Search Results (41)

Background and Clinical Significance: Mallet finger is a common injury of the extensor mechanism at the distal interphalangeal (DIP) joint; however, open double mallet lesions are rare and may present a complex reconstruction challenge. Case Presentation: A 15-year-old male high school student who sustained an open injury to the left ring and little fingers after a high-energy buggy accident. The ring finger showed an open double mallet lesion in which the extensor tendon remained attached to a tiny avulsion fragment, and a separate dorsal base fragment was also present. The adjacent little finger had a concomitant open fracture with substantial soft tissue injury. Emergency surgery was performed on the day of the injury. For the ring finger, reduction of the tendon-attached avulsion fragment and separate dorsal base fragment was achieved using extension-block pinning, transarticular DIP pinning, and pull-out fixation over a volar button. For the little finger, cross-pinning was performed because the distal fragment was too small for stable non-transarticular fixation. Serial radiographs showed maintained alignment and progressive healing. At the final follow-up, 21 months after the injury, residual deformity and limitation of DIP motion remained; however, no infection, major skin complications, or nail deformity were observed. The little finger DIP joint became ankylosed, whereas some residual mobility remained in the ring finger DIP joint. Despite persistent functional limitations, the patient was able to continue school attendance and percussion-related activities. Conclusions: This case highlights that in an open double mallet lesion, disruption of both the tendon-attached fragment and its bony bed should be considered, and stabilization of the base may be useful in selected injury patterns before definitive tendon-side repair. Full article

Primary hip and knee arthroplasties are common surgeries in the U.S., with periprosthetic joint infection (PJI) being the leading cause of implant revision. Systemic antibiotics often fail to achieve sufficient local concentrations, driving interest in localized drug delivery. Titanium (Ti) implants modified with titania nanotubes (TNTs) provide an increased surface area for drug loading and controlled release. Previous studies have shown that gentamicin-loaded TNTs inhibit Staphylococcus aureus growth in vitro without compromising osteoblast viability. This study investigated the effect of gentamicin–chitosan (GC)-coated TNT implants in a murine model, hypothesizing a positive impact on osseointegration. Titanium alloy (Ti6Al4V) wires were anodized to form TNTs and then coated with gentamicin–chitosan (GC) via electrophoretic deposition. Implants (Bare, TNT, TNT+GC; n = 30) were inserted bilaterally into femoral canals of C57BL/6J mice. After > 1 month, osseointegration was assessed by histological point counting, scanning electron microscopy (SEM)-based areal analysis, and mechanical pull-out testing. ANOVA was used to identify differences between groups, and linear regression was applied to account for harvest time, bone contact area, and anatomical section. Bone area fraction (BAF) around the implant measured by the SEM–areal method was significantly higher around TNT+GC (18.4% ± 1.1) and TNT (16.5% ± 1.4) versus Bare (9.0% ± 2.3) (p < 0.0028) implants. The maximum fixation strength was higher for TNT (0.878 ± 0.175 N/mm²) and TNT+GC (0.853 ± 0.215N/mm²) when compared to bare implants 0.316 ± 0.082 N/mm²) (p = 0.048 and p = 0.050, respectively). No significant differences appeared between TNT and TNT+GC. These findings indicate that GC coatings on TNT implants do not impair osseointegration and may even enhance bone–implant integration. Such coatings may therefore provide dual benefits, offering antibacterial protection while improving bone fixation, making them a promising strategy for PJI prevention. Further long-term studies are needed to confirm durability and clinical translation. Full article

Suture anchors are widely used for tendon and ligament repair, but their fixation strength is compromised in osteoporotic bone and limited bone volume such as the coracoid process. Existing designs are prone to penetration and insufficient cortical engagement under such conditions. In this study, we developed a novel short expandable-wing (SEW) suture anchor (Ti6Al4V) designed to enhance pull-out resistance through a deployable wing mechanism that locks directly against the cortical bone. Finite element analysis based on CT-derived bone material properties demonstrated reduced intra-bone displacement and improved load transfer with the SEW compared to conventional anchors. Mechanical testing using matched artificial bone surrogates (N = 3 per group) demonstrated significantly higher static pull-out strength in both normal (581 N) and osteoporotic bone (377 N) relative to controls (p < 0.05). Although the sample size was limited, results were consistent and statistically significant. After cyclic loading, SEW anchor fixation strength increased by 25–56%. In a 3D-printed anatomical coracoclavicular ligament reconstruction model, the SEW anchor provided nearly double the fixation strength of the hook plate, underscoring its superior stability under high-demand clinical conditions. This straightforward implantation protocol—requiring only a 5 mm drill hole without tapping, followed by direct insertion and knob-driven wing deployment—facilitates seamless integration into existing surgical workflows. Overall, the SEW anchor addresses key limitations of existing anchor designs in small bone volume and osteoporotic environments, demonstrating strong potential for clinical translation. Full article

