Investigating the biomechanical behaviour of tendon-loaded wrist joint using web-like kinematic network model.

The complexity of wrist anatomy and mechanics makes it challenging to develop standardized measurements and establish a normative reference database of wrist biomechanics despite being studied extensively. Moreover, heterogeneity factors in both demographic characteristics (e.g. gender) and physiological properties (e.g. ligament laxity) could lead to differences in biomechanical behaviour even within healthy groups. We investigated the kinematic behaviour of the carpal bones by creating a virtual web-like network between the bones using electromagnetic (EM) sensors. Our objective was to quantify the changes in the carpal bones' biomechanical relative motions and orientations during active wrist motion in the form of orb-web architecture. Models from five cadaveric specimens at different wrist positions: (1) Neutral to 30° Extension, (2) Neutral to 50° Flexion, (3) Neutral to 10° Radial Deviation, (4) Neutral to 20° Ulnar Deviation, and (5) Dart-Throw Motion - Extension (30° Extension/10° RD) to Dart-Throw Motion Flexion (50° Flexion/20° UD), in both neutral and pronated forearm have been analyzed. Quantification analyses were done by measuring the changes in the network thread length, as well as determining the correlation between the threads at different wrist positions. We observed similarities in the kinematic web-network patterns across all specimens, and the interactions between the network threads were aligned to the carpal bones' kinematic behaviour. Furthermore, analyzing the relative changes in the wrist web network has the potential to address the heterogeneity challenges and further facilitate the development of a 3D wrist biomechanics quantitative tool.

Biomechanical evaluation of porcine lens capsule with and without nucleus after capsulotomy - Finite element analysis.

Previous studies have shown that the nucleus could offer structural support to the lens capsule. This study investigated the biomechanical performance of porcine lens with and without nucleus for 4 mm, 4.5 mm, 5 mm, 5.5 mm and 6 mm capsulotomy and its potential impact on the stretch ratio of capsular bag when the anterior capsulotomy edge was stretched. Our simulation results showed higher strain for the capsular bag with nucleus, which is crucial for the porcine lens to tolerate more stretch without failure. This simulation could support future study on the optimization of capsulotomy based on patient specific condition, that is, the geometry of lens.

Fatigue following head and neck cancer radiotherapy: a systematic review of dose correlates.

INTRODUCTIONS: Radical radiotherapy (RT) is the cornerstone of Head and Neck (H&N) cancer treatment, but it often leads to fatigue due to irradiation of brain structures, impacting patient quality of life. OBJECTIVE: This study aimed to systematically investigate the dose correlates of fatigue after H&N RT in brain structures. METHODS: The systematic review included studies that examined the correlation between fatigue outcomes in H&N cancer patients undergoing RT at different time intervals and brain structures. PubMed, Scopus, and WOS databases were used in the systematic review. A methodological quality assessment of the included studies was conducted following the PRISMA guidelines. After RT, the cohort of H&N cancer patients was analyzed for dose correlations with brain structures and substructures, such as the posterior fossa, brainstem, cerebellum, pituitary gland, medulla, and basal ganglia. RESULT: Thirteen studies meeting the inclusion criteria were identified in the search. These studies evaluated the correlation between fatigue and RT dose following H&N RT. The RT dose ranged from 40 Gy to 70 Gy. Most of the studies indicated a correlation between the trajectory of fatigue and the dose effect, with higher levels of fatigue associated with increasing doses. Furthermore, five studies found that acute and late fatigue was associated with dose volume in specific brain structures, such as the brain stem, posterior fossa, cerebellum, pituitary gland, hippocampus, and basal ganglia. CONCLUSION: Fatigue in H&N RT patients is related to the radiation dose received in specific brain areas, particularly in the posterior fossa, brain stem, cerebellum, pituitary gland, medulla, and basal ganglia. Dose reduction in these areas may help alleviate fatigue. Monitoring fatigue in high-risk patients after radiation therapy could be beneficial, especially for those experiencing late fatigue.

Partially Lacerated Digital Flexor Tendons: A Cadaveric Study Determining the Intact Cross-sectional Area and Biomechanical Analysis.

