Locking Compression Plate Constructs Research Articles

Comparação biomecânica entre placa de TPLO modificada, placa bloqueada e construção placa-pino intramedular aplicadas medialmente em modelo de fratura proximal em tíbias sintéticas caninas

ABSTRACT The aim of this study was to develop a modified tibial plateau leveling osteotomy (TPLO) plate and to compare its biomechanical properties with a locking compression plate (LCP) and plate-rod constructs for the stabilization of experimentally induced gap fractures in canine synthetic tibias. The tibial models were assigned to either repair with a modified TPLO plate (Group 1), locking compression plate construct (Group 2), or plate-rod construct (Group 3). The specimens were loaded to failure in axial compression, three-point mediolateral and craniocaudal bending. There was no statistical difference between the three groups regarding stiffness (N/mm) and deformation (mm) in axial compression. The modified TPLO plate achieved load to failure similar to the plate-rod construct in craniocaudal bending. There was no significant difference between groups on mediolateral bending tests regarding load to failure and deformation. Furthermore, there was no significant difference in stiffness between groups 1 and 2. In conclusion, the modified TPLO plate had similar mechanical properties to LCP and plate-rod construct in the axial compression and bending tests. Nonetheless, clinical studies with a large population of dogs are required to determine the value of this new implant in proximal tibial fracture repair.

Evaluation of locking compression plate fixation of the distal phalanx to the hoof wall as a potential therapy for laminitis.

Surgical stabilisation of the distal phalanx (DP) is a potential therapeutic strategy for severe acute laminitis. To evaluate the effects of locking compression plate (LCP) fixation of the DP to the dorsal hoof wall. Ex vivo and in vivo experiments. A T-shaped LCP was applied to one limb per pair in six pairs of cadaver forelimbs subjected to a combination of thermally induced lamellar failure and vertical load to simulate severe acute laminitis. Standard radiographic measurements were used to compare DP displacement. The LCP was then applied to one forefoot in 12 healthy Standardbred horses either standing (n=6) or under general anaesthesia (n=6). Lameness was evaluated daily, then horses were euthanised (day 8) and lamellar tissue analysed using light microscopy, histomorphometery and molecular markers of apoptosis. In the cadaver limb model, LCP fixation prevented the significant changes in hoof-distal phalanx distance, coronary extensor process distance and sole depth that characterised DP displacement in untreated limbs (p < 0.05). Application of the construct in vivo was well tolerated with minimal lameness (10/12 horses were sound at the trot on day 8); however, histology revealed dorsal lamellar pathology consistent with laminitis, but with extensive keratinocyte apoptosis. Adjacent to the LCP, caspase-3 positive cell counts were approximately 20-fold higher than control (p < 0.001). Pathology was evaluated at a single time point. Microvascular perfusion was not evaluated. Rigid fixation of the DP to the hoof capsule was achieved with the LCP construct in a cadaver limb laminitis model. In live horses, LCP fixation caused regional lamellar pathology with extensive apoptosis, likely due to disturbed lamellar microvascular perfusion and/or mechanostasis. Understanding these mechanisms is critical for refinement of the technique in order to avoid iatrogenic lamellar damage.

Osteosynthesis of diaphyseal tibia fracture with locking compression plates: A numerical investigation using Taguchi and ANOVA.

Performance of the locking compression plate (LCP) is a multifactorial function. The control parameters of plating, such as geometries, material properties, and physical constraints of the LCP components, affect basic functions associated with the bone fixation, including the extent of stress shielding and subsequent bone remodeling, strength and stability of the bone-LCP construct, and performance of secondary bone healing. The main objectives of this research were as follows: (1) to find the appropriate values of control parameters of an LCP construct to achieve the optimized performance throughout bone healing; and (2) to unravel relationships between LCP parameters and the LCP's performance. Different values for the plate/screw modulus of elasticity (E), plate width (W), plate thickness (T), screw diameter (D), bone-plate offset (O), and screw configuration (C), as six control parameters, were considered at five different levels. Taguchi method was adopted to create trial combinations of control parameters and determining the best set of parameters, which can optimize the overall performance of the LCP. All design cases were analyzed using the finite element method. The optimal set of control parameters consisting of 150 GPa, 12 mm, 4 mm, 5.5 mm, 2 mm, and 123,678 were determined for E, W, T, D, O, and C, respectively. Furthermore, ANOVA was used to rank the most influential parameters on each function of the LCP fixation. In the overall performance of the LCP fixation, E, D, T, C, W, and O showed a contribution percentage of 46%, 22%, 10%, 11%, 8%, and 3%, respectively.

Evaluation of a Feline Bone Surrogate and In Vitro Mechanical Comparison of Small Interlocking Nail Systems in Mediolateral Bending.

The aim of this study was to (1) evaluate bending structural properties of a machined short fibre epoxy (SFE) feline bone surrogate (FBS), (2) compare the bending behaviour of small angle-stable interlocking nails (I-Loc; Targon) and locking compression plates (LCP) and (3) evaluate the effect of implant removal on FBS bending strength. Part 1: Feline cadaveric femurs (n = 10) and FBS (n = 4) underwent cyclic four-point bending and load to failure. Part 2: Fracture gap FBS constructs (n = 4/group) were stabilized in a bridging fashion with either I-Loc 3 and 4, Targon 2.5 and 3.0, LCP 2.0 and 2.4, then cyclically bent. Part 3: Intact FBS with pilot holes, simulating explantation, (n = 4/group) underwent destructive bending tests. Bending compliance, angular deformation and failure moment (FM) were statistically compared (p < 0.05). Native bone and FBS were similar for all outcome measures (p > 0.05). The smallest and largest bending compliance and angular deformation were seen in the I-Loc 4 and LCP 2.0 respectively (p < 0.05). While explanted Targon FBS had the lowest FM (p < 0.05), I-Loc and LCP constructs FM were not different (p > 0.05). The similar bending properties of short fibre epoxy made FBS and native feline femurs suggest that this model could be used for mechanical testing of implants designed for feline long bone osteosynthesis. The I-Loc constructs smaller angular deformation which also suggests that these implants represent a valid alternative to size-matched Targon and LCP for feline fracture osteosynthesis. The significantly lower FM of explanted Targon may increase the risk of secondary fracture following implant removal.

Biomechanical comparison of locking compression plate fixation and a novel pedicle screw external fixation to repair equine mandibular fractures.

To determine the biomechanical properties of pedicle screw external fixation (PDW) for equine mandibular fracture repair and compare PDW to locking compression plates (LCP). Cadaveric study. Sixteen adult equine mandibles. Four mandibles were kept intact, while 12 were osteotomized and stabilized with the LCP or PDW construct (6 mandibles/group). Failure, stiffness, and yield were calculated from quasi-static ramp to failure and compared with previous analysis of mandibular fracture constructs. Tooth root involvement and method of failure were determined from radiographs and videos. Locking compression plate constructs achieved greater stiffness and load at failure (4656 ± 577 N-m/radian, 558 ± 27 N-m P < .05) compared with PDW constructs (2626 ± 127 N-m/radian, 315 ± 48 N-m). Yield did not differ between types of fixation (369 ± 57 N-m, 193 ± 35 N-m, P = .145). Tooth involvement was noted in two LCP constructs with failure via bone fracture. Pedicle screw external fixation constructs failed via wire unraveling and screw bending. Locking compression plate fixation increased stiffness and failure of constructs but did not influence yield. It also increased the risk to tooth root involvement relative to fixation with PDW. Compared with another study, PDW offered stiffness and failure similar to an intraoral splint with interdental wires, external fixator (EF), and external fixator with wires (EFW) and yield similar to an EF, an EFW, and a dynamic compression plate. Pedicle screw external fixation offers biomechanical stability comparable to other relevant mandibular fixation techniques and reduces the risk of tooth root damage compared with LCP fixation.

Biomechanical Comparison of Two Locking Plate Constructs for the Stabilization of Feline Tibial Fractures.

The aim of this study was to compare the biomechanical characteristics of locking compression plate (LCP) and conical coupling plate (CCP) constructs for the stabilization of experimentally induced gap fractures in cat tibiae. Pelvic limbs were harvested from eight cat cadavers. Paired tibiae were stripped of all soft tissues, and randomly assigned to the LCP or CCP stabilization group. An eight-hole 2.7 mm LCP or a six-hole 2.5 mm CCP was applied to the medial surface of each tibia. A 1-cm segment of the tibia was excised centrally beneath the plate. The specimens were potted, then tested in non-destructive four-point craniocaudal and mediolateral bending, followed by non-destructive axial compression. Each construct was subsequently loaded to failure in axial compression. Bending and axial stiffness, yield load and failure load were calculated for each specimen. The LCP constructs were significantly stiffer than the CCP constructs when subjected to non-destructive bending and axial loading. Craniocaudal bending stiffness was significantly greater than mediolateral bending stiffness for both constructs. Yield load and failure load were significantly greater for LCP constructs compared with CCP constructs. LCP may be a more suitable implant for stabilizing complex diaphyseal tibial fractures in cats. Additional supplemental fixation should be considered when using CCP to stabilize unreconstructed diaphyseal tibial fractures in cats. Further clinical investigation of both implants is recommended.

Biomechanical Comparison of Locking Plate and Cancellous Screw Techniques in Medial Malleolar Fractures: A Finite Element Analysis

As the commonly used fixation strategy of medial malleolar fractures, cancellous screws (CS) have been challenged for instability, bone destruction, and metal prominence. It is still unclear whether a locking compression plate (LCP) is a better choice in such fractures. Our purpose is to compare the mechanical efficacy of LCP with traditional 4.0-mm CS for transverse, oblique, and vertical medial malleolar fractures by using finite element analysis. In this study, 3-dimensional models of the distal tibia were reconstructed from a computed tomography scan of a young healthy male adult. Conditions included 3 fracture lines at 30°, 60°, and 90°; 2 groups of fixation (LCP and CS); and 3 adduction loads of 300, 500, and 700 N applied to the medial malleolar joint surface. The proximal part of the tibia was fixed for all degrees of freedom. The fracture displacements of the LCP were smaller than those of CS (p < .05). The stiffness of the LCP constructs was much higher than that of the CS constructs, especially in the 90° fractures (490.3 versus 163.6 N/mm). The mean stress around the CS was higher than that in LCP for 60° and 90° fractures, but there was no difference for 30°. Maximal bone stress increased (19.84 to 50.86 MPa) and concentrated on cortical bone in LCP, whereas it concentrated on cancellous bone in CS. The results showed that LCP could improve stability, preventing bone destruction in oblique and vertical medial malleolar fractures. However, in transverse fractures, CS provides sufficient stability, with no need to use LCP.

Drilling the near cortex with elongated figure-of-8 holes to reduce the stiffness of a locking compression plate construct.

To compare the stiffness of locking compression plate (LCP) constructs with or without drilling the near cortex with elongated figure-of-8 holes. 24 synthetic bones were sawn to create a 10-mm gap and were fixed with a 9-hole 4.5-mm narrow LCP. In 12 bones, the near cortex of the adjacent holes to the LCP holes was drilled to create elongated figure-of-8 holes before screw insertion. The stiffness of LCP constructs under axial loading or 4-point bending was assessed by (1) dynamic quasi-physiological testing for fatigue strength, (2) quasi-static testing for stiffness, and (3) testing for absolute strength to failure. None of the 24 constructs had subcatastrophic or catastrophic failure after 10 000 cycles of fatigue loading (p=1.000). The axial stiffness reduced by 16% from 613±62 to 517±44 N/mm (p=0.012) in the case group, whereas the bending stiffness was 16±1 Nm2 in both groups (p=1.000). The maximum axial load to catastrophic failure was 1596±84 N for the control group and 1627±48 N for the case group (p=0.486), whereas the maximum bending moment to catastrophic failure was 79±12 and 80±10 Nm, respectively (p=0.919). Drilling the near cortex with elongated figure-of-8 holes reduces the axial stiffness of the LCP construct, without compromising its bending stiffness or strength.

In Vitro Biomechanical Comparison of 3.5 String of Pearl Plate Fixation to 3.5 Locking Compression Plate Fixation in a Canine Fracture Gap Model

ObjectiveTo compare the 3.5 string of pearls (SOP) plate with a 3.5 mm locking compression plate (LCP) using a fracture model in static loading and cyclic fatigue testing.Study DesignIn vitro biomechanical testing of paired tibias with a mid‐diaphyseal ostectomy, stabilized by 1 of 2 locking systems.Sample PopulationCadaveric canine tibiae (n = 24 pairs).MethodsTibias were randomly divided into 4 equal groups: (1) 4‐point bending single cycle to failure, (2) 4‐point bending cyclic fatigue, (3) torsion single cycle to failure, and (4) torsion cyclic fatigue. Randomly assigned SOP and LCP bridged a 20 mm mid‐diaphyseal ostectomy. Mean test variables values for each method were compared using a paired t‐test within each group with significance set at P &lt; .05.ResultsThe SOP construct had significantly greater mean yield load, mean yield displacement, mean yield bending moment, mean composite rigidity and mean failure bending moment under static 4‐point bending to failure than the LCP construct. Mean number of cycles to failure under 4‐point bending was significantly greater for the SOP constructs but the mean number of cycles to failure in torsion was significantly greater for the LCP constructs. The LCP construct had significantly greater mean composite stiffness and significantly lesser mean displacement to yield and to failure in static torsion testing.ConclusionThe SOP construct was superior under bending static and cycling testing but the LCP construct was superior in static and cycling torsion testing.

Biomechanical testing of a hybrid locking plate fixation of equine sesamoid osteotomies

To compare the biomechanical properties of a hybrid locking compression plate (LCP) construct with the compression screw technique as a treatment for transverse mid-body proximal sesamoid bone fractures. Ten paired forelimbs from abattoir horses were used. The medial proximal sesamoid bone of each limb was osteotomized transversely and randomly assigned, to either repair with a two-hole 3.5 mm LCP or a 4.5 mm cortical screw placed in lag fashion. Each limb was tested biomechanically by axial loading in single cycle until failure. The point of failure was evaluated from the load-displacement curves. Then a gross evaluation and radiographs were performed to identify the mode of failure. The loads to failure of limbs repaired with the hybrid LCP construct (4968 N ± 2167) and the limbs repaired with the screw technique (3009 N ± 1091) were significantly different (p <0.01). The most common mode of failure was through a comminuted fracture of the apical fragment of the proximal sesamoid bone. The LCP technique has potential to achieve a better fracture stability and healing when applied to mid-body fractures of the proximal sesamoid bone. Further testing, particularly fatigue resistance is required to corroborate its potential as a treatment option for mid-body fractures of the proximal sesamoid bone.

English

Abstract Introduction In recent years, the treatment of distal femoral fractures has evolved although these fractures remain complex to treat and carry an inconsistent prognosis. Debate continues around choice of implant for fixation of metaphyseal–diaphyseal fractures. In this retrospective study, we evaluated and compared clinical and radiological outcomes of distal femur fracture stabilisation using retrograde nailing and locking compression plate constructs. Materials and Methods Between 2008 and 2013, 103 patients with distal femoral fracture who had been treated by retrograde intramedullary interlocking (IMIL) nailing (n = 57) and locking compression plating (LCP) (n = 46) were evaluated in this study at our centre. Results Clinical and radiographic evaluation demonstrated osseous healing within 6 months following retrograde nail and LCP plating in over 75% of patients. Average time of union in LCP group was 6.8 months and in retrograde nailing group was about 7.4 months. In the retrograde nail group, 5 out of 57 patients (9%) developed nonunion as no bony consolidation of the femoral fracture was observed 9 months after fixation. In the LCP group, nonunion was observed in 2 out of 46 patients (4%). Conclusion Outcome of retrograde intramedullary nailing and locking compression plating of distal femoral fractures in adults

Ex vivo cyclic mechanical behaviour of 2.4 mm locking plates compared with 2.4 mm limited contact plates in a cadaveric diaphyseal gap model

To compare the mechanical properties of locking compression plate (LCP) and limited contact dynamic compression plate (LC-DCP) constructs in an experimental model of comminuted fracture of the canine femur during eccentric cyclic loading. A 20 mm mid-diaphyseal gap was created in eighteen canine femora. A 10-hole, 2.4 mm stainless steel plate (LCP or LC-DCP) was applied with three bicortical screws in each bone fragment. Eccentric cyclic loadings were applied at 10 Hertz for 610,000 cycles. Quasistatic loading / unloading cycles were applied at 0 and 10,000 cycles, and then every 50,000 cycles. Structural stiffness was calculated as the slope of the linear portion of the load-displacement curves during quasistatic loading / unloading cycles. No bone failure or screw loosening occurred. Two of the nine LCP constructs failed by plate breakage during fatigue testing, whereas no gross failure occurred with the LC-DCP constructs. The mean first stiffness of the LCP constructs over the course of testing was 24.0% lower than that of constructs stabilized by LC-DCP. Construct stiffness increased in some specimens during testing, presumably due to changes in bone-plate contact. The first stiffness of LC-DCP constructs decreased by 19.4% and that of locked constructs by 34.3% during the cycling period. A biphasic stiffness profile was observed: the second stiffness was significantly greater than the first stiffness in both groups, which allowed progressive stabilization at elevated load levels. Because LCP are not compressed to the bone, they may have a longer working length across a fracture, and thus be less stiff. However, this may cause them to be more susceptible to fatigue failure if healing is delayed.

Suitability of DCPs with Screw Locking Elements to allow sufficient interfragmentary motion to promote secondary bone healing of osteoporotic fractures

This paper analyses the suitability of a system comprising a Dynamic Compression Plate (DCP) and Screw Locking Elements (SLEs) to allow sufficient interfragmentary motion to promote secondary bone healing in osteoporotic fractures.Four fixation systems were mounted on bone-simulating reinforced epoxy bars filled with solid rigid polyurethane foam. Group 1, used for comparison purposes, represents a system comprised of a Locking Compression Plate (LCP) and eight locking screws. Groups 2 and 3 represent a system comprised of a DCP plate with eight cortical screws and two SLEs placed on the screws furthest from (group 2) and nearest to (group 3) the fracture. Group 4 represents the system comprised of a DCP plate with SLEs placed on all eight cortical screws. Cyclic compression tests of up to 10,000 load cycles were performed in order to determine the parameters of interest, namely the stiffnesses and the interfragmentary motion of the various configurations under consideration. Tukey's multiple comparison test was used to analyse the existence or otherwise of significant differences between the means of the groups.At 10,000 cycles, interfragmentary motion at the far cortex for group 2 was 0.60±0.04mm and for group 3 0.59±0.03mm (there being no significant differences: p=0.995). The mean interfragmentary motion at the far cortex of the LCP construct was 70% less than that of the two groups with 2SLEs (there being significant differences: p=1.1×10−8). In the case of group 4 this figure was 45% less than in groups 2 and 3 (there being significant differences: p=5.6×10−6). At 10,000 cycles, interfragmentary motion at the near cortex for group 2 was 0.24±0.06mm and for group 3 0.24±0.03mm (there being no significant differences: p=1.000). The mean interfragmentary motion at the near cortex of the LCP construct was 70.8% less than that of the two groups with 2SLEs (there being significant differences: p=0.011). In the case of group 4 this figure was 66.7% less than in groups 2 and 3 (there being significant differences: p=0.016). The mean stiffness at 10,000 cycles was 960±110Nmm−1 for group 2 and 969±53Nmm−1 for group 3 (there being no significant differences: p=1.000). For group 1 (the LCP construct) the mean stiffness at 10,000 cycles was 3144±446Nmm−1, 3.25 times higher than that of groups 2 and 3 (there being significant differences: p=0.00002), and 1.6 times higher than that of the DCP+8SLEs construct (1944±408Nmm−1, there being significant differences: p=0.007).It is concluded that using the DCP+2SLEs construct sufficient interfragmentary motion is ensured to promote secondary bone healing. However, if too many SLEs are used the result may be, as with the LCP, an excessively rigid system for callus formation.

In-vitro comparison of LC-DCP- and LCP-constructs in the femur of newborn calves – a pilot study

BackgroundTo compare the biomechanical in-vitro characteristics of limited-contact dynamic compression plate (LC-DCP) and locking compression plate (LCP) constructs in an osteotomy gap model of femoral fracture in neonatal calves. Pairs of intact femurs from 10 calves that had died for reasons unrelated to the study were tested. A 7-hole LC-DCP with six 4.5 mm cortical screws was used in one femur and a 7-hole LCP with four 5.0 mm locking and two 4.5 mm cortical screws was used in the corresponding femur. The constructs were tested to failure by cyclic compression at a speed of 2 mm/s within six increasing force levels.ResultsThe bone-thread interface was stripped in 21 of 80 cortical screws (26.3%) before a pre-set insertion torque of 3 Nm was achieved. Only 3 corresponding intact pairs of constructs could be statistically compared for relative structural stiffness, actuator excursion and width of the osteotomy gap. Relative structural stiffness was significantly greater, actuator excursion and width of the osteotomy gap were significantly smaller in the LCP constructs. While failure occurred by loosening of the screws in the LC-DCP constructs, locking constructs failed by cutting large holes in the soft distal metaphyseal bone.ConclusionsAn insertion torque sufficient to provide adequate stability in femurs of newborn calves could not be achieved reliably with 4.5 mm cortical screws. Another limiting factor for both constructs was the weak cancellous bone of the distal fracture fragment. LCP constructs were significantly more resistant to compression than LC-DCP constructs.

Single cycle to failure in torsion of three standard and five locking plate constructs

The biomechanical properties of standard plates and recently designed locking plates were compared in torsion. We hypothesized that titanium (Ti) constructs would have the greatest deformation, and String of Pearls (SOP) constructs the greatest strength and stiffness. Dynamic compression plates (DCP), stainless steel (SS) limited contact (LC)-DCP, Ti LC-DCP, locking compression plate (LCP), 10 mm and 11 mm Advanced Locking Plate System (ALPS) 10 and 11, SOP and Fixin plates were applied to a validated bone model simulating a bridging osteosynthesis. Yield torque (strength), yield angle (deformation) and stiffness were compared using one-way ANOVA with post hoc Tukey (p <0.05). The ALPS 11 constructs had significantly greater elastic deformation than all constructs except for the ALPS 10. There were not any differences in strength observed except for the ALPS 10 constructs, which was less than that for the SOP, LCP, DCP and ALPS 11 constructs. No differences in construct torsional stiffness were observed with the SS LC-DCP, DCP, LCP and SOP constructs; however all had greater stiffness than all remaining constructs. The ALPS 10 construct had lower stiffness than all constructs. Modulus of elasticity of Ti explains the higher deformation and lower stiffness of these systems, with similar results for the Fixin due to its lower section modulus compared to all other plates. The SOP and standard constructs had surprisingly similar biomechanical properties in torsion. The rationale for selecting these implants for fracture repair likely needs to be based upon their differing biomechanical properties inherent to the diverse implant systems.

An In Vitro Biomechanical Comparison of a Locking Compression Plate Fixation and Kerf Cut Cylinder Fixation for Ventral Arthrodesis of the Fourth and the Fifth Equine Cervical Vertebrae

To (1) define mechanical properties in flexion, extension, and left lateral bending of cadaveric equine 4th and 5th cervical (C4-C5) articulations, (2) compare biomechanical properties of C4-C5 when stabilized with a kerf cut cylinder (KCC) compared with a ventrally placed 4.5 mm locking compression plate (LCP). In vitro biomechanical investigation. Cadaveric adult equine cervical vertebral columns (n=54). Cervical vertebrae aged by horse dentition and size measured from radiographs were divided into 3 age groups then randomly allocated to 3 groups. The C4-C5 articulation was treated differently in each of the groups: KCC group; KCC-implanted LCP group; 8-hole 4.5 mm LCP implanted and intact group; no implant. Specimens were randomly subdivided into 1 of 3 loading conditions, before testing to failure under 4-point bending. Stiffness, yield bending moment, failure bending moment, and failure mode were recorded. General linear models were performed to analyze associations between biomechanical properties and test variables. All specimens failed at the C4-C5 intervertebral articulation. The cervical vertebrae with the LCP construct had significantly higher stiffness, yield bending moment, and failure bending moment than the KCC-implanted cervical vertebrae. Failure modes differed between groups and varied with loading direction: KCC group, fractures of C5 associated with the KCC were common; LCP group, screw pull out or fractures (of C4 and C5 bodies, during extension and the caudal aspect of C4 during left lateral bending) were common; and intact group, subluxations were most common. In this model, LCP constructs had superior biomechanical properties compared with KCC constructs. Further research investigating the effect of repetitive loading is indicated.

Treatment of distal humeral fractures using conventional implants. Biomechanical evaluation of a new implant configuration

BackgroundIn the face of costly fixation hardware with varying performance for treatment of distal humeral fractures, a novel technique (U-Frame) is proposed using conventional implants in a 180° plate arrangement. In this in-vitro study the biomechanical stability of this method was compared with the established technique which utilizes angular stable locking compression plates (LCP) in a 90° configuration.MethodsAn unstable distal 3-part fracture (AO 13-C2.3) was created in eight pairs of human cadaveric humeri. All bone pairs were operated with either the "Frame" technique, where two parallel plates are distally interconnected, or with the LCP technique. The specimens were cyclically loaded in simulated flexion and extension of the arm until failure of the construct occurred. Motion of all fragments was tracked by means of optical motion capturing. Construct stiffness and cycles to failure were identified for all specimens.ResultsCompared to the LCP constructs, the "Frame" technique revealed significant higher construct stiffness in extension of the arm (P = 0.01). The stiffness in flexion was not significantly different (P = 0.16). Number of cycles to failure was found significantly larger for the "Frame" technique (P = 0.01).ConclusionsIn an in-vitro context the proposed method offers enhanced biomechanical stability and at the same time significantly reduces implant costs.

A biomechanical comparison of 3.5 locking compression plate fixation to 3.5 limited contact dynamic compression plate fixation in a canine cadaveric distal humeral metaphyseal gap model

3.5 locking compression plate (LCP) fixation was compared to 3.5 limited contact dynamic compression plate (LC-DCP) fixation in a canine cadaveric, distal humeral metaphyseal gap model. Thirty paired humeri from adult, large breed dogs were separated into equal groups based on testing: static compression, cyclic compression, and cyclic torsion. Humeral constructs stabilised with LCP were significantly stiffer than those plated with LC-DCP when loaded in static axial compression (P = 0.0004). When cyclically loaded in axial compression, the LCP constructs were significantly less stiff than the LC-DCP constructs (P = 0.0029). Constructs plated with LCP were significantly less resistant to torsion over 500 cycles than those plated with LC-DCP (P<0.0001). The increased stiffness of LCP constructs in monotonic loading compared to constructs stabilised with non-locking plates may be attributed to the stability afforded by the plate-screw interface of locking plates. The LCP constructs demonstrated less stiffness in dynamic testing in this model, likely due to plate-bone offset secondary to non-anatomic contouring and occasional incomplete seating of the locking screws when using the torque-limiting screw driver. Resolution of these aspects of LCP application may help improve the stiffness of fixation in fractures modeled by the experimental set-up of this investigation.

A pilot in vitro biomechanical comparison of locking compression plate fixation and kerf-cut cylinder fixation for ventral fusion of fourth and fifth equine cervical vertebrae

The mechanical properties of equine cervical vertebrae joined by implants have not yet been reported. Locking compression plates (LCP) may provide a useful alternative system to the commonly used stainless steel kerf-cut cylinders (KCC) currently used for fixation of cervical vertebrae in horses. The objectives of this study were to establish a method for biomechanical testing of equine C4-C5 articulations and to compare the biomechanical properties of cadaveric spines stabilised with KCC and LCP. Twenty-four equine cadaveric cervical spines were size measured from radiographs, and then randomly allocated to four groups. The C4-C5 articulation for each group was treated in the following way: group 1: KCC implanted, group 2: 8-hole 4.5/5.0 LCP implanted, group 3: 11-hole 3.5 LCP implanted and group 4: No implant. The specimens were fixed in resin and tested under four-point bending in ventral flexion until failure. Stiffness, maximum moment to failure and mode of failure were recorded for all specimens. General linear models were performed to analyse associations. All spines failed at the C4-C5 articulation. Failure however differed between groups with fractures in group 1, screw pull-out in groups 2 and 3, and disarticulation in group 4 being the common failure modes. The stiffness and maximum moment to failure of the KCC and LCP implanted spines were similar. Increasing age was significantly associated with decreasing moment to failure and increasing size was significantly associated with increasing moment to failure and stiffness. This study describes a successful technique for examining the biomechanical properties of equine cervical vertebrae. The LCP constructs had similar mechanical properties to the KCC which may justify their use in clinical cases.

Mechanical Comparison of 3.5 mm Broad Dynamic Compression Plate, Broad Limited‐Contact Dynamic Compression Plate, and Narrow Locking Compression Plate Systems Using Interfragmentary Gap Models

To compare (1) pullout properties between 3.5 mm cortical and locking screws, and (2) mechanical properties and gap displacements between the 3.5 mm broad limited-contact dynamic compression plate (LC-DCP), broad dynamic compression plate (DCP), and narrow locking compression plate (LCP), during axial loading of plate-stabilized diaphyseal fragments with an interfragmentary gap. In vitro mechanical testing of implanted polyurethane foam (PUF) hollow cylinders that simulated compact or osteopenic diaphyseal bone. (1) Five cortical and locking screws and (2) 4 PUF-plate constructs for each plate type; using high- and low-density (0.8 and 0.32 g/cm(3)) cylinders. (1) Screws were completely extracted at 5 mm/min. (2) Plated constructs were axially compressed at 300 N/s for 10 cycles from 5 to 355 N to determine gap displacement during physiologic loading, followed by single cycle increasing load to failure. Pullout properties were not different between screw types. All plate constructs had yield loads over 3 times trotting loads. Gap closure occurred with LC-DCP and DCP constructs, but not LCP constructs. LCP construct properties were most similar to LC-DCP and DCP construct properties in the low-density model. All plate systems sustained physiologic limb loads. Only LCP constructs maintained some gap integrity, although LC-DCP and DCP screws were placed in neutral position. The LCP system is more likely than LC-DCP and DCP systems, with neutrally positioned screws, to maintain a planned interfragmentary gap, although gap strains range from 0% to 15% across the 2 mm gap during a trot load.