Dr. Kevin Yip

Dr Kevin Yip
Orthopaedic Surgeon
MBBS(UK), FRCS(EDIN), FAM(SING), FHKCOS(ORTHO)

Featured on Channel NewsAsia

Hip Replacement

Basics
Description
  • Many forms of arthritis lead to destruction of the articular cartilage of the hip joint, resulting in pain and loss of function.
  • End-stage arthritis can be treated with surgical replacement of the joint.
  • Elderly patients may have a greater risk of cardiac complications and more associated medical problems than younger patients.
  • Patients <50 years old:
    • Are likely to need revision surgery because their life expectancy may exceed the longevity of the prosthesis
    • Other treatment options, such as medical management, hip fusion, and femoral osteotomy, should be strongly considered in the younger, high-demand patient.
  • Hip replacements may be anchored to the bone with bone cement or with uncemented techniques that allow the bone to grow into the implant.
General Prevention
Weight loss and limitation of activity may postpone the need for hip replacement.
 
Epidemiology
Most hip replacements are performed in patients >65 years old, but the procedure is being performed more commonly in younger patients than in the past.
 
Incidence
  • >200,000 total hip replacements are performed in the United States each year.
  • The number of hip replacements continues to increase.
Risk Factors
  • Primary osteoarthritis may be more common in high-demand athletes and obese patients.
  • Osteonecrosis has been linked to prolonged steroid use, alcoholism, radiation, and trauma.
  • Osteoporosis often leads to femoral neck fractures in elderly patients.
Genetics
  • Possible familial predisposition to primary osteoarthritis
  • No Mendelian pattern of inheritance
Pathophysiology
Pathological Findings
The common denominators in all forms of arthritis are breakdown of the articular cartilage, loss of the proteoglycan, and gradual cartilage dissolution.
 
Etiology
  • Primary osteoarthritis is the most common cause of disabling hip arthritis.
  • Traumatic arthritis, osteonecrosis, rheumatoid arthritis, sickle cell anemia, recurrent hemarthrosis, Paget disease, and AS all may lead to degenerative destruction of the hip joint.
  • Developmental conditions such as SCFE, DDH, and Legg-Calve-Perthes disease all may lead to degenerative joint disease later in life.
  • Some acute hip fractures also may be treated with partial or total hip replacement.
Associated Conditions
Degenerative joint disease of the contralateral hip, either knee, the lumbar spine, and the upper extremities often is seen in patients requiring hip replacement.
 
