PENG vs Femoral Block for Hip Fracture, A Pragmatic Cluster-Randomized Study

Each year, 250,000 adults in the US and 1.6 million worldwide suffer hip fractures. Peripheral nerve blocks, including femoral blocks, administered soon after admission to patients presenting with hip fractures have been shown to produce clinically and statistically significant reductions in pain scores, opioid consumption, the incidence of confusional state, and the time to mobilization.

Historically, lower extremity blocks for hip fracture pain have targeted the femoral nerve. The PENG block is a relatively novel ultrasound guided block that was first described in 2018 as an alternative to the more traditional femoral block for regional hip analgesia in hip fracture patients. The PENG block targets articular branches of the obturator nerve and accessory obturator nerve, as well as branches of the femoral nerve, the combination of which richly innervate the anterior hip capsule. In a case series of 5 patients presenting to the Emergency Department with hip fracture pain, the PENG block was demonstrated to be an effective nerve block for hip analgesia by reducing the numerical rating scale pain scores by 7 points on a 10 point scale. A larger study compared the PENG block to placebo, also in hip fracture patients presenting to the Emergency Department, and demonstrated a significant decrease of 3 in the dynamic NRS pain score at 1 and 3 hours post-block. A Cochrane review in 2017 demonstrated femoral blocks to have a 3.4 point reduction in pain scores compared to placebo. No study to date has compared the PENG block to the femoral block for acute hip fracture pain.

This study aims to compare the PENG block with femoral block for acute hip fracture pain in patients upon presentation who have not undergone surgical repair. Patients presenting to the hospital with a diagnosis of hip fracture and consenting to analgesic block will receive either a PENG or femoral block. The choice of block will be dictated by a randomized monthly schedule, and all patients presenting during each four-week period will receive the designated block. The primary outcome will be the change in NRS pain score from pre-block to one-hour post-block. Secondary outcomes will include NRS pain scores and opioid consumption for 24 hours post-block. A sub-group analysis will be performed to determine any difference in efficacy in patients with intracapsular versus extracapsular fractures.

This will be a pragmatic study with a multiple crossover cluster-controlled design. In this type of trial an intervention is implemented for all patients for a limited period of time and then substituted with the alternate intervention for a comparable amount of time. The order of intervention will be randomized. The repetition of the study periods, especially if conducted over a period of a year of more, has the effect of reducing time-dependent confounding from background improvements in healthcare and regression to the mean. The Hawthorne effect will be limited in this particular case because both of the interventions are already routinely and interchangeably used in our current practice for hip fracture analgesia. Research consent is usually waived in this type of trial design because the treatment received by subjects is identical to standard care and the exposure within a subject population is based only on time period rather than patient characteristics or consent.

As per current standard of care, all hip fracture patients admitted Monday - Friday, 7AM - 5PM, will be offered an analgesic lower extremity peripheral nerve block. Each month of the study will be randomized to either PENG or femoral block. All patients who consent to a block during each month will receive the designated block.