Fracture Gap Research Articles

Extension Block Pinning versus percutaneous Fragment Reduction with a Towel Clip and extension Block Pinning with direct Pin Fixation for Treatment of Mallet Fracture.

This study compared the clinical and radiographic results between extension block pinning (Group A) and percutaneous reduction of the dorsal fragment with a towel clip followed by extension block pinning with direct pin fixation (Group B) for the treatment of mallet fractures. A total of 69 patients (group A = 34 patients, group B = 35 patients) who underwent operative treatment for mallet fractures from June 2008 to November 2017 with ≥ 6 months post-surgical follow-up were analysed retrospectively. The extent of subluxation of the distal interphalangeal joint, articular involvement of fracture fragment, fracture gap, and articular step-off were examined on plain radiographs before and after surgery. The functional outcomes were evaluated with the Crawford rating system. The postoperative step-offs were 0.16 mm in group A and 0.01 mm in group B. Group B had a significantly better anatomical outcome than group A. Five patients in group A had a loss of reduction. Among them, two had malunion and post-traumatic arthritis. Meanwhile, no patients in group B presented with loss of reduction and nonunion. The mean extension lags were 4.2° in group A and 1.6° in group B. However, functional outcome did not differ between the two groups at the final follow-up. Fracture reduction using a towel clip and extension block pinning with direct pin insertion for mallet fracture facilitated the anatomical reduction of fragments, and allowed for stable fixation of fragments. Compared with extension block pinning technique, this technique has shown better anatomical results and stability, but not better clinical results.

Length of Plates and Number of Screws for the Fixation of Distal Humerus Fractures: A Finite Element Biomechanical Study

We performed a biomechanical analysis using the finite element method to assess the effects of plate length and the number of screws on construct stiffness, stress distribution, and fracture displacement in the fixation of type A2 distal humerus fractures. A 3-dimensional humerus model was constructed using computed tomography of a healthy man. After creating a 2-mm extra-articular fracture gap, orthogonal double-plate fixation was performed with an incremental increase in plate length and the number of screws, creating 17 fixation models. Four screws were placed in each plate's distal segment, and the number of screws was increased incrementally in the segment proximal to the fracture, starting from 2 in the medial (M) and 2 in the lateral (L) plate (M2∗L2). The fifth screw proximal to the fracture in the lateral plate (L5) played an essential role in increasing stiffness under bending, axial, and torsional forces surpassing the intact bone, which may have been due to the bypassing of the stress riser area. Minimum construct stiffness was created when 5 (M3∗L2) screws were inserted into the proximal segment. For bending forces, the M4∗L2 construct was stronger than M3∗L3 (total 6 proximal screws), and M5∗L3 was stronger than M4∗L4 (total 8 proximal screws), showing higher stiffness when the plates ended at different levels. The M4∗L2 construct (6 screws) had stiffness comparable with M4∗L3, M4∗L4, and M5∗L4 during bending, showing comparable stiffness with the least instrumentation density. Our findings suggested M3∗L5 as the optimum and M3∗L2 as the minimum construct to resist all bending, axial and torsional forces. Applying the results may improve surgical techniques, decrease the rate of complications, including fixation failure and nerve injury, and optimize the time of surgery. Moreover, hardware removal is less cumbersome with fewer screws.

Impact of Bone Cement Augmentation on the Fixation Strength of TFNA Blades and Screws.

