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

Non-screw glenoid augmentation constructs for shoulder instability with bone loss: A biomechanical assessment of static and elastic cerclage constructs

Purpose

This study aims to compare the biomechanical performance of elastic and static suture-based cerclage systems to traditional screw constructs in the setting of modeled glenoid bony augmentation.

Methods

Biomechanical testing was conducted on polyurethane cellular foam blocks modeling a 20 % glenoid defect repaired with a coracoid graft. Constructs consisted of an elastic suture-based cerclage, static suture-based cerclage, and a two-screw construct. Biomechanical testing was performed on material testing system, using a 7-phase, 100 cycle per phase, 1Hz, sinusoidal cyclic loading protocol, following a stair-step pattern in load control. Failure for cyclic loading was assessed at 0.8 mm linear displacement. The absolute end level for load-to-failure was 7.0 mm.

Results

Static suture-based cerclage failed at 5-50 N (Cycles 2 through 4), 2-screw constructs failed at 25-50 N (Cycle 4), and elastic suture-based cerclage failed at 100-200N (Cycles 6 and 7). Elastic cerclage exhibited superior performance compared to static cerclage beginning in Cycle 2 (p = 0.0440) and compared to SOC 2-screw construct beginning in Cycle 4 (p = 0.0118). 2-screw construct exhibited superior stability performance compared to static cerclage beginning in Cycle 3 (p = 0.0001). Elastic cerclage reached failure at 558.141 ± 4.508 N, while 2-screw construct and static cerclage reached failure at 422.009 ± 24.998 N and 366.770 ± 66.653 N, respectively. Elastic cerclage demonstrated superior biomechanical stability in load-at-failure performance to static cerclage (p < 0.0001) and the screw construct (p < 0.0001), while static cerclage demonstrated inferior biomechanical stability to the screw construct (p = 0.0343).

Conclusion

This biomechanical study comparing the performance of elastic cable and static suture tape cerclage fixation methods identified that the elastic cable cerclage exhibits a higher load-at-failure and less displacement under repetitive stress. In addition, elastic cable cerclage fixation exhibits greater strength and construct rigidity than traditional metal screw fixation.

The Type of Lateral Hinge Fracture in Medial Open-Wedge High Tibial Osteotomy Determines Its Stability: A Biomechanical Study

BACKGROUND

Lateral hinge fractures (LHFs) are considered risk factors for delayed union or nonunion after medial open-wedge high tibial osteotomies (MOWHTOs). However, there is limited evidence on the extent to which the morphology of the hinge fracture influences the stability of a MOWHTO.

PURPOSE/HYPOTHESIS

The purpose of this study was to validate the Takeuchi classification under axial and torsional loading to identify the LHF types requiring surgical treatment. It was hypothesized that (1) LHFs would reduce construct stiffness and increase interfragmentary instability across the osteotomy gap, and (2) shear displacement associated with impaired bone healing of >2 mm would be observed in Takeuchi type 2 and 3 fractures.

STUDY DESIGN

Descriptive laboratory study.

METHODS

A total of 24 fresh-frozen human cadaveric proximal tibiae underwent MOWHTO fixed with a locking compression plate. The specimens were assigned to 3 different groups so that the mean bone mineral density values were similar between the groups. Each group simulated a different type of LHF according to the Takeuchi classification: (1) type 1 fracture, extension along the osteotomy plane; (2) type 2 fracture, extension distal to the proximal tibiofibular joint; and (3) type 3 fracture, proximal extension into the lateral tibial plateau. Each specimen was subjected to 10 quasi-static cycles of axial compression up to 720 N, followed by internal and external torsional loading up to 10 N·m, while the interfragmentary movements were captured with a motion tracking system.