This study aimed to assess, using finite element analysis (FEA), the mechanical effects of cortical bone thickness and cancellous bone density on the pull-out strength of suture anchors. A PEEK anchor was modeled and embedded in synthetic bone blocks with cortical thicknesses ranging from 1 to 5 mm and cancellous densities of 10 PCF, 20 PCF, and 30 PCF. Axial tensile loading simulations were conducted for all combinations, and selected cases were validated through experimental pull-out tests using commercial synthetic bone, demonstrating agreement within ±6%. Both cortical thickness and cancellous density were found to enhance pull-out resistance, though the magnitude and pattern varied with density. At 10 PCF, pull-out strength increased linearly with cortical thickness. At 20 PCF, substantial gains were observed between 2 and 4 mm, followed by a plateau. At 30 PCF, most of the increase was confined between 2 and 3 mm, with minimal improvement thereafter. These findings suggest that fixation strategies should be adapted on the basis of bone quality and provide biomechanical insights to inform patient-specific implant design and surgical planning. Full article

Hydroxyapatite (HA) has become a widely used material for bone grafting and surface modification of titanium-based orthopedic implants due to its excellent biocompatibility. Among various coating techniques, microplasma spraying (MPS) has gained significant industrial relevance. However, the clinical success of HA coatings also depends on their adhesion to the implant substrate. Achieving durable fixation and reliable biological integration of orthopedic implants remains a major challenge due to insufficient coating adhesion and limited osseointegration. This study addresses challenges in dental and orthopedic implantology by evaluating the microstructure, mechanical properties, and biological behavior of bilayer coatings composed of a zirconium (Zr) sublayer and an HA top layer, applied via MPS onto titanium alloy. Surface roughness, porosity, and adhesion were characterized, and pull-off and shear tests were used to assess mechanical performance. In vitro biocompatibility was tested using rat mesenchymal stem cells (MSCs) to model osteointegration. The results showed that the MPS-fabricated Zr–HA bilayer coatings achieved a pull-off strength of 28.0 ± 4.2 MPa and a shear strength of 32.3 ± 3.2 MPa, exceeding standard requirements. Biologically, the HA top layer promoted a 45% increase in MSC proliferation over three days compared to the uncoated titanium substrate. Antibacterial testing also revealed suppression of E. coli growth after 14 h. These findings support the potential of MPS-applied Zr-HA coatings to enhance both the mechanical integrity and biological performance of titanium-based orthopedic implants. Full article

Pedicle screw fixation is a common spinal surgery technique, but concerns remain about stability when screws are malpositioned. Traditional in vitro pull-out tests assess anchorage but lack physiological accuracy. This study examined the stability of correctly placed and intentionally malpositioned pedicle screws on forty vertebrae from five cadavers. Optimal screw paths were planned via CT scans and applied using 3D-printed guides. Four malposition types—medial, lateral, superior, and superior-lateral—were created by shifting the original trajectory. A custom setup applied three consecutive cycles of tensile and compressive load from 50 N to 200 N. Screw inclination under load was measured with a 3D optical system. The results showed increasing screw inclination with higher forces, reaching about 1° at 50 N and 2° at 100 N, similar in both load directions. Significant differences in inclination were only found at 100 N tensile load, where malpositioned screws showed a lower inclination. Overall, malpositioning had no major effect on screw loosening. These findings suggest that minor deviations in screw placement do not significantly compromise mechanical stability. Clinically, the main concern with malpositioning lies in the potential for injury to nearby structures rather than reduced screw fixation strength. Full article

