Ultrasound guided pericapsular nerve group (PENG) block resulting in reduction of dislocated prosthetic hip

Summary

A 78‐year‐old woman with a prosthetic hip dislocation underwent a pericapsular nerve group block for regional anesthesia. The hip spontaneously reduced before manual intervention, likely due to the block's analgesic and muscle‐relaxing effects. Compared to other techniques, this block effectively targets hip innervation while sparing motor function. This case highlights its potential for managing hip dislocations safely, especially in patients at risk from sedation.

We present the case of a 78‐year‐old woman admitted with a prosthetic hip dislocation, reduced inadvertently after a pericapsular nerve group (PENG) block. The patient's medical background included hypertension and mild dementia. We planned to perform a closed reduction under regional anaesthesia to reduce the risk of postoperative delirium and facilitate an enhanced recovery. After obtaining informed consent and applying monitoring, we performed a PENG block with 20 ml bupivacaine 0.25% and 10 ml lidocaine 1%. The block technique used was the originally described one by Peng et al. [1]. After 10 min, the hip joint was mobilised to test the efficacy of the block, and the patient reported no pain. Once on the surgical table, the initial X‐ray revealed the hip joint had been reduced. The patient was discharged home a few hours later.

The success of a closed reduction increases when good pain control is achieved due to the relaxation of the peri‐articular muscle groups facilitating the manoeuvre [2]. Fascia iliaca compartment block [3] and femoral nerve block [4] have been described to facilitate hip joint reduction, but these blocks alone may not provide adequate analgesia to the joint and can cause weakness of the quadriceps muscle. High branches of the femoral nerve, the obturator nerve and the accessory obturator nerve provide innervation to the hip capsule. Therefore, these nerves should be the targets for hip joint analgesia. The PENG block, a technique developed for hip arthroplasty analgesia with motor sparing benefits, could be used to achieve this goal [1]. Sedation is not without risk or adverse effects and there may be benefits to avoiding it in certain cases [4, 5].

We hypothesise that the hip reduced spontaneously either because of the block alone, or during the subsequent movement used to assess the block (no obvious time of reduction was noted). In either case, we suggest the PENG block achieved complete analgesia and abolition of reflex‐mediated muscle stiffness [6], permitting reduction. In the absence of afferent nociception, the spinal reflex which keeps the peri‐articular muscle groups contracted was likely abolished. The spinal nociceptive reflex would not be expected to be completely abolished by fascia iliaca block, femoral nerve block or sedation alone [7].

This case illustrates how complete joint anaesthesia may result in joint reduction without further intervention.