The sentinel vein: an anatomical guide to localisation of the dorsomedial cutaneous nerve in hallux surgery.

Damage to the dorsomedial branch of the medial dorsal cutaneous nerve is not uncommon in surgery of the hallux. The resultant morbidity can be disabling. In the light of the senior author's operative observation of a sentinel vein, we undertook a cadaver study to investigate the anatomical relationships of the dorsomedial branch of the medial dorsal cutaneous nerve. This established that in 14 of 16 cadaver great toes exposed via a modified medial incision, there is an easily identified vein which runs transversely superficial and proximal to the nerve. In a prospective clinical study of 171 operations on the great toe using this approach, we confirmed this anatomical relationship in 142 procedures (83%), with no complaint of numbness or pain in the scar at follow-up. We attribute this to careful identification of the 'sentinel' vein and the subjacent sensory nerve, which had been successfully protected from damage. We recommend this technique when operating on the great toe.

On admission haemoglobin in patients with hip fracture.

Several authors have identified on admission haemoglobin level as the most useful predictor of transfusion risk in patients with a hip fracture. A low postoperative haemoglobin unexplained by perioperative blood loss is not uncommon in these patients. The drop in haemoglobin after re-hydration prior to surgery should depend not only on the degree of dehydration but also on the amount of blood lost in the fracture.We could find no study in the English literature estimating the magnitude of this fall in haemoglobin after re-hydration prior to surgery.We conducted a prospective study to estimate the magnitude of fall in haemoglobin after rehydration prior to surgery by repeating the full blood count after at least 12 h of preoperative fluid resuscitation in 127 patients with hip fracture (75 consecutive at one centre and 52 consecutive at another).The average preoperative drop in haemoglobin was 2.23 gram/decilitre (g/dL) (p-value = 0.00) in subtrochanteric fractures, 1.1 g/dL (p-value = 0.001) in intertrochanteric fractures and 0.7 g/dL (p-value = 0.02) in intracapsular fractures. Fifteen patients with a haemoglobin level >9 g/dL on admission were found to have a haemoglobin level <9 g/dL on repeat test and were prevented from going to theatre without arrangements for perioperative transfusion during this study. Their predicted average postoperative haemoglobin without perioperative blood transfusion was calculated to be 6.5 g/dL.The on admission haemoglobin level was found to be falsely reassuring and could lead to a very low postoperative haemoglobin level. This could prove to be dangerous for many patients especially if remains undetected for several hours. We recommend that all patients with subtrochanteric fractures,and all patients with intertrochanteric or intracapsular fractures with a haemoglobin of less than 12 g/dL on admission have a repeat haemoglobin level performed prior to their surgery.