- Email: [email protected]
Reply to the letter by Liang Cheng, Yong Zhu and Hai-Tao Long
Lettres à la rédaction / Revue de chirurgie orthopédique et traumatologique 102 (2016) 683–687
685
Reply to the letter by Liang Cheng, Yong Zhu and Hai-Tao Long夽 These comments about our article entitled ‘Radial head replacement in adults with recent fractures’ are relevant, and we are grateful to their authors. Supination and pronation put tension on the anterior band and posterior band, respectively, of the flexor retinaculum. However, the work performed by Martin BF disregarded translation, which has been described in great detail by Weiss et al. as capable of correcting the difference in tension between the anterior and posterior bands. Thus, the point most deserving of emphasis is that both pronation and supination increase the overall tension on the flexor retinaculum, thereby inducing coaptation of the proximal radioulnar joint. Tension on the flexor retinaculum is therefore at its lowest when the forearm is in the neutral position. We trust this additional information will enable the readers to fully understand our work. Disclosure of interest The author declares that he has no competing interest. N. Bonnevialle CHU de Toulouse, 31059 Toulouse, France E-mail address: [email protected] DOIs
of
original
articles:
http://dx.doi.org/10.1016/j.otsr.2016.06.002,
http://dx.doi.org/10.1016/j.rcot.2016.06.014 夽
Ne pas utiliser, pour citation, la référence franc¸aise de cet article, mais
celle de l’article original paru dans Orthopaedics & Traumatology: Surgery & Research, en utilisant le DOI ci-dessus.
http://dx.doi.org/10.1016/j.rcot.2016.09.005
Comments on “Reproducibility of digital measurements of lower-limb deformity on plain radiographs and agreement with CT measurements” by G. Sorin, G. Pasquier, E. Drumez, A. Arnould, H. Migaud, S. Putman published in Orthop & Traumat: Surgery & research 2016,102: 423–28. Common mistake and methodological issue to avoid mismanagement夽 We were interested to read the paper by Sorin G. et al. published in the June 2016, issue of Orthop Traumatol Surg Res. Five angles (HKA, HKS, alpha, beta, tibial slope) are used for goniometry in total knee arthroplasty [1]. They aimed to: (1) evaluate the inter- and intrarater reliability of the measurement of these angles on digital x-rays taken on a PACS; (2) determine the agreement of these measurements with those obtained using a CT protocol [1]. They used interclass correlation (Pearson) and kappa coefficients. Reliability (precision, repeatability or reproducibility) is an important methodological issue. Reliability is being assessed by different statistical tests including interclass correlation coefficient or Pearson r which is one of the common mistakes in reliability analysis (Fig. 1) [2–7]. Briefly, for quantitative variable intra class correlation coefficient (ICCC) single measure and for qualitative variables weighted kappa should be used with caution because
夽 Ne pas utiliser, pour citation, la référence franc¸aise de cet article, mais celle de l’article original paru dans Orthopaedics &Traumatology: Surgery & Research, en utilisant le DOI ci-dessus.
Fig. 1. Cases when Pearson coefficient fails to detect non reproducibility.
simple kappa has its own limitation (Table 1) [3,4,8–10]. Two important weaknesses of k value to assess agreement of a qualitative variable are as follow: it depends upon the prevalence in each category which means it is possible to have different kappa value having the same percentage for both concordant and discordant cells! Table 1 shows that in both (a) and (b) situations the prevalence of concordant cells are 80% and discordant cells are 20%, however, we get different kappa value (0.38 as fair and 0.60 as moderate - good) respectively. Kappa value also depends upon the number of categories which means the higher the categories, the lower the kappa value.[2–8]. Therefore, reporting weighted kappa can be highly recommended. [3,4,8–10]. As the authors pointed out in their conclusion, the HKA, alpha, and beta angles were reproducible for digital radiographs and showed good agreement with CT measurements. Such conclusion may be a misleading message due to inappropriate use of statistical tests. In conclusion, for reliability analysis, appropriate tests as well as correct interpretation should be applied. Otherwise, misdiagnosis and mismanagement of the patients cannot be avoided.
