Hip Dysplasia

Hip dysplasia is the most common developmental hip deformity causing osteoarthritis in adults. It describes a condition in which the acetabulum (socket) is too shallow to fully cover the femoral head (ball), resulting in abnormal loading of the joint that, over time, causes damage to the labrum and cartilage. Mr Balakumar treats hip dysplasia across all age groups, from infants through to adults, and is one of the few surgeons in Australia with the paediatric and adult training to manage the condition across an entire lifetime.

Understanding the hip joint

The hip is a ball-and-socket joint. The femoral head rotates inside the acetabulum. Both surfaces are lined with articular cartilage and lubricated by synovial fluid, which reduces friction inside the normal hip to less than one tenth that of an ice cube sliding on ice. The labrum, a rim of fibrocartilage lining the outer edge of the acetabulum, deepens the socket and helps stabilise the joint.

When the socket is too shallow, the femoral head bears abnormal pressure on the rim of the acetabulum rather than distributing load evenly across the joint surface. Over years, this rim overload causes labral tears and progressive cartilage loss, leading to osteoarthritis.

How common is hip dysplasia?

At least 80 per cent of hip osteoarthritis is caused by a developmental abnormality, and hip dysplasia is the most common of these. In its mildest form, the hip may look near-normal on X-ray and cause no symptoms until the patient is in their 30s or 40s. In its most severe form, the femoral head lies completely outside the socket — a condition called hip dislocation.

Causes and risk factors

Hip dysplasia has both genetic and environmental contributors. No single cause has been identified, though certain risk factors are well established: female sex, firstborn child, large birth weight, breech position in the womb, and family history of hip dysplasia. These factors are associated with laxity of the hip ligaments, which allows the femoral head to sit in an abnormal position during early development.

In some countries all newborns are screened for hip dysplasia at six weeks. This is because unless the hip is dislocated, dysplasia can be completely asymptomatic in its early stages. In Australia, babies are screened based on risk factors and clinical examination findings.

Symptoms

In infants, dysplasia is often detected through newborn screening or early developmental checks. In adolescents and adults, symptoms typically include groin or hip pain with prolonged activity, deep hip flexion or extended sitting. A sense of instability or clicking in the hip may also be present. Symptoms often develop or worsen during periods of increased physical demand, such as adolescence or early adulthood.

Diagnosis

Mr Balakumar assesses hip dysplasia through clinical examination and a specific set of standardised X-ray views, including a standing AP pelvis, a faux profile and a Von Rosen view. In selected patients, MRI with dGEMRIC cartilage mapping is used to assess joint cartilage health and guide decisions between joint preservation and joint replacement. Mr Balakumar uses this technology in collaboration with radiologists at the Royal Children’s Hospital Melbourne and Melbourne Radiology Clinic.

Treatment in infants and young children

When diagnosed in the first six months of life, hip dysplasia can be treated very effectively with brace treatment. A Pavlik harness or Dennis Brown abduction bar is worn to hold the hip in a position that encourages the socket to develop normally. The brace is worn for 23 to 24 hours per day depending on severity. Early diagnosis is integral — the earlier treatment begins, the better the outcome.

All treatment of dysplasia relies on four main principles: obtaining reduction of the hip, maintaining that reduction, encouraging growth of the socket to give a mechanically normal hip, and serial review until skeletal maturity to consider joint preservation options if needed.

When brace treatment fails, surgery is required. Options include medial open reduction to remove the soft tissue blocking the joint and reposition the femoral head, combined where necessary with a pelvic osteotomy such as a Dega, Salter or Bernese triple osteotomy to improve socket coverage.

Treatment in adolescents and adults

In adolescents and adults with preserved joint cartilage, periacetabular osteotomy (PAO) is the primary surgical treatment. The PAO repositions the entire socket to provide better coverage of the femoral head, correcting the underlying mechanical problem and reducing abnormal rim loading. It is a joint preservation procedure — the goal is to protect the patient’s own hip and delay or avoid the need for replacement.

In patients with advanced cartilage loss, joint preservation is no longer viable and hip replacement is the more appropriate option. The timing of this transition is informed by clinical assessment, X-rays and, in borderline cases, dGEMRIC cartilage mapping.

The condition must be pre-arthritic for preservation to be appropriate. If the mechanical environment has been severe for long enough, the cartilage is usually damaged beyond the point of preservation. In these cases, hip replacement becomes the appropriate path forward.

When should I consider surgery?

The timing of surgery in hip dysplasia is important because cartilage damage, once established, heals poorly. Intervening early, before irreversible damage has occurred, gives the best long-term outcomes. The decision is made jointly between the patient and Mr Balakumar, based on age, symptoms, imaging findings and the degree of cartilage damage present.