Effect of arthritis in other compartment after unicompartmental arthroplasty

The purpose of this study is to evaluate the outcome of robotic-assisted (MAKO Surgical Corp.) unicondylar replacement in the treatment for knee osteoarthritis after the initial surgical insult is worn off to evaluate the impact of residual patellofemoral and lateral osteoarthritis on the outcome of medial unicompartmental knee replacement. One hundred and thirty-four patients who underwent uncomplicated 144 robotic-assisted medial unicondylar replacements for knee arthritis were identified and studied. Original radiographs were used to classify severity of patellofemoral and lateral compartmental osteoarthritis in these patients. Severity of patellofemoral and lateral compartmental osteoarthritis was analyzed against Oxford and Knee Society scores and amount of ipsilateral residual knee symptoms at 6 months postoperative period. Preoperative Oxford and Knee Society scores, other comorbidities and long-term disability were studied as confounding variables. We found significant improvement in symptoms and scores in spite of other compartment diseases. Poorer outcome was seen in association with comorbidities and long-term disability but not when radiographic signs of arthritis in the other compartments were present. Six patients required revision of which three had (lateral facet) patellofemoral disease in the original X-rays. In conclusion, there is a higher amount of postoperative retained symptoms, but similar outcome when there is radiographic disease in the other compartments. However, when symptoms are severe enough to necessitate revision, this is due to the lateral facet of patellofemoral compartment and not lateral compartment disease.