RESULTS

Compared with a MOWHTO with a preserved lateral hinge, Takeuchi type 2 and 3 fractures significantly increased shear displacement and hinge rotation by 2.2 mm and 2.3°, respectively, resulting in at least 80% reduction in torsional stiffness (P < .001). In contrast, Takeuchi type 1 fractures did not significantly alter the torsional stability of a MOWHTO. Takeuchi type 2 and 3 fractures significantly increased axial displacement at the hinge site by 0.2 mm (P < .01) compared with an intact hinge MOWHTO, while axial displacement of the medial osteotomy gap remained unchanged. All Takeuchi types significantly reduced axial construct stiffness by at least 28% (P < .01).

CONCLUSION

From a biomechanical perspective, Takeuchi type 1 LHFs did not affect the torsional stability of MOWHTO, whereas Takeuchi type 2 and 3 fractures resulted in significantly reduced torsional stiffness, increased shear displacement, and hinge rotation across the osteotomy gap. All Takeuchi fracture types resulted in reduced axial construct stiffness, while axial displacement was not significantly affected by the type of hinge fracture.

CLINICAL RELEVANCE

The observed shear displacement of >2 mm for Takeuchi type 2 and 3 fractures may be indicative of impaired bone healing and may therefore qualify these fractures for hinge fixation to potentially reduce the risk of delayed union and nonunion.

Fixation of Takeuchi Type II/III lateral hinge fractures provides favourable stability of a medial open wedge high tibial osteotomy-A biomechanical study

PURPOSE

To investigate the biomechanical consequences of osteosynthesis of lateral hinge fractures (LHFs) in medial open wedge high tibial osteotomy (MOWHTO).

METHODS

Sixteen fresh-frozen human cadaveric proximal tibiae underwent MOWHTO fixed with an ipsilateral locking compression plate. The specimens were assigned to two clusters simulating LHFs according to the Takeuchi classification: (1) Type II fracture; and (2) Type III fracture. The following conditions were serially tested: (1) intact hinge; (2) fractured hinge; (3) screw fixation of the LHF; (4) staple fixation of the LHF; and (5) locking T-plate fixation of the LHF. Each specimen was subjected to 10 cycles of axial compression load (720 N; 36 N/s), and internal and external rotational loads (10 N m; 1 N m/s), while capturing the interfragmentary movements via motion tracking.

RESULTS

In Takeuchi Type II fractures, osteosynthesis of the fractured hinge with staples or a plate significantly reduced fracture site displacement (p < 0.05) and significantly increased construct stiffness (p < 0.05) under axial and torsional loading, while only the plate restored intact torsional displacement (n.s.). For Takeuchi Type III fractures, both screw and plate fixation significantly reduced fracture site displacement (p < 0.05) and significantly increased construct stiffness (p < 0.05) under axial and torsional loading. Both techniques restored torsional stiffness in each rotational direction and torsional displacement in internal rotation (n.s.).

CONCLUSION

Additional plate fixation of Takeuchi Type II fractures was the construct with the highest stiffness, restoring the axial and torsional stability to a MOWHTO with an intact hinge. Screw and plate fixation of Takeuchi Type III fractures provided equivalent stability and restored the torsional and axial stability of the MOWHTO. In case of a Takeuchi Type II or III fracture, surgeons should consider additional plate or screw osteosynthesis of the fractured hinge to best restore the stability of the MOWHTO, which may potentially reduce the risk of loss of correction and impaired bone healing.

LEVEL OF EVIDENCE

There is no level of evidence as this study was an experimental laboratory study.

A novel external fixation for treating tibial fractures: a finite element and biomechanical study

OBJECTIVE

Design a new type of external fixation device that is small in size, high in strength, and capable of achieving the mechanical requirements for fracture healing. Verify the rationality and effectiveness of the device in treating tibial fractures through finite element analysis and biomechanical comparative tests.

METHODS

Finite element simulation was performed on the new external fixation device to treat fractures, to verify whether the mechanical properties of the device meet the requirements of fracture healing. A fracture gap model was created using Sawbones to simulate midshaft tibial comminuted fractures. The experiment was divided into four groups, testing the mechanical characteristics of the new external fixation (NEF), locking compression plate (LCP), the unilateral external fixation (UEF), and the externalized locking compression plate (E-LCP). The axial compression, torsion, fatigue and ultimate load tests were performed separately. Data were collected and statistical analysis was performed to verify whether there were statistical differences between the four groups.

