![]() N., nerve ant., anterior inf., inferior sup., superior post., posterior quad., quadratus obtur., obturator. Table 2.1 Muscles of the Hip Joint: Muscle Group Actions and Innervations Most of the capsular fibers of are longitudinally orientated as they traverse from the pelvis to the femur,Įxcept for the circular fibers of the zona orbicularis located posteriorly and inferiorly ( Fig. The femoral neck is thus intracapsular anteriorly, but posteriorly the basicervical portion and intertrochanteric crest are extracapsular. Running distally the capsule attaches anteriorly to the femur along the intertrochanteric line, but has an arched free border that results in only partial covering of the femoral neck posteriorly ( Fig. Inferiorly, the capsule is attached to the transverse acetabular ligament. Making anterior and posterior incisions between the capsule and labrum allow retractors to be placed safely over the anterior and posterior columns. The capsule attaches along the anterior and posterior periphery of the acetabulum just outside the acetabular labrum. The articular capsule of the hip is strong and dense, contributing substantially to joint stability ( Fig. 2.3) can be used to locate the safe and dangerous zones for the transacetabular placement of screws but they also can be used as a guide for retractor placement, for drilling acetabular anchoring holes for graft fixation, or to estimate bone depth in a specific acetabular zone. The anatomic and high hip center (HHC) quadrant systems ( Fig. If this line is then bisected with a perpendicular at its midpoint, four quadrants are formed. For primary or revision acetabular arthroplasty, a line drawn from the ASIS through the center of the acetabulum defines anterior and posterior quadrant locations. Use of this system allows the surgeon to know the location of intrapelvic structures with respect to fixed points of reference within the acetabulum. The acetabular anatomy and surrounding nerves and vessels can be easily understood by using the acetabular quadrant system ( 4). The nerves and vessels that course around the acetabulum and proximal femur are demonstrated in this and many other anatomy and surgery texts ( 4, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28). The influence of bone quality on successful hip replacement is presently being determined ( 17, 18). Trabeculae are removed with the required neck resection for removal of the femoral head at arthroplasty, this osteopenia measurement is likely less important than the quality of bone against the ingrowth surface. ( 16) have created an index to grade the loss of trabeculae that occurs with osteopenia. The ability of these indexes to predict the success of cementless femoral implants is still being elucidated. Patients with stovepipe configurations may require more porous surface on their femoral implants to adequately contact the endosteal femoral surface, or a cemented implant may be considered. As the canal calcar isthmus ratio (the Dorr index) approaches 1, prosthesis fill proximally and distally is compromised. The Dorr index is a ratio of the canal diameter at the level of the lesser trochanter to the canal diameter at a point 10 cm distal ( Fig. Because these different configurations affect the ability of the porous coating of a particular implant to be adequately apposed to subchondral bone, Dorr ( 14) and Spotorno ( 15) have developed indexes to characterize proximal femoral configuration. The proximal femur of younger patients tends to have a trumpetlike or champagne-fluted configuration. Endosteal expansion of the isthmus with age results in the stovepipe femoral configuration ( 12, 13). The proximal endosteal femoral geometry is demonstrated adequately for surgical planning on preoperative radiographs. Not only must cementless stems fit the anterior–posterior and medial–lateral dimensions of the canal, they also need to maximize the endosteal contact down the length of their porous coating. The canal configuration may create problems for a cementless stem with fixed proximal geometries. It is not until the neck cut is made during femoral arthroplasty that this geometry is best appreciated and assessed. Although internal dimensions tend to correlate with one another, it is impossible to predict which configuration is present unless CT scans of the proximal femur are obtained prior to surgery. The proximal femoral metaphyseal orientation and shape have great variability ( 7, 8, 9, 10, 11).
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