To determine if there is a safe osseous corridor for trans-sacroiliac screw fixation of U-type sacral fractures using fluoroscopic landmarks.

We reviewed the sacral anatomy of patients who underwent Computed Tomography (CT) investigations between October and December 2009. Agfa-IPMAX Version 5.2 software was used to determine if there was a trans-sacroiliac osseous corridor in the S1 and S2 vertebrae from one ilium to the other.

76 patients were in the study, 38 male and 38 female. Exclusion criteria were patients under 18 years old; patients with degenerate lumbar spine and lumbo-sacral junction; CT imaging slices greater than 2.5mm.

We measured various parameters including the dimensions of the S1 and S2 mid-sagittal vertebral body; cross-sectional areas of the S1 and S2 corridor; location of the centre of the S1 and S2 corridor.

The mean cross-sectional area for S1 and S2 corridors in males and females are 21mm² and 15mm² respectively. The mean cross-sectional area for the S2 corridor in males and females were 15mm² and 11mm² respectively. The centre of the S1 and S2 corridor is located in the centre of both S1 and S2 vertebrae.

Two-thirds of males and females have a complete osseous corridor to pass a trans-sacroiliac S1 screw. The S2 corridor was present in all males but only in 87% of females. Before placement of trans-sacroiliac screws, the surgeon should review the CT sacral anatomy to determine if the trans-sacroiliac osseous corridor is present.

Ethics Approval: None – Audit Interest Statement: None

Hind foot arthrodesis through traditional lateral approach in patient with severe valgus deformity carries a significant risk of wound breakdowns, infection and the risk of sural nerve damage. It is also difficult to fully correct a severe valgus deformity through the lateral approach. To overcome some these problems a medial approach has been recommended. Few authors have reported good results in a small series of cases.

We present a retrospective review of 18 consecutive patients with valgus hind foot deformity who underwent hind foot arthrodesis via a medial approach. There were 10 male and 8 female with an average age of 55 years (range 28–75years). The indications included osteoarthritis in 13; post traumatic OA in 3 and rheumatoid arthritis in 2. The mean pre-op subtalar valgus angle was 32o (range 12 – 49) and mean post op valgus angle was 17 (range 10 – 25). All the wounds healed primarily and there were no incidence of wound breakdown or infection. None of the patients developed neuro-vascular complications. The average time for fusion was 5.6 months (range 3–9). Two patients needed further surgical intervention, one for FHL tethering at the fusion site and one for non-union of subtalar joint in a chronic smoker.

The medial approach not only allows a safe and fantastic access to subtalar joint making correction of valgus deformity easier but is also extendable to include talo- navicular and naviculo-cunieform fusion and FDL transfer as additional procedures through the same approach as and when indicated

In conclusion we recommend the medial approach for performing subtalar arthrodesis in valgus hind foot deformities