RESULTS

The finite element analysis of NEF demonstrated that the fracture end was displaced by 0.512 mm under 700 N loading, and the maximum stress value of the device was 189 MPa, which met the mechanical requirements. Axial compression tests showed that LCP (2108.596 N/mm) had the highest stiffness, and NEF (519.489 N/mm) had higher stiffness than both UEF (327.153 N/mm) and E-LCP (316.763 N/mm) (p < 0.05), but no significant difference between UEF and E-LCP (p = 0.313). There was a significant difference in mean torsional stiffness among UEF (1.412 N·m/deg), NEF (1.398 N·m/deg), LCP (1.128 N·m/deg), and E-LCP (0.838 N·m/deg). No structural failures occurred during fatigue testing spanning 108,000 cycles. In ultimate load tests, NEF withstood the highest load, followed sequentially by LCP, UEF, and E-LCP. Significant differences were found between the groups (p < 0.05), with frame bending and secondary bone fractures noted in post-test evaluations.

CONCLUSIONS

The NEF for tibial fractures is well-designed to meet the fracture healing requirements. It has certain advantages in comparison with other fixation methods and can be used as a new method for the treatment of tibial fractures.

Volumetric Humeral Canal Fill Ratio Effects Primary Stability and Cortical Bone Loading in Short and Standard Stem Reverse Shoulder Arthroplasty: A Biomechanical and Computational Study

OBJECTIVE

This study evaluated the effect of three-dimensional (3D) volumetric humeral canal fill ratios (VFR) of reverse shoulder arthroplasty (RSA) short and standard stems on biomechanical stability and bone deformations in the proximal humerus.

METHODS

Forty cadaveric shoulder specimens were analyzed in a clinical computed tomography (CT) scanner allowing for segmentation of the humeral canal to calculate volumetric measures which were verified postoperatively with plain radiographs. Virtual implant positioning allowed for group assignment (VFR < 0.72): Standard stem with low (n = 10) and high (n = 10) filling ratios, a short stem with low (n = 10) and high filling ratios (n = 10). Biomechanical testing included cyclic loading of the native bone and the implanted humeral component. Optical recording allowed for spatial implant tracking and the quantification of cortical bone deformations in the proximal humerus.

RESULTS

Planned filling ratios based on 3D volumetric measures had a good-to-excellent correlation (ICC = 0.835; p < 0.001) with implanted filling ratios. Lower canal fill ratios resulted in significantly higher variability between short and standard stems regarding implant tilt (820 N: p = 0.030) and subsidence (220 N: p = 0.046, 520 N: p = 0.007 and 820 N: p = 0.005). Higher filling ratios resulted in significantly lower bone deformations in the medial calcar area compared to the native bone, while the bone deformations in lower filling ratios did not differ significantly (p > 0.177).

CONCLUSIONS

Lower canal filling ratios maintain dynamic bone loading in the medial calcar of the humerus similar to the native situation in this biomechanical loading setup. Short stems implanted with a low filling ratio have an increased risk for implant tilt and subsidence compared to high filling ratios or standard stems.

Early resistance rehabilitation improves functional regeneration following segmental bone defect injury

Many studies have explored different loading and rehabilitation strategies, yet rehabilitation intensity and its impact on the local strain environment and bone healing have largely not been investigated. This study combined implantable strain sensors and subject-specific finite element models in a 2 mm rodent segmental bone defect model. After injury animals were underwent high or low intensity rehabilitation. High intensity rehabilitation increased local strains within the regenerative niche by an average of 44% compared to the low intensity rehabilitation. Finite element modeling demonstrated that resistance rehabilitation significantly increased compressive strain by a factor of 2.0 at week 2 and 4.45 after 4 weeks of rehabilitation. Animals that underwent resistance running had the greatest bone volume and improved functional recovery with regenerated femurs that matched intact failure torque and torsional stiffness values. These results demonstrate the potential for early resistance rehabilitation to improve bone healing.

