Hip Spacers: Weight-Bearing Restrictions, Purpose, and Rehabilitation

Can you weight bear on a hip spacer?

Generally, weight-bearing on a hip spacer is significantly restricted, often limited to toe-touch or partial weight-bearing, as these devices are temporary solutions not designed for full load-bearing capacity.

Understanding the Hip Spacer: Purpose and Design

A hip spacer is a crucial, albeit temporary, component in the management of periprosthetic joint infection (PJI) following total hip arthroplasty (THA). Unlike a definitive hip replacement prosthesis, a spacer serves a specific therapeutic role, primarily to combat infection and maintain joint space.

• What is a Hip Spacer? A hip spacer is a temporary implant, typically made of bone cement (polymethylmethacrylate, PMMA) that is custom-molded or pre-formed. It is often impregnated with high concentrations of antibiotics, which elute directly into the joint space to target the infection locally. It functions as a placeholder, preventing the surrounding tissues from collapsing into the void left by the removed infected prosthesis.
• Why is it Used? The primary indication for a hip spacer is in the two-stage revision arthroplasty protocol for PJI. In the first stage, the infected prosthetic components are removed, the joint is thoroughly debrided, and the antibiotic-laden spacer is implanted. This allows for a period of antibiotic treatment (typically 6-12 weeks) to eradicate the infection before the second stage, where the spacer is removed and a new, definitive hip prosthesis is implanted.
• Types of Spacers:
  • Static (Non-Articulating) Spacers: These are fixed in place and do not allow for significant hip movement. They are often used when bone stock is poor or stability is a major concern.
  • Articulating Spacers: These are designed to allow some degree of hip motion, mimicking the ball-and-socket function of a natural hip. They may consist of a femoral component and an acetabular component, allowing for controlled movement while the infection is being treated.

Weight-Bearing Protocols: The Crucial Considerations

The ability to weight bear on a hip spacer is highly individualized and dependent on several critical factors, but the overarching principle is one of restricted weight-bearing.

• General Principle: Restricted Weight-Bearing Due to their temporary nature, material properties (cement is not as robust as metal/ceramic implants), and the underlying compromised bone and tissue health from infection, hip spacers are not designed to withstand the full loads of normal gait. The goal during the spacer period is to maintain hip stability, allow the infection to clear, and prevent mechanical failure of the spacer or surrounding bone.
• Factors Influencing Weight-Bearing Status:
  • Type of Spacer:
    • Static Spacers: These typically necessitate non-weight bearing (NWB) or toe-touch weight bearing (TTWB) to protect the surgical site and prevent spacer dislodgement.
    • Articulating Spacers: While designed for some movement, they still generally require restricted weight-bearing, often partial weight-bearing (PWB) with strict limits (e.g., 20-50 lbs or 10-25% of body weight), or toe-touch weight bearing (TTWB). The allowance for some movement is to prevent muscle atrophy, maintain range of motion, and potentially improve joint fluid circulation, aiding antibiotic delivery, but not for full load.
  • Surgeon's Protocol and Patient-Specific Factors: The most critical determinant of weight-bearing status is the specific instruction from the orthopedic surgeon. This decision is based on:
    • The patient's bone quality and integrity.
    • The stability and fixation of the spacer.
    • The extent of the original infection and bone loss.
    • The patient's overall health, balance, and ability to comply with restrictions.
    • The surgeon's preferred technique and experience.
  • Bone Quality and Fixation: If the surrounding bone is osteoporotic or significantly damaged by infection, the risk of fracture or spacer subsidence (sinking) increases with weight-bearing.
  • Pain and Stability: Any increase in pain with attempted weight-bearing or signs of instability should immediately halt the activity and be reported to the medical team.
• Risks of Non-Adherence to Weight-Bearing Restrictions:
  • Spacer Dislocation or Fracture: The temporary cement construct is not as strong as a permanent implant.
  • Periprosthetic Fracture: Fracture of the bone around the spacer due to excessive stress.
  • Deep Venous Thrombosis (DVT) and Pulmonary Embolism (PE): While weight-bearing restrictions are in place, prolonged immobility can increase DVT risk, necessitating appropriate prophylaxis.
  • Delayed Infection Clearance: Mechanical stress on the joint can impede the healing process and potentially compromise the local antibiotic environment.
  • Increased Pain and Swelling: Overloading the joint can lead to inflammation and discomfort.
  • Compromised Outcome of the Second Stage: Damage during the spacer phase can complicate the subsequent definitive hip replacement surgery.

Rehabilitation During the Spacer Period

Despite weight-bearing restrictions, rehabilitation is vital during the spacer phase to maintain muscle strength, preserve range of motion, and prepare for the second stage of surgery.

• Focus Areas:
  • Non-Weight Bearing Exercises: Isometric exercises for hip and thigh muscles, ankle pumps, and gluteal sets.
  • Assisted Range of Motion (AROM) or Passive Range of Motion (PROM): Gentle, controlled movements within prescribed limits to prevent stiffness, especially with articulating spacers.
  • Core Stability and Upper Body Strength: Crucial for managing crutches or other assistive devices.
  • Gait Training: Learning to ambulate safely with assistive devices while adhering to weight-bearing restrictions.
• Assistive Devices: Patients will typically require crutches, a walker, or a rolling walker to ambulate safely and offload the affected hip.
• Activity Restrictions: High-impact activities, twisting motions, and extreme ranges of motion are strictly prohibited to protect the spacer.

The Path Forward: From Spacer to Definitive Arthroplasty

The spacer period is a critical interim phase. Once the infection markers normalize and the medical team confirms infection eradication, the patient will proceed to the second stage of surgery. The spacer is removed, and a new, sterile total hip replacement prosthesis is implanted. Post-operatively, rehabilitation for the new hip replacement will begin, often with a more progressive weight-bearing protocol as determined by the surgeon.

Crucial Takeaway: Always Consult Your Surgical Team

The information provided here is for educational purposes only. Any specific questions regarding weight-bearing status, activity restrictions, or rehabilitation during the hip spacer period must be directed to your orthopedic surgeon, physical therapist, or medical team. Adherence to their individualized instructions is paramount for successful infection eradication and optimal surgical outcomes.