Trabecular Pattern of the Proximal Femur

Courtesy: Prof Nabil Ebraheim, University of Toledo, Ohio, USA

TRABECULAR PATTERN OF THE PROXIMAL FEMUR

• There are important trabecular patterns in the proximal femur.
• It occurs according to Wolff’s Law in response of the bone to stress.
• There is a primary tensile trabeculae and a primary compression trabeculae.
• There also are secondary tensile and compression trabeculae.
• In between them is what is known as the Ward triangle(very weak, empty area, not full of trabeculae). This trabecular pattern is seriously affected by osteoporosis.
• The tensile forces can create micro fractures or stress fractures at the superior neck in response to repeated loads.
• Adult bone is weak in tension.
• Stress fracture in this area will propagate and will become complete.
• Early identification and treatment by fixation of this stress fracture is important.
• Otherwise, the fracture will become complete.
• It may become displaced and may be hard to treat.
• The tip apex distance is important when treating hip fractures with compression hip screws.
• This is because the screw will be imbedded into an area where the tensile trabeculae and compression trabeculae cross each other(it is more dense area that contains more bone).
• The failure rate of the fixation is less if the tip apex distance is less than 2.5cm.
• The lateral cortex of femur is importantly because, in this area, the trabeculae present is secondary tensile trabeculae(this area is weak and can easily be affected by fractures).
• Integrity of lateral wall is important in order to achieve stable fixation and lessen the rate of revision of fixation.
• If the lateral wall integrity is compromised by a fracture or by deficiency, then the surgeon should select an intramedullary nail rather than a compression hip screw.
• In the case of hip fracture and osteoporosis, it is advisable to insert the screws posteriorly and inferiorly, because the trabecular pattern is more dense in this area.