BACKGROUND: The extent of injury in partially lacerated tendons has conventionally been expressed as a percentage of the total tendon, to justify surgical repair. We propose a more objective method to estimate the cross-sectional area of the remnant intact tendon and to determine if the remaining tendon fibers can withstand the tensile forces of early active mobilization against resistance. METHODS: The study was done on 20 cadaveric specimens, which were randomly assigned to receive a laceration of 25%, 50%, or 75% of the measured transverse tendon diameter. The circumference of the remaining intact portion of the partially lacerated tendon was measured and converted using a formula to determine the derived cross-sectional area (D-CSA). These D-CSA values were then validated by comparing them to digitally measured cross-sectional areas using a computer software program (computer-measured cross-sectional area, C-CSA). In addition, the ultimate tensile strength (UTS) of these partially lacerated tendons was analyzed to determine if a threshold exists beyond which surgical repair of a partially lacerated tendon is indicated. RESULTS: We found that the D-CSAs matched moderately with C-CSAs, with 0.622 of Pearson correlation coefficient. The UTSs of tendons with CSAs above 8 mm in circumference were consistently above 150 N. CONCLUSION: Measurement of the circumference of the partially lacerated tendon to obtain the D-CSA could be an accurate and practical method to benchmark residual tendon strength in the management of partially lacerated tendons.

Comparing the torsional resistance of different fixation techniques for spiral metacarpal fractures.

This study aimed to compare the torsional resistance of three fixation techniques for spiral metacarpal fractures: screw-only fixation, screw plus neutralization plate fixation, and a locking plate construct. A spiral fracture was created on 18 cadaveric metacarpal bones by applying an axial and torsional loading force using an Instron 3343 mechanical tester. The failure strength was defined as the native torque strength. The fractures were divided into three groups and fixed using each of the three techniques. The repaired bones were loaded to failure to determine the post-repair strength. The neutralization plate group conferred a post-repair torque (278.6 Nmm) that was similar to the native torque (292 Nmm) with a diminution of only 4.5% and appeared to provide the best resistance to torsion.

Biomechanics of surgical knot security: a systematic review.

BACKGROUND: This review aims to identify publications on quantitative biomechanical testing of surgical knot security and the physical factors that determine knot security and failure. MATERIALS AND METHODS: An electronic literature search was performed in accordance with PRISMA guidelines in January 2022 utilizing the PubMed and Google Scholar databases to look for objective biomechanical studies on knot security in surgery using the primary terms 'knot security' and 'biomechanical testing'. RESULTS: Thirty-six articles were included. Twenty-four configurations of surface, laparoscopic, and arthroscopic knots were studied. Biomechanical tensile testing was used to evaluate knot security in vitro . Load to failure (N) and elongation at knot failure (mm) were quantified by static and cyclic testing to evaluate the knot holding capacity and failure mechanism of slippage or rupture. CONCLUSION: This review reassures that the knot configuration, suture materials, suture sizes, and number of throws are key factors in determining the knot's security. Knot configuration has to be simple for laparoscopic and arthroscopic knots due to the confined space of the operating site. With the advent of stronger suture materials for high-tension surgical reconstructive procedures, there is an unmet need to understand the physical behavior of the knot and the factors that determine its resistance to slippage or rupture.Level of Evidence: Level IV.

The right turn around: Penrose tourniquet application in paediatrics.

INTRODUCTION: Commercially available tourniquets are ill-suited for paediatric patients with limb circumferences smaller than the required mechanism, forcing surgeons to improvise. This study aimed to quantify pressures exerted by the Penrose tourniquet when applied on a phantom model and evaluate the intra-/inter-rater reproducibility of the technique previously proposed. METHODS: Eight calibrated pressure sensors were distributed evenly along the inner and outer circumference of a silicon-based model. A 30cm-by-3.2 cm ARGYLE Penrose drain, 4-by-4 gauze, marker and ruler were used. The optimal interval for arterial occlusion was determined to be 70% of limb circumference. The tourniquet was secured using two half-knots formed by gauze. RESULTS: Two-turns of the tourniquet about the model generated mean pressures (SD) of 209.43 (SD:35.98 mmHg) (95%CI: 195.85-224.00 mmHg) (outer-sensor) and 246.32 (SD:61.92 mmHg) (95%CI: 221.02-273.49 mmHg) (inner-sensor). Three-turns generated mean pressures of 302.07 (SD:23.98 mmHg) (95%CI: 292.29-312.53 mmHg) (outer-sensor) and 314.44 (SD:56.70 mmHg) (95%CI: 291.25-338.25 mmHg) (inner-sensor). CONCLUSION: The Penrose tourniquet has clinical utility, particularly for patients where commercially available tourniquets are not suitable. Current application techniques generate inconsistent pressures. Using the existing model, further refinement can be done to improve the consistency and safety of the application. We recommend using intervals of slightly more than 70% of limb circumference and only two turns of the Penrose tourniquet during application. LEVEL OF EVIDENCE: V.