Background and Objectives: Hip fractures constitute the most debilitating complication of osteoporosis with steadily increasing incidences in the aging population. Their intramedullary nailing can be challenging because of poor anchorage in the osteoporotic femoral head. Cement augmentation of Proximal Femoral Nail Antirotation (PFNA) blades demonstrated promising results by enhancing cut-out resistance in proximal femoral fractures. The aim of this study was to assess the impact of augmentation on the fixation strength of TFN-ADVANCEDTM Proximal Femoral Nailing System (TFNA) blades and screws within the femoral head and compare its effect when they are implanted in centre or anteroposterior off-centre position. Materials and Methods: Eight groups were formed out of 96 polyurethane low-density foam specimens simulating isolated femoral heads with poor bone quality. The specimens in each group were implanted with either non-augmented or cement-augmented TFNA blades or screws in centre or anteroposterior off-centre positions, 7 mm anterior or posterior. Mechanical testing was performed under progressively increasing cyclic loading until failure, in setup simulating an unstable pertrochanteric fracture with a lack of posteromedial support and load sharing at the fracture gap. Varus-valgus and head rotation angles were monitored. A varus collapse of 5° or 10° head rotation was defined as a clinically relevant failure. Results: Failure load (N) for specimens with augmented TFNA head elements (screw/blade centre: 3799 ± 326/3228 ± 478; screw/blade off-centre: 2680 ± 182/2591 ± 244) was significantly higher compared with respective non-augmented specimens (screw/blade centre: 1593 ± 120/1489 ± 41; screw/blade off-centre: 515 ± 73/1018 ± 48), p < 0.001. For both non-augmented and augmented specimens failure load in the centre position was significantly higher compared with the respective off-centre positions, regardless of the head element type, p < 0.001. Augmented off-centre TFNA head elements had significantly higher failure load compared with non-augmented centrally placed implants, p < 0.001. Conclusions: Cement augmentation clearly enhances the fixation stability of TFNA blades and screws. Non-augmented blades outperformed screws in the anteroposterior off-centre position. Positioning of TFNA blades in the femoral head is more forgiving than TFNA screws in terms of failure load.

Is it advantageous to use the intraoperative compression option of proximal femoral nail antirotation in the treatment of osteoporotic intertrochanteric fractures? A retrospective comparative study.

The aim of this study was to retrospectively compare the radiological and clinical results of intertrochanteric fractures treated with proximal femoral nail antirotation (PFNA) that were either intraoperatively compressed or non-compressed. Ninety-four patients (64 female, 30 male; mean age = 77.6 years; age range = 68-81) who underwent intraoperative fracture compression (IOFC) (94 hip joints, group A) and 88 patients (64 female, 24 male; mean age = 77.1 years; age range = 67- 80) who underwent postoperative impaction (POI) alone (88 hip joints, group B) from2012 to 2017 met the following six conditions were observed for over 2 years: AO Foundation/Orthopaedic Trauma Association 31-A1 and 31-A2 trochanteric fractures; Singh index grade ≥ 3; positive or neutral medial cortical support position with slightly valgus reduction; possible compression of more than one cortical bone in the anterior or medial region of the fracture site based on preoperative imaging test; blade position within the center-center; andtip-apex distance of < 25 mm. During the follow- up periods, changes of pain and time to fracture union were evaluated clinically, and the lateral extension distance (for screw back-up) was evaluated radiologically which measuredbetween the lateral end of the screw and lateral edge of the intramedullary nail. The mean follow-up was 38.4 (range = 24-48) months in Group A and 36.7 (24-48) months in Group B. The mean operation time was 68 (range = 40-100) min in group A and 71 (range = 40-105) min in Group B (P = 0.521). Intraoperative blood loss was 78 (range = 50-110) mL in Group A and 81 (range = 50-100) mL in Group B (p=0.715). The mean fluoroscopy time was 2.8 (range = 2.2-3.5) min in Group A and 2.6 (range = 2.1-3.5) min in Group B (P = 0.631). The acute phase pain scores measured by visual analog scale at postoperative 3 months were 35.5 in Group A and 37.6 in Group B (P = 0.073). The lateral extension of the PFNA blade showed significant difference at 24 months after surgery (Group A, 3.6±3.1 mm; group B, 7.8±3.7 mm, P = 0.017). Fracture gaps after surgery were 1.8 (range = 0.5-2.5)mmin Group A and 2.6 (range = 0.7-4.6)mmin Group B, showing significant difference (P = 0.001). The average fracture union time was 16.7 (range = 14-20) weeks in Group A) and 19.7 (range = 16-22) weeks in Group B (P = 0.065). The mean Harris Hip Scores at postoperative 24 months were 84.3 (range = 65-100) in Group A and 85.5 (range= 69-100) in Group B (P = 0.545).p Conclusion: If all the six conditions are met, IOFC seems to appropriate for AO/OTA 31-A1 and 31-A2 intertrochanteric fractures with the smaller postoperative fracture gap and lateral protrusion of the blade, which may contribute to the shortening of fracture union periods. Level IV, Therapeutic Study.

Tibial alignment following intramedullary nailing via three approaches.

