Cadaver Experiments Research Articles

The Role of Deep Deltoid Ligament in Ankle Fracture Stability: A Biomechanical Cadaveric Study

Category:Ankle; Basic Sciences/Biologics; TraumaIntroduction/Purpose:Supination-external rotation (SER) injuries make up 80% of all ankle fractures. SER stage 2 injuries (AITFL and Weber B) are considered stable. SER stage 3 injury includes disruption of the posterior malleolus (or PITFL). In SER stage 4 there is either medial malleolus fracture or deltoid injury. SER 4 injuries have been considered unstable, requiring surgery. The deltoid ligament is a key component of ankle stability, but clinical tests to assess deltoid injury have low specificity. This biomechanical cadaveric study specifically investigates the role of the components of the deep deltoid ligament in the stabillity of SER ankle fractures.Methods:In the first phase of the study, three specimens were utilised to standardise dissection of the deltoid ligament and creation and fixation of SER ankle fracture. In phase two, four matched pairs (8 specimens) were tested using this standardised protocol (Figure1). Specimens were sequentially tested for stability when axially loaded with a custom rig with up to 750N. Specimens were tested with: ankle intact; lateral injury (AITFL and Weber B); additional posterior injury (PITFL); additional anterior deep deltoid; additional posterior deep deltoid; lateral side ORIF. Clinical photographs and radiographs were recorded at each stage. In addition, dynamic stress radiographs were performed after sectioning the deep deltoid and following fracture fixation to assess talar tilt in eversion.Results:All specimens behaved in an identical manner when subjected to this standardised protocol. When the posterior deep deltoid ligament was intact, the ankle remained stable when loaded and showed no talar tilt on dynamic stress test. Once the posterior deep deltoid ligament was sectioned, there was demonstrable instability in all specimens. Surgical stabilisation of the lateral side using standard technique with a plate prevented talar shift but not talar tilt. In adequately stabilised ankle specimens, there was no loss of fixation on axial loading.Conclusion:This biomechanical cadaveric experiment demonstrates that under the standardised test conditions, all SER fracture ankle specimens with an intact posterior deep deltoid ligament behaved as stable injuries. The posterior portion of the deep deltoid ligament is a crucial structure in conferring stability to SER stage 4 injuries. The clinical implication of this is that when the posterior deep deltoid ligament is intact, SER fractures may be managed without surgical intervention in a plantigrade cast. We also conclude that without immobilisation, the talus may tilt in the mortise risking long-term deltoid incompetence.

The feasibility for a novel minimally invasive surgery\u2013percutaneous endoscopic transforaminal lumbar interbody fusion (PE-TLIF) for the treatment of lumbar degenerative diseases: a cadaveric experiment

BackgroundThe objective of the study was to evaluate our innovative percutaneous endoscopic transforaminal lumbar interbody fusion (PE-TLIF) for the treatment of lumbar degenerative diseases.MethodsTwo fresh-frozen human cadavers with soft tissues were donated for the experiment. Both cadavers had no history of previous spine surgery. The PE-TLIF surgery was performed on 3 levels (L4-5 of the first one, and L3-4, L4-5 of the second one) in October 2015. The PE-TLIF technique mainly included the following aspects: primary guide pins and a specially designed superior articular process (SAP) guide insertion, working channel setup, endoscopic decompression and fusion, and pedicle screw implantation and fixation. Under the surveillance of C-arm fluoroscope, four primary guide pins were inserted. The inferior primary guide in the hypothetically symptomatic side was confirmed as the first guide pin. At the end of the first guide pin, the specially designed SAP guide was installed. The secondary guide pin was inserted in the SAP via self-designed SAP guide. Under the protection cannula, part of the superior articular process was removed by oriented SAP resection device, so the working channel was smoothly put through the Kambin’s triangle. The endoscope was inserted close to the exiting nerve root. Rotation of the working channel kept the nerve root out of it.ResultsThree levels of PE-TLIF were successfully performed in two cadavers. Self-designed SAP guide made the secondary guide pin inserting the SAP accurately. Decompression was adequate and the traversing nerve root was relieved. Three aimed intervertebral levels are implanted with two 7-mm-high PEEK cages and one expandable cage. The expandable cage could be adjusted from 8 mm to 13 mm. Surgical incisions included four 15 mm incisions for percutaneous screw fixation and one 12 mm incision for working channel. There was no nerve injury during the operations.ConclusionsOur present results showed that the novel minimally invasive surgery PE-TLIF was feasible for the treatment of lumbar degenerative diseases.

