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Purpose Posterior tibial slope (PTS) represents an important risk factor for anterior cruciate ligament (ACL) graft failure, as seen in clinical studies. An anterior closing wedge osteotomy for slope reduction was performed to investigate the effect on ACL-graft forces and femoro-tibial kinematics in an ACL-deficient and ACL-reconstructed knee in a biomechanical setup. Methods Ten cadaveric knees with a relatively high native slope (mean ± SD): (slope 10° ± 1.4°, age 48.2 years ± 5.8) were selected based on prior CT measurements. A 10° anterior closing-wedge osteotomy was fixed with an external fixator in the ACL-deficient and ACL-reconstructed knee (quadruple Semi-T/Gracilis-allograft). Each condition was randomly tested with both the native tibial slope and the post-osteotomy reduced slope. Axial loads (200 N, 400 N), anterior tibial draw (134 N), and combined loads were applied to the tibia while mounted on a free moving and rotating X–Y table. Throughout testing, 3D motion tracking captured anterior tibial translation (ATT) and internal tibial rotation (ITR). Change of forces on the reconstructed ACL-graft (via an attached load-cell) were recorded, as well. Results ATT was significantly decreased after slope reduction in the ACL-deficient knee by 4.3 mm ± 3.6 ( p  < 0.001) at 200 N and 6.2 mm ± 4.3 ( p  < 0.001) at 400N of axial load. An increase of ITR of 2.3° ±2.8 ( p  < 0.001) at 200 N and by 4.0° ±4.1 ( p  < 0.001) at 400 N was observed after the osteotomy. In the ACL-reconstructed knee, ACL-graft forces decreased after slope reduction osteotomy by a mean of 14.7 N ± 9.8 ( p  < 0.001) at 200 N and 33.8 N ± 16.3 ( p  < 0.001) at 400N axial load, which equaled a relative decrease by a mean of 17.0% (SD ± 9.8%), and 33.1% (SD ± 18.1%), respectively. ATT and ITR were not significantly changed in the ACL-reconstructed knee. Testing of a tibial anterior drawing force in the ACL-deficient knee led to a significantly increased ATT by 2.7 mm ± 3.6 ( p  < 0.001) after the osteotomy. The ACL-reconstructed knee did not show a significant change (n.s.) in ATT after the osteotomy. However, ACL-graft forces detected a significant increase by 13.0 N ± 8.3 ( p  < 0.001) after the osteotomy with a tibial anterior drawer force, whereas the additional axial loading reduced this difference due to the osteotomy (5.3 N ± 12.6 (n.s.)). Conclusions Slope-reducing osteotomy decreased anterior tibial translation in the ACL-deficient and ACL-reconstructed knee under axial load, while internal rotation of the tibia increased in the ACL-deficient status after osteotomy. Especially in ACL revision surgery, the osteotomy protects the reconstructed ACL with significantly lower forces on the graft under axial load.

In this article we address the question ‘what is tracking in the mobile ecosystem’ through a comprehensive overview of the Software Development Kit (SDK). Our research reveals a complex infrastructural role for these technical objects connecting end-user data with app developers, third parties and dominant advertising platforms like Google and Facebook. We present an innovative theoretical framework which we call a data monadology to foreground this interrelationship, predicated on an economic model that exchanges personal data for the infrastructural services used to build applications. Our main contribution is an SDK taxonomy, which renders them more transparent and observable. We categorise SDK services into three main categories: (i) Programmatic AdTech for monetisation; (ii) App Development, for building, maintaining and offering additional artificial intelligence features and (iii) App Extensions which more visibly embed third parties into apps like maps, wallets or other payment services. A major finding of our analysis is the special category of the Super SDK, reserved for platforms like Google and Facebook. Not only do they offer a vast array of services across all three categories, making them indispensable to developers, they are super conduits for personal data and the primary technical means for the expansion of platform monopolisation across the mobile ecosystem.

