Role of cortical bone in hip fracture

Abstract

In this review, I consider the varied mechanisms in cortical bone that help preserve its integrity and how they deteriorate with aging. Aging affects cortical bone in two ways: extrinsically through its effects on the individual that modify its mechanical loading experience and 'milieu interieur'; and intrinsically through the prolonged cycle of remodelling and renewal extending to an estimated 20 years in the proximal femur. Healthy femoral cortex incorporates multiple mechanisms that help prevent fracture. These have been described at multiple length scales from the individual bone mineral crystal to the scale of the femur itself and appear to operate hierarchically. Each cortical bone fracture begins as a sub-microscopic crack that enlarges under mechanical load, for example, that imposed by a fall. In these conditions, a crack will enlarge explosively unless the cortical bone is intrinsically tough (the opposite of brittle). Toughness leads to microscopic crack deflection and bridging and may be increased by adequate regulation of both mineral crystal size and the heterogeneity of mineral and matrix phases. The role of osteocytes in optimising toughness is beginning to be worked out; but many osteocytes die in situ without triggering bone renewal over a 20-year cycle, with potential for increasing brittleness. Furthermore, the superolateral cortex of the proximal femur thins progressively during life, so increasing the risk of buckling during a fall. Besides preserving or increasing hip BMD, pharmaceutical treatments have class-specific effects on the toughness of cortical bone, although dietary and exercise-based interventions show early promise.

Biomechanics of Osteoporotic Fracture Fixation

“…Thus, due to cortical thinning and trabecular bone loss, the femoral neck in particular loses strength and becomes susceptible to fracture. Similarly, as the lateral cortex of the trochanter becomes thinner during aging, it has a higher potential to buckle during a fall impacting the hip [16].…”

“…While there is a general consensus on treatment of stable fractures (A1, A2), the best way to treat unstable fractures remains controversial [17]. Simple trochanteric fractures are treated by extra-or intramedullary devices [16,22], mostly sliding hip screws and cephalo-medullary nails. While it appears that the use of cephalo-medullary nails is becoming more and more popular, there is no clear clinical evidence on the superiority of any surgical treatment method yet available [23].…”

Is Primary Fixation with the Sliding Hip Screw Introduced into the Non-ideal Position Sufficient for Stable Pertrochanteric Fracture Stabilisation? A Biomechanical Evaluation and Experimental Study

“…From the anatomical point of view, the exact reduction of the posteromedial cortical bone wall, also called the Adams arch, is crucial for the healing process of a stable pertrochanteric fracture. After appropriate anatomical reduction, the implant (SHS) helps maintain the fragments in this position until the healing process is sufficient and the bone can take charge of load bearing [12]. This time is thought to be a minimum of 6 weeks.…”

Association of Decreased Handgrip Strength with Reduced Cortical Thickness in Japanese Female Patients with Type 2 Diabetes Mellitus

“…It is known that cortical bone components play important roles in maintaining the axial load bearing capacity of long bones 29 , 30 , thus the amplitude of mechanical load on a long bone, which is mainly composed of cortical bone components, might determine its strength 31 , 32 . A previous study that utilized HR-pQCT demonstrated that impaired cortical bone components in particular increased cortical porosity and are responsible for fragility fractures in postmenopausal T2DM females 9 .…”