Background/Objectives: Previous studies have reported satisfactory outcomes and low rates of instrumentation-related complications (IRCs) following nonfusion posterior fixation in patients with metastatic spinal tumors (MSTs). However, to adequately assess the longevity and durability of nonfusion instrumentation in patients with longer life expectancy, an extended follow-up period is essential. This study aims to evaluate the incidence of and risk factors for IRCs in patients with MSTs who underwent nonfusion posterior fixation and had radiographic follow-up data available for at least one year postoperatively. Methods: Consecutive data were collected from patients who underwent pedicle screw-based posterior fixation without fusion for MSTs in the thoracic and/or lumbar region from 2005 to 2018. The IRCs included screw loosening, screw pull-out, and metal breakage. The IRC-free survival and related factors were analyzed by Kaplan–Meier survivorship analysis with the log-rank test within a minimum follow-up period of one year. A multivariate analysis was performed using a Cox proportional-hazards regression model. Results: In total, 61 patients were included. The mean follow-up period was 28.3 months (range: 12.0–102.6 months). There were 27 cases (44.2%) of IRCs, including 22 cases of screw loosening, four cases of screw pull-out, and one case of rod breakage, at an average of 9.6 months (range: 1.0–38.1 months). The median IRC-free survival was 38.1 months (range: 1.0–102.6 months). Only three patients experienced pain aggravation with IRCs. No revision surgery was performed. A multivariate analysis identified that fixation length was a risk factor for IRCs (odds ratio: 0.358, 95% confidence interval: 0.114–0.888; p = 0.027). Conclusions: IRCs are frequent but mostly asymptomatic after nonfusion posterior fixation in patients with MSTs followed up for at least one year. Overall, the IRC-free survival was long enough considering the patient survival. Fixation length was a significant risk factor for IRCs regardless of MST location. Full article

This study aimed to develop a novel modular pedicle screw system incorporating an elliptical sleeve to conform the pedicle’s elliptical cross-section and enhance fixation strength with mechanical stability. The biomechanical evaluation was conducted based on fundamental mechanics principles, followed by a finite element (FE) analysis to assess stress distribution under compressive and torsional loads. Subsequently, mechanical testing was performed to evaluate static and fatigue bending performance and in vitro biomechanical fatigue in porcine vertebrae by pull-out testing after 5000 and 100,000 cycles to assess fixation stability. The FE analysis demonstrated that the elliptical sleeve design improved bending resistance by 1.21× and torsional resistance by 1.91× compared to conventional cylindrical screws. Mechanical testing revealed greater bending/torsion stiffness and fatigue resistance, with the elliptical sleeve screw withstanding 5 million cycles at 235.4 N, compared to 175.46 N for cylindrical screws. Biomechanical pull-out testing further confirmed significantly higher retention strength after 100,000 cycles (1229.75 N vs. 867.83 N, p = 0.0101), whereas cylindrical screws failed prematurely at 10,663 cycles due to excessive displacement (>2 mm). The elliptical sleeve pedicle screw system demonstrated enhanced fixation strength, reduced micromotion, and superior fatigue resistance, making it a promising alternative to conventional pedicle screws for improving long-term spinal fixation stability. Full article

Background: The management of residual elbow instability is a challenging and compelling issue for treating physicians. To overcome inherent drawbacks of dynamic external fixators, the internal joint stabilizer (IJS) has been developed, achieving successful results, but it can sometimes cause local tenderness or anesthetic concerns in the subcutaneous layer. In addition, a bulky anconeus can pull the hardware away from the axis of rotation with an increase in the lever arm and potential issues. To address these issues, an alternative approach has been recently described in which the internal device is covered by the anconeus muscle, becoming submuscular, rather than subcutaneous. The aim of this study was to evaluate the effectiveness of this alternative approach to the IJS application in maintaining a concentric elbow during and after device removal in both acute and chronic scenarios. Methods: Prospective data collection was performed with consecutive patients who had residual elbow instability treated with an IJS (Skeletal Dynamics, Miami, FL) covered by the anconeus from January 2022 and with a minimum follow-up of 12 months. Results: At a medium follow-up of 16 months, the 16 patients selected had a mean arc of flexion–extension of 123° (range: 0–140°) and a mean pronation-supination arc of 150° (range: 80–80°). The mean MEPS and DASH scores were 90.3 ± 6.2 and 6.3 ± 5.3, respectively. At the last follow-up, elbow stability and concentric reduction were confirmed with radiographic and clinical examinations. Conclusions: With a minimum follow-up of 12 months, the present study supports the safety and efficacy of the internal device in a submuscular layer. The clinical outcomes and the rate of recurrent instability are comparable to those achieved with a classic subcutaneous position. Similarly, the complication rate is not affected, and removal surgery is no more aggressive than the classic approach. Full article

