Introduction:
The calcaneus bone is the largest and one of the seven talus bones forming the foot. The calcaneus bone is divided into two surfaces, the anterior and posterior. Bohler angle is the line present in the side of the foot, forming an angle between the high point on the anterior surface to the articulating region on the posterior surface. Bohler angle is called so as it was named after the Australian surgeon Lorenz Bohler, who is considered the father of traumatology. It is also known as a calcaneal angle, tubular joint angle, or tuber angle and is used for assessing calcaneal fractures and normal foot level. The normal value of Bohler angle is between twenty-five degrees to forty degrees.
What Are the Structures Related to Bohler Angle?
The following are the structures related to Bohler angle:
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The Talus: The talus bone is a part of the foot that forms the base of the ankle and is placed above the calcaneus bone. It is the main connecting bone between the foot and the leg. The talus and the calcaneal bone together form the subtalar joint. The functions of the talus bone include bearing the weight of the body, helping in ankle rotation, and movement of the foot.
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The Calcaneus: Calcaneus is the largest of the seven-foot bones called the tarsal bones, whose function is to withstand body weight. Calcaneus bone is present at the junction where the tibia, fibula, and talus bone articulate. The functions of the calcaneal bone include flexion of the muscles of the foot, stretching the foot, stabilizing the ankle joint, and maintaining proper gait and posture.
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Subtalar Joint: The subtalar joint is the joint of the back foot or ankle where the two bones (the talus and calcaneus) are joined together by the interosseous talocalcaneal ligament. The joint structure and function appear to be like a synovial joint. It helps in the stability and movement of the body.
What Is the Normal Bohler Angle?
Although there is a vast difference among the foot shape of the individuals, the normal Bohler angle ranges from twenty-five degrees to forty degrees. A slight decrease in Bohler angle is also considered. But a normal Bohler angle does not always prove the absence of calcaneal fracture.
How Is Bohler Angle Interpreted?
Bohler angle is interpreted by intersecting two lines where one line is drawn along the highest point of the bone, and a second line is drawn from the point of attachment in the highest point on the posterior surface of the calcaneal bone. Bohler angle helps to decide the treatment plan and the outcome and prognosis. The Bohler angle appears to be depressed in the fracture of the calcaneus bone.
Lines of Intersection: Two lines of intersection form the angle, and the lines made are:
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Line 1 - It is made by point 1, which connects the highest point of the calcaneus bone to point 2, which is the highest point in the posterior facet articulating the surface of the calcaneus bone.
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Line 2 - It is made by connecting points 2 and 3, where point 2 is the highest point on the posterior articulating surface, and point 3 is the lowest in the calcaneus bone.
The difference in Bohler angles shows no variation in gender or sides of the leg.
What Are the Types of Bohler Angles?
Based on the degree of angulation, Bohler angle is divided into three types:
Positive Bohler Angle: This type of angle is said to occur when the degree is around thirteen to eighteen.
Normal Bohler Angle: The normal or the most average angle value is between twenty to forty degrees.
Negative Bohler Angle: A negative angle is when the degree of displacement is more than forty degrees.
How Is a Variation in the Bohler Angle Treated?
The variation in Bohler angle indicates a discrepancy in the talus and calcaneus bone structure. In cases with minor positive deformities, it is considered normal or corrected with non-surgical management like immobilization. While in cases of major negative deformity, surgical management is preferred for correction. The occurred deformity of the calcaneus bone is treated surgically and shortened to manage the difference in the angle. The average value of difference corrected during surgery is around 5.2 degrees.
How Is Bohler Angle Assessed?
Bohler angle is assessed using the following imaging techniques, and they are:
Radiographs (X-Rays): These are two-dimensional (2D) imaging techniques used to study bony structures or identify fractures or displacements. The radiographs taken here are used to check the degree of Bohler angle, the calcaneus bone fracture line, and the displacement angle. In the X-ray, Bohler angle is seen as the distance between the high points on the foot with an imaginary line intersecting it.
What Are the Uses of Bohler Angle?
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Achieve the articular correlation.
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Determine the presence or absence of fracture.
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Decide on the treatment plan.
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Determine the level of angle that is corrected.
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Decide the prognosis of the treatment.
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Used to repair the height of the calcaneus within the acceptable normal range.
Conclusion:
Bohler angle is a very important marker for determining calcaneus fracture. But it is often measured along with other angles of the foot while deciding for surgical correction of the difference in Bohler angle. The average value of Bohler angle shows an excellent prognosis. The corrective surgeries performed to resolve the differentiation also gives great outcome, balancing the structure of the calcaneus and establishing normal gait, balance, and posture.
