Superior Biomechanical Performance Research Articles

Overview of Achilles Tendon Injury Treatment

Achilles tendon rupture is a prevalent injury, particularly among middle-aged individuals who participate in high-demand athletics. This article reviews the anatomy, risk factors, diagnosis, and current treatment strategies for Achilles tendon rupture, with a focus on surgical and non-surgical approaches. The traditional open repair technique is still a widespread surgical approach that uses a large incision to reconnect the tendon directly. However, complications and infections may occur, so percutaneous or mini-open techniques can be changed depending on the patient's condition. Various suture techniques, such as Bunnell, Modified Kessler, and Tsuge, have been evaluated in clinical settings, with braided polyester sutures demonstrating superior biomechanical performance over monofilament polydioxanone sutures. Despite the effectiveness of surgical intervention, non-surgical treatment remains an option for specific patient populations, though it is associated with a slightly higher re-rupture rate. Postoperative rehabilitation is crucial for restoring function, with early weight-bearing and mechanical stimulation playing key roles in successful recovery.

Biomechanical comparison of Gofried positive support reduction of Pauwels type III femoral neck fractures: A finite elements analysis

ObjectiveThis study aims to investigate the biomechanical characteristics of non-anatomical reduction and different screw positions on the stability of Pauwels type III femoral neck fractures. MethodsThree-dimensional finite element models of femoral neck fractures were constructed using CT images. Four types of internal fixation methods were simulated, including biplane double-supported screw fixation (BDSF), three inverted triangular parallel cannulated screws (3CS), new parallel cannulated screws with posterior screws moving down (New 3CS), and two parallel cannulated screws (2CS). von Mises stress and total displacement were compared between the fracture models after the femoral head was subjected to an axial load of 2100 N. Stress and displacement data for the implants and the femur were recorded for each fixation method and compared. ResultsThe results demonstrated that positive reduction of a Pauwels type III femoral neck fracture provided greater stability than neutral or negative reduction. Specifically, the BDSF group showed the lowest maximum von Mises stress in the femur (17.66 MPa) in positive reduction, compared to 3CS (21.08 MPa), New 3CS (22.14 MPa), and 2CS (36.57 MPa). The total displacement of positive reduction in the BDSF group was 0.3143 mm, which was lower than in the 3CS (0.3498 mm), New 3CS (0.3343 mm), and 2CS (0.4533 mm) groups. The stress distribution in the positive support reduction group was lower than that of the other groups, indicating better load distribution. Among the three-screw fixation methods, the New 3CS system exhibited the highest stress in the screws (with a peak of 28.62 MPa), while the 2CS group displayed the highest stresses overall, both in the femur and the screws. ConclusionFor Pauwels type III femoral neck fractures, a positive support reduction with BDSF fixation exhibited superior biomechanical performance than negative reduction. Based on the finite element analysis conducted in this study, the positive support reduction with BDSF fixation can enhance fixation stability, suggesting that non-anatomical reduction is recommended.

Biomechanical Comparison of Three Modified Kessler Techniques for Flexor Tendon Repair: Implications in Surgical Practice and Early Active Mobilization.

Objective: Managing flexor tendon injuries surgically remains challenging due to the ongoing debate over the most effective suture technique and materials. An optimal repair must be technically feasible while providing enough strength to allow for early active mobilization during the post-operative phase. This study aimed to assess the biomechanical properties of three modified Kessler repair techniques using two different suture materials: a conventional two-strand and a modified four-strand Kirchmayr-Kessler repair using 3-0 Prolene® (2s-KK-P and 4s-KK-P respectively), and a four-strand Kessler-Tsuge repair using 4-0 FiberLoop® (4s-KT-FL). Methods: Human flexor digitorum profundus (FDP) tendons were retrieved from Thiel-embalmed prosections. For each tendon, a full-thickness cross-sectional incision was created, and the ends were reattached using either a 2s-KK-P (n = 30), a 4s-KK-P (n = 30), or a 4s-KT-FL repair (n = 30). The repaired tendons were tested using either a quasi-static (n = 45) or cyclic testing protocol (n = 45). Maximum force (Fmax), 2 mm gap force (F2mm), and primary failure modes were recorded. Results: In both quasi-static and cyclic testing groups, tendons repaired using the 4s-KT-FL approach exhibited higher Fmax and F2mm values compared to the 2s-KK-P or 4s-KK-P repairs. Fmax was significantly higher with a 4s-KK-P versus 2s-KK-P repair, but there was no significant difference in F2mm. Suture pull-out was the main failure mode for the 4s-KT-FL repair, while suture breakage was the primary failure mode in 2s- and 4s-KK-P repairs. Conclusions: FDP tendons repaired using the 4s-KT-FL approach demonstrated superior biomechanical performance compared to 2s- and 4s-KK-P repairs, suggesting that the 4s-KT-FL tendon repair could potentially reduce the risk of gapping or re-rupture during early active mobilization.