Tensor Veli Palatinopexy as a Novel Treatment for Eustachian Tube Dysfunction: A Cadaveric Feasibility Study.

To demonstrate the feasibility of a novel procedure whereby a suture is placed transorally in the tensor veli palatini muscle to tighten it, thereby dilating the cartilaginous portion of the eustachian tube (ET). The study design was a prospective cadaveric experiment to examine the feasibility of a novel treatment for ET dysfunction. Academic medical center in a research-oriented operating room with intraoperative computed tomography (CT) capabilities. Seven fresh-frozen cadaver heads were obtained, each of which was thawed for 36 hours prior to use. The preprocedural volumes of the cartilaginous ET were measured by filling the ET with an iodine-containing radiocontrast agent via the nasopharynx and then obtaining CT images. Submucosal flaps in the soft palate were raised, and sutures were placed in the tensor veli palatini bilaterally to increase tension. After completion of the procedure, contrast placement and CT imaging were repeated. Three-dimensional models of the ETs were created, and the volumes were measured and compared. Of the 14 ETs evaluated, 13 showed an increase in postprocedure volume. On average, postprocedure volumes showed a 57% increase from preprocedure volumes (mean relative change, 57.1%; P = .013). Placement of a tension-holding suture in the tensor veli palatini muscle can reliably dilate the cartilaginous portion of the ET. Such a procedure may be useful in the treatment of ET dysfunction.

237. Individual plates vs single plate for multilevel fixation results in superior biomechanics in anterior cervical fusion surgery

BACKGROUND CONTEXT Anterior cervical discectomy and fusion (ACDF) has been the gold standard surgical treatment for degenerative conditions of the cervical spine, including degenerative disc disease, cervical spondylotic myelopathy, and cervical disc prolapse. This procedure remains the preferred treatment technique particularly for more elderly patients or those with a contraindication to total disc replacement. Multilevel anterior cervical spine fusion with single plates are associated with hardware failure and screw pullout due to stress shielding and excessive loading. Given the lever arm of longer plates and multiple fusion surfaces, pseudarthrosis rates are higher than single level cases. The biomechanics of a new approach using segmental fixation versus convention fixation using a long plate is compared using computational modeling. PURPOSE To compare the biomechanics of multilevel cervical spine fixation using segmental plating versus single plating. STUDY DESIGN/SETTING Computational modeling using cadaver-validated finite element model of cervical spine PATIENT SAMPLE N/A OUTCOME MEASURES Biomechanical data including segmental range of motion and pull-out load on screws METHODS A cadaver-validated finite element (FE) model of C3-C7 spine was used. The model included all crucial anatomical components including, vertebral bones, intervertebral ligaments and connecting tissues, intervertebral disc, facet joints and uncinate processes. The model was validated by comparison of segmental range of motion against data obtained from a cadaver experiment of cervical spine. The validated model was then used to simulate the fixation across C4-C6 using anterior plating, screw and interbody fixation with PEEK cages following simulation of the surgical procedure including total annulectomy and removal of ACL ligaments and the index levels. Two surgical cases were simulated: fixation with two individual plates (each with three screws) vs fixation with single long plate and 6 screws. Anatomical loading of 70N compressive follower load plus 1.5Nm bending moment were applied to the constructs to simulate physiological flexion, extension, lateral bending and axial rotation motions. Segmental motion and screw load data were compared among constructs. RESULTS Fixation at the index levels resulted in significant reduction in range of motion with 60% reduction in extension,85% in left and right axial rotation (LR&RR),63% in left and right lateral bending (LB&RB) and 80% in flexion. The range of motion in the multi-plate construct was similar to the long plate construct in all loadings. At the upper adjacent segment, both constructs yielded a slight increase in ROM in flexion, extension and lateral bending motions (3-10%). The screws in the long plate construct had significantly greater pull out force ranging from 35-82N in extension versus 10-60N in the multi-plate constructs. In axial rotation the ranges of forces were 18-139N in long plate versus 15-70N in multi-plate constructs. The load ranges were similar in both constructs in flexion and lateral bending. CONCLUSIONS Cervical segmental plating allows the ability to treat each level individually yielding in improvement in ability of restoring natural lordosis and biomechanics. When instrumenting across more than one level in ACDF, the individual multi-plates demonstrate superior biomechanics versus the conventional single long plate constructs by ensuring load sharing versus stress shielding. The screw in segmental plating experience lower axial forces resulting in lower risk of screw pull-out post-surgery. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

