Intracapsular fractures of the hip.

Abstract

The proximal femoral epiphysis generally is closed by the age of sixteen years, thus establishing the anatomy of the proximal part of the femur in an adult [34]. The neck-shaft angle in adults does not seem to vary substantially between the sexes and is approximately 130 +-\7 degrees (mean and standard deviation) [78]. The femoral neck is normally anteverted with respect to the femoral shaft, and this anteversion has been measured as 10 +-\7 degrees in normal specimens; again, there is no difference between the sexes [77]. Proximal femoral anteversion does not change after skeletal maturity. The diameter of the femoral head varies according to the size of the individual and ranges from forty to sixty millimeters [44]. Hoaglund and Low measured the thickness of the articular cartilage covering the femoral head and found that it averages four millimeters at the superior portion and tapers to three millimeters at the periphery [44]. A synovial membrane covers the entire femoral neck anteriorly but only the proximal half posteriorly [111]. The lengths and shapes of femoral necks vary widely. There is a large posterior overhang of the greater trochanter. Thus, the femoral neck appears to lie wholly anterior to the mid-axis of the proximal part of the femur when viewed from a lateral location; a surgeon must recognize this relationship in order to place an internal fixation device accurately. The calcar femorale is a dense vertical plate of bone that originates from the posteromedial portion of the femoral shaft, radiates superiorly toward the greater trochanter, and fuses with the posterior cortex of the femoral neck [114]. In the literature regarding hip arthroplasty, the medial cortex of the femoral neck has frequently been mistakenly labeled as the calcar. As pointed out by Harty [42], and later by Griffin [39], this structure plays a central role in the development of patterns of fracture of the proximal part of the femur. Trueta and Harrison [109] expanded on the work of Howe et al [50], by using injection techniques to study the vascular anatomy of the proximal aspect of the femur. The lateral epiphyseal artery, which is the terminal branch of the medial femoral circumflex artery (from the profunda femoris artery), supplies most of the femoral head. In fifteen high-quality studies performed with injection of a barium suspension into fifteen-micrometer sections that were then studied with light microscopy, Trueta and Harrison found that the lateral epiphyseal artery supplied four-fifths of the femoral head in seven subjects, two-thirds in another seven, and slightly more than half in one. The inferior metaphyseal vessel--the terminal artery of the ascending branch of the lateral femoral circumflex artery--pierces the mid-portion of the anterior part of the capsule of the hip. Trueta and Harrison reported that this vessel supplied the more distal metaphyseal bone anteriorly and inferiorly in two-thirds of their subjects. The third major blood supply of the femoral head is the artery of the ligamentum teres, from the obturator arterial system. This vessel generally anastomoses with the system of the lateral epiphyseal artery [9,19]. This anastomotic system formed by the lateral epiphyseal artery and the artery of the ligamentum teres may play a role in the revascularization of the femoral head after a fracture of the femoral neck. I found no evidence, in several other injection studies [19,41,84,109], that the metaphyseal vessels that extend proximally from the nutrient artery supply any nutrition to the proximal part of the femoral neck or to the femoral head.