Femoral rami obturator nerve trunk (FRONT) block in intramedullary nailing surgery: A motor-sparing approach to anterior hip analgesia

Dear Editor,

Effective postoperative pain management is essential for optimal recovery and early mobilisation and rehabilitation following hip surgery in geriatric trauma patients.. Regional anaesthesia techniques, such as femoral nerve, lumbar plexus, pericapsular nerve group (PENG), and fascia iliaca blocks, have gained attention for their opioid and sometimes motor-sparing potential, as well as the ability to provide targeted analgesia for the anterior hip joint.[1] Nevertheless, the anterior hip joint coverage needs the constant contribution of the femoral and obturator nerves to provide adequate pain relief.[2] This case series reports on three patients who underwent intramedullary femoral nailing for hip (trochanteric) fracture under spinal anaesthesia. They received preoperative femoral rami obturator nerve trunk (FRONT) block, a novel regional anaesthesia technique described by Jessen et al.[3] as a promising solution to the long-standing challenge of anaesthetising both the femoral and obturator nerve branches in the anterior hip joint for postoperative pain control, addressing a more comprehensive coverage of anterior hip innervation. Written informed consent was obtained from the patients and to publish this case series. Premedication included intravenous midazolam 1 mg. The vital parameters were monitored. The ultrasound-guided FRONT block was performed at the infrainguinal level, targeting the iliopsoas plane. Using the same needle approach, the subpectineal compartment was also accessed [Figure 1]. We used ultrasound and electrical nerve stimulation guidance (0.4 mA, 0.1 ms, without eliciting a motor response) to avoid direct involvement of the femoral nerve. A total of 40 mL (20 mL for the iliopsoas plane and 20 mL for the subpectineal compartment) of 0.125% plain levobupivacaine was administered. Spinal anaesthesia with the patient in sitting position (prilocaine 40 mg) was administered aseptically at the L3-L4 level with a 25-G Whitacre needle. No intraoperative complications were observed, and the patients’ vital signs remained stable. Spontaneous ventilation was maintained, and intraoperative sedation was achieved with intravenous midazolam 1 mg. After the spinal anaesthesia resolved, all patients experienced effective postoperative pain control without motor weakness. Perioperative care was standardised for all patients. Postoperative analgesia included intravenous paracetamol 1 g at the patient’s request, with intravenous ketorolac 30 mg or tramadol 50 mg administered based on a patient-reported numerical rating scale score >5. Patients were followed for 36 hours postoperatively and assessed for pain, motor function, and complications. None of the patients exhibited signs of local anaesthetic systemic toxicity or other complications (such as motor weakness) related to the blocks, and no opioids were administered. Preoperative patients’ characteristics and their postoperative outcomes are presented in Table 1.

Figure 1.

(a) Procedural setup for the FRONT block: Skin markings indicate the pre-block identification of the lateral femoral cutaneous nerve and the anterior superior iliac spine (ASIS) using a low-frequency transducer. The injection is then performed following the method described by Jessen, positioning the probe infrainguinally approximately 6–7 cm distal and 2 cm medial to the anterior superior iliac spine (ASIS). (b) and (c): Ultrasound image of the infrainguinal region: The FRONT block achieves anterior hip analgesia using a single needle approach with a dual injection technique. The injection site is not on the same ultrasound plane as the probe is tilted to identify two distinct planes: the subpectineal interfascial plane (1, yellow arrow) and the iliopsoas plane (2, red arrow). Ultrasound guidance is essential for precision. Note that the femoral nerve is located around 1.5 cm from the hip capsule. Needle trajectory and injectate spread are shown. A = artery; FH = femoral head and surrounding capsule; FN = femoral nerve; IP = iliopsoas muscle; LA = local anaesthetic; OE = obturator externus muscle; PECT = pectineus muscle; V = vein

Table 1.