A fluid-structure interaction investigation of intra-articular pressure and ligament in wrist joint.

Understanding the stresses on the scapholunate interosseous ligament (SLIL) and its interaction with synovial fluid pressure could be vital to improve wrist treatment for various wrist conditions such as arthritis, sprains and tendonitis. This study investigated the interaction between the intra-articular pressure, specifically the synovial fluid pressure change and the SLIL stresses in a computational model during wrist radioulnar deviation (RUD). Magnetic resonance imaging (MRI) scans were used to acquire the anatomical model of the carpal bones and ligament, while the kinematics of scaphoid and lunate were obtained through dynamic computerized tomography (CT) scans. A two-way fluid-structure interaction (FSI) was used to model the dynamics between the scaphoid and lunate, the SLIL, and the synovial fluid. The synovial fluid pressure change was found to be small (-4.86 to 3.23 Pa) and close to that simulated in a previous work without the SLIL (-1.68 to 2.64 Pa). Furthermore, peaks of maximum fluid pressure were found to trail the peaks of ligament stress. Therefore, it is suggested that the influence of synovial fluid pressure on the ligament in the SLIL model is negligible and simulations of the scapholunate joint could forego fluid-structure interactions. Future studies can instead explore other structures in the carpus that can possibly contribute to the ligament stresses. Clinically, treatments can be targeted at these areas to help prevent or slow the progression of ligament injuries into serious consequences like the degenerative joint disease.

Biomechanical Study of Asymmetric Flexor Tendon Repair Using a 6-Strand 4-0 Supramid Suture Versus a 4-Strand 2-0 Tenoflex Suture.

Background: Multi-strand repair of flexor tendons are important for increased strength but this may cause ischemia during the intrinsic healing process. In this study, we aim to compare the strength of the 4-strand modified Asymmetric repair using 2-0 Tenoflex® suture with the original description of the Asymmetric repair using a 6-strand 4-0 Supramid® suture under cyclic loading in a porcine tendon model. We hypothesise that the number of core sutures through the repair site can be reduced with advanced suture material. Methods: Two groups consisting of 10 porcine tendons each were repaired using the Asymmetric repair technique. One group underwent the original description using a 6-strand 4-0 Supramid® suture and the other group underwent a modified 4-strand technique using 2-0 Tenoflex® suture. The repaired tendons were subjected to a two-stage cyclic loading test. Survival rate and gap formation at the repaired site were analysed. The failure mechanism of each repair was also analysed. Additionally, the cross-sectional area of each strand of core suture used was also calculated. Results: The 1st and 2nd stage survival rates were 90% and 30% for the 6-strand repair and 100% and 60% for the 4-strand repair respectively. The mean gap formation at the end of stage 2 was 1.79 mm (SD 1.57) for the 4-strand repair, which is comparable to that of the 6-strand repair (1.82 mm; [SD 1.20]). The total mean cross-sectional area of 2-0 Tenoflex® and 4-0 Supramid® suture strands were 0.078 and 0.086 mm2, respectively. Conclusions: These results demonstrate that despite having fewer core sutures, the 4-strand modified Asymmetric repair using 2-0 Tenoflex® may be a better option as compared to the original 6-strand Asymmetric repair using 4-0 Supramid®.

Biomechanical Study of Modified Massachusetts General Hospital Flexor Tendon Repair Using Looped Sutures.

