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Background: The use of patient-specific instruments (PSIs) for osteotomies is becoming more popular in orthopaedic surgery for correcting mechanical axis and posttraumatic deformities. However, the PSI reduction guides have great potential for intraoperative deformation, which adversely affects the accuracy of the procedure., Purpose: To conduct a finite element analysis (FEA) to analyze different design parameters to improve the intraoperative stability of the reduction guides., Study Design: Descriptive laboratory study., Methods: A reduction guide with a rectangular cross section and four 4-mm K-wire slots was simplified, and the following parameters were modified: width, height, profile design, K-wire thickness, and positions. Bending and torsional moments were applied to the guide construct and guide deformation and equivalent stress were determined using FEA., Results: Increasing the profile height by 25% resulted in a 44% reduction in guide deformation for bending (37% for torsion). A 25% increase in profile width led to an 18% deformation reduction for bending (22% for torsion). Transverse K-wire slots resulted in 51% less deformation in torsion compared with longitudinally oriented slots. Placing the central K-wire slots 25% closer to the osteotomy reduced guide deformation by 20% for bending and 11% for torsion., Conclusion: The most effective methods to increase reduction guide stability are to increase the guide height and reduce the central K-wire distance to the osteotomy., Clinical Relevance: When performing opening or closing wedge osteotomies, which mainly involve bending of the guide, a high-profile guide and longitudinally oriented K-wire slots should be used. When torque is expected as in rotational osteotomies, the K-wire holes in guides should be oriented transversely to reduce intraoperative deformation., Competing Interests: One or more of the authors has declared the following potential conflict of interest or source of funding: S.F.F. has received consulting fees from Medacta International SA, Zimmer Biomet, and Karl Storz and is a board member for ESSKA-EKA Osteotomy Committee. AOSSM checks author disclosures against the Open Payments Database (OPD). AOSSM has not conducted an independent investigation on the OPD and disclaims any liability or responsibility relating thereto., (© The Author(s) 2024.)

Background: Hinge fractures in varus-producing distal femoral osteotomies (DFOs) lead to decreased axial and torsional stability. The purpose of this study was to assess (1) which hinge width has a high risk of hinge fracture in DFO for lateral opening wedge (LOW) and medial closing wedge (MCW) osteotomies, (2) which osteotomies allow for greater correction before risking a fracture, (3) whether patient-specific instrumentation (PSI) allows accurate hinge width planning., Methods: Thirty porcine femoral bones were divided into two groups: LOW, MCW with hinge widths of 5 mm, 7.5 mm, and 10 mm as subgroups. Osteotomies were performed in a PSI-navigated fashion. A force parallel to the longitudinal bone axis was applied in a uniaxial testing machine until a fracture occurred., Results: The maximum correction was 6.7 ± 1.1° for LOW and 13.4 ± 1.9° for MCW (β 0  < 0.001 , β 1  = 0.002, β 2  = 0.02 , β 3  = 0.005). The relative error of the planned hinge width compared with the actual hinge width was -3.7 ± 12.3% for LOW (P = 0.25) and 12.3 ± 13.1% for MCW (P = 0.003)., Conclusions: Increasing the hinge width allows for greater correction in MCW osteotomies. For LOW osteotomies, a smaller hinge width seems to be advantageous because it allows a greater correction without the risk of hinge fracture. With PSI-guided LOW osteotomies, the planned hinge width could be achieved intraoperatively with greater accuracy than with MCW osteotomies. However, the MCW osteotomy appears to be the preferred option when larger corrections are desired because a larger correction angle can be achieved without the risk of intraoperative hinge fracture., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

