18 months, and 24 months. Clinical assessments for all patients was via the Oswestry disability index (ODI) and visual analogue scores (VAS). At the latest follow-up, 18 out of the 20 patients showed a significant (p<0.05) improvement in their ODI and VAS scores. The mean post-operative ODI score was 8%. All patients had radiographs and CT scans which showed fusion rates of 80% in those patients followed up for a minimum of 24 months. This new technique for direct pars repair demonstrates high fusion rates in addition provides the possible benefits of maintaining adjacent level motion. Clinically this group had good-to excellent functional outcomes as indicated by visual analogue scales and the Oswestry Disability Index in 18 out of 20 patients studied with a minimum follow-up of 2 years

The accuracy of pedicle screw placement is essential for successful spinal reconstructive surgery. The authors of several previous studies have described the use of image-based navigational templates for pedicle screw placement. These are designed based on a pre-operative computed tomographic (CT) image that fits into a unique position on an individual's bone, and holes are carefully designed to guide the drill or the pedicle probe through a pre-planned trajectory. The current study was conducted to optimise navigational template design and establish its designing method for safe and accurate pedicle screw placement. Thin-section CT scans were obtained from 10 spine surgery patients including 7 patients with adolescent idiopathic scoliosis (AIS) and three with thoracic ossification of the posterior longitudinal ligament (OPLL). The CT image data were transferred to the commercially available image-processing software and were used to reconstruct a three-dimensional (3D) model of the bony structures and plan pedicle screw placement. These data were transferred to the 3D-CAD software for the design of the template. Care was taken in designing the template so that the best intraoperative handling would be achieved by choosing several round contact surfaces on the visualised posterior vertebral bony structure, such as transverse process, spinous process and lamina. These contact surfaces and holes to guide the drill or the pedicle probe were then connected by a curved pipe. STL format files for the bony models with planned pedicle screw holes and individual templates were prepared for rapid prototype fabrication of the physical models. The bony models were made using gypsum-based 3D printer and individual templates were fabricated by a selective laser melting machine using commercially pure titanium powder. Pedicle screw trajectory of the bony model, adaptation and stability of the template on the bony model, and screw hole orientation of the template were evaluated using physical models. Custom-made titanium templates with adequate adaptation and stability in addition to proper orientation of the screw holes were sterilised by autoclave and evaluated during surgery. During segmentation, reproducibility of transverse and spinous processes were inferior to the lamina and considered inadequate to select as contact surfaces. A template design with more bone contact area might enhance the stability of the template on the bone but it is susceptible to intervening soft tissue and geometric inaccuracy of the template. In the bony model evaluation, the stability and adaptation of the templates were sufficient with few small round contact surfaces on each lamina; thus, a large contact surface was not necessary. In clinical patients, proper fit for positioning the template was easily found manually during the operation and 141/142 screws were inserted accurately with 1 insignificant pedicle wall breach in AIS patient. This study provides a useful design concept for the development and introduction of custom-fit navigational template for placing pedicle screws easily and safely