Background: Massachusetts General Hospital (MGH) repair is one of the widely used 4-strand flexor tendon repair techniques. However, it uses two single strand sutures that are each passed twice across the repair site. This is time consuming and may cause imbalance of the load across the repair. We modified the MGH repair by using a looped suture and call it the looped MGH repair. The aim of this study is to compare the strength of the looped MGH repair performed with three different looped sutures against the strength of original MGH repair. Methods: Forty porcine flexors were used for the study. The original MGH repair was performed with Prolene® 4-0. Looped MGH repair was performed with three different loop sutures, Supramid® 4-0, Tendo-Loop® 4-0 and FiberLoop® 4-0. Mechanism of failure, ultimate tensile strength, stiffness, load to 2-mm gap formation and repair time were recorded for comparison. Results: There was no significant difference between the original MGH repair and the looped repair using Supramid® regarding their biomechanical performance. Looped MGH repair using Tendo-Loop® and FiberLoop® showed significantly higher ultimate tensile strength and FiberLoop® had highest 2-mm gap force. All looped MGH repairs required significant less time compared to original MGH repair. Conclusions: Our modification of the MGH repair using a looped Supramid® 4-0 suture took significantly lesser time to perform while providing the same strength as the original MGH repair using Prolene® 4-0. The use of the FiberLoop® 4-0 provided significantly greater strength while taking lesser time.

A Biomechanical Comparison of Gliding Resistance between Modified Lim Tsai and Asymmetric Tendon Repair Techniques in Zone II Flexor Tendon Repairs.

Background: Early active motion protocols have shown better functional outcomes in zone II flexor tendon lacerations. Different techniques of tendon repair have different effects on gliding resistance, which can impact tendon excursion and adhesion formation. For successful initiation of early active mobilisation, the repair technique should have high breaking strength and low gliding resistance. Previous studies have shown the Modified Lim-Tsai technique demonstrates these characteristics. The Asymmetric repair has also shown superior ultimate tensile strength. This study aims to compare the gliding resistance between the two techniques. Methods: FDP tendons from ten fresh frozen cadaveric fingers were randomly divided into two groups, transected completely distal to the sheath of the A2 pulley and repaired using either the Modified Lim-Tsai or Asymmetric technique. The core repair was performed with Supramid 4-0 looped sutures and circumferential epitendinous sutures were done with nylon monofilament Prolene 6-0 sutures. The gliding resistance and ultimate tensile strength were then tested. Results: The gliding resistance of the Asymmetric and Modified Lim-Tsai repair techniques were 0.2 and 0.95 N respectively. This difference was significant (p = 0.008). The Modified Lim-Tsai technique had a higher ultimate tensile strength and load to 2 mm gap formation, though this was not significant. Conclusions: Gliding resistance of the Asymmetric repair is significantly less than that of Modified Lim-Tsai. Ultimate tensile strength and load to 2 mm gap formation are comparable.

Biomechanical Study of Asymmetric Flexor Tendon Repair Using 3 Different Suture Materials.

Background: The asymmetric technique for flexor tendon repairs has various advantages but further improvement is possible by using a suitable suture material. In this study, we compare the biomechanical performance of asymmetric repairs using 3 suture materials: Supramid Extra II 4-0, Tendo-Loop 4-0, and FiberLoop 4-0. Methods: We divided 30 porcine flexor tendons into 3 arms. Each arm of tendons were repaired by using 1 of the 3 proposed suture materials. Each repaired tendon was tested by using a mechanical tester. Ultimate tensile strength (UTS), load to 2 mm gap force, failure mechanism and stiffness of the tendons were investigated. Results: FiberLoop® achieved the highest UTS (90.4 ± 17.9 N), followed by Tendo-Loop (85.3 ± 10.3 N). The difference was no statistically significant. The UTS of repairs using Supramid® was significantly lower (64.0 ± 8.4 N). For load to 2 mm gap force, FiberLoop® achieved 20.7 ± 4.8 N while Tendo-Loop® had 20.5 ± 4.2 N. The difference was also no statistically significant. The repairs using Supramid® had a significantly lower load to 2 mm gap force of 14.2 ± 2.7 N. The stiffness of asymmetric repairs using FiberLoop® and Tendo-Loop® was 5.64 ± 1.7 N/mm and 5.63 ± 0.7 N/mm. The difference was also no statistically significant. The repairs using Supramid® had a significantly lower stiffness of 4.15 ± 1.0 N/mm. Failure mechanisms for the repaired specimens were reported as such: Supramid had 100% suture rupture; Tendo-Loop had 90% suture rupture and 10% suture pullout; FiberLoop had 20% suture rupture and 80% suture pullout. Conclusions: The asymmetric repair configuration is able to produce superior biomechanical performance by using Tendo-Loop® or FiberLoop®. Improvement of the asymmetric technique by using Tendo-Loop® or FiberLoop® could potentially contribute to better surgical outcomes of flexor tendon repair.

