Osteology Flashcards
Why is the femoral neck a common site of fracture, especially in elderly?
The femoral neck is a common site of fracture, particularly in the elderly, due to the following reasons:
1. Anatomical Location:
• The femoral neck is located at the junction of the femoral head and the shaft of the femur, making it a region of the bone that is under significant shear stress and torsional forces during weight-bearing activities.
2. Bone Fragility in the Elderly:
• In elderly individuals, osteoporosis (loss of bone density) weakens the bones, making the femoral neck more susceptible to fractures, even with minimal trauma, such as a fall.
3. Less Bone Support:
• The femoral neck is a relatively thin and angled bone compared to other parts of the femur, making it prone to fractures under stress. In addition, the blood supply to the femoral neck is limited, increasing the risk of complications like avascular necrosis after a fracture.
4. Falls and Impact:
• The most common mechanism of injury is a fall onto the hip, which is particularly common in the elderly due to balance issues and muscle weakness.
What is the angle of inclination of the femur and how does it change with age?
The angle of inclination of the femur (around 125 degrees) is crucial for hip joint alignment and efficient force distribution during movement. With age, it can increase (coxa valga), reducing stability, or decrease (coxa vara), leading to joint wear and osteoarthritis. These changes affect hip function and risk of fractures.
Explain why Patella is prone to dislocation laterally.
The patella is prone to lateral dislocation due to a shallow femoral trochlea, weaker medial ligaments (like the MPFL), and an increased Q-angle, which directs more force laterally on the patella. These factors make lateral dislocation more likely, especially with trauma or muscle imbalances.
Why is the tibia more likely to fracture than fibula?
The tibia is more likely to fracture than the fibula because:
1. Weight-Bearing Role: The tibia is the main weight-bearing bone in the lower leg, while the fibula is primarily for support and stability, carrying less load.
2. Location: The tibia is located more medially and is more exposed to direct trauma compared to the fibula, which lies on the outer side and is less vulnerable.
3. Bone Strength: The tibia is larger and stronger than the fibula, but because it bears most of the body’s weight, it is more prone to fractures under stress or impact.
Functional importance of interosseous membrane between tibia and fibula.
The interosseous membrane between the tibia and fibula has several important functions:
1. Stabilization: It helps stabilize the tibia and fibula, preventing them from shifting relative to each other during movement.
2. Force Distribution: The membrane distributes forces from the tibia (which bears the body’s weight) to the fibula, helping reduce the load on the tibia and enhancing overall stability.
3. Muscle Attachment: It provides attachment points for muscles, such as the flexor muscles of the lower leg, contributing to efficient movement.
4. Prevents Excessive Movement: It limits excessive movement between the tibia and fibula, maintaining structural integrity during activities like walking and running.
Why is the medial malleolus more commonly fractured compared to the lateral malleolus?
The medial malleolus is more commonly fractured than the lateral malleolus because:
1. Anatomical Position: The medial malleolus (on the inside of the ankle) is more exposed and prone to impact or direct trauma, whereas the lateral malleolus is better protected by the fibula and lies more laterally.
2. Bony Structure: The medial malleolus is thinner and more fragile compared to the lateral malleolus, making it more susceptible to fractures in cases of twisting or ankle sprains.
3. Foot Position: During inversion injuries (foot turned inward), the medial malleolus is at greater risk of fracturing as the lateral ligaments of the ankle often tear first.
Explain anatomical basis of ovascular necrosis of the femoral head in posterior hip dislocations.
Avascular necrosis (AVN) of the femoral head in posterior hip dislocations occurs due to damage to the blood supply to the femoral head. The anatomical basis is:
1. Disruption of the Blood Supply: The femoral head primarily receives blood from the medial circumflex femoral artery, which enters the femoral neck. In a posterior hip dislocation, this blood supply can be disrupted, particularly when the femoral neck is displaced or fractured.
2. Vessel Tension: The posterior dislocation may stretch or tear the vessels, especially the posterior femoral circumflex artery, leading to a loss of circulation to the femoral head.
3. Ischemia: Without adequate blood flow, the femoral head becomes ischemic, leading to bone death (AVN), which can cause pain, collapse, and long-term disability if untreated.
Summary:
In posterior hip dislocations, the medial circumflex femoral artery is often damaged, leading to impaired blood flow to the femoral head and resulting in avascular necrosis.
