2007 OITE Question 20

Question

Which of the following findings is considered a contraindication to a mobile-bearing unicompartmental knee arthroplasty?

1- A range of flexion of 110°

2- A flexion deformity of 10°

3- A correctable varus deformity of 5°

4- Absence of the anterior cruciate ligament

5- Osteophytes in the patellofemoral compartment

Figures

Answer (click for answer)

Preferred response: 4 – Absence of the anterior cruciate ligament

The early medial unicompartmental replacements were performed without regard to the state of the ACL. UKA in knees with absent or damaged ACL showed 10 times higher rate of failure, usually from loosening of the tibial component (Goodfellow et al, 1988 JBJS Br). By the mid-1980s, an absent ACL was considered a contraindication for UKA.

Murray et al defined a ‘normal’ ligament as one which retained its synovial covering and had no longitudinal splits. The preserved surfaces in the posterior part of the joint, plus an intact ACL, are protective from the development of a fixed varus deformity and from involvement of the lateral compartment. The possibility of full correction of a varus deformity to neutral had been shown by routine preoperative AP x-rays taken in valgus stress.

Of note, the state of the patellofemoral joint, excessive weight, or chondrocalcinosis were not selection factors in the studies. Moreover, fibrillation of the surface of the cartilage in the lateral compartment seen at operation was not a contraindication and even frank erosions, if they were limited to the medial margin of the lateral femoral condyle, were accepted. Osteophytes around the margins of the lateral condyle were often seen and were not a contraindication.

Reference: Murray DW, Goodfellow JW, O’Connor JJ. The Oxford medial unicompartmental arthroplasty: a ten-year survival study. J Bone Joint Surg Br. 1998 Nov;80(6):983-9.


Murray DW. Mobile bearing unicompartmental knee replacement. Orthopedics. 2007 Sep;30(9):768-9.