The Hip Joint

K. Mohan Iyer, K. Mohan Iyer

• Publisher: Jenny Stanford Publishing
• Year: 2021
• ISBN:
  9781000376234
• Edition: 2
• Topic: Medicina
• Subtopic: Ortopedia

The Hip Joint, written in 2016, provides a detailed account of the hip joint's anatomy and biomechanics and covers recent trends in orthopaedic surgery of the hip joint, including the latest advances in revision total hip arthroplasty (THA), computer-assisted navigation for THA, resurfacing of the hip joint andneoplastic conditions around the hip as well asindications, complications and outcomes of hip arthroscopy. Another book, The Hip Joint in Adults: Advances and Developments, gives additional important details of how hip joint surgery has evolved around the world. While much of the basic knowledge in this area is constant, it is critically important to stay current on those areas that do change.

This updated second edition of The Hip Joint contains a host of original articles from contributory authors all around the world, showing the evolution of the hip joint till the present day, building upon the solid foundation set by the first edition. It covers hot topics such as 3D printing in orthopaedics and traumatology, stem cell therapy in orthopaedics, hip resurfacing, hip-preserving surgery, sports medicine for the hip joint, robotic-assisted surgery in orthopaedics and neoplastic conditions around the hip.

Chapter 1

Applied Anatomy of the Hip Joint

K. Mohan Iyer

Formerly Locum Consultant Orthopaedic Surgeon, Royal Free Hampstead NHS Trust, Royal Free Hospital, Pond Street, London NW3 2QG, UK
[email protected]

1.1 The Hip Joint

The hip joint is a ball-and-socket type of a synovial joint where the articular surfaces are formed by the head of the femur, which articulates with the acetabulum of the hip bone. It is the largest joint of the body, having a very high degree of mobility and stability, which makes it unique in every way. The articular surface of the acetabulum is of horseshoe shape formed by the pubis ilium and ischium bones and is deficient inferiorly at the acetabular notch. The cavity of the acetabulum is deepened by a fibrocartilaginous rim called the acetabular labrum. Its depth starts at the age of 8, and its depth increases by puberty due to the development of 3 secondary centres of ossification. This labrum bridges across the acetabular notch, where it is called the transverse acetabular ligament. The articular surfaces are covered by hyaline cartilage. The acetabulum allows the proximal transmission of weight from the axial skeleton to the lower extremity.

The femur is the largest bone in the body and consists of the head, neck and two trochanters, greater and lesser. A cross-sectional view of the normal hip joint is shown in Fig. 1.1 [1].

Figure 1.1 Cross-sectional view of the normal hip joint. Figure reproduced by courtesy of Byrne et al. [1].

It has been observed that labral tears are most likely to occur at the junction of the labrum and articular cartilage; this area has been termed the ‘watershed’ region [2].

The head of the femur is covered with hyaline cartilage except at the fovea capitalis, which serves at the attachment of the ligamentum teres. The femoral neck is externally rotated with respect to the shaft, thus forming the angle of anteversion. In normal adults the neck forms an angle of 135° with the shaft. The normal angle is 120° to 135°. In coxa valga, the angle is >135° while in coxa vara it is <120° (Fig. 1.2).

Figure 1.2(a) Normal femoral neck angle, (b) decreased femoral neck angle (coxa vara), and (c) increased femoral neck angle (coxa valga). Figure reproduced by courtesy of Byrne et al. [1].

• The capsule is a cylindrical sleeve which extends from the pelvis proximally to the intertrochanteric line anteriorly distally. Laterally, the acetabular labrum extends to the femoral head, while posteriorly it extends to the neck of the femur just 1 cm medial to the intertrochanteric crest. The articular labrum and the capsule are thicker antrosuperiorly, while being thinner posteroinferiorly. This capsule has circular and longitudinal fibres. The circular fibres form a collar around the neck to be called as zona orbicularis, while the longitudinal fibres travel along the neck and carry the blood vessels. At its attachment to the intertrochanteric line anteriorly, blood vessels are reflected upwards along the neck as bands called retinacula, which supply the head and neck of the femur.
• The synovial membrane lines the capsule and is attached to the margins of the articular surfaces. It ensheaths the ligament of the head of the femur and covers the pad of fat in the acetabular fossa.
• The psoas bursa is formed by a pouch of synovial membrane which protrudes through a gap in the anterior wall of the capsule between the pubofemoral and iliofemoral ligaments to form the psoas bursa beneath the psoas tendon.

