This retrospective study included 32 patients diagnosed with DA who underwent brace treatment between January 2015 and January 2023. Supplementary Table S1 provides demographic information about the patients. All patients exhibited flexion contractures at multiple finger joints, with amyoplasia and other primary neurological or muscular disorders ruled out through history taking and physical examination based on published classification (10–12). They subsequently underwent progressive extension brace treatment and were followed up for over 2 years. Informed consent was obtained from all parents/guardians of the patients included in this study. Ethical approval for this study was granted by the ethics committee of the Shanghai Ninth People's Hospital, affiliated to the Shanghai Jiaotong University School of Medicine.

We propose a clinical strategy for correcting DA using a progressive extension brace. The brace employs the method of static progressive stretching with low strength over a long time, whereby soft tissues elongate with stress relaxation and creep, transitioning from elastic deformation to plastic deformation. The use of the brace follows three principles: progressive extension to rectify camptodactyly, maintaining an open web space to straighten the clasped thumb, and continuous application throughout development. Patients with DA can commence braces from infancy, starting at around 1-month-old. It is recommended that children wear the braces during both night-time and daytime sleep for 8–12 h per day, whereas they engage in joint activities and hand function training during the remaining time. Continuous wear and regular follow-up visits facilitate ongoing adjustments of the brace, which transitions from a flexed to an extended position and eventually to an overextended position (Figure 1). Each phase is maintained for 2–3 months after achieving the desired adjustment; afterward, the brace is maintained throughout the hand developmental period (up to age 12).

To assess the clinical effects of early intervention on the correction of these hand deformities, we categorized the patients into four groups based on the age at treatment: 0–1 year (n = 11), 1–3 years (n = 9), 3–7 years (n = 7), and above 7 years (n = 5). The total active movement (TAM) of metacarpophalangeal joints (MPJ) and PIPJ and the extensor lag of PIPJ of the affected fingers were recorded using a goniometer to evaluate camptodactyly. The thumb-to-index finger metacarpal angle (M1M2 angle) and the degree of deviation at the first MPJ (M1P1 angle) were measured with the first web space open to assess the clasped thumb (13). The PedsQL 4.0 Generic Core Scales were used to assess the quality of life patients. Parental satisfaction with brace correction was evaluated using the FACE questionnaire (14). Results were expressed as mean ± SD. Between-group comparisons were conducted using unpaired t-tests, and a p-value < 0.05 was considered statistically significant (*p < 0.05, **p < 0.01, and ***p < 0.001). All statistical analyses were performed with GraphPad Prism 9 software.

Thirty-two DA patients underwent progressive extension brace treatment with an average follow-up of 4.8 years (4.8 ± 1.2 years). Patient compliance was very good, with no occurrence of skin breakdown or related complications. We found that the most favorable outcomes in progressive extension brace correction were observed in infants (under 1 year), who achieved an average TAM of up to 152° after correction. Toddlers (1–3 years old) with DA also demonstrated significant improvement, reaching an average TAM of 126°. They are rated as excellent and good according to the Strickland criteria. Patients aged 3–7 years old and above 7 years old achieved average TAM scores of only 83° and 72°, respectively, rated as poor based on the Strickland criteria (Figure 2A, Supplementary Table S2). These findings reveal superior brace treatment outcomes in DA patients when initiated during infancy or early childhood and underscore the imperative for early intervention.

By comparing the changes in the extensor lag of infants and toddlers with DA (I&T group) before and after brace correction, we observed a decrease from an average of 46° to 6° after treatment, demonstrating effective rectification of camptodactyly (Figure 2B).

The clinical presentation of a clasped thumb primarily involves a narrowed first web space. A smaller M1M2 angle and a larger M1P1 angle correspond to a more severely clasped thumb. In the I&T group, 10 cases exhibited pronounced clasped thumbs. Brace correction significantly reduced the M1P1 angle (decreased from an average of 43° to 5°) and increased the M1M2 angle (increased from an average of 38° to 65°), demonstrating effective correction of the clasped thumb (Figures 2C,D) in the I&T group.

In addition, DA patients achieved average PedsQL scores of 94.7 (parent-reported) and 89.3 (child-reported) after brace correction. Specifically, the I&T group attained average scores of 95.7 (parent-reported) and 90.2 (child-reported) after receiving brace intervention, indicating a quality of life close to that of normal children (Supplementary Table S3). Among all the parents, 24 expressed high satisfaction with the treatment for their children, 5 reported moderate satisfaction, and 3 expressed a fair outcome (Supplementary Table S3).

A female DA patient, 2 months old with a cleft palate, presented a clasped thumb and severe camptodactyly with the extensor lag exceeding 90° in multiple fingers (Figure 3A). A remarkable reduction in the extensor lag was observed after just 1 month of progressive extension brace correction (Figure 3B), and the brace use was continued to prevent subsequent contracture recurrence. Partial deformities in the PIP joints appeared in the patient after 5 years of treatment due to rapid finger growth and development (Figure 3C). However, thanks to the correction of joint contractures by the brace, we only needed to perform the double-opposing Z-plasty with a Y to V advancement on the little finger and Z-plasty on other fingers to complete the surgical correction without the need for additional skin grafting on the palm (Figure 3D, Supplementary Figure S1). At the 3-month postoperative follow-up, remarkable improvement in the patient's left fingers was observed (Figure 3E).

In a DA patient with a clasped thumb and ulnar deviation deformities (Figure 4A), the correction of camptodactyly was noticed after 10 months of brace treatment, although some degree of thumb adduction and ulnar deviation persisted (Figure 4B). Subsequently, after 30 months of continuous brace use, significant improvements were observed in finger flexion and extension function, the first web space dimensions, and ulnar deviation. Both hands achieved nearly normal function without the need for surgical intervention (Figure 4C). Another toddler with distal arthrogryposis in both hands also exhibited favorable corrective outcomes after progressive extension brace treatment (Figure 5).