Finite element analysis of distraction osteogenesis with a new extramedullary internal distractor

Distraction osteogenesis (DO) is a bone regenerative maneuver, which is conventionally done with external fixators and, more recently, with telescopic intramedullary nails. Despite the proven effectiveness, external approaches are intrusive to the patient's life while intramedullary nailing damages the growth plates, making them unsuitable for pediatric patients. An internal DO plate fixator (IDOPF) was developed for pediatric patients to address these limitations. The objective of this study was to test the hypothesis that the IDOPF can withstand a partial weight bearing scenario and create a favorable mechanical microenvironment at the osteotomy gap for bone regeneration as the device elongates. A finite element model of a surrogated long bone diaphysis osteotomy fixation by means of the IDOPF was created and subjected to axial compression, bending and torsion. As the osteotomy gap increased from 2 mm to 20 mm, under compression, The average axial interfragmentary strains decreased from 2.33% to 0.35%. Stress increased from 179 MPa to 281 MPa at the contact interfaces of the telescopic compartments, which exceeded the endurance limit of stainless steel (270 MPa) but was below its yield limit (415 MPa). These results demonstrate, that the IDOPF can withstand a partial load bearing scenario and provide a stable biomechanical environment conductive to bone healing. However, high contact stresses at the telescopic interfaces of the device are likely to cause wear, as is frequently reported in telescopic fixators. This study is a step towards refining the IDOPF design for clinical use.

A stemless anatomic shoulder arthroplasty design provides increased cortical medial calcar bone loading in variable bone densities compared to a short stem implant

Background

Several studies have reported proximal bone resorption in stemless and press-fit short-stem humeral implants for anatomic total shoulder arthroplasty. The purpose of this biomechanical study was to evaluate implant and cortical bone micromotion of a cortical rim-supported stemless implant compared to a press-fit short stem implant during cyclic loading and static compression testing.

Methods

Thirty cadaveric humeri were assigned to 3 groups based on a previously performed density analysis, adopting the metaphyseal and epiphyseal and inferior supporting bone densities for multivariate analyses. Implant fixation was performed in stemless implant in low bone density (SL-L, n = 10) or short stem implant in low bone density (Stem-L, n = 10) and in stemless implant in high bone density (SL-H, n = 10). Cyclic loading with 220 N, 520 N, and 820 N over 1000 cycles at 1.5 Hz was performed with a constant valley load of 25 N. Optical recording allowed for spatial implant tracking and quantification of cortical bone deformations in the medial calcar bone region. Implant micromotion was measured as rotational and translational displacement. Load-to-failure testing was performed at a rate of 1.5 mm/s with ultimate load and stiffness measured.

Results

The SL-H group demonstrated significantly reduced implant micromotion compared to both low-density groups (SL-L: P = .014; Stem-L: P = .031). The Stem-L group showed significantly reduced rotational motion and variance in the test results at the 820-N load level compared to the SL-L group (equal variance: P = .012). Implant micromotion and reversible bone deformation were significantly affected by increasing load (P < .001), metaphyseal cancellous (P = .023, P = .013), and inferior supporting bone density (P = .016, P = .023). Absolute cortical bone deformation was significantly increased with stemless implants in lower densities and percentage reversible bone deformation was significantly higher for the SL-H group (21 ± 7%) compared to the Stem-L group (12 ± 6%, P = .017).

Conclusion

A cortical rim-supported stemless implant maintained proximally improved dynamic bone loading in variable bone densities compared to a press-fit short stem implant. Biomechanical time-zero implant micromotion in lower bone densities was comparable between short stem and stemless implants at rehabilitation load levels (220 N, 520 N), but with higher cyclic stability and reduced variability for stemmed implantation at daily peak loads (820 N).