Study Design: Biomechanical cadaveric study., Objective: The goal of this study was to analyze the effects of an endoscopic transpedicular approach with different drill diameters (6 and 8 mm) and compare them with the intact native side. In addition, the influence of bone quality on the resistance of the pedicle was investigated., Summary of Background Data: Clinical studies have repeatedly highlighted the benefits of endoscopic transpedicular decompression for downmigrated lumbar disc herniations. However, the biomechanical effects on pedicle stability have not been studied up to now., Materials and Methods: Twenty-four vertebras originating from four fresh-frozen cadavers were tested under uniaxial compression load in a ramp-to-failure test: (1) the tunneled pedicle on one side, and (2) the native pedicle on the other side. Twelve lumbar vertebrae were assigned to drill diameter of 6 mm and the other 12 to diameter of 8 mm., Results: The median ratio of sustained force for the operated side compared with the intact contralateral side is equal to 74% (63-88) for both drill diameters combined. An 8 mm transpedicular approach recorded an axial resistance of 77% (60-88) compared with the intact contralateral side ( P =0.002). A 6 mm approach resulted in an axial resistance of 72% (66-84) compared with the intact opposite side ( P =0.01). No significant difference between the two different drill diameters was recorded ( P =1). For all three subgroups (intact, 8 mm, 6 mm) the Hounsfield units-values and the absolute resistance force showed significant correlations (intact: ρ=0.859; P <0.001; 8 mm: ρ=0.902; P <0.001; 6 mm: ρ=0.835; P <0.001)., Conclusion: The transpedicular approach significantly reduces the axial resistance force of the pedicle, which may lead to pedicle fracture. Bone quality correlated positively with the absolute resistance force of the pedicle, whereas the influence of the drill hole diameter plays only a limited role., Competing Interests: M.F. reports being a Consultant for Incremed (Balgrist University Startup), Zimmer Biomet, Medacta, and 25 Segments (Balgrist Startup). The remaining authors report no conflicts of interest., (Copyright © 2023 The Author(s). Published by Wolters Kluwer Health, Inc.)

Early aseptic loosening is caused by deficient osteointegration of the femoral stem due to increased micromotions and represents a common mode of failure in uncemented total hip arthroplasty (THA). This study hypothesized that a higher femoral offset, a smaller stem size and obesity increase femoral micromotion, potentially resulting in early aseptic loosening. A finite element analysis was conducted based on computed tomography segmented model of four patients who received a THA with a triple-tapered straight stem (Size 1, 3, 6). The influence of femoral stem offset (short neck, standard, lateral), head length (S to XXL), femoral anteversion and obesity during daily activities of fast walking and stair climbing was analyzed. The micromotions for the femoral stem zones were compared to a threshold representing a value above which only partial osseointegration is expected. The minimum femoral offset configuration compared to the maximum offset configuration (short neck stem, S head vs. lateral stem, XXL head) leads to a relative mean micromotion increase of 24% for the upper stem zone. Increasing the body weight (body mass index 30-35 kg/m 2 ) increases the micromotion by 20% for all stem zones. The obese population recorded threshold-exceeding micromotions for stem sizes 1 and 3 for all offset configurations during stair climbing. Higher femoral offset, a smaller stem size, and higher loading due to obesity lead to an increase in micromotion between the prosthesis and proximal femur and represent a risk configuration for impaired osseointegration of a triple-tapered straight stem, especially when these three factors are present simultaneously., (© 2024 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

Background: The Latarjet procedure is widely used to address anterior shoulder instability, especially in case of glenoid bone loss. Recently, cortical suture button fixation for coracoid transfer has been used to mitigate complications seen with screw placement. The aim of this biomechanical study was to evaluate the stability of a novel and cost-effective cow-hitch suture button technique, designed to be performed through a standard open deltopectoral approach, and compare this to a well-established double suture button technique., Materials and Methods: We randomly assigned 12 fresh frozen cadaveric shoulders to undergo the Latarjet procedure with either 4 suture button (S&N EndoButton) fixations (SB group; n = 6, age 72 ± 9.8 years) or cow-hitch suture button technique using a 1.7-mm FiberTape looped sequentially in 2 suture buttons (Arthrex Pectoralis Button) placed from anterior on the posterior glenoid (CH-SB group; n = 6, age 73 ± 9.3 years). After fixation, all shoulders underwent biomechanical testing with direct loading on the graft via a material testing system. Cyclic loading was performed for 100 cycles (10-100 N) to determine axial displacement with time; each graft was then monotonically loaded to failure., Results: The maximum cyclic displacement was 4.3 ± 1.6 mm for the cow-hitch suture button technique and 5.0 ± 1.7 mm for the standard double suture button technique (P = .46). Ultimate load to failure and stiffness were, respectively, 190 ± 82 N and 221 ± 124 N/mm for the CH-SB technique and 172 ± 48 N and 173 ± 34 N/mm for the standard double SB technique (P = .66 and .43). The most common failure mode was suture cut-through at the anteroinferior aspect of the glenoid for both fixation groups., Conclusions: The cow-hitch suture button technique resulted in a similar elongation, stiffness, and failure load compared to an established double suture button technique. Therefore, this cost-effective fixation may be an alternative, eligible for open approaches, to the established double suture button techniques., (Copyright © 2023 The Author(s). Published by Elsevier Inc. All rights reserved.)

