Developmental Dysplasia of the Hip (DDH): Understanding, Symptoms, Diagnosis, and Treatment

What is DDH in Ortho?

Developmental Dysplasia of the Hip (DDH) is an orthopedic condition characterized by an abnormality in the development of the hip joint, where the head of the femur (thigh bone) and the acetabulum (hip socket) are misaligned or improperly formed, leading to instability or dislocation.

Understanding Developmental Dysplasia of the Hip (DDH)

Developmental Dysplasia of the Hip (DDH), formerly known as Congenital Dislocation of the Hip (CDH), encompasses a spectrum of conditions affecting the hip joint in infants and children. It ranges from a mild instability or looseness of the joint to a complete dislocation where the femoral head is entirely out of the acetabulum. The critical aspect of DDH is that it's a developmental condition, meaning the hip joint, which is normal at birth, develops abnormally over time, or an already abnormal hip worsens. This improper development can lead to a shallow acetabulum, a stretched joint capsule, or a misaligned femoral head, compromising the integrity and function of the hip.

Anatomy of the Hip Joint

To understand DDH, it's essential to briefly review the normal anatomy of the hip. The hip is a ball-and-socket joint, designed for stability and a wide range of motion.

• Femoral Head: The "ball" is the rounded upper end of the femur.
• Acetabulum: The "socket" is a cup-shaped depression in the pelvis, formed by the fusion of three bones (ilium, ischium, and pubis).
• Articular Cartilage: Both the femoral head and acetabulum are covered with smooth articular cartilage, allowing for frictionless movement.
• Joint Capsule and Ligaments: A strong fibrous capsule encloses the joint, reinforced by powerful ligaments that provide stability and limit excessive motion.

In a healthy hip, the femoral head fits snugly and deeply into the acetabulum, maintaining proper alignment during movement and weight-bearing.

Causes and Risk Factors

While the exact cause of DDH is often multifactorial, several contributing factors and risk indicators have been identified:

• Genetic Predisposition: A family history of DDH significantly increases the risk.
• Female Gender: Girls are approximately four to five times more likely to develop DDH than boys.
• Firstborn Status: First-born children may be at higher risk due to a tighter uterus in the first pregnancy.
• Breech Presentation: Infants born in a breech position (feet or buttocks first) have a significantly higher risk due to increased pressure on the hips in utero.
• Oligohydramnios: Low amniotic fluid levels during pregnancy can restrict fetal movement and put pressure on the hips.
• Postnatal Swaddling Practices: Improper swaddling that restricts hip movement, particularly keeping the legs extended and together, can contribute to DDH development. "Hip-healthy" swaddling allows the baby's legs to bend up and out at the hips.
• Other Conditions: Associated with other musculoskeletal conditions like metatarsus adductus or torticollis.

Signs and Symptoms

The signs and symptoms of DDH vary depending on the child's age and the severity of the condition.

• In Infants (Newborn to 6 months):
  • Asymmetry: Uneven skin folds on the thighs or buttocks, or one leg appearing shorter than the other.
  • Limited Abduction: Reduced ability to spread the affected hip outwards (away from the body).
  • Clicking or Clunking Sensation: During specific maneuvers (Ortolani and Barlow tests) performed by a healthcare professional, a palpable click or clunk may indicate instability or relocation of the hip. Note: Not all clicks are indicative of DDH.
  • Difference in Movement: Less spontaneous movement of one leg.
• In Older Children (Walking Age):
  • Limp: A noticeable limp or waddling gait.
  • Trendelenburg Gait: Pelvic drop on the unsupported side during walking.
  • Leg Length Discrepancy: One leg appearing shorter.
  • Reduced Hip Mobility: Difficulty with certain movements like squatting or sitting cross-legged.
• In Adolescents and Adults (Undiagnosed or Late Presentation):
  • Chronic Hip Pain: Often in the groin, radiating to the thigh or knee.
  • Early Onset Osteoarthritis: Due to abnormal joint mechanics and increased stress on the articular cartilage.
  • Gait Abnormalities: Persistent limp or compensatory walking patterns.
  • Reduced Range of Motion: Stiffness and difficulty with daily activities.

Diagnosis of DDH

Early diagnosis is crucial for successful treatment and preventing long-term complications.