Methods to accelerate fracture healing - a narrative review from a clinical perspective

Bone regeneration is a complex pathophysiological process determined by molecular, cellular, and biomechanical factors, including immune cells and growth factors. Fracture healing usually takes several weeks to months, during which patients are frequently immobilized and unable to work. As immobilization is associated with negative health and socioeconomic effects, it would be desirable if fracture healing could be accelerated and the healing time shortened. However, interventions for this purpose are not yet part of current clinical treatment guidelines, and there has never been a comprehensive review specifically on this topic. Therefore, this narrative review provides an overview of the available clinical evidence on methods that accelerate fracture healing, with a focus on clinical applicability in healthy patients without bone disease. The most promising methods identified are the application of axial micromovement, electromagnetic stimulation with electromagnetic fields and direct electric currents, as well as the administration of growth factors and parathyroid hormone. Some interventions have been shown to reduce the healing time by up to 20 to 30%, potentially equivalent to several weeks. As a combination of methods could decrease the healing time even further than one method alone, especially if their mechanisms of action differ, clinical studies in human patients are needed to assess the individual and combined effects on healing progress. Studies are also necessary to determine the ideal settings for the interventions, i.e., optimal frequencies, intensities, and exposure times throughout the separate healing phases. More clinical research is also desirable to create an evidence base for clinical guidelines. To make it easier to conduct these investigations, the development of new methods that allow better quantification of fracture-healing progress and speed in human patients is needed.

Long-term continuous instrumented insole-based gait analyses in daily life have advantages over longitudinal gait analyses in the lab to monitor healing of tibial fractures

Introduction: Monitoring changes in gait during rehabilitation allows early detection of complications. Laboratory-based gait analyses proved valuable for longitudinal monitoring of lower leg fracture healing. However, continuous gait data recorded in the daily life may be superior due to a higher temporal resolution and differences in behavior. In this study, ground reaction force-based gait data of instrumented insoles from longitudinal intermittent laboratory assessments were compared to monitoring in daily life. Methods: Straight walking data of patients were collected during clinical visits and in between those visits the instrumented insoles recorded all stepping activities of the patients during daily life. Results: Out of 16 patients, due to technical and compliance issues, only six delivered sufficient datasets of about 12 weeks. Stance duration was longer (p = 0.004) and gait was more asymmetric during daily life (asymmetry of maximal force p < 0.001, loading slope p = 0.001, unloading slope p < 0.001, stance duration p < 0.001). Discussion: The differences between the laboratory assessments and the daily-life monitoring could be caused by a different and more diverse behavior during daily life. The daily life gait parameters significantly improved over time with union. One of the patients developed an infected non-union and showed worsening of force-related gait parameters, which was earlier detectable in the continuous daily life gait data compared to the lab data. Therefore, continuous gait monitoring in the daily life has potential to detect healing problems early on. Continuous monitoring with instrumented insoles has advantages once technical and compliance problems are solved.

Early Resistance Rehabilitation Improves Functional Regeneration Following Segmental Bone Defect Injury

Mechanical loading is integral to bone development and repair. The application of mechanical loads through rehabilitation are regularly prescribed as a clinical aide following severe bone injuries. However, current rehabilitation regimens typically involve long periods of non-loading and rely on subjective patient feedback, leading to muscle atrophy and soft tissue fibrosis. While many pre-clinical studies have focused on unloading, ambulatory loading, or direct mechanical compression, rehabilitation intensity and its impact on the local strain environment and subsequent bone healing have largely not been investigated. This study combines implantable strain sensors and subject-specific finite element models in a pre-clinical rodent model with a defect size on the cusp of critically-sized. Animals were enrolled in either high or low intensity rehabilitation one week post injury to investigate how rehabilitation intensity affects the local mechanical environment and subsequent functional bone regeneration. The high intensity rehabilitation animals were given free access to running wheels with resistance, which increased local strains within the regenerative niche by an average of 44% compared to the low intensity (no-resistance) group. Finite element modeling demonstrated that resistance rehabilitation significantly increased compressive strain by a factor of 2.0 at week 1 and 4.45 after 4 weeks of rehabilitation. The resistance rehabilitation group had significantly increased regenerated bone volume and higher bone bridging rates than its sedentary counterpart (bone volume: 22.00 mm3 ± 4.26 resistance rehabilitation vs 8.00 mm3 ± 2.27 sedentary; bridging rates: 90% resistance rehabilitation vs 50% sedentary). In addition, animals that underwent resistance running had femurs with improved mechanical properties compared to those left in sedentary conditions, with failure torque and torsional stiffness values matching their contralateral, intact femurs (stiffness: 0.036 Nm/deg ± 0.006 resistance rehabilitation vs 0.008 Nm/deg ± 0.006 sedentary). Running on a wheel with no resistance rehabilitation also increased bridging rates (100% no resistance rehabilitation vs 50% sedentary). Analysis of bone volume and von Frey suggest no-resistance rehabilitation may improve bone regeneration and hindlimb functionality. These results demonstrate the potential for early resistance rehabilitation as a rehabilitation regimen to improve bone regeneration and functional recovery.

