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PURPOSE: Screwed anterior lumbar interbody fusion (SALIF) alleviates the need for supplemental posterior fixation leading to reduction of perioperative morbidity. Specifically, elderly and multimorbid patients would benefit from shorter operative time and faster recovery but tend to have low bone mineral density (BMD). The current study aimed to compare loosening, defined as increase of ROM and NZ, of SALIF versus transforaminal lumbar interbody fusion (TLIF) under cyclic loading in cadaveric spines with reduced BMD. METHODS: Twelve human spines (L4-S2; 6 male 6 female donors; age 70.6 ± 19.6; trabecular BMD of L5 84.2 ± 24.4 mgHA/cm3, range 51-119 mgHA/cm3) were assigned to two groups. SALIF or TLIF were instrumented at L5/S1. Range of motion (ROM) and neutral zone (NZ) were assessed before and after axial cyclic loading (0-1150 N, 2000 cycles, 0.5 Hz) in flexion-extension (Flex-Ext), lateral bending, (LB), axial rotation (AR). RESULTS: ROM of the SALIF specimens increased significantly in all loading directions (p ≤ 0.041), except for left AR (p = 0.053), whereas for TLIF it increased significantly in left LB (p = 0.033) and Flex (p = 0.015). NZ of SALIF showed increase in Flex-Ext and LB, whereas NZ of TLIF did not increase significantly in any motion direction. CONCLUSIONS: Axial compression loading caused loosening of SALIF in Flex-Ext and LB, but not TLIF at L5/S1 in low BMD specimens. Nevertheless, Post-cyclic ROM and NZ of SALIF is comparable to TLIF. This suggests that, neither construct is optimal for the use in patients with reduced BMD.
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BACKGROUND AND PURPOSE: Recommendations regarding fragment-size-dependent screw fixation trajectory for coronal plane fractures of the posterior femoral condyles (Hoffa fractures) are lacking. The aim of this study was to compare the biomechanical properties of anteroposterior (AP) and crossed posteroanterior (PA) screw fixations across differently sized Hoffa fractures on human cadaveric femora. PATIENTS AND METHODS: 4 different sizes of lateral Hoffa fractures (n = 12 x 4) were created in 48 distal human femora according to the Letenneur classification: (i) type I, (ii) type IIa, (ii) type IIb, and (iv) type IIc. Based on bone mineral density (BMD), specimens were assigned to the 4 fracture clusters and each cluster was further assigned to fixation with either AP (n = 6) or crossed PA screws (n = 6) to ensure homogeneity of BMD values and comparability between the different test conditions. All specimens were biomechanically tested under progressively increasing cyclic loading until failure, capturing the interfragmentary movements via motion tracking. RESULTS: For Letenneur type I fractures, kilocycles to failure (mean difference [∆] 2.1, 95% confidence interval [CI] -1.3 to 5.5), failure load (∆ 105 N, CI -83 to 293), axial displacement (∆ 0.3 mm, CI -0.8 to 1.3), and fragment rotation (∆ 0.5°, CI -3.2 to 2.1) over 5.0 kilocycles did not differ significantly between the 2 screw trajectories. For each separate subtype of Letenneur type II fractures, fixation with crossed PA screws resulted in significantly higher kilocycles to failure (∆ 6.7, CI 3.3-10.1 to ∆ 8.9, CI 5.5-12.3) and failure load (∆ 275 N, CI 87-463 to ∆ 438, CI 250-626), as well as, less axial displacement from 3.0 kilocycles onwards (∆ 0.4°, CI 0.03-0.7 to ∆ 0.5°, CI 0.01-0.9) compared with AP screw fixation. CONCLUSION: Irrespective of the size of Letenneur type II fractures, crossed PA screw fixation provided greater biomechanical stability than AP-configured screws, whereas both screw fixation techniques demonstrated comparable biomechanical competence for Letenneur type I fractures. Fragment-size-dependent treatment strategies might be helpful to determine not only the screw configuration but also the surgical approach.
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Tornillos Óseos , Cadáver , Fracturas del Fémur , Fijación Interna de Fracturas , Humanos , Fijación Interna de Fracturas/métodos , Fijación Interna de Fracturas/instrumentación , Fenómenos Biomecánicos , Fracturas del Fémur/cirugía , Anciano , Femenino , Masculino , Densidad Ósea , Persona de Mediana Edad , Anciano de 80 o más Años , Estudios de CohortesRESUMEN
PURPOSE: Recently, a new dynamic high-strength suture (DC) was introduced, also available in tape form (DT), featuring a salt-infused silicone core attracting water in a fluid environment to preserve tissue approximation. The aims of this study were to (1) assess the influence of securing throw number on knot security of two double-stranded knot configurations (Cow-hitch and Nice-knot) tied with either dynamic (DC and DT) or conventional (FW and ST) high-strength sutures and tapes, and (2) compare the ultimate force and knot slippage of the novel dynamic versus conventional sutures and tapes when used with their minimal number of needed securing throws. METHODS: Seven specimens of each FW, ST, DC and DT were considered for tying with Cow-hitch or Nice-knots. The base of these Cow-hitch and Nice-knots was secured with surgeons` knots using 1-3 alternating throws. Tensile tests were conducted under physiologic conditions to evaluate knot slippage, ultimate force at rupture, and minimum number of throws ensuring 100% knot security. RESULTS: For both Cow-hitch and Nice-knots, 100% security was achieved with 2 securing throws for DC, DT, ST, and with 3 securing throws for FW. With these minimum numbers of securing throws, ultimate force was significantly higher for Nice-knots versus Cow-hitch tied with DT (p = 0.001) and slippage was significantly less with Nice-knots versus Cow-hitch tied with DC (p = 0.019). CONCLUSIONS: The minimum number of securing throws required to achieve 100% security was 2 with DC, DT and ST for both Cow-hitch and Nice-knots configurations, in contrast to FW where 3 securing throws were needed. With these minimum numbers of securing throws, Nice-knots were associated with significantly higher ultimate forces when using DT and lower slippage with DC versus Cow-hitch knots.
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Background and Objectives: Despite the established role of subtalar joint arthrodesis (SJA) for treatment of subtalar osteoarthritis, achieving bone union remains challenging, with up to 46% non-union rates. Adequate compression and stable fixation are crucial for successful outcomes, with internal screw fixation being the gold standard for SJA. The delta configuration, featuring highly divergent screws, offers stability, however, it can result in hardware irritation in 20-30% of patients. Solutions to solve this complication include cannulated compression screw (CCS) countersinking or cannulated compression headless screw (CCHS) application. The aim of this biomechanical study was to investigate the stability of a delta configuration for SJA utilizing either a combination of a posterior CCHS and an anterior CCS or a standard two-CCS combination. Materials and Methods: Twelve paired human cadaveric lower legs were assigned pairwise to two groups for SJA using either two CCSs (Group 1) or one posterior CCHS and one anterior CCS (Group 2). All specimens were tested under progressively increasing cyclic loading to failure, with monitoring of the talocalcaneal movements via motion tracking. Results: Initial stiffness did not differ significantly between the groups, p = 0.949. Talocalcaneal movements in terms of varus-valgus deformation and internal-external rotation were significantly bigger in Group 1 versus Group 2, p ≤ 0.026. Number of cycles until reaching 5° varus-valgus deformation was significantly higher in Group 2 versus Group 1, p = 0.029. Conclusions: A delta-configuration SJA utilizing a posterior CCHS and an anterior CCS is biomechanically superior versus a standard configuration with two CCSs. Clinically, the use of a posterior CCHS could prevent protrusion of the hardware in the heel, while an anterior CCS could facilitate less surgical time and thus less complication rates.
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Artrodesis , Tornillos Óseos , Cadáver , Articulación Talocalcánea , Humanos , Artrodesis/métodos , Artrodesis/instrumentación , Articulación Talocalcánea/cirugía , Fenómenos Biomecánicos , Masculino , Femenino , Anciano , Osteoartritis/cirugía , Persona de Mediana EdadRESUMEN
PURPOSE: Due to the increase in life expectancy and high-energy traumas, anterior column acetabular fractures (ACFs) are also increasing. While open reduction and internal fixation (ORIF) is still the standard surgical procedure, minimally invasive, percutaneous fixation of osteoporotic acetabulum fractures (AF) are growing in popularity. The aim of this biomechanical study was to evaluate the biomechanical competence following antegrade fixation with a standard screw versus a cannulated compression headless screw. METHODS: Eight anatomical osteoporotic composite pelvises were given an anterior column fracture. Two groups of eight specimens each (n = 8) for fixation with either a 6.5 mm cannulated compression headless screw in group Anterior Acetabulum Canulated Compression Headless Screw (AACCH), or with a 6.5 mm partially threaded cannulated screw in group Anterior Acetabulum Standard Screw (AASS) where compared. Each specimen was biomechanically loaded cyclically at a rate of 2 Hz with monotonically increasing compressive load until failure. Motions were assessed by means of optical motion tracking. RESULTS: Initial construct stiffness trended higher in group AACCH at 152.4 ± 23.1 N/mm compared to group AASS at 118.5 ± 34.3 N/mm, p = 0.051. Numbers of cycles and corresponding peak load at failure, were significantly higher in group AACCH at 6734 ± 1669 cycles and 873.4 ± 166.9 N versus group AASS at 4440 ± 2063 cycles and 644.0 ± 206.3 N, p = 0.041. Failure modes were breakout of the screws around the proximal entry point. CONCLUSION: From a biomechanical perspective, group AACCH was associated with superior biomechanical competence compared to standard partially threaded cannulated screws and could therefore be considered as valid alternative for fixation of anterior acetabulum fractures.
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Acetábulo , Tornillos Óseos , Fijación Interna de Fracturas , Acetábulo/cirugía , Acetábulo/lesiones , Humanos , Fijación Interna de Fracturas/métodos , Fijación Interna de Fracturas/instrumentación , Fenómenos Biomecánicos , Fracturas Óseas/cirugía , Osteoporosis/cirugía , Osteoporosis/fisiopatología , Osteoporosis/complicacionesRESUMEN
BACKGROUND: Early mobilization after tendon surgery is crucial to avoid commonly observed postoperative soft tissue adhesions. Recently, a new suture was introduced (DYNACORD; DC) with a salt-infused silicone core designed to minimize laxity and preserve consistent tissue approximation in order to avoid gap formation and allow early mobilization. AIMS: To compare the biomechanical competence of DC against a conventional high strength suture (FiberWire; FW) in a human cadaveric tendon transfer model with an early rehabilitation protocol. METHODS: Sixteen tendon transfers (flexor digitorum superficialis (FDS) IV to flexor pollicis longus (FPL)) were performed in 8 pairs human cadaveric forearms using either DC or FW. Markings were set 0.8 cm proximally and 0.7 cm distally to the level of the interweaving zone of the transfer. All specimens underwent repetitive thumb flexion against resistance in 9 intermittent series of 300 cycles each, simulating an aggressive postoperative rehabilitation protocol. After each series, the distance of the proximal marker to the interweaving zone (proximal), the length of the interweaving zone (intermediate) and the distance of the distal marker to the interweaving zone (distal) were measured. RESULTS: Pooled data over all nine series, normalized to the immediate postoperative status, demonstrated no significant differences between FW and DC (p ≥ 0.355) for the proximal and distal markers. However, at the intermediate zone, DC was associated with significant length shortening (p < 0.001) compared to FW without significant length changes (p = 0.351). Load to catastrophic failure demonstrated significant higher forces in FW (p = 0.011). Nevertheless, due to failure mainly proximal or distal of the transfer zone, these loads are not informative. CONCLUSION: From a biomechanical perspective, DC preserved tissue approximation and might be considered as a valid alternative to conventional high-strength sutures in tendon transfer surgery. DC might allow for a shorter interweaving zone and a more aggressive early postoperative rehabilitation program, possibly avoiding commonly observed postoperative soft tissue adhesions and stiffness.
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Cadáver , Suturas , Transferencia Tendinosa , Humanos , Transferencia Tendinosa/métodos , Fenómenos Biomecánicos , Extremidad Superior/cirugía , Masculino , Técnicas de Sutura , Anciano , FemeninoRESUMEN
BACKGROUND: Pressure distribution in the ankle joint is known to be dependent on various factors, including hindfoot alignment. We seek to evaluate how hindfoot alignment affects contact pressures in the ankle joint in the setting of supination external rotation (SER) type ankle fractures. METHODS: SER fractures were created in 10 human cadaver lower extremity specimens, simulating progressive stages of injury: without fracture (step 0), SER fracture and intact deltoid ligament (step 1), superficial deltoid ligament disruption (step 2), and deep deltoid ligament disruption (step 3). At each step, varus and valgus alignment was simulated by displacing the calcaneal tuberosity 7 mm medial or lateral. Each limb was axially loaded following each osteotomy at a static load of 350 N. The center of force (COF), contact area (CA), and peak contact pressure (PP) under load were measured, and radiographs of the ankle mortise were taken to analyze the medial clear space (MCS) and talar tilt (TT). RESULTS: The COF (5.3 mm, P = .030) and the CA (-188.4 mm2, P = .015) changed in step 3 in the valgus hindfoot alignment compared to baseline parameters, indicating the importance of deep deltoid ligament integrity in maintaining normal ankle joint contact stress in the valgus hindfoot. These changes were not seen in the setting of varus alignment (COF: 2.3 mm, P = .059; CA -121 mm2, P = .133). PP were found to not change significantly in either varus or valgus (varus: -4.9 N, P = .132; valgus: -4 N, P = .464).The MCS demonstrated widening in step 3 compared to step 2 (0.7 mm, P = .020) in both varus and valgus hindfoot. The TT increased significantly in step 3 in the valgus hindfoot (2.8 degrees, P = .020) compared to step 0. CONCLUSION: SER-IV fractures with valgus hindfoot alignment showed significant changes in pressure distribution and radiographic parameters when compared to SER-IV fractures with varus hindfoot alignment. CLINICAL RELEVANCE: Based on this cadaver modeling study, patients with SERIV fracture with varus hindfoot alignment and complete deltoid ligament lesion may not need fracture fixation, whereas those with valgus hindfoot alignment likely need fracture fixation.
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Fracturas de Tobillo , Cadáver , Supinación , Humanos , Supinación/fisiología , Fracturas de Tobillo/cirugía , Fracturas de Tobillo/fisiopatología , Fracturas de Tobillo/diagnóstico por imagen , Rotación , Fenómenos Biomecánicos , Articulación del Tobillo/fisiopatología , Ligamentos Articulares/fisiopatología , Ligamentos Articulares/diagnóstico por imagen , Ligamentos Articulares/lesiones , Soporte de Peso/fisiología , MasculinoRESUMEN
High-resolution peripheral quantitative computed tomography (HR-pQCT) based micro-finite element (µFE) analysis allows accurate prediction of stiffness and ultimate load of standardised (â¼1 cm) distal radius and tibia sections. An alternative homogenized finite element method (hFE) was recently validated to compute the ultimate load of larger (â¼2 cm) distal radius sections that include Colles' fracture sites. Since the mechanical integrity of the weight-bearing distal tibia is gaining clinical interest, it has been shown that the same properties can be used to predict the strength of both distal segments of the radius and the tibia. Despite the capacity of hFE to predict structural properties of distal segments of the radius and the tibia, the limitations of such homogenization scheme remain unclear. Therefore, the objective of this study is to build a complete mechanical data set of the compressive behavior of distal segments of the tibia and to compare quantitatively the structural properties with the hFE predictions. As a further aim, it is intended to verify whether hFE is also able to capture the post-yield strain localisation or fracture zones in such a bone section, despite the absence of strain softening in the constitutive model. Twenty-five fresh-frozen distal parts of tibias of human donors were used in this study. Sections were cut corresponding to an in-house triple-stack protocol HR-pQCT scan, lapped, and scanned using micro computed tomography (µCT). The sections were tested in compression until failure, unloaded and scanned again in µCT. Volumetric bone mineral density (vBMD) and bone mineral content (BMC) were correlated to compression test results. hFE analysis was performed in order to compare computational predictions (stiffness, yield load and plastic deformation field pattern) with the compressive experiment. Namely, strain localization was assessed based on digital volume correlation (DVC) results and qualitatively compared to hFE predictions by comparing mid-slices patterns. Bone mineral content (BMC) showed a good correlation with stiffness (R2 = 0.92) and yield (R2 = 0.88). Structural parameters also showed good agreement between the experiment and hFE for both stiffness (R2 = 0.96, slope = 1.05 with 95 % CI [0.97, 1.14]) and yield (R2 = 0.95, slope = 1.04 [0.94, 1.13]). The qualitative comparison between hFE and DVC strain localization patterns allowed the classification of the samples into 3 categories: bad (15 sections), semi (8), and good agreement (2). The good correlations between BMC or hFE and experiment for structural parameters were similar to those obtained previously for the distal part of the radius. The failure zones determined by hFE corresponded to registration only in 8 % of the cases. We attribute these discrepancies to local elastic/plastic buckling effects that are not captured by the continuum-based FE approach exempt from strain softening. A way to improve strain localization hFE prediction would be to use longer distal segments with intact cortical shells, as done for the radius. To conclude, the used hFE scheme captures the elastic and yield response of the tibia sections reliably but not the subsequent failure process.
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INTRODUCTION: Treatment of both simple and complex patella fractures is a challenging clinical problem. Although tension band wiring has been the standard of care, it can be associated with high complication rates. The aim of this study was to investigate the biomechanical performance of recently developed lateral rim variable angle locking plates versus tension band wiring used for fixation of simple and complex patella fractures. MATERIALS AND METHODS: Sixteen pairs of human anatomical knees were used to simulate either two-part transverse simple AO/OTA 34-C1 or five-part complex AO/OTA 34-C3 patella fractures by means of osteotomies, with each fracture model created in eight pairs. The complex fracture pattern was characterized by a medial and a lateral proximal fragment, together with an inferomedial, an inferolateral, and an inferior (central distal) fragment mimicking comminution around the distal patellar pole. The specimens with simple fractures were pairwise assigned for fixation with either tension band wiring through two parallel cannulated screws or a lateral rim variable angle locking plate. The knees with complex fractures were pairwise treated with either tension band wiring through two parallel cannulated screws plus circumferential cerclage wiring or a lateral rim variable angle locking plate. Each specimen was tested over 5000 cycles by pulling on the quadriceps tendon, simulating active knee extension and passive knee flexion within the range of 90° flexion to full extension. Interfragmentary movements were captured via motion tracking. RESULTS: For both fracture types, the articular displacements measured between the proximal and distal fragments at the central patella aspect between 1000 and 5000 cycles, together with the relative rotations of these fragments around the mediolateral axis were all significantly smaller following the lateral rim variable angle locked plating compared with tension band wiring, p ≤ 0.01. CONCLUSIONS: From a biomechanical perspective, lateral rim variable angle locked plating of both simple and complex patella fractures provides superior construct stability versus tension band wiring under dynamic loading.
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Placas Óseas , Hilos Ortopédicos , Fijación Interna de Fracturas , Fracturas Óseas , Rótula , Humanos , Rótula/lesiones , Rótula/cirugía , Fenómenos Biomecánicos , Fijación Interna de Fracturas/métodos , Fijación Interna de Fracturas/instrumentación , Fracturas Óseas/cirugía , Cadáver , Anciano , Masculino , Femenino , Fractura de RótulaRESUMEN
PURPOSE: To investigate the forces on a medial collateral ligament (MCL) reconstruction (MCLR) relative to the valgus alignment of the knee. METHODS: Eight fresh-frozen human cadaveric knees were subjected to dynamic valgus loading at 400 N using a custom-made kinematics rig. After resection of the superficial medial collateral ligament, a single-bundle MCLR with a hamstring tendon autograft was performed. A medial opening wedge distal femoral osteotomy was performed and fixed with an external fixator to gradually adjust the alignment in 5° increments from 0° to 10° valgus. For each degree of valgus deformity, the resulting forces acting on the MCLR were measured through a force sensor and captured in 15° increments from 0° to 60° of knee flexion. RESULTS: Irrespective of the degree of knee flexion, increasing valgus malalignment resulted in significantly increased forces acting on the MCLR compared to neutral alignment (p < 0.05). Dynamic loading at 5° valgus resulted in increased forces on the MCLR at all flexion angles ranging between 16.2 N and 18.5 N (p < 0.05 from 0° to 30°; p < 0.01 from 45° to 60°). A 10° valgus malalignment further increased the forces on the MCLR at all flexion angles ranging between 29.4 N and 40.0 N (p < 0.01 from 0° to 45°, p < 0.05 at 60°). CONCLUSION: Valgus malalignment of the knee caused increased forces acting on the reconstructed MCL. In cases of chronic medial instabilities accompanied by a valgus deformity ≥ 5°, a realigning osteotomy should be considered concomitantly to the MCLR to protect the graft and potentially reduce graft failures. LEVEL OF EVIDENCE: Level III.
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Ligamentos Colaterales , Tendones Isquiotibiales , Humanos , Cadáver , Articulación de la Rodilla/cirugía , Fenómenos Biomecánicos , Ligamentos Colaterales/cirugíaRESUMEN
BACKGROUND: The current literature lacks recommendations regarding surgical approaches to best visualize and reduce Hoffa fractures. The aims of this study were to (1) define surgical corridors to the posterior portions of the lateral and medial femoral condyles and (2) compare the articular surface areas visible with different approaches. METHODS: Eight fresh-frozen human cadaveric knees (6 male and 2 female donors; mean age, 68.2 ± 10.2 years) underwent dissection simulating 6 surgical approaches to the distal femur. The visible articular surface areas for each approach were marked using an electrocautery device and subsequently analyzed using image-processing software. The labeled areas of each femoral condyle were statistically compared. RESULTS: At 30° of flexion, visualization of the posterior portions of the lateral and medial femoral condyles was not possible by lateral and medial parapatellar approaches, as only the anterior 29.4% ± 2.1% of the lateral femoral condyle and 25.6% ± 2.8% of the medial condyle were exposed. Visualization of the lateral femoral condyle was limited by the posterolateral ligamentous structures, hence a posterolateral approach only exposed its central (13.1% ± 1.3%) and posterior (12.4% ± 1.1%) portions. Posterolateral extension by an osteotomy of the lateral femoral epicondyle significantly improved the exposure to 53.4% ± 2.7% and, when combined with a Gerdy's tubercle osteotomy, to 70.9% ± 4.1% (p < 0.001). For the posteromedial approach, an arthrotomy between the anteromedial retinaculum and the superficial medial collateral ligament, and one between the posterior oblique ligament and the medial gastrocnemius tendon, allowed visualization of the central (13.5% ± 2.2%) and the posterior (14.6% ± 2.3%) portions of the medial femoral condyle, while a medial femoral epicondyle osteotomy significantly improved visualization to 66.1% ± 5.5% (p < 0.001). CONCLUSIONS: Visualization of the posterior portions of the femoral condyles is limited by the specific anatomy of each surgical corridor. Extension by osteotomy of the femoral epicondyles and Gerdy's tubercle significantly improved articular surface exposure of the femoral condyles. CLINICAL RELEVANCE: Knowledge of the surgical approach-specific visualization of the articular surface of the femoral condyles might be helpful to properly reduce small Hoffa fragments.
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Cadáver , Fracturas del Fémur , Humanos , Femenino , Masculino , Anciano , Fracturas del Fémur/cirugía , Articulación de la Rodilla/cirugía , Persona de Mediana Edad , Fémur/cirugía , Fémur/anatomía & histología , Anciano de 80 o más Años , Disección/métodosRESUMEN
BACKGROUND: Recently, a new generation of superior clavicle plates was developed featuring the variable-angle locking technology for enhanced screw positioning and a less prominent and optimized plate-to-bone fit design. On the other hand, minifragment plates in dual plating mode have demonstrated promising clinical results. The aim of the current study was to compare the biomechanical competence of single superior plating using the new-generation plate vs. dual plating using low-profile minifragment plates. METHODS: Sixteen paired human cadaveric clavicles were pairwise assigned to 2 groups for instrumentation with either a superior 2.7-mm variable-angle locking compression plate (group 1), or with one 2.5-mm anterior combined with one 2.0-mm superior matrix mandible plate (group 2). An unstable clavicle shaft fracture (AO/OTA 15.2C) was simulated by means of a 5-mm osteotomy gap. Specimens were cyclically tested to failure under craniocaudal cantilever bending, superimposed with bidirectional torsion around the shaft axis, and monitored via motion tracking. RESULTS: Initial construct stiffness was significantly higher in group 2 (9.28 ± 4.40 N/mm) compared to group 1 (3.68 ± 1.08 N/mm), P = .003. The amplitudes of interfragmentary motions in terms of axial and shear displacement, fracture gap opening and torsion, over the course of 12,500 cycles were significantly higher in group 1 compared to group 2, P ≤ .038. Cycles to 2 mm shear displacement were significantly lower in group 1 (22,792 ± 4346) compared to group 2 (27,437 ± 1877), P = .047. CONCLUSION: From a biomechanical perspective, low-profile 2.5/2.0-mm dual plates could be considered as a useful alternative for diaphyseal clavicle fracture fixation, especially in less common unstable fracture configurations.
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Clavícula , Fracturas Óseas , Humanos , Clavícula/cirugía , Fenómenos Biomecánicos , Fracturas Óseas/cirugía , Fijación Interna de Fracturas/métodos , Tornillos Óseos , Placas ÓseasRESUMEN
Dual plating of comminuted distal femoral fractures allows for early patient mobilization. An additional helically shaped medial plate avoids the medial vital structures of the thigh. The aim of this study is to investigate the biomechanical competence of an augmented lateral locking compression plate distal femur (LCP-DF) using an additional straight versus a helically shaped medial LCP of the same length. Ten pairs of human cadaveric femora were instrumented with a lateral anatomical 15-hole LCP-DF. Following, they were pairwise instrumented with either an additional medial straight 14-hole LCP (group 1) or a 90°-helical shape LCP (group 2). All specimens were biomechanically tested under quasi-static and progressively increasing combined cyclic axial and torsional loading until failure. Initial interfragmentary axial displacement and flexion under static compression were significantly smaller in group 1 (0.11 ± 0.12 mm and 0.21 ± 0.10°) versus group 2 (0.31 ± 0.14 mm and 0.68 ± 0.16°), p ≤ 0.007. Initial varus deformation under static compression remained not significantly different between group 1 (0.57 ± 0.23°) and group 2 (0.75 ± 0.34°), p = 0.085. Flexion movements during dynamic loading were significantly bigger in group 2 (2.51 ± 0.54°) versus group 1 (1.63 ± 1.28°), p = 0.015; however, no significant differences were observed in terms of varus, internal rotation, and axial and shear displacements between the groups, p ≥ 0.204. Cycles to failure and load at failure were higher in group 2 (25,172 ± 6376 and 3017 ± 638 N) compared to group 1 (22,277 ± 4576 and 2728 ± 458 N) with no significant differences between them, p = 0.195. From a biomechanical perspective, helical double plating may be considered a useful alternative to straight double plating, demonstrating ameliorated damping capacities during flexion deformation and safer application as the medial neurovascular structures of the thigh are avoided.
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Fracturas del Fémur , Fijación Interna de Fracturas , Humanos , Fenómenos Biomecánicos , Fémur/cirugía , Placas Óseas , Extremidad InferiorRESUMEN
PURPOSE: The number of seven required throws per knot was previously reported as providing sufficient security against slippage. A novel high-strength suture featuring dynamic tightening may allow for throw number reduction without compromising stability. The aims of this study were to (1) investigate the influence of the throw number and the effect of different ambient conditions on the knot security of two different high-strength sutures, and (2) compare their biomechanical competence. METHODS: Two sutures (FiberWire (FW) and DynaCord (DC)) were considered for preparing alternating surgical knots. The specimens were stratified for exposure to different media during biomechanical testing-namely air (dry), saline solution (wet), and fat (fatty-wet). A monotonic tensile ramp loading to failure was applied in each test run. For each suture and ambient condition, seven specimens with three to seven throws each were tested (n = 7), evaluating their slippage and ultimate force to failure. The minimum number of throws preventing suture unraveling was determined for each suture type and condition. RESULTS: For each suture type and condition, failure occurred via rupture in all specimens for the following minimum number of throws: FW-dry-7, wet-7, fatty-wet-7; DC-dry-6, wet-4, fatty-wet-5. When applying seven throws, FW demonstrated significantly larger slippage (6.5 ± 2.2 mm) versus DC (3.5 ± 0.4 mm) in wet (p = 0.004) but not in dry and fatty-wet conditions (p ≥ 0.313). CONCLUSIONS: The lower number of throws providing knot security of DC versus FW in the more realistic wet and fatty-wet conditions indicates that the novel DC suture may allow to decrease the foreign body volume and save surgical time without compromising the biomechanical competence.
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Técnicas de Sutura , Suturas , Humanos , Ensayo de Materiales , Resistencia a la Tracción , Rotura , Técnicas de Sutura/efectos adversosRESUMEN
OBJECTIVES: As currently there is no existing biomechanical work on the topic of interest, the aim of the current study was to investigate the effect of cerclage banding distally to an intraoperatively occurring proximal periprosthetic femoral clamshell fracture versus a non-fractured femur after total hip arthroplasty. METHODS: A diaphyseal anchoring stem was implanted in twenty paired human cadaveric femora, assigned to a treatment and a control group. In the treatment group, each specimen was fitted with a cerclage band placed 3 mm distally to a clamshell fracture, created with an extent of 40% of the anchoring length of the stem. The resulting fragment was not treated further. The contralateral specimens were left with the stems without further fracture creation or treatment. All constructs were tested under progressively increasing cyclic axial loading until failure. Relative bone-implant movements were monitored by motion tracking. RESULTS: Number of cycles and the corresponding load at stem loosening, defined as 1 mm displacement of the stem along the shaft axis, were 31,417 ± 8870 and 3641.7 ± 887 N in the control group, and 26,944 ± 11,706 and 3194.4 ± 1170.6 N in the treatment group, respectively, with no significant differences between them, p = 0.106. CONCLUSION: From a biomechanical perspective, cerclage banding distally to an intraoperative clamshell fracture with an extent of 40% of the anchoring length of the stem demonstrated comparable resistance against hip stem loosening versus a non-fractured femur. It may therefore represent a valid treatment option to restore the full axial stability of a diaphyseal anchoring stem. In addition, it may be considered to keep the medial wall fragment unfixed, thus saving operative time and minimizing associated risks.
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Background and Objectives: The surgical treatment of proximal humeral shaft fractures usually considers application of either long straight plates or intramedullary nails. By being able to spare the rotator cuff and avoid the radial nerve distally, the implementation of helical plates might overcome the downsides of common fixation methods. The aims of the current study were (1) to explore the biomechanical competence of different plate designs and (2) to compare their performance versus the alternative treatment option of using intramedullary nails. Materials and Methods: Twenty-four artificial humeri were assigned to the following four groups for simulation of an unstable proximal humeral shaft fracture and instrumentation: Group 1 (Straight-PHILOS), Group 2 (MULTILOC-Nail), Group 3 (45°-Helical-PHILOS), and Group 4 (90°-Helical-PHILOS). All specimens underwent non-destructive, quasi-static biomechanical testing under loading in axial compression, torsion in internal/external rotation, and pure bending in four directions, accompanied by motion tracking. Results: Axial stiffness/displacement in Group 2 was significantly higher/smaller than in all other groups (p ≤ 0.010). Torsional displacement in Group 2 was significantly bigger than in all other groups (p ≤ 0.017). Significantly smaller coronal plane displacement was identified in Group 2 versus all other groups (p < 0.001) and in Group 4 versus Group 1 (p = 0.022). Significantly bigger sagittal plane displacement was detected in Group 4 versus all other groups (p ≤ 0.024) and in Group 1 versus Group 2 (p < 0.001). Conclusions: Intramedullary nails demonstrated higher axial stiffness and smaller axial interfragmentary movements compared with all investigated plate designs. However, they were associated with bigger torsional movements at the fracture site. Although 90°-helical plates revealed bigger interfragmentary movements in the sagittal plane, they demonstrated improved resistance against displacements in the coronal plane when compared with straight lateral plates. In addition, 45°-helical plates manifested similar biomechanical competence to straight plates and may be considered a valid alternative to the latter from a biomechanical standpoint.
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Fijación Intramedular de Fracturas , Humanos , Fijación Intramedular de Fracturas/métodos , Clavos Ortopédicos , Fenómenos Biomecánicos , Fijación Interna de Fracturas , Húmero , Placas ÓseasRESUMEN
BACKGROUND: Distal femoral fractures are commonly treated with lateral straight plates. However, the lateral approach may not always be desirable, and 180°-helical plates may be an alternative. AIM: To investigate the biomechanical competence of 180°-helical plating versus standard straight lateral plating of unstable fractures at the distal femur. METHODS: Twelve left artificial femora were instrumented with a 15-hole Locking Compression Plate-Distal Femur, using either 180°-helical plates (group 1) or conventional straight lateral plates (group 2). An unstable distal femoral fracture AO/OTA 33-A3.3 was simulated. All specimens were biomechanically tested under quasi-static and progressively increasing combined cyclic axial and torsional loading in internal rotation until failure. FINDINGS: Initial axial stiffness (N/mm) was significantly higher in group 1 (185.6 ± 50.1) compared to group 2 (56.0 ± 14.4), p < 0.001. Group 1 demonstrated significantly higher initial interfragmentary flexion (°) and significantly lower initial varus/valgus deformation (°) under 500 N static axial compression versus group 2 (2.76 ± 1.02 versus 0.87 ± 0.77 and 4.08 ± 1.49 versus 6.60 ± 0.47), p ≤ 0.005. Shear displacement (mm) under 6 Nm static torsion was significantly higher in group 1 versus group 2 in both internal (1.23 ± 0.28 versus 0.40 ± 0.42) and external (1.21 ± 0.40 versus 0.57 ± 0.33) rotation, p ≤ 0.013. Cycles to failure and failure load (N) (clinical/catastrophic) were significantly higher in group 1 (12,484 ± 2116/13,752 ± 1518 and 1748.4 ± 211.6/1875.2 ± 151.8) compared to group 2 (7853 ± 1262/9727 ± 836 and 1285.3 ± 126.2/1472.7 ± 83.6), p ≤ 0.001. INTERPRETATION: Although 180°-helical plating using a pre-contoured standard straight lateral plate was associated with higher shear and flexion movements, it demonstrated improved initial axial stability and resistance against varus/valgus deformation compared to straight lateral plating. Moreover, the helical plates were associated with significantly higher endurance to failure. From a biomechanical perspective, 180°-helical plating may be considered as a valuable alternative to standard straight lateral plating of unstable distal femoral fractures.
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Fracturas Femorales Distales , Fracturas del Fémur , Humanos , Fracturas del Fémur/cirugía , Fenómenos Biomecánicos , Fijación Interna de Fracturas , Placas ÓseasRESUMEN
Background and Objectives: Unstable proximal humerus fractures (PHFs) with metaphyseal defects-weakening the osteosynthesis construct-are challenging to treat. A new augmentation technique of plated complex PHFs with metaphyseal defects was recently introduced in the clinical practice. This biomechanical study aimed to analyze the stability of plated unstable PHFs augmented via implementation of this technique versus no augmentation. Materials and Methods: Three-part AO/OTA 11-B1.1 unstable PHFs with metaphyseal defects were created in sixteen paired human cadaveric humeri (average donor age 76 years, range 66-92 years), pairwise assigned to two groups for locked plate fixation with identical implant configuration. In one of the groups, six-milliliter polymethylmethacrylate bone cement with medium viscosity (seven minutes after mixing) was placed manually through the lateral window in the defect of the humerus head after its anatomical reduction to the shaft and prior to the anatomical reduction of the greater tuberosity fragment. All specimens were tested biomechanically in a 25° adduction, applying progressively increasing cyclic loading at 2 Hz until failure. Interfragmentary movements were monitored by motion tracking and X-ray imaging. Results: Initial stiffness was not significantly different between the groups, p = 0.467. Varus deformation of the humerus head fragment, fracture displacement at the medial humerus head aspect, and proximal screw migration and cut-out were significantly smaller in the augmented group after 2000, 4000, 6000, 8000 and 10,000 cycles, p ≤ 0.019. Cycles to 5° varus deformation of the humerus head fragment-set as a clinically relevant failure criterion-and failure load were significantly higher in the augmented group, p = 0.018. Conclusions: From a biomechanical standpoint, augmentation with polymethylmethacrylate bone cement placed in the metaphyseal humerus head defect of plated unstable PHFs considerably enhances fixation stability and can reduce the risk of postoperative complications.
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BACKROUND: The beneficial effects of unrestricted postoperative full weight bearing for elderly patients suffering hip fractures have been demonstrated. However, there is still existing disagreement regarding acetabular fractures.The aim of this biomechanical study was to evaluate the initial load bearing capabilities of different fixation constructs of anterior column fractures (ACFs) in osteoporotic bone. METHODS: Artificial pelvises with ACFs were assigned to three groups (n = 8) and fixed with either a 7.3 mm partially threaded antegrade cannulated screw (group AASS), an anteriorly placed 3.5 mm plate (group AAPF), or a press-fit acetabular cup with screw augmentation (group AACF). All specimens underwent ramped loading from 20 N preload to 200 N at a rate of 18 N/s, followed by progressively increasing cyclic testing at 2 Hz until failure performed at a rate of 0.05 N/cycle. Relative displacements of the bone fragments were monitored by motion tracking. FINDINGS: Initial stiffness (N/mm) was 118.5 ± 34.3 in group AASS, 100.4 ± 57.5 in group AAPF, and 92.9 ± 44.0 in group AACF, with no significant differences between the groups, p = 0.544. Cycles to failure were significantly higher in groups AACF (8364 ± 2243) and AAPF (7827 ± 2881) compared to group AASS (4440 ± 2063), p ≤ 0.041. INTERPRETATION: From a biomechanical perspective, the minimally invasive cup fixation with screw augmentation demonstrated comparable stability to plate osteosynthesis of ACFs in osteoporotic bone. The results of the present study do not allow to conclusively answer whether immediate full weight bearing following cup fixation shall be allowed. Given its similar performance to plate osteosynthesis, this remains rather an utopic wish and a more conservative approach deems more reasonable.
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Fracturas Óseas , Fracturas de Cadera , Osteoporosis , Fracturas de la Columna Vertebral , Humanos , Anciano , Acetábulo/cirugía , Estudios de Factibilidad , Fenómenos Biomecánicos , Fracturas Óseas/cirugía , Fijación Interna de Fracturas/métodos , Fracturas de Cadera/cirugía , Tornillos Óseos , Placas ÓseasRESUMEN
Background and purpose: Cannulated screws are standard implants for percutaneous fixa-tion of posterior pelvis ring injuries. The choice of whether to use these screws in combination with a washer is still undecided. The aim of this study was to evaluate the biomechanical competence of S1-S2 sacroiliac (SI) screw fixation with and without using a washer across three different screw designs. Material and Methods: Twenty-four composite pelvises were used and an SI joint injury type APC III according to the Young and Burgess classification was simulated. Fixation of the posterior pelvis ring was performed using either partially threaded short screws, fully threaded short screws, or fully threaded long transsacral screws. Biomechanical testing was performed under progressively increasing cyclic loading until failure, with monitoring of the intersegmental and bone-implant movements via motion tracking. Results: The number of cycles to failure and the corresponding load at failure (N) were significantly higher for the fully threaded short screws with a washer (3972 ± 600/398.6 ± 30.0) versus its counterpart without a washer (2993 ± 527/349.7 ± 26.4), p = 0.026. In contrast, these two parameters did not reveal any significant differences when comparing fixations with and without a washer using either partially threaded short of fully threaded long transsacral screws, p ≥ 0.359. Conclusions: From a biomechanical perspective, a washer could be optional when using partially threaded short or fully threaded long transsacral S1-S2 screws for treatment of posterior pelvis ring injuries in young trauma patients. Yet, the omission of the washer in fully threaded short screws could lead to a significant diminished biomechanical stability.