The purpose of this study is to evaluate the incidence of malalignment in patients undergoing IMN for tibial shaft fractures treated with the extra-articular lateral parapatellar, suprapatellar, and infrapatellar approaches. A retrospective review of an institutional trauma database was completed at a single level 1 trauma academic medical centre. Quality of reduction was assessed using the following three parameters: (1) < 10°of angulation in orthogonal radiographic views (2) < 5mm of displacement between the major fracture fragments (3) < 5mm of gap between the major fracture fragments. A good reduction was one that met all 3 criteria, an acceptable reduction met 2 criteria, and a bad reduction met one or none of the criteria. All patients treated consecutively for tibial shaft fractures between June 1, 2019 and June 1, 2020 were identified. The final cohort included 57 tibia fractures in 56 patients. Of the 57 tibia fractures, 8 (14%) were proximal third, 32 (56%) were middle third, and 17 (30%) were distal third fractures. We found no significant difference in angulation, displacement, or gapping with respect to surgical approach utilized or location of fracture (proximal or distal tibia fractures) on one-way ANOVA. Quality of reduction was rated as "good" in 48 (84%) of the cases (19 supra, 13 infra, and 16 lateral). Nine reductions (16%) met only two of the three reduction quality criteria and were considered acceptable reductions. These included 2 suprapatellar (1 > 5mm displacement, 1 > 5mm gapping), 4 infrapatellar (4 > 5mm displacement), and 3 lateral extra-articular parapatellar (2 > 5mm displacement and 1 > 5mm gapping). No reductions were determined to be bad according the Baumgaertner et al. criteria. There was no significant difference in the rate of combined fibula fractures or the rate of fibular fixation between the three cohorts. In conclusion, no significant difference was found in fracture reduction angulation, displacement, and gapping in patients treated with an IMN with respect to approach for diaphyseal or metadiaphyseal tibial shaft fractures.

Immediate Weight Bearing After Fixation of Humeral Shaft Fractures with Small Fragment Hybrid Plating: A Biomechanical Analysis

Background This study evaluates the stiffness of both 4.5 mm dynamic compression plates (DCP) and 3.5 mm hybrid locking-compression plates (LCP) for treatment of humeral shaft fractures in a simulated weight bearing model. Methods Testing was performed on 16 4th generation Sawbones humeri. Initial axial and torsional stiffness were determined. Plates were placed and a 5 mm defect was produced. Specimens were subjected to 90,000 loading cycles to simulate 90 days of crutch walking and then loaded to failure. Statistical analysis was performed using a t-test with significance at P &lt; 0.05. Findings Comparison reveals a significant difference between the intact axial and torsional stiffness of 4.5 mm DCPs and 3.5 mm LCPs. The 3.5 mm plates provided 80% of the axial stiffness and 75% of the torsional stiffness of the 4.5 mm plates. The 3.5 mm plated bones failed at 79% of the mean failure load of the 4.5 mm plated bones. The 3.5 mm plated bones failed due to incidental torsion during axial loading; the 4.5 mm plated bones failed as a result of gap closure. Interpretation Our results followed expectations due to differences in plate dimensions. There were no apparent differences between constructs following cyclic loading. Our model includes a fracture gap, which requires the plate to carry the entire load. This does not simulate the actual clinical scenario wherein healing would tend to improve construct performance. While the constructs performed differently, both appear to support loads that are anticipated in the clinical setting.

Spinal alignment shift between supine and prone CT imaging occurs frequently and regardless of the anatomic region, risk factors, or pathology

Computer-assisted spine surgery based on preoperative CT imaging may be hampered by sagittal alignment shifts due to an intraoperative switch from supine to prone. In the present study, we systematically analyzed the occurrence and pattern of sagittal spinal alignment shift between corresponding preoperative (supine) and intraoperative (prone) CT imaging in patients that underwent navigated posterior instrumentation between 2014 and 2017. Sagittal alignment across the levels of instrumentation was determined according to the C2 fracture gap (C2-F) and C2 translation (C2-T) in odontoid type 2 fractures, next to the modified Cobb angle (CA), plumbline (PL), and translation (T) in subaxial pathologies. One-hundred and twenty-one patients (C1/C2: n = 17; C3-S1: n = 104) with degenerative (39/121; 32%), oncologic (35/121; 29%), traumatic (34/121; 28%), or infectious (13/121; 11%) pathologies were identified. In the subaxial spine, significant shift occurred in 104/104 (100%) cases (CA: *p = .044; T: *p = .021) compared to only 10/17 (59%) cases that exhibited shift at the C1/C2 level (C2-F: **p = .002; C2-T: *p < .016). The degree of shift was not affected by the anatomic region or pathology but significantly greater in cases with an instrumentation length > 5 segments (“∆PL > 5 segments”: 4.5 ± 1.8 mm; “∆PL ≤ 5 segments”: 2 ± 0.6 mm; *p = .013) or in revision surgery with pre-existing instrumentation (“∆PL presence”: 5 ± 2.6 mm; “∆PL absence”: 2.4 ± 0.7 mm; **p = .007). Interestingly, typical morphological instability risk factors did not influence the degree of shift. In conclusion, intraoperative spinal alignment shift due to a change in patient position should be considered as a cause for inaccuracy during computer-assisted spine surgery and when correcting spinal alignment according to parameters that were planned in other patient positions.

