Woudsma, J. (2013) Validity and reliability of the EOS stereography system Alignment measurement of the lower limb in total knee arthroplasty. thesis, Medicine.
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Abstract
Background: Total knee arthroplasty (TKA) is an effective and cost-effective treatment for end-stage knee osteoarthritis (OA). During TKA it is important that correct lower limb alignment is achieved, because malalignment may lead to component loosening, abnormal component wear and patellofemoral problems. It is important to assess lower limb alignment and determine prosthesis alignment after TKA. Computer assisted surgery (CAS) has been developed for this purpose and improves postoperative lower limb alignment and reduces the outliers in malalignment. Pre- and postoperative lower limb alignment used to be determined on conventional full leg radiographs. A new imaging method, the EOS stereography system, is developed to evaluate lower limb alignment in the coronal and sagittal plane in 2D and 3D. EOS has several advantages over convential full leg radiographs and CT-scan. The amount of radiation is less compared to full leg radiographs and CT-scan. Moreover, alignment measurements are not affected by flexion and rotation of the lower limb, which is different from full leg radiographs. Other advantages over CT-scan are lower costs and the weight-bearing position during scanning. Previous research showed a significant difference between 2D and 3D alignment measurements by the EOS stereography system in patients with and without a knee prosthesis. Objective of this study was to investigate the concurrent validity and intra- and interobserver reliability of lower limb alignment measurements with the EOS stereography system in patients with before and after TKA. Methods: This study included 20 CAS-TKA’s in 17 patients. Preoperative measurements of 19 lower limbs and postoperative measurements of 16 lower limbs were analyzed. Concurrent validity was assessed by comparing pre- and postoperative measurements of EOS with CAS peroperative. Preoperative lower limb alignment was measured twice by two observers with a standard and extended 3D reconstruction. Postoperatively two observers measured the lower limb alignment twice with the standard 3D reconstruction. Intra- and interobserver reliability was determined by means of preoperative measurements with EOS. Lower limb alignment was evaluated by measuring varus/valgus angle (VV), flessum/recurvatum angle (FR), mechanical lateral distal femoral angle (mLDFA) and mechanical medial proximal tibial angle (mMPTA). Paired T-tests, Pearson correlation coefficient and Cohen’s Kappa were used to determine validity. Intra- and interobserver realiability was assessed by intraclass correlation coefficients (ICCs). Bland-Altman analyses were performed for both validity and reliability. Results: For validity, high to very high correlations were found for VV, mLDFA and mMPTA in 2D and 3D preoperatively (r=0.80-0.98). There was fair to substantial agreement for VV between EOS and CAS (κ=0.38-0.73). A significant difference of 1.92° was found for VV 3D. A bias was found between CAS and EOS, with CAS measuring on average 2.3° more varus. Postoperatively there were moderate correlations for VV in 2D and 3D (r=0.47-0.54) and poor to slight agreement was found between EOS and CAS (κ=0.00-0.07). Bland-Altman analysis showed bias for VV 3D. Intraobserver reliability was excellent for both observers, with ICCs >0.95 and >0.95. Interobserver reliability was excellent as well, with ICCs >0.94. Significant differences between measurements and observers were <1°. Discussion and conclusion: The EOS stereography system and CAS can not be used interchangeably to measure lower limb alignment, since bias exists between measurements with EOS and CAS. Preoperatively CAS measures substantially more varus alignment than 3 EOS. However, the EOS stereography provides reliable measurements of lower limb alignment in patients with end-stage OA and after TKA.
| Item Type: | Thesis (Thesis) |
|---|---|
| Supervisor name: | Stevens, Dr. M. |
| Faculty: | Medical Sciences |
| Date Deposited: | 25 Jun 2020 10:51 |
| Last Modified: | 25 Jun 2020 10:51 |
| URI: | https://umcg.studenttheses.ub.rug.nl/id/eprint/1250 |
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