Biomechanical role and motion contribution of ligaments and bony constraints in the elbow stability: A preliminary study

In flexion-extension motion, the interaction of several ligaments and bones characterizes the elbow joint stability. The aim of this preliminary study was to quantify the relative motion of ulna respect to humerus in two human elbow specimens and to investigate the constraints role for maintaining the joint stability in different dissections condition. Two clusters of 4 markers were fixed respectively to ulna and humerus, and their trajectory was recorded by a motion capture system during orthopedic maneuver. Considering the medial ulnar collateral posterior bundle (pMUCL) and the coronoid, two dissection sequences were executed. The orthopedic maneuver of compression, pronation and varus force was repeated at 30°, 60°, 90° flexion for the functional investigation of constraints. Ulna deflection was compared to a baseline flexion condition. Respect to intact elbow, the coronoid osteotomy influences the elbow stability at 90° (deflection=11.49±17.39 mm), while small differences occur at 30° and 60°, due to ligaments constraint. The contemporary pMUCL dissection and coronoid osteotomy causes elbow instability, with large deflection at 30° (deflection=34.40±9.10 mm), 60° (deflection=45.41±18.47 mm) and 90° (deflection=52.16±21.92 mm). Surgeons may consider the pMUCL reconstruction in case of unfixable coronoid fracture

The Design and Validation of a Computational Rigid Body Model for Study of the Radial Head

Rigid body modeling has historically been used to study various features of the elbow joint including both physical and computational models. Computational modeling provides an inexpensive, easily customizable, and effective method by which to predict and investigate the response of a physiological system to in vivo stresses and applied perturbations. Utilizing computer topography scans of a cadaveric elbow, a virtual representation of the joint was created using the commercially available MIMICS(TM) and SolidWorks(TM) software packages. Accurate 3D articular surfaces, ligamentous constraints, and joint contact parameters dictated motion. The model was validated against two cadaveric studies performed by Chanlalit et al. (2011, 2012) considering monopolar and bipolar circular radial head replacements in their effects on radiocapitellar stability and respective reliance upon lateral soft tissues, as well as a comparison of these with a novel anatomic radial head replacement system in an elbow afflicted with the “terrible triad” injury. Rigid body simulations indicated that the computational model was able to accurately recreate the translation of forces in the joint and demonstrate results similar to those presented in the cadaveric data in both the intact elbow and in unstable injury states. Trends in the resulting data were reflective of the average behavior of the cadaveric specimens while percent changes between states correlated closely with the experimental data. Information on the transposition of forces within the joint and ligament tensions gleaned from the computational model provided further insight into the stability of the elbow with a compromised radial head

Musculoskeletal Modeling of The Human Elbow Joint

Title from PDF of title page viewed June 8, 2017Dissertation advisor: Antonis P. Stylianou and Majid Bani-YaghoubVitaIncludes bibliographical references (pages 130-139)Thesis (Ph.D.)--School of Computing and Engineering and Department of Mathematics and Statistics. University of Missouri--Kansas City, 2017Comprehensive knowledge of the in vivo loading of elbow structures is essential in understanding the biomechanical causes associated with elbow diseases and injuries, and to find appropriate treatment. Currently, in vivo measurements of ligament, and muscle forces, and cartilage contact pressures during elbow activities is not possible. Therefore, computational models needs to be employed for prediction. A dynamic computational model in which muscle, ligament and articular surface contact forces are predicted concurrently would be the ideal tool for patient specific pre-operative planning, computer aided surgery and rehabilitation. Computational models of the elbow have been developed to study joint behavior, but all of these models have limited applicability because the joint structure was modeled as an idealized joint (e.g. hinge joint) rather than a true anatomical joint. Three dimensional studies of elbow passive motion showed that the elbow does not function as a simple hinge joint. An accurate elbow model should reflect the intrinsic laxity of the elbow especially for clinical applications. Presented here are methods for developing an anatomically based computational model of the human elbow joint that replicates the mechanical behavior of the joint and is capable of concurrent prediction of articular contact, ligament, and muscle forces under dynamic conditions. The model performance was evaluated in both a cadaveric study and a living human subject experiment. The validated models were then used to investigate the effects of medial and lateral collateral ligament deficiency on elbow joint kinematics, ligament loads, and articular contact pressure distribution.Introduction -- Background -- Prediction of elbow joint contact mechanics in the multibody framework -- Lateral collateral ligament deficiency of the elbow joint: a modeling approach -- A modeling approach to simulating medial collateral ligament deficiency of the elbow joint -- Muscle driven elbow joint simulation: a computational approach -- Conclusio

