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UKA produced fewer knee bending problems 2 years postoperative than TKA
Lygre SHL. J Bone Joint Surg (Am). 2010;92:2890-2897. doi:10.2106/JBJS.I.00917.
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Norwegian researchers found similar pain and function scores at 2 years’ postoperative in patients who underwent unicompartmental or total knee arthroplasty. The patients who underwent unicompartmental knee arthroplasty had fewer problems bending their knees.
The researchers collected patient-reported data on pain and function from 972 patients listed on the Norwegian Arthroplasty Register has having had an unrevised primary total knee arthroplasty (TKA) or 372 who underwent an unrevised unicompartmental arthroplasty (UKA). All 1,344 patients underwent TKA or UKA to treat their arthritis, and all those included were at least 2-years post surgery.
Stein Håkon Låstad Lygre, MD, Haukeland University Hospital, Bergen, Norway, and colleagues assessed outcomes with the following: five subscales from the Knee Injury and Osteoarthritis Outcome Score, Visual Analog Scale scores on the degree of pain and satisfaction with surgery, and the change in index score on the EuroQol-5D health-related quality of life instrument. In addition, they used the 42 questions from the Knee Injury and Osteoarthritis Outcome Score.
To reach clinical significance, the differences had to be eight units for the Knee Injury and Osteoarthritis Outcome Score outcomes, 10 units for the pain and satisfaction scales, and 0.4 units for the detailed Knee Injury and Osteoarthritis Outcome Score questions.
The results showed that the UKA patients performed better on the Knee Injury and Osteoarthritis Outcome subscales for symptoms (adjusted mean difference, 2.7; P=.04), function in daily living (adjusted mean difference 4.1; P=.01) and function in sport and recreation (adjusted mean difference, 5.4; P=.006). Of the 42 questions from the Knee Injury and Osteoarthritis Outcome Score, four differences were significant and in favor of UKA; however, only the question “Can you bend your knee fully?” reached clinical significance.
This paper compares patient-reported outcomes of unicondylar and total knee arthroplasty in a sampling of a national joint implant registry 2 years post surgery. The study demonstrates that both unicondylar and total knee arthroplasty can improve knee function in patients with gonarthrosis, with slightly better scores in the unicondylar group. Faster postoperative recovery and return of function have been previously reported for unicondylar knees, as has generally better range of motion.
The authors surmise that better self-reported sports performance for the unicondylar knees may be attributable to ligament and motion preservation, and this is the first study that demonstrates this finding, although the baseline performance is not included. Pain after knee arthroplasty can be multifactorial and without radiographic or clinical analysis; few assumptions can be made regarding pain scoring.
Knee arthroplasty is technically challenging, and the impact of surgeon volume or selection bias was not assessed in this study. In general, surgeons do many more total knees than unicondylar replacements and may have more adequate skills for the former.
Long-term registry follow-up may help define proper patient selection criteria, best surgical techniques and superior implant performance. I look forward to future reports.
— David A. Fisher, MD
Director Total Joint Center
OrthoIndy, Indiana Orthopedic Hospital
Indianapolis, Indiana