Biomechanical characteristic differences of two new types of intramedullary nail devices in the treatment of comminuted intertrochanteric fractures of femur: a comparative study based on finite element analysis

ObjectiveGiven the recent application of two new types of intramedullary nail devices in the treatment of comminuted femoral intertrochanteric fractures (CFIFs), there is still a lack of deep understanding and comparative evaluation of their biomechanical properties. Therefore, this study aims to systematically compare the advantages and disadvantages of these two new devices with traditional proximal femoral nail antirotation (PFNA) and InterTan nails in the fixation of CFIFs through finite element analysis.MethodsBased on the validated finite element model, this study constructed an accurate CFIFs model. In this model, PFNA, InterTan nails, proximal femoral bionic nails (PFBN), and new intramedullary systems (NIS) were implanted, totaling four groups of finite element models. Each group of models was subjected to simulation tests under a vertical load of 2100 N to evaluate the displacement and Von Mises stress (VMS) distribution of the femur and intramedullary nail devices.ResultsUnder a vertical load of 2100 N, a comparative analysis of the four finite element models showed that the NIS device exhibited the most superior performance in terms of peak displacement, while the PFNA device performed relatively poorly. Although the NIS device had the highest peak stress in the femur, it had the smallest peak displacement of both the femur and intramedullary nail devices, and the peak stress was mainly concentrated on the lateral side of the femur, with significantly lower stress in the proximal femur compared to the other three intramedullary nail devices. In contrast, the PFBN device had the lowest peak stress in the femur, and its peak displacement of both the femur and intramedullary nail devices was also less than that of PFNA and InterTan nails.ConclusionThis study demonstrates that in the treatment of CFIFs, PFBN and NIS devices exhibit superior biomechanical performance compared to traditional PFNA and InterTan nail devices. Especially the NIS device, which can achieve good biomechanical results when fixing femoral intertrochanteric fractures with missing medial wall. Therefore, both PFBN and NIS devices can be considered reliable closed reduction and internal fixation techniques for the treatment of CFIFs, with potential clinical application value.

Influence of Connector Design on Displacement and Micromotion in Tooth-Implant Fixed Partial Dentures Using Different Lengths and Diameters: A Three-Dimensional Finite Element Study.

The literature presents insufficient data evaluating the displacement and micromotion effects resulting from the combined use of tooth-implant connections in fixed partial dentures. Analyzing the biomechanical behavior of tooth-implant fixed partial denture (FPD) prothesis is vital for achieving an optimum design and successful clinical implementation. The objective of this study was to determine the relative significance of connector design on the displacement and micromotion of tooth-implant-supported fixed dental prostheses under occlusal vertical loading. A unilateral Kennedy class I mandibular model was created using a 3D reconstruction from CT scan data. Eight simulated designs of tooth-implant fixed partial dentures (FPDs) were split into two groups: Group A with rigid connectors and Group B with non-rigid connectors. The models were subjected to a uniform vertical load of 100 N. Displacement, strain, and stress were computed using finite element analysis. The materials were defined as isotropic, homogeneous, and exhibiting linear elastic properties. This study focused on assessing the maximum displacement in various components, including the bridge, mandible, dentin, cementum, periodontal ligament (PDL), and implant. Displacement values were predominantly higher in Group B (non-rigid) compared to Group A (rigid) in all measured components of the tooth-implant FPDs. Accordingly, a statistically significant difference was observed between the two groups at the FPD bridge (p value = 0.021 *), mandible (p value = 0.021 *), dentin (p value = 0.043 *), cementum (p value = 0.043 *), and PDL (p value = 0.043 *). Meanwhile, there was an insignificant increase in displacement values recorded in the distal implant (p value = 0.083). This study highlighted the importance of connector design in the overall stability and performance of the prosthesis. Notably, the 4.7 mm × 10 mm implant in Group B showed a displacement nearly 92 times higher than its rigid counterpart in Group A. Overall, the 5.7 mm × 10 mm combination of implant length and diameter showcased the best performance in both groups. The findings demonstrate that wider implants with a proportional length offer greater resistance to displacement forces. In addition, the use of rigid connection design provides superior biomechanical performance in tooth-implant fixed partial dentures and reduces the risk of micromotion with its associated complications such as ligament overstretching and implant overload, achieving predictable prognosis and enhancing the stability of the protheses.

