I．Introduction

In Japan, cerebral palsy (CP) is defined as “a permanent but changeable motor and postural abnormality based on non-progressive lesions of the brain occurring between conception and the neonatal period (within 4 weeks of birth) ^［1］. Symptoms develop by the age of two years. CP excludes progressive disease, transient movement disorders, or delayed motor development that is likely to normalize in the future. In CP patients, abnormal posture due to muscle hypertonia (spasticity and rigidity) causes motor paralysis and impairs motor development^［2］. Patients are classified using the Gross Motor Function Classification System (GMFCS) ^［3］which classifies their motor abilities from Level I, in which they can walk independently, to Level V, in which they are unable to move on their own.

An ankle-foot orthosis (AFO) is commonly used for CP. With respect to equinus gait, orthoses that limit plantar flexion improve gait^［4］, improve gait speed by 9%^［5］, and reduce oxygen consumption during walking ^［5-8］. Both the double bar ankle-foot orthosis and the shoe-horn brace exhibit enhanced gait performance when compared to walking barefoot. While there is no specific orthosis as better than the others, there exist subtle variances in characteristics depending on the type of orthosis employed^［9］. However, the precise nature of adaptation remains unclear. During daily life and training to use them, the orthoses often require repair. The purpose of this study is to investigate the causes for repair of AFOs in children with CP.

II．Material and methods

Participants

The subjects were 332 CP patients under the age of 18 (1-17 years old, mean 8.6 years old) who visited the brace clinic of our hospital regarding an ankle-foot orthosis (AFO) from November 2021 to June 2022. There were 32 patients available for repair, involving 43 AFOs. Among them, excluding multiple repairs for the same reason and orthoses created by other medical institutions, a total of 29 patients with 36 AFOs were analyzed. We decided on AFO as the data collection unit.

Indications for AFO in our hospital are decided based on published textbook^［10］. If heel-ground contact is not possible and the deformity is severe, a double bar ankle-foot orthosis (double bar AFO) is indicated. If heel-ground contact is possible and the deformity is not too severe, a shoe-horn brace (SHB) is indicated. SHB is prescribed if the deformity can be corrected with SHB, and double bar AFO if not. Figure 1 shows the types of AFO repairs in our hospital. In the case of hindfoot varus when loaded, the belt is pulled from lateral to medial. In the case of hindfoot valgus when loaded, the belt is pulled from medial to lateral and a medial arch support is attached. When the deformation is strong, four belts are used instead of the usual three.

Data collection and analysis

Age at the time of outpatient consultation, sex, Gross Motor Function Classification System (GMFCS) level, type of orthosis repaired, the ratio of repair and fabrication for double bar AFO and SHB, length of time from orthosis completion to repair, and the cause of the needed repair were examined. The period from completion of the brace to repair was classified as within 3 months, between 3 months and 1 year, and after 1 year. Causes of repair were categorized into rubbing on the medial side of the foot, rubbing on the lateral side of the foot, rubbing on both sides of the foot, rubbing on other parts of the foot, growth, wear and parts deterioration, and fitting failure. We also investigated the relationship between time to repair and cause of repair. Regarding rubbing on the medial side of the foot and rubbing on the lateral side of the foot, we investigated the direction of deformation in the patient’s unloaded and loaded conditions.

Statistical analysis

Sex and the ratio of repair and fabrication for double bar AFO and SHB were compared. Between group differences were tested using the chi-squared test with p < 0.05 set as the threshold for significance.

III．Results

Twenty-nine AFOs were repaired. The mean period from fabrication of the AFO to repair was 9.9 months (0-43 months).

There was no difference in age between repair patients and fabrication patients (Table 1). Repair patients were more likely to be male than fabrication patients, but the difference was not significant (p = 0.101) (Table 1). The GMFCS level in repair patients (mean 2.8) was non-significantly (p = 0.15) better than in fabrication patients (mean 3.1) (Table 1).

Eight double bar AFOs and 28 SHBs were repaired. Sixty-eight double bar AFOs and 125 SHBs were fabricated. There was no significant difference in the percentage of repairs and fabrications between SLB and SHB (p = 0.128) (Table 1).

Nine AFOs required repair within 3 months, 17 AFOs between 3 months and 1 year, and 10 AFOs after 1 year.