Purpose The acromioclavicular ligament complex (ACLC) is the primary stabilizer against horizontal translation with the superior ACLC providing the main contribution. The purpose of this study was to evaluate the specific regional contributions in the superior half of ACLC, where the surgeon can easily access and repair or reconstruct, for posterior translational and rotational stability. Methods The superior half of ACLC was divided into three regions; Region A (0°–60°): an anterior 1/3 region of the superior half of ACLC, Region B (60°–120°): a superior 1/3 region of the superior half of ACLC, and Region C (120°–180°): a posterior 1/3 region of the superior half of ACLC. Fifteen fresh-frozen cadaveric shoulders were used. Biomechanical testing was performed to evaluate the resistance force against passive posterior translation (10 mm) and the resistance torque against passive posterior rotation (20°) during the following the four conditions. (1) Stability was tested on all specimens in their intact condition ( n  = 15). (2) The ACLC was dissected and stability was tested ( n  = 15). (3) Specimens were randomly divided into three groups by regions of suturing. Stability was tested after suturing Region A, Region B, or Region C ( n  = 5 per group). (4) Stability was tested after suturing additional regions: Region A + B (0°–120°), Region B + C (60°–180°), or Region A + C (0°–60°, 120°–180°, n  = 5 per group). Results The translational force increased after suturing Region A when compared with dissected ACLC ( P  = 0.025). The force after suturing Region A + B was significantly higher compared to the dissected ACLC ( P  < 0.001). The rotational torque increased after suturing Region A or Region B compared with dissected ACLC ( P  = 0.020, P  = 0.045, respectively). The torque after suturing the Region A + C was significantly higher compared to the dissected ACLC ( P  < 0.001). Conclusion The combined Region A + B contributed more to posterior translational stability than Region B + C or Region A + C. In contrast, combined Region A + C contributed more to posterior rotational stability than Region A + B or Region B + C. Based on these findings, surgical techniques restoring the entire superior ACLC are recommended to address both posterior translational and rotational stability of the AC joint.

Background Elliptical shape humeral head prostheses have been recently proposed to reflect a more anatomic shoulder replacement. However, its effect on obligate glenohumeral translation during axial rotation compared to a standard spherical head is still not well understood. The purpose of the study was to compare obligate humeral translation during axial rotation using spherical and elliptical shaped humeral head prostheses. It was hypothesized that the spherical head design would show significantly more obligate translation when compared to the elliptical design. Methods Six fresh-frozen cadaveric shoulders were utilized for biomechanical testing of internal (IR) and external (ER) rotation at various levels of abduction (0°, 30°, 45°, 60°) with lines of pull along each of the rotator cuff muscles. Each specimen underwent the following three conditions: (1) native; total shoulder arthroplasty (TSA) using (2) an elliptical and (3) spherical humeral head implant. Obligate translation during IR and ER was quantified using a 3-dimensional digitizer. The radius of curvature of the superoinferior and anteroposterior dimensions of the implants was calculated across each condition. Results Posterior and inferior translation as well as compound motion of spherical and elliptical heads during ER was similar at all abduction angles (P > 0.05, respectively). Compared to the native humeral head, both implants demonstrated significantly decreased posterior translation at 45° (elliptical: P = 0.003; spherical: P = 0.004) and 60° of abduction (elliptical: P < 0.001; spherical: P < 0.001). During internal rotation at 0° abduction, the spherical head showed significantly more compound motion (P = 0.042) compared to the elliptical head. The spherical implant also demonstrated increased anterior translation and compound motion during internal rotation at 60° abduction (P < 0.001) compared to the resting state. This difference was not significant for the native or elliptical head design at this angle (P > 0.05). Conclusion In the setting of TSA, elliptical and spherical head implants showed similar obligate translation and overall compound motion during axial rotation. A gained understanding of the consequences of implant head shape in TSA may guide future surgical implant choice for better recreation of native shoulder kinematics and potentially improved patient outcomes. Level of evidence Controlled Laboratory Study.

Purpose Posterolateral rotatory instability (PLRI) of the elbow occurs from an insufficient lateral collateral ligament complex (LCLC). For subacute LCLC injuries, lateral ulnar collateral ligament (LUCL) internal bracing rather than reconstruction may be a viable option. The purpose of the study was to compare the stabilizing effects of LUCL internal bracing to triceps tendon graft reconstruction in simulated PLRI. Methods Sixteen cadaveric elbows were assigned for either LUCL internal bracing ( n  = 8) or reconstruction with triceps tendon graft ( n  = 8). Specimen were mounted and a valgus rotational torque was applied to the ulna to test posterolateral rotatory stability. Posterolateral rotation was measured at 0°, 30°, 60°, 90° and 120° of elbow flexion. Cyclic loading was performed for 1000 cycles at 90° of elbow flexion. Three conditions were compared in each specimen: intact elbow, LUCL and radial collateral ligament (RCL) transected, and then either LUCL internal bracing or reconstruction with triceps tendon graft. Results Transection of the LUCL and RCL significantly increased posterolateral rotation in all degrees of elbow flexion compared to the intact condition ( P  < 0.05). Both LUCL internal bracing and reconstruction restored posterolateral rotatory stability to the native state between 0° and 120° of elbow flexion, with no significant difference in improvement between groups. Similarly, LUCL internal bracing and reconstruction groups showed no significant difference in posterolateral rotation compared to the intact condition during cyclic loading. Conclusions At time zero, both LUCL internal bracing and reconstruction with triceps tendon graft restored posterolateral rotatory stability. As such, this study supports the use of internal bracing as an adjunct to primary ligament repair in subacute PLRI.