Mini-Open Reduction and Extension Block Pinning for Irreducible Mallet Fractures: A Minimally Invasive Technique for Anatomical Reduction.

Background: Dorsal rotation or persistent displacement of the fracture fragment is frequently encountered in extension block pinning for mallet fractures. We reviewed nine irreducible mallet fracture patients treated with mini-open reduction and extension block pinning. Methods: A small V-shaped incision was made on the fracture gap when there was persistent displacement of fracture fragment despite closed maneuvers and percutaneous procedures while performing extension block pinning. Soft tissue or granulation tissue hampering reduction was removed through the incision. Anatomical reduction was guided with a freer elevator. The incision was closed by distal interphalangeal joint transfixation in extension without any suture. Pin tips were buried under the skin. The incision and pin entry sites were covered with skin adhesive, and the patients were allowed to wash their hands 1-2 days after the surgery. No splint was applied postoperatively. Mean follow-up period was 13 months. Results: Anatomical reduction was achieved in 7 out of 9 patients. In the rest 2 patients, postoperative step-off of the articular surface at the fracture site was less than 0.5 mm. Solid union was achieved in all cases. The mean extension lag at final follow-up was 0°. No patient developed postoperative external bleeding or other complications in the incision site or the pin site. Conclusions: Mini-open reduction and extension block pinning appears to be a good option for irreducible mallet fractures, which improves reduction quality and patients' convenience.

Virtual Simulation for Interactive Visualization of 3D Fracture Fixation Biomechanics.

In the surgical fixation of fractures, proper biomechanical stability is key in preventing clinical complications including poor fracture healing, residual deformity, loss of fixation, or implant failure. Stability is largely influenced by treatment decisions made by the surgeon. The interplay of surgeon-controlled variables and their effect on the three-dimensional (3D) biomechanics of a fracture fixation construct are often not intuitive, and current training methods do not facilitate a deep understanding of these interactions. A simulation software interface, FracSim, was developed. FracSim is built on a large precomputed library of finite element simulations. The software allows a surgeon to make adjustments to a virtual fracture fixation construct/weight-bearing plan and immediately visualize how these changes affect 3D biomechanics, including implant stress and fracture gap strain, important for clinical success. Twenty-one orthopaedic residents completed an instructor-led educational session with FracSim focused on bridge plating. Subjects completed pretests and posttests of knowledge of biomechanical concepts and a questionnaire. Subjects scored a mean of 5.6/10 on the pretest of biomechanical knowledge. Senior residents scored better than junior residents (P = 0.04). After the educational session with FracSim, residents improved their test scores to a mean of 8.0/10, with a significant improvement (P < 0.001). Questionnaire scores indicated that subjects believed that FracSim had realistic implants, constructs, and motions and that training with FracSim was purposeful, desirable, efficient, fun, and useful for enhancing the understanding of fracture fixation biomechanics. This new type of simulation software enables interactive visualization of 3D fracture fixation biomechanics. Limitations of this study include lack of a control group undergoing traditional education and lack of a delayed posttest to assess retention. FracSim may provide an effective and engaging way to promote a deeper understanding of biomechanical concepts in the orthopaedic learner.