Development of an Active Elbow Motion Simulator and Coordinate Systems to Evaluate Kinematics in Multiple Positions

Elbow disorders are common as a consequence of both traumatic and degenerative conditions. Relative to disorders of the lower limb, there is comparatively little evidence to direct the treatment of many elbow disorders. Biomechanical studies are required to develop and validate the optimal treatment of elbow disorders prior to their application in patients. Clinically relevant simulation of elbow motion in the laboratory can be a powerful tool to advance our knowledge of elbow disorders. This work was undertaken with the rationale that simulation and quantification of elbow motion could be improved significantly. This treatise includes the development and evaluation of an in-vitro elbow motion simulator which, with the humerus horizontally positioned, is the first to achieve active flexion and extension in a vertical plane. Additionally, it is capable of operating in the vertical, varus and valgus positions, and while maintaining full forearm pronation or supination. The simulator controller employs a Cascade PID configuration with feedforward transfer functions, which achieves unified control of flexion angle and muscle tension for multiple muscles. Feedback of the elbow joint angle and muscle tension is utilized to achieve closed-loop control. A performance evaluation in a full series of specimens clearly demonstrated that the actual joint angle is not more than 5 degrees removed from the desired setpoint during flexion or extension in any position. Also, a new method for creating upper extremity bone segment coordinate systems which are derived from elbow flexion and forearm rotation was developed and tested. This produced joint kinematics with significantly less inter-subject variability than traditional anatomy-derived coordinate systems. This minimally-invasive method also provides increased statistical power for laboratory based studies and may prove useful for clinical applications. The new simulation techniques developed herein were applied to an in-vitro investigation of olecranon fracture repair with clinical significance. This study revealed valuable insights into a common repair procedure. This was made possible by the previously unattainable measurements that these new techniques now provide. These developments will assist surgeons and other investigators in the design and evaluation of treatments for elbow disorders, and contribute to the betterment of patient care

Design, Development, and Biomechanical Testing of a Novel Prosthetic Replacement for the Coronoid Process

The coronoid process is considered an integral structure for maintaining the stability of the elbow joint. While most fractures of the coronoid are successfully treated with open reduction and internal fixation, there is currently no reliable method to manage severely comminuted fractures. A prosthetic device is required to replace the coronoid in the setting of unreconstructable fractures. The stabilizing effect of a coronoid prosthesis, designed based on an anthropometric characterization of the proximal ulna, was investigated in an elbow joint motion simulator. The prosthesis was found to effectively restore stability to the coronoid deficient elbow. Additionally, a biomechanical investigation was conducted to evaluate implant fixation techniques. Cement was found to provide the most secure fixation, while screw fixation was also found to provide acceptable initial fixation, pending osseous integration. Collectively, these results indicate that the use of a coronoid prosthesis may be useful in treating severe unreconstructable fractures of the coronoid proces

In Vitro Biomechanical Analyses of The PCL and Medial Ligaments of The Human Knee

Previous studies have shown that surgical treatments of PCL injuries are not successful in all cases and there is room for improvement. The effectiveness of an isolated PCL reconstruction, in the setting of what actually is a multi-ligament injury, may be inadequate, and therefore the biomechanical contribution of other ligaments in a PCL-deficient knee need to be better understood. A new apparatus was used to analyze the effect of medial ligaments transection on the kinematics of the PCL-deficient knee during simulated clinical tests and activities of daily living. We observed that the anterior translation of the medial side of the joint increased after transection of the POL; however, this increase was small. Transection of neither the POL nor dMCL affected the posterior translation of the medial aspect of the joint; however, both contributed to resisting loads crossing the joint, which increase after the PCL transection

The Contact Mechanics and Kinematics of Radial Head Implants

A number of commercially available radial head (RH) implants are used for the management of RH fractures. The optimal shape of a RH implant to restore joint mechanics to the native state has not been established. This work compares radiocapitellar contact and kinematics for three implant designs as well as the native RH. These implants include an axisymmetric, a quasi-anatomic and a patient-specific design. When compared to the native RH, only the axisymmetric implant was significantly different in contact area (p=0.008). Active and passive forearm supination was assessed for differences in translations of the RH. Significant differences were found in anterior-posterior translations during active forearm supination between the axisymmetric implant and the native RH (p=0.014) and between the quasi-anatomic implant and native RH (p=0.019). This work demonstrates that while an anatomic implant slightly improves radiocapitellar contact and kinematics, future efforts are needed to optimize the materials employed in these devices

