Stiffness and Endurance of a Locking Compression Plate Fixed on Fractured Femur

Abstract

The effects of locking screw position (long column fixation—long distance between the nearest screws to the fracture—and short column fixation—short distance between the nearest screws to the fracture) and fracture gap size (1-mm and 8-mm transverse fracture gap) on stiffness and fatigue of fractured femur fixed with a locking compression plate (LCP) were biomechanically evaluated. The stiffness of 1-mm fracture gap models and that of intact femoral model were in the range of 270–284 N/mm, while those of 8-mm fracture gap models were significantly lower (155–170 N/mm). After 1,000,000 cycles of loading, no fracture of LCP of 1-mm fracture gap models fixed in either long column or short column fashions occurred. On the other hand, the complete fractures of LCPs of 8-mm fracture gap models fixed in long column and short column fashions occurred after 51,500 and 42,000 cycles of loading, respectively. These results suggest that the full weight loading may be allowed for the patient with 1-mm transverse femoral fracture fixed with an LCP. On the other hand, the full load of walking should be avoided for the patient with 8-mm transverse femoral fracture fixed with an LCP before adequate healing.

Locking Buttons Increase Fatigue Life of Locking Plates in a Segmental Bone Defect Model

“…The plates used in this study also were stainless steel, however, testing in that study was performed using peak loads slightly greater than the elastic limit, whereas we used loads that were 65% of the elastic limit. All the plates in that study [19] and ours broke through the screw holes closest to the defect, consistent with two additional studies that showed the greatest amount of stress in the plate is at the screw holes nearest the defect [2,24].…”

Effect of plate working length on plate stiffness and cyclic fatigue life in a cadaveric femoral fracture gap model stabilized with a 12-hole 2.4 mm locking compression plate

“…Maxwell et al reported similar results when screw placement was evaluated in 3.5 mm dynamic compression plates and limited contact dynamic compression plates applied in a fracture gap model [11]. Recent studies comparing the cyclic fatigue properties of plates applied with a short and long working length found that the constructs with a longer working length withstood more cycles before failure, although the differences between stabilization techniques were not significant [5,9]. …”

“…Plate working length has been shown to influence construct stiffness, plate strain and cyclic fatigue properties of the plate [5,8-11]. The lack of load sharing between the stabilized bone and the implants increases the risk of cyclic fatigue and early failure of the implant [9,12]. A mechanical study evaluating the mechanical endurance of human femora stabilized with 14-hole broad 4.5 mm LCPs found that constructs with load sharing resisted 20 times more cycles than the constructs with an 8 mm segmental diaphyseal gap [13].…”

“…In contrast, Field et al reported that omitting two screws proximal and distal to the fracture had no significant effect on either bending or torsional stiffness of conventional plate constructs in a comparable bridge plate configuration [14]. Studies evaluating the effect of working length on the cyclic fatigue properties of plated constructs have yielded inconsistent results [5,9,12]. Stoffel et al found that the constructs with shorter plate working length were more resistant to cyclic loading [12].…”

Observe a distância entre a linha de fratura e o comprimento da área de trabalho: análise bidimensional de elementos finitos em modelo de fixação extramedular

“…Assim, quanto maior a capacidade elástica de deformação da placa em ponte, menor seu risco de quebra ou fadiga. 17 Com modelos artificiais de fêmur, Hoffmeier et al 18 e Kanchanomai et al 19 observaram redução na tensão superficial de placas bloqueadas em aço inoxidá-vel e em titânio quanto maior a área de trabalho do implante. Isso mostra que comportamento de fadiga dependente, dentre outros fatores relacionados à técnica de osteossíntese, da área de trabalho.…”