An accelerometer-based portable navigation system improved prosthetic alignment after total knee arthroplasty in 3D measurements.
PURPOSE
This study aimed to compare prosthetic alignment using three-dimensional (3D) measurements following total knee arthroplasty (TKA) performed using an accelerometer-based portable navigation system (KneeAlign2) versus the conventional technique.


METHODS
A total of 159 patients who had primary osteoarthritis of the knee with varus deformity underwent TKA. The KneeAlign2 system was used for distal femoral resection and tibial resection in 78 knees, and the conventional instrumentation (intramedullary for the femur and extramedullary for the tibia) was used in 81 knees. 3D computed tomography (CT) scans of the whole leg were taken after TKA. Femoral and tibial prosthetic alignments in the coronal, sagittal, and axial planes were measured using computer software. The operation time and estimated blood loss were calculated. Deep venous thrombosis (DVT) and pulmonary embolism (PE) were evaluated using the contrast-enhanced multi-detector row CT at 1 week after TKA.


RESULTS
In the femoral coronal plane, the mean and standard deviation of prosthetic alignment from neutral alignment were 1.2° [95% confidence interval (CI) 1.0°-1.4°) in the navigation group and 1.6° (95% CI 1.3°-2.0°) in the conventional group (p = 0.03). The femoral component outliers (> 3° away from the goal alignment) using the navigation system and the conventional technique were 3 and 15%, respectively, in the coronal plane (p < 0.01), and 15 and 43%, respectively, in the sagittal plane (p < 0.01). The outliers in tibial coronal and tibial sagittal planes were not statistically different between the two groups. There were no statistically significant differences between the two groups in operation time, blood loss, DVT, and PE.


CONCLUSION
Using an accelerometer-based portable navigation system decreased the outliers of prosthetic alignment in femoral coronal and sagittal planes, and did not increase the complications such as operation time, blood loss, DVT, and PE. To our knowledge, this study is the first to investigate the usefulness of an accelerometer-based portable navigation system using the validated 3D measurement.


LEVEL OF EVIDENCE
III.
['Ueyama|Hideki|H|', 'Minoda|Yukihide|Y|', 'Sugama|Ryo|R|', 'Ohta|Yoichi|Y|', 'Yamamura|Kazumasa|K|', 'Nakamura|Suguru|S|', 'Takemura|Susumu|S|', 'Nakamura|Hiroaki|H|']
D061725:Accelerometry D000368:Aged D000369:Aged, 80 and over D019645:Arthroplasty, Replacement, Knee D003287:Contrast Media D005260:Female D005269:Femur D006801:Humans D021621:Imaging, Three-Dimensional D007717:Knee D007719:Knee Joint D008297:Male D008875:Middle Aged D061646:Operative Time D020370:Osteoarthritis, Knee D011184:Postoperative Period D011474:Prosthesis Design D011655:Pulmonary Embolism D025321:Surgery, Computer-Assisted D013977:Tibia D014057:Tomography, X-Ray Computed D020246:Venous Thrombosis
Accelerometer-based portable navigation system Alignment Total knee arthroplasty Outlier Three-dimensional assessment