Hip Spacers: Purpose, Mobility Restrictions, and Rehabilitation

Can you walk with hip spacers?

While it is generally possible to bear some weight and ambulate with hip spacers, this is typically highly restricted and carefully controlled, as their primary purpose is infection management, not functional mobility.

What Are Hip Spacers and Why Are They Used?

Hip spacers are temporary, antibiotic-loaded implants used in the treatment of periprosthetic joint infection (PJI) following total hip arthroplasty (THA) or in cases of severe septic arthritis. They are typically made from bone cement (polymethyl methacrylate, PMMA) mixed with high doses of antibiotics.

The primary purposes of a hip spacer are:

• To deliver a high local concentration of antibiotics directly to the infected joint space, helping to eradicate the bacterial infection.
• To maintain the joint space between the femur and the pelvis, preventing soft tissue contractures and bone loss that could complicate a subsequent definitive hip replacement surgery.
• To provide some degree of stability and allow for limited, controlled movement while the infection is being treated.

Hip spacer insertion is often the first stage in a two-stage revision arthroplasty, where the infected prosthetic components are removed, the spacer is implanted, and then, once the infection is cleared, a new, permanent hip prosthesis is implanted in a second surgery.

The Immediate Post-Operative Period: Mobility Restrictions

Following the insertion of a hip spacer, mobility is significantly restricted. The immediate post-operative period is crucial for infection control and allowing the tissues to heal.

Key considerations regarding mobility:

• Weight-bearing status: Most surgeons will prescribe a non-weight-bearing (NWB) or touchdown weight-bearing (TDWB) protocol on the affected limb. This means the patient is instructed not to put any significant weight through the leg, or only to touch the foot to the ground for balance without bearing weight.
• Reason for restriction: The spacer is a temporary device, not designed for the full biomechanical loads of normal walking. It lacks the robust fixation of a permanent implant. Excessive weight-bearing can lead to:
  • Spacer displacement or fracture: The spacer can shift out of position or break, necessitating further surgery.
  • Increased pain: Putting weight on an unstable or healing joint can cause significant discomfort.
  • Impaired infection resolution: Stress on the joint may hinder the effectiveness of antibiotic delivery and tissue healing.
  • Damage to surrounding soft tissues: Uncontrolled movement can strain muscles, ligaments, and capsule.
• Mobility aids: Patients will typically require the use of crutches, a walker, or a wheelchair for all ambulation during this phase.

The Purpose of Limited Ambulation (If Permitted)

While full functional walking is not the goal, limited, controlled movement may be encouraged under strict medical guidance. This movement is not for full weight-bearing ambulation but rather for:

• Maintaining joint range of motion (ROM): Gentle, passive, or assisted ROM exercises help prevent joint stiffness and contractures, which can make the subsequent definitive surgery more challenging.
• Facilitating antibiotic delivery: Some movement can aid in the circulation of antibiotic-rich synovial fluid within the joint space.
• Improving patient comfort and activities of daily living (ADLs): Limited movement can help patients manage basic self-care tasks within the confines of their restrictions.
• Preventing deconditioning: Controlled exercise can help minimize muscle atrophy and maintain overall fitness while avoiding undue stress on the hip.

Any ambulation with a hip spacer must be strictly within the limits set by the orthopedic surgeon and guided by a physical therapist.

Potential Risks and Complications of Excessive Weight-Bearing

Ignoring medical advice regarding weight-bearing restrictions can lead to serious complications, including:

• Spacer instability or dislocation: The spacer can move out of its intended position, requiring urgent surgical intervention.
• Spacer fracture: The temporary cement spacer can break under excessive load.
• Persistent or worsening infection: Overloading the joint can compromise the local environment, making it harder for antibiotics to clear the infection.
• Increased pain and inflammation: Mechanical stress on an already compromised joint can exacerbate symptoms.
• Delayed definitive surgery: Complications can postpone the second stage of the revision, prolonging the treatment period.
• Damage to bone and soft tissues: Excessive force can further injure the surrounding structures, complicating future surgery.

Rehabilitation and Transition to Definitive Arthroplasty

The rehabilitation process with a hip spacer is primarily focused on infection eradication and maintaining passive joint integrity.

• During the spacer phase: Physical therapy will emphasize gentle range of motion exercises, isometric strengthening (without joint movement), and instruction on safe transfers and protected ambulation using assistive devices. The focus is not on rebuilding strength for walking, but on preventing complications and preparing for the next stage.
• After infection resolution: Once the infection markers normalize (typically after several weeks or months), the spacer is removed, and the definitive total hip arthroplasty is performed.
• Post-definitive surgery: Following the permanent hip replacement, a more traditional rehabilitation program begins, progressively increasing weight-bearing, strength, and functional mobility, with the goal of restoring normal walking and activity levels.

Key Takeaways for Patients and Professionals

• Hip spacers are temporary medical devices primarily for infection management, not for long-term functional ambulation.
• Mobility is severely restricted with a hip spacer, typically involving non-weight-bearing or touch-down weight-bearing protocols.
• Strict adherence to the orthopedic surgeon's instructions regarding weight-bearing and activity levels is paramount to prevent complications and ensure successful infection eradication.
• Rehabilitation during the spacer phase focuses on maintaining joint integrity and preventing deconditioning within strict safety limits, preparing for the eventual definitive hip replacement.
• Full functional walking is the goal after the permanent hip replacement, not during the spacer phase.