The absence of immediate stimulation delays bone healing

AIM

Secondary bone healing requires an adequate level of mechanical stimulation expressed by the extent of interfragmentary motion in the fracture. However, there is no consensus about when the mechanical stimulation should be initiated to ensure a timely healing response. Therefore, this study aims to compare the effect of the immediate and delayed application of mechanical stimulation in a large animal model.

METHODS

Twelve Swiss White Alpine sheep underwent partial osteotomy of a tibia that was stabilised with an active fixator inducing well-controlled mechanical stimulation. Animals were randomly assigned into two groups with different stimulation protocols. The immediate group received daily stimulation (1000 cycles/day) from the first day post-operation, while in the delayed group, stimulation began only on the 22nd day post-operation. Healing progression was evaluated daily by measuring the in vivo stiffness of the repair tissue and by quantifying callus area on weekly radiographs. All animals were euthanised five weeks post-op. Post-mortem callus volume was determined from high-resolution computer tomography (HRCT).

RESULTS

Fracture stiffness (p < 0.05) and callus area (p < 0.01) were significantly larger for the immediate group compared to the delayed stimulation group. In addition, the callus volume measured on the post-mortem HRCT showed 319 % greater callus volume for the immediate stimulation group (p < 0.01).

CONCLUSIONS

This study demonstrates that a delay in the onset of mechanical stimulation retards fracture callus development and that mechanical stimulation already applied in the early post-op phase promotes bone healing.

Primary Stability and Bone Contact Loading Evaluation of Suture and Screw based Coracoid Graft Fixation for Anterior Glenoid Bone Loss

BACKGROUND

Reconstruction techniques for anterior glenoid bone loss have seen a trend from screws to suture-based fixations. However, comparative biomechanical data, including primary fixation and glenoid-graft contact pressure mapping, are limited.

HYPOTHESIS

Suture-based bone block cerclage (BBC) and suspensory suture button (SB) techniques provide similar primary fixation and cyclic stability to double-screw fixation but with higher contact loading at the bony interface.

STUDY DESIGN

Controlled laboratory study.

METHODS

In total, 60 cadaveric scapulae were prepared to simulate anterior glenoid bone loss with coracoid autograft reconstruction. Graft fixation was performed with 3 different techniques: (1) an interconnected all-suture BBC, (2) 2 SB suspensions, and (3) 2 screws. Initial compression was analyzed during primary fixation. Cyclic peak loading with 50 N and 100 N over 250 cycles at 1 Hz was performed with a constant valley load of 25 N. Optical recording and pressure foils allowed for spatial bone block tracking and contact pressure mapping at the glenoid-graft interface. Load-to-failure testing was performed at a rate of 1.5 mm/s with ultimate load and stiffness measured.