The purpose of this research was to determine the feasibility of radiostereometric analysis (RSA) as a diagnostic tool for assessing non-union following spinal arthrodesis procedures. Further, to estimate clinical thresholds for precision and accuracy of the proposed method in the cervical and lumbar spine. A three-level lumbo-sacral and a four-level cervical posterior arthrodesis procedures were performed on an artificial spine model (Sawbones, WA). Using a spring loaded inserter (RSA Biomedical, Sweden), eight to ten RSA markers were placed within each of the L4 and L5 segments in the spinous process (L4 only), lamina, transverse processes, posterior and anterior (down the pedicle) wall of the vertebral body. Eight to ten markers were placed within the proximal sacrum (S1) at the medial and lateral crests, tuberosity, and within the sacral canal wall. Four to eight RSA markers were placed into the C3-C6 lateral masses. Titanium screws and rods were applied to the spinal segments. Identical procedures were then performed on a cadaveric spine using similar bead placement and hardware. RSA imaging consisted of 12 double exams (24 exams) of the cervical and lumbar regions for both the Sawbones and cadaveric spine to assess precision of measurement under zero-displacement conditions. The most distal vertebrae were considered the datum against which the movement of all other vertebrae was compared. The artificial spine was then dismantled for accuracy assessment in which the middle vertebrae (L5 and C4-C5) were moved relative to the superior (L4 and C3) and inferior (S1 and C6) vertebrae by known, incremental displacements on an imaging phantom device. Displacements occurred along the superior-inferior, anterior-posterior, and flexion-extension (rotational) axes of motion. RSA images were obtained at each displacement. Image analysis was performed using model-based software (RSACore v3.41, Leiden, Netherlands) to visualize implanted RSA beads in 3-D space. Precision was defined as the 95% confidence interval of error in measuring zero-displacement. Accuracy was defined as the mean difference (with 95% confidence interval) between the known and measured displacement. The rate of RSA bead detection was high with 5–8 implanted beads being visible in both the lumbar and cervical regions of the artificial and cadaveric spines. Translational RSA precision for both spines was better than 0.25 mm and 0.82 mm for the lumbar and cervical regions, respectively. Rotational precision was better than 0.40° and 1.9° for the lumbar and cervical regions, respectively. RSA accuracy for the artificial spine overall demonstrated less than 0.11 mm translational bias (margin < ±0.02 mm) and less than 0.22° rotational bias (margin < ±0.15°). This study demonstrates that RSA achieves sufficient precision and accuracy to detect intervertebral micromotion for the purpose of assessing arthrodesis. Well dispersed RSA bead placement is critical to achieving sufficient accuracy as well as avoiding occlusion by metal hardware. Cervical bead implantation is particularly sensitive to bead clustering due to small vertebrae size and proximity to critical structures. The results of this work will aid in the development of a clinical study to assess arthrodesis in patients

INTRODUCTION. Mal-positioning of the acetabular component in total hip replacement (THR) could lead to edge loading, accelerated component wear, impingement and dislocation [1,2]. In order to achieve a successful position for the acetabular component, the assessment of the acetabular orientation with reference to different coordinate systems is important [3]. The aims of the present study were to establish a pelvic coordinate system and a global body coordinate system, and to assess the acetabular orientations of natural hips with reference to the two coordinate systems. METHODS. Three-dimensional (3D) computed tomographic (CT) images of 56 subjects (28 males and 28 females) lying supine were obtained from a public image archive (Cancer Image Archive, website: . www.cancerimagingarchive.net. ). 3D solid models of pelvis and spine were generated from the CT images. Two coordinate systems, pelvic and global body coordinate systems, were established. The pelvic coordinate system was established based on four bony landmarks on the pelvis: the bilateral anterior superior iliac spines (RASIS and LASIS) and the bilateral pubic tubercles (RPT and LPT). The global body coordinate system was generated based on the bony landmarks on the spine: the geometric centers of five lumbar vertebrae bodies and the most dorsal points of five corresponding spinous processes, as well as the anterior sacral promontory (Fig 1a and 1b). The acetabular rim plane was obtained by fitting a set of point along the acetabular rim to a plane using least squares method. The acetabular orientation was defined as the three coordinate components (x-, y- and z- components) of the unit normal vector of the acetabular rim plane in the two coordinate systems (Fig. 1c). RESULTS. Statistically significant differences of y- and z- components of the unit normal vector of the acetabular rim plane were calculated in the two coordinate systems (p<0.05). However, no significant difference of x- components was found (p=0.22) (Fig. 2). The differences of y- and z- components of the unit normal vector between the two coordinate system measurements were positive for most subjects. In addition, the differences and their standard deviations were larger for females compared to those for males (Fig. 3). DISCUSSION. Significantly different acetabular orientations were measured in the two coordinate systems, with larger variations in the global body coordinate system. The statistical analysis indicates that the different orientations measured in the two coordinate systems are primarily attributed to the pelvic tilt in the sagittal plane. The results also indicates that there was a trend of forward inclination of pelvis for most subjects considered in the present study and that the females generally have larger forward inclination and greater variation of pelvic tilt compared to males. SIGNIFICANCE. The study suggested that the consideration of pelvic tilt in THR placement is necessarily required in order to achieve a successful positioning of THR component with respect to the biomechanical axis of the body