Objectives: Tibial eminence fractures account for 2% to 5% of all knee injuries. Low-grade fractures, such as Type I, are typically treated conservatively, whereas high-grade fractures, such as Types III and IV, usually require surgical intervention. This paper describes a modified surgical arthroscopic technique, which employs pull-through triangle suture fixation for Type II and Type III arthroscopic intercondylar eminence avulsion fractures. In addition, we examined the efficacy and complication rate compared to the existing literature. Methods: Data were prospectively collected for knee arthroscopy surgeries and retrospectively analyzed with a minimum two-year follow-up. Twenty-three consecutive adults underwent arthroscopic treatment of displaced intercondylar Type II and Type III eminence fractures, as evidenced by clinical examination and imaging studies between May/2008 and May/2021. The patient’s knee evaluation was performed using clinical symptoms and physical examination, along with International Knee Documentation Committee (IKDC) questionnaire and Tegner Activity Score. Compared to the literature, post-hoc power was calculated based on the mean Tegner Activity Score in our analysis. Results: fifteen females and eight males (mean age 33.9 years, range 19–56 years) were enrolled. The average postoperative follow-up was 35.4 months (27–53). The post-hoc power was 95% confidence in terms of the Tegner Activity Score. The mean ± standard deviation postoperative Tegner Activity Score was 8.2 ± 1.7 (6.8–10.0). Fifteen patients were classified as IKDC A (normal), six as IKDC B (nearly normal), and two as IKDC C (abnormal). The mean IKDC subjective score was 72.7 ± 23 (23–100). Twenty-four patients achieved normal flexion degrees compared with the unaffected side, while one patient achieved a flexion of only 0–90°. The group’s mean flexion range of motion was 123 ± 16° (90–150°). Conclusion: This study presents a modified surgical arthroscopic suture fixation technique for tibial eminence fractures. The procedure is relatively simple and requires no more than basic arthroscopy equipment. The clinical and radiographic results indicate that this technique is safe, efficient, enables early initiation of rehabilitation, and has a lower complication rate in a variety of aspects compared with other fixation techniques used for tibial eminence fractures. Full article

Background: The lack of resources limits the treatment of craniomaxillofacial fractures (CMF) in low-income countries (LIC). Therefore, Barton bandages and/or interdental wiring are considered in these regions. Fracture reduction is maintained by permanent occlusion for 6 weeks, which often leads to limited compliance and dissatisfying results. The aim of this cadaver-based study is to evaluate the feasibility of the use of an external face fixator (EFF) for the treatment of CMF, its biomechanical values and to define the optimal pin insertion points and angles. Materials and Methods: An AO hand fixator was used. CMF of types Le Fort 1–3 with split fractures of the hard palate were treated with EFF on 13 anatomical specimens. Fractures were created using a chisel, and pins were placed in specific anatomical regions. The maximal pull-out force [N] of pins was analysed by a tensile force gauge, and Fmax of the mandibular pins was evaluated. Computer tomography scans were performed on the healthy, fractured and EFF-treated skulls. Results: The pull-out forces for the single pins were mandibular pins (n = 15, median 488.0 N), supraorbital pins (n = 15, median 455.0 N), zygomatic pins (n = 14, median 269.1 N), medial hard palate pins (n = 12, median 208.4 N) and lateral hard palate pins (n = 8, median 49.6 N). Conclusions: The results indicate that the operation technique is feasible, and the stability of the EFF is sufficient for maintaining the reduction. The required pins can safely be inserted into the described areas with good reduction results. Using EFF offers a feasible alternative to the non-surgical treatment of CMF in LIC. Full article

Biodegradable suture anchors based on Mg-Nd-Zn-Zr alloy were developed for ligament-to-bone fixation in rotator cuff surgeries. The Mg alloy anchors were designed with structural features of narrow tooth and wide tooth, and simulated through finite element analysis (FEA). Meanwhile, the corrosion behaviors of the Mg alloy anchors were studied by immersion test and the mechanical properties were investigated by measuring the maximum torque and pull-out force. The simulation result showed that the wide-tooth anchor exhibited more a uniform stress distribution and lower shear stress in the torsion process, suggesting a satisfactory torsional resistance of this structure. Meanwhile, the wide-tooth anchor exhibited a lower Von-Mises stress after applying the same pull-out force in the simulation, indicating a higher resistance to pull-out failure of the anchor. The result of the immersion test indicated that the wide-tooth anchor exhibited a slightly slower corrosion rate in Hank’s solution after 14-day immersion, which was beneficial to enhance the structural and mechanical stability of the biodegradable suture anchor. Furthermore, the results of the mechanical properties test demonstrated that the wide-tooth anchor showed superior performance with higher maximum torques and axial pull-out forces before and after corrosion. More importantly, the axial pull-out force and maximum torque for the wide-tooth anchor decreased by 5.86% and 8.64% after corrosion, which were significantly less than those for the narrow-tooth anchor. Therefore, the wide-tooth suture anchor with lower corrosion rate, higher mechanical properties and structural stability is a promising candidate for ligament-bone fixation in the repair of rotator cuff injuries. Full article

