Bone Plate Fixation: Its Relationship with Implant Induced Osteoporosis

Abstract

SummaryThe use of internal fixation devices for fracture repair induces profound changes in the affected bone. The factors implicated in the development of implant induced osteoporosis have been extensively studied. The processes following bone plate fixation which results in vascular and structural changes to the bone have not been accurately described. There are many inconsistencies in the design of experimental studies and in data interpretation which confound the issue.Implant induced osteoporosis appears to be a biphasic phenomenon following the application of rigid internal fixation, with an early-onset osteonecrosis (8-12 weeks) elicited through cortical vascular insufficiency, followed by osteoporosis (24-36 weeks) induced by stress redistribution.The development of implant induced osteoporosis appears to involve mechanical factors (surgical trauma, screw placement, rigidity of the fixation device), acting in conjunction with vascular insufficiencies related to the bone-plate interface contact area and pressure distribution.Whatever the pathogenesis, the end result is a thinning of the diaphyseal cortices. Should implant removal be deemed necessary such osteoporosis is a cause for concern in view of the bones predisposition to refracture following plate removal. The degree of cortical osteoporosis observed appears to be time-dependent following internal fixaton and as such the clinical outcomes, after implant removal, are also related to the timing of removal.Numerous factors have been implicated in the development of the vascular and structural changes that follow the plating of bone. It appears that implant induced osteoporosis has a multifactorial pathogenesis involving surgical trauma, screw placement and the rigidity of the fixation device. Elements involved in the interface between plate and bone, such as interface contact area and pressure, are also implicated in the pathogenesis.

Prospective Randomized Clinical and Radiographic Evaluation of a Novel Bioabsorbable Biocomposite Tibial Tuberosity Advancement Cage Implant

“…However, elective surgery to remove these implants is a significant source of patient morbidity and has a massive economic impact. The latter may explain why elective removal of implants is less commonly performed in veterinary patients even though the same implant‐related issues can and do occur . Removal is typically reserved for when an implant‐associated problem has already occurred.…”

Changes of Biomechanical Characteristics of the Bone in Experimental Tibial Osteotomy Model in the Dog.

“…On the contrary, biomechanical disadvantages of intramedullary pins include poor resistance to compressive or rotational loads and lack of fixation with bone [8]. In the field of orthopedics, it has been widely recognized that some situation in which the bone is protected from the mechanical stress, including the rigid plate fixation for fracture or immobilization of the limb, decrease the mechanical strength of the bone, and called as stress-shielding phenomenon [5,9,11,12,17,18]. In the present study, osteotomized area of the tibia had been protected from bending loads by the intramedullary pin during the observational period.…”

Highly Comminuted, Articular Fractures of the Distal Antebrachium Managed by Pancarpal Arthrodesis in 8 Dogs

“…An ex vivo biomechanical study using a long bone fracture model concluded that orthogonal plate constructs were significantly stiffer in lateromedial bending and failed at a higher axial compressive load than pin‐plate constructs . Stiff fixation systems may result in stress shielding and development of osteoporotic bone with longer healing times, but no evidence of this was identified in the dogs of this report. The clinical use of orthogonal plates for either long bone fracture repair or arthrodesis has not been reported in the peer‐reviewed literature.…”