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Abstract
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Introduction
Neutral alignment in total knee arthroplasty (TKA) is defined as a hip-knee-ankle angle (HKA) within 3° from neutral and is associated with improved implant survival and function. Several studies reported higher rates of inaccurate positioning and alignment outliers when using standard instrumentation and technique. However, single surgeon clinical series comparing implant positioning and alignment with standard technique (STD), patient-specific instrumentation (PSI) and navigation (NAV) are lacking. Therefore, this study aimed to compare coronal alignment and implant positioning as well as operative time when the three techniques are performed by the same surgeon.
Methods
A single surgeon series of 274 patients who underwent TKA via standard instrumentation (STD), patient-specific guides (PSI) and computer assisted surgery (NAV) was analyzed at a one-year follow-up. The three groups (STD, n=89; PSI, n=94; NAV, n=89) were matched for pre-operative coronal alignment. Pre- and post-operative HKA angles were retrospectively assessed analyzing stereoradiographic images of patients in functional position as obtained through the EOS ® System.
Alignment outliers were defined as having a deviation of more than 3° from neutral (HKA < 177° or HKA > 183°). Operative times were retrospectively assessed on patients’ operative reports.
Results
Coronal alignment as measured through the HKA was significantly different between STD and NAV groups (p=0.001), but not between STD and PSI (p=0.4) nor between PSI and NAV (p=0.1). There were 20 (23%) outliers in the STD group, 15 (17%) outliers in the PSI group and 8 (9%) outliers in the NAV group. The operative time was significantly lower in STD procedures (129 ± 3 min) and PSI procedures (126 ± 5 min) when compared with navigation (134.8 ± 9 min) (NAV: PSI p=0.03, NAV: STD p= 0.04, STD : PSI p=0.06).
Conclusion
In the present single surgeon series, TKA performed with navigation resulted in a significant improvement in implant positioning and coronal alignment when compared to standard technique. Moreover, use of navigation resulted in a significant reduction of alignment outliers. No relevant difference in terms of alignment or operative time existed between standard and patient specific instrumentation technique. However, because of the significantly longer operative time and the uncertain clinical benefit, use of navigation is still to be questioned.
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