Cervical spine
Abstract. Objectives. While spinal fusion is known to be associated with adjacent disc degeneration, little is known on the role of the facet joints in the process, and whether their altered biomechanics following fusion plays a role in further spinal degeneration. This work aimed to develop a model and method to sequentially measure the effects of spinal fusion on lumbar facet joints through synchronisation of both motion analysis, pressure mapping and mechanical analysis. Methods. Parallel measurements of mature ovine lumbar facet joints (∼8yr old, n=3) were carried out using synchronised load and displacement measurements, motion capture during loading and pressure mapping of the joint spaces during loading. Functional units were prepared and cemented in PMMA endcaps. Displacement-controlled compression measurements were carried out using a materials testing machine (3365, Instron, USA) at 1 mm/min up to 950 N with the samples in a neutral position, while motion capture of the facet joints during compression was carried out using orthogonal HD webcams (Logitech, Switzerland) to measure the displacement of key facet joint features. The pressure mapping of load transfer during displacement was carried out using a flexible pressure sensor (6900 series, Tekscan, USA). Each sample was imaged at an isotropic resolution of 82 microns using a μCT scanner (XtremeCT, Scanco, Switzerland) to quantify the curvature within the facet joints. Results. Relative facet joint displacement under load, in a neutral position, showed more displacement (2.36 ±1.68 mm) compared to the cross-head when under compression (2.06 ±1.19 mm). Motion capture indicated the relative displacement of the facet joints was more posterior with some lateral motion. For five of the six facet joints, pressure measurement was possible only on 24±7 % of the surface due to the large change in curvature. Partially measured loads through the
Summary. Nucleotomy almost doubles the transmitted forces on the facet joints in human lumbar spine, regardless of the amount of removed nucleus pulposus. Introduction. Low back pain involves the lumbar facet joints in 15% to 45% of the cases. The surgical intervention, nucleotomy, might also lead to painful
Background. Surgical resection of middle
Introduction. Anteromedial gonarthrosis is a common well described pattern of knee osteoarthritis with cartilage wear beginning in the anteromedial quadrant of the medial tibial plateau in the presence of an intact and functioning ACL. It is well known that mechanical factors such as limb alignment and meniscal integrity affect the progression of arthritis and there is some evidence that the morphology of the tibial plateau may be a risk factor in the development of this disease. The extension
Facet joint osteoarthritis (FJOA) is a prominent clinical hallmark of degenerative spine disorders. During disease progression, cartilage and subchondral bone tissues undergo increased turnover and remodeling. The structural changes to the subchondral tissue of FJOA have not been studied thus far. In this study, we performed a micro computed tomography (µCT) study of the subchondral cortical plate (SCP) and trabecular bone (STB) in FJOA and determined osteoarthritis-specific alterations. Twenty-four patients (11 male, 13 female, median age 65) scheduled for decompression and stabilization surgery for degenerative spinal stenosis were included in this study. FJOA specimens were harvested during surgery and analyzed by µCT. Bone volume fraction (BV/TV), trabecular thickness (Tb.Th), trabecular separation (Tb.Sp) and trabecular number (Tb.N) were evaluated using CT Analyser. Lumbar facet joints without chondropathy from cadaveric specimens (9 male, 6 female, median age 57) served as healthy controls. Age-, gender- and disease-specific effects were identified by ANOVA (Introduction
Methods
Displaced intraarticular calcaneal fractures are debilitating injuries with significant socioeconomic and psychological effects primarily affecting patients in active age between 30 and 50 years. Recently, minimally and less invasive screw fixation techniques have become popular as alternative to locked plating. The aim of this study was to analyze biomechanically in direct comparison the primary stability of 3 different cannulated screw configurations for fixation of Sanders type II-B intraarticular calcaneal fractures. Fifteen fresh-frozen human cadaveric lower limbs were amputated mid-calf and through the Chopart joint. Following, soft tissues at the lateral foot side were removed, whereas the medial side and Achilles tendon were preserved. Reproducible Sanders type II-B intraarticular fracture patterns were created by means of osteotomies. The proximal tibia end and the anterior-inferior aspect of the calcaneus were then embedded in polymethylmethacrylate. Based on bone mineral density measurements, the specimens were randomized to 3 groups for fixation with 3 different screw configurations using two 6.5 mm and two 4.5 mm cannulated screws. In Group 1, two parallel longitudinal screws entered the tuber calcanei above the Achilles tendon insertion and proceeded to the anterior process, and two transverse screws fixed the posterior
The use of intraoperative navigation and robotic surgery for minimally invasive lumbar fusion has been increasing over the past decade. The aim of this study is to evaluate postoperative clinical outcomes, intraoperative parameters, and accuracy of pedicle screw insertion guided by intraoperative navigation in patients undergoing lumbar interbody fusion for spondylolisthesis. Patients who underwent posterior lumbar fusion interbody using intraoperative 3D navigation since December 2021 were included. Visual Analogue Scale (VAS), Oswestry Disability Index (ODI), and Short Form Health Survey-36 (SF-36) were assessed preoperatively and postoperatively at 1, 3, and 6 months. Screw placement accuracy, measured by Gertzbein and Robbins classification, and facet joint infringement, measured by Yson classification, were assessed by intraoperative Cone Beam CT scans performed at the end of instrumentation. Finally, operation time, intraoperative blood loss, hospital stay, and screw insertion time were evaluated. This study involved 50 patients with a mean age of 63.7 years. VAS decreased from 65.8±23 to 20±22 (p<.01). ODI decreased from 35.4%±15 to 11.8%±14 (p<.01). An increase of SF-36 from 51.5±14 to 76±13 (p<.01) was demonstrated. The accuracy of “perfect” and “clinically acceptable” pedicle screw fixation was 89.5% and 98.4%, respectively. Regarding
