Measuring Tibial Component Rotation Following Total Knee Arthroplasty: What Is the Best Method?

Background Computed tomography (CT) can be used to assess the rotational alignment of prosthesis components to identify possible underlying causes of symptomatic total knee arthroplasty (TKA). The use of cone beam computed tomography (CBCT) for the imaging of extremities is relatively new, although it has been widely used in dental imaging. Purpose To assess the intra- and inter-observer reproducibility of CBCT, as well as to validate CBCT for TKA component and periprosthetic bone diagnostics. Material and Methods CBCT scans were performed on 18 patients the day before a scheduled revision TKA, from which the intra- and inter-observer reproducibility were assessed. Component rotation and loosening were evaluated. Perioperative bone defects were classified. Results The inter-observer intraclass coefficient correlation (ICC) for femoral component rotation was 0.41 (95% confidence interval [CI] = 0.12–0.69). For the tibial component, the ICC was 0.87 (95% CI = 0.74–0.94). Intra-observer reproducibilities were 0.70 (95% CI = 0.35–0.87) and 0.92 (95% CI = 0.80–0.97), respectively. The sensitivity for tibial component loosening was 97% and the specificity was 85%. The reliability of bone defect classification was only weak to moderate. Conclusion Two-dimensional (2D) CBCT scanning provides reliable and reproducible data for determining the rotation of femoral and tibial components, while showing minor overestimation of tibial component loosening. CBCT is a promising new tool for the evaluation of symptomatic knee arthroplasty patients, with a substantially lower radiation dose compared to conventional 2D multi-slice CT.

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The type of approach (medial versus lateral) influences TKA component rotation in total knee arthroplasty - a clinical study using 3D-CT

Orthopaedic Journal of Sports Medicine ◽

10.1177/2325967118s00010 ◽

2018 ◽

Vol 6 (4_suppl2) ◽

pp. 2325967118S0001

Author(s):

Filippo-Franco Schiapparelli ◽

Felix Amsler ◽

Michael Hirschmann

Keyword(s):

Total Knee Arthroplasty ◽

Knee Arthroplasty ◽

Tibial Component ◽

Tibial Tubercle ◽

Component Position ◽

Tibial Tubercle Osteotomy ◽

Subvastus Approach ◽

Leg Axis ◽

Component Rotation ◽

Total Knee

The purpose of this study was to investigate if the type of approach (medial parapatellar approach (MPA) versus lateral parapatellar subvastus approach with tibial tubercle osteotomy (LPA)) influences the rotation of femoral and/or tibial component and leg axis in total knee arthroplasty (TKA). This study included 200 consecutive patients in whom TKA was performed using either a parapatellar medial (n=162, MPA) or parapatellar lateral subvastus approach with tibial tubercle osteotomy (n=38, LPA). All patients underwent clinical follow-up, standardised radiographs and computed radiography (CT). TKA components’ position and the whole leg axis were assessed on 3D reconstructed CT scans (sagittal, coronal and rotational). Mean values of TKA component position and the whole leg alignment of both groups were compared using a T-test. The tibial component was graded as internally rotated (< 3° of external rotation (ER)), neutral rotation (equal or between 3° and 6° of ER) and and externally rotated (>6° ER). The femoral component was graded as internally rotated (< 3° of internal rotation (IR)), neutral rotation (equal or between -3° IR and 3° of ER) and externally rotated (>3° ER). There was no significant difference in terms of whole leg axis after TKA between both groups (MPA: 0.2° valgus ± 3.4; LPA: 0.0° valgus ± 3.5). Means of tibial component position were 2.7° ER ± 6.1 (MPA) and 7.6° ER ± 5.4 (LPA). Patients of group LPA presented a significantly less internally rotated (LPA: 18.4%; MPA: 48.8%) and more externally rotated (LPA: 52.6%; MPA: 22.8%) tibial component (p<0.001). No significant differences were seen for the femoral component position, tibial valgus/varus and tibial slope. The type of approach significantly influences the tibial TKA component rotation. It appears that a MPA tends to internally rotate the tibial TKA component and a LPA tends to externally rotate the tibial TKA.

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