Growth response was the primary cause for repair after one year. Fitting failure was the primary cause for repair within the first 3 months (Table 2). All patients with rubbing on the medial side of the foot were hindfoot vulgus, and all patients with rubbing on the lateral side of the foot were hindfoot varus in the patient’s loaded conditions.

IV．Discussion

In a 2019 systematic review, AFO for CP was recommended as “PROBABLY DO IT” for its motor function^［11］. In this research, the participants were younger than 18 years old. Beyond the age of 18, growth ceases, thereby minimizing issues associated with orthosis-related factors like growth and alterations in gait patterns resulting from motor development. Furthermore, it is worth noting that the provision of orthotic services in Japan has undergone modifications for individuals aged 18 and above, leading to a decrease in hospital visits for orthotic purposes. There was no difference in age between repair and fabrication patients. GMFCS level tended to be better in repair patients, although there was no significant difference between groups. Patients with greater mobility to stand and walk with AFOs may require more AFO repairs. Unes et al. reported that AFO-wearing time depends on activity and participation levels rather than body functions and structures in children with spastic CP^［12］.

Murayama and Mizuma reported that 59.2% of prosthetists’ jobs are related to AFO^［13］. Sato et al. reported that repair of AFOs in adults often involves foot modification and adjustment during the recovery period and repair and correction perpendicularly during the maintenance period^［14］. However, there are no reports on the repair of AFOs in CP patients as far as we could determine.

In CP children, spasticity may cause changes in foot varus/valgus opposition between non-loading and loading^［2］, consistent with the data in this study. Saisu described that contracture of the triceps surae usually results in difficulty in, or absence of, dorsiflexion and the foot being equinus, but some affected children try to compensate by externalizing the subtalar joint, which allows the forefoot to move upward^［15］. Kuya et al. reported that an indication for AFO is a collaborative, iterative, and individualized process^［16］. In children with CP, the varus and valgus of the hindfoot may change between non-loading and loading due to spasticity, so it is important to evaluate the loading position when making the orthosis. It is important to explain to parents the possibility that an orthosis may rub on the foot, which can only be known after the orthosis is used.

The double bar AFO is rigid, constrains varus/valgus and twisting, has a strong binding force^［10］, and is heavy. SHBs have low stiffness and strength, are flexible ^［10］and light. Although not included in the current study, there are cases in which the equinus foot is strong and the double bar AFO is indicated, but the parents may want SHB because of the weight and appearance. Caregivers of CP patients believe that although AFOs can benefit mobility and independence, AFO provision is a confusing and lengthy process, and that the AFOs themselves are uncomfortable and difficult to use. They would like more information during the AFO provision process^［17］. Morris et al. reported that there was considerable variation in the types of orthoses prescribed between districts, and particularly for AFO^［18］. Careful consideration of the indications for orthosis is important. In our hospital, before creating an AFO, the patient tried wearing the AFO during rehabilitation by a therapist, and the patient’s acceptance was evaluated.

Our study has several limitations. First, we did not conduct a detailed investigation of the wearing time and conditions of the AFO. Second, we have not been able to examine what kind of patients needed repair, such as the type of CP they had. Third, the AFO orthotist was not the same. Fourth, though greater weight has detrimental effects on the gait pattern in CP^［19］, height and weight were not examined.

In conclusion, we investigated 36 AFOs repaired in CP patients. Repair patients were more likely to be male than fabrication patients. GMFCS levels tended to be higher in patients with AFO repair. Fitting failure was most common within 3 months, and growth response was the most common cause for repair after 1 year. It is important to follow up after completion of the orthosis.

Contributors

TK and HT contributed to project development, data collection, and manuscript writing. MS contributed to data collection. NK contributed as the scientific guarantor of this manuscript. All authors read and approved the final manuscript.

Financial support

No specific funding was used for this study.

Conflict of interest

The authors have no conflicts of interest.

Ethical approval

The study protocol was approved by the ethics review committee of Chiba Rehabilitation Center on July, 2022. The participants were informed by opt out. This is not animal research.

Data availability

All data generated or analyzed during this study are included in this published article.

Acknowledgements

We thank prosthetist Atsushi Urata for data collection and prosthetist Akira Matsumoto for repair of ankle-foot orthoses.