The skeletal elements in the area of the distal extremity systems are already separated from each other in the 8th week of intrauterine fetal development. If this separation process in the area of joints remains incomplete, this consecutively leads to the formation of coalitions, which in many cases occur on both extremity sides, right and left. These coalitions are initially fibrous and somehow mobile, later cartilage-like and can continue to ossify to the formation of an incomplete or complete bony bridge. These fibrous, cartilaginous or bony bridges affect the usual free mobility of the tarsal bones which are functioning like a precise clockwork, thus causing foot pain due to overuse and sheer forces in the tarsal bones.
Coalitions are among the most common diseases of the child’s foot in need of surgical treatment. Their occurrence is indicated with a prevalence of about 1% (compared to idiopathic clubfoot 0.1-0.2%). However, many cases remain asymptomatic and are not diagnosed or diagnosed late.
It is not uncommon for real or supposed foot trauma to be the onset of clinical symptoms. In some cases spontaneous improvement of acute complaints is possible, so conservative treatment options are appropriate in some cases, while a surgical procedure must be considered for persistent complaints.
This is a very common form of the tarsal coalition. Usually in between the navicular and the calcaneal bone there is a ligament ( ligamentum bifurcatum). In a coalition this ligament is transformed into a fibrous, and at the age of about 8 to 12 years of life increasingly bony bridge. This causes reduced and inhibited tarsal mobility with limitation in particular of inversion and eversion which then often leads to stress pain. Also peroneal spasms and overuse pathologies in the Talonavicular joint are seen.
As a diagnosis apart from the restricted inversion and eversion mobility a simple X-ray usually shows already the problem. A MRI can confirm fibrous pathologies which sometimes can make diagnostic problems.
Therapeutically early resection, independent of the extent of the symptoms, is recommended. The prognosis is particularly favorable with early surgery.
The second more important form of tarsal coalitions is found in the medial area of the ankle joint, most often involving the medial, middle facet of the talocalcaneal joint. The expansion of the initially fibrous, later increasingly ossified bridge formation can include very different parts of the lower ankle. Pain often occurs between the ages of about 12 to 16 years in the area of the coalition, but often also at the lateral side of the foot due to decreased mobility in the sinus-tarsi area as typical anterolateral subtalar impingement.
Besides the clinical symptoms of reduced mobility and pain the typical signs of talar head ossifications and C-sign in the X-ray can lead to the diagnosis. In these cases a MRI or CT scan is recommended to help the surgeon planning the treatment.
The indication of the surgical treatment is particularly difficult in the talocalcaneal coalition in childhood and adolescens. A resection here does not necessarily guarantee a painfree situation but an early treatment usually has a higher success rate after surgical treatment. There are some other important factors involved in the decision finding of the most successful treatment as e.g. muscular contracture status and presented foot deformities.
The postoperative follow up can be extremely lengthy with months of residual complaints. This is due to the fact that the joints have been in certain situations and alignments for many years and the resection of the coalition only creates the basis for the restoration of a certain partial mobility. In a certain percentage a secondary correction of the position of the foot or complete arthrodesis of the joint might be needed. Here especially in the talocalcaneal coalitions a secondary arthrodesis might in case be a reasonable solution for an otherwise secondary painfree situation.
The results of resection deteriorate with advancing age at the time of the procedure.