P8. Biomechanical analysis of standalone lumbar interbody cages versus 360-degree constructs: an in vitro and finite element investigation

BACKGROUND CONTEXT Low fusion rates and cage subsidence have been reported as the main drawbacks of lumbar fixation with stand-alone interbody cages. However, recent new cage placement techniques preserve the spinal structures that contribute to spinal stability. The biomechanical effect of the addition of posterior instrumentation to interbody instrumented segment was evaluated using cadaver spine and validated computational model. PURPOSE To evaluate the mechanical support/stability of different interbody fixation techniques in lumbar spinal segments and the effect of posterior instrumentation support on altering kinematics and load sharing of stand-alone cage instrumented segments. STUDY DESIGN/SETTING A combined cadaveric and finite element (FE) modeling study. PATIENT SAMPLE N/A OUTCOME MEASURES Segmental range of motion and load sharing on vertebral endplate. METHODS An in vitro experiment using seven fresh human cadaveric spines was performed to test intact versus instrumented spines instrumented with stand-alone lateral interbody cages (LIF) and cage instrumented spine supplemented with posterior pedicle screw-rod fixation (360 construct). A Finite element (FE) model of L4-L5 motion segment was also created and validated against cadaveric kinematic data then used to simulate different surgical setting as in the in vitro experiment. The validated model was then used to evaluate the stability of stand-alone lateral (LIF), transforaminal (TLIF) and anterior (ALIF) fixation constructs. The stand-alone cage models were then stabilized with posterior instrumentation and reassessed. To simulate anatomical loading, all FE models of were subjected to a 400N compressive pre-load followed by an 8Nm bending moment. The segmental kinematics and the load sharing at the inferior endplate were computed and compared among cases. RESULTS The segmental ROM for the intact cadaveric segment was 3.1±0.9(Ext), 7.1±2.8(Flex), 5.0±1.7(LB), 5.0±2.1(RB), 2.6±1.8(LR), 2.4±1.7(RR) degrees. The FE model predicted ranges of motion close to the average and within one standard deviation of the cadaver experiment. For the LIF instrumented in vitro cases the motion ranged from 1.7±1.3 (Ext), 1.8±1.0 (Flex), 1.7±1.1 (LB), 1.7±1.0 (RB), 0.9±0.5 (LR), 1.3±0.9 (RR) for cage alone and 0.8±0.5 (Ext), 0.8±0.7 (Flex), 0.9±0.5 (LB), 0.8±0.4 (RB), 0.5±0.4 (LR), 0.6±0.3 (RR) for 360 construct cases. The predicted reduction in motion for ALIF and LIF stand-alone cage cases in axial rotation (AR) and lateral bending (LB) were similar to those with the addition of posterior instrumentation (∼90%). The reduction in sagittal motion for ALIF and LIF ranged from 66% to 86% while the corresponding value for the 360 construct was ∼90%. The peak stresses in extension for the LIF stand-alone cage were somewhat higher than the posterior instrumented cases, but not significant. Stresses for the ALIF cages were similar to the 360 construct designs. Stresses for the ALIF and LIF cages in LB and AR were similar to the posterior instrumented constructs. CONCLUSIONS Our data suggest that stand-alone cages using ALIF and LIF techniques are effective in providing stability primarily in AR and LB, at least under the controlled conditions analyzed in the present study. Clinical data will further define the role and application of stand-alone cages. This data further supports, that 360° stabilization with cage and posterior instrumentation provides maximum construct stability, irrespective of the surgical technique used for cage placement. FDA DEVICE/DRUG STATUS This abstract does not discuss or include any applicable devices or drugs.