Biomechanical evaluation of Gamma 3 nail with anti-rotation screw fixation for unstable femoral neck fractures: a biomechanical study

This study aims to evaluate the biomechanical performance of the Gamma 3 nail with an anti-rotation screw (GNS) and compare it to two established gold-standard methods for treating unstable femoral neck fractures (UFNFs). Synthetic bone models were prepared with Pauwels’ type III osteotomy and an additional posterior wedge. Three different implant configurations were tested: three cannulated crews (3CS) in an inverted triangle configuration, a dynamic hip screw with an anti-rotation screw (DHSS), and GNS. Non-destructive cyclic axial loading was applied at 7° adduction, with 1000 cycles ranging from 100 to 1000 N. Subsequently, a construct failure test was conducted using progressive axial compression, and fracture reduction loss was recorded. The average axial stiffness was 321 ± 52 N/mm for 3CS, 430 ± 71 N/mm for DHSS, and 519 ± 104 N/mm for GNS. The average ultimate failure loads were 2699.3 N for 3CS, 3427.1 N for DHSS, and 3758.9 N for GNS. GNS demonstrated significantly greater axial stiffness compared to the other two groups (P < 0.05). Both DHSS and GNS exhibited similar failure loading, which were greater than those of 3CS (P < 0.05). GNS offers the advantages of a minimally invasive and intramedullary implant with comparable stability to the DHSS system. Moreover, GNS demonstrated superior biomechanical performance compared to 3 CS configuration.

Three-dimensional planning, navigation, patient-specific instrumentation and mixed reality in shoulder arthroplasty: a digital orthopedic renaissance.

Accurate component placement in shoulder arthroplasty is crucial for avoiding complications, achieving superior biomechanical performance and optimizing functional outcomes. Shoulder and elbow surgeons have explored various methods to improve surgical understanding and precise execution including preoperative planning with 3D computed tomography (CT), patient-specific instrumentation (PSI), intraoperative navigation, and mixed reality (MR). 3D preoperative planning facilitated by CT scans and advanced software, enhances surgical precision, influences decision-making for implant types and approaches, reduces errors in guide pin placement, and contributes to cost-effectiveness. Navigation demonstrates benefits in reducing malpositioning, optimizing baseplate stability, improving humeral cut, and potentially conserving bone stock, although challenges such as varied operating times and costs warrant further investigation. The personalized patient care and enhanced operational efficiency associated with PSI are not only attractive for achieving desired component positions but also hold promise for improved outcomes in complex cases involving glenoid bone loss. Augmented reality (AR) and virtual reality (VR) technologies play a pivotal role in reshaping shoulder arthroplasty. They offer benefits in preoperative planning, intraoperative guidance, and interactive surgery. Studies demonstrate their effectiveness in AR-guided guidewire placement, providing real-time surgical advice during reverse total shoulder arthroplasty (RTSA). Additionally, these technologies show promise in orthopedic training, delivering superior realism and accelerating learning compared to conventional methods.

Debulking of the Femoral Stem in a Primary Total Hip Joint Replacement: A Novel Method to Reduce Stress Shielding.

