Comminuted Fracture Model Research Articles

A biomechanical matched-pair comparison of two different locking plates for tibial diaphyseal comminuted fracture: carbon fiber-reinforced poly-ether-ether-ketone (CF-PEEK) versus titanium plates

BackgroundSeveral methods have been proposed to reduce plate construct stiffness and promote secondary bone healing. In this study, we explored the stiffness and strength of the new carbon fiber-reinforced poly-ether-ether-ketone (CF 50) plate compared with the titanium alloy plate (Ti6Al4V).MethodsTitanium and CF-PEEK locking plates were tested in a tibial non-osteoporotic diaphyseal comminuted fracture model to determine construct stiffness in axial compression, torsion, and bending. Subsequently, constructs were loaded until construct failure to determine construct strength.ResultsRelative to the titanium locking plate, the stiffness of the CF-PEEK locking plate was 6.8% and 30.8% lower in 200 N and 700 N axial compression, respectively (P < 0.05), 64.9% lower in torsion (P < 0.05), and 48.9% lower in bending (P < 0.05). The strength of the CF-PEEK locking plate was only 2.6% lower under axial compression, 7.8% lower in torsion, and 4.8% lower in bending than the titanium locking plate (P > 0.05).ConclusionsThe CF-PEEK locking plate significantly reduced axial, torsion, and bending stiffness compared with the titanium locking plate. Nonetheless, axial, torsional, and bending strength showed only a modest reduction. Considering its other advantages, which include radiolucency and artifact-free imaging, the CF-PEEK locking plate therefore deserves further clinical investigation.

Comminuted olecranon fractures: biomechanical testing of locked versus minifragment non-locked plate fixation.

Open reduction and internal fixation has long been accepted as optimal treatment for displaced olecranon fractures based on poor results seen with conservative management. With the presence of comminution, tension-band wiring constructs are contraindicated due to tendency to compress through fragments, thereby shortening the articular segment. Therefore, plate fixation is typically employed. Our hypothesis was that in a comminuted fracture model, 2.7mm reconstruction plating without locking screws will perform equally to 3.5mm locked plating in terms of fracture displacement and rotation (shear). A three-part comminuted olecranon fracture pattern was created in nine matched pairs of cadaveric specimen using an oscillating saw in standardized, reproducible fashion. Each matched pair was then randomized to receive either 2.7mm reconstruction plating or 3.5mm proximal ulna locked plating. Random allocation software was used to assign the 2.7mm plate construct to either the right or left side of each pair with the contralateral receiving the 3.5mm plate construct. Specimens were cyclically loaded simulating passive range of motion exercises commonly performed during rehabilitation. Displacement and rotation in relation to the long axis of the ulna were measured through motion capture. Fragment gapping and rotation was quantified following 100 cycles at 10N and again following 100 cycles at 500N. No significant differences were detected between the 2.7 and 3.5mm plates in fracture rotation or gapping following loads at 10N (0.5° and 0.7°; 0.6 and 1.2mm; respectively; p>0.05) or 500N (2.3° and 1.6°; 3.8 and 3.1mm; respectively; p>0.05) loading. Fragment rotation and gapping were positively correlated within each plate construct (R 2>0.445; p<0.05). 2.7mm plating is an alternative to 3.5mm locked plating with decreased plate prominence without significantly sacrificing displacement and rotational control. This is beneficial in fracture patterns where the traditional dorsal plating does not offer optimal screw trajectory.

Effect of bending direction on the mechanical behaviour of 3.5 mm String-of-Pearls and Limited Contact Dynamic Compression Plate constructs.

To compare the bending properties of String-of-Pearls® (SOP) and Limited Contact Dynamic Compression Plate® (LC-DCP) constructs in orthogonal bending directions. 3.5 mm SOP and LC-DCP plates were fixed to a bone model simulating a comminuted tibial fracture. Specimens were non-destructively tested in both mediolateral and craniocaudal bending for 10 cycles. Bending stiffness and total angular deformation were compared using parametric analyses (p <0.05). For both constructs, stiffness was significantly less when bending moments were applied against the thickness of the plates (mediolateral bending) than against the width (craniocaudal bending). When compared to the mediolateral plane, bending constructs in the craniocaudal plane resulted in a 49% (SOP group) and 370% (LC-DCP group) increase in stiffness (p <0.001). Mediolateral bending stiffness was significantly greater in the SOP than the LC-DCP constructs. Conversely, in craniocaudal bending, SOP constructs stiffness was significantly less than that of the LC-DCP constructs. The differences between the two constructs in total angular deformation had an identical pattern of significance. This study found that SOP showed less variability between the orthogonal bending directions than LC-DCP in a comminuted fracture model, and also described the bi-planar bending behaviour of both constructs. Although not exhibiting identical bending properties in both planes, SOP constructs had a more homogenous bending behaviour in orthogonal loading directions. The difference between the SOP with a circular cross sectional shape compared to the rectangular shape of standard plates is probably responsible for this difference.

Biomechanical analysis of operative methods in the treatment of extra-articular fracture of the proximal tibia.

BackgroundTo determine relative fixation strengths of a single lateral locking plate, a double construct of a locking plate, and a tibial nail used in treatment of proximal tibial extra-articular fractures.MethodsThree groups of composite tibial synthetic bones consisting of 5 specimens per group were included: lateral plating (LP) using a locking compression plate-proximal lateral tibia (LCP-PLT), double plating (DP) using a LCP-PLT and a locking compression plate-medial proximal tibia, and intramedullary nailing (IN) using an expert tibial nail. To simulate a comminuted fracture model, a gap osteotomy measuring 1 cm was created 8 cm below the knee joint. For each tibia, a minimal preload of 100 N was applied before loading to failure. A vertical load was applied at 25 mm/min until tibial failure.ResultsUnder axial loading, fixation strength of DP (14,387.3 N; standard deviation [SD], 1,852.1) was 17.5% greater than that of LP (12,249.3 N; SD, 1,371.6), and 60% less than that of IN (22,879.6 N; SD, 1,578.8; p < 0.001, Kruskal-Wallis test). For ultimate displacement under axial loading, similar results were observed for LP (5.74 mm; SD, 1.01) and DP (4.45 mm; SD, 0.96), with a larger displacement for IN (5.84 mm; SD, 0.99). The median stiffness values were 2,308.7 N/mm (range, 2,147.5 to 2,521.4 N/mm; SD, 165.42) for the LP group, 4,128.2 N/mm (range, 3,028.1 to 4,831.0 N/mm; SD, 832.88) for the DP group, and 5,517.5 N/mm (range, 3,933.1 to 7,078.2 N/mm; SD, 1,296.19) for the IN group.ConclusionsDuring biomechanical testing of a simulated comminuted proximal tibial fracture model, the DP proved to be stronger than the LP in terms of ultimate strength. IN proved to be the strongest; however, for minimally invasive osteosynthesis, which may be technically difficult to perform using a nail, the performance of the DP construct may lend credence to the additional use of a medial locking plate.

A biomechanical experiment and clinical study of the use of figure of eight plus circular wiring fixation for the treatment of olecranon fractures

The aim of the present study was to evaluate the stability of the figure of eight plus circular wiring fixation technique compared with four common internal fixation techniques and to provide experimental data for the selection of internal fixation techniques clinically. A total of 20 fresh cadaveric elbow joints were used as transverse, oblique and comminuted olecranon fracture models. Five techniques of internal fixation were investigated: circular wiring, figure of eight wiring, circular plus figure of eight wiring, Kirschner wire (K-wire) and screw fixation. The elbow joints were flexed at 90°. The fixation performance was tested using a high-precision displacement sensor. Displacement-load curves revealed that the strength of internal fixation was weakest when using circular wiring alone and that circular wiring plus figure of eight wiring fixation was stronger than that of figure of eight wiring or screw fixation. The difference was statistically significant (P<0.05). There were no significant differences between circular wiring plus figure of eight wiring fixation and K-wire fixation in the transverse and oblique fracture models (P>0.05). However, figure of eight plus circular wiring fixation was superior to K-wire fixation in the comminuted fracture model, with a tensile force of 67.42±2.17 vs. 58.52±2.17 N, respectively (P<0.05). All 152 patients with olecranon fractures who received circular wiring plus figure of eight wiring fixation recovered and 108 were included in the follow-up for an average of 12 months. The rate of excellent/fairly good recovery was 98.10%. Due to its reliability, simple surgery, lower invasiveness and lower cost, figure of eight plus circular wiring fixation is an ideal choice for the internal fixation of olecranon fractures, particularly comminuted fractures, compared with circular wiring, figure of eight wiring or screw fixation.

Fatigue Load of Current Tibial Intramedullary Nail Designs: A Simulated Study

Comminuted tibial shaft fractures are traditionally treated with statically locked intramedullary nailing and protected weight bearing until fracture callous is evident. The purpose of this study was to demonstrate that a simulation of immediate full weight bearing following intramedullary nailing of these fractures does not result in implant failure.A comminuted fracture model was created using 2 pieces of polyvinyl chloride (PVC) pipe. Ten-millimeter-diameter tibial nails (Synthes, Paoli, Pennsylvania; Styker, Mahwah, New Jersey; Zimmer, Warsaw, Indiana; Smith & Nephew, Memphis, Tennessee) were inserted within the PVC pipe and secured proximally and distally with 2 or 3 locking bolts. The constructs were cycled in axial compression for 500,000 cycles or until implant failure. The tests were conducted using a modified staircase method (200 N per step), and the fatigue strength was identified for each of the tibial nail designs. When 2 interlocking bolts were placed proximally and distally, the fatigue strength was between 900 and 1100 N for the Stryker nail, 1100 and 1300 N for the Zimmer nail, 1200 and 1400 N for the Synthes nail, and 1400 and 1600 N for the Smith & Nephew nail. Adding a third interlocking bolt proximally and distally to the Smith & Nephew nail increased the fatigue strength by 13% to between 1700 and 1900 N. In all cases, implant failures occurred through the proximal or distal interlocking bolts.Biomechanical tests suggest that current tibial nail designs may permit immediate full weight bearing of comminuted tibial shaft fractures with minimal risk of implant failure. This may facilitate mobilization in the early postoperative period, especially in the multiply injured patient.

Ability and Limitation of Radiographic Assessment of Fracture Healing in Rats

The purpose of the present study was to assess whether clinicians are actually able to evaluate the mechanical status of fracture healing from radiograms. Fifteen orthopaedic surgeons evaluated the radiograms of experimentally produced femur fractures in rats and predicted mechanical strength (%) of the affected side compared to the unaffected control side. Following this, actual mechanical strength of the affected and control side was determined by a three-point bending test. The median of the strength in the transverse fracture model predicted from radiograms was 33% (2 weeks), 72% (4 weeks), 88% (6 weeks), 84% (8 weeks), and 89% (12 weeks). The actual measured recovery ratio of mechanical strength (exp/control x 100) was 36%, 76%, 93%, 89%, and 106% in each observation period respectively. The tendency was almost the same in a comminuted fracture model. The mean recovery rate determined by interpretation of the surgeons correlated linearly to the actual measured mechanical strength determined by mechanical testing (R(2): 0.80 in transverse fracture, 0.60 in comminuted fracture). Clinicians demonstrated that a comparatively good evaluation of the mechanical status of fracture healing is possible from radiograms up to approximately 80% recovery. However, they tended to make less accurate, weaker assessments at the final stages. In conclusion, radiograms may be inadequate for evaluation of fracture healing completion.

Biomechanical Comparison of Flexible Stainless Steel and Titanium Nails with External Fixation Using a Femur Fracture Model

There are several options available for surgical stabilization of pediatric femoral shaft fractures. The purpose of this study was to compare the stability afforded by Ender stainless steel nails, titanium elastic nails, and one-plane unilateral external fixators for the fixation using a synthetic adolescent midshaft femur fracture model. The anterior-posterior (sagittal plane) bending, lateral (coronal plane) bending, torsional, and axial stiffness values were calculated using 6 different fixation configurations. These included pairs of 3.5-mm-diameter Ender nails with and without distal locking, 3.5- and 4.0-mm-diameter titanium elastic nails as well as single- and double-stacked monolateral external fixators. Eight synthetic femur models, 4 each with simulated transverse and comminuted fracture patterns, were sequentially tested for stability afforded by the various fracture fixation configurations. External fixation exhibited significantly greater control of anterior-posterior angulation compared with all flexible-nailing systems. Although Ender nails were slightly superior to titanium nails in control of sagittal plane angulation, this was not statistically significant. Compared with the external fixation constructs, all 4 flexible nail constructs demonstrated higher torsional stability. For prevention of axial shortening, all fixation methods were similar for the transverse fracture pattern, whereas external fixation was superior to flexible nails in the comminuted fracture model. No significant benefit was demonstrated with double stacking of external fixators. These findings may help guide clinicians choose the optimal fixation method for treatment of pediatric femoral shaft fractures.

Metabolic measurement techniques to assess bone fracture healing: a preliminary study.

The purpose of this study was to project the effectiveness of using positron emission tomography for evaluation of fracture healing using the analogous method of liquid scintillation. A reproducible comminuted fracture model in rabbit femurs was stabilized with external fixation. Thirty-nine rabbits were divided into four groups: Group A had slight distraction, Group B had shortening, Group C had a bone defect, and Group D was the sham control group. At 2 and 4 weeks after fracture, the femurs had liquid scintillation measurements using 2-[14C]-deoxyglucose (2DG C-14). Glucose uptake was significantly elevated in the experimental limb relative to the contralateral control femurs at both times. The distraction group showed a significant decrease in uptake from 2-4 weeks. There was a high correlation between the liquid scintillation measurements and the radiographic fracture healing scores, with higher levels of 2DG C-14 uptake corresponding to lower levels of fracture healing calcification. The high correlation found between 2DG C-14 uptake and radiographic scores suggests that positron emission tomography used in conjunction with a glucose-based radiopharmaceutical such as 2-[18F]fluoro-2-deoxyglucose can monitor the fracture healing process effectively.