C-arm orbits for metal artifact avoidance (MAA) in cone-beam CT

Metal artifacts present a challenge to cone-beam CT (CBCT) image-guided surgery, obscuring visualization of metal instruments and adjacent anatomy—often in the very region of interest pertinent to the imaging/surgical tasks. We present a method to reduce the influence of metal artifacts by prospectively defining an image acquisition protocol—viz., the C-arm source-detector orbit—that mitigates metal-induced biases in the projection data. The metal artifact avoidance (MAA) method is compatible with simple mobile C-arms, does not require exact prior information on the patient or metal implants, and is consistent with 3D filtered backprojection (FBP), more advanced (e.g. polyenergetic) model-based image reconstruction (MBIR), and metal artifact reduction (MAR) post-processing methods. The MAA method consists of: (i) coarse localization of metal objects in the field-of-view (FOV) via two or more low-dose scout projection views and segmentation (e.g. a simple U-Net) in coarse backprojection; (ii) model-based prediction of metal-induced x-ray spectral shift for all source-detector vertices accessible by the imaging system (e.g. gantry rotation and tilt angles); and (iii) identification of a circular or non-circular orbit that reduces the variation in spectral shift. The method was developed, tested, and evaluated in a series of studies presenting increasing levels of complexity and realism, including digital simulations, phantom experiment, and cadaver experiment in the context of image-guided spine surgery (pedicle screw implants). The MAA method accurately predicted tilted circular and non-circular orbits that reduced the magnitude of metal artifacts in CBCT reconstructions. Realistic distributions of metal instrumentation were successfully localized (0.71 median Dice coefficient) from 2–6 low-dose scout views even in complex anatomical scenes. The MAA-predicted tilted circular orbits reduced root-mean-square error (RMSE) in 3D image reconstructions by 46%–70% and ‘blooming’ artifacts (apparent width of the screw shaft) by 20–45%. Non-circular orbits defined by MAA achieved a further ∼46% reduction in RMSE compared to the best (tilted) circular orbit. The MAA method presents a practical means to predict C-arm orbits that minimize spectral bias from metal instrumentation. Resulting orbits—either simple tilted circular orbits or more complex non-circular orbits that can be executed with a motorized multi-axis C-arm—exhibited substantial reduction of metal artifacts in raw CBCT reconstructions by virtue of higher fidelity projection data, which are in turn compatible with subsequent MAR post-processing and/or polyenergetic MBIR to further reduce artifacts.

The Segond fracture occurs at the site of lowest sub-entheseal trabecular bone volume fraction on the tibial plateau.

In a series of human cadaveric experiments, Dr. Paul Segond first described the avulsion injury occurring at the anterolateral tibial plateau that later took his name. The fracture is thought to arise as a consequence of excessive tibia internal rotation which often also elicits damage to other connective tissue of the knee. The exact mechanism behind the avulsion is, however, unclear. A number of ligamentous structures have been proposed in separate studies to insert into the Segond fragment. Suggestions include the iliotibial band (ITB), biceps femoris and the controversial ‘anterolateral ligament’ (ALL). Despite increasing knowledge of tibial plateau bony microarchitecture in both healthy and disease states, no studies have yet, to our knowledge, considered the role of tibial sub‐entheseal bone structure in pathogenesis of the Segond fracture. The goal of this study was thus to elucidate the differences in trabecular properties at regions across the tibial plateau in order to provide an explanation for the susceptibility of the anterolateral region to avulsion injury. Twenty human tibial plateaus from cadaveric donors were dissected and imaged using a Nikon‐XTH225‐μCT scanner with <80 μm isotropic voxel size. Scans were reconstructed using MicroView 3D Image Viewer and Analysis Tool. Subsequent virtual biopsy at ten anatomically defined regions of interest (ROI) generated estimates of bone volume fraction (‘bone volume divided by total volume’ (BV/TV)). The overall mean BV/TV value across all 20 tibiae and all 10 ROIs was 0.271. Univariate repeated‐measurements ANOVA demonstrated that BV/TV values differed between ROIs. BV/TV values at the Segond site (Sα, Sβ or Sγ) were lower than all other ROIs at 0.195, 0.192 and 0.193, respectively. This suggests that, notwithstanding inter‐ and intra‐specimen variation, the Segond site tends to have a lower trabecular bone volume fraction than entheseal sites elsewhere on the tibia. Since BV/TV correlates with tensile and torsional strength, the lower BV/TV at the Segond site could equate to a region of local weakness in certain individuals which predisposes them to an avulsion injury following the application of force from excessive internal rotation. The low BV/TV recorded at the Segond site also challenges the idea that the fracture occurs due to pull from a discrete ‘anterolateral ligament’, as the tension exerted focally would be expected to elicit a hypertrophic response in line with Frost's Mechanostat hypothesis. Our data would instead agree with the aforementioned reports of the fibrous band at the Segond site being part of a broader insertion of an ‘anterolateral complex’.

