Review Question - QID 216688

ACL deficiency is a traditional/relative contraindication to mobile bearing UKA due to the risk of component spinout.

Unicompartmental knees rely on normal knee biomechanics to preserve motion and stability at the knee. The indications for unicondylar knee replacements are evolving. Using the original published criteria, indications for unicondylar replacement include: non-inflammatory arthritis, mechanical axis deviation <10 degrees from neutral in varus or 5 degrees in valgus, intact ACL, flexion contracture <15 degrees, no patellofemoral symptoms (although radiographic arthritis alone at the PF joint is not a contraindication), flexion to 90 degrees or greater, age >60, low activity demand, and weight <82 kilograms. While some authors argue that fixed bearing UKA may still be performed in patients with ACL deficiencies, mobile bearing UKA remains contraindicated given the risk of spinout.

In a study of 10 year follow up, Murray et al, defined the following indications for UKA: fixed flexion deformity <15 degrees, correctable varus deformity (indicating a competent medial collateral ligament), full-thickness cartilage in the lateral compartment, and non-inflammatory arthritis. Patellofemoral arthritis is not a contraindication, nor is moderate obesity.

The second Murray reference is a review of the indications and techniques for mobile bearing unicompartmental knee arthroplasty as mentioned above.

Engh et al review fixed bearing UKA in patients with ACL deficiency. They report revision rates between UKAs with and without intact ACLs were similar in the absence of clinical instability. Six-year UKA survivorship was 94% in ACL-deficient knees and 93% in ACL-intact knees. They conclude that ACL deficiency does not effect survivorship of in patients receiving fixed bearing UKA.

Incorrect Answers:
Answer 1: Medial patellofemoral disease is not an absolute contraindication for UKA.
Answer 2: Age is not a contraindication for UKA. Original patient description was that of an older low demand patient.
Answer 3: UKA can successfully be performed in patients with a flexion contraction <15 degrees.
Answer 5: Prior HTO does not affect clinical outcomes following UKA. This is not an absolute contraindication for mobile bearing UKA.