Hip fractures remain one of the most serious injuries that occur in older people [1–3], with a mortality rate of 10% at one month, 20% at four months and 30% at one year . Many of those who recover suffer a loss in mobility and independence. Approximately half of patients who were previously functionally independent become partly dependent, while one third become totally dependent . The mean age of these patients is 81 years, 75% are female, and they are one the frailest groups of patients to be admitted to hospital, commonly with multiple co-morbidities. Hip fractures are painful , in both the pre and postoperative period. Adequate treatment of pain is not only a humanitarian issue, but may also impact on recovery. Pain is associated with increased neuro-hormonal stress response, myocardial ischemia, and delayed mobilization, all of which may increase postoperative length of stay and are associated with increased postoperative mortality. Untreated pain is also associated with delirium [7, 8]. Current methods of providing analgesia include: paracetamol, non-steroidal anti-inflammatory drugs (NSAIDS), oral or parenteral opioids, and regional anaesthesia techniques. Paracetamol is an effective and safe analgesic , but insufficient for a significant number of patients when used alone. NSAIDs are largely contraindicated in this patient group due to their nephrotoxicity, and gastrointestinal side effects. They may also increase operative blood loss.
Opioids provide reasonable analgesia at rest but are relatively ineffective for dynamic pain (pain on movement). This is an issue postoperatively as patients often feel comfortable at rest but complain of moderate to severe pain during physiotherapy and ambulation. Opioid-related side effects are very common, distressing, and potentially serious. Nausea, vomiting, constipation, and delayed gastric emptying are common. Less common but more serious side effects include, delirium, respiratory depression, and death. Regional anaesthesia offers an attractive alternative to systemic opioids both for pre and postoperative use. Evidence from elective lower limb arthroplasty suggests that postoperative nerve block analgesia is beneficial overall  and may even enhance early mobilization, assuaging concern that impairment of motor function leads to a delay in ambulation . However, to date, trials have been inconclusive regarding the benefit in acute hip fracture patients [12, 13].
Several factors may explain this. Firstly, the historical success rate of regional anaesthetic techniques appears to have been relatively low. A non-randomized study of fascia iliaca block by Emergency Department physicians found adequate block at 1 hour in only 30% of subjects, although improvements in outcome (length of stay) were favorable in those with a successful block . Use of ultrasound would be expected to improve the success rate of regional techniques and evidence does support this . A recent trial comparing ultrasound-guided femoral nerve block to parenteral opioids in an Emergency Department setting in exactly this patient group demonstrated significantly reduced pain scores and decreased the need for rescue analgesia .
Another reason for the conflicting evidence is that most studies have provided a single injection nerve block either on admission or in the immediate perioperative period. Given that the pain experienced following hip fracture persists for several days, single injection nerve blocks may be inadequate as they only provide analgesia for up to 24 hours. There are two potential options to improve the duration of analgesia. Foss et al. reported the successful use of low dose continuous epidural analgesia. Unfortunately this is not thought to be feasible or optimal in the United Kingdom at present for this group of patients. Another option is to provide initial analgesia with a single shot nerve block followed by continuous perineural infusion of local anaesthetic. One study which used postoperative perineural catheter infusion failed to show benefit , however, catheters were only inserted postoperatively. We therefore propose to study the effects of early and continuous femoral nerve block analgesia on dynamic pain and early rehabilitation compared to standard analgesic care.