Instability following TKR:

- Discussion:
    - 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



Original Text by Clifford R. Wheeless, III, MD.

Last updated by Data Trace Staff on Sunday, January 4, 2015 12:13 pm