9 – Joint arthroplasty + hip osteoarthritis + bone substitution

From greek.doctor

16. Hip osteoarthritis, clinical features, conservative management of

  • Osteoarthritis of the hip
  • Clinical features
    • Morning stiffness
    • Inguinal pain or pain above greater trochanter
      • Can refer to the thigh and knee
    • Contractures (reduced ROM)
      • First movement affected: internal rotation
    • Limp
    • Muscle atrophy around hip and thigh
    • Limb length difference
  • Diagnosis
    • By conventional x-ray
    • AP view and Lauenstein (frog-leg) view x-ray
      • Narrow joint line
      • Subchondral sclerosis
      • Subchondral cysts
      • Osteophytes
  • Treatment
    • Conservative
      • Frequent exercise
        • Especially joint-friendly exercises, like swimming, cycling
      • Weight loss
      • Physical therapy
      • NSAIDs
      • Orthopaedic shoes
      • Crutch on affected side
    • Surgical
      • Only if conservative treatment isn’t sufficient (late stage)
      • Total hip replacement
      • Hip arthroplasty is one of the most successful orthopaedic operations
        • > 90% satisfaction rate
        • 1,5 million procedures every year
      • Can be used in any joint destruction
        • Mostly in osteoarthritis or osteonecrosis of hip joint
        • But contraindicated in case of ongoing local or systemic infection
          • The prosthesis has no blood supply and antibiotics therefore can’t reach it -> provides good base for infection
      • (Partial hip replacement)
        • NOT used in orthopaedics -> only used in treatment of hip fractures
        • Femoral head is replaced with prosthesis
        • Acetabulum is preserved
      • Total hip replacement (THR)
        • Used in orthopaedics
        • Femoral head is replaced with prosthesis
        • Acetabulum is replaced with prosthesis
      • Postoperative DVT prophylaxis

35. Surgical options for degenerative joint diseases

See topics on hip osteoarthritis and knee osteoarthritis

58. Joint prothesis types and fixation methods

  • Joint prosthesis
    • They are used to replace damaged joints
  • Total hip replacement (THR)
    • Surgical technique
      • The acetabulum is opened and reamed (hollowed out)
        • This removes any residual cartilage and leaves only the bony surface
      • The neck of the femur is cut with a saw
      • The medullary cavity is reamed to make space for the femoral stem
      • If bone cement is used, bone cement is applied to the medullary cavity of the femur and the acetabulum to fix the femoral stem and the acetabular parts, respectively
      • If bone cement is not used the femoral stem and acetabular parts are banged in
    • Components
      • Acetabular component
        • Polyethylene insert or liner
          • A special kind of plastic
          • Provides the mobile part of the joint
        • Acetabular shell
          • Made of metal
      • Femoral head
      • Femoral stem – goes into medullary canal of femur
    • Types
      • Cemented THR
        • Both femoral component and acetabular component are fixed to the bone with bone cement
        • Bone cement dries after 15 minutes, meaning that the prosthesis can (in theory) be walked on and used immediately after the procedure
          • However, no patient can walk immediately after any major surgery
        • Bone cement is created by mixing a powder with a solution -> then applied with a cement gun
        • The bone cement will enter the lacunae of the bone, fixing the prosthesis to the bone
      • Uncemented THR
        • Does not use bone cement – instead, the prosthesis is fixed by force
          • This is called “press fit”
        • The acetabular part is banged into the acetabulum
        • The femoral stem is banged into the medullary cavity of the femur
        • The prosthesis has a porous coating and the bony part is rough, which creates a lot of friction between the prosthesis and the bone
          • This is called primary fixation
          • If the friction itself is not enough the prosthesis can be further fixed with screws
        • After some weeks the bone will grow into the porous surface of the prosthesis
          • This is called secondary or final fixation
          • This takes time, and the patient must not be weightbearing during this time
    • Indications
      • Cemented THR
        • For elderly
        • For less active patients
        • For those with poor bone quality
      • Uncemented THR
        • For young, active patients
        • For those with good bone quality

61. Bone substitution, bone transplantation

  • Bone grafting/substitution/transplantation = replacing bone with something (called a bone graft)
  • As the native bone grows it will generally replace the graft material with normal bone
  • Needed in
    • Alignment correction
      • A wedge of bone graft may be inserted into a gap made by an osteotomy to correct alignment
    • Tumour surgery
      • Significant amounts of bone are removed and should be replaced
      • Tumour in diaphysis -> part of the diaphysis is removed and must be replaced
    • Revision joint replacement (replacing the previously implanted prosthesis with a new one)
    • Bone cyst removal
    • Congenital bone defects
    • Post-traumatic bone defects
  • Properties of an ideal bone graft
    • Sterility
    • Good mechanical properties
      • Loadability
      • Fixation – must be fixable by plate or screw
    • Good healing properties
      • Osteoconduction – the grafts ability to connect the resected bone surfaces of host bone
      • Osteoinduction – the grafts ability to induce host osteogenesis
      • Osteogenesis – the grafts ability to produce bone by itself
        • Some grafts contain living osteoblasts, or a protein called BMP which stimulates host osteoblasts
    • Good availability
    • The choice of graft depends on the patient
    • A modern orthopaedic department should have all different types of bone graft available
    • There is no single “best” graft or material
  • Types of grafts according to material
    • Bone grafts
      • Solid (tubular) bone grafts
        • To replace bone after tumour removal, etc.
      • Morselized bone (= bone chips)
        • To replace bone inside a bone cyst
    • Artificial grafts
      • Metal grafts
      • Bone cement grafts
  • Types of grafts according to origin
    • Autologous (from the patient)
      • Best graft
      • Osteogenesis + osteoinduction + osteoconduction
      • Patient needs an extra surgery to acquire the bone graft
      • Limited amount
    • Allogenic
      • From a human donor
        • Cadaver
        • Brain dead
        • From another patient who had bone removed as part of joint replacement, etc.
      • Osteoinduction + osteoconduction
      • Contains BMP
      • May contain transmittable diseases (hepatitis, HIV)
      • Expensive
    • Xenogenic (from another species)
      • Only used after deprotonation, so only the inorganic bone remains
      • No BMP or transmittable diseases
      • No osteoinduction or osteogenesis, only osteoconduction
      • Grafts from sea corrals
        • Sea corrals are comprised of hydroxyapatite with similar properties as human bone