EGFL6 regulates angiogenesis and osteogenesis in distraction osteogenesis via Wnt/\u03b2-catenin signaling

BackgroundOsteogenesis is tightly coupled with angiogenesis during bone repair and regeneration. However, the underlying mechanisms linking these processes remain largely undefined. The present study aimed to test the hypothesis that epidermal growth factor-like domain-containing protein 6 (EGFL6), an angiogenic factor, also functions in bone marrow mesenchymal stem cells (BMSCs), playing a key role in the interaction between osteogenesis and angiogenesis.MethodsWe evaluated how EGFL6 affects angiogenic activity of human umbilical cord vein endothelial cells (HUVECs) via proliferation, transwell migration, wound healing, and tube-formation assays. Alkaline phosphatase (ALP) and Alizarin Red S (AR-S) were used to assay the osteogenic potential of BMSCs. qRT-PCR, western blotting, and immunocytochemistry were used to evaluate angio- and osteo-specific markers and pathway-related genes and proteins. In order to determine how EGFL6 affects angiogenesis and osteogenesis in vivo, EGFL6 was injected into fracture gaps in a rat tibia distraction osteogenesis (DO) model. Radiography, histology, and histomorphometry were used to quantitatively evaluate angiogenesis and osteogenesis.ResultsEGFL6 stimulated both angiogenesis and osteogenic differentiation through Wnt/β-catenin signaling in vitro. Administration of EGFL6 in the rat DO model promoted CD31hiEMCNhi type H-positive capillary formation associated with enhanced bone formation. Type H vessels were the referred subtype involved during DO stimulated by EGFL6.ConclusionEGFL6 enhanced the osteogenic differentiation potential of BMSCs and accelerated bone regeneration by stimulating angiogenesis. Thus, increasing EGFL6 secretion appeared to underpin the therapeutic benefit by promoting angiogenesis-coupled bone formation. These results imply that boosting local concentrations of EGFL6 may represent a new strategy for the treatment of compromised fracture healing and bone defect restoration.

No more rattling: biomechanical evaluation of a hexapod ring fixator free of play.

Hexapod-ring-fixators have a characteristic rattling sound during load changes due to play in the hexapod struts. This play is perceived as unpleasant by patients and can lead to frame instability. Using slotted-ball-instead of universal-joints for the ring-strut connection could potentially resolve this problem. The purpose of the study was to clarify if the use of slotted-ball-joints reduces play and also fracture gap movement. A hexapod-fixator with slotted-ball-joints and aluminum struts (Ball-Al) was compared touniversal-joint-fixators with either aluminum (Uni Al) orsteel struts (Uni Steel). Six fixator frames each were loaded in tension, compression, torsion, bending and shear andmechanical performance was analyzed in terms of movement, stiffness and play. The slotted-ball-joint fixator wasthe only system without measurable axial play(<0.01mm) compared to Uni-Al (1.2±0.1)mm and Uni-Steel (0.6±0.2)mm (p≤0.001). In both shear directions the Uni-Al had the largest play (p≤0.014). The resulting axial fracture gap movements were similar for the two aluminum frames and up to 25% smaller for the steel frame, mainly due to the highest stiffness found for the Uni-Steel in allloading scenarios (p≤0.036). However, the Uni-Steel construct was also up to 29% (450g) heavier and had fewer usable mounting holes. In conclusion, the slotted-ball-joints of the Ball-Al fixator reduced play and minimized shear movement in the fracture while maintaining low weight of the construct. The heavier and stiffer Uni-Steel fixator compensates for existing play with a higher overall stiffness.

Retrospective comparison of conservative treatment and surgery for widely displaced olecranon fractures in low-demanding geriatric patients

IntroductionThe aim of this study was to evaluate the difference of the clinical outcome of elderly patients who were treated surgically or conservatively for a displaced olecranon fracture (Mayo type IIA or IIB).Patients and methodsPatients above the age of 70 years who were treated surgically (n = 11) for a displaced Mayo type IIA and IIB olecranon fracture between July 2015 and February 2019 were retrospectively compared with patients who were treated conservatively (n = 6). The range of motion, elbow strength, grip strength, VAS, DASH, OES, MEPI and Broberg and Morrey scores were evaluated.ResultsThe conservative group showed a non-union with a persistent fracture gap of 17 mm (SD 12 mm) at the articular rim and 31 mm (15 mm) at the dorsal rim while there was no case of non-union in the surgical group. The arch of motion was 120° in the conservative group and 136° in the surgical group. There was no obvious difference in elbow extension strength in comparison to the healthy contralateral side (p = 0.20; 88% group I/87% group II). There was no difference in the OES (p = 0.30; 42 (SD 7) vs. 45 (SD 5)) and MEPI score (p = 0.46; (SD 8) vs. 96 (SD 19)). The conservative group presented a slightly worse DASH [p = 0.10; 26 (SD 25) vs 7 (SD 14)] and a significantly worse Broberg and Morrey score (p = 0.02; 84(SD 9) vs. 95 (SD 7)). The conservative group presented one complication (ulnar nerve palsy), while the surgical group presented two cases (prolonged lymphedema; blocked forearm rotation due to screw length with consecutive revision surgery).ConclusionWidely displaced olecranon fractures can successfully be treated conservatively in low-demanding geriatric patients with a satisfactory outcome. Patient selection is essential as patients that are more active might benefit from surgical treatment. Yet, treatment risks and benefits need to be balanced carefully in regard to the patient`s demands and requests.