Significance of the greater and lesser trochanters of the femur in muscle attachment
The greater and lesser trochanters of the femur serve as important sites for muscle attachment:
1. Greater Trochanter:
• Provides attachment for muscles involved in hip abduction, lateral rotation, and stabilization of the hip joint, such as the gluteus medius, gluteus minimus, and piriformis.
2. Lesser Trochanter:
• Serves as the attachment point for the iliopsoas muscle, which is a primary muscle responsible for hip flexion.
Summary:
The greater trochanter is for muscles controlling abduction and rotation, while the lesser trochanter is for the iliopsoas muscle, which aids in hip flexion.
Why is the talus prone to ovascular necrosis after fractures?
The talus is prone to avascular necrosis (AVN) after fractures due to the following reasons:
1. Limited Blood Supply: The talus has a limited blood supply, mainly from the posterior tibial artery and the dorsalis pedis artery. These vessels enter the bone at narrow points, making it vulnerable to disruption during fractures.
2. Disruption of Blood Flow: In a talus fracture, especially in the neck of the talus, the blood vessels supplying the bone can be damaged or compressed, leading to impaired circulation.
3. No Muscular or Soft Tissue Coverage: Unlike other bones, the talus has minimal soft tissue and muscular attachments to help maintain its blood supply, making it more susceptible to ischemia after injury.
Summary:
The talus is prone to avascular necrosis after fractures due to its limited blood supply, especially to the neck of the talus, which can be easily disrupted.
Anatomical importance of the calcaneal tuberosity in weight-bearing.
The calcaneal tuberosity is anatomically significant in weight-bearing due to the following reasons:
1. Primary Weight-Bearing Point: The calcaneal tuberosity is the largest bony prominence of the calcaneus (heel bone) and serves as the main point of contact with the ground during standing and walking, supporting the body’s weight.
2. Attachment for Tendons: It serves as the attachment site for the Achilles tendon, which is crucial for plantar flexion and propelling the body forward during walking, running, and jumping.
3. Distribution of Forces: The calcaneal tuberosity helps in the efficient distribution of forces during weight-bearing activities by transferring the load from the foot to the rest of the lower limb.
Summary:
The calcaneal tuberosity is crucial in weight-bearing as it provides the primary contact point for the ground, supports body weight, and facilitates movement through the attachment of the Achilles tendon.
Why is the acetabulum considered a deep and stable circuit compared to the glenoid cavity?
The acetabulum is considered a deeper and more stable socket compared to the glenoid cavity for the following reasons:
1. Depth and Orientation: The acetabulum is deeper and has a more concave shape, providing a more secure fit for the femoral head. In contrast, the glenoid cavity is shallower, allowing greater mobility but at the cost of stability.
2. Labrum and Ligaments: The acetabulum is reinforced by a stronger acetabular labrum and ligaments (like the iliofemoral ligament), which enhance its stability by preventing dislocation. The glenoid labrum, although important for stability, is less robust compared to the acetabulum.
3. Bony Structure: The acetabulum is more encompassing around the femoral head, whereas the glenoid cavity has less bony support and relies more on soft tissues for joint stability.
Summary:
The acetabulum is deeper and more enclosed around the femoral head, with stronger ligamentous support, making it more stable than the shallower, less enclosed glenoid cavity.
How does the fracture of metatarsals contribute to the arches of foot?
Fractures of the metatarsals can affect the arches of the foot in the following ways:
1. Disruption of the Medial Longitudinal Arch: Fractures, particularly of the first and second metatarsals, can weaken the medial longitudinal arch, which is primarily responsible for weight distribution and shock absorption. This can lead to flatfoot or loss of the arch’s normal height.
2. Altered Load Distribution: When a metatarsal is fractured, the load-bearing function of that bone is compromised, which can shift the weight to other parts of the foot, disrupting the balance and alignment of the arches, especially the transverse arch.
3. Impaired Function of Foot Muscles: Metatarsal fractures can affect the attachment points of muscles that help support the arches, such as the tibialis posterior and flexor hallucis longus, leading to instability in the arches.
Summary:
Fractures of the metatarsals can weaken the foot arches by disrupting normal load distribution and affecting the function of muscles that support the arches, potentially leading to flattening or altered foot mechanics.