Background: Avulsion of the greater tuberosity (GT) due to traumatic anterior shoulder dislocation (ASD) is a commonly observed fracture pattern. After closed reduction of the dislocated humerus, the GT typically reduces itself into its anatomic position enabling the patient to undergo conservative treatment. The aim of this study was to retrospectively review a consecutive series of patients with conservatively treated GT avulsion fractures after closed reduction of an ASD and analyze radiographic outcome, shoulder function and glenohumeral stability and the conversion rate to surgical treatment., Methods: All patients who underwent closed reduction of a GT avulsion fracture after ASD with the primary intention of conservative treatment between 2017 and 2022 were included. Complications (i.e. conversion to surgical treatment), shoulder function assessed with the American Shoulder and Elbow Surgeons score and subjective shoulder value, instability assessed with the Western Ontario Shoulder Instability score, radiological impingement (greater tuberosity index = GTI and impingement index = II) and GT fracture pattern were assessed as outcome measurements., Results: A total of 29 patients (mean age 44 years, 27% female) with a mean follow-up of 32.6 (range, 8-96) months were enrolled. Seven patients (24%) underwent surgery due to secondary displacement (n = 4, 14%) or impingement symptoms (n = 3, 10%). All patients who underwent secondary surgery showed a multifragmentary fracture pattern of the GT. Shoulder stiffness (n = 7) and neuropraxia of the axillary nerve (n = 3) were observed temporarily and resolved during the follow-up period. The American Shoulder and Elbow Surgeons and subjective shoulder value of the conservatively treated patients at the last follow-up was 89.2 ± 19.1 respectively 86 ± 18.2%. No recurrent glenohumeral dislocation was documented. The mean Western Ontario Shoulder Instability score at last follow-up was 8(0-71). The mean GTI decreased from 1.2 ± 0.1 after ASD to 1.1 ± 0.1 at the last follow-up ( P  = .002). The mean II decreased from 0.6 ± 0.5 after ASD to 0.4 ± 0.3 at the last follow-up ( P  = .110)., Conclusion: The GT avulsion fragment reduces typically into a close to anatomic position after closed reduction and the GTI even improves with further conservative treatment over time. Close radiological follow-up is necessary to rule out secondary displacement which occurs typically in a multifragmentary fracture pattern. Patients without the need for surgery showed good clinical outcomes without recurrence of glenohumeral instability., (© 2024 The Authors.)

Squatting is a common daily activity and fundamental exercise in resistance training and closed kinetic chain programs. The aim of this study was to investigate the effects of an experimentally induced weakness of the gluteal muscles on joint kinematics, reactions forces (JRFs), and dynamic balance performance during deep bilateral squats in healthy young adults. Ten healthy adults received sequential blocks of (1) branch of the superior gluteal nerve to the tensor fasciae latae (SGNtfl) muscle, (2) superior gluteal nerve (SGN), and (3) inferior gluteal nerve (IGN) on the dominant right leg. At the control condition and following each block, the participants were instructed to perform deep bilateral squats standing on two force plates. Hip, knee, ankle, and pelvis kinematics did not differ significantly following iatrogenic weakness of gluteal muscles. The most important finding was the significant differences in JRFs following SGN and IGN block, with the affected hip, patellofemoral, and ankle joint demonstrating lower JRFs, whereas the contralateral joints demonstrated significantly higher JRFs, especially the patellofemoral joint which demonstrated an average maximum difference of 1.43 x body weight compared with the control condition. When performing a deep bilateral leg squat under SGN and IGN block, the subjects demonstrated an increased center of pressure (CoP) range and standard deviation (SD) in mediolateral compared with the control condition. These results imply that squat performance changes significantly following weakness of gluteal muscles and should be considered when assessing and training athletes or patients with these injuries., (© 2023 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals LLC on behalf of Orthopaedic Research Society.)

Purpose: The medial malleolar osteotomy is commonly performed to gain access to the medial talar dome for treatment of osteochondral lesions of the talus. The primary aim of this study was to assess osseous healing based on postoperative radiographs to determine consolidation, non-union and malreduction rates., Methods: Sixty-seven cases were reviewed where an oblique uniplanar medial malleolar osteotomy was performed to gain access to the medial talar dome for addressing an osteochondral lesion. Two, respectively three fully threaded 3.5 mm corticalis screws were used to fixate the osteotomy. Postoperative radiographs were reviewed to assess consolidation, non-union, malreduction and dislocation of the osteotomy., Results: Out of 67 patients, 66 patients had a consolidation of the osteotomy. 23.9% of the cases showed malreduction of the osteotomy. One patient suffered a non-union, which required a revision surgery. No significant difference was shown between two and three screws used for fixation in terms of malreduction and consolidation of the osteotomy. Eighty-four percent of the patients underwent hardware removal due to pain or medial impingement., Conclusion: The oblique medial malleolar osteotomy is a safe and relatively simple procedure with a high consolidation rate and low revision providing excellent exposure of the talus. The moderately high malreduction rate and required hardware removal surgery by most of the patients are relevant factors which should be considered before performing this surgery., Level of Evidence: Level III, retrospective cohort study., (© 2022. The Author(s), under exclusive licence to Springer-Verlag GmbH Germany, part of Springer Nature.)

Background: Autologous matrix-induced chondrogenesis (AMIC) for the treatment of osteochondral lesions of the talus (OLT) results in favorable clinical outcomes, yet high reoperation rates. The aim of this study was to report and analyze typical complications and their risk factors after AMIC for OLT., Methods: A total of 127 consecutive patients with 130 AMIC procedures for OLT were retrospectively assessed. All AMIC procedures were performed in an open fashion with 106 (81.5%) cases requiring a malleolar osteotomy (OT) to access the OLT. Seventy-one patients (54.6%) underwent subsequent surgery. These cases were evaluated at a mean follow-up of 3.1 years (±2.5) for complications reviewing postoperative imaging and intraoperative findings during revision surgery. Six patients (8.5%) were lost to follow-up. Regression model analysis was conducted to identify factors that were associated with AMIC-related complications., Results: Among the 65 (50%) patients who required revision surgery, 18 patients (28%) demonstrated AMIC-related complications with deep fissuring (83%) and thinning (17%) of the AMIC graft. Conversely, 47 patients (72%) underwent subsequent surgery due to AMIC-unrelated reasons including isolated removal of symptomatic hardware (n = 17) and surgery addressing concomitant pathologies with (n = 25) and without hardware removal (n = 5). Previous prior cartilage repair surgery was significantly associated with AMIC graft-associated complications in patients undergoing revision surgery ( P  = .0023). Among age, body mass index, defect size, smoking, and bone grafting, smoking was the only factor showing statistical significance with an odds ratio of 3.7 (95% CI 1.24, 10.9; P  = .019) to undergo revision surgery due to graft-related complications, when adjusted for previous cartilage repair surgery., Conclusion: The majority of revision surgeries after AMIC for OLT are unrelated to the performed AMIC graft but frequently address symptomatic hardware and concomitant pathologies. Both smoking and previous cartilage repair surgery seem to significantly increase the risk of undergoing revision surgery due to AMIC-related complications., Level of Evidence: Level IV, case series., Competing Interests: The author(s) declared no potential conflicts of interest with respect to the research, authorship, and/or publication of this article. ICMJE forms for all authors are available online., (© The Author(s) 2023.)

Purpose: Intraoperative hinge fractures in distal femur osteotomies represent a risk factor for loss of alignment and non-union. Using finite element analysis, the goal of this study was to investigate the influence of different hinge widths and osteotomy corrections on hinge fractures in medial closed-wedge and lateral open-wedge distal femur osteotomies., Methods: The hinge was located at the proximal margin of adductor tubercle for biplanar lateral open-wedge and at the upper border of the lateral femoral condyle for biplanar medial closed-wedge distal femur osteotomies, corresponding to optimal hinge positions described in literature. Different hinge widths (5, 7.5, 10 mm) were created and the osteotomy correction was opened/closed by 5, 7.5 and 10 mm. Tensile and compressive strain of the hinge was determined in a finite element analysis and compared to the ultimate strain of cortical bone to assess the hinge fracture risk., Results: Doubling the correction from 5 to 10 mm increased mean tensile and compressive strain by 50% for lateral open-wedge and 48% for medial closed-wedge osteotomies. A hinge width of 10 mm versus 5 mm showed increased strain in the hinge region of 61% for lateral open-wedge and 32% for medial closed-wedge osteotomies. Medial closed-wedge recorded a higher fracture risk compared to lateral open-wedge osteotomies due to a larger hinge cross-section area (60-67%) for all tested configurations. In case of a 5 mm hinge, medial closed-wedge recorded 71% higher strain in the hinge region compared to lateral open-wedge osteotomies., Conclusion: Due to morphological features of the medial femoral condyle, finite element analysis suggests that lateral-open wedge osteotomies are the preferable option if larger corrections are intended, as a thicker hinge can remain without an increased hinge fracture risk., (© 2023. The Author(s).)

Purpose: Functional internal rotation (IR) is a combination of extension and IR. It is clinically often limited after reverse total shoulder arthroplasty (RTSA) either due to loss of extension or IR in extension. It was the purpose of this study to determine the ideal in-vitro combination of glenoid and humeral components to achieve impingement-free functional IR., Methods: RTSA components were virtually implanted into a normal scapula (previously established with a statistical shape model) and into a corresponding humerus using a computer planning program (CASPA). Baseline glenoid configuration consisted of a 28 mm baseplate placed flush with the posteroinferior glenoid rim, a baseplate inclination angle of 96° (relative to the supraspinatus fossa) and a 36 mm standard glenosphere. Baseline humeral configuration consisted of a 12 mm humeral stem, a metaphysis with a neck shaft angle (NSA) of 155° (+ 6 mm medial offset), anatomic torsion of -20° and a symmetric PE inlay (36mmx0mm). Additional configurations with different humeral torsion (-20°, + 10°), NSA (135°, 145°, 155°), baseplate position, diameter, lateralization and inclination were tested. Glenohumeral extension of 5, 10, 20, and 40° was performed first, followed by IR of 20, 40, and 60° with the arm in extension of 40°-the value previously identified as necessary for satisfactory clinical functional IR. The different component combinations were taken through simulated ROM and the impingement volume (mm 3 ) was recorded. Furthermore, the occurrence of impingement was read out in 5° motion increments., Results: In all cases where impingement occurred, it occurred between the PE inlay and the posterior glenoid rim. Only in 11 of 36 combinations full functional IR was possible without impingement. Anterosuperior baseplate positioning showed the highest impingement volume with every combination of NSA and torsion. A posteroinferiorly positioned 26 mm baseplate resulting in an additional 2 mm of inferior overhang as well as 6 mm baseplate lateralization offered the best impingement-free functional IR (5/6 combinations without impingement). Low impingement potential resulted from a combination of NSA 135° and + 10° torsion (4/6 combinations without impingement), followed by NSA 135° and -20° torsion (3/6 combinations without impingement) regardless of glenoid setup., Conclusion: The largest impingement-free functional IRs resulted from combining a posteroinferior baseplate position, a greater inferior glenosphere overhang, 90° of baseplate inclination angle, 6 mm glenosphere lateralization with respect to baseline setup, a lower NSA and antetorsion of the humeral component. Surgeons can employ and combine these implant configurations to achieve and improve functional IR when planning and performing RTSA., Level of Evidence: Basic Science Study, Biomechanics., (© 2023. The Author(s).)

Background: For humeral flexion and elevation, most relevant for daily activities with reverse total shoulder arthroplasty, the anterior and lateral deltoid muscles are most important. However, how this direction of movement is best supported with the glenosphere position is not fully understood. We hypothesized that both inferior positioning and posterior positioning of the glenosphere may best support this direction of movement., Methods: A validated, anatomic biomechanical shoulder model was modified to host a reverse shoulder prosthesis. The glenoid baseplate was altered to allow inferior, lateral, and posterior center-of-rotation (COR) offsets. An optical tracking system was used to track the excursion of ropes simulating portions of various shoulder muscles during humeral abduction, elevation, and flexion., Results: The inferior COR offset resulted in a significant increase in the deltoid moment arm in all 3 planes of motion. The lateral COR offset showed a significantly lower posterior deltoid moment arm during humeral abduction and a significantly lower lateral deltoid moment arm during humeral elevation. The posterior offset showed significantly larger anterior and lateral deltoid moment arms during humeral flexion., Discussion and Conclusion: Owing to the oblique direction of the deltoid muscle across the shoulder joint, an inferior offset of the COR in reverse total shoulder arthroplasty increases the deltoid moment arm during abduction, elevation, and flexion, whereas it mainly supports humeral flexion at a posterior offset. For humeral elevation and flexion, favorable positioning of the glenosphere may, therefore, be defined by a more inferior and posterior placement compared with the non-offset position., (Copyright © 2019 Journal of Shoulder and Elbow Surgery Board of Trustees. Published by Elsevier Inc. All rights reserved.)