What are the treatment options for complications related to collared uncemented (non-cemented) stem implants?

Treatment Options for Complications Related to Collared Uncemented Stem Implants

Cemented femoral stems are strongly recommended over uncemented stems for hip arthroplasty due to lower complication rates, particularly in older adults. 1, 2

Common Complications of Uncemented Collared Stems

Uncemented collared stems can experience several complications that require specific management approaches:

1. Subsidence and Loosening

• Presentation: Pain, limb length discrepancy, radiographic evidence of stem migration
• Treatment options:
  • Minor subsidence (<3mm): Protected weight-bearing for 4-8 weeks 3
  • Significant subsidence: Revision to cemented stem if loosening continues 4
  • For stems without initial collar-calcar contact (higher risk): More intensive monitoring as these have 19% vs 1.3% subsidence rate compared to those with good contact 3

2. Periprosthetic Fractures

• Incidence: 2% in uncemented stems 5
• Treatment options:
  • Nondisplaced calcar cracks: Protected weight-bearing for 4-6 weeks 3
  • Displaced fractures: Open reduction internal fixation with cables/plates
  • Severe fractures with loose stem: Revision to longer stem (cemented preferred) 4

3. Aseptic Loosening

• Risk factors: High offset collarless designs (1.6 times higher risk), small stem sizes (sizes 8-11 have 1.4 times higher risk) 4
• Treatment options:
  • Revision to cemented stem (preferred) 1
  • Revision to larger diameter uncemented stem with collar if bone stock adequate 4

Evidence-Based Management Approach

Step 1: Diagnosis and Assessment

• Obtain standard radiographs to evaluate stem position, subsidence, and bone integrity
• Consider advanced imaging (CT, MRI) to assess bone loss and implant stability
• Evaluate for infection with inflammatory markers (ESR, CRP) and joint aspiration if indicated

Step 2: Determine Complication Type and Severity

1. Mild complications (minimal subsidence, stable implant):

   • Protected weight-bearing
   • Physical therapy focused on gait training with assistive devices
   • Follow-up radiographs at 4-8 weeks 3

2. Moderate complications (progressive subsidence, early loosening):

   • Activity modification
   • Consider revision if symptoms persist despite conservative measures
   • More frequent radiographic monitoring

3. Severe complications (fracture, significant loosening):

   • Surgical revision with cemented stem strongly recommended 1, 2
   • Consider interdisciplinary care program to improve outcomes 1

Revision Strategy

When revision is necessary, the following approach is recommended:

1. Implant selection:

   • Cemented femoral stems are strongly recommended for revision of failed uncemented stems, especially in patients >65 years 1, 6
   • Recent evidence shows cemented stems have lower risk of complications in older adults 1

2. Surgical technique:

   • Thorough canal preparation with pressurized lavage system 2
   • Retrograde cement application using a cement gun 2
   • Enhanced soft tissue repair to minimize dislocation risk 2

3. Postoperative care:

   • Physical therapy beginning on postoperative day 1 1
   • Implementation of an interdisciplinary care program 1
   • Follow-up at 2-4 weeks, then at 3 months, 6 months, and annually 2

Special Considerations

Age-Related Factors

• Patients >70 years have 1.6-1.9 times higher risk of stem revision with uncemented stems 4
• Recent evidence suggests collared metadiaphyseal-filling cementless stems may have advantages over cemented stems in patients ≥65 years, with lower risk of all-cause revision, aseptic loosening, dislocation, and infection 6

Stem Design Considerations

• Collared stems show lower complication rates than collarless designs 7
• Long stems demonstrate fewer complications than short stems in direct anterior approach THA 7
• Initial collar-calcar contact significantly reduces subsidence risk (1.3% vs 19.0%) 3

Preventive Measures for Future Implantations

To reduce complications with uncemented collared stems:

• Ensure proper sizing (avoid sizes 8-11 which have 1.4 times higher revision risk) 4
• Achieve direct collar-calcar contact during implantation 3
• Consider patient factors (age, bone quality, gender) in implant selection 4
• Use cemented stems in patients >70 years, especially women 4

While uncemented collared stems can be successful in well-selected patients, cemented fixation remains the most reliable option for most patients, particularly older adults, based on the strongest and most recent evidence 1, 2.