Biomechanical comparison of gourd-shaped LCP versus LCP for fixation of comminuted tibial shaft fracture

Abstract

The purpose of this study was to compare monotonic biomechanical properties of gourd-shaped LCP fixation with LCP fixation of human tibial shaft in gap fracture mode. Twenty paired fresh cadaveric human tibias were randomly divided into 4 groups (5 pairs each): (1) axial loading single cycle to failure testing, (2) torsion single cycle to failure testing, (3) 4-point bending single cycle to failure testing, and (4) dynamic 4-point bending testing. A 7-hole 4.5 mm gourd-shaped LCP was secured on the anteromedial surface of 1 randomly selected bone from each pair, respectively, using 6 locking screws in the 1st, 2nd, 3rd, 5th, 6th and 7th hole with the middle hole unfilled and just located at the mid-diaphysis of the tibia. A 7-hole 4.5 mm LCP was secured on the other bone with the same method. Standard AO/ASIF techniques were used. After fixation finished, a 10 mm gap in the mid-diaphysis of tibia was created, centrally located at the unfilled hole. The axial, torsional, and bending stiffness and failure strengths were calculated from the collected data in static testings and statistically compared using paired Student's t-test. The 4-point bending fatigue lives of the two constructs were calculated from the dynamic testing data and also statistically compared using paired Student's t-test. Failure modes were recorded and visually analyzed. P<0.05 was considered significant. Results showed that the axial, torsional and bending stiffness of gourd-shaped LCP construct was greater (4%, 19%, 12%, respectively, P<0.05) than that of the LCP construct, and the axial, torsional and bending failure strengths of gourd-shaped LCP construct were stronger (10%, 46%, 29%, respectively, P<0.05) than those of the LCP construct. Both constructs failed as a result of plate plastic torsional deformation. After axial loading and 4-point bending testings, LCP failed in term of an obvious deformation of bent apex just at the unfilled plate hole, while the gourd-shaped LCP failed in term of a deformation of bent arc between the 3rd and 5th holes, which indicated a more consistent stress distribution on gourd-shaped LCP. Fatigue life of gourd-shaped LCP construct was significantly greater than LCP construct (153 836±2 228 vs. 132 471±6 460 cycles, P<0.01). All constructs failed as a result of fracture of the plate through the compression hole of the unfilled combination screw hole. The biomechanical testing showed that gourd-shaped LCP can provide greater stiffness and strength, and longer fatigue life than LCP. The gourd-shaped LCP may be more advantageous mechanically and may reduce the plate breakage rate clinically.

Investigating the biomechanical function of the plate-type external fixator in the treatment of tibial fractures: a biomechanical study

“…External fixators used in present clinical practice have various limitations, including insufficient fixation stiffness and strength, leading to poor healing, or high construct profiles, resulting in nonpatient friendly physical burden [13][14][15][16][17]. It is therefore essential to design a novel prototype of an external fixator for tibial fracture to increase rigidity and strength while reducing the profile of the fixation constructs.…”

Measuring Orthopedic Plate Strain to Track Bone Healing Using a Fluidic Sensor Read via Plain Radiography

“…Although no single study presents the entire applied load vs. average or probable cycles to failure, from prior studies at low and high cycle number we can estimate its shape for bent and unbent plates based on three studies. [28]–[30] Plates are designed to align bone fragments and limit interfragmentary motion, but allow some bending to encourage callus formation. [31] Tibial plates support short term weight bearing above 1×BW, but will fail under larger loads and eventually fatigue under repetitive cycling of 1×BW.…”

“…For a single cycle, Lindeque et al found that proximal locking compression plates (LCP) failed under loads of 1720 N for Synthes plates, and Xu et al found Zimmer plates and 1500 N for mid-tibial shaft LCP, averaging to around 2x BW for an 80 kg person. [28], [29] Additionally, Brunner et al studied high cycle fatigue failure for normal and bent titanium plates (plate bending is sometimes done deliberately to better fit the bone contour and also can occur naturally during the fixation process). At 106 cycles in NaCl solution they report 7 Nm for unbent plates and 3 Nm for plates that were bent prior to fixation.…”

In vitro analysis and in vivo assessment of fracture complications associated with use of locking plate constructs for stabilization of caprine tibial segmental defects

“…Orthopedic plate stabilization is a desirable option as it reflects the current standard of care for clinical management of fractures, does not interfere with the defect, and provides for ease of imaging assessment for evaluation of gap fillers including biomaterial scaffolds and other implants [ 25 ]. However, plate systems used in this model utilize a range of options including dynamic compression plates (DCP), limited-contact dynamic compression plates (LC-DCP), point-contact fixators (PC-Fix), locking compression plates (LCP), and locking plates (LP) [ 3 , 34 ].…”

“…As the bone defect heals and bony union is established, plate stresses decrease. However, if the plate reaches fatigue limit prior to bony union or if the fixation is biomechanically unsound, the construct will fail [ 11 , 19 , 34 ]. Avoidance of early loading and carefully monitored rehabilitation following plate fixation are common practices in human orthopedics to maximize fixation stability and reduce the risk of early fatigue, and immediate postoperative weightbearing in preclinical animal models poses a significant challenge to fixation longevity.…”