From January 2014 to January 2015, a total of 241 patients (252 knees) with advanced osteoarthritis were treated with CR and PS TKA in our hospital. All patients provided informed consent to participate. This study was approved by our hospital institutional ethics committee. (Study No. 2014-K-076).
The inclusion criteria were as follows:
(1) Severe osteoarthritis (Kellgren–Lawrence grade > III)
(2) Substantial pain and loss of function in the knee
(3) Primary total knee replacement
The exclusion criteria were as follows:
(1) History of high tibial osteotomy in the knee or contralateral total knee replacement
(2) Hemophilia or juvenile rheumatoid arthritis
(3) Severe bony defect, valgus deformity, revision TKA, or active knee joint infection
(4) Concomitant performance of another surgery with the TKA, such as ligament repair
Based on these criteria, 210 patients were included in this study; among them, 102 patients underwent CR TKA and 108 underwent PS TKA. The demographic data were compared between the two groups (Table 1). All patients underwent clinical follow-up for at least 5 years after surgery.
The follow-up parameters were the Knee Society Score (KSS), range of motion (ROM), patient satisfaction, patellar stability, and complications.
Table 1
Demographics of the patients
|
CR
|
PS
|
P value
|
No. of patients
|
102
|
108
|
n.s.
|
Sex (male/female)
|
42/60
|
43/65
|
n.s.
|
Side involved (right/left)
|
54/48
|
53/55
|
n.s.
|
Age (years)
|
67 ± 5
|
65 ± 4
|
n.s.
|
BMI (kg/m2)
|
31 ± 4
|
32 ± 5
|
n.s.
|
Kellgren & Lawerence III
|
20
|
31
|
|
Kellgren & Lawerence IV
|
82
|
77
|
n.s.
|
Passive flexion
|
87 ± 7
|
90 ± 5
|
|
Passive extension
|
14 ± 5
|
15 ± 7
|
n.s.
|
Follow-up time (months)
|
60 ± 4
|
60 ± 3
|
n.s.
|
Surgical technique
All surgical procedures were performed by a senior surgeon. A pneumatic tourniquet was used for all cases. A standard medial parapatellar approach was performed in all surgeries. All tibial and femoral components were cemented, incorporating a posterior referencing guide for sizing the femoral component. Sequential soft tissue release was performed if the flexion and extension gaps were not balanced.
All patients underwent patelloplasty in which an oscillating saw was used to trim the patella. No patients underwent patellar replacement. No drainage tube was used in any cases. The Gemini MK II CR TKA prosthesis (Link, Hamburg, Germany) and Gemini Legacy PS TKA prosthesis (Zimmer Biomet, Warsaw, IN, USA) were used in our experiment.
Postoperative rehabilitation training
All patients were given rehabilitation instructions and training by a rehabilitation team. After the operation, walking was encouraged on the day of surgery under the supervision of a physiotherapist. Walking and active ROM exercises were conducted by the rehabilitations every day after the operative procedure.
A follow-up evaluation was scheduled 5 years postoperatively. This postoperative follow-up was completed by the same follow-up team and involved assessment of the KSS, ROM, patellar stability, and complications.
Passive postoperative flexion and extension were measured using a standard goniometer with the patient in the supine position. Patellar grinding, catching, and clunking were tested and recorded. Postoperative radiographs were reviewed, and the position of the implant, Insall-Salvati ratio, and joint line position were evaluated.
Patellar stability was evaluated with the apprehension test, and the patients were divided into three groups according to the test result: those with patellar stability, subluxation, and dislocation. According to the lateral translation grade, grades I and II with a hard end point were consistent with patellar stability, grade III with a hard end point was consistent with patellar subluxation, and a soft end point was consistent with patellar dislocation. Grade > III was also consistent with patellar dislocation. Radiographic evaluation included the patellar tilt and the patellar lateral shift.
Statistical analysis
SPSS statistical software, version 20.0 (IBM Corp., Armonk, NY, USA) was used for the statistical analysis. A t-test or nonparametric test was used to compare the measurement data among the groups, and the chi-square test or a nonparametric test was used to compare the count data. A p value of < 0.05 indicated a statistically significant difference.