Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

Abstract

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

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

“…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.…”

“…Due to its stability and suitability for tissue engineering and bone biomaterial research, locking compression plate fixation has gained widespread use in bone segmental defect models [ 20 , 25 ]. However, questions regarding risk factors for locking plate implant failure and possible torsional instability persist, and relatively few studies have been published assessing complications associated with tibial locking plate gap stabilization, particularly in small ruminant species [ 6 , 11 , 26 ]. Finite element analysis (FEA) has allowed exploration of intrinsic factors of LCP fixation including plate length, positioning of the plate on the bone, screw number, and screw placement.…”

“…Goats are a preferred model for translational orthopedic studies due to their trainability, cost-effectiveness, and translational characteristics including body weight, long bone dimensions, bone mineral composition, metabolic rate, and bone remodeling rate compared to humans [19,25]. The caprine tibial segmental defect model has been well documented in the literature, but fixation and stabilization options vary among research groups [11,[16][17][18]. Fracture fixation has varied based on clinical application, and reported methods for external and internal fixation include options such as intramedullary pins/nails, intramedullary interlocking nails, single bridging plates, or overlapping auto-compression plates [25,30].…”

“…Conventional dynamic compression plating requires adequate plate to bone contact during screw tightening to achieve desired stability between the plate and bone surface, and potential complications such as periosteal vascular compromise, stress risers, and loss of compression in compromised bone may lead to fracture complications [8,22,35]. In contrast, locking compression plating relies more on the screw-plate interface for construct stability, and locking plate fixation is particularly useful in cases of bone loss or poor bone integrity [11,32]. Biomechanically, DCPs and LC-DCPs convert axial load to shear stress whereas LCPs convert axial load to compressive force, and the stability of a locking plate construct will reflect the sum of screw torques, not merely the friction of the bone-plate interface [21].…”

Changes in tibial cortical dimensions and density associated with long‐term locking plate fixation in goats

“…Compression plating comorbidities and complications reflect these fixation biomechanics. Each screw is loaded individually at the screw‐bone interface and repetitive interface loads can lead to screw toggle, failure, or pullout complications [1, 15]. These interfaces can be further compromised by cortical bone loss, either during the fracture itself or as a result of the fracture fixation (periosteal injury, soft tissue damage, or cortical stress‐shielding) [1, 7, 20].…”