A New Digital Preoperative Planning Method for Total Hip Arthroplasties

Preoperative templating is an important part of a THA. The ability to accurately determine magnification of the hip on the radiograph and apply identical magnification to the radiograph and template will improve accuracy of preoperative templating of THA. We designed a templating method using a new way of determining the hip magnification with a linear relationship between magnification of the hip and the reference object on top of the pubis symphysis; the relationship was determined on 50 radiographs. We then compared our method with two other templating methods: an analog method assuming an average hip magnification of 15% and a digital method determining the hip magnification with a one-to-one relationship between the reference object and the hip. All methods were reproducible. Uniform undersizing occurred when templating with the digital method based on the one-to-one relationship; the analog method best predicted the implanted prosthesis size, closely followed by our new digital templating method; the new method will be particularly applicable for preoperative THA when analog methods are replaced by digital methods

The Resistance Force of the Anterior Cruciate Ligament during Pull Probing Is Related to the Mechanical Property

There are various methods for reconstructing the anterior cruciate ligament (ACL) from other muscles or tendons. Initial tension of the reconstructed ACL is one of the key elements affecting postoperative outcomes. However, tension cannot be measured after graft fixation. The only intraoperative assessment is pull probing, which is performed by pulling joint soft tissues with the arthroscopic probe and can be measured quantitatively. Therefore, its value might be used as an alternative value for the mechanical property of the ACL. Using a probing device one author developed to measure the resistance force of soft tissues quantitatively while probing, we measured the resistance force of dissected ACLs and used tensile testing to investigate the correlation between the resistance force and the mechanical property of the ligaments. According to the results, when a certain amount of tension (strain; 16.6%) was applied, its mechanical properties were moderately correlated (r = 0.56 [p = 0.045]) with the probing force. Therefore, the tension of the reconstructed ACL after fixation under real ACL reconstruction surgery can be derived from the value of the probing device

Applicability of forcibly spinning technology to produce a finer silk filament

Forcibly spinning method has once shown a potential to enhance tensile strength of Bombyx mori silkworm silk fibers to the level of spider dragline silk. Thus, the tensile data for the forcibly spun silk fibers reported so far were compared with the tensile data for the industrially used hybridized F1 Bombyx mori silkworms. The forcibly spinning method may be convenient to produce a finer filament, but it was found to be difficult to produce a long and strong filament comparable to the commercial silk fibers. On the contrary, the breeding technology which can reduce the number of molts from four to three by feeding an imidazole compound appears to be the most practical strategy to obtain a finer and stronger silk filament with a length more than 500 m

Patient-specific Instrumentation for Acetabular Cup Orientation: Accuracy Analysis in a Pre-clinical Study

Abstract Purpose We investigated two major factors which affect the overall accuracy of patient specific instrumentation (PSI) for cup insertion in total hip arthroplasty; 1) the fitting of PSI on the bony surface, and 2) deviation of cup impaction under a linear visual reference. Methods Using 12 cadaveric hips, we inserted Kirschner wire (K-wire) through PSI on the acetabulum for the linear reference to transfer planned cup alignment. Deviation of the K-wire was then measured. With bone models, deviation when aligning an impactor to the K-wire was also measured. Results The mean deviation of the fitting was 1.9° for inclination and 2.0° for anteversion. The mean deviation when aligning the two lines was 1.2° for inclination and 1.4° for anteversion. Discussion This PSI can transfer the pre-operative plan to the operating room with acceptable accuracy