RESULTS

Initial graft compression was higher with screw fixation (141 ± 5 N) compared with suture-based fixations (P < .001), with BBC fixation providing significantly higher compression than SB fixation (116 ± 7 N vs. 91 ± 5 N; P < .001). Spatial bone block migration and ultimate failure load were similar between the BBC and screw groups. The SB group showed significantly increased bone block translation (3.1 ± 1.0 mm; P≤ .014) and rotation (2.5°± 1.4°; P≤ .025) and significantly lower ultimate failure load (180 ± 53 N) compared with the BBC (P = .046) and screw (P = .002) groups. Both suture-based fixations provided significantly increased graft-glenoid contact loading with higher pressure amplitudes (P≤ .032) and contact pressure after cyclic loading (+13%; SB: P = .007; BBC: P = .004) compared with screw fixation.

CONCLUSION

Both SB and interconnected cerclage fixation improved dynamic contact loading compared with screw fixation in a biomechanical glenoid bone loss model. Cerclage fixation was biomechanically comparable with screw fixation but with a greater variability. SB fixation showed significantly lower primary fixation strength and greater bone block rotation and migration.

CLINICAL RELEVANCE

Suture-based bone block fixations improved graft-glenoid contact loading, but the overall clinical consequence on healing remains unclear.

Wireless Measurements Using Electrical Impedance Spectroscopy to Monitor Fracture Healing

There is an unmet need for improved, clinically relevant methods to longitudinally quantify bone healing during fracture care. Here we develop a smart bone plate to wirelessly monitor healing utilizing electrical impedance spectroscopy (EIS) to provide real-time data on tissue composition within the fracture callus. To validate our technology, we created a 1-mm rabbit tibial defect and fixed the bone with a standard veterinary plate modified with a custom-designed housing that included two impedance sensors capable of wireless transmission. Impedance magnitude and phase measurements were transmitted every 48 h for up to 10 weeks. Bone healing was assessed by X-ray, µCT, and histology. Our results indicated the sensors successfully incorporated into the fracture callus and did not impede repair. Electrical impedance, resistance, and reactance increased steadily from weeks 3 to 7-corresponding to the transition from hematoma to cartilage to bone within the fracture gap-then plateaued as the bone began to consolidate. These three electrical readings significantly correlated with traditional measurements of bone healing and successfully distinguished between union and not-healed fractures, with the strongest relationship found with impedance magnitude. These results suggest that our EIS smart bone plate can provide continuous and highly sensitive quantitative tissue measurements throughout the course of fracture healing to better guide personalized clinical care.

Tensioning device increases coracoid bone block healing rates in arthroscopic Latarjet procedure with suture-button fixation

BACKGROUND

There is growing interest in using suture buttons for coracoid fixation to avoid the complications associated with screws during the Latarjet procedure. However, achieving bone block healing is critical for successful shoulder stabilization and return to sport. The purpose of this study was to assess and compare the healing rates and positioning of the coracoid bone block fixed with cortical suture buttons that were either manually tensioned (using a knot pusher) or mechanically tensioned (using a tensioning device) during arthroscopic Latarjet procedures.

METHODS

This prospective, nonrandomized, comparative study enrolled 69 consecutive patients (mean age, 27 years) who underwent an arthroscopic guided Latarjet procedure with suture-button fixation. Hand tensioning was performed in the first 34 shoulders, whereas the next 35 shoulders underwent mechanical tensioning. Twelve patients (17%) had a history of failed Bankart stabilization. The characteristics of the patients in each group in terms of age, sex, type of sport, bone loss, number of previous failed surgical procedures, smoking, and length of follow-up were comparable. Intraoperatively, the tensioning device was set at 100 N successively 3 times until complete immobilization of the bone block was confirmed, as assessed with a probe. The primary outcome measure was coracoid bone block union and position on computed tomography scan images at 6 months' follow-up. Secondary outcome measures included functional outcome scores, shoulder stability, return to sports, and complications at last follow-up.

