Chemical neurolysis for the conservative treatment of hip fractures

Abstract

Aim: Hip fracture management is challenging when surgical risks outweigh benefits. Inadequate analgesia from conservative treatments prompted new procedures targeting hip capsule denervation. This study evaluates the efficacy and safety of single injection chemical hip neurolysis in the pericapsular nerve group plane.

Materials & methods: In eligible patients, an ultrasound-guided diagnostic block was performed using 5 ml of 2% lidocaine in the pericapsular nerve group plane. If positive, 6 ml of 99.9% alcohol was administered.

Results: From May 2022 to May 2023, five patients underwent hip neurolysis. None reported pain at day 5 or during follow-up. There were no adverse effects.

Conclusion: Chemical neurolysis seems to provide effective and safe conservative treatment for hip fractures, offering reliable analgesia for nonsurgical candidates.

Plain Language Summary

Managing hip fractures is difficult, especially when surgery is too risky. Traditional pain relief methods often do not work well enough, so doctors are exploring new ways to reduce pain by targeting the nerves around the hip.

In this study, we looked at a new technique called chemical neurolysis to see if it can safely and effectively relieve pain for people with hip fractures who can not have surgery.

For this procedure, doctors first used a special technique to find the right spot near the hip using ultrasound. Then, they injected a small amount of a numbing medicine called lidocaine to see if it helped with the pain. If it did, they followed up by injecting alcohol to block the pain nerves more permanently.

Between May 2022 and May 2023, five patients received this treatment. All of them reported no pain 5 days after the procedure and there were no negative side effects. We continued to check on them regularly to monitor their progress.

In conclusion, chemical neurolysis appears to be a safe and effective way to manage hip fracture pain for patients who cannot undergo surgery, providing reliable pain relief without major risks.

Plain language summary

Article highlights.

• Conservative treatment options for hip fractures often provide insufficient analgesia.

• Chemical neurolysis offers a safe and effective conservative treatment option for hip fractures in nonsurgical candidates.

• A multidisciplinary approach involving orthopedic and anesthesiology teams enhances patient care and selection for neurolysis.

• In our retrospective case series, chemical hip neurolysis was achieved with a single ultrasound-guided injection of absolute alcohol in the pericapsular nerve group plane after a positive diagnostic block.

• Targeting only the pericapsular nerve group plane with a single needle approach expedites identification of landmarks and simplifies the technique, enhancing reproducibility.

• All patients who underwent the procedure were pain free and able to tolerate the sitting position and hygiene care during the follow-up period and no adverse effects were reported.

• Future research directions include conducting large prospective studies to assess the efficacy and safety of this approach, as well as investigating the potential benefits of injecting neurolytic agents directly at the fracture site or intracapsular to the hip joint for enhanced pain relief.

1. Background

Hip fractures present significant challenges in patient management, particularly in cases where surgical intervention carries high risks compared with the potential benefits [1,2]. Conservative treatment options for hip fractures often provide insufficient analgesia. In recent years, several new regional anesthesia techniques have been developed to denervate the hip capsule, including chemical neurolysis [3,4].

Understanding the anatomical basis of hip joint innervation allows the identification of potential nerves to target [5]. According to current literature, the area with the densest nociceptive innervation was found to be the superior portion of the anterior capsule [6]. The anterior capsule is consistently supplied by two major nerves, the femoral nerve and the obturator nerve, with inconsistent contribution from the accessory obturator nerve.

Since the pericapsular nerve group (PENG) block specifically targets the articular branches of the femoral and obturator nerves, which innervate the area of the articular capsule with a higher density of nociceptor receptors, this approach alone is expected to provide significant pain relief [7,8]. Previous studies have successfully achieved hip neurolysis by targeting the nerve branches through multiple injections [4,9]. We propose that neurolysis through a single injection in the PENG provides adequate analgesia in patients whose surgical risks outweigh benefits.

The primary objective of the neurolysis was to achieve effective pain relief in patients with hip fractures who had a significant decline in functional capacity due to heavy comorbidities and were previously unable to ambulate. We describe a case series of five patients who underwent a single injection pericapsular hip absolute alcohol neurolysis as a conservative treatment for intracapsular hip fracture in patients within our department’s protocol.

2. Methods

The protocol of chemical neurolysis as a conservative treatment for hip fracture patients was developed by our anesthesiology department, aiming to provide a framework for evaluating the patient’s eligibility for chemical neurolysis, as well as to guide and standardize the execution of the procedure. The protocol underwent thorough development and revision to streamline the procedure, ensuring its reproducibility and ease of implementation.

After admission to the hospital and confirmation of the hip fracture diagnosis by an orthopedic surgeon, the anesthesiology team conducts a medical evaluation of the patient. During the evaluation process, the orthopedic and anesthesiology teams collaborate to identify suitable patients. This collaborative effort emphasizes the multidisciplinary approach to patient management, promoting comprehensive and tailored care for individuals with hip fractures. