Internal plate fixation of fractures: short history and recent developments

Abstract

Metal plates for internal fixation of fractures have been used for more than 100 years. Although initial shortcomings such as corrosion and insufficient strength have been overcome, more recent designs have not solved all problems. Further research is needed to develop a plate that accelerates fracture healing while not interfering with bone physiology. The introduction of rigid plates had by far the greatest impact on plate fixation of fractures. However, it led to cortical porosis, delayed bridging, and refractures after plate removal. These unwarranted effects were said to be caused by bone-plate contact interfering with cortical perfusion. Consequently, further plate modifications aimed to reduce this contact area to minimize necrosis and subsequent porosis. The advocates of limited-contact plates have not published measurements of the contact area or proof of the temporary nature of the porosis. Moreover, clinical studies of newer plate types have failed to show a superior outcome. Histomor-phometric measurements of the cortex showed no difference in the extent of necrosis under plates having different contact areas. Necrosis was predominant in the periosteal cortical half, whereas porosis occurred mostly in the endosteal cortical half. No positive correlation was found between either. The scientific evidence to date strongly suggests that bone loss is caused by stress shielding and not interference with cortical perfusion secondary to bone-plate contact. Consequently, an axially compressible plate (ACP) incorporating polylactide (PLA) inserts press-fit around screw holes was designed. The bioresorbable inserts should allow for (1) increased micromotion in the axial plane to promote healing during the union phase and (2) gradual degradation over time to decrease stress shielding during the remodeling phase. Results of ongoing experimental results are encouraging. Only plates allowing dynamic compression in the axial plane can lead to a revolution in fracture fixation.

Fig. 1

Lane’s plate abandoned because of corrosion (1895). (From Bechtol CO, Fergusson AB, Laing PE. Metals and Engineering in Bone and Joint Surgery. Williams Wilkins; Baltimore: 1959. p. 20, with permission)

Fig. 2

Lambotte’s plate (1909) is thin, round, and tapered at both ends

Fig. 3

Structural instability of Eggers’ plate

Fig. 4

Danis’ plate (1949) called “coapteur” suppresses interfragmentary motion and increases stability of fixation through interfragmentary compression achieved by tightening the side screw

Fig. 5

Primary bone healing

Fig. 6

Bagby and Janes’ (1956) oval holes designed for interfragmentary compression during screw tightening. (From Uhthoff HK. Current Concepts of Internal Fixation of Fractures. Heidelberg: Springer-Verlag; 1980. p. 175, with permission of Springer Science and Business Media)

Fig. 7

Müller’s plate design (1965) achieves interfragmentary compression by tightening a tensioner that is temporarily anchored to the bone and the plate. (From Sequin F, Texhammar R. AO/ASIF Instrumentation. Heidelberg: Springer-Verlag; 1981. p. 72, with permission of Springer Science and Business Media)

Fig. 8

Dynamic compression plate (DCP) incorporates specially designed oval holes similar to Bagby and Janes’ invention to compress bony fragments during screw tightening

Fig. 9

Cortical bone loss under rigid plating

Fig. 10

Railed plates (left) have limited bone-plate contact area compared to contact plates (right)

Fig. 11

Decreased cortical perfusion is more pronounced with increased bone-plate contact with contact plates (left) versus railed plates (right)

Fig. 12

Porosis is more pronounced in the endosteal half of the cortex of a beagle femur plated with six-hole stainless steel rigid plates. HPS ×25

Fig. 13

Point-contact fixator (PC-Fix) acts like a fixator as the monocortical screws lock into the plate achieving angular stability and preventing the bone to be pulled toward the plate. (From Fernandez Dell’Oca AA, Tepic S, Frigg R, Meisser A, Haas N, Perren SM. Treating forearm fractures using an internal fixator: a prospective study. Clin Orthop 2001;389:196–205, with permission of Lippincott Williams & Wilkins)

Fig. 14

Radiograph of mongrel canine femur plated with sixhole limited-contact dynamic compression plate (LC-DCP) at 16 weeks following harvest. Endosteal buildup at both ends of the plate is indicative of a high percentage load transferred through the plate

Fig. 15

Axially flexible plate (AFP) for beagle femors incorporates polymethylmethacrylate (PMMA) cushions between plate and screw head to allow increased micromotion in the axial direction only

Fig. 16

a Axially compressible plate (ACP). Screws (A) and outer shell (B) are titanium, and inserts (C) are polylactic acid (PLA). Inserts allow increased micromotion in the axial plane during union and reduced stress shielding during remodeling as the inserts degrade. b Cross section of ACP screw (A), outer shell (B), and insert (C). Design allows screw head to subside slightly in bone to reduce plate-bone contact