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. 2023 May 17;12(10):3509.
doi: 10.3390/jcm12103509.

The Controversial Definition of Normal Toe Alignment

Philipp Schippers  1 , Philipp Drees  1 , Erol Gercek  1 , Felix Wunderlich  1 , Daniel Müller  2 , Christian Ruckes  3 , Alexander Meyer  4 , Stefan Klein  5 , Sebastian Fischer  6
Affiliations

The Controversial Definition of Normal Toe Alignment

Philipp Schippers et al. J Clin Med. .

Abstract

"Normal" and "abnormal" are frequently used in surgical planning and to evaluate surgical results of the forefoot. However, there is no objectifiable value of metatarsophalangeal angles (MTPAs) 2-5 in the dorsoplantar (DP) view with which to objectively evaluate lesser toe alignment. We aimed to determine which angles are considered to be "normal" by orthopedic surgeons and radiologists. Thirty anonymized radiographs of feet were submitted twice in randomized order to determine the respective MTPAs 2-5. After six weeks, the anonymized radiographs and photographs of the same feet without apparent affiliation were presented again. The terms "normal," "borderline normal," and "abnormal" were assigned by the observers. Viewers considered MTP-2 alignment from 0° to -20° to be normal, and below -30° abnormal; MTP-3, 0° to -15° to be normal and below -30° abnormal; MTP-4, 0° to -10° normal and below -20° abnormal. Between 5° valgus and 15° varus was the range of MTP-5 recognized as normal. High intra-observer but low interobserver reliability with overall low correlation of clinical and radiographic aspects was observed. The assessment of the terms "normal" or "abnormal" are subject to a high degree of variation. Therefore, these terms should be used cautiously.

Keywords: forefoot; metatarsophalangeal angle; parabola; toe alignment; transverse plane.

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Conflict of interest statement

Philipp Schippers, Invented and created the used software, Tyche. No funding or other financial benefit was given. All further authors declare no conflict of interest.

Figures

Figure 1
Figure 1
Experimental Setup.
Figure 2
Figure 2
Web-based online analysis tool Tyche™. (a) Assessment of clinical images, (b) assessment of radiographic images.
Figure 3
Figure 3
Study flow chart.
Figure 4
Figure 4
Six experts measured MTP–angles two (a), three (b), four (c) and five (d) on thirty dorsoplantar (DP) radiographs. Results were plotted on the X–axis. In addition, they graded the MTP–alignment, based on their personal opinion, into three grades: “normal”, “borderline normal” and “abnormal”. An ordinal scale was created giving “normal” the number 1, “borderline normal” the number 2 and “abnormal” the number 3. A mean value with SD was calculated between the six experts for every MTP joint and plotted on the Y–axis. This can be considered the “mean assessment” between the six experts. SD, standard deviation.
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