Distal radioulnar joint stability measured with radiostereometry during the piano key test.

Distal radioulnar joint instability is difficult to grade by clinical examination and interobserver reliability is low. This study used a new and precise radiostereometry method for measurement of distal radioulnar joint translation. Eight human donor arms were positioned in a custom-made fixture and a standardized piano key test was done with pressure on the ulnar head. Examination was done before and after dividing the styloid and foveal insertions of the triangular fibrocartilage complex. In the intact wrists, the piano key test induced a mean 1.36 mm translation of the ulnar head, which increased statistically significantly to 1.96 mm after a lesion of the styloid ligament insertion and to 2.3 mm after combined lesions of the styloid and foveal ligament insertions. This experimental cadaver study demonstrates a radiological method for precise quantification of distal radioulnar joint stability after different grades of triangular fibrocartilage complex injury.

A novel method for near‐infrared fluorescence imaging of the urethra during perineal and transanal surgery: demonstration in a cadaveric model

Transanal total mesorectal excision is a promising novel sphincter-saving procedure for low rectal cancer. However, the transanal bottom-up dissection is associated with increased rates of iatrogenic urethral injuries. Near-infrared fluorescence (NIRF) imaging, given its deeper tissue penetration, has been explored in a limited number of studies for enhanced intra-operative urethral visualization. In this study, we explored the feasibility of a novel, ultrabright, biocompatible fluorescent polymer to coat urinary catheters for the purpose of intra-operative urethral visualization. In an ex vivo experiment, using a near-infrared laparoscope, the fluorescent signal of a coated catheter (near-infrared coating of equipment, NICE) was qualitatively and quantitatively compared to the signal of indocyanine green (ICG)/Instillagel® mixtures and ICG-filled catheters at several concentrations. Also, in three male human torsos, using fluorescent urinary catheters, NIRF-guided perineal dissections and a transanal total mesorectal excision were performed. Intra-operative NIRF-based urethral visualization was performed systematically. During the qualitative and quantitative fluorescence signal assessment, NICE-coated catheters were clearly superior to the ICG-based solutions. In the cadaveric experiments, enhanced urethral visualization was possible even at early stages of dissection, when the organ was covered by several tissue layers. NICE-coated catheters represent a promising potential to allow for NIRF-based intra-operative urethral visualization.

Effect of variations in tissue-level ductility on human vertebral strength.

Although the ductility of bone tissue is a unique element of bone quality and varies with age and across the population, the extent to which and mechanisms by which typical population-variations in tissue-level ductility can alter whole-bone strength remains unclear. To provide insight, we conducted a finite element analysis parameter study of whole-vertebral (monotonic) compressive strength on six human L1 vertebrae. Each model was generated from micro-CT scans, capturing the trabecular micro-architecture in detail, and included a non-linear constitutive model for the bone tissue that allowed for plastic yielding, different strengths in tension and compression, large deformations, and, uniquely, localized damage once a specified limit in tissue-level ultimate strain was exceeded. Those strain limits were based on reported (mean±SD) values from cadaver experiments (8.8±3.7% strain for trabecular tissue and 2.2±0.9% for cortical tissue). In the parameter study, the strain limits were varied by ±1 SD from their mean values, for a combination of nine analyses per specimen; bounding values of zero and unlimited post-yield strain were also modeled. The main outcomes from the finite element analysis were the vertebral compressive strength and the amount of failed (yielded or damaged) tissue at the overall structure-level failure. Compared to a reference case of using the mean values of ultimate strain, we found that varying both trabecular and cortical tissue ultimate strains by ±1 SD changed the computed vertebral strength by (mean±SD)±6.9±1.1% on average. Mechanistically, that modest effect arose because the proportion of yielded tissue (without damage) was 0.9±0.3% of all the bone tissue across the nine cases and the proportion of damaged tissue (i.e. tissue exceeding the prescribed tissue-level ultimate strain) was 0.2±0.1%. If the types of variations in tissue-level ductility investigated here accurately represent real typical variations in the population, the consistency of our results across specimens and the modest effect size together suggest that typical variations in tissue-level ductility only have a modest impact on vertebral compressive strength, in large part because so few trabeculae are damaged at the load capacity of the bone.