In current-generation designs of total primary hip joint replacement, the prostheses are fabricated from alloys. The modulus of elasticity of the alloy is substantially higher than that of the surrounding bone. This discrepancy plays a role in a phenomenon known as stress shielding, in which the bone bears a reduced proportion of the applied load. Stress shielding has been implicated in aseptic loosening of the implant which, in turn, results in reduction in the in vivo life of the implant. Rigid implants shield surrounding bone from mechanical loading, and the reduction in skeletal stress necessary to maintain bone mass and density results in accelerated bone loss, the forerunner to implant loosening. Femoral stems of various geometries and surface modifications, materials and material distributions, and porous structures have been investigated to achieve mechanical properties of stems closer to those of bone to mitigate stress shielding. For improved load transfer from implant to femur, the proposed study investigated a strategic debulking effort to impart controlled flexibility while retaining sufficient strength and endurance properties. Using an iterative design process, debulked configurations based on an internal skeletal truss framework were evaluated using finite element analysis. The implant models analyzed were solid; hollow, with a proximal hollowed stem; FB-2A, with thin, curved trusses extending from the central spine; and FB-3B and FB-3C, with thick, flat trusses extending from the central spine in a balanced-truss and a hemi-truss configuration, respectively. As outlined in the International Organization for Standardization (ISO) 7206 standards, implants were offset in natural femur for evaluation of load distribution or potted in testing cylinders for fatigue testing. The commonality across all debulked designs was the minimization of proximal stress shielding compared to conventional solid implants. Stem topography can influence performance, and the truss implants with or without the calcar collar were evaluated. Load sharing was equally effective irrespective of the collar; however, the collar was critical to reducing the stresses in the implant. Whether bonded directly to bone or cemented in the femur, the truss stem was effective at limiting stress shielding. However, a localized increase in maximum principal stress at the proximal lateral junction could adversely affect cement integrity. The controlled accommodation of deformation of the implant wall contributes to the load sharing capability of the truss implant, and for a superior biomechanical performance, the collared stem should be implanted in interference fit. Considering the results of all implant designs, the truss implant model FB-3C was the best model.

Segment selection for fusion and artificial disc replacement in the hybrid surgical treatment of noncontiguous cervical spondylosis: a finite element analysis.

Introduction: The treatment of skip-level cervical degenerative disease (CDD) with no degenerative changes observed in the intervening segment (IS) is complicated. This research aims to provide a reference basis for selecting treatment approaches for noncontiguous CDD. Methods: To establish accurate finite element models (FEMs), this study included computed tomography (CT) data from 21 patients with CDD (10 males and 11 females) for modeling. The study primarily discusses four cross-segment surgical approaches: upper (C3/4) anterior cervical discectomy and fusion (ACDF) and lower (C5/6) cervical disc arthroplasty (CDA), FA model; upper CDA (C3/4) and lower ACDF (C5/6), AF model; upper ACDF (C3/4) and lower ACDF (C5/6), FF model; upper CDA (C3/4) and lower CDA (C5/6), AA model. An initial axial load of 73.6 N was applied at the motion center using the follower load technique. A moment of 1.0Nm was applied at the center of the C2 vertebra to simulate the overall motion of the model. The statistical analysis was conducted using STATA version 14.0. Statistical significance was defined as a p value less than 0.05. Results: The AA group had significantly greater ROM in flexion and axial rotation in other segments compared to the FA group (p < 0.05). The FA group consistently exhibited higher average intervertebral disc pressure in C2/3 during all motions compared to the AF group (p < 0.001); however, the FA group displayed lower average intervertebral disc pressure in C6/7 during all motions (p < 0.05). The AA group had lower facet joint contact stresses during extension in all segments compared to the AF group (p < 0.05). The FA group exhibited significantly higher facet joint contact stresses during extension in C2/3 (p < 0.001) and C6/7 (p < 0.001) compared to the AF group. Discussion: The use of skip-level CDA is recommended for the treatment of non-contiguous CDD. The FA construct shows superior biomechanical performance compared to the AF construct.

Hybrid cortical bone trajectory and modified cortical bone trajectory techniques in transforaminal lumbar interbody fusion at L4-L5 segment: A finite element analysis

BackgroundThe academia has increasingly acknowledged the superior biomechanical performance of the hybrid fixation technique in recent years. However, there is a lack of research on the hybrid fixation technique using BCS (Bilateral Cortical Screws) and BMCS (Bilateral Modified Cortical Screws). This study aims to investigate the biomechanical performance of the BCS and BMCS hybrid fixation technique in transforaminal lumbar interbody fusion (TLIF) at the L4-L5 segment in a complete lumbar-sacral finite element model. MethodsThree cadaver specimens are used to construct three lumbar-sacral finite element models. The biomechanical properties of various fixation technologies (BCS-BCS, BMCS-BMCS, BMCS-BCS, and BCS-BMCS) are evaluated at the L4-5 segment with a TLIF procedure conducted, including the range of motion (ROM) of the L4-5 segment, as well as the stress experienced by the cage, screws, and rods. The testing is conducted under specific loading conditions, including a compressive load of 400 N and a torque of 7.5Nm, subjecting the model to simulate flexion, extension, lateral bending, and rotation. ResultsNo significant variations are seen in the ROM at the L4-5 segment when comparing the four fixation procedures during flexion and extension. However, when it comes to lateral bending and rotation, the ROM is ordered in descending order as BCS-BCS, BCS-BMCS, BMCS-BMCS, and BMCS-BCS. The maximum stress experienced by the cage is observed to be highest within the BMCS-BCS technique during movements including flexion, extension, and lateral bending. Conversely, the BMCS-BMCS technique exhibits the highest cage stress levels during rotational movements. The stress applies to the screws and rods order the sequence of BCS-BCS, BCS-BMCS, BMCS-BCS, and BMCS-BMCS throughout all four working conditions. ConclusionThe BMCS-BCS technique shows better biomechanical performance with less ROM and lower stress on the internal fixation system compared to other fixation techniques. BMCS-BMCS technology has similar mechanical performance to BMCS-BCS but has more contact area between screws and cortical bone, making it better for patients with severe osteoporosis.

Does the angle between dynamic hip screw and anti-rotation screw affect the outcome of vertically oriented femoral neck fractures? A biomechanical analysis and clinical results

ObjectiveTo analyze the effects of the angle between dynamic hip screw (DHS) and anti-rotation screw (AS) on vertically oriented femoral neck fractures (VOFNFs) and investigate the clinical results of them. MethodsEighteen synthetic femurs were simulated and divided into 3 groups. The angle between DHS and AS in anteroposterior-view was marked as α, and in lateral-view was marked as β, thus the total angle (TA) was defined as the summation of α and β. The groups were categorized as group A (TA ≤ 5°), B (5° < TA ≤ 10°), and C (TA > 10°), respectively. All samples were tested under incremental, cyclical loading, and loading to failure. In clinic, 80 consecutive VOFNFs in 78 patients were treated with DHS plus AS. The patients were divided into 2 groups, including 48 fractures in parallel group (TA ≤10°) and 32 in angular group (TA >10°). ResultsGroup A and B survived during incremental and cyclical loading and endured longer than group C. Axial stiffness and failure loads were not different between group A and B, and greater than group C. Fracture gaps compressive stress was highest in group A, followed by group B and C. Forty-one fractures in parallel group and 23 in angular group healed at final follow-up. Nonunion and osteonecrosis occurred in 3 and 4 of parallel group, and 4 and 5 of angular group. ConclusionThe construction with TA ≤10° between DHS and AS showed superior biomechanical performance and clinical results than those with TA >10°.

Biomechanical Comparison of Distal Biceps Tendon Repair Techniques: Extracortical Single-Button Inlay Fixation Versus Intracortical Double-Button Onlay Anatomic Footprint Fixation

Background: Extracortical single-button (SB) inlay repair is a commonly used distal biceps tendon technique. However, complications (eg, neurovascular injury) and nonanatomic repairs have led to the development of intracortical fixation techniques. Purpose: To compare the biomechanical stability of extracortical SB repair with an anatomic intracortical double-button (DB) repair technique. Study Design: Controlled laboratory study. Methods: The distal biceps tendon was transected in 18 cadaveric elbows from 9 donors. One elbow of each donor was randomly assigned to the extracortical SB or anatomic DB group. Both groups were cyclically loaded with 60 N over 1000 cycles between 90° of flexion and full extension. The elbow was then fixed in 90° of flexion and the repair construct loaded to failure. Gap formation and construct stiffness during cyclic loading and ultimate load to failure were analyzed. Results: When compared with the extracortical SB technique after 1000 cycles, the anatomic DB technique showed significantly less gap formation (mean ± SD, 2.7 ± 0.8 vs 1.5 ± 0.9 mm; P = .017) and significantly more construct stiffness (87.4 ± 32.7 vs 119.9 ± 31.6 N/mm; P = .023). Ultimate load to failure was not significantly different between the groups (277 ± 93 vs 285 ± 135 N; P = .859). The failure mode in the anatomic DB group was significantly different from that of the extracortical SB technique (P = .002) and was due to fracture avulsion of the cortical button in 7 of 9 specimens (vs none in the SB group). Conclusion: Our study shows that the intracortical DB technique produces equivalent or superior biomechanical performance to that of the SB technique. The DB technique may offer a clinically viable alternative to the SB repair technique. Clinical Relevance: This study suggests, at worst, an equivalent and, at best, a superior biomechanical performance of intracortical anatomic DB footprint repair at the time of surgery. However, the mode of failure suggests that this technique should not be used in patients with poor bone quality.