1.2 Ligaments of the Hip Joint

These can be classified as follows:

• Intra-articular:
  • The ligamentum teres
  • The transverse acetabular ligament
  • The acetabular labrum
• Extra-articular:
  • The iliofemoral ligament (the Y ligament of Bigelow) is the strongest, inverted Y-shaped ligament, with its base attached to the anterior inferior iliac spine above and below by its two limbs to the upper and lower parts of the intertrochanteric line of the femur. This strong ligament prevents over-extension during standing.
  • The pubofemoral ligament is triangular, with its base attached to the superior pubic ramus of the pubis and the apex attached to the lower part of the intertrochanteric line. This ligament limits extension and abduction.
  • The ischiofemoral ligament is a spiral-shaped ligament attached to the body of the ischium near the acetabular margin. The fibres then pass upwards and laterally to the greater trochanter to blend with the zona orbicularis, and they limit extension. It tightens with internal rotation and is the more commonly injured ligament than the other ligaments.
    The ligamentum teres is a round, flat, triangular ligament which is also called the round ligament. Its apex is attached to the fovea capitis and its base to the transverse ligament and margins of the acetabular notch. It functions in transmitting arteries to the head of the femur (acetabular branches of the obturator and medial circumflex femoral arteries). It tightens during adduction, flexion and external rotation and thus prevents subluxation of the femoral head superiorly and laterally in adduction and external rotation movements of the hip joint.
• The transverse acetabular ligament is formed by the acetabular labrum as it bridges the acetabular notch. It thus converts the notch into a tunnel through which the arteries and nerves pass to enter into the joint.
• The ligament of the head of the femur is flat and triangular attached by its apex to the pit on the head of the femur (fovea capitalis) and by its base to the transverse ligament and the margins of the acetabular notch. It lies within the joint and is ensheathed by the synovial membrane.
• The acetabular labrum is made up mostly of type I collagen fibres, which narrows the mouth of the acetabulam and helps in holding the head of the femur in position. It provides stability by creating negative intra-articular pressure in the hip joint, thereby improving mobility by providing an elastic alternative to the bony rim.

Femoral triangle: The superior border is the inguinal ligament, the lateral border is the sartotius muscle and the medial border is the adductor longus muscle.

1.3 Movements of the Hip Joint

Table 1.1 shows the various muscles involved in movements of the hip joint.

Table 1.1 Muscles producing movements of the hip joint

Movements	Main muscles	Accessory muscles
Flexion	Psoas major and iliacus	Pectineus, rectus femoris, sartorius and adductor longus
Extension	Gluteus maximus, biceps femoris, semimembranosus and semitendinosis	Gluteus medius
Adduction	Adductor longus, brevis and magnus	Pectineus and gracilis
Abduction	Gluteus medius and minimus and tensor fasciae latae	Sartorius, piriformis
Medial rotation	Tensor fasciae latae and anterior fibres of the gluteus medius and minimus	Adductor longus brevis and pectineus
Lateral rotation	Obturator externus, internus, gamellus superior, gamelus inferior, quadratus femoris, gluteus maximus, sartorius	Piriformis, biceps femoris

Flexion is a movement in which the head of the femur rotates along a transverse axis which passes through both the acetabula and which is limited by the thigh touching the abdomen and is 120°. This is mainly due to the contraction of the iliopsoas muscles with the help of the sartorius, rectus femoris and pectineus muscles.

Extension rotates around the transverse axis with a range of 20°, which is limited by the tension of the iliofemoral ligament. It is mainly due to the gluteus maximus muscles with the help of the hamstrings.

Flexion and extension occur around a transverse...