Introduction

Unicompartmental knee arthroplasty (UKA) is currently considered favorable over total knee arthroplasty (TKA) due to quicker recovery and high postoperative function; however, UKA failure rates remain high and there is a lack of universal guidelines for operative planning. The purpose of this study was to investigate the role of preoperative MRI in surgical decision making for medial (UKA) vs. total knee arthroplasty (TKA).

Methods

A total of 94 knees of 85 consecutive patients who underwent knee replacement surgery were analyzed retrospectively. Patients who were deemed candidates for UKA based on stress view radiographs and physical exam underwent MRI scans to assess candidacy. Exclusion criteria on MRI included lateral meniscus tears, loose bodies, grade 3-4 chondromalacia, anterior cruciate ligament (ACL) tears, sclerosis and osteoarthritis in more than one compartment of the knee (excluding the patella compartment).

Results

47.87% of patients who were candidates for medial UKA based on stress view radiographs and physical exam alone were deemed only TKA candidates based on exclusion criteria found in the preoperative MRI. Lateral meniscus and anterior cruciate ligament (ACL) tears were the two most common exclusion criteria found.

Conclusions

Preoperative MRIs, in conjunction with stress view radiographs and physical exam, should become part of the surgical decision making for UKA vs. TKA. While MRIs pose an additional cost, the current high failure rate of UKA and the high cost of conversion to TKA make it a more beneficial solution. As the indications for UKA continue to grow, superior imaging, including MRIs, are needed for surgical planning.