BIOMECHANICAL COMPARISON OF DISTAL BICEPS REPAIR TECHNIQUES: SINGLE EXTRACORTICAL BUTTON INLAY FIXATION VERSUS DOUBLE INTRACORTICAL BUTTON ONLAY ANATOMICAL FOOTPRINT FIXATION

The extracortical single-button (SB) inlay repair is one of the most preferred distal biceps tendon repair techniques. However, specific complications such as neurovascular injury and non-anatomic repairs have led to the development of techniques that utilize intracortical double-button (DB) fixation.To compare the biomechanical stability of the extracortical SB repair with the anatomical DB repair technique.Controlled laboratory study.The distal biceps tendon was transected in 18 cadaveric elbows from 9 donors. One elbow of each donor was randomly assigned to the extracortical SBor anatomical DB group. Both groups were cyclically loaded with 60N over 1000 cycles between 90° of flexion and full extension. The elbow was then fixed in 90° of flexion and the repair construct loaded to failure. Gap-formation and construct stiffness during cyclic loading, and ultimate load to failure was analysed.After 1000 cycles, the anatomical DB technique compared with the extracortical SB technique showed significantly less gap-formation (mean difference 1.2 mm; p=0.017) and significantly more construct stiffness (mean difference 31 N/mm; p=0.023). Ultimate load to failure was not significantly different comparing both groups (SB, 277 N ±92 vs. DB, 285 N ±135; p=0.859). The failure mode in the anatomical DB group was significantly different compared with the extracortical SB technique (p=0.002) and was due to fracture avulsion of the BicepsButton in 7 out of 9 specimens (vs. none in SB group).Our study shows that the intracortical DB technique produces equivalent or superior biomechanical performance to the SB technique. The DB repair technique reduces the risk of nerve injury and better restores the anatomical footprint of biceps tendon. The DB technique may offer a clinically viable alternative to the SB repair technique.

The Bone Bridge for Tibial ACL Graft Fixation: A Biomechanical Analysis of Different Tibial Fixation Methods for ACL Reconstruction.

The tibial fixation site is considered the weak link in anterior cruciate ligament (ACL) reconstruction, and conflicting results regarding the biomechanical properties of various fixation methods have been reported. To examine knots tied over a bone bridge and its biomechanical properties as a suitable tibial fixation method in ACL reconstruction. Controlled laboratory study. We divided 40 fresh-frozen porcine tibiae into 4 equal groups to evaluate flexor tendon grafts set with standard tibial fixation techniques: (1) bone bridge (BB group), (2) suspension button (SB group), (3) combined interference screw and bone bridge (IFS/BB group), and (4) combined interference screw and suspension button (IFS/SB group). Each construct was subjected to cyclic loading (1500 cycles, 50-250 N, 1 Hz) with a servohydraulic materials testing machine to measure elongation; load-to-failure testing (displacement rate: 25 mm/s) was then performed. Load to failure, stiffness, and yield load were compared between constructs using 1-way analysis of variance. The hybrid fixation constructs (IFS/BB and IFS/SB groups) showed significantly better biomechanical properties than the isolated extracortical fixation constructs (BB and SB groups) (P < .05 for all). There were no differences between the isolated extracortical fixation constructs or between the hybrid fixation constructs in elongation or load to failure; however, stiffness of the IFS/BB group was significantly higher than that of the IFS/SB group (175.3 ± 16.6 vs 144.9 ± 20.1 N/mm, respectively; P < .05). Stiffness between the SB and BB groups was not significantly different. Hybrid fixation had superior biomechanical performance compared with isolated extracortical fixation. However, tibial graft fixation using a bone bridge either as isolated extracortical fixation or combined with an interference screw for hybrid fixation showed equivalent biomechanical properties compared with suspension button-based graft fixation. The clinical use of a bone bridge for tibial graft fixation could reduce the cost for ACL reconstruction and lower the rate of implant-associated issues.

A new all-suture tension band tape fixation technique for simple olecranon fractures versus conventional tension band wire fixation: a comparative biomechanics study.