• Clinical Examination:
  • Newborn Screening: All newborns undergo a physical examination, including specific hip maneuvers (Ortolani and Barlow tests) to check for hip instability.
  • Ongoing Monitoring: Pediatricians continue to monitor hip development during routine check-ups.
• Imaging Studies:
  • Ultrasound: The preferred imaging method for infants up to approximately 4-6 months of age, as their bones are not yet fully ossified. It provides excellent visualization of cartilage and soft tissues.
  • X-ray: Used for infants older than 4-6 months, once the femoral head and acetabulum have ossified sufficiently to be visible on X-ray. It assesses the bony alignment and development.
  • MRI (Magnetic Resonance Imaging): May be used in more complex cases or for surgical planning to provide detailed soft tissue and bone imaging.

Treatment Approaches

Treatment for DDH aims to achieve and maintain a concentric reduction of the femoral head within the acetabulum, allowing for normal hip development. The approach depends on the child's age and the severity of the dysplasia.

• Non-Surgical (Conservative) Treatment:
  • Pavlik Harness: The most common and effective treatment for infants under 6 months. This soft, dynamic brace holds the hips in a flexed and abducted (frog-leg) position, encouraging the femoral head to seat properly within the socket and stimulating acetabular development.
  • Abduction Bracing/Casting: For slightly older infants (6-18 months) or those who failed Pavlik harness treatment, a rigid abduction brace or spica cast may be used after a gentle closed reduction.
• Surgical Treatment:
  • Closed Reduction: For infants or young children where conservative methods failed, the hip can be manually reduced into the socket without an incision, often under anesthesia, followed by a spica cast.
  • Open Reduction: If closed reduction is unsuccessful or for older children with persistent dislocation, an incision is made to directly visualize and reposition the femoral head into the acetabulum.
  • Osteotomy: For older children or adolescents, surgical procedures like a pelvic osteotomy (reshaping the acetabulum) or femoral osteotomy (reshaping the femur) may be performed to improve the congruity and stability of the hip joint.
  • Total Hip Arthroplasty (THA): In adults with late-diagnosed DDH leading to severe osteoarthritis, hip replacement surgery may be necessary to alleviate pain and restore function.

Long-Term Implications and Prognosis

The prognosis for DDH is generally excellent with early diagnosis and appropriate treatment.

• Early Intervention: When DDH is identified and treated effectively in infancy, the hip joint often develops normally, and the child can lead a full, active life without long-term complications.
• Late Diagnosis: If DDH goes undiagnosed or untreated until childhood or adolescence, the long-term outlook is less favorable. The abnormal mechanics put undue stress on the joint, leading to:
  • Persistent pain and limping.
  • Gait abnormalities.
  • Early onset degenerative joint disease (osteoarthritis), often requiring surgical interventions like osteotomies or, eventually, total hip replacement in adulthood.
• Importance of Follow-up: Regular follow-up appointments with an orthopedic specialist are crucial, even after successful treatment, to monitor hip development and address any potential late-onset issues.

DDH and Physical Activity/Exercise

For fitness enthusiasts, personal trainers, and student kinesiologists, understanding DDH is important, especially when working with individuals who have a history of the condition.

• Post-Treatment Rehabilitation: After conservative or surgical treatment, a structured rehabilitation program is often necessary. This typically involves:
  • Range of Motion Exercises: To restore flexibility and mobility.
  • Strengthening Exercises: Targeting hip abductors, adductors, extensors, and core muscles to improve stability and support the joint.
  • Gait Training: To correct compensatory patterns and improve walking efficiency.
• Exercise Considerations for Individuals with a History of DDH:
  • Joint Protection: Even if successfully treated, individuals with a history of DDH may have a slightly altered hip joint morphology or biomechanics. High-impact activities (e.g., long-distance running, jumping sports) might need to be moderated or avoided if they cause pain or discomfort.
  • Low-Impact Alternatives: Encouraging activities like swimming, cycling, elliptical training, and strength training can provide cardiovascular and muscular benefits with less stress on the hip joint.
  • Proprioception and Balance: Exercises that enhance proprioception and balance can further improve hip stability.
  • Pain Monitoring: Emphasize listening to the body and stopping or modifying exercises if pain occurs. Persistent pain should prompt a consultation with a healthcare professional.
• Role of Exercise Professionals: Personal trainers and kinesiologists should:
  • Obtain a Thorough Health History: Always ask about previous injuries or medical conditions like DDH.
  • Collaborate with Healthcare Providers: If a client has a history of DDH, especially if they experience symptoms, recommend consulting their orthopedic surgeon or physical therapist for specific exercise guidelines.
  • Individualized Programming: Design exercise programs that respect the individual's unique hip mechanics and any residual limitations. Focus on functional strength, mobility, and stability, rather than solely on performance metrics that might exacerbate joint stress.