Biomechanical study of transsacral-transiliac screw fixation versus lumbopelvic fixation and bilateral triangular fixation for \u201cH\u201d- and \u201cU\u201d-type sacrum fractures with traumatic spondylopelvic dissociation: a finite element analysis study

ObjectiveTo compare the biomechanical stability of transsacral-transiliac screw fixation and lumbopelvic fixation for “H”- and “U”-type sacrum fractures with traumatic spondylopelvic dissociation.MethodsFinite element models of “H”- and “U”-type sacrum fractures with traumatic spondylopelvic dissociation were created in this study. The models mimicked the standing position of a human. Fixation with transsacral-transiliac screw fixation, lumbopelvic fixation, and bilateral triangular fixation were simulated. Biomechanical tests of instability were performed, and the fracture gap displacement, anteflexion, rotation, and stress distribution after fixation were assessed.ResultsFor H-type fractures, the three kinds of fixation ranked by stability were bilateral triangular fixation > lumbopelvic fixation > transsacral-transiliac screw fixation in the vertical and anteflexion directions, bilateral triangular fixation > transsacral-transiliac S1 and S2 screw fixation > lumbopelvic fixation in rotation. The largest displacements in the vertical, anteflexion, and rotational directions were 0.57234 mm, 0.37923 mm, and 0.13076 mm, respectively. For U-type fractures, these kinds of fixation ranked by stability were bilateral triangular fixation > lumbopelvic fixation > transsacral-transiliac S1 and S2 screw fixation > transsacral-transiliac S1 screw fixation in the vertical, anteflexion, and rotational directions. The largest displacements in the vertical, anteflexion, and rotational directions were 0.38296 mm, 0.33976 mm, and 0.05064 mm, respectively.ConclusionAll these kinds of fixation met the mechanical criteria for clinical applications. The biomechanical analysis showed better bilateral balance with transsacral-transiliac screw fixation. The maximal displacement for these types of fixation was less than 1 mm. Percutaneous transsacral-transiliac screw fixation can be considered the best option among these kinds of fracture fixation.

Biomechanics of subtrochanteric fracture fixation using short cephalomedullary nails: A finite element analysis

A finite element analysis was performed to evaluate the stresses around nails and cortical bones in subtrochanteric (ST) fracture models fixed using short cephalomedullary nails (CMNs). A total 96 finite element models (FEMs) were simulated on a transverse ST fracture at eight levels with three different fracture gaps and two different distal locking screw configurations in both normal and osteoporotic bone. All FEMs were fixed using CMNs 200 mm in length. Two distal locking screws showed a wider safe range than 1 distal screw in both normal and osteoporotic bone at fracture gaps ≤ 3 mm. In normal bone FEMs fixed even with two distal locking screws, peak von Mises stresses (PVMSs) in cortical bone and nail constructs reached or exceeded 90% of the yield strength at fracture levels 50 mm and 0 and 50 mm, respectively, at all fracture gaps. In osteoporotic bone FEMs, PVMSs in cortical bone and nail constructs reached or exceeded 90% of the yield strength at fracture levels 50 mm and 0 and 50 mm, respectively, at a 1-mm fracture gap. However, at fracture gaps ≥ 2 mm, PVMSs in cortical bone reached or exceeded 90% of the yield strength at fracture levels ≥ 35 mm. PVMSs in nail showed the same results as 1-mm fracture gaps. PVMSs increased and safe range reduced, as the fracture gap increased. Short CMNs (200 mm in length) with two distal screws may be considered suitable for the fixation of ST transverse fractures at fracture levels 10 to 40 mm below the lesser trochanter in normal bone and 10 to 30 mm in osteoporotic bone, respectively, under the assumptions of anatomical reduction at fracture gap ≤ 3 mm. However, the fracture gap should be shortened to the minimum to reduce the risk of refracture and fixation failure, especially in osteoporotic fractures.