Simple transverse or short oblique olecranon fractures without articular comminution are classified as Mayo type IIA fractures and are typically treated with a tension band wire construct. Because of the high reoperation rates, frequently because of prominent hardware, all-suture tension band constructs have been introduced. It was the purpose to compare the biomechanical performance of conventional tension band wire fixation with a new all-suture tension band tape fixation for simple olecranon fractures. Mayo type IIA olecranon fractures were created in 20 cadaveric elbows from 10 donors. One elbow of each donor was randomly assigned to the tension band wire technique (group TBW) or tension band tape (Arthrex, 1.3-mm SutureTape) technique (group TBT). Both groups were cyclically loaded with 500 N over 500 cycles, after which a uniaxial displacement was performed to evaluate load to failure. Data were analyzed for gap formation after cyclic loading, construct stiffness, and ultimate load to failure, where failure was defined as fracture gap formation greater than 4.0 mm. There was no significant difference in gap formation after 500 cycles between the TBW (1.8 mm±1.3 mm) and the TBT (1.9 mm±1.1 mm) groups (P=.854). The TBT showed a tendency toward greater construct stiffness compared with the TBW construct (mean difference: 142 N/mm; P=.053). Ultimate load to failure was not significantly different comparing both groups (TBW: 1138 N±286 N vs. TBT: 1126 N±272 N; P=.928). In both groups, all repairs failed because of >4.0-mm gap formation at the fracture site and none because of tension band construct breakage. Our study shows that the TBT technique produces equivalent or superior biomechanical performance to the TBW for simple olecranon fractures. The TBT approach reduces the risk of hardware prominence and as a result mitigates against the need for hardware removal. The TBT technique offers a clinically viable alternative to TBW.

Effect of Simulated Bone Resorption on the Biomechanical Performance of Intramedullary Devices for Foot and Ankle Arthrodesis

Midfoot and subtalar arthrodesis surgeries are performed to correct foot deformities and relieve arthritic pain. These procedures often employ intramedullary (IM) devices. The aim of the present study was to evaluate the biomechanical performance of a sustained dynamic compression (SDC) IM device compared to mechanically static devices in withstanding the effects of simulated bone resorption. Mechanically static and SDC IM devices were implanted in simulated bone blocks (n = 5/device). Compressive loads were measured with a custom-made mechanism to simulate bone resorption. The construct bending stiffness was determined from a 4-point bend test. Resorption was simulated by cutting a 1 mm or 2 mm gap in the midpoint of each construct and repeating the loading (n = 6/device). Initial compressive loads after device insertion were greater in the SDC IM devices when compared to the static devices (p < .01). The SDC device was able to sustain compression from 2 mm to 5.5 mm of simulated resorption depending upon device length, while the static devices lost compression within 1 mm of simulated resorption regardless of implant length (p < .001). In the 4-point bend test, the SDC device maintained its bending stiffness during simulated resorption whereas the static device displayed a significant loss in bending stiffness after 1 mm of simulated resorption (p < .001). The SDC device exhibited a significantly higher bending stiffness than the static device (p < .001). The SDC IM device demonstrated superior biomechanical performance during simulated resorption compared to static devices (p < .001). In conclusion, the ability of SDC IM devices to maintain construct stability and sustain compression across the fusion site while adapting to bone resorption may lead to greater fusion rates and overall quicker times to fusion than static IM devices. Surgeons who perform midfoot and subtalar arthrodesis procedures should be aware of a device's ability to sustain compression, especially in cases where bone resorption and joint settling are prevalent postoperatively.

Finite Element Analysis of the Effect of Dynamic Plating on Two-Level Anterior Cervical Discectomy Fusion Biomechanics

The limitations of anterior cervical discectomy and fusion (ACDF) are related to mechanical failure of the construct after recurring subsidence and migration. In the present study, we evaluated the effect of the maximum rotation of variable angle screws on the range of motion (ROM), cage migration, and subsidence. Five finite element models were developed from a C2-C7 cervical spine model. The first model was an intact C2-C7 spine model, and the second model was an altered C2-C7 model with C4-C6 cage insertion and a 2-level static plate. The other three models were altered C2-C7 models with the same C4-C6 cage insertion and a 2-level dynamic plate. The ROM of C4-C6 in the static plate model was reduced by ∼14° from the intact model but only reduced by ∼9° in the dynamic plate models. The maximum migration and subsidence at the cage-endplate interface in the dynamic plate models were lower than those in the static plate model for all moments. The von Mises stress of the C3-C4 and C6-C7 discs in the dynamic plate models was lower than that in the static plate model. Our results indicate that dynamic plating has promising potential (greater ROM and lower von Mises stress of discs) for stabilization in multilevel anterior cervical discectomy and fusion than static plating, although both dynamic and static plates showed lower ROM than the intact model. A lower screw rotational angle resulted in superior biomechanical performance (lower incidence of migration and subsidence) compared with a higher rotational angle in multilevel applications, regardless of loading.

