Prophylactic pinning of the contralateral hip in the treatment of slipped upper femoral epiphysis has been shown to be safer than continued observation of the contralateral hip. This treatment remains controversial due to the potential for harm caused to an apparently unaffected hip. There is evidence that pinning of an already slipped epiphysis causes growth disturbance of the proximal femur, however Hagglund showed that there is not necessarily growth arrest at the physis after pinning, as the slip occurs at the hypertrophic layer of the growth plate with no damage to the germative layer. This was confirmed by Guzzanti who confirmed that a single screw provided epiphyseal stability and preserved potential for growth. We conducted a pilot study to determine whether prophylactic pinning affects subsequent growth of the unaffected hip. In order to determine the effect of prophylactic pinning we compared radiographs skeletally mature patients who had either undergone the procedure (group 1), not undergone the procedure but had pinning of the affected side (group 2), and adults with no history of SUFE (group 3). We measured the articulo-trochanteric distance and calculated the ratio of the trochanteric-trochanteric distance to articulo-trochanteric distance. These measures have been used in previous studies and shown to be reliable indicators of disturbed proximal femoral growth. As this was a pilot study we recruited 8 to each group. The absolute sum of the ATDs were 219mm (average 27.3mm) Group 1, 213mm (average 26.6mm) Group2 and 258mm (average 32.5mm). The average trochanter-trochanter:
