Augmented Ulnar Collateral Ligament Repair With Structural Bioinductive Scaffold: A Biomechanical Study.

BACKGROUND: Elbow ulnar collateral ligament (UCL) repair with suture brace augmentation shows good time-zero biomechanical strength and a more rapid return to play compared with UCL reconstruction. However, there are concerns about overconstraint or stress shielding with nonabsorbable suture tape. Recently, a collagen-based bioinductive absorbable structural scaffold has been approved by the Food and Drug Administration for augmentation of soft tissue repair. PURPOSE/HYPOTHESIS: This study aimed to assess the initial biomechanical performance of UCL repair augmented with this scaffold. We hypothesized that adding the bioinductive absorbable structural scaffold to primary UCL repair would impart additional time-zero restraint to the valgus opening. STUDY DESIGN: Controlled laboratory study. METHODS: Eight cadaveric elbow specimens-from midforearm to midhumerus-were utilized. In the native state, elbows underwent valgus stress testing at 30o, 60o, and 90o of flexion, with a cyclical valgus rotational torque. Changes in valgus rotation from 2- to 5-N·m torque were recorded as valgus gapping. Testing was then performed in 4 states: (1) native intact UCL-with dissection through skin, fascia, and muscle down to an intact UCL complex; (2) UCL-transected-distal transection of the ligament off the sublime tubercle; (3) augmented repair with bioinductive absorbable scaffold; and (4) repair alone without scaffold. The order of testing of repair states was alternated to account for possible plastic deformation during testing. RESULTS: The UCL-transected state showed the greatest increase in valgus gapping of all states at all flexion angles. Repair alone showed similar valgus gapping to that of the UCL-transected state at 30° (P = .62) and 60° of flexion (P = .11). Bioinductive absorbable scaffold-augmented repair showed less valgus gapping compared with repair alone at all flexion angles (P = .021, P = .024, and P = .024 at 30°, 60°, and 90°, respectively). Scaffold-augmented repair showed greater gapping compared with the native state at 30° (P = .021) and 90° (P = .039) but not at 60° of flexion (P = .059). There was no difference when testing augmented repair or repair alone first. CONCLUSION: UCL repair augmented with a bioinductive, biocomposite absorbable structural scaffold imparts additional biomechanical strength to UCL repair alone, without overconstraint beyond the native state. Further comparative studies are warranted. CLINICAL RELEVANCE: As augmented primary UCL repair becomes more commonly performed, use of an absorbable bioinductive scaffold may allow for improved time-zero mechanical strength, and thus more rapid rehabilitation, while avoiding long-term overconstraint or stress shielding.

Optimal assessment for anterior talofibular ligament injury utilizing stress ultrasound entails internal rotation during plantarflexion.

OBJECTIVES: An optimal load and ankle position for stress ultrasound of the injured anterior talofibular ligament (ATFL) are unknown. The objectives of this study were to compare stress ultrasound and ankle kinematics from a 6 degree-of-freedom (6-DOF) robotic testing system as a reference standard for the evaluation of injured ATFL and suggest cut-off values for ultrasound diagnosis. METHODS: Ten fresh-frozen human cadaveric ankles were used. Loads and ankle positions examined by the 6-DOF robotic testing system were: 40 N anterior load, 1.7 Nm inversion, and 1.7 Nm internal rotation torques at 30° plantarflexion, 15° plantarflexion, and 0° plantarflexion. Bony translations were measured by ultrasound and a robotic testing system under the above conditions. After measuring the intact ankle, ATFL was transected at its fibular attachment under arthroscopy. Correlations between ultrasound and robotic testing systems were calculated with Pearson correlation coefficients. Paired t-tests were performed for comparison of ultrasound measurements of translation between intact and transected ATFL and unloaded and loaded conditions in transected ATFL. RESULTS: Good agreement between ultrasound measurement and that of the robotic testing system was found only in internal rotation at 30° plantarflexion (ICC â€‹= â€‹0.77; 95% confidence interval 0.27-0.94). At 30° plantarflexion, significant differences in ultrasound measurements of translation between intact and transected ATFL (p â€‹< â€‹0.01) were found in response to 1.7 Nm internal rotation torque and nonstress and stress with internal rotation (p â€‹< â€‹0.01) with mean differences of 2.4 â€‹mm and 1.9 â€‹mm, respectively. CONCLUSION: Based on the data of this study, moderate internal rotation and plantarflexion are optimal to evaluate the effects of ATFL injury when clinicians utilize stress ultrasound in patients. LEVEL OF EVIDENCE: III.

Scaffold-Free Bone Marrow-Derived Mesenchymal Stem Cell Sheets Enhance Bone Formation in a Weight-Bearing Rat Critical Bone Defect Model.

Researchers have been exploring alternative methods for bone tissue engineering, as current management of critical bone defects may be a significant challenge for both patient and surgeon with conventional surgical treatments associated with several potential complications and drawbacks. Recent studies have shown mesenchymal stem cell sheets may enhance bone regeneration in different animal models. We investigated the efficacy of implanted scaffold-free bone marrow-derived mesenchymal stem cell (BMSC) sheets on bone regeneration of a critical bone defect in a weight-bearing rat model. BMSCs were isolated from the femora of male Sprague-Dawley rats 5-6 weeks of age and cell sheets were produced on temperature-responsive culture dishes. Nine male Sprague-Dawley rats 6-8 weeks of age were utilized. A bilateral femoral critical bone defect was created with a bridge plate serving as internal fixation. One side was randomly selected and BMSC sheets were implanted into the bone defect (BMSC group), with the contralateral side receiving no treatment (control). Rats were anesthetized and radiographs were performed at 2-week intervals. At the 8-week time point, rats were euthanized, femurs harvested, and microcomputed tomography and histological analysis was performed. We found a statistically significant increase in new bone formation and bone volume fraction compared with the control. Histomorphometry analysis revealed a larger percent of newly formed bone and a higher total histological score. Our results suggest that scaffold-free BMSC sheets may be used in the management of large weight-bearing bone defects to complement a different surgical technique or as a standalone approach followed by internal fixation. However, further research is still needed.

Hindbrain REV-ERB nuclear receptors regulate sensitivity to diet-induced obesity and brown adipose tissue pathophysiology.

OBJECTIVE: The dorsal vagal complex (DVC) of the hindbrain is a major point of integration for central and peripheral signals that regulate a wide variety of metabolic functions to maintain energy balance. The REV-ERB nuclear receptors are important modulators of molecular metabolism, but their role in the DVC has yet to be established. METHODS: Male REV-ERBα/ß floxed mice received stereotaxic injections of a Cre expressing virus to the DVC to create the DVC REV-ERBα/ß double knockout (DVC RDKO). Control littermates received stereotaxic injections to the DVC of a green fluorescent protein expressing virus. Animals were maintained on a normal chow diet or a 60% high-fat diet to observe the metabolic phenotype arising from DVC RDKO under healthy and metabolically stressed conditions. RESULTS: DVC RDKO animals on high-fat diet exhibited increased weight gain compared to control animals maintained on the same diet. Increased weight gain in DVC RDKO animals was associated with decreased basal metabolic rate and dampened signature of brown adipose tissue activity. RDKO decreased gene expression of calcitonin receptor in the DVC and tyrosine hydroxylase in the brown adipose tissue. CONCLUSIONS: These results suggest a previously unappreciated role of REV-ERB nuclear receptors in the DVC for maintaining energy balance and metabolic rate potentially through indirect sympathetic outflow to the brown adipose tissue.

A Dynamic Elbow Testing Apparatus for Simulating Elbow Joint Motion in Varying Shoulder Positions.

