Purpose

Flat feet are an important cause of foot problems in children. The flexible flat foot is the most common form and is normally physiological and asymptomatic. Further assessment is necessary when a symptomatic flat foot persists. Surgical interventions are indicated when conservative therapies have failed. The Kalix arthroereisis is a surgical option and is placed in the subtalar joint of the foot, thereby preventing hyperpronation, and stabilizes the foot against excessive movements. The purpose of this study was to evaluate the functional and radiological outcomes of pediatric patients who had undergone a Kalix implantation for the treatment of a symptomatic flexible flat foot.

Dysplasia Epiphysealis Hemimelica (DEH) also known as Trevor's Disease is a rare developmental disorder resulting in cartilaginous overgrowth of the epiphysis of long bones. DEH is usually diagnosed in children between two and eight years old and it is three times more often diagnosed in boys. The most reported complaints are pain, limitation in range of motion, and deformity or swelling of the affected joint. Treatment of symptomatic lesions consists of surgical resection of the lesion, resulting in good long-term results.

Based on histological evaluation, DEH is often described as an osteochondroma or an osteochondroma-like lesion, although there are clinical, radiological and genetic differences between DEH and osteochondromas. To investigate the hypothesis that DEH and osteochondromas are histologically identical, two cases of DEH and two cases of osteochondromas in patients with Hereditary Multiple Osteochondroma (HMO) are compared at histological level.

Tissue samples from patients with a histopathologically confirmed diagnosis of DEH were compared with two age and gender matched patients diagnosed with HMO. After tissue sampling and processing, (immuno)histological stainings were performed for Collagen type II, Collagen type X, Sox-9 and Safranin-O.

Histologically, clumping of chondrocytes in a fibrillar matrix, a thick disorganized cartilage cap and ossification centres with small amounts of unresorbed cartilage were observed in DEH. In contrast, chondrocyte organisation in cartilage of osteochondromas displays characteristics of the normal growth plate. In addition, differences in expression of collagen type II, collagen type X and Sox9 were observed. Collagen type II was expressed in the extracellular matrix surrounding proliferative and hypertrophic chondrocytes in osteochondromas, while weak expression was observed in the entire cartilage cap in DEH. Collagen type X was not expressed in DEH, while expressed in the pericellular matrix surrounding hypertrophic chondrocytes in osteochondromas. Staining for Sox9 was positive in the hypertrophic chondrocytes in osteochondromas, while expressed in the nuclei of all chondrocyte clusters in DEH.

Both morphological and immunohistological differences were observed in histological sections of DEH and osteochondromas. These findings reject our hypothesis, and supports the earlier observed clinical, radiological and genetic differences and implies a different aetiology between DEH and osteochondroma formation in HMO.

Osteoarthritis of the first metatarsophalangeal (MTP1) joint is a common disorder in elderly, resulting in pain and disability. Arthrodesis of this joint shows satisfactory results, with relieve of pain in approximately 85% of the patients. However, the compensation mechanism for loss of motion in the MTP1 joint after MTP1 arthrodesis is unknown. A reduced compensation mechanism of the foot may explain the disappointing result of MTP1 arthrodesis in the remaining 15% of the patients. This study was conducted to elucidate this compensation mechanism. We hypothesize that the ankle and forefoot are responsible for compensation after MTP1 arthrodesis.

Gait was evaluated in eight patients with arthrodesis of the MTP1 joint (10 feet) and twelve healthy controls (21 feet) by using a sixteen-camera Vicon-system. The four-segmental, validated Oxford-Foot-Model was used to investigate differences in range of motion of the hindfoot-tibia, forefoot-hindfoot and hallux-forefoot segment during stance. For statistical analysis, the unpaired t-test with Bonferroni correction (p<0.0125) was performed.

No differences in spatiotemporal parameters were observed between both groups. In the frontal plane, MTP1 arthrodesis decreased the range of motion in midstance, while an increased range of motion was observed in terminal stance for the hindfoot relative to the tibia in the transversal plane. Subsequently range of motion in the forefoot in preswing was increased. This resulted in less eversion in the hindfoot during midstance, increased internal rotation of the hindfoot during terminal stance and more supination in the forefoot during preswing in the MTP1 arthrodesis group. Motion of the hallux was restricted in the loading response (i.e. plantar flexion) and terminal stance (i.e. dorsiflexion).

As hypothesized, both the ankle and the forefoot are responsible for compensation after MTP1 arthrodesis, because arthrodesis causes less eversion and increased internal rotation of the hindfoot and increased supination of the forefoot. As expected, both dorsiflexion and plantar flexion of the hallux was restricted due to arthrodesis. These findings suggest a gait pattern in which the lateral arch of the foot is more loaded and the stiff hallux is avoided during the stance phase of gait.

Our results indicate that proper motion of the forefoot and ankle joint is important when considering arthrodesis of the MTP1 joint. Therefore, we emphasize careful assessment the range of motion in the forefoot and ankle joint in the pre-operative situation, since patients with a decreased range of motion in the forefoot and ankle joint have a less functioning compensation mechanism. We currently perform a study to evaluate the strength of the positive correlation between the pre-operative range of motion in the forefoot and ankle joint and the clinical outcome.