- may result from unequal flexion and extension gaps; (instability in extension or flexion due to MCL or LCL incompetence);
- varus subluxation in extension or flexion due to unequal gaps;
- in the report by Fehring TK, et al, the authors evaluated the causes of revision surgery;
- between 1986 and 1999, 440 patients with TKR were referred for revision surgery;
- of the 440 patients who had revision surgery, 279 (63%) had revision surgery within 5 years of their index arthroplasty:
- 105 of the 279 patients with early failures (38%) had revision surgery because of infection;
- 74 (27%) had revision surgery because of instability;
- flexion instability / posterior subluxation:
- excessive posterior tibial slope:
- loose posterior stabilized TKR;
- previous patellectomy
- loose PCL (PCL retaining TKR);
- excessive extension position of femoral component:
- femoral component undersized (AP cutting guided positioned using anterior referenceing and downsized)
- references:
- Early Failures in Total Knee Arthroplasty.
- Flexion instability without dislocation after posterior stabilized total knees.
- Flexion instability after primary posterior cruciate retaining total knee arthroplasty.
- Early, incapacitating instability of posterior cruciate ligament-retaining total knee arthroplasty.
- Stepwise surgical correction of instability in flexion after total knee replacement
- Isolated Polyethylene Exchange:
- references:
- Polyethylene exchange only for prosthetic knee instability.
- Clinical Results of Modular Polyethylene Insert Exchange with Retention of Total Knee Arthroplasty Components.
- The Effectiveness of Isolated Tibial Insert Exchange in Revision Total Knee Arthroplasty.
- Isolated liner exchange: not always a useful option in revision TKA. Counterpoint.
- Isolated tibial insert/liner change: it can work. Point.
- references:
- Early Failures in Total Knee Arthroplasty.
- Knee instability after total knee arthroplasty.
- Insall Award paper. Why are total knee arthroplasties failing today?
- Flexion and extension gap balancing in revision total knee arthroplasty.
- Flexion instability in primary total knee replacement.
- Treatment Options for the Unstable Total Knee Arthroplasty - Condylar Constrained
- Study shows stable knees post-TKA led to significant improvement in functional outcomes