Purpose: To develop and evaluate the capabilities of a dynamic elbow testing apparatus that simulates unconstrained elbow motion throughout the range of humerothoracic (HTA) abduction. Methods: Elbow flexion was generated by six computer-controlled electromechanical actuators that simulated muscle action, while six degree-of-freedom joint motion was measured using an optical tracking device. Repeatability of joint kinematics was assessed at four HTA angles (0°, 45°, 90°, 135°) and with two muscle force combinations (A1-biceps brachialis, brachioradialis and A2-biceps, brachioradialis). Repeatability was determined by comparing kinematics at every 10° of flexion over five flexion-extension cycles (0° to 100°). Results: Multiple muscle force combinations can be used at each HTA angle to generate elbow flexion. Trials showed that the testing apparatus produced highly repeatable joint motion at each HTA angle and with varying muscle force combinations. The intraclass correlation coefficient was greater than 0.95 for all conditions. Conclusions: Repeatable smooth cadaveric elbow motion was created that mimicked the in vivo situation. Clinical relevance: These results suggest that the dynamic elbow testing apparatus can be used to characterize elbow biomechanics in cadaver upper extremities.

Is There a Critical Dorsal Lunate Facet Size in Distal Radius Fractures That Leads to Dorsal Carpal Subluxation? A Biomechanical Study of the Dorsal Critical Corner.

PURPOSE: Intra-articular distal radius fractures are common and can be associated with carpal instability. Failure to address articular fragments linked to maintaining carpal stability can lead to radiocarpal subluxation or dislocation. The purpose of this study was to evaluate the size of a dorsal osteotomy in the dorsal/volar plane of the lunate facet that leads to dorsal carpal subluxation. METHODS: Dorsal lunate facet fractures were simulated twice in each of nine fresh-frozen cadavers. After completing a partial dorsal osteotomy in the radial/ulnar plane between the scaphoid and lunate facets, an osteotomy in the dorsal/volar plane was completed. Using a cutting jig, first an estimated 5-mm osteotomy, and then a 10-mm osteotomy (from the dorsal rim of the distal radius) were completed. The wrist was mounted in a custom jig and loaded with 100 N. Displacement of the lunate in the dorsal/volar plane compared with displacement in an intact specimen was evaluated and used to assess carpal subluxation. RESULTS: Lunate translation was 0 mm ± 0 mm in the intact state. The 5-mm osteotomy averaged 29% of the distal radius dorsal lunate facet in the dorsal/volar plane, and lunate translation was 0.7 mm ± 1.7 mm. The 10-mm osteotomy averaged 54% of the dorsal lunate facet in the dorsal/volar plane, and lunate translation was 2.8 mm ± 2.6 mm. Assuming a linear relationship from the osteotomies created, an osteotomy of an estimated ≥40% of the distal radius in the dorsal to volar plane resulted in substantial dorsal subluxation, although this specific osteotomy was not assessed in our study. CONCLUSIONS: Sequentially increased dorsal osteotomies of the dorsal lunate facet result in increased dorsal carpal subluxation. CLINICAL RELEVANCE: Distal radius fractures that include >40% of the "dorsal critical corner" are at risk for dorsal carpal subluxation and may require supplementary fixation.

The Effect of Elbow Flexion On Valgus Carrying Angle.

PURPOSE: This study aimed to examine the effect of flexion on valgus carrying angle in the human elbow using a dynamic elbow testing apparatus. METHODS: Active elbow motion was simulated in seven cadaveric upper extremities. Six electromechanical actuators simulated muscle action, while 6 degrees-of-freedom joint motion was measured with an optical tracking system to quantify the kinematics of the ulna with respect to the humerus as the elbow was flexed at the side position. Repeatability of the testing apparatus was assessed in a single elbow over five flexion-extension cycles. The varus angle change of each elbow was compared at different flexion angles with the arm at 0° of humerothoracic abduction or dependent arm position. RESULTS: The testing apparatus achieved excellent kinematic repeatability (intraclass correlation coefficient, >0.95) throughout flexion and extension. All elbows decreased their valgus carrying angle during flexion from 0° to 90° when the arm was maintained at 0° of humerothoracic abduction. Elbows underwent significant total varus angle change from full extension of 3.9° ± 3.4° (P = .007), 7.3° ± 5.2° (P = .01), and 8.9° ± 7.1° (P = .02) at 60°, 90°, and 120° of flexion, respectively. No significant varus angle change was observed between 0° and 30° of flexion (P = .66), 60° and 120° of flexion (P = .06), and 90° and 120° of flexion (P = .19). CONCLUSIONS: The dynamic elbow testing apparatus characterized a decrease of valgus carrying angle during elbow flexion and found that most varus angle changes occurred between 30° and 90° of flexion. All specimens underwent varus angle change until at least 90° of flexion. CLINICAL RELEVANCE: Our model establishes the anatomic decrease in valgus angle by flexion angle in vitro and can serve as a baseline for testing motion profiles of arthroplasty designs and ligamentous reconstruction in the dependent arm position. Future investigations should focus on characterizing motion profile change as the arm is abducted away from the body.

Digital Microfluidics for Microproteomic Analysis of Minute Mammalian Tissue Samples Enabled by a Photocleavable Surfactant.

Proteome profiles of precious tissue samples have great clinical potential for accelerating disease biomarker discovery and promoting novel strategies for early diagnosis and treatment. However, tiny clinical tissue samples are often difficult to handle and analyze with conventional proteomic methods. Automated digital microfluidic (DMF) workflows facilitate the manipulation of size-limited tissue samples. Here, we report the assessment of a DMF microproteomics workflow enabled by a photocleavable surfactant for proteomic analysis of minute tissue samples. The surfactant 4-hexylphenylazosulfonate (Azo) was found to facilitate fast droplet movement on DMF and enhance the proteomics analysis. Comparisons of Azo and n-Dodecyl ß-d-maltoside (DDM) using small samples of HeLa digest standards and MCF-7 cell digests revealed distinct differences at the peptide level despite similar results at the protein level. The DMF microproteomics workflow was applied for the sample preparation of ∼3 µg biopsies from murine brain tissue. A total of 1969 proteins were identified in three samples, including established neural biomarkers and proteins related to synaptic signaling. Going forward, we propose that the Azo-enabled DMF workflow has the potential to advance the practical clinical application of DMF for the analysis of size-limited tissue samples.

Screws or Sutures? A Pediatric Cadaveric Study of Tibial Spine Fracture Repairs.

BACKGROUND: Tibial spine fractures are common in the pediatric population because of the biomechanical properties of children's subchondral epiphyseal bone. Most studies in porcine or adult human bone suggest that suture fixation performs better than screw fixation, but these tissues may be poor surrogates for pediatric bone. No previous study has evaluated fixation methods in human pediatric knees. PURPOSE: To quantify the biomechanical properties of 2-screw and 2-suture repair of tibial spine fracture in human pediatric knees. STUDY DESIGN: Controlled laboratory study. METHODS: Cadaveric specimens were randomly assigned to either 2-screw or 2-suture fixation. A standardized Meyers-Mckeever type 3 tibial spine fracture was induced. Screw-fixation fractures were reduced with two 4.0-mm cannulated screws and washers. Suture-fixation fractures were reduced by passing 2 No. 2 FiberWire sutures through the fracture fragment and the base of the anterior cruciate ligament. Sutures were secured through bony tunnels over a 1-cm tibial cortical bridge. Each specimen was mounted at 30° of flexion. A cyclic loading protocol was applied to each specimen, followed by a load-to-failure test. Outcome measures were ultimate failure load, stiffness, and fixation elongation. RESULTS: Twelve matched pediatric cadaveric knees were tested. Repair groups had identical mean (8.3 years) and median (8.5 years) ages and an identical number of samples of each laterality. Ultimate failure load did not significantly differ between screw (mean ± SD, 143.52 ± 41.9 7 N) and suture (135.35 ± 47.94 N) fixations (P = .760). Screws demonstrated increased stiffness and decreased elongation, although neither result was statistically significant at the .05 level (21.79 vs 13.83 N/mm and 5.02 vs 8.46 mm; P = .076 and P = .069, respectively). CONCLUSION: Screw fixation and suture fixation of tibial spine fractures in human pediatric tissue were biomechanically comparable. CLINICAL RELEVANCE: Suture fixations are not biomechanically superior to screw fixations in pediatric bone. Pediatric bone fails at lower loads, and in different modes, compared with adult cadaveric bone and porcine bone. Further investigation into optimal repair is warranted, including techniques that may reduce suture pullout and "cheese-wiring" through softer pediatric bone. This study provides new biomechanical data regarding the properties of different fixation types in pediatric tibial spine fractures to inform clinical management of these injuries.