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

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

Titanium alloy cannulated screws and biodegradable magnesium alloy bionic cannulated screws for treatment of femoral neck fractures: a finite element analysis

BackgroundCannulated screws (CS) are one of the most widely used treatments for femoral neck fracture, however, associated with high rate of complications. In this study, we designed a new type of cannulated screws called degradable magnesium alloy bionic cannulated screws (DMBCS) and our aim was to compare the biomechanical properties of DMBCS, the traditionally used titanium alloy bionic cannulated screws (TBCS) and titanium alloy cannulated screws (TTCS).MethodsA proximal femur model was established based on CT data of a lower extremity from a voluntary healthy man. Garden type III femoral neck fracture was constructed and fixed with DMBCS, TBCS, and TTCS, respectively. Biomechanical effect which three type of CS models have on femoral neck fracture was evaluated and compared using von Mises stress distribution and displacement.ResultsIn the normal model, the maximum stress value of cortical bone and cancellous bone was 76.18 and 6.82 MPa, and the maximum displacement was 5.52 mm. Under 3 different fracture healing status, the stress peak value of the cortical bone and cancellous bone in the DMBCS fixation model was lower than that in the TTCS and TBCS fixation, while the maximum displacement of DMBCS fixation model was slightly higher than that of TTCS and TBCS fixation models. As the fracture heals, stress peak value of the screws and cortical bone of intact models are decreasing, while stress peak value of cancellous bone is increasing initially and then decreasing.ConclusionsThe DMBCS exhibits the superior biomechanical performance than TTCS and TBCS, whose fixation model is closest to the normal model in stress distribution. DMBCS is expected to reduce the rates of post-operative complications with traditional internal fixation and provide practical guidance for the structural design of CS for clinical applications.

Biomechanical Comparison of Augmentation of Engineered Tendon-Fibrocartilage-Bone Composite With Acellular Dermal Graft Using Double Rip-Stop Technique for Canine Rotator Cuff Repair.

Background:The retear rate after rotator cuff repair remains unacceptably high. Various biological engineered scaffolds have been proposed to reduce the retear rate. We have developed a double rip-stop repair with medial row knot (DRSK) technique to enhance suture-tendon strength and a novel engineered tendon-fibrocartilage-bone composite (TFBC) for rotator cuff repair.Hypothesis:DRSK rotator cuff repair augmented with TFBC will have better biomechanical properties than that of DRSK repair with an acellular dermal graft (DG).Study Design:Controlled laboratory study.Methods:Fresh-frozen canine shoulders (n = 30) and knees (n = 10) were used. TFBCs were harvested from the patellar tendon–tibia complex and prepared for rotator cuff repair. The infraspinatus tendon was sharply detached from its bony attachment and randomly assigned to the (1) control group: DRSK repair alone, (2) TFBC group: DRSK repair with TFBC, and (3) DG group: DRSK repair with DG. All specimens were tested to failure, and videos were recorded. The footprint area, tendon thickness, load to create 3-mm gap formation, failure load, failure modes, and stiffness were recorded and compared. Data were recorded as mean ± SD.Results:The mean load to create a 3-mm gap in both the control group (206.8 ± 55.7 N) and TFBC group (208.9 ± 39.1 N) was significantly higher than that in the DG group (157.7 ± 52.3 N) (P < .05 for all). The failure load of the control group (275.7 ± 75.0 N) and TFBC group (275.2 ± 52.5 N) was significantly higher compared with the DG group (201.5 ± 49.7 N) (P < .05 for both comparisons). The stiffness of the control group (26.4 ± 4.7 N/mm) was significantly higher than of the TFBC group (20.4 ± 4.4 N/mm) and the DG group (21.1 ± 4.8 N/mm) (P < .05 for both comparisons).Conclusion:TFBC augmentation showed superior biomechanical performance to DG augmentation in rotator cuff tears repaired using the DRSK technique, while there was no difference between the TFBC and control groups.Clinical Relevance:TFBC may help to reduce retear or gap formation after rotator cuff repair using the DRSK technique.