The Effect of the Joint Capsule and Anterior Oblique Ligament on Dorsal Subluxation of the First Metacarpal During Key Pinch.

Laxity of the anterior oblique ligament (AOL) and/or the dorsoradial ligament (DRL) are believed to contribute to the progression of osteoarthritis in the trapeziometacarpal joint through increased dorsal subluxation. Stress radiographs during functional tasks, such as key pinch, can be used to evaluate such joint instability. Cadaveric experiments can explore joint contact pressures as well as subluxation under varying conditions, to gain knowledge about joint mechanics. The disturbance of supporting tissues, such as the joint capsule, during experiments may affect the recorded stability of the joint. To evaluate potential effects of opening the joint capsule and severing the AOL, eleven cadaveric specimens were rigged to simulate key pinch. An anteroposterior (AP) radiograph of the hand was recorded for each specimen while intact, after partially opening the joint capsule and after sectioning the AOL. First metacarpal subluxation levels were compared between the intact joint, partially open joint capsule, and sectioned AOL. Neither opening the joint capsule nor cutting the AOL had a statistically significant effect on metacarpal subluxation. The results indicate that partially opening the joint capsule has a negligible effect on joint mechanics and support recent studies that postulate that the AOL plays a less substantial role in preventing subluxation.

Validating the Transfer of Skills Acquired on a Prostate Biopsy Simulator: A Prospective, Randomized, Controlled Study

To evaluate the ability of students to reproduce the skills acquired on a prostate biopsy simulator in a real-life situation. A prospective randomized controlled study was conducted. Medical students with no experience of prostate biopsy were randomized between arm A « conventional training » and arm B « simulator-enhanced training. » The training was performed for both groups on the simulator. The students in arm B were provided with visual and numerical feedback. The transfer of skills was assessed by recording the position of the 12 biopsies performed by each student on an unembalmed human cadaver using a 3D ultrasound mapping device. The study was conducted in an academic urology department and the cadaver experiments in the adjoining anatomy laboratory. Twenty-four students were included, and 22 completed the study. The median score obtained on the simulator at the end of the training was 57% (53-61) for arm A and 66% (59-71) for arm B. The median score obtained on the cadaver by students trained with the simulator was 75% (60-80), statistically superior to the score obtained by students trained conventionally of 45% (30-60), p < 0.0001. The median score obtained by all students when performing biopsies in a real-life situation was 63% (50-80) versus 60% (56-70) for their last training on the simulator. These results support the transfer of skills acquired on the simulator, and the superiority of a training curriculum integrating simulation, and performance feedback.

Development and Validation of Finite Element Analysis Model (FEM) of Craniovertebral Junction: Experimental Biomechanical Cadaveric Study.

Experimental Cadaveric Biomechanical Study. To establish an experimental procedure in cadavers to estimate joint stiffness/stability at craniovertebral junction (CVJ) region with various implant systems and to develop/validate an indigenous cost effective 3D-FEM (three-dimensional finite element model) of CVJ region. Finite element analysis (FEM) tools can provide estimates of internal stress and strain in response to external loading of various implant systems used in CVJ fixations. Experimental setup for conducting biomechanical movements on CVJ region of cadaver was developed using cost effective innovative tools. A manually actuated seven- degrees of freedom parallel manipulator motion testing system (MA7DPM) was designed and developed to impart designed trajectories and to conduct various biomechanical motion studies at CVJ region for the present study. FEM model of CVJ region was developed and subsequently validated with CVJ morphometry data of 15 human subjects of Asian origin. Validated FEM was subjected to force motion studies at the CVJ region. The force-motion maps obtained from the FEM studies were subsequently validated against biomechanical experiment results from cadaveric experiment results obtained with three different implant fixations. A cost effective biomechanical tool (which did not require decapitation of cadaveric head) and a customised chair (to place cadaver in sitting position during conduct of biomechanical movements simulating real-life scenario) was indigenously designed and developed. Developed biomechanical tool (MA7DPM) for this study is likely to be useful for stress-testing analysis of various implant systems for individual patients undergoing surgery at CVJ region in near future. 5.