Introduction. Kinematics analyses of the spine have been recognized as an effective method for functional analysis of the spine. CT is suitable for obtaining bony geometry of the vertebrae but radiation is a clinical concern. MRI is noninvasive but it is difficult to detect bone edges especially at endplates and processes where soft tissues attach. Kinematics analyses require tracking of solid bodies; therefore, bony geometry is not always necessary for kinematics analysis of the spine. This study aimed to develop a reliable and robust method for kinematics analysis of the spine using an innovative MRI-based 3D bone-marrow model. Materials and Methods. This IRB-approved study recruited 17 patients undergoing lumbar decompression surgery to treat a single-level symptomatic herniation as part of a clinical trial for a new dynamic stabilization device. T1 & T2 sagittal MRI scans were acquired as part of the pre-operative evaluation in three positions: supine and with the shoulders rotated 45° to the left and right to induce torsion of the lumbar spine. 3D bone-marrow models of L5 and S1 at the neutral and rotated positions were created by selecting a threshold level of the bone-marrow intensity at bone-marrow/bone interface. Validated 3D-3D registration techniques were used to track movements of L5 and S1. Segmental movements at L5/S1 during torsion were calculated. Results. Bone-marrow models were created not only in the vertebral body but also in superior/inferior, transverse and spinous processes, pedicles and laminae. Segmental rotation (mean±SD) at L5/S1 was shown to be symmetric for both left and right motions (p=0.149; Left: 1.04°±0.93° and Right: 1.33°±0.80°). The range of motion recorded was: left [0.05°-3.70°] and right [0.35°-3.25°]. These values were equivalent to previously reported values of axial lumbar rotation measured by 3D CT lumbar models. Conclusions. This study demonstrated feasibility of kinematic analyses using the 3D bone-marrow model created with clinical MRI. The bone-marrow model shows the bone-marrow/bone interface geometry –the internal structure of the vertebra rather than outside geometry usually used for kinematic analyses– that is easily and consistently detected due to its high-contrast interface MRI intensity, which does not require lengthy manual tracing of the bony contour. The bone-marrow model includes key elements of the vertebra including posterior elements and the 3D-3D registration technique used for 3D-CT model can be applied (Fig.1). This type of methodology can be used in the clinic to evaluate with sufficient accuracy subject-specific spinal kinematics without exposure to additional radiation. The MRI-based 3D bone-marrow model may also be useful for kinematic analyses of other major joints such as hip, knee, ankle and shoulder joints

Study Design. A prospective cohort study was carried out looking at the functional outcome and post-procedure translational segmental instability after multi-level lumbar decompression using a Hinge osteotomy technique. Objective. The Hinge osteotomy technique involves unilateral subperiosteal muscle dissection with osteotomy of the base of the spinous processes thereby preserving the integrity of the posterior elements. The objective of this study was to demonstrate the results of this technique clinically and radiologically. Methods. Between February 2005 and February 2007, 120 patients (51 male and 69 female) diagnosed with degenerative and/or congenital lumbar stenosis with a mean age of 64 years, underwent central and bilateral canal decompression using the hinge osteotomy technique. A mean of 2 segments (range 2-4) was decompressed. All patients were followed up for a minimum of three years. Five outcome measures were used: visual analogue scale for leg pain, Likert scale for functional status, symptom specific well-being score, general well-being score, and ODI score. The outcome measures were recorded pre-operatively and at 6 months and 3 years post-operatively. Successful surgical outcome was defined as an improvement in at least four out of five outcome measures. Results. 108 patients (90%) had a successful surgical outcome. There was a statistically significant improvement in all outcome criteria (p< 0.001) when measured at the 6-month post-operative mark as compared to pre-operatively, with further marginal significant improvement (p< 0.05) at 3 years post-surgery. There was no evidence of progressive lumbar segmental instability at 3 years post-operatively. Conclusion. Decompression of multi-level lumbar spine stenosis using the unilateral approach with the Hinge osteotomy technique is a safe approach for multi-level stenosis, with good outcome and no evidence of significant segmental translational spinal instability