Development and Assessment of a Micro-CT Based System for Quantifying Loaded Knee Joint Kinematics and Tissue Mechanics

Although anterior cruciate ligament (ACL) reconstruction is a highly developed surgical procedure, sub-optimal treatment outcomes persist. This can be partially attributed to an incomplete understanding of knee joint kinematics and regional tissue mechanic properties. A system for minimally-invasive investigation of knee joint kinematics and tissue mechanics under clinically relevant joint loads was developed to address this gap in understanding. A five degree-of-freedom knee joint motion simulator capable of dynamically loading intact human cadaveric knee joints to within 1% of user defined multi-axial target loads was developed. This simulator was uniquely designed to apply joint loads to a joint centered within the field of view of a micro-CT scanner. The use of micro-CT imaging and tissue-embedded radiopaque beads demonstrated high-resolution strain measurement, distinguishing differences in inter-bead distances as low as 0.007 mm. Inter-bead strain measurement was highly accurate and repeatable, with no significant error introduced from cyclic joint loading. Finally, regional strain was repeatably measured using radiopaque markers in four intact, human cadaveric knees to within 0.003 strain in response to multi-directional joint loads. This novel combination of dynamic knee joint motion simulation, tissue-embedded radiopaque markers, and micro-CT imaging provides the opportunity to increase our understanding of the kinematics and tissue mechanics of the knee, with the potential to improve ACL reconstruction outcomes

Optimizing the Rehabilitation of Elbow Lateral Collateral Ligament Injuries

Elbow lateral collateral ligament (LCL) injuries frequently arise following trauma, and can result in disabling instability. Typically such injuries are managed with immobilization followed by a graduated exercise regime; however there is minimal biomechanical evidence to support current treatment protocols. This investigation examines the in vitro effectiveness of several rehabilitation techniques using a custom elbow motion simulator. It was found that active range of motion is safest in the overhead position (n = 7). Early motion in this position may reduce the incidence of elbow stiffness without compromising ligament healing following LCL injury. Forearm pronation and active motion stabilize the LCL-deficient elbow, while varus positioning worsens instability. It was also found that a hinged elbow orthosis did not significantly improve in vitro elbow stability following LCL injury (n = 7). However, such orthoses may be useful in keeping the forearm in the more stable pronated position. Future research directions are proposed, with suggestions on applying this methodology to other elbow injuries

Development and Validation of a Computational Musculoskeletal Model of the Elbow Joint

Musculoskeletal computational modeling is a versatile and effective tool which may be used to study joint mechanics, examine muscle and ligament function, and simulate surgical reconstructive procedures. While injury to the elbow joint can be significantly debilitating, questions still remain regarding its normal, pathologic, and repaired behavior. Biomechanical models of the elbow have been developed, but all have assumed fixed joint axes of rotation and ignored the effects of ligaments. Therefore, the objective of this thesis was to develop and validate a computational model of the elbow joint whereby joint kinematics are dictated by three-dimensional bony geometry contact, ligamentous constraints, and muscle loading.Accurate three-dimensional bone geometry was generated by acquiring CT scans, segmenting the images to isolate skeletal features, and fitting surfaces to the segmented data. Ligaments were modeled as tension-only linear springs, and muscle were represented as force vectors with discrete attachment points. Bone contact was modeled by a routine which applied a normal force at points of penetration, with a force magnitude being a function of penetration depth. A rigid body dynamics simulator was used to predict the model\u27s behavior under particular external loading conditions.The computational model was validated by simulating past experimental investigations and comparing results. Passive flexion-extension range of motion predicted by the model correlated exceptionally well with reported values. Bony and ligamentous structures responsible for enforcing motion limits also agreed with past observations. The model\u27s varus stability as a function of elbow flexion and coronoid process resection was also investigated. The trends predicted by the model matched those of the associated cadaver study.This thesis successfully developed an accurate musculoskeletal computational model of the elbow joint complex. While the model may now be used in a predictive manner, further refinements may expand its applicability. These include accounting for the interference between soft tissue and bone, and representing the dynamic behavior of muscles