Patients who received a newer prosthesis similar to the Miller-Galante knee design showed significantly better Knee Society function scores than patients who had a long-used prosthesis to which it was compared. However, the two implants performed about the same at short-term follow-up, according to a presenter.
In a study of 81 unicompartmental knee replacements (UKR) performed in 67 consecutive patients with osteoarthritis, Alan Howieson, FRCS (T&O), and colleagues analyzed outcomes for the Zimmer Unicompartmental High-Flex Knee System (ZUK) and compared the outcomes to those for patients who had received the Oxford Partial Knee Replacement (Biomet). Two senior surgeons performed all the procedures between 2005 and 2013.
Howieson said there were no clinically detectable differences between the two groups postoperatively.
“The functional outcomes of ZUK were good at short-[term] to midterm follow-up. It is at least equivalent to the Oxford knee,” Howieson said.
No previous long-term results
Few previously published studies have evaluated the results of the ZUK prosthesis and no previous studies evaluated the long-term follow-up data, Howieson and colleagues wrote in their study. The investigators noted seven patients in the ZUK cohort and six patients in the Oxford cohort underwent either sequential or simultaneous bilateral UKR. For these patients, investigators analyzed only the first UKR performed chronologically. In simultaneous cases, a random knee was chosen.
Howieson reported a mean maximum flexion of 132° for the ZUK group and 126° for the Oxford group.
Based on the results, the researchers found no significant difference in the revision rate between the cohorts, and no revisions were required in the ZUK group. However, one patient had his or her implant washed out due to a deep infection. Howieson noted the infection seemed to be cured at 2 years postoperatively.
Three patients in the Oxford group were revised early to standard total knee replacements, according to Howieson.
Functional scores were excellent for both groups of patients, and there was no statistically significant difference in the Oxford and WOMAC scores or the Knee Society scores. Patient satisfaction was high in both cohorts, Howieson said.
The investigators noted the patients with the ZUK prosthesis experienced better Knee Society scores for function, but the improvement in those scores did not reach the minimal clinically detectable difference needed for the study.
Howieson noted 100% follow-up was possible for the patients in the ZUK group. In the Oxford UKR group, however, four patients (five knees) were lost to follow-up and one patient died.
Howieson and colleagues concluded the ZUK prosthesis provided satisfactory early performance for patients and was at least equivalent to the Oxford UKR implant. These findings justify the continued use of the ZUK prosthesis in patients with osteoarthritis, he said. – by Susan M. Rapp and Robert Linnehan
- Howieson A, et al. Paper #561. Presented at: British Orthopaedic Association Annual Congress; Sept. 15-18, 2015; Liverpool, United Kingdom.
- For more information:
- Alan Howieson, FRCS (T&O), can be reached at Department of Orthopaedic Surgery, Norfolk and Norwich University Hospitals, NHS Foundation Trust, Colney Lane, Norwich NR4 7UY, United Kingdom; email: firstname.lastname@example.org.
Disclosure: Howieson reports no relevant financial disclosures.