The posterior midline approach used in spinal surgery has been associated with a significant rate of wound dehiscence. This study investigates anatomical study of the arterial supply of the cervical and thoracic spinal muscles and overlying skin at each vertebral level. It aimed to provide possible anatomical basis for such wound complications. A dissection and angiographic study was undertaken on 8 cadaveric neck and posterior torso from 6 embalmed and 2 fresh human cadavers. Harvested cadavers were warmed and hydrogen peroxide was injected into the major arteries. Lead oxide contrast mixture was injected in stepwise manner into the subclavian and posterior intercostal arteries of each specimen. Specimens were subsequently cross-sectioned at each vertebral level and bones elevated from the soft tissue. Radiographs were taken at each stage of this process and analysed. The cervical paraspinal muscles were supplied by the deep cervical arteries, transverse cervical arteries and vertebral arteries. The thoracic paraspinal muscles were supplied by the superior intercostal arteries, transverse cervical arteries and posterior intercostal arteries. In the thoracic region, two small vessels provide the longitudinal connection between the segmental arteries and in the cervical region, deep cervical arteries provide such connection from C3 to C6. The arterial vessels supplying the paraspinal muscles on the left and right side anastomose with each other, posterior to the spinous processes in all vertebral levels. At cervical vertebral levels, source arteries travel near the surgical field and are not routinely cauterised; Haematoma is postulated to be the cause of wound complications. At thoracic levels, source arteries travel in the surgical field and tissue ischemia is a contributing factor to wound complications, especially in operations over extensive levels. Post-operative wound complications is a multi-factorial clinical problem, the anatomical findings in this study provide possible explanations for wound dehiscence in the posterior midline approach. It is postulated that drain tubes may reduce the incidence of haematoma in the cervical level

Pedicle screws fixation to stabilise lumbar spinal fusion is the gold standard for posterior stabilisation. Pedicle screws are today positioned in free hand or under fluoroscopic guidance with an error from 20% up to 40–50%, which can determine the inefficacy of treatment or severe damages to close neurologic structures. Surgical navigation drastically increases screws placement accuracy. However its clinical application is limited due to cost reasons and troubles related to the presence of a localiser in the OR and the need to perform a registration procedure before surgery. An alternative image guided approach is the use of patient specific templates similar to the ones used for dental implants or knee prosthesis. Until now, the proposed solutions allow to guide the drill, and in some cases, as templates fit completely around vertebra, they require the complete removal of soft tissues on a large portion of the spine, so increasing intervention invasiveness. To reduce the soft tissue demolition, some authors proposed a fitting based on small “V shape” contact points, but these solutions can determine instability of the template and the reacting of wrong stable positions. In our solution, after spine CT acquisition, each vertebra is segmented using a modified version of ITK-SNAP software, on which the surgeon plans screws positioning and finally the template is designed around the chosen trajectories, using a tool which allows to insert cylinders (full or empty) in the segmented images. Each template, printed in ABS, contains two hollow cylinders, to guide the screws, and multiple contact points on the bone surface, for template stabilisation. We made an in-vitro evaluation on synthetic spine models (by Sawbones) to study different template designs. During this first step an ongoing redesign allowed to obtain an optimal template stability and an easy template positioning to minimise the intervention invasiveness. A first contact point, which fits on the sides of the spinous process, is used to simplify template alignment. The other 4 contact points, which consists of cylinders (diameter 5 mm), fit exactly on spine surface in correspondence to the vertebra's lamina and articular processes to stabilise the template in an unique position. Templates can be used to guide not only the drill, but also Kirschner wires, to guide cannulated screws. After the Kirschner wires insertion the template can be dismounted for its removal (the direction of the kirschner wires are not parallel). After the definitive template design an ex-vivo animal test on 2 porcine specimens has been conducted to evaluate template performance in presence of soft-tissue in place. The specimens have been scanned with CT, we realised a total of 14 templates and we performed the insertion of 28 Kirschner wires. We evaluated that after the soft tissue dissection and the bone exposure, the template can be easily positioned in the right unique position, with no additional tissue removal compared to the traditional approach, requiring just removal of the soft tissue under the small contact points using an electric cutter. The surgeon evaluated (and corrected) some wrong stable template positions when not all the contact points were in contact with the bone surface. The post-op evaluation was made with a CT scan that showed 1 cortical pedicle violation (3.5%) (grade II according to the FU classification)

We report the results of six trauma and orthopaedic projects to Kenya in the last three years. The aims are to deliver both a trauma service and teaching within two hospitals; one a district hospital near Mount Kenya in Nanyuki, the other the largest public hospital in Kenya in Mombasa. The Kenya Orthopaedic Project team consists of a wide range of multidisciplinary professionals that allows the experience to be shared across those specialties. A follow-up clinic is held three months after each mission to review the patients. To our knowledge there are no reported outcomes in the literature for similar projects.

A total of 211 operations have been performed and 400 patients seen during the projects. Most cases were fractures of the lower limb; we have been able to follow up 163 patients (77%) who underwent surgical treatment. We reflect on the results so far and discuss potential improvements for future missions.