Occult deep vein thrombosis in lower limb trauma requiring microsurgical reconstruction-A retrospective cohort study.

BACKGROUND: Delayed microsurgical reconstruction of lower extremity trauma is associated with increased risk of free flap loss, frequently following failure of the venous anastomosis. This has been attributed to thrombocytosis, but occult deep vein thrombosis (DVT) may contribute to this risk. METHODS: We performed a retrospective cohort study of consecutive patients presenting to our service with lower limb injuries requiring microsurgical reconstruction between 2013 and 2017, and examined venous Duplex ultrasound reports, operation notes and free flap outcomes. RESULTS: A total of 165 free flap reconstructions for lower limb trauma were performed for 162 limbs in 158 patients. Seventy-two limbs (44.4%) underwent preoperative venous Duplex ultrasound identifying occult DVT in 14 (19.4%) patients. Occult DVT was identified intraoperatively in a further 7 cases. Bilateral lower limb injuries (p = 0.0002), the level of injury at or above the knee (p < 0.0001), multiple levels of injury within the affected limb (p = 0.0008) and critical care admission (p = 0.0008) were significant risk factors for DVT. All 7 cases of DVT diagnosed intraoperatively prompted a change in the surgical plan for the recipient vein; however, preoperative identification of occult DVT also lead to an adjustment in the microsurgical plan in 4 out of 14 cases. CONCLUSIONS: Prevalence of DVT is high in severe lower limb injury, potentially increasing the risk of free flap loss. Preoperative identification of occult DVT may influence the microsurgical plan and mitigate for this risk.

Developmental mechanisms underlying polydactyly in the mouse mutant Doublefoot.

The pre-axial polydactylous mouse mutant Doublefoot has 6-9 digits per limb but lacks anteroposterior polarity (there is no biphalangeal digit 1). It differs from other polydactylous mutants in showing normal Shh expression, but polarizing activity (shown by mouse-chick grafting experiments) and hedgehog signalling activity (shown by expression of Ptc1) are present throughout the distal mesenchyme. The Dbf mutation has not yet been identified. Here we review current understanding of this mutant, and briefly report new results indicating (1) that limb bud expansion is concomitant with ectopic lhh expression and with extension of the posterior high cell proliferation rate into the anterior region, and (2) that the Dbf mutation is epistatic to Shh in the limb.