Bone Microarchitecture of the Tibial Plateau in Health and Osteoporosis

AIMS AND OBJECTIVES: A failure rate of up to 69% of surgically treated tibial plateau fractures in the elderly is attributed among others to the increasing incidence of osteoporosis resulting in renewed immobilization and revision surgery. Hence, ideally implants are fixed in regions with sufficient bone mass. However, data on region-specific structural alterations of the tibial plateau in osteoporosis do not exist. The primary aim of the study was to characterize region-specific changes of the bone structure in patients with osteoporosis compared to skeletally healthy controls. MATERIALS AND METHODS: In a preclinical case-control study twenty-one human right proximal tibiae from females with postmenopausal osteoporosis (mean age: 84.3±4.9 years) and eight skeletally healthy, premenopausal female controls (45.5±6.9 years) were harvested during autopsy. Histomorphometric parameters were assessed by HR-pQCT (high-resolution peripheral quantitative computed tomography) after digital subdivision into different volumes of interest (VOI) according to a 10-segment classification in three levels of the tibial plateau. In the coronal plane, analysis was performed in the proximal 3 cm from the articular surface. Statistical analysis was based on evolutionary learning using globally optimal regression trees. RESULTS: Skeletally healthy controls showed a better bone structure throughout the whole tibial plateau than osteoporotic patients. In osteoporosis, the greatest bone loss was found in the medio-medial VOI (antero-medio-medial, postero-medio-medial) compared to controls. The lowest bone volume, however, was found in the central VOI (antero-central, postero-central) representing the tibial spine. Trabecular connectivity was severely reduced. Most importantly, in the anterior and posterior 25% of the lateral and medial tibial plateau, the trabecular support and the subchondral lamella thickness itself was severely reduced. CONCLUSION: The bone structure deterioration of the tibial plateau due to osteoporosis is region-specific. The additional thinning of the subchondral lamella and marked bone loss in the anterior and posterior 25% of the tibial plateau may explain failure of fracture reduction in cases of unilateral plate fixation, specifically in postero-medial fragments. The understanding of region-specific architectural alterations of the tibial plateau may help to improve the long-term, fracture-specific fixation of tibial plateau fractures, especially in osteoporotic patients.