A novel approach for optimal graft positioning and tensioning in anterior cruciate ligament reconstructive surgery based on the finite element modeling technique

BackgroundIn ACL-reconstructed patients the postoperative knee biomechanics may differ from the intact knee biomechanical behavior which can alter knee kinematics and kinetics, and as a result lead to the progression of knee osteoarthritis. The aim of this study was to demonstrate the potential of finite element models to define the optimal choices in surgical parameters in terms of optimal graft positioning in combination with graft type in order to restore the kinematic and kinetic behavior of the knee as best as possible. MethodsA workflow was proposed based on cadaveric experiments in order to restore the injured knee to a near normal physiological condition. Femoral and tibial graft insertion sites and graft fixation tension were optimized to obtain similar intact knee laxity, for three common single-bundle and one double-bundle reconstructions. To verify the success of the surgery with the variables calculated using the proposed workflow, a full walking cycle was simulated with the intact, ACL-ruptured, optimal ACL-reconstructed and non-optimal reconstructed knees. ResultsOur results suggested that for patellar tendon and hamstring tendon grafts, anatomical positioning (fixation force: 40 N), and for quadriceps tendon graft, isometric positioning (fixation tension: 85 N) could recover the intact joint kinematics and kinetics. Also for double-bundle reconstruction, with the numerically calculated optimal insertion sites, both bundles needed 50-N fixation force. ConclusionsWith optimal graft positioning parameters, following the proposed workflow in this study, any of the single-bundle graft types and surgical techniques (single vs. double-bundle) may be used to acceptably recover the intact knee joint biomechanical behavior.

Origami-Layer-Jamming Deployable Surgical Retractor With Variable Stiffness and Tactile Sensing

Abstract Origami-based flexible, compliant, and bio-inspired robots are believed to permit a range of medical applications within confined environments. In this article, we experimentally demonstrated an origami-inspired deployable surgical retractor with the controllable stiffness mechanism that can facilitate safer instrument–tissue interaction in comparison to their rigid counterparts. When controllable negative-pressure is applied to the jammed origami retractor module, it becomes more rigid, increasing its strength. To quantify origami-modules strength further, we demonstrated performances of retractor based on the Daler–Rowney Canford paper (38 grams per square meter (gsm)) and sandpaper of 1000 grit. Experiments on the proposed retractor prototype elucidated sandpaper-based retractor can outperform paper-38-gsm retractor for facelift incision with the width of more than 9 cm. Though 38 gsm Canford paper comprised of thin layers, 16 times lesser in thickness than sandpaper, experiments proved its comparable layer jamming (LJ) performance. We leverage the advantage of the LJ mechanism to tune retractor stiffness, allowing the instrument to hold and separate a facelift incision to mitigate the likelihood of surgical complications. The retractor is equipped with a custom-made printed conductive ink-based fabric piezoresistive tactile sensor to assist clinicians with tissue-retractor interaction force information. The proposed sensor showed a linear relationship with the applied force and has a sensitivity of 0.833 N−1. Finally, cadaver experiments exhibit an effective origami-inspired surgical retractor for assisting surgeons and clinicians in the near future.

Biomechanical cadaver study of proximal fixation in a minimally invasive bipolar construct.

Biomechanical human cadaver study. To determine the three-dimensional intervertebral ranges of motion (ROMs) of intact and hook-instrumented thoracic spine specimens subjected to physiological loads, using an in vitro experimental protocol with EOS biplane radiography. Pedicle screws are commonly used in thoracic instrumentation constructs, and their biomechanical properties have been widely studied. Promising clinical results have been reported using a T1-T5 thoracic hook-claw construct for proximal rod anchoring. Instrumentation stability is a crucial factor in minimizing mechanical complications rates but had not been assessed for this construct in a biomechanical study. Six fresh-frozen human cadaver C6-T7 thoracic spines were studied. The first thoracic vertebrae were instrumented using two claws of supra-laminar and pedicle hooks, each fixed on two adjacent vertebrae, on either side of a single free vertebra. Quasi-static pure-moment loads up to 5Nm were applied to each specimen before and after instrumentation, in flexion-extension, right and left bending, and axial rotation. Five steel beads impacted in each vertebra allowed 3D tracking of vertebral movements on EOS biplanar radiographs acquired after each loading step. The relative ranges of motion (ROMs) of each pair of vertebras were computed. Mean ROMs with the intact specimens were 17° in flexion-extension, 27.9° in lateral bending, and 29.5° in axial rotation. Corresponding values with the instrumented specimens were 0.9°, 2.6°, and 7.3°, respectively. Instrumentation significantly (P < 0.05) decreased flexion-extension (by 92-98%), lateral bending (by 87-96%), and axial rotation (by 68-84%). This study establishes the biomechanical stability of a double claw-hook construct in the upper thoracic spine, which may well explain the low mechanical complication rate in previous clinical studies. Not applicable, experimental cadaver study.