Conventional TKA surgery attempts to restore patients to a neutral alignment, and devices are designed with this in mind. Neutral alignment may not be natural for many patients, and may cause dissatisfaction. To solve this, kinematical alignment (KA) attempts to restore the native pre-arthritic joint-line of the knee, with the goal of improving knee kinematics and therefore patient's function and satisfaction. Proper prosthetic trochlea alignment is important to prevent patella complications such as instability or loosening. However, available TKA components have been designed for mechanical implantation, and concerns remain relating the orientation of the prosthetic trochlea when implants are kinematically positioned. The goal of this study is to investigate how a currently available femoral component restores the native trochlear geometry of healthy knees when virtually placed in kinematic alignment. The healthy knee OAI (Osteoarthritis Initiative) MRI dataset was used. 36 MRI scans of healthy knees were segmented to produce models of the bone and cartilage surfaces of the distal femur. A set of commercially available femoral components was laser scanned. Custom 3D planning software aligned these components with the anatomical models: distal and posterior condyle surfaces of implants were coincident with distal and posterior condyle surfaces of the cartilage; the anterior flange of the implant sat on the anterior cortex; the largest implant that fitted with minimal overhang was used, performing ‘virtual surgery’ on healthy subjects. Software developed in-house fitted circles to the deepest points in the trochlear grooves of the implant and the cartilage. The centre of the cartilage trochlear circle was found and planes, rotated from horizontal (0%, approximately cutting through the proximal trochlea) through to vertical (100%, cutting through the distal trochlea) rotated around this, with the axis of rotation parallel to the flexion
Treatment of comminuted intraarticular calcaneal fractures remains controversial and challenging. Anatomic reduction with stable fixation has demonstrated better outcomes than nonoperative treatment of displaced intraarticular fractures involving the posterior
Trochlear geometry of modern femoral implants is designed for mechanical alignment (MA) technique for TKA. The biomechanical goal is to create a proximalised and more valgus trochlea to better capture the patella and optimize tracking. In contrast, Kinematic alignment (KA) technique for TKA respects the integrity of the soft tissue envelope and therefore aims to restore native articular surfaces, either femoro-tibial or femoro-patellar. Consequently, it is possible that current implant designs are not suitable for restoring patient specific trochlea anatomy when they are implanted using the kinematic technique, this could cause patellar complications, either anterior knee pain, instability or accelerated wear or loosening. The aim of our study is therefore to explore the extent to which native trochlear geometry is restored when the Persona. ®. implant (Zimmer, Warsaw, USA) is kinematically aligned. A retrospective study of a cohort of 15 patients with KA-TKA was performed with the Persona. ®. prosthesis (Zimmer, Warsaw, USA). Preoperative knee MRIs and postoperative knee CTs were segmented to create 3D femoral models. MRI and CT segmentation used Materialise Mimics and Acrobot Modeller software, respectively. Persona. ®. implants were laser scanned to generate 3D implant models. Those implant models have been overlaid on the 3D femoral implant model (generated via segmentation of postoperative CTs) to replicate, in silico, the alignment of the implant on the post-operative bone and to reproduce in the computer models the features of the implant lost due to CT metal artefacts. 3D models generated from post-operative CT and pre-operative MRI were registered to the same coordinate geometry. A custom written planner was used to align the implant, as located on the CT, onto the pre-operative MRI based model. In house software enabled a comparison of trochlea parameters between the native trochlea and the performed prosthetic trochlea. Parameters assessed included 3D trochlear axis and anteroposterior offset from medial
Summary Statement. Spinal flexibility in bending and axial torque has been shown to exhibit very modest changes with advancing disc degeneration. This study is the first to address the possible relationship in pure anterior shear and no clear relationship was observed. Introduction. Disc degeneration (DD) is a risk factor for low back pain. Stable or unstable spine segments may be treated with an isolated decompression or instrumented stabilization, respectively. The effect of DD on spinal flexibility has been addressed by several groups in bending but not in shear; a highly relevant load direction in the lumbar spine is anterior shear. The objective of our study was to determine the effect of DD on anterior translation and specimen stiffness under shear loading in an in vitro model of degenerative spondylolisthesis. Methods. Magnetic resonance images were obtained for human cadaveric lumbar FSUs (N=30). Disc degeneration was assessed with the Pfirrmann five-point grading scale. Three surgeons independently graded the discs and the grade common to at least two of the surgeons was assigned to that specimen. Each specimen was then tested in three sequential states: intact,