Prospective observational study on Pazopanib in patients treated for advanced or metastatic renal cell carcinoma in countries in Asia Pacific, North Africa, and Middle East regions: PARACHUTE study.

BACKGROUND: Clinical effectiveness and safety data of pazopanib in patients with advanced or mRCC in real-world setting from Asia Pacific, North Africa, and Middle East countries are lacking. METHODS: PARACHUTE is a phase IV, prospective, non-interventional, observational study. Primary endpoint was the proportion of patients remaining progression free at 12 months. Secondary endpoints were ORR, PFS, safety and tolerability, and relative dose intensity (RDI). RESULTS: Overall, 190 patients with a median age of 61 years (range: 22.0-96.0) were included. Most patients were Asian (70%), clear-cell type RCC was the most common (81%), with a favourable (9%), intermediate (47%), poor (10%), and unknown (34%) MSKCC risk score. At the end of the observational period, 78 patients completed the observational period and 112 discontinued the study; 60% of patients had the starting dose at 800 mg. Median RDI was 82%, with 52% of patients receiving < 85%. Of the 145 evaluable patients, 56 (39%) remained progression free at 12 months, and the median PFS was 10 months (95% CI: 8.48-11.83). 19% of patients (21/109) were long-term responders (on pazopanib for ≥18 months). The best response per RECIST 1.1 was CR/PR in 24%, stable disease in 44%, and PD in 31%. Most frequent (> 10%) TEAEs related to pazopanib included diarrhoea (30%), palmar-plantar erythrodysesthesia syndrome (15%), and hypertension (14%). CONCLUSIONS: Results of the PARACHUTE study support the use of pazopanib in patients with advanced or mRCC who are naive to VEGF-TKI therapy. The safety profile is consistent with that previously reported by pivotal and real-world evidence studies.

Development of In-Situ Spray for Local Delivery of Antibacterial Drug for Hidradenitis Suppurativa: Investigation of Alternative Formulation.

Hidradenitis suppurativa (HS) has been considered an orphan disease with limited treatments available. The available topical treatment for this condition is clindamycin lotion; however, short retention and frequent application are the main setbacks. Thus, the present study aimed to attain an optimized antibacterial in situ spray formulation for the hidradenitis suppurativa skin condition, which gels once in contact with the skin surface at around 37 °C and possesses bioadhesion as well as sustained-release properties of the incorporated drug. Different concentrations of thermo-reversible gelling polymer, Pluronic F-127, were investigated along with the selected bioadhesive polymers, HPMC and SA. The optimized formulation F3 consisting of 18% Pluronic F-127 with 0.2% HPMC and 0.2% SA was characterized based on various physicochemical properties. The gelation temperature of F3 was found to be 29.0 ± 0.50 °C with a gelation time of 1.35 ± 0.40 min and a pH of 5.8. F3 had the viscosity of 178.50 ± 5.50 cP at 25 °C and 7800 ± 200 cP at 37 °C as the gel set. The optimized formulation was found to be bioadhesive and cytocompatible. Cumulative drug release was 65.05% within the time-frame of 8 h; the release pattern of the drug followed zero-order kinetics with the Higuchi release mechanism. The average zone of inhibition was found to be 43.44 ± 1.34 mm. The properties of F3 formulation reflect to improve residence time at the site of application and can enhance sustained drug release. Therefore, it could be concluded that optimized formulation has better retention and enhanced antimicrobial activity for superior efficacy against HS.

Intramedullary nailing confers an increased risk of medial migration compared to dynamic hip screw fixation in unstable intertrochanteric hip fractures.

