Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
Core Procedures
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Open reduction internal fixation of acetabular fractures; open reduction internal fixation of femoral head and neck fractures
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Closed reduction screw fixation of femoral neck fractures
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Arthroplasty, hemiarthroplasty
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Osteotomies of the pelvis; osteotomies of the neck of the femur and proximal femur
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Closed and open reduction of hip dislocation
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Hip joint arthroscopy
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Arthrocentesis; diagnostic and therapeutic injections of the hip joint and other extra-articular musculotendinous structures
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Irrigation and debridement of the hip joint
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Paediatric hip joint: pinning for slipped capital femoral epiphysis; osteotomy, epiphysiodesis and arthrodiastasis for Legg–Calvé–Perthes disease
Embryology
In utero , the hip is formed from a condensation of mesenchyme in the lower limb bud, which differentiates until week 20, before maturation starts. After birth, the acetabulum is formed from the coordinated growth of the Y-shaped triradiate cartilage that will eventually form the depths of the acetabulum, and the saucer-shaped acetabular cartilage that will form the articular rim. The shape of the acetabulum is mostly determined by the age of 8 years, but growth continues through ossification centres that appear at 8 or 9 years and fuse by the age of 17 or 18. The ossification process in the proximal femur reaches the greater trochanter and the neck of the femur by birth. The cartilage that is not ossified contains three growth plates responsible for the longitudinal growth of the proximal femur and for its shape. The lack of appropriate contact pressure between the acetabulum and the proximal femur during growth results in an incongruent joint.
Surgical surface anatomy
Bony landmarks important for approaches to the hip joint include the iliac crest, anterior superior iliac spine (ASIS), posterior superior iliac spine (PSIS), anterior inferior iliac spine (AIIS), posterior inferior iliac spine (PIIS), body of pubis and pubic symphysis, ischial tuberosity and greater trochanter. A point just inferior and lateral to the midpoint of the inguinal ligament marks the position of the hip joint. Posteriorly, the greater sciatic foramen is approximated on a line made between the ischial tuberosity and PSIS. The femoral artery is just medial to the femoral nerve and both enter the thigh inferiorly at about the midpoint of the inguinal ligament ( 
).
Clinical anatomy
The hip joint is a constrained enarthrodial joint. The cartilage covering the head of the femur is thickest at the centre and thinner at the equator, the opposite being true for the cartilage lining the acetabulum. The acetabular cartilage is horseshoe-shaped, open inferiorly at the acetabular notch; a central cavity, the acetabular fossa, is occupied by synovium-covered fat over which the ligament of the head of the femur (ligamentum teres) can glide. The transverse acetabular ligament bridges the notch, defining a passageway through which the nutrient vessels enter the joint. Three extra-articular ligaments reinforce the capsule and are intimately connected to it. The iliofemoral ligament (Y-shaped ligament of Bigelow), between the intertrochanteric line and the inferior portion of the AIIS, is the strongest ligament in the human body. The pubofemoral ligament, which is attached to the obturator crest and the superior pubic ramus, blends into it. Posteriorly, the ischiofemoral ligament (ligament of Bertin) consists of a triangular band of fibres between the ischium and the intertrochanteric line. The hip joint is stable by virtue of its geometry. Its congruence is augmented by the acetabular labrum, a fibrocartilaginous gasket that is also believed to function as a suction seal, preventing synovial fluid from leaving the joint space. The neurovascular anatomy and the muscles of the hip are described in Chapter 79 .
Biomechanics of the hip
The hip is the most proximal joint that connects the axial skeleton to the lower limb. It plays an essential role in posture, balance and movement, including gait. Pelvic tilt maintains the sagittal alignment of the spine. It occurs mainly at the hip joint, which acts as a fulcrum between the force of body weight and the force of contraction of the abductors of the hip ; these forces result in an equal and opposite joint reaction force at the hip. Measurements in vivo have shown that this force equals 2.3–2.9 times body weight during monopodal stance; 1.6–3.3 times body weight when walking; and around 5 times body weight during running or ascending and descending stairs. To maintain a stable hip, the torque produced by body weight is countered by the contraction of gluteus medius and gluteus minimus. Weakness of these muscles can lead to gait abnormalities (Trendelenburg, Duchenne and waddling gaits). Weakness of gluteus maximus can also result in gait imbalance (maximus lurch), as does muscle spasticity (circumductory, scissoring, paralytic and quadriplegic patterns).
The bony geometry of the joint is also essential for determining the arc of motion and the stability of the hip. When surgery around the hip is planned, it is essential to understand the biomechanics at play and to restore function through muscle balance and optimal geometry. Some of the key elements to consider are described in Fig. 80.1 .
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