An ACL reconstruction robotic positioning system based on anatomical characteristics

To improve the positioning accuracy of tunnels for anterior cruciate ligament (ACL) reconstruction, we proposed an ACL reconstruction robotic positioning system based on anatomical characteristics. The system includes a preoperative path planning system, an intraoperative path planning system, and a navigation and positioning system. Brahmet line, anterior, and posterior cortical lines are used for registration of preoperative computed tomography (CT) images and intraoperative X-ray images. A new calibrator of C-arm is applied to establish the mapping between medical images and surgical space. Tunnels for ACL reconstruction can be built anatomically by the robot. The accuracy of the path planning system is 1.73 mm in the four dry bones experiments and 2.17 mm in the two cadaver experiments. The accuracy meets the accuracy requirement of ACL construction surgery.

Automatic Segmentation of Multiple Structures in Knee Arthroscopy Using Deep Learning

Minimally invasive surgery (MIS) is among the preferred procedures for treating a number of ailments as patients benefit from fast recovery and reduced blood loss. The trade-off is that surgeons lose direct visual contact with the surgical site and have limited intra-operative imaging techniques for real-time feedback. Computer vision methods as well as segmentation and tracking of the tissues and tools in the video frames, are increasingly being adopted to MIS to alleviate such limitations. So far, most of the advances in MIS have been focused on laparoscopic applications, with scarce literature on knee arthroscopy. Here for the first time, we propose a new method for the automatic segmentation of multiple tissue structures for knee arthroscopy. The training data of 3868 images were collected from 4 cadaver experiments, 5 knees, and manually contoured by two clinicians into four classes: Femur, Anterior Cruciate Ligament (ACL), Tibia, and Meniscus. Our approach adapts the U-net and the U-net++ architectures for this segmentation task. Using the cross-validation experiment, the mean Dice similarity coefficients for Femur, Tibia, ACL, and Meniscus are 0.78, 0.50, 0.41, 0.43 using the U-net and 0.79, 0.50, 0.51, 0.48 using the U-net++. While the reported segmentation method is of great applicability in terms of contextual awareness for the surgical team, it can also be used for medical robotic applications such as SLAM and depth mapping.

Kinematic Model of the Human Leg Using DH Parameters

Robotic-assisted surgical procedures have recently increased in popularity in clinical environments. Applications of clinically approved surgical robots range from minimally invasive surgery to open joint replacements. In hip and knee orthopaedic procedures, access to leg joint cavities require constant manipulation of the patient's leg to a high degree of accuracy to reduce surgical injuries. This study develops a nine degree of freedom serial kinematic model of the human leg, using the well known Denavit Hartenberg Parameters, for robotic-assisted leg manipulation during orthopaedic leg surgery. The proposed model is validated through human cadaver experiments with an optical tracking system used as ground-truth to measure the leg pose. The knee and foot workspace for the model determines the pose of the leg and in comparing it to cadaver leg position. The positional error relative to the cadaver leg was found to be 0.43mm and 0.4mm respectively, with a maximum uncertainty of 3.51mm in the foot position. It demonstrates that the proposed model provides an accurate representation of the human leg motion for automated leg manipulation during orthopaedic surgery.

Real-time surgical instrument tracking in robot-assisted surgery using multi-domain convolutional neural network.

Image-based surgical instrument tracking in robot-assisted surgery is an active and challenging research area. Having a real-time knowledge of surgical instrument location is an essential part of a computer-assisted intervention system. Tracking can be used as visual feedback for servo control of a surgical robot or transformed as haptic feedback for surgeon–robot interaction. In this Letter, the authors apply a multi-domain convolutional neural network for fast 2D surgical instrument tracking considering the application for multiple surgical tools and use a focal loss to decrease the effect of easy negative examples. They further introduce a new dataset based on m2cai16-tool and their cadaver experiments due to the lack of established public surgical tool tracking dataset despite significant progress in this field. Their method is evaluated on the introduced dataset and outperforms the state-of-the-art real-time trackers.