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D. Bai1,2, H. Kurokawa3, M. Shirotani1, M. Takigawa1, C. Nozawa1, P. Mahakknaukrauh4, M. Tokuda1,5, Y. Tanaka3,2
1Heisei Memorial Hospital, Rehabilitation, Nara, Japan, 2Nara Medical University, Graduate School of Medicine, Musculoskeletal Reconstructive Surgery, Nara, Japan, 3Nara Medical Univeristy, Orthopedic Surgery, Nara, Japan, 4Chiang Mai University, Anatomy and Faculty of Medicine, Chiang Mai, Thailand, 5Kio University, Graduate School of Health Sciences, Nara, Japan
Background: The flexor hallucis longus (FHL) and flexor digitorum longus (FDL) tendons are frequently used in foot and ankle surgery, such as tendon transfers and cross-connections. The knowledge of tendon interconnections is essential for surgeons to minimize postoperative functional loss and to understand the underlying causes of loss of toe functions. Therefore, a less invasive or non-invasive method is necessary for the preoperative evaluation of chiasma plantare formation to perform optimal surgeries and provide appropriate physiotherapy. The development of ultrasonography (US) may help chiasma plantare formation evaluation in patients with foot and ankle disorders.
Purpose: Our purpose was to demonstrate the usefulness of the US method using cadavers and healthy subjects.
Methods: We describe a two-part study. In the first part of the study, 11 cases (22 ankles, mean age; 70.0±9.4 years) were obtained from adult Asian cadavers and fixed in 10% formalin solution before examination. All of them had no experiences of lower leg problems according to their clinical records. First, we evaluated chiasma plantare formation using US. Later, this was evaluated using the findings of dissection. Then, we compared the results of US and those of dissection. In the second part of the study, 50 healthy young subjects (100 feet, mean age; 27.1±5.3 years) participated in this study. We evaluated chiasma plantare formation using US. For both parts of the study, the FHL and FDL were evaluated at locations approximately 40% proximal from the lateral malleolus to the fibular head using US. Moreover, we classified chiasma plantare formation, according to a previous report, as follows: type A, connection from the FHL to the FDL of the second toe; type B, connection from the FHL to the second and third toes; type C, connection from the FHL to the second, third, and fourth toes; or type D, connection from the FHL to all lesser toes.
Results: As for the first part of the study, using US, chiasma plantare formation was classified as types A and B in 15 and 7 ankles, respectively. Types C and D were not observed. Regarding the findings of dissection, chiasma plantare formation was classified as types A, B, and C in 14, 6, and 2 ankles, respectively. Therefore, the results of chiasma plantare formation using US were correctly matched in 19 of 22 ankles (86%) to those using the findings of dissection. Furthermore, there was an 86% similarity between the two methods, suggesting that US can be used with reasonable accuracy. And, in the second part, type A was observed in 15 subjects (30%), type B in 32 subjects (64%), type C in 3 subjects (6%), and type D in 0 subjects (0%). As a result, chiasma plantare formation was observed in all ankles (cadavers and healthy subjects).
Conclusion(s): Chiasma plantare formation can be reliably and noninvasively evaluated using US. We can also evaluate healthy individuals. Therefore, we could prove the reliability of US evaluation.
Implications: Our results suggest that chiasma plantare formation can be reliably and noninvasively evaluated using ultrasonography.
Funding, acknowledgements: No funding was received for this study.
Keywords: Ultrasonography, Chiasma plantare, cadaver study
Topic: Orthopaedics
Did this work require ethics approval? Yes
Institution: Nara Medical University
Committee: Nara Medical University and Chiang Mai University
Ethics number: ANA-2562-06064
All authors, affiliations and abstracts have been published as submitted.