Purpose The primary objective of this study is to evaluate the contact areas, contact pressures, and peak pressures in the medial compartment of the knee in six sequential testing conditions. The secondary objective is to establish how much the medial meniscus is able to extrude, secondary to soft tissue injury while keeping its roots intact. Methods Ten cadaveric knees were dissected and tested in six conditions: (1) intact meniscus, (2) 2 mm extrusion, (3) 3 mm extrusion, (4) 4 mm extrusion, (5) maximum extrusion, (6) capsular based meniscal repair. Knees were loaded with a 1000-N axial compressive force at 0°, 30°, 60°, and 90° for each condition. Medial compartment contact area, average contact pressure, and peak contact pressure data were recorded. Results When compared to the intact state, there was no statistically significant difference in medial compartment contact area at 2 mm of extrusion or 3 mm of extrusion (n.s.). There was a statistically significant decrease in contact area compared to the intact state at 4 mm ( p  = 0.015) and maximum extrusion ( p  < 0.001). The repair state was able to improve medial compartment contact area, and there was no statistically significant difference between the repair and the intact states (n.s.). No significant differences were found in the average contact pressure between the repair, intact, or maximum extrusion conditions at any flexion angle (n.s.). No significant differences were found in the peak contact pressure between the repair, intact, or maximum extrusion conditions at any flexion angle (n.s.). Conclusion In this in vitro model, medial meniscus extrusion greater than 4 mm reduced medial compartment contact area, but meniscal extrusion did not significantly increase pressure in the medial compartment. Additionally, meniscal centralization was effective in restoring the medial tibiofemoral contact area to intact state when the meniscal extrusion was secondary to meniscotibial ligament injury. The diagnosis of meniscal extrusion may not necessarily involve meniscal root injury. Since it is known that meniscal extrusion greater than 3 or 4 mm has a biomechanical impact on tibiofemoral compartment contact area and pressures, specific treatments can be established. Centralization restored medial compartment contact area to the intact state.

IntroductionFemoral nerve block (FNB) is a routinely used regional analgesic technique for anterior cruciate ligament (ACL) reconstruction. One method to balance the analgesic effect and functional impairment of FNBs may be to control the concentration of local anesthetics utilized for the block.Materials and methodsRetrospective chart review was performed on 390 consecutive patients who underwent ACL reconstruction between June 2014 and May 2017. Patients were divided into those who received a standard (0.5%-bupivacaine) or low (0.1–0.125%-bupivacaine) concentration single-shot FNB performed with ultrasound guidance. Maximum postoperative VAS, Post-Anaesthesia Care Unit (PACU) time prior to discharge, need for additional ‘rescue’ block, and intravenous postoperative narcotic requirements were recorded.ResultsA total of 268 patients (28.4 ± 11.9 years) were included for final analysis, with 72 patients in the low-concentration FNB group and 196 patients receiving the standard concentration. There were no differences in the maximum postoperative VAS between the low (6.4 ± 2.5) and standard (5.7 ± 2.9) concentration groups (P = 0.08). Similarly, the time from PACU arrival to discharge was not different between groups (P = 0.64). A sciatic rescue block was needed in 22% of patients with standard-dose FNB compared to 30% of patients receiving the low-concentration FNB (P = 0.20). Patients with a hamstring autograft harvest were more likely to undergo a postoperative sciatic rescue block compared to a bone-patellar tendon autograft (P = 0.005), regardless of preoperative block concentration. Quadriceps activation was preserved with low-concentration blocks.ConclusionsUsing 1/5th to 1/4th the standard local anesthetic concentration for preoperative femoral nerve block in ACL reconstruction did not significantly differ in peri-operative outcomes, PACU time, need for rescue blockade, or additional immediate opioid requirements.Level of EvidenceIII.

Background Metacarpal shaft fractures are common and can be treated nonoperatively. Shortening, angulation, and rotational deformity are indications for surgical treatment. Various forms of treatment with advantages and disadvantages have been documented. The purpose of the study was to determine the stability of fracture fixation with intramedullary headless compression screws in two types of metacarpal shaft fractures and compare them to other common forms of rigid fixation: dorsal plating and lag screw fixation. It was hypothesized that headless compression screws would demonstrate a biomechanical stronger construct. Methods Five matched paired hands (age 60.9 ± 4.6 years), utilizing non-thumb metacarpals, were used for comparative fixation in two fracture types created by an osteotomy. In transverse diaphyseal fractures, fixation by headless compression screws ( n  = 7) and plating ( n  = 8) were compared. In long oblique diaphyseal fractures, headless compression screws ( n  = 8) were compared with plating ( n  = 8) and lag screws ( n  = 7). Testing was performed using an MTS frame producing an apex dorsal, three point bending force. Peak load to failure and stiffness were calculated from the load-displacement curve generated. Results For transverse fractures, headless compression screws had a significantly higher stiffness and peak load to failure, means 249.4 N/mm and 584.8 N, than plates, means 129.02 N/mm and 303.9 N (both p  < 0.001). For long oblique fractures, stiffness and peak load to failure for headless compression screws were means 209 N/mm and 758.4 N, for plates 258.7 N/mm and 518.5 N, and for lag screws 172.18 N/mm and 234.11 N. There was significance in peak load to failure for headless compression screws vs plates ( p  = 0.023), headless compression screws vs lag screws ( p  < 0.001), and plates vs lag screws ( p  = 0.009). There was no significant difference in stiffness between groups. Conclusion Intramedullary fixation of diaphyseal metacarpal fractures with a headless compression screw provides excellent biomechanical stability. Coupled with lower risks for adverse effects, headless compression screws may be a preferable option for those requiring rapid return to sport or work. Level of evidence Basic Science Study, Biomechanics.

