Stem abutment affects alignment of the humeral component in computer-assisted elbow arthroplasty.
ABSTRACT The humeral component in total elbow arthroplasty has limited geometric modularity, and the extent to which this affects accurate positioning is unknown. The objectives of this study were to (1) validate the accuracy of a computer-assisted implant alignment technique, and (2) identify variations in distal humeral morphology that affected computer-assisted implant alignment. This was achieved by implanting both an unmodified humeral component and an implant with a reduced stem using computer assistance. We hypothesized that implantation of a humeral component with a reduced stem length would be more accurate than implantation of the standard length stem. In addition, we hypothesized that the variation in flexion-extension (FE) varus-valgus angulation would significantly affect computer-assisted implant alignment.
Computer-assisted alignment of the implant articulating axis with the humeral FE axis was performed on 13 cadaveric humeri for both the regular and modified humeral component. Navigation was based on alignment of the prosthesis with a preoperative plan and registration of this plan to the humerus.
Implant alignment was significantly improved for the reduced stem. Alignment error of the reduced stem averaged 1.3 ± 0.5 mm in translation and 1.2° ± 0.4° in rotation, compared with 1.9 ± 1.1 mm and 3.6° ± 2.1° for the regular stem. Humeral varus-valgus angulation significantly affected alignment of the unmodified stem.
A humeral component with a fixed valgus angulation cannot be accurately positioned in a consistent fashion without sacrificing alignment of the FE axis. Improved accuracy of implant placement can be achieved by introducing a family of humeral components, with 3 valgus angulations of 0°, 4° and 8°.
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ABSTRACT: Elbow replacement or arthroplasty is a good therapeutic option for a large percentage of patients with significant joint destruction. However, many orthopaedic surgeons are no familiar with the surgical approaches or techniques associated with elbow replacement implants. Furthermore, the incidence of complications is higher than in other joint replacements, the most important being infections, mechanical failure, cubital neuropathy, and problems with the triceps. For these reasons, the use of bone arthroplasty in Spain may be less than ideal. Although, inflammatory arthritic diseases, such as rheumatoid arthritis, are the most frequent indication for this operation, distal humerus fractures and post-traumatic disease are a growing indication. This work attempts to summarise the most important current concepts associated with elbow replacement.Revista Española de Cirugía Ortopédica y Traumatología 09/2012; 56(5):413–420.
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ABSTRACT: Distal humeral hemiarthroplasty is a treatment option for distal humeral fractures, nonunions, and avascular necrosis. The biomechanical effects, however, have not been reported. The purpose of this in vitro study was to quantify the effects of hemiarthroplasty and implant size on elbow joint kinematics. Eight fresh-frozen cadaveric arms were mounted in an in vitro motion simulator. An electromagnetic tracking system quantified elbow kinematics. A custom distal humeral stem was implanted by use of navigation, and 3 humeral articular spools were evaluated: optimally sized, undersized, and oversized. Statistical analysis was performed with repeated-measures analysis of variance. Distal humeral hemiarthroplasty altered elbow kinematics, regardless of implant size. In the valgus position, the optimally sized implant resulted in a mean increase in valgus angulation of 3° ± 1° (P = .003) as compared with the osteotomy control. In the varus position, the optimal and undersized implants both resulted in significant increases in varus angulation: 3° ± 1° (P = .01) and 3° ± 1° (P = .001), respectively. The undersized implant had the greatest alteration in kinematics, whereas the oversized implant best reproduced native elbow kinematics. This study showed a small but significant alteration in elbow joint kinematics with placement of a distal humeral hemiarthroplasty implant, regardless of implant size. This could be due to errors in implant positioning and/or differences in the shape of the humeral implant relative to the native elbow. These changes in joint tracking may cause abnormal articular contact and loading, which may result in pain and cartilage degeneration over time.Journal of shoulder and elbow surgery / American Shoulder and Elbow Surgeons ... [et al.] 04/2014; · 1.93 Impact Factor
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ABSTRACT: Total elbow arthroplasty (TEA) represents one of the surgical procedures performed on the upper limb in order to replace the diseased joint with a prosthetic device. According to current surgical standards, TEA is carried out with little information on the amount of bone to be removed in order to allow the installation of the implant within the medullary canal of the humerus. To address this, the present study proposes a numerical technique capable to estimate both the amount and location of the bone to be removed from the canal. As a first step, the developed method entails the extraction of the outer and inner contours of the bone based on the raw CT data. Then, global optimization search built on a gradient-based solver was used to identify the implant posture which minimizes the total interference amount as quantified across the entire length of the analyzed humeral specimen. After the proposed approach was tested on three different specimens and compared with a computationally-intensive baseline, clinically-relevant information was extracted in an attempt to provide the surgeons with more effective means to decide on the location and the amount of bone to be removed.Computer-Aided Design and Applications 07/2014; 11(4):478-492.