RESULTS

Overall, the rate of bone block healing was 74% (25 of 34 patients) in the hand-tensioning group and 94% (33 of 35 patients) in the mechanical tensioning group (P = .043). Smoking was an independent risk factor associated with nonunion (P < .001) in each group. Patient age, size of the preoperative glenoid bone defect (<20% or >20%), and a history of surgery were not found to have any influence. The tensioning modality did not affect the bone block position, which was subequatorial in 92% of the cases and flush with the glenoid rim in 92%. At a mean of 34 months of follow-up (range, 24-62 months), 96% of the patients (65 of 69) had a stable shoulder and 87% returned to sports. At final follow-up, no significant difference in clinical scores was noted between the groups; no neurologic or hardware complications were observed.

CONCLUSION

Mechanical tensioning achieves significantly higher healing rates than hand tensioning during the arthroscopic Latarjet procedure with suture-button fixation. The use of a suture-tensioning device is a key step to the suture-button fixation technique during arthroscopic Latarjet procedures. By making the suture-button construct rigid, the tensioning device transforms the initially flexible suture into a "rigid fixation", similar to a bolt (or a rivet).

New Ground-Breaking Strategies in Bone Regeneration—In Memory of Nerio Ceroni

This editorial article is dedicated to the memory of the Nerio Ceroni, the grandfather of the first author [...]

Evaluation of Bone Consolidation in External Fixation with an Electromechanical System

The monitoring of fracture or osteotomy healing is vital for orthopedists to help advise, if necessary, secondary treatments for improving healing outcomes and minimizing patient suffering. It has been decades since osteotomy stiffness has been identified as one main parameter to quantify and qualify the outcome of a regenerated callus. Still, radiographic imaging remains the current standard diagnostic technique of orthopedists. Hence, with recent technological advancements, engineers need to use the new branches of knowledge and improve or innovate diagnostic technologies. An electromechanical system was developed to help diagnose changes in osteotomy stiffness treated with the external fixator LRS Orthofix®. The concept was evaluated experimentally and numerically during fracture healing simulation using two different models: a simplified model of a human tibia, consisting of a nylon bar with a diameter of 30 mm, and a synthetic tibia with the anatomical model from fourth-generation Sawbones®. Moreover, Sawbones® blocks with different densities simulated the mechanical characteristics of the regenerated bone in many stages of bone callus growth. The experimental measurements using the developed diagnostic were compared to the numerically simulated results. For this external fixator, it was possible to show that the displacement in osteotomy was always lower than the displacement prescribed in the elongator. Nevertheless, a relationship was established between the energy consumption by the electromechanical system used to perform callus stimulus and the degree of osteotomy consolidation. Hence, this technology may lead to methodologies of mechanical stimulation for regenerating bone, which will play a relevant role for bedridden individuals with mobility limitations.

Short-Term Bone Healing Response to Mechanical Stimulation-A Case Series Conducted on Sheep

It is well known that mechanical stimulation promotes indirect fracture healing by triggering callus formation. We investigated the short-term response of healing tissue to mechanical stimulation to compare the changes in tissue stiffness during stimulation and resting phases in a preclinical case-series. Four sheep underwent a tibial osteotomy and were instrumented with a custom-made active fixator which applied a mechanical stimulation protocol of 1000 cycles/day, equally distributed over 12 h, followed by 12 h of rest. During each cycle, a surrogate metric for tissue stiffness was measured, enabling a continuous real-time monitoring of the healing progression. A daily stiffness increase during stimulation and an increase during resting were evaluated for each animal. One animal had to be excluded from the evaluation due to technical reasons. For all included animals, the stiffness began to increase within the second week post-op. A characteristic pattern was observed during daily measurements: the stiffness dropped considerably within the first stimulation cycles followed by a steady rise throughout the rest of the stimulation phase. However, for all included animals, the average daily stiffness increase within the first three weeks post operation was larger during resting than during stimulation (Sheep I: 16.9% vs. -5.7%; Sheep II: 14.7% vs. -1.8%; Sheep III: 8.9% vs. 1.6%). A continuous measurement of tissue stiffness together with a controlled fracture stimulation enabled the investigation of the short-term effects of specific stimulatory parameters, such as resting periods. Resting was identified as a potentially determining factor for bone healing progression. Optimizing the ratio between stimulation and resting may contribute to more robust fracture healing in the future.