Torn and damaged menisci resulting from trauma are very common knee injuries, which can cause pain and mobility limitations and lead to osteoarthritis. Meniscal injuries can require surgery to repair the tissue damage and restore mobility. Here we describe the biomechanical testing of a 3D-printed meniscus to illustrate methods to determine if it has the strength and durability to effectively repair meniscal tears and restore knee biomechanics. This work was designed to demonstrate the steps needed to test novel meniscus repair devices prior to moving toward animal testing. The first testing step determined the ability of the 3D-printed meniscus to withstand surgical fixation by measuring the suture pull-out force. We show that vertical 2/0 silk or Fiberwire sutures need an average of 1.4 or 1.8 N, respectively, to pull through the meniscus, while horizontal sutures need only 0.7 and 1.2 N, respectively. The next step measured the compressive strength of normal, damaged, and repaired porcine meniscus tissue. Here, we show that meniscectomy decreased the stiffness of meniscus tissue from 26.7 ± 0.85 N to 7.43 ± 0.81 N at 25% strain. Menisci repaired with the 3D-printed tissue restored 66% of the measured force at 25% strain. The final step measured the contact pressures and areas in an ex vivo porcine knee before and after meniscal repair was made with the 3D-printed meniscus tissue. The example 3D-printed meniscus was successfully sutured into the porcine knee joint but failed to restore normal knee contact pressures. This work demonstrates the need for an iterative biomechanical testing process of biomaterial development, 3D-printing optimization, and knee kinematics to develop a durable and functional meniscus repair device. In summary, the methods described here serve as a guide for the functional evaluation of novel meniscus repair devices. Full article

The locking plate may provide improved fixation in osteoporotic bone; however, it has been reported to fail due to varus collapse or screw perforation of the articular surface, especially in osteoporotic bone with medial cortex comminution. Using bone graft as an intramedullary strut together with plate fixation may result in a stronger construct. However, the drawbacks of bone grafts include limited supply, high cost, and infection risk. PMMA (so-called bone cement) has been widely used for implant fixation due to its good mechanical properties, fabricability, and biocompatibility. The risk of donor-site infection and the drawbacks of allografting may be overcome by considering PMMA struts as alternatives to fibular grafts for humeral intramedullary grafting surgeries. However, the potential effects of intramedullary PMMA strut on the dynamic behaviour of osteoporotic humerus fractures remain unclear. This study aimed to investigate the influence of an intramedullary PMMA strut on the stability of unstable proximal humeral fractures in an osteoporotic synthetic model. Two fixation techniques, a locking plate alone (non-strut group) and the same fixation augmented with an intramedullary PMMA strut (with-strut group), were cyclically tested in 20 artificial humeral models. Axially cyclic testing was performed to 450 N for 10,000 cycles, intercyclic motion, cumulated fragment migration, and residual deformation of the constructs were determined at periodic cyclic intervals, and the groups were compared. Results showed that adding an intramedullary PMMA strut could decrease 1.6 times intercyclic motion, 2 times cumulated fracture gap migration, and 1.8 times residual deformation from non-strut fixation. During cycling, neither screw pull-out, cut-through, nor implant failure was observed in the strut-augmented group. We concluded that the plate-strut mechanism could enhance the cyclic stability of the fixation and minimize the residual displacement of the fragment in treating osteoporotic proximal humeral unstable fractures. The PMMA strut has the potential to substitute donor bone and serve as an intramedullary support when used in combination with locking plate fixation. The intramedullary support with bone cement can be considered a solution in the treatment of osteoporotic proximal humeral fractures, especially when there is medial comminution. Full article

Graft fixation during cruciate ligament reconstruction using interference screws is a common and frequently used surgical technique. These interference screws are usually made of metal or bioabsorbable materials. This paper describes the development of an allograft interference screw from cortical human bone. During the design of the screw, particular attention was paid to the choice of the screw drive and the screw shape, as well as the thread shape. Based on these parameters, a prototype was designed and manufactured. Subsequently, the first biomechanical tests using a bovine model were performed. The test procedure comprised a torsion test to determine the ultimate failure torque of the screw and the insertion torque during graft fixation, as well as a pull-out test to asses the ultimate failure load of the graft fixation. The results of the biomechanical analysis showed that the mean value of the ultimate failure torque was 2633 $\mathrm{N}$$\mathrm{m}$$\mathrm{m}$, whereas the mean occurring insertion torque during graft fixation was only 1125 $\mathrm{N}$$\mathrm{m}$$\mathrm{m}$. The mean ultimate failure load of the graft fixation was approximately 235 $\mathrm{N}$. The results of this work show a good overall performance of the allograft screw compared to conventional screws, and should serve as a starting point for further detailed investigations and studies. Full article