Assessment Of Coronal Alignment And Its Effect On Functional Outcomes In Unicompartmental Knee Arthroplasty

Background and Aim: Unicompartmental knee arthroplasty is an established treatment approach for isolated single compartment.It has more advantages compare to total knee arthroplasty such as preservation of anterior cruciate ligament and natural knee kinematics,low costs,easier revision TKA,and fast recovery.The aim of this study was to assess the percentage of Varus deformity,observe the correction rate and identify the main causes of varus deformity.And to evaluate its impact on short term functional outcomes after UKA.Methods: A single-center study at our hospital that involved a retrospective analysis.All the patients who undergone UKA surgery were included from Oct 2015-Aug 2018 in the study.The mean of follow up was 22.5±24.75(range 5-40 mo),and was obtained by telephone inquiry.Pre and postoperative full leg length X-ray were asses for coronal alignment.All the cases were divided into neutral alignment(0-3°)group and varus alignment(>3°)according to postoperative coronal alignment.45(72.58%)cases with neutral alignment and 17(27.42%)cases with varus alignment were investigated.To evaluate the clinical outcomes two scores Hospital for Special Surgery score(HSS)and Western Ontario and McMaster University Arthritis Index(WOMAC)were used.All statistical analyses were performed using SPSS 15.0 statistics software.A two-sided P<0.05 was considered as statistically significant.Results: A total 53(62 knees)patients were involved in this study.The mean age was 67.87±7.738(range 52-88 yo).The number of female cases was higher which is 43 knees(69.35%)compare to male cases 19 knees(30.65%).According to preoperative coronal alignment measurement there were 17 cases with neutral alignment have analyzed.The varus alignment 45 cases including 14 cases with extra-articular deformity and 31 cases of intraarticular deformity was observed.The postoperative coronal alignment measurement shows 45 cases of neutral alignment and 17 cases of varus alignment including 13 cases with extra-articular and 4 cases of intra-articular problem.The correction rate of postoperative varus alignment was 62.22%(28/45).The pre and postoperative HSS scores mean have significantly improve from 52.89±15.73 to 92.79 ±9.518(P< 0.001).Similarly,the WOMAC index also improved in pain mean from 14.5±3.297 to 1.477±1.753(P< 0.001),in the stiffness mean from 3.316±2.548 to 0.509±0.953(P< 0.001),and the physical functions mean from 43.03±9.972 to 5.897±7.149(P< 0.001).Paired t-test was used for difference means between pre and post-operative.The postoperative HSS scores of the neutral alignment group and the varus alignment group were 93.11±8.52 and 91.94±12.02(p=0.6696),respectively.There was no significant difference between the two groups.The WOMAC index of the neutral alignment group and the varus alignment group was 2.566 ±5.123 and 2.792 ±4.16(p=0.7782),respectively.There was no significant difference in postoperative clinical efficacy among two groups.Unpaired t test was used to evaluate patients in both groups.Conclusion: UKA for the treatment of medial compartment osteoarthritis can significantly alleviate pain and improve the patient's knee function.Patients with medial compartment OA may be associated with proximal tibial joint varus deformity.As unicompartmental knee replacement can only correct intra-articular deformity,these patients are prone to residual varus deformity of the lower limb postoperatively,but such varus of the lower limb does not affect short-term functional recovery of patients after the surgery.Our study suggests that patients accepted UKA,pre and postoperative knee functional score have significant improvements.HSS score and WOMAC index results suggest,neutral alignment(0 to 3 °)and varus alignment(3-7 °)there was no statistical difference in clinical outcomes after surgery.The minor varus deformity between 0 to 7 ° is acceptable in UKA surgery.