Background: Toe-walking is a possible finding during gait assessment of autism spectrum disorder (ASD) subjects, and it can be also manifested during standing and running [1]. Three mutually exclusive clinical functional classes of tiptoe behavior (TTB) of increasing severity have been described: TTB during running (TTB1), during walking and running (TTB2), and during standing, walking and running (TTB3) [1]. Moreover, a positive relationship between the presence and severity of TTB and the Achilles tendon shortening (assessed as Soleus (SM) and Gastrocnemius (GM) muscle lengths) was reported [2]. To our knowledge, no studies describe SM and GM length values of ASD subjects without and with TTB at different age classes.
Objectives: This cross-sectional study aimed: 1) to describe the prevalence of TTB in a sample of individuals with ASD and at different age classes; 2) to describe SM and GM length values of ASD subjects with and without TTB in the general sample and at different age classes; 3) to compare SM and GM length values of ASD subjects without TTB (NO-TTB subgroup) versus ASD subjects with moderate-severe TTB (i.e., TTB2+TTB3 subgroup) in the sample and for each age class subgroups.

Methods: 106 subjects (mean age: 11.27±4.95yrs; range: 3.66–24.83yrs; 83 males) diagnosed with ASD according to DSM-5 or ICD-10 criteria were included.
The presence of TTB was evaluated by a physiotherapist through direct observation and a structured interview of the main caregiver [1]. The SM and GM length were assessed using a manual goniometer [2]. The sample was divided according four age classes: 0-6 yrs, 7-12 yrs, 13-18 yrs, and 19-24 yrs. Subjects belonging to TTB2 and TTB3 were considered as moderate-high TTB severity subjects. Thus, a comparison of GM and SM length values between NO-TTB and TTB2+TTB3 subgroups was performed.

Results: The prevalence of TTB subjects was 28.3% (n=30). Table 1 describes the TTB prevalence in the four age classes. Table 1 provides a detailed description of SM and GM length values of ASD subjects with and without TTB. Performing a Mann-Whitney tests we found that ASD subjects with moderate-severe TTB manifest statistically significant lower SM and GM length values than ASD subjects without TTB in the general sample and in age class subgroups (p<0.05) (Table 2).
TABLES here

Conclusion: ASD subjects who present moderate-high TTB severity manifest a significant decrease in Achilles’ tendon length values. Further research is required to confirm the results.

Notes:

1 Villa Santa Maria Foundation, Tavernerio (CO), Italy
2 School of Medicine and Surgery, University of Milano-Bicocca, Milano, Italy
3 School of Physical & Occupational Therapy, McGill University, Montreal, Canada
4 Istituto “La Casa del Sole”, Mantova, Italy
5 CTR di Fondazione Renato Piatti Onlus, Milano, Italy