Early Patellofemoral Function of Medial Pivot Prostheses Compared with Posterior‐Stabilized Prostheses for Unilateral Total Knee Arthroplasty

Abstract

Objective: To systematically evaluate the patellofemoral joint design of medial pivot prosthesis, which incorporates a variety of "patella-friendly" design features, by comparing clinical and radiographic results with another prosthesis. Methods: All consecutive patients who underwent unilateral total knee arthroplasty (TKA) with medial pivot prosthesis (Group MP, 126 cases) between September 2016 and April 2018 were enrolled in this retrospective study. For each patient reviewed, a control patient was matched, according to age, gender, side, body mass index (BMI), preoperative range of motion (ROM), and operating period, who had received primary unilateral TKA with a conventional posteriorstabilized prosthesis at the same period as the study group (Group PS, 126 cases). All patients underwent at least 1year follow-up. At the preoperative and final follow-up periods, data on the Knee Society Score (KSS) score, WOMAC score, Kujala score, and ROM were collected. Merchant views were taken with the knee flexion at 30 , 60 , and 90 to measure patella shift and tilt. Preoperative posterior condylar angle (PCA) was also measured. Postoperative complications, including anterior knee pain, maltracking, patellar clunk or crepitus (PCC), were evaluated. Results: There were no significant differences in the demographics or clinical characteristics between the two groups. No statistically significant difference was identified in the KSS total score, including knee score and function score, or in the Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) score between the two groups after the operation. We found statistically significant differences in the postoperative Kujala scores and the ROMs between the two groups. The mean Kujala score in group MP was better than in group PS (MP 77.16 AE 3.80 vs PS 75.97 AE 4.06, P < 0.05), while the ROM in group PS was significantly higher than in group MP (MP 122.24 AE 4.45 vs PS 123.78 AE 6.05 , P < 0.05). Simultaneously, the preoperative/postoperative Kujala score improvement in group MP was observed to be significantly larger than in group PS (MP 27.82 AE 5.31 vs PS 26.17 AE 4.89, P < 0.05), but the average ROM improvement in group PS was significantly greater than in group MP (MP 19.00 AE9.90 vs PS 21.57 AE 9.62). In the 90 Merchant view, the mean patella tilt of group MP was statistically smaller than that of group PS (MP 4.21 AE 1.62 vs PS 4.74 AE 1.95 , P < 0.05), and the average patella tilt change in group MP was significantly greater than in group PS (MP-3.8 AE 1.43 vs PS-3.23 AE 1.33 , P < 0.05). Preoperative PCA did not show significant differences between the two groups. Two cases of PCC and three cases of anterior knee pain were noted in group MP, and nine cases and six cases, respectively, were observed in group PS. The incidence of PCC was significantly lower in group MP (1.6% vs 7.1%, P < 0.05). There was no significant difference in follow-up time between the two groups. Conclusion: The medial pivot prosthesis could achieve satisfactory outcomes with b...

Medial pivot versus (cam post) posterior stabilised total knee arthroplasty, systematic review and meta-analysis of 3837 knees

“…Posterior stabilized (PS) TKAs utilise the cam-post mechanism whereby the cam-post articulates with the tibial post improving femoral rollback and at the same time providing sagittal stability (8)(9)(10)(11)(12). Despite this it is associated with central tibial impingement and increased bleeding intra-operatively secondary to the larger osteotomy (13). Moreover, these alteration in the normal knee kinematic might contribute to the knee function and the survival of the prothesis.…”

Medial pivot prosthesis has a better functional score and lower complication rate than posterior-stabilized prosthesis: a systematic review and meta-analysis

“…A total of 13 studies reported ROM [ 4 , 5 , 8 , 11 , 18 , 19 , 21 – 25 , 30 , 32 ]. Since high heterogeneity was indicated ( I 2 = 77%, P < 0.1), sensitivity analyses were conducted.…”

“…The comparison of KSS between the MP group and PS group was recorded in 10 studies [ 8 , 11 , 18 , 19 , 21 , 22 , 24 , 26 , 28 , 32 ].The included studies had significant heterogeneity ( I 2 = 89%, P < 0.1), and there was no change after sensitivity analysis. Random-effects model analysis showed that no significant difference in postoperative KSS existed between the MP group (867 knees) and PS group (809 knees) (MD = − 0.83, 95% CI − 3.01–1.35, P = 0.45) (Fig.…”

“…4 a). Seven studies reported WOMAC [ 8 , 11 , 18 , 20 , 22 , 24 , 28 ]. The fixed-effects model ( I 2 = 32%, P = 0.19) analysis showed that the WOMAC of the MP group (730 knees) was significantly lower compared with the PS group (676 knees) (MD = − 1.11, 95% CI − 1.98 to − 0.23, P = 0.01) (Fig.…”

“…Polyethylene wear is one important reason for revision of TKA [ 10 ], whereas the MP prosthesis reduces contact stress, polyethylene wear, and improves prosthesis survival rate by maximizing the contact area between polyethylene insert and femoral prosthesis. Besides, the MP prosthesis does not need an intercondylar box to accommodate columns, and such a design is beneficial to reducing bone loss and the incidence of AKP and PCC [ 8 , 11 ].…”