Can Optimizing the Mechanical Environment Deliver a Clinically Significant Reduction in Fracture Healing Time?

The impact of the local mechanical environment in the fracture gap on the bone healing process has been extensively investigated. Whilst it is widely accepted that mechanical stimulation is integral to callus formation and secondary bone healing, treatment strategies that aim to harness that potential are rare. In fact, the current clinical practice with an initially partial or non-weight-bearing approach appears to contradict the findings from animal experiments that early mechanical stimulation is critical. Therefore, we posed the question as to whether optimizing the mechanical environment over the course of healing can deliver a clinically significant reduction in fracture healing time. In reviewing the evidence from pre-clinical studies that investigate the influence of mechanics on bone healing, we formulate a hypothesis for the stimulation protocol which has the potential to shorten healing time. The protocol involves confining stimulation predominantly to the proliferative phase of healing and including adequate rest periods between applications of stimulation.

Time-dependent in silico modelling of orthognathic surgery to support the design of biodegradable bone plates

Orthognathic surgery is performed to realign the jaws of a patient through several osteotomies. The state-of-the-art bone plates used to maintain the bone fragments in place are made of titanium. The presence of these non-degradable plates can have unwanted side effects on the long term (e.g. higher infection risk) if they are not removed. Using a biodegradable material such as magnesium may be a possible solution to this problem. However, biodegradation leads to a decrease of mechanical strength, therefore a time-dependent computational approach can help to evaluate the performance of such plates. In the present work, a computational framework has been developed to include biodegradation and bone healing algorithms in a finite element model. It includes bone plates and the mandible, which are submitted to masticatory loads during the early healing period (two months following the surgery). Two different bone plate designs with different stiffnesses have been tested. The stiff design exhibited good mechanical stability, with maximum Von Mises stress being less than 40% of the yield strength throughout the simulation. The flexible design shows high stresses when the bone healing has not started in the fracture gaps, indicating possible failure of the plate. However, this design leads to a higher bone healing quality after two months, as more cartilage is formed due to higher strains exerted in fracture gaps. We therefore conclude that in silico modelling can support tuning of the design parameters to ensure mechanical stability and while promoting bone healing.

The effect of pearl spacing on single-cycle load-to-failure and cyclic loading parameters of 2.0 mm pearl locking plates

ABSTRACT Aims To compare the mechanical performance and mode of failure in four-point bending of two different 2.0 mm “string of pearls” locking plates that differ in dimensions. Methods Ten *2.0 mm, 82 mm long, 10-hole (Plate A) and ten 2.0 mm, 69 mm long, 12-hole (Plate B) Cortical Pearl Systems were secured to plate extenders and centred beneath an Instron tensile tester in four-point bending. In all constructs, a simulated fracture gap was maintained at 33 mm. Due to differences in plate dimensions, 33 mm corresponded to four pearls (Plate A) and six pearls (Plate B). Following an initial preload of 10 N, ramped single-cycle load-to-failure at 0.1 mm/second was performed in five Plate A and five Plate B constructs. Load and displacement were recorded. Constant frequency sinusoidal cyclic loading (33 N) at 20 mm/minute was performed on five Plate A and five Plate B constructs following 10 N of preload. Maximum moment and cycle count were recorded. Testing and data analysis were completed in accordance with the American Society for Testing and Materials F382-14 guidelines. Differences in performance and mode of failure were compared. Results : Plate A constructs produced higher mean values for bending stiffness (19.8 (SD 2.0) N/mm vs. 10.1 (SD 0.6) N/mm; p < 0.001), bending structural stiffness (0.77 (SD 0.08) Nm2 vs. 0.39 (SD 0.02) Nm2; p < 0.001), yield point (64.1 (SD 4.2) N vs. 54.6 (SD 3.9) N; p = 0.01), proof load (65.4 (SD 3.2) N vs. 55.6 (SD 4.0) N; p = 0.005), and bending strength (1.3 (SD 0.1) Nm vs. 1.1 (SD 0.08) Nm; p = 0.005) when compared to Plate B constructs in single cycle load-to-failure. Plate A constructs had a greater (p = 0.001) mean cycle count to failure (26,178 (SD 4,061) cycles) when compared with Plate B constructs (15,550 (SD 1,291) cycles). All plates failed by non-catastrophic plastic deformation. Conclusions Plate A, which is wider, thicker and has a greater spacing between pearls, was mechanically superior to Plate B in four-point bending under single-cycle load-to-failure and sinusoidal cyclic loading. Clinical relevance Although mechanical differences were identified in four-point bending, in vivo biomechanical performance remains undetermined. By selecting Plate B, the clinician may gain bone purchase through a greater number of pearls and thus screws per unit length, however, the inferior mechanical characteristics, as evaluated in four-point bending, should also be considered. Further research into the mechanical and biomechanical performance of these plating systems is warranted.