INTRODUCTION: Medial migration of the femoral neck element (FNE) superomedially against gravity with respect to the intramedullary component of the cephalomedullary nail is a complication increasingly recognized to cause femoral head cut-out in intramedullary nailing of pertrochanteric hip fractures. Although cut-outs are common to both intra- and extramedullary fixation, especially in unstable pertrochanteric hip fractures, FNE medial migration in sliding hip screws continues to remain sparse despite increased awareness of the phenomenon. This study aims to investigate whether intramedullary nailing is biomechanically predisposed to FNE medial migration compared to extramedullary fixation with sliding hip screws to account for the discrepancy in reported FNE medial migration rates. MATERIALS AND METHODS: Twelve fourth-generation synthetic femurs (Sawbones) with unstable intertrochanteric fractures were divided into 2 groups (n=6 per group). Fracture fixation was performed using the Proximal Femoral Nail Antirotation (PFNA, Synthes) (n=6) in the first group, and the Dynamic Hip Screw (DHS, Synthes) (n=6) in the second group. Both groups were subjected to bidirectional cyclic loading (600N compression loading, 120N tensile loading) at 2 Hz for 5000 cycles. The medial migration distance (MMD) was recorded at the end of the testing cycles. RESULTS: The mean MMD in the PFNA group was 4.56mm (SD 0.69mm) with consistent reproduction of medial migration across all constructs tested. This was significantly more compared to the MMD of 1.17mm (SD 0.69mm) in the DHS group (p<0.001). CONCLUSION: Intramedullary nailing of unstable intertrochanteric hip fractures is inherently predisposed to FNE medial migration making it more susceptible to consequent cut-out compared to fixation with the DHS.

Evaluation of femtosecond laser-assisted anterior capsulotomy in the presence of ophthalmic viscoelastic devices (OVDs).

The introduction of femtosecond laser-assisted cataract surgery is an alternative approach to conventional cataract surgery. Our study aimed to determine the effectiveness of femtosecond laser-assisted capsulotomy in the presence of different ophthalmic viscoelastic devices (OVDs) in the anterior chamber. Fresh porcine eyes (n = 96) underwent LDV Z8-assisted anterior capsulotomy, either in the presence of an OVD (Viscoat, Provisc, Healon, Healon GV or HPMC) or without, using 90% and 150% energies respectively. Following that, the capsule circularity, tag's arc-length, tag-length, tag-area and rupture strength (mN) of the residual capsular bag were evaluated. We found that increasing energy from 90 to 150% across the OVD sub-groups improved the studied capsulotomy parameters. Amongst the 90% energy sub-groups, the circularity and tag-parameters were worse with Viscoat and Healon GV, which have higher refractive index and viscosity compared to the aqueous humour. Using 150% energy, Healon GV showed a significantly worse total arc-length (p = 0.01), total tag-length (p = 0.03) and total tag-area (p = 0.05) compared to the control group. We concluded that; an OVD with a refractive index similar to aqueous humour and lower viscosity, such as Healon or Provisc, as well as a higher energy setting, are recommended, to enhance the efficacy of laser capsulotomy.

Biomechanical comparison of vertical suture techniques for repairing radial meniscus tear.

PURPOSE: The aim of this study was to (1) develop suture techniques in repairing radial meniscal tear; (2) to compare the biomechanical properties of the proposed repair techniques with the conventional double horizontal technique. METHODS: Thirty-six fresh-frozen porcine medial menisci were randomly assigned into four groups and a complete tear was made at the midline of each meniscus. The menisci were subsequently repaired using four different repair techniques: double vertical (DV), double vertical cross (DVX), hybrid composing one vertical and one horizontal stitch, and conventional double horizontal (DH) suture technique with suturing parallel to the tibia plateau. The conventional double horizontal group was the control. The repaired menisci were subjected to cyclic loading followed by the load to failure testing. Gap formation and strength were measured, stiffness was calculated, and mode of failure was recorded. RESULTS: Group differences in gap formation were not statistically significant at 100 cycles (p = .42), 300 cycles (p = .68), and 500 cycles (p = .70). A trend was found toward higher load to failure in DVX (276.8 N, p < .001), DV (241.5 N, p < .001), and Hybrid (237.6 N, p < .001) compared with DH (148.5 N). Stiffness was also higher in DVX (60.7 N/mm, p < .001), DV (55.3 N/mm, p < .01), and Hybrid (52.1 N/mm, p < .01), than DH group (30.5 N/mm). Tissue failure was the only failure mode observed in all specimens. CONCLUSION: Our two proposed vertical suture techniques, as well as the double vertical technique, had superior biomechanical properties than the conventional technique as demonstrated by higher stiffness and higher strength.