685
Reply to the letter by Liang Cheng, Yong Zhu and Hai-Tao Long夽 These comments about our article entitled ‘Radial head replacement in adults with recent fractures’ are relevant, and we are grateful to their authors. Supination and pronation put tension on the anterior band and posterior band, respectively, of the flexor retinaculum. However, the work performed by Martin BF disregarded translation, which has been described in great detail by Weiss et al. as capable of correcting the difference in tension between the anterior and posterior bands. Thus, the point most deserving of emphasis is that both pronation and supination increase the overall tension on the flexor retinaculum, thereby inducing coaptation of the proximal radioulnar joint. Tension on the flexor retinaculum is therefore at its lowest when the forearm is in the neutral position. We trust this additional information will enable the readers to fully understand our work. Disclosure of interest The author declares that he has no competing interest. N. Bonnevialle CHU de Toulouse, 31059 Toulouse, France E-mail address: [email protected] DOIs
of
original
articles:
http://dx.doi.org/10.1016/j.otsr.2016.06.002,
http://dx.doi.org/10.1016/j.rcot.2016.06.014 夽
Ne pas utiliser, pour citation, la référence franc¸aise de cet article, mais
celle de l’article original paru dans Orthopaedics & Traumatology: Surgery & Research, en utilisant le DOI ci-dessus.
http://dx.doi.org/10.1016/j.rcot.2016.09.005
Comments on “Reproducibility of digital measurements of lower-limb deformity on plain radiographs and agreement with CT measurements” by G. Sorin, G. Pasquier, E. Drumez, A. Arnould, H. Migaud, S. Putman published in Orthop & Traumat: Surgery & research 2016,102: 423–28. Common mistake and methodological issue to avoid mismanagement夽 We were interested to read the paper by Sorin G. et al. published in the June 2016, issue of Orthop Traumatol Surg Res. Five angles (HKA, HKS, alpha, beta, tibial slope) are used for goniometry in total knee arthroplasty [1]. They aimed to: (1) evaluate the inter- and intrarater reliability of the measurement of these angles on digital x-rays taken on a PACS; (2) determine the agreement of these measurements with those obtained using a CT protocol [1]. They used interclass correlation (Pearson) and kappa coefficients. Reliability (precision, repeatability or reproducibility) is an important methodological issue. Reliability is being assessed by different statistical tests including interclass correlation coefficient or Pearson r which is one of the common mistakes in reliability analysis (Fig. 1) [2–7]. Briefly, for quantitative variable intra class correlation coefficient (ICCC) single measure and for qualitative variables weighted kappa should be used with caution because
夽 Ne pas utiliser, pour citation, la référence franc¸aise de cet article, mais celle de l’article original paru dans Orthopaedics &Traumatology: Surgery & Research, en utilisant le DOI ci-dessus.
Fig. 1. Cases when Pearson coefficient fails to detect non reproducibility.
simple kappa has its own limitation (Table 1) [3,4,8–10]. Two important weaknesses of k value to assess agreement of a qualitative variable are as follow: it depends upon the prevalence in each category which means it is possible to have different kappa value having the same percentage for both concordant and discordant cells! Table 1 shows that in both (a) and (b) situations the prevalence of concordant cells are 80% and discordant cells are 20%, however, we get different kappa value (0.38 as fair and 0.60 as moderate - good) respectively. Kappa value also depends upon the number of categories which means the higher the categories, the lower the kappa value.[2–8]. Therefore, reporting weighted kappa can be highly recommended. [3,4,8–10]. As the authors pointed out in their conclusion, the HKA, alpha, and beta angles were reproducible for digital radiographs and showed good agreement with CT measurements. Such conclusion may be a misleading message due to inappropriate use of statistical tests. In conclusion, for reliability analysis, appropriate tests as well as correct interpretation should be applied. Otherwise, misdiagnosis and mismanagement of the patients cannot be avoided.