Impact of joint line orientation on clinical outcomes in bilateral Oxford mobile-bearing unicompartmental knee arthroplasty.
BACKGROUND
Joint line orientation angle (JLOA) is the angle between the knee joint line and the floor. It has been reported to be related to postoperative outcome after TKA. Regarding unicompartmental knee arthroplasty (UKA), although it can be horizontal after UKA because it is a resurfacing surgery, there are few reports about the JLOA after UKA and its impact on clinical outcomes.


PURPOSE
The purpose of this study was to reveal the relationship between JLOA and clinical outcome after UKA.


METHODS
This study included 106 knees in 53 consecutive patients with osteoarthritis who underwent simultaneous bilateral mobile-bearing UKA. Their pre- and postoperative JLOAs were measured by full-leg-length standing coronal radiographs. We also evaluated the tibial component height (TCH) as the factor which we assumed could influence JLOA. We analyzed the patients' JLOAs, TCHs and clinical outcomes.


RESULTS
Pre- and postoperative JLOA were 0.4 ± 2.4° and 2.7 ± 2.6°, respectively. The JLOA significantly tilted medially (P < 0.0001). The JLOA significantly negatively correlated with the improvement of the clinical outcomes (Oxford Knee Score (OKS): r = 0.40, P < 0.0001, Knee Society Knee Score (KSKS): r = 0.25, P < 0.01, Knee Society Function Score (KSFS): r = 0.22, P = 0.02). The TCH showed a positive correlation with postoperative JLOA and with the postoperative JLOA change (r = 0.45, P < 0.001; r = 0.25, P < 0.01, respectively).


CONCLUSION
The JLOA significantly tilted medially after UKA. An excessive medial tilt of the JLOA was associated with poorer postoperative outcomes of UKA. It is therefore recommended to keep the JLOA horizontal and to avoid a lower tibial cut.
['Nishida|Ryota|R|', 'Hiranaka|Takafumi|T|', 'Kamenaga|Tomoyuki|T|', 'Hida|Yuichi|Y|', 'Fujishiro|Takaaki|T|', 'Okamoto|Koji|K|', 'Kuroda|Ryosuke|R|', 'Matsumoto|Tomoyuki|T|']
D000368:Aged D019645:Arthroplasty, Replacement, Knee D005260:Female D006801:Humans D007719:Knee Joint D007720:Knee Prosthesis D008297:Male D020370:Osteoarthritis, Knee D000071066:Patient Reported Outcome Measures D011859:Radiography D012189:Retrospective Studies
Unicompartmental knee arthroplasty Joint line orientation angle (JLOA) Alignment Oxford partial knee