A recent paper of note by James Pritchett MD, FACS was published this year in the Journal of Arthroplasty (2011, 26:224-228).
The study sought to determine whether patients with well-functioning prostheses in both knees can notice differences between knee prostheses, and if so, do they have a preference? Patients were also asked the reason for their preference.
The study included 440 patients, all with staged bilateral total knee arthroplasty with a different prosthesis on each side. Average follow-up was 7 years (range, 2-14 years), mean age 68 years. This is a highly dependable study: with each patient comparing one knee against the other, patient-related variability that would normally influence results was eliminated. Exclusions included patients with fair or poor results in one or both knees to avoid comparing a fair or poor result to a good or excellent result; all patients had a good or excellent result in both knees. The medial pivot design used is based on the Medial Rotation Knee™, first implanted in the UK in 1994.
More than 90% of patients had a preference for one knee prosthesis over the other. Overwhelmingly, 76% preferred the medially rotating design over both the posterior stabilised knee or PCL retaining knee, and 61% preferred it over the mobile bearing knee.
Patients gave the following reasons for preferring one knee over the other:
feels more normal
stronger on stairs
superior single-leg weight bearing
feels more stable overall
fewer clunks, pops, clicks
There were no important differences in the mean pain score, range of motion, knee score or function score between types of prosthesis and all knees were well fixed (radiographic assessment). This agrees with many other studies in that many postoperative assessment measures do not distinguish between well functioning prostheses. Despite this, it is worthy of note that the medial pivot knee was associated with the greatest mean range of motion of all knees (125°) and the greatest mean knee score (80.4.)
In agreement with the study by Hossain et al., the results of this study indicate that the medially rotating design provides a level of stability and a more natural kinematic profile that results in improved patient satisfaction.