Patellar height before and after unicompartmental knee arthroplasty: association with early clinical outcome?
BACKGROUND
There is paucity of information available concerning the role of patellar height in unicompartmental knee arthroplasty (UKA). The present study was conducted to determine the patellar height before and after UKA and to assess possible effects on the early clinical outcome.


METHODS
We measured the patellar height before and after UKA in 83 consecutive knees using the Blackburne-Peel (BP) index and Insall-Salvati (IS) ratio and investigated the impact of the patellar height on the clinical outcome 2 years after surgery.


RESULTS
BP values significantly decreased from 0.81 before surgery to 0.76 postoperatively (P < 0.001). IS ratios did not significantly decrease from 1.02 to 1.01 (P = 0.108). Lower preoperative BP values were negatively correlated with the postoperative knee extension (r = -0.357, P = 0.026), while higher preoperative BP values were negatively associated with the postoperative Knee Society Score (r = -0.302, P = 0.046). Lower preoperative IS values were negatively correlated with postoperative Knee Scores (r = -0.394, P = 0.019).


CONCLUSIONS
After UKA, the patellar height decreased significantly according to the BP index, but not significantly according to the IS ratio. We found only weak and inconsistent correlations between the patellar height and clinical outcome parameters. Hence, based on the present results, the patellar height seems not to be a strict separate patient-selection criterion for UKA.
Department of Orthopaedic Surgery, Joint Center, Schulthess Clinic, Lengghalde 2, 8008 Zurich, Switzerland. florian.naal@gmail.com
Florian D
FD
Naal
Carl
C
Neuerburg
Fabian
F
von Knoch
Gian M
GM
Salzmann
Monika
M
Kriner
Urs
U
Munzinger
D000368:Aged; D000369:Aged, 80 and over; D019645:Arthroplasty, Replacement, Knee; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000033:anatomy & histology; D008297:Male; D008875:Middle Aged; D010329:Patella / Q000033:anatomy & histology* / Q000000981:diagnostic imaging; D011184:Postoperative Period; D011379:Prognosis; D011859:Radiography; D016896:Treatment Outcome