Children with congenital vertical talus (CVT) have been treated with extensive soft-tissue releases, with a high rate of complications. Recently, reverse Ponseti-type casting followed by percutaneous reduction and fixation has been described, with excellent results in separate cohorts of children with CVT, of either idiopathic or teratological aetiology. There are currently no studies that compare the outcome in these two types. We present a prospective cohort of 13 children (21 feet) with CVT of both idiopathic and teratological aetiology, in which this technique has been used. Clinical, radiological and parent-reported outcomes were obtained at a mean follow-up of 36 months (8 to 57). Six children (nine feet) had associated neuromuscular conditions or syndromes; the condition was idiopathic in seven children (12 feet).

Initial correction was achieved in all children, with significant improvement in all radiological parameters. Recurrence was seen in ten feet. Modification of the technique to include limited capsulotomy at the initial operation may reduce the risk of recurrence.

The reverse Ponseti-type technique is effective in the initial correction of CVT of both idiopathic and teratological aetiology. Recurrence is a problem in both these groups, with higher rates than first reported in the original paper. However, these rates are less than those reported after open surgical release.

Cite this article: Bone Joint J 2014;96-B:274–8.

Background

Congenital vertical talus (CVT) is a rare deformity of the foot. It has been historically treated with extensive soft tissue releases with significant associated complications. Recently, reverse Ponseti-type casting followed by minimally invasive or percutaneous reduction and fixation has been described with excellent results in separate cohorts of either idiopathic or teratologic cases of CVT. There are currently no studies that compare the outcomes between the two types.

Ventral screw osteosynthesis is a common surgical method for treating fractures of the odontoid peg, but there is still no consensus about the number and diameter of the screws to be used. The purpose of this study was to develop a more accurate measurement technique for the morphometry of the odontoid peg (dens axis) and to provide a recommendation for ventral screw osteosynthesis.

Images of the cervical spine of 44 Caucasian patients, taken with a 64-line CT scanner, were evaluated using the measuring software MIMICS. All measurements were performed by two independent observers. Intraclass correlation coefficients were used to measure inter-rater variability.

The mean length of the odontoid peg was 39.76 mm (sd 2.68). The mean screw entry angle α was 59.45° (sd 3.45). The mean angle between the screw and the ventral border of C2 was 13.18° (sd 2.70), the maximum possible mean converging angle of two screws was 20.35° (sd 3.24). The measurements were obtained at the level of 66% of the total odontoid peg length and showed mean values of 8.36 mm (sd 0.84) for the inner diameter in the sagittal plane and 7.35 mm (sd 0.97) in the coronal plane. The mean outer diameter of the odontoid peg was 12.88 mm (sd 0.91) in the sagittal plane and 11.77 mm (sd 1.09) in the coronal plane. The results measured at the level of 90% of the total odontoid peg length were a mean of 6.12 mm (sd 1.14) for the sagittal inner diameter and 5.50 mm (sd 1.05) for the coronal inner diameter. The mean outer diameter of the odontoid peg was 11.10 mm (sd 1.0) in the sagittal plane and 10.00 mm (sd 1.07) in the coronal plane. In order to calculate the necessary screw length using 3.5 mm cannulated screws, 1.5 mm should be added to the measured odontoid peg length when anatomical reduction seems possible.

The cross-section of the odontoid peg is not circular but slightly elliptical, with a 10% greater diameter in the sagittal plane. In the majority of cases (70.5%) the odontoid peg offers enough room for two 3.5 mm cannulated cortical screws.

Cite this article: Bone Joint J 2013;95-B:536–42.