ArticleArthroplasty (London, England)2026
Accuracy of digital inclinometers for measuring knee extension during total knee arthroplasty: comparison with visual estimation and computer navigation.
Article in Arthroplasty (London, England), 2026. The graph could read no effect estimate from its abstract, so it casts no vote on the map. Not yet cited in PubMed.
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Abstract
backgroundAccurate intra-operative assessment of knee extension angle is essential in total knee arthroplasty (TKA), as residual flexion contracture or hyperextension is associated with inferior post-operative function and increased implant wear. Visual estimation remains widely used, but prior research has demonstrated substantial inaccuracy. This study evaluated the accuracy and reliability of a digital inclinometer technique for measuring knee extension angle during TKA, using computer navigation as the reference standard.
methodsA prospective comparative study was performed on 130 knees undergoing primary posterior-stabilized TKA. After trial implant insertion, knee extension was assessed using two methods: visual estimation and a digital inclinometer method utilizing the femoral chisel holder and anterior border of the tibial crest. All measurements were compared with OrthoPilot navigation. Accuracy was defined as measurements within ± 2° of navigation. Correlation, agreement, and intra- and inter-observer reliability were evaluated.
resultsVisual estimation underestimated extension and showed a mean difference of - 3.5° ± 4.1° versus navigation (p < 0.001). The proportion of knees within ± 2° of navigation was only 26.2%. In comparison, the digital inclinometer demonstrated a significantly smaller mean difference of 0.1° ± 1.6° (p = 0.753), with 86.9% of knees meeting the ± 2° accuracy threshold. Superiority of the inclinometer persisted across all subgroups of pre-operative deformity. Correlation with navigation was weak for visual estimation (r = 0.320; r
conclusionThe digital inclinometer technique provides accurate and reproducible intra-operative knee extension measurements, outperforming visual estimation and approximating navigation-based assessment. This low-cost approach is feasible where navigation is unavailable.
trial registrationThai Clinical Trials Registry (TCTR20180828002). Registered on 28 August 2018. Prospectively registered.
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