Innovative Approach in the Development of Computer Assisted Algorithm for Spine Pedicle

Pedicle screws are typically used for fusion, percutaneous fixation, and means of gripping a spinal segment. The screws act as a rigid and stable anchor points to bridge and connect with a rod as part of a construct. The foundation of the fusion is directly related to the placement of these screws. Malposition of pedicle screws causes intraoperative complications such as pedicle fractures and dural lesions and is a contributing factor to fusion failure. Computer assisted spine surgery (CASS) and patient-specific drill templates were developed to reduce this failure rate, but the trajectory of the screws remains a decision driven by anatomical landmarks often not easily defined. Current data shows the need of a robust and reliable technique that prevents screw misplacement. Furthermore, there is a need to enhance screw insertion guides to overcome the distortion of anatomical landmarks, which is viewed as a limiting factor by current techniques. The objective of this study is to develop a method and mathematical lemmas that are fundamental to the development of computer algorithms for pedicle screw placement. Using the proposed methodology, we show how we can generate automated optimal safe screw insertion trajectories based on the identification of a set of intrinsic parameters. The results, obtained from the validation of the proposed method on two full thoracic segments, are similar to previous morphological studies. The simplicity of the method, being pedicle arch based, is applicable to vertebrae where landmarks are either not well defined, altered or distorted

A Clove-Hitch Suture Method for Small-Caliber Tendon Ends

Background: The choices of suture methods used to secure the end of a small-caliber tendon with a combination of suture materials passing through and looping around the tendon are not well documented. A secure stitchtendon unit may be an important factor in preserving muscle function, by facilitating healing without gapping or failure. Methods: Five types of suture methods utilizing four or fewer passes through the tendon end were mechanically tested on 178 canine flexor digitorum profundus tendons. An Instron apparatus was used to test the load to failure. Results: The single and double clove-hitch suture methods demonstrated improved repair strength when compared with the three other methods studied in this small-caliber canine tendon model. Conclusions: The single and double clove-hitch suture method better secured the end of a small-caliber tendon compared with other methods. Clinical Relevance: The single (pull-out) and double (non-pull-out) clove-hitch suture methods are reliable alternatives for the repair of small-caliber tendons

Factors Influencing Initial Cup Stability in Total Hip Arthroplasty

Background: One of the main goals in total hip replacement is to preserve the integrity of the hip kinematics, by well positioning the cup and to make sure its initial stability is congruent and attained. Achieving the latter is not trivial. Methods: A finite element model of the cup-bone interface simulating a realistic insertion and analysis of different scenarios of cup penetration, insertion, under reaming and loading is investigated to determine certain measurable factors sensitivity to stress-strain outcome. The insertion force during hammering and its relation to the cup penetration during implantation is also investigated with the goal of determining the initial stability of the acetabular cup during total hip arthroplasty. The mathematical model was run in various configurations to simulate 1 and 2 mm of under-reaming at various imposed insertion distances to mimic hammering and insertion of cup insertion into the pelvis. Surface contact and micromotion at the cup-bone interface were evaluated operative loading conditions. Findings: The results suggest a direct correlation between under-reaming and insertion force used to insert the acetabular cup on the micromotion and fixation at the cup-bone interface. Interpretation: while increased under-reaming and insertion force result in an increase amount of stability at the interface, approximately the same percentage of surface contact and micromotion reduction can be achieved with less insertion force. We need to exercise caution to determine the optimal configuration which achieves a good conformity without approaching the yield strength for bone