Diagnosis
  • Primary osteoarthritis of the hip may result in pain in the groin, the lateral thigh, or radiating to the knee.
  • Pain is more common with activity but may eventually become present at rest and at night.
  • In advanced stages, pain may limit the patient to needing rest after walking <1 block.
  • Limitation of ROM, especially of flexion, extension, and internal rotation, may be present.
  • With ambulation, abductor lurch may be evident.
Signs and Symptoms
  • Incapacitating arthritis of the hip commensurate with physical and radiographic findings
  • Failure to walk more than a few blocks without stopping
  • Pain unrelieved by standard arthritis medication
  • Pain after activity
  • Difficulty with activities of daily living, including dressing, grooming, and climbing stairs
Physical Exam
  • Perform a neurovascular examination of the affected extremity.
  • Record the ROM of the hip.
  • Pay special attention to contractures, leg-length discrepancy, and gluteal muscle strength.
  • Assess the patient’s gait.
  • Pain at extremes of motion
  • Positive Trendelenburg test
  • Groin or anterior thigh pain with active straight-leg raises
Tests
Lab
  • For total hip replacement, order the following before surgery:
    • Complete blood count
    • Blood chemistry studies
    • Coagulation times
  • Electrocardiogram, chest radiographs, and urinalysis should be obtained when appropriate.
  • Many patients are able to donate autologous units of blood 4-6 weeks before surgery.
Imaging
  • Radiography:
    • AP pelvis and frog-leg lateral hip radiographs usually are adequate for assessing the hip joint.
    • Long, standing films of the lower extremities and pelvis may be helpful.
Differential Diagnosis
  • Hip pain may be caused by spinal stenosis or a herniated lumbar disc.
  • Low back pain of any cause may radiate to the lateral thigh and hip.
  • Trochanteric bursitis may result in lateral hip pain.
  • Stress fracture
  • Occult neoplasms, such as metastatic bone disease, multiple myeloma, and primary mesenchymal tumors, also can cause hip pain.
Treatment
Special Therapy
Physical Therapy
  • Postoperative patients are instructed in strengthening exercises, especially hip flexion, extension, and abduction.
  • Transfer and gait training with a standup walker are emphasized.
Medication
First Line
  • Analgesics in the acute postoperative period
  • Postoperative patients require prolonged treatment for prophylaxis of DVT with warfarin (Coumadin) or low-molecular-weight heparin.
Surgery
  • Total hip replacement consists of a metal femoral component and a head that replaces the proximal femur.
    • The acetabulum most commonly is replaced with a metal shell that has a high-density polyethylene plastic insert.
    • The components may be fixed to the bone with or without cement.
      • Uncemented components have a rough surface to allow for bony ingrowth.
  • Surgical approaches:
    • Anterior (Smith-Peterson)
      • Superficial interval: Sartorius and tensor fascia lata
      • Deep interval: Rectus femoris and gluteus medius
      • Lateral femoral cutaneous nerve is in danger because it penetrates the sartorial fascia.
    • Anterolateral (Watson-Jones approach):
      • Interval between the gluteus medius muscle and the tensor fascia lata
    • Lateral (Hardinge):
      • The anterior 1/3 of the gluteus medius and minimus are reflected off the greater trochanter.
      • The superior gluteal nerve and artery can be injured with anterior reflection of the gluteus medius.
      • Slower abductor rehabilitation
    • Posterior (Langenbeck/Moore):
      • Splitting of the gluteus maximus with release of short external rotators
      • The sciatic nerve should be identified and protected.
      • Higher dislocation rate than with other approaches, especially without capsular repair
  • Bearing surfaces: The acetabular liner and the femoral head ball can be made of different materials to prevent wear.
    • Metal on polyethylene:
      • Standard option
      • Newer highly cross-linked polyethylenes are thought to decrease wear rates.
      • Polyethylene wear debris leads to osteolysis and component loosening.
    • Metal on metal:
      • Very low wear rates
      • Metal ion debris can accumulate in the bloodstream and organs.
      • Very large head size may decrease dislocation rates and increase ROM.
    • Ceramic on ceramic:
      • Very low wear rates
      • Very low rate of ceramic fracture
      • No liner options
  • Minimally invasive surgery:
    • Some approaches may limit muscle damage.
    • Multimodal approaches to anesthesia and therapy have hastened recovery.
    • Some evidence suggests that smaller incisions are not responsible for faster recovery.
Follow-up
Prognosis
  • Hip arthroplasty has excellent long-term results, with many patients ambulating without external support and resuming previously impossible activities.
  • A long-term study has shown that 85% of cemented prostheses survive for 20 years.
  • Uncemented components also have an excellent long-term performance.
Complications
  • Postoperative medical complications:
    • Myocardial infarction
    • Pneumonia
    • Urinary retention
    • Ileus
    • Death
  • Leg-length discrepancy
  • DVT and PE
  • Infection
  • Revision surgery
  • Polyethylene wear
  • Osteolysis
  • Dislocation
  • Periprosthetic fracture
  • Heterotopic ossification
  • Loosening
  • Nerve palsy
Patient Monitoring
  • The importance of long-term radiographic monitoring must be stressed.
    • Radiographs should be taken at 1-2-year intervals to look for polyethylene wear and osteolysis.
  • After hip replacement, patients should receive antibiotic prophylaxis before dental work.
Miscellaneous
Codes
ICD9-CM
715.95 Hip osteoarthritis
 
Patient Teaching
  • Patients must understand that hip arthroplasty is a major surgical procedure that requires months of substantial activity limitation and may require a full year to achieve full benefit.
  • They must be prepared to adhere to the hip precautions taught in physical therapy and to contribute to the rehabilitation process.
Activity
  • Weightbearing after surgery depends on surgeon technique and preference, but as-tolerated is common.
  • Patients may be given motion restrictions to prevent dislocation; most commonly, avoidance of hip flexion >90° and crossing the legs.
FAQ
Q: When should I have a hip replacement?
A: Hip replacement has an excellent chance of reducing pain and improving function. However, it is major surgery with serious potential complications, including death. A patient should have severe pain and disability before considering surgery.

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