Summary

Robotic assisted total knee arthroplasty can add further benefit to navigation assisted total knee arthroplasty.

Abstract

Introduction

As the demand for primary total knee arthroplasty(TKA) increases, newer technology like robot assisted TKA(RTKA) has gained recent popularity. Computer navigation assisted TKA(NTKA) has been used for the past two decades for more accurate implant positioning as compared to conventional-jig based TKA. RTKA has the added advantage of a robotic arm completing bony cuts to reduce technical errors. Additionally, the ability to implement alternative alignment philosophies allowing for better component positioning to balance gaps may reduce the need for soft tissue releases, especially in severe deformities. To the best of our knowledge, there are no studies comparing the outcomes of NTKA and RTKA. The aim of our study is to compare the clinical outcomes of RTKA and NTKA in a)all patients and b)subgroup analysis of mild and severe varus deformity.

Methods

We prospectively recruited all patients undergoing primary TKA at a single tertiary care center by a single surgeon from January 2023 until December 2023. We recruited 179 consecutive TKA, 90 in NTKA group and 89 in RTKA group. The surgeon was experienced in NTKA for two decades before transitioning to RTKA in January 2023, with the patients in this study being the first RTKA performed by the surgeon. All patients received a posterior stabilized cemented implant with patella resurfacing, using a functional alignment strategy of 3º limit from neutral for overall coronal alignment. Clinical outcomes were assessed using flexion and New Knee Society Score(NKSS). The intraoperative soft tissue release(STR) rate, i.e. release of the superficial medial collateral ligament was recorded. Comparison between NTKA and RTKA was made in the total cohort and in the mild(<10º) and severe(≥ 10º) varus cohort. Student T test, Mann Whitney U test and Fisher Exact test were used for statistical analysis.

Results

Total Cohort:
There was no difference(p>0.05) in preoperative general demographics. There was no difference in preoperative(p=0.45) and postoperative(p=0.11) NKSS. RTKA patients had a greater improvement in NKSS(p<0.05) and function score(p<0.05) compared to NTKA at 3 months.

Mild varus cohort:
There were 28 NTKA and 29 RTKA in the mild varus cohort. The preoperative age(p=0.41), BMI(p=0.88), sex(p=0.31) and NKSS(p=0.18) were comparable between the two groups. The intraoperative STR rate(p=0.97) and postoperative NKSS(p=0.98) and flexion(p=0.87) were comparable between the two groups.

Severe varus cohort:
There were 62 NTKA and 60 RTKA in the severe varus cohort. The preoperative age(p=0.65), BMI(p=0.59), and NKSS(p=0.98) were comparable between the two groups. The incidence of intraoperative STR was greater(p=0.02) in NTKA(54.8%) as compared to RTKA(33.3%) patients. At 3 months post TKA, flexion(p=0.02) was higher and NKSS(p=0.09) was trending higher in RTKA group.

Conclusion

RTKA can benefit a surgeon experienced in NTKA by reducing need for soft tissue releases in severe varus deformities. Postoperative improvement in scores was found to be significantly more with RTKA at 3 months, when the entire cohort was considered for comparison. Longer term studies are required to identify clinical benefits of RTKA and we plan to continue following these patients, with 1 year post TKA results available by the end of this year.