Alignment and early clinical outcomes following total knee arthroplasty using a handheld navigation system compared to conventional instruments

Introduction

Proper lower extremity alignment is important for success and longevity of total knee arthroplasty (TKA). Conventional instrumentation has demonstrated higher rates of mechanical axis (MA) malalignment compared to robotic or computer navigated surgery. The purpose of this study is to compare the alignment and early clinical outcomes between a handheld implant agnostic navigation system and conventional instrumentation.

Methods

117 patients who underwent single-stage bilateral TKA were prospectively studied. The distal femoral and proximal tibial resections were performed using a handheld navigation system (HHNS) on one knee and conventional instrumentation on the other knee. Implant positioning and lower extremity alignment were compared. Knee society knee score (KSKS), knee injury and osteoarthritis outcome score for joint replacement (KOOS JR), patient-reported outcomes measurement information system (PROMIS) global physical health (GPH), and patient satisfaction were compared up to one year postoperatively.

Results

There were statistically significant differences in the mean values between knees performed using HHNS compared to conventional instruments for MA (0.71° vs. − 0.32°, p = 0.0086), tibial slope (1.17° vs. 0.61°, p = 0.0165), and AP tibial component angle (0.52° vs 0.03°, p = 0.0149). No significant difference in AP femoral component position (5.65° vs. 5.60°, p = 0.87) was found. The HHNS resulted in a higher proportion of knees achieving targeted alignment for each measurement reviewed by 3–9%. Tourniquet time was approximately 6 min longer for the HHNS compared to conventional instruments (p < 0.0005). No significant difference was found for KSKS, KOOS JR, PROMIS GPH, and patient satisfaction at 1 year following surgery.

Conclusion

TKA performed with a HHNS did not result in any clinical or statistically meaningful differences regarding alignment or patient reported outcomes when compared to conventional instruments. However, a larger proportion of patients achieved surgical alignment targets for all measurements considered with use of the HHNS.