Purpose To evaluate tunnel widening and its relationship in loss of reduction and clinical outcomes in patients undergoing anatomic coracoclavicular ligament reconstruction (ACCR) using free tendon grafts for chronic acromioclavicular (AC) joint injuries. Methods A retrospective chart review was performed on patients undergoing ACCR for type III–VI AC joint injuries between January 2003 and December 2017. For radiographic analysis, pre- and post-operative coracoclavicular distance (CCD) and tunnel width of the medial and lateral clavicular bone tunnel were measured at the earliest (EPO) and latest postoperative follow-up (LPO). To determine the clinical relevance of improvement in clinical outcome score (American Shoulder and Elbow Surgeons score) substantial clinical benefit (SCB), and patient acceptable symptomatic state (PASS) thresholds were used. Results Twenty-four patients with a mean clinical follow-up of 37 ± 35 months (mean age 44.7 ± 13.4) were included in the study. Both the medial (5.6 ± 0.2 mm EPO –6.6 ± 0.7 mm LPO; p  < 0.001) and lateral (5.6 ± 0.5 mm EPO –6.8 ± 1 mm LPO ; p  < 0.001) clavicular bone tunnel showed significant widening from EPO to LPO. There was a significant loss of reduction at LPO (CCD LPO 10.1 ± 4 mm) compared to EPO (CCD EPO : 6.2 ± 3.8 mm) ( p  < 0.001). No significant correlation between loss of reduction and medial ( p  = 0.45; r  = − 0.06) or lateral ( p  = 0.69; r  = − 0.06) tunnel widening was found. Alterations in tunnel width were shown having no influence on clinical outcomes. Conclusion Patients who underwent ACCR using a free tendon graft for the treatment of chronic type III–VI ACJ injuries showed significant clavicular bone tunnel widening during the postoperative course. No correlation between tunnel widening and loss of reduction was shown with radiographic findings having no influence on clinical benefit and satisfaction. Study design Case Series; Level of evidence, IV.

IntroductionElliptical shape humeral head prostheses have been proposed to reflect a more anatomic shoulder replacement. Its effect on the rotational range of motion (ROM) compared to a standard spherical head is still not understood. The purpose was to investigate if there would be a difference in rotational ROM when comparing elliptical and spherical prosthetic heads in a dynamic shoulder model. The authors hypothesized that the use of elliptical heads would result in significantly more rotational ROM compared to the spherical head design.Materials and methodsSix fresh-frozen, cadaveric shoulders were evaluated using a dynamic shoulder model. After being tested in the native condition, each specimen underwent 6 conditions in the hemiarthroplasty state: (1) matched-fit spherical head, (2) oversized spherical head, (3) undersized spherical head, (4) matched-fit elliptical head, (5) oversized elliptical head, and (6) undersized elliptical head. Following conversion to total shoulder arthroplasty (TSA), the 6 prior conditions were rerun. Each condition was tested at 0°, 30° and 60° of glenohumeral abduction. Rotational ROM was quantified using 3-dimensional tracking, while dynamically applying alternating forces for internal and external rotation via the rotator cuff tendons.ResultsElliptical and spherical prosthetic heads showed no significant difference in the degree of the total, internal, and external rotational ROM for both the hemiarthroplasty and TSA state. Conversion from hemiarthroplasty to TSA resulted in less degree of total rotational ROM for both head designs in all abduction positions, without reaching statistical significance. There was a significant decrease in total, internal, and external rotational ROM for both elliptical and spherical heads in every replacement condition, when comparing 0° to 30° and 60° of abduction (P < 0.05, respectively).ConclusionIn a dynamic shoulder model, elliptical and spherical prosthetic head designs showed no significant difference in the degree of the total, internal, and external rotational ROM in both the hemiarthroplasty and TSA state.Level of evidenceControlled laboratory study