Demographics of the patients and all the outcomes

	Patient 1	Patient 2	Patient 3
Age (years)	82	82	79
Gender (Male/Female)	Female	Female	Female
Weight (kg)/BMI, (kg/m2)	50/25	50/25	80/30
ASA-PS/Comorbidities	2/hypertension	3/diabetes, MDC hypertension	3/hypertension, diabetes
NRS-dynamic pre-block	8	8	7
NRS-dynamic (20 min) post-block	3	2	4
Type of surgery/duration (min)	nailing/45	nailing/50	nailing/45
Spinal level/drug	L3-L4/prilocaine 40 mg	L3-L4/prilocaine 40 mg	L3-L4/prilocaine 40 mg
2 h Bromage	IV	III	IV
4 h* Bromage	IV	IV	IV
NRS post-surgery	0	0	0
4 h* NRS-rest/dynamic	0/0	0/0	0/0
6 h NRS rest/dynamic	0/2	0/1	0/2
8 h NRS rest/dynamic	0/3	1/3	1/4
12 h NRS rest/dynamic	1/4	1/4	2/5
First request analgesia (h)/dynamic NRS	25/4	30/5	22/6
24 h NRS rest/dynamic	2/4	2/4	0/2
Second request (h)	33	Nil	31
Third request (h)	Nil	Nil	Nil
36 h NRS rest/dynamic	0/3	0/0	0/3
Analgesia administered	1	1	1
Total postoperative analgesic use	Paracetamol 2 g	Paracetamol 1 g	Paracetamol 2 g
Side effects	Nil	Nil	Nil
Clavien-Dindo classification	1	1	1

Bromage motor blockade score: I, complete; II, almost complete; III, partial; IV, none. (Acta Anaesthesiol Scand Suppl 1965; 16: 55-69). FRONT Block: 0.125% plain levobupivacaine total volume 40 mL. Analgesia: 1, IV paracetamol 1 g; 2, IV ketorolac 30 mg; 3, IV tramadol 50 mg* Resolution of spinal anaesthesia. COPD=Chronic obstructive pulmonary disease; BMI=Body mass index; ASA-PS=American Society of Anesthesiologists Physical Status; NRS=Numeric rating scale; MDC=Major depression condition

The femoral triangle, defined by the inguinal ligament, sartorius, and adductor longus muscles, is a key passage for neurovascular structures. Below the inguinal ligament, the iliopectineal ligament (continuous with the iliofemoral ligament of the hip capsule) forms a fascial barrier between the iliopsoas plane and the subpectineal compartment. This anatomical separation can limit the spread of local anaesthetics in blocks such as the PENG block. Although the PENG block was introduced to spare motor function, subsequent studies have shown occasional quadriceps weakness[4] and inconsistent coverage of the obturator nerve.[5] The FRONT block is designed to overcome these limitations by combining two target planes – the iliopsoas and subpectineal space – via a single infrainguinal injection. The novelty of our case series is related to dual-target hip analgesia via one infrainguinal injection, achieving motor-sparing coverage of the femoral and obturator nerves. Preservation of motor function remains an observational finding rather than a comparative outcome. Larger, controlled studies are needed to confirm efficacy and safety.

Declaration of patient consent

Written informed consent has been obtained from the patient/first line relatives of the patient for publication of all materials and images (including radiological and ultrasonographic) in scientific journals. The authors certify that they have obtained all appropriate patient consent forms. In the form, the patient/his relatives consented to his images and other clinical information to be reported in the journal. The patient understands that his name and initials will not be published.

Authors Contributions

FM: Concepts, design, investigation, data curation, manuscript writing and reviewing. TS: Concepts, investigation, data curation, manuscript reviewing. GC: Investigation, data curation, manuscript reviewing. SP: Investigation, data curation, manuscript reviewing, supervision.

Disclosure of use of artificial intelligence (AI)-assistive or generative tools

The AI tools or language models (LLM) have not been utilised in the manuscript, except that software has been used for grammar corrections and references.

Conflicts of interest

There are no conflicts of interest.

Funding Statement

Nil.