Total Hip Replacement in Special Circumstances

Conversion of a Hip Arthrodesis to THR

Indications

  • Pain in other joints due to hip fusion, especially in the other hip and ipsilateral knee
  • Previously arthrodesed hip; patient now desires increased range of motion (ROM)

Pre-Op Workup

  • Investigate the reason for the original arthrodesis
  • Rule out ongoing infection if arthrodesis was due to or complicated by infection

Principles & Potential Problems

  1. Proximal femoral deformity
  2. Lack of reference for neck cut
  3. Lack of reference for cup position (TAL often still present)
  4. Bleeding
  5. Bone loss (uncommon)
  • Functioning abductors are essential for a good outcome
  • Assess abductors clinically, using MRI (fatty infiltration) or EMG
  • Use retained hardware or visible trochanter as reference for neck cut
  • Place retractor in obturator foramen to visualize cup placement
  • Intra-operative X-ray can help assess cup position before reaming
  • Generally, good bone stock for cup placement
  • If proximal femoral deformity or sclerosis is present, consider using burrs, drills, or osteotomy

Paget’s Disease

Causes of Hip Pain

  • Secondary arthritis
  • Deformity
  • Stress fracture
  • Sarcomatous change
  • Referred pain from the spine

Typical Deformities

  • Varus neck
  • Antero-lateral bowing of the femur
  • Protrusio

Possible Problems

  • Hypervascular tissues, especially in active disease, leading to significant blood loss
  • Risk of intra-pelvic perforation
  • Bone may be osteoporotic or sclerotic

Pre-Operative Considerations

  • Evaluate for significant proximal femoral deformity; obtain full femur X-rays
  • Plan for osteotomy if necessary
  • Use burrs and drills to open the canal
  • Pre-operative treatment with bisphosphonates and calcitonin to reduce disease activity
  • Prepare for protrusio
  • Avoid lengthening if the neck is in varus
  • Warn the anesthetist about the potential for high output failure in active disease

Gaucher’s Disease

  • Commonly presents with AVN; consider in any patient with AVN
  • Bone infiltrated with structurally weak Gaucher’s cells
  • High risk of intra-operative fractures and bleeding
  • Post-operative pain is common
  • Many patients have had a splenectomy, increasing infection risk

Sickle Cell Anemia

Potential Problems

  • AVN and its complications
  • Very sclerotic canal due to prior sickle cell crises and infarcts
  • Hypervascular tissues leading to bleeding
  • Increased infection risk, particularly in asplenic patients
  • Pain management challenges due to long-term opioid use

Hemophilia

Characteristics

  • Hemophilic arthropathy typically affects the knee and elbow; less common in the hip
  • Deformities resemble Perthes disease with a flattened head
  • Often associated with acetabular dysplasia

Main Concerns

  • Bleeding and infection
  • Requires close collaboration with a hematologist in an MDT center

Tumors

Indications for THR

  • Metastases
  • Low-grade malignancies, such as chondrosarcoma
  • Benign aggressive lesions, e.g., PVNS or GCT

Principles

  • Determine the nature of the lesion
  • Plan surgical margins
  • Select the appropriate prosthesis (standard, revision type, or endoprosthesis)
  • Preserve abductors if possible
  • MDT collaboration is essential for adjuvant or neo-adjuvant therapy

Neuromuscular Disorders

  • Examples include Parkinson’s disease
  • Instability caused by contractures (flexion, adduction deformities)
  • Treatment:
    • Release adductors, rectus femoris, and psoas
    • Use an anterolateral approach and over-antevert the cup
  • Patients are prone to skin breakdown and systemic infections post-operatively

Femoroacetabular Impingement (FAI)

Aetiology

  • Pain due to a labral tear, caused by acute or chronic trauma
  • Often associated with structural issues, commonly CAM lesions
  • May be secondary to conditions such as SUFE or Perthes
  • Evidence suggests FAI is a leading cause of early-onset OA

Pathophysiology

CAM Impingement

  • Mismatch in the radius of curvature between the femoral head and acetabulum
  • Labral tear leads to separation at the chondro-labral junction
  • Progresses to delamination and unstable chondral flaps

Pincer Impingement

  • Femoral neck impinges on the acetabulum during ROM
  • Associated with conditions like coxa profunda, protrusio, or acetabular retroversion
  • Leads to acetabular lesions with cystic degeneration

Clinical Features

  • Deep-seated groin pain exacerbated by hip flexion (e.g., sprinting, kicking, rising from chairs)
  • Pincer impingement often causes buttock pain during leg extension
  • Associated clicking is common with labral tears

Examination

  • Positive impingement sign
  • Reduced internal rotation

Imaging

X-Ray (AP and Cross-Table Lateral)

  • Evaluate acetabular abnormalities:
    • Centre Edge angle (<15 degrees diagnostic of dysplasia)
    • Protrusio
    • Retroversion
  • Evaluate femoral abnormalities:
    • Neck-shaft angle
    • Offset ratio (<0.15 diagnostic of CAM)
    • Alpha angle (>50 degrees diagnostic of CAM)

MRI Arthrogram

  • Gold standard for diagnosing labral and chondrolabral tears
  • Detects subtle CAM deformities

CT Scan

  • Useful for identifying dysplasia and subtle deformities

Management

Non-Operative

  • Worth attempting but unlikely to resolve symptoms
  • Aim to prevent arthritic changes

Arthroscopic Surgery

  • Recommended for isolated CAM deformity with labral tears
  • Most common treatment

Open Surgical Dislocation

  • Less common due to advancements in arthroscopic techniques

Osteotomy (Periacetabular or Proximal Femoral)

  • Used for cases of dysplasia where labral repair alone is insufficient

Arthroplasty

  • Suitable for patients with debilitating symptoms and OA
  • Options include THR or resurfacing
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