The Journal of Arthroplasty , Volume 34 , Issue 3 , 483 - 487

The Learning Curve by Operative Time for Soft Tissue Balancing in Total Knee Arthroplasty Using Electronic Sensor Technology

Lakra, Akshay et al.


Electronic sensor devices can provide an objective assessment of soft tissue balancing in total knee arthroplasty (TKA) which may potentially decrease postoperative pain. We aim to quantify the learning curve for operative time (OT) for this technology.


Consecutive TKA cases balanced with an electronic sensor balancing device by one senior surgeon from 2013 to 2017 were included in this study. The OT (in minutes) was analyzed using the cumulative sum analysis to evaluate the learning curve for this technology. Further analysis was done by splitting the 287 patients into 7 cohorts, 41 patients each.


Two hundred eighty-seven patients balanced with sensor technology were available for analysis. The cumulative sum OT learning curve estimated that this technology’s learning curve was 41 cases. This curve consisted of 2 phases: phase 1 which includes the first 41 cases and phase 2 which includes the remaining 246 patients. The mean OT for the first and last sensor-assisted cohorts was 120.4 and 108.9 minutes (P = .021). The mean OT for the first sensor-assisted cohort and the control cohort was 120.4 versus 109 minutes (P = .023). The mean OT for the last sensor-assisted cohort and the control cohort was 108.9 versus 109 minutes (P = .94).


Our findings suggest that it takes approximately 41 cases of sensor-assisted TKA cases to achieve OTs identical to manually balanced TKA cases. This is a relatively shallow learning curve for the sensor technology, and allows arthroplasty surgeons to objectively achieve soft tissue balancing without adding OT to the surgery.

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