All-in-One digital microfluidics pipeline for proteomic sample preparation and analysis.

Highly sensitive and reproducible analysis of samples containing low amounts of protein is restricted by sample loss and the introduction of contaminants during processing. Here, we report an All-in-One digital microfluidic (DMF) pipeline for proteomic sample reduction, alkylation, digestion, isotopic labeling and analysis. The system features end-to-end automation, with integrated thermal control for digestion, optimized droplet additives for sample manipulation and analysis, and an automated interface to liquid chromatography with tandem mass spectrometry (HPLC-MS/MS). Dimethyl labeling was integrated into the pipeline to allow for relative quantification of the trace samples at the nanogram level, and the new pipeline was applied to evaluating cancer cell lines and cancer tissue samples. Several known proteins (including HSP90AB1, HSPB1, LDHA, ENO1, PGK1, KRT18, and AKR1C2) and pathways were observed between model breast cancer cell lines related to hormone response, cell metabolism, and cell morphology. Furthermore, differentially quantified proteins (such as PGS2, UGDH, ASPN, LUM, COEA1, and PRELP) were found in comparisons of healthy and cancer breast tissues, suggesting potential utility of the All-in-One pipeline for the emerging application of proteomic cancer sub-typing. In sum, the All-in-One pipeline represents a powerful new tool for automated proteome processing and analysis, with the potential to be useful for evaluating mass-limited samples for a wide range of applications.

Introduction of a Novel Sequential Approach to the Ponte Osteotomy to Minimize Spinal Canal Exposure.

Ponte osteotomy is an increasingly popular technique for multiplanar correction of adolescent idiopathic scoliosis. Prior cadaveric studies have suggested that sequential posterior spinal releases increase spinal flexibility. Here we introduce a novel technique involving a sequential approach to the Ponte osteotomy that minimizes spinal canal exposure. One fresh-frozen adult human cadaveric thoracic spine specimen with 4 cm of ribs was divided into three sections (T1-T5, T6-T9, T10-L1) and mounted for biomechanical testing. Each segment was loaded with five Newton meters under four conditions: baseline inferior facetectomy with supra/interspinous ligament release, superior articular process (SAP) osteotomy in situ, spinous process (SP) osteotomy in situ, and complete posterior column osteotomy with SP/SAP excision and ligamentum flavum release (PCO). Compared to baseline, in situ SAP osteotomy alone provided 3.5%, 7.6%, and 7.2% increase in flexion/extension, lateral bending, and axial rotation, respectively. In situ SP osteotomy increased flexion/extension, lateral bending, and axial rotation by 15%, 18%, and 10.3%, respectively. PCO increased flexion/extension, lateral bending, and axial rotation by 19.6%, 28.3%, and 12.2%, respectively. Our report introduces a novel approach where incremental increases in range of motion can be achieved with minimal spinal canal exposure and demonstrates feasibility in a cadaveric model.

Reoperation Rates Due to Adjacent Segment Disease Following Primary 1 to 2-Level Minimally Invasive Versus Open Transforaminal Lumbar Interbody Fusion.

STUDY DESIGN: Retrospective analysis of prospectively collected data. OBJECTIVE: To investigate the effect of the approach of the transforaminal lumbar interbody fusion [TLIF; open vs . minimally invasive (MIS)] on reoperation rates due to ASD at 2 to 4-year follow-up. SUMMARY OF BACKGROUND DATA: Adjacent segment degeneration is a complication of lumbar fusion surgery, which may progress to adjacent segment disease (ASD) and cause debilitating postoperative pain potentially requiring additional operative management for relief. MIS TLIF surgery has been introduced to minimize this complication but the impact on ASD incidence is unclear. MATERIALS AND METHODS: For a cohort of patients undergoing 1 or 2-level primary TLIF between 2013 and 2019, patient demographics and follow-up outcomes were collected and compared among patients who underwent open versus MIS TLIF using the Mann-Whitney U test, Fischer exact test, and binary logistic regression. RESULTS: Two hundred thirty-eight patients met the inclusion criteria. There was a significant difference in revision rates due to ASD between MIS and open TLIFs at 2 (5.8% vs . 15.4%, P =0.021) and 3 (8% vs . 23.2%, P =0.03) year follow-up, with open TLIFs demonstrating significantly higher revision rates. The surgical approach was the only independent predictor of reoperation rates at both 2 and 3-year follow-ups (2 yr, P =0.009; 3 yr, P =0.011). CONCLUSIONS: Open TLIF was found to have a significantly higher rate of reoperation due to ASD compared with the MIS approach. In addition, the surgical approach (MIS vs . open) seems to be an independent predictor of reoperation rates.

Reliability, Concurrent Validity, and Minimal Detectable Change of Timed Up and Go Obstacle Test in People With Stroke.

OBJECTIVE: The aims of this study were to investigate the psychometric property of the timed Up and Go Obstacle (TUGO) test in people with stroke. DESIGN: Cross-sectional design. SETTING: University based neurorehabilitation laboratory. PARTICIPANTS: Twenty-eight people with stroke and 30 healthy older adults. INTERVENTION: Not Applicable. OUTCOME MEASURES: The TUGO (obstacle heights: 0, 5, 17 cm) test completion times, Fugl-Meyer Assessment (FMA) score, ankle dorsiflexor and plantarflexor muscle strength, Berg Balance Scale (BBS) score, Narrow Corridor Walking Test (NCWT) completion time, timed Up and Go (TUG) test completion time, and Community Integrated Measure. RESULTS: Excellent inter-rater (intraclass correlation coefficient [ICC]=0.999-1.000) and test-retest reliabilities (ICC=0.917-0.975) were found for TUGO test completion times for all obstacle heights. The TUGO test completion times for all obstacle heights were significantly correlated with NCWT and TUG test completion times (r=0.817-0.912). Only TUGO test completion times for 0 and 5 cm obstacle heights showed significant correlations with BBS scores (r=-0.518 to -0.534), while the TUGO test completion time for the 17 cm obstacle height correlated significantly with FMA scores. The minimal detectable change and optimal cut-off values for TUGO test completion times for the 0, 5, and 17 cm obstacle heights were 2.54, 3.60, and 3.07 s, and 14.69, 14.76, and 16.10 s, respectively. CONCLUSION: The TUGO test is a reliable, valid, and easy-to-administer clinical measure to discriminate between people with stroke and healthy older adults.

Comparison of Database Searching Programs for the Analysis of Single-Cell Proteomics Data.

Single-cell proteomics is emerging as an important subfield in the proteomics and mass spectrometry communities, with potential to reshape our understanding of cell development, cell differentiation, disease diagnosis, and the development of new therapies. Compared with significant advancements in the "hardware" that is used in single-cell proteomics, there has been little work comparing the effects of using different "software" packages to analyze single-cell proteomics datasets. To this end, seven popular proteomics programs were compared here, applying them to search three single-cell proteomics datasets generated by three different platforms. The results suggest that MSGF+, MSFragger, and Proteome Discoverer are generally more efficient in maximizing protein identifications, that MaxQuant is better suited for the identification of low-abundance proteins, that MSFragger is superior in elucidating peptide modifications, and that Mascot and X!Tandem are better for analyzing long peptides. Furthermore, an experiment with different loading amounts was carried out to investigate changes in identification results and to explore areas in which single-cell proteomics data analysis may be improved in the future. We propose that this comparative study may provide insight for experts and beginners alike operating in the emerging subfield of single-cell proteomics.

The efficiency of genetically modified mesenchymal stromal cells combined with a functionally graded scaffold for bone regeneration in corticosteroid-induced osteonecrosis of the femoral head in rabbits.

