Introduction

The hip is a ball and socket synovial joint between the pelvis and femur (Fig. 2.1). The acetabulum is formed by the fusion of the triradiate cartilage between the three ossification centres of the pelvis: ilium, ischium and pubis. It is further deepened by the labrum and surrounded by a strong capsule with three ligamentous condensations (iliofemoral, ischiofemoral and pubofemoral ligaments) (Fig. 2.1). The iliofemoral ligament in particular is one of the strongest ligaments in the body and is tight in hip extension to reduce energy expenditure during stance. The acetabulum is anteverted 15° and covers the femoral head at an angle of 45°. An important landmark in elective practice is the transverse acetabular ligament, which represents the inferior portion of the acetabular labrum. It has a constant alignment in nondysplastic hips and can provide a useful guide to acetabular implant orientation (Table 2.1).

The femoral head is predominantly covered with a cartilage cap to permit a large range of movement. The hip capsule attaches anteriorly along the intertrochanteric crest and posteriorly part way up the femoral neck. The blood supply to the femoral head penetrates through the capsular attachment, which is important in hip pathology such as femoral neck fracture or avascular necrosis. In the adult the blood supply is predominantly through the medial femoral circumflex artery, which reaches the capsule through the quadratus muscle and must be protected during joint preserving surgery through a posterior approach. The normal femoral neck is anteverted 15° with a neck-shaft angle of 125°. The greater and lesser trochanters are bony protuberances from the proximal femur that permit numerous muscle attachments around the proximal femur, predominantly from muscles originating around the pelvis.

Adult Manifestations of Hip Dysplasia

Clinical Summary

Developmental dysplasia of the hip in childhood (Chapter 10) can result in long-term acetabular and/or femoral anatomical abnormalities. The presence of dysplastic features on imaging is associated with a four-fold increase in the development of osteoarthritis. Dysplasia can affect both the acetabulum and femur.

A reduced joint contact area is responsible for point loading and reduced lubrication. This culminates in loading and accelerated chondral and labral damage. Patients commonly present with onset of symptoms in their third to fifth decade of life.

Symptoms

Symptoms arise from progressive degeneration and tearing of the anterosuperior labrum followed by chondral surface and eventually degenerative joint disease. There may be an associated femoroacetabular impingement (FAI) due to reduced femoral offset and abnormal femoral version (Table 2.2).

• • Fatigue weakness and trochanteric pain
• • Hip pain when sitting (common in FAI due to impingement)
• • Progression from intermittent pain to a constant dull ache
• • Clicking or locking during activity

When later degenerative changes occur, symptoms are more typical of hip osteoarthritis (OA), namely groin, buttock or thigh stiffness/pain related to activity levels. The differential diagnoses of extraarticular hip pathologies should be considered, particularly in the presence of normal imaging.

Clinical Examination

• • Inspection – Antalgic, stiff or Trendelenburg gait (due to reduced femoral offset and abductor failure)
• • Palpation – Femoral triangle pain
• • Movement – Limited range of motion, crepitis, excessive internal rotation (femoral anteversion), and pain on hip flexion and internal rotation, signifying femoro-acetabular impingement

Imaging

The aims of imaging in adult hip problems are to:

1. 1. Establish the presence of dysplasia (acetabulum and femur)
2. 2. Gauge severity of dysplasia
3. 3. Identify focal pathology (e.g., FAI, labral or chondral damage)
4. 4. Evaluate presence/absence of irreversible chondral degeneration
5. 5. Plan for surgery

Treatment

Nonoperative

There is limited scope for nonoperative management in dysplastic hips due to the pathoanatomy and abnormal mechanics. Weight modification and gait training may give some symptomatic relief.

Operative

Hip Arthroscopy – Hip arthroscopy can be used to treat a focal lesion such as a labral detachment or partial chondral damage. It is usually only be successful in those with a borderline centre-edge angle.

Periacetabular Osteotomy – A periacetabular osteotomy (PAO) aims to increase cover of the femoral head with articular cartilage, improving the contact area in the weight-bearing zone. A range of periacetabular osteotomies have been described; however, the Ganz PAO (while technically challenging) is the predominant procedure for...