When is a constraint liner recommended in total hip arthroplasty (THA)?

Indications for Constrained Liners in Total Hip Arthroplasty

Constrained acetabular liners should be used as a salvage procedure primarily in patients with recurrent hip instability or those at high risk for dislocation when all other factors related to total hip arthroplasty have been optimized, especially component positioning. 1

Primary Indications

Recurrent Instability

• Constrained liners were developed specifically to address the problem of recurrent instability in total hip arthroplasty patients 1
• They are most frequently used in revision cases with recurrent dislocation, accounting for approximately 77% of constrained liner usage in revision settings 2

Severe Ligamentous Instability

• Patients with severe ligamentous instability are candidates for constrained liners without delay for optimization of non-life-threatening conditions 3
• Delaying THA in these patients may lead to increased instability and juxtaarticular bone loss or deformity, which increases technical difficulty and risk of failure 3

Neuropathic Joints

• Patients with neuropathic joints often require more constrained implants as their procedures are technically challenging 3
• These cases should proceed to THA without delay as delaying surgery increases technical difficulty and does not improve outcomes 3
• Neuropathic joints typically show severe joint destruction even in early disease stages, with worsening bone loss and pain as the condition progresses 3

Risk Factors and Considerations

Failure Rates

• Modern constrained liners have a mechanical failure rate of approximately 5.7-11.4% 1, 4
• In revision settings, re-revision rates of approximately 10% at 5-year follow-up and 12% at 9-year follow-up have been reported 2
• The most common reason for failure is recurrent dislocation (70% of re-revisions) 2

Bone Loss Considerations

• There appears to be a trend toward higher revision rates with increasing acetabular and femoral bone loss, though this hasn't reached statistical significance in studies 5
• Component positioning is critical - implantation should only be considered when all other factors related to the THA have been optimized 1

Specific Patient Populations

• Multiple previous revisions: Patients who have undergone multiple revision procedures (three or more) are at particularly high risk for recurrent dislocation 5
• Failed dual mobility cups: Constrained liners may be considered when dual mobility cups have failed 5

Clinical Approach Algorithm

1. Exhaust conservative options first:

   • Optimize component positioning when possible 1
   • Consider less constrained options like dual mobility cups before proceeding to constrained liners 5

2. Reserve for specific high-risk scenarios:

   • Recurrent dislocations despite appropriate interventions 2
   • Severe ligamentous instability 3
   • Neuropathic joints with significant destruction 3
   • Multiple previous revisions (≥3 procedures) 5

3. Consider bone quality:

   • Evaluate acetabular and femoral bone loss according to classification systems 5
   • Be cautious with severe bone defects as they may impact revision rates 5

Important Caveats

• Constrained liners should be considered a salvage device rather than a primary option for instability 1
• The rigid design of constrained liners carries a risk of structural failure of acetabular reconstruction implants 5
• Closed reduction of dislocated constrained liners has been reported but with limited evidence regarding success rates 6
• In the Netherlands, there is relatively low usage of constrained liners in both primary and revision THA, suggesting they should be reserved for specific cases with high dislocation risk 2