Abstract. Objectives. Catastrophic neck injuries in rugby tackling are rare (2 per 100,000 players per year) with 38% of these injuries occurring in the tackle. The aim of this study was to determine the primary mechanism of cervical spine injury during rugby tackling and to highlight the effect of tackling technique on intervertebral joint loads. Methods. In vivo and in vitro experimental data were integrated to generate realistic computer simulations representative of misdirected tackles. MRI images were used to inform the creation of a musculoskeletal model. In vivo kinematics and neck muscle excitations were collected during lab-based staged tackling of the player. Impact forces were collected in vitro using an instrumented anthropometric test device during experimental simulations of rugby collisions. Experimental kinematics and muscle excitations were prescribed to the model and impact forces applied to seven skull locations (three cranial and four lateral). To examine the effects of technique on intervertebral joint loads the model's neck angle was altered in steps of 5° about each rotational axis resulting in a total of 1,623 experimentally informed simulations of misdirected tackles. Results. Neck flexion angles and cranial impact locations had the largest effects on maximal compression, anterior shear and flexion moment loads. During posterior cranial impacts compression forces and flexion moments increased from 1500 to 3200 N and 30 to 60 Nm respectively between neck angles of 30° extension and 30° flexion. This was more evident at the C5-C6 and C6-C7 joints. Anterior shear loads remained stable throughout neck angle ranges however during anterior impacts they were directed posteriorly when the neck was flexed. Conclusions. The combination of estimated joint loads in the lower cervical spine support buckling as the primary injury mechanism of anterior bilateral
In six unloaded cadaver knees we used MRI to determine the shapes of the articular surfaces and their relative movements. These were confirmed by dissection. Medially, the femoral condyle in sagittal section is composed of the arcs of two circles and that of the tibia of two angled flats. The anterior
Advancements in treating complex distal radius fractures. We will review tips and tricks in the treatment of complex articular distal radius fractures. We will discuss the treatment of carpal instability resulting from fracture of the volar marginal fragment. We will cover optimizing surgical exposure to address fractures extending from the radial styloid to the lunate
Constitutional knee varus increases the risk of medial OA disease due to increase in the knee adduction moment and shifting of the mechanical axis medially. Hueter-Volkmann’s law states that the amount of load experienced by the growth plate during development influences the bone morphology. For this reason, heightened sports activity during growth is associated with constitutional varus due to added knee adduction moment. In early OA, X-rays often show a flattened medial femoral condyle extension
There has been only one limited report dating from 1941 using dissection which has described the tibiofemoral joint between 120° and 160° of flexion despite the relevance of this arc to total knee replacement. We now provide a full description having examined one living and eight cadaver knees using MRI, dissection and previously published cryosections in one knee. In the range of flexion from 120° to 160° the flexion
Background. Finite element (FE) models have become a standard pre-clinical tool to study biomechanics of spine and are used to simulate and evaluate different strategies in scoliosis treatment: examine their efficacy as well as the effect of different implant design parameters. The goal of this study is to investigate, in a system of rods and laminar wires, the effect of the number of wires and their pre-stress on whole spine stiffness. Methods. A generic FE model was developed to represent a full human spine, including vertebrae, intervertebral discs, ligaments,
At our district general hospital in the southwest of England, around 694 total knee replacements (TKR) are performed annually. Since spring 2013 we have been using an enhanced recovery protocol for all TKR patients, yet we have neither assessed compliance with the protocol nor whether its implementation has made a discernible and measurable difference to the delivery of care in this patient population. Enhanced recovery after surgery (ERAS) protocols are multi-modal care pathways designed to aid recovery. They are based on best evidence and promote a multi-disciplinary approach which standardises care and encompasses nutrition, analgesia and early mobilisation throughout the pre, intra and postoperative phases of an inpatient stay. ERAS has been found to reduce length of stay (LOS), readmission rates and analgesic requirements following surgery. 1, 2, 3. Additionally, they have been shown to improve range of knee movement following TKR and improve mobility, patient satisfaction whilst reducing mortality and morbidity. 4, 5, 6. With these benefits in mind, we sought to investigate how well our trauma and orthopaedic department was complying with a local ERAS protocol and whether we could replicate the benefits seen within the literature. Following approval from our local audit office in September 2015 we generated a patient list of elective TKR patients under the same surgeon before and after the implementation of the ERAS protocol. Using discharge summaries and patient notes we extracted data for 39 patients operated on prior to the ERAS implementation between January 2011 and December 2012 and 27 patients following its introduction between January 2014 and September 2015. Data collected included length of stay, time to discharge from inpatient physiotherapy and use of analgesia and antiemetics. Alongside this we audited the compliance with all