Influence of Timing on Surgical Outcomes for Acute Humeral Shaft Fractures.

Surgical treatment for humeral shaft fractures has been reported to yield satisfactory results; however, there may be complications, such as delayed bone union, nonunion, iatrogenic radial nerve injury, and infection. The risk factors for postoperative complications remain largely unknown. This study aimed to investigate the influence of timing of surgery on the incidence of postoperative complications of acute humeral shaft fractures. We retrospectively reviewed 43 patients who underwent osteosynthesis for acute humeral shaft fractures between 2006 and 2020. The patients were divided into early (21 patients) and delayed (22 patients) treatment groups based on the timing of the surgical intervention (within or after four days). Outcomes were the incidences of complications (delayed union, nonunion, iatrogenic radial nerve injury, and infection) and postoperative fracture gaps. We evaluated the outcomes using plain radiographs and clinical notes. In addition, we performed subgroup analyses on outcomes in a subgroup of patients who underwent intramedullary nailing and one who underwent plate fixation. The frequency of delayed union was significantly higher in the delayed group (P=0.046), and the postoperative fracture gap size was also significantly greater in the delayed group (P=0.007). The subgroup analyses demonstrated a significant association between the increased incidence of delayed union and delayed surgical interventions only in the intramedullary nailing subgroup (P=0.017). This study suggests that performing surgery within four days after acute humeral shaft fracture is recommended to reduce the occurrence of delayed union, particularly in cases requiring intramedullary nailing fixation.

Mandibular Fractures: Pre-Operative Panoramic Radiography and Duplication Sign Patterns

The purpose of this essay is to present the multiple patterns of the duplication sign at the mandibular fracture line/gap visualized at the panoramic radiography as two-line fracture gap or pseudocomminuted fracture. We retrospectively reviewed the orthopantomography of patients with mandible fractures and presented nine patients with 12 duplication signs (also known as lambda course fracture line). On panoramic radiographs the fracture line/gap with duplication sign is visualized as two-line cortical bone discontinuity with or without dislocation due to the fact that the fracture gap runs asymmetrically on the external and internal cortical plates of the jaw. Knowledge of duplication sign patterns, artifacts is also crucial for the precise diagnosis and choice of correct management strategy.

Optimal time-dependent levels of weight-bearing for bone fracture healing under Ilizarov circular fixators

It is known that weight-bearing exercises under Ilizarov circular fixators (ICF) could enhance bone fracture healing by mechano-regulation. However, interfragmentary movements at the fracture site induced by weight-bearing may inhibit angiogenesis and ultimately delay the healing process. To tackle this challenge, a computational model is presented in this study which considers the spatial and temporal changes in mechanical properties of fracture callus to predict optimal levels of weight-bearing during fracture healing under ICF. The study takes sheep fractures as example and shows that the developed model has the capability of predicting patient specific, time-dependent optimal levels of weight-bearing which enhances mechano-regulation mediated healing without hindering the angiogenesis process. The results demonstrate that allowable level of weight-bearing and timings depend on fracture gap size. For normal body weights (BW) and moderate fracture gap sizes (e.g. 3 mm), weight-bearing with 30% BW could start by week 4 post-operation and gradually increase to 100% BW by week 11. In contrast, for relatively large fracture gap sizes (i.e. 6 mm), weight-bearing is recommended to commence in later stages of healing (e.g. week 11 post-operation). Furthermore, increasing ICF stiffness (e.g. using half pins instead of pretension wires) can increase the level of weight-bearing significantly in the early stages up to a certain time point (e.g. week 8 post-operation) beyond which no noticeable benefits could be achieved. The findings of this study have potential applications in designing post-operative weight bearing exercises.