Core decompression (CD) with mesenchymal stromal cells (MSCs) is an effective therapy for early-stage osteonecrosis of the femoral head (ONFH). Preconditioning of MSCs, using inflammatory mediators, is widely used in immunology and various cell therapies. We developed a three-dimensional printed functionally graded scaffold (FGS), made of ß-TCP and PCL, for cell delivery at a specific location. The present study examined the efficacy of CD treatments with genetically modified (GM) MSCs over-expressing PDGF-BB (PDGF-MSCs) or GM MSCs co-over-expressing IL-4 and PDGF-BB and preconditioned for three days of exposure to lipopolysaccharide and tumor necrosis factor-alpha (IL-4-PDGF-pMSCs) using the FGS for treating steroid-induced ONFH in rabbits. We compared CD without cell-therapy, with IL-4-PDGF-pMSCs alone, and with FGS loaded with PDGF-MSCs or IL-4-PDGF-pMSCs. For the area inside the CD, the bone volume in the CD alone was higher than in both FGS groups. The IL-4-PDGF-pMSCs alone and FGS + PDGF-MSCs reduced the occurrence of empty lacunae and improved osteoclastogenesis. There was no significant difference in angiogenesis among the four groups. The combined effect of GM MSCs or pMSCs and the FGS was not superior to the effect of each alone. To establish an important adjunctive therapy for CD for early ONFH in the future, it is necessary and essential to develop an FGS that delivers biologics appropriately and provides structural and mechanical support.

Distal Metaphyseal Ulnar Shortening Osteotomy Fixation: A Biomechanical Analysis.

PURPOSE: Ulnar shortening osteotomy can be used to treat ulnar impaction syndrome and other causes of ulnar wrist pain. Distal metaphyseal ulnar shortening osteotomy (DMUSO) is one technique that has been proposed to reduce the complications seen with a diaphyseal USO or a wafer resection. However, to our knowledge, the optimal fixation construct for DMUSO has not been studied. We sought to characterize the biomechanical stiffness and rotational stability of different DMUSO constructs. METHODS: A DMUSO was performed on 40 human cadaveric ulnas using 4 different fixation constructs (10 specimens per group): one 3.0 mm antegrade screw; two 2.2 mm antegrade screws; one 3.0 mm retrograde screw; and two 2.2 mm retrograde screws. Biaxial testing using axial load and cyclical axial torque was performed until failure, defined as 10° of rotation or 2 mm displacement. Specimens were assessed for stiffness at failure. Bone density was assessed using the second metacarpal cortical percentage. RESULTS: Bone density was similar between all 4 testing groups. Of the 4 groups, the 2 antegrade screw group exhibited the highest rotational stiffness of 232 ± 102 Nm/deg. In paired analysis, this was significantly greater than 1 retrograde screw constructs. In multivariable analysis, 2-screw constructs were significantly stiffer than 1 screw and antegrade constructs were significantly stiffer than retrograde. Maximum failure torque did not differ with orientation, but 2 screws failed at significantly higher torques. CONCLUSION: Using 2 screws for DMUSO fixation constructs may provide higher stiffness and maximum failure torque, and antegrade screw constructs may provide more stiffness than retrograde constructs. CLINICAL RELEVANCE: Antegrade screw fixation using 2 screws may provide the strongest construct for DMUSO. Antegrade fixation may be preferred because it avoids violating the distal radioulnar joint capsule and articular surface of the ulna.

Increasing the posterior tibial slope lowers in situ forces in the native ACL primarily at deep flexion angles.

High tibial osteotomy is becoming increasingly popular but can be associated with unintentional posterior tibial slope (PTS) increase and subsequent anterior cruciate ligament (ACL) degeneration. This study quantified the effect of increasing PTS on knee kinematics and in situ forces in the native ACL. A robotic testing system was used to apply external loads from full extension to 90° flexion to seven human cadaveric knees: (1) 200 N axial compressive load, (2) 5 Nm internal tibial + 10 Nm valgus torque, and (3) 5 Nm external tibial + 10 Nm varus torque. Kinematics and in situ forces in the ACL were acquired for the native and increased PTS state. Increasing PTS resulted in increased anterior tibial translation at 30° (1.8 mm), 60° (1.7 mm), and 90° (0.9 mm) flexion and reduced in situ force in the ACL at 30° (57.6%), 60° (69.8%), and 90° (75.0%) flexion in response to 200 N axial compressive load. In response to 5 Nm internal tibial + 10 Nm valgus torque, there was significantly less (39.0%) in situ force in the ACL at 90° flexion in the increased compared with the native PTS state. Significantly less in situ force in the ACL at 60° (62.8%) and 90° (67.0%) flexion was observed in the increased compared with the native PTS state in response to 5 Nm external tibial + 10 Nm varus torque. Increasing PTS affects knee kinematics and results in a reduction of in situ forces in the native ACL during compressive and rotatory loads at flexion angles exceeding 30°. In a controlled laboratory setting PTS increase unloads the ACL, affecting its natural function.

Increased superior translation following multiple simulated anterior dislocations of the shoulder.

PURPOSE: Recurrent shoulder dislocations can result in kinematic changes of the glenohumeral joint. The number of prior shoulder dislocations may contribute to increased severity of capsulolabral lesions. The kinematics of the glenohumeral joint following multiple dislocations remain poorly understood. The purpose of this study was to assess the kinematics of the glenohumeral joint during anterior dislocations of the shoulder, and more specifically, altered translational motion following multiple dislocations. The kinematics of the glenohumeral joint were hypothesized to change and correlate with the number of dislocations. METHODS: Eight fresh-frozen cadaveric shoulders were dissected free of all soft tissues except the glenohumeral capsule. Each joint was mounted in a robotic testing system. At 60 degrees of glenohumeral abduction, an internal and external rotational torque (1.1 Nm) were applied to the humerus, and the resulting joint kinematics were recorded. Anterior forces were applied to the humerus to anteriorly dislocate the shoulder and the resulting kinematics were recorded during each dislocation. Following each dislocation, the same rotational torque was applied to the humerus, and the resulting joint kinematics were also recorded. A repeated-measures analysis of variance (ANOVA) was used to compare the kinematics following each dislocation. RESULTS: During the 7th, 8th, 9th, and 10th dislocations, the humerus significantly translated superiorly compared with the shoulder during the 1st dislocation (p < 0.05). Following the 3rd, 4th, 5th, and 10th dislocations, the humeral head significantly translated superiorly compared with the shoulder following the 1st dislocation in the position of 60 degrees of abduction in response to external rotation torque (p < 0.05). CONCLUSION: Multiple anterior shoulder dislocations lead to abnormal translational kinematics and result in increased superior translation of the humerus. This may contribute to pathologic superior extension of capsulolabral injuries. Superior translation of the humerus with overhead motion in the setting of recurrent instability may also place the shoulder at risk for extension of the capsulolabral injuries.

Direction of non-recoverable strain in the glenohumeral capsule following multiple anterior dislocations: Implications for anatomic Bankart repair.

The study aimed to analyze the direction of non-recoverable strain and determine the optimal direction for anatomic capsular plication within four sub-regions of the inferior glenohumeral capsule following multiple dislocations. Seven fresh-frozen cadaveric shoulders were dissected. A grid of strain markers was affixed to the inferior glenohumeral capsule. Each joint was mounted in a 6-degree-of-freedom robotic testing system and repeatedly dislocated in the anterior direction 10 times at 60° of abduction and 60° of external rotation of the glenohumeral joint. The 3D positions of the strain markers were compared before and after dislocations to define the non-recoverable strain. The strain map was divided into four sub-regions. The angles of deviation between each maximum principle strain vector and the anterior band of the inferior glenohumeral ligament (AB-IGHL) or posterior band of the IGHL (PB-IGHL) for the anterior and posterior regions of the capsule were determined. The mean direction of all strain vectors in each sub-region was categorized. The direction of the non-recoverable strain in the anterior-band and anterior-axillary-pouch sub-regions was categorized as parallel to the AB-IGHL, whereas the posterior-axillary-pouch and posterior-band sub-regions were mostly perpendicular to the PB-IGHL. Clinical Significance: Plication of the anteroinferior capsule parallel to the AB-IGHL may be preferred during arthroscopic Bankart repair to restore anatomy; posteroinferior capsular plication may also be necessary and best performed perpendicular to the PB-IGHL. The direction of the capsular injury remains the same irrespective of the number of dislocations. This study provides the scientific and quantitative rationale for an anatomic approach to capsular plication.