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Acromioclavicular joint separation is a common shoulder injury. Grade I and II separation may be treated nonoperatively, whereas higher grades tend to require surgical intervention. Various repair techniques have been described in the literature, with no consensus on the gold standard. This Technical Note describes our use of a graft-passing instrument to pass suture under the coracoid during an anatomic reconstruction of both the acromioclavicular and coracoclavicular ligaments. Although this approach is technically challenging, it avoids coracoid drilling and requires smaller-diameter clavicle and acromion drilling. Furthermore, using suture instead of graft material increases the cost-effectiveness of the procedure.

Several factors affect the success of an anterior cruciate ligament reconstruction, including graft origin, type, and morphology. Hamstring and bone–patellar tendon–bone autografts are the most widely used, and there are many different techniques of graft preparation with each. In this Technical Note and accompanying video, a 4-strand hamstring autograft technique is described that uses a simple diamond-type braid to produce a more ovoid morphology with increased cross-sectional area. Increased graft diameters have been associated with higher success rates and more positive long-term outcomes. Therefore, this braiding construct may provide additional tensile strength with increased resistance to failure than grafts that are otherwise undersized using conventional techniques.

Anterior shoulder pathology involving the subscapularis is often associated with the biceps tendon because both anatomic structures intersect the lesser tuberosity. Standard procedures for such pathology often involve simultaneous subscapularis repairs and biceps tenodesis. Single anterior portal subscapularis repairs have been emerging in the past 5 years because of cost-effectiveness and efficiency. Biceps tenodesis is a common procedure performed both open and arthroscopically. This technique takes advantage of the close relation between the long head of the biceps tendon and subscapularis tendon to restore the functional length-tension relation and preserve function through fixation using a single portal and a single knotless suture anchor.

Pathology of the acromioclavicular joint is common and often resistant to conservative treatment, requiring distal clavicle excision for definitive relief. First described as an open technique by Mumford and Gurd in 1941, distal clavicle excision has evolved greatly, with arthroscopic techniques currently predominating. No significant difference has been found in patient satisfaction or rate of complication between the techniques in a recent meta-analysis. Indeed, open excisions are still performed at a high rate, owing to the difficulty in technique and visualization with arthroscopic methods. One major critique of arthroscopic distal clavicle excision is difficulty safeguarding against under- and overexcision of the distal clavicle due to the lack of depth perception and visual reference points of the arthroscopic perspective. This Technical Note and accompanying video describe an indirect subacromial arthroscopic distal clavicle excision using a fluoroscopic Kirschner wire guide placed at the proximal border prior to resection to serve as a visual and mechanical reference to overexcision.

Acromioclavicular joint separations are common shoulder injuries, yet standard treatment practices vary. Popular surgical techniques include reconstruction using allografts or neighboring ligaments as well as repair using screws and sutures. This Technical Note and accompanying video describe both an acromioclavicular and coracoclavicular joint reconstruction using an allograft to replace native acromioclavicular ligament along with an AC joint reduction using a Suture Cerclage System to precisely control reduction and restore anatomic alignment.

Achilles repair has evolved over the past 30 years, from large open procedures with high complication rates to shorter, less-invasive procedures with better outcomes. Percutaneous repair has comparable failure rates with open repairs, fewer complications, and faster recovery. However, percutaneous Achilles repairs risk sural nerve injury. A mini-open repair fuses the gap between percutaneous and open procedures, and this approach has the potential to mitigate nerve injury while maintaining the increased efficiency in procedure time and patient recovery. The purpose of this Technical Note and accompanying video is to outline the repair of the Achilles tendon using a mini open repair using a low-profile flat braided suture.

Total shoulder arthroplasty (TSA) has evolved over the years and is used for a variety of indications, with arthritis being the most common. Stemless TSA is a unique bone-preserving design that can eliminate rotational malalignment. Additionally, recent literature has found utility in the use of biological mesh and a platelet-rich plasma injection to improve healing. The purpose of this article is to outline the process of TSA using a stemless system and how to incorporate the use of amnion matrix and platelet-rich plasma into the surgical technique.

The throat region of solid armatures is subjected to significant stress and temperature during a railgun launch. Recovered aluminum alloy armatures show evidence of plastic deformation, melting, and even cracking in the throat region. Plastic deformation can result from magnetic pinch or thermal expansion forces and melting from ohmic heating. Although cracking is historically associated with grain boundary melting, the cracks observed in recently recovered armatures are likely a result of thermal stresses. Finite-element codes EMAP3D and DYNA3D were linked to assess stresses generated by magnetic forces, inertial loading, wear, and thermal expansions. For low-speed armatures, thermal stresses were found to be as important as magnetic stresses. The observed cracking is likely due to rapid cooling, similar to quench cracking, and may or may not occur during launch. Index Terms--Cracking, solid armatures, throat region.

Previous work investigated macroscopic features of recovered aluminum alloy armatures launched at five different currents. Here, microstructural features of those armatures are explored. Several distinct heat-treatment regimes present near the armature throat surface include grain deformation, melting, and material ejection. Two distinct cracking mechanisms are present. The first--presumably due to liquation cracking---occurs at higher currents, is intergranular, and has cracking directions independent of armature geometry directions. The second--likely due to thermal stresses--is intragranular and has strong dependence on orientation. Detailed photomicrographs of the recovered armatures are presented, along with calculated dimensions of the heat-treatment zones and observed cracks. Index Terms--Aluminum-alloy armature, microstructure.

Insights from recovered armatures suggest re-examining historical modeling assumptions for railguns. The finite-element codes EMAP3D and DYNA3D were linked to explore the effects of temperature-dependent material properties, thermal diffusion, armature wear, inertial loading, thermal stresses, and 2-D model approximations. Temperatures and principal stresses for each of these cases were compared. Thermal diffusion and thermal stresses in armatures cannot be ignored past the first millisecond of launch; material properties under pulsed heating can significantly differ from equilibrium and room-temperature values. Armature wear and inertial loading can be ignored at low speeds, but not at high speeds (>1 km/s). Models in 2-D can approximate 3-D models with appropriate boundary conditions, but only for the first few milliseconds of launch. With a detailed EMAP3D model and minimal assumptions, simulations that agree within a few percentage points of microstructural measurements from recovered armatures are possible. Index Terms--Model assumption, railguns.

The correlation between wear and entropy flow in machinery components was studied experimentally.

Bond graph models for the audio range response of a dynamically continuous, linear motion magnetostrictive actuator are formulated and presented. The actuator involves a continuous rod of magnetostrictive material that extends, contracts, and vibrates in modes when energized by magnetic flux produced by a coil. The left end is fixed, force is extracted from the right end. The bond graph model includes dynamics of the energizing coil, the flux routing circuit, magnetic to mechanical energy conversion, and mechanical elements. Constitutive relations for magnetostriction suggest use of a multiport capacitor with ports for magnetic and mechanical power flow; constraints imposed by modal dynamics require a separate mechanical port for each vibration mode. Values were assigned to bond graph parameters in a non-empirical manner: solely from theory and handbook data. State equations and transfer functions were extracted from the bond graph. For audio range operation, theory (the bond graph model) compared well with experiment (measurements taken on a magnetostrictive actuator designed and built by the author).

The stress between axisymmetric bodies with quartic profiles are measured accurately by increasing the contact radius and surface profile with temperature uniformly. The gradual evolution of radius and profile provides information on the thermal deformations in electrically or frictionally heated bodies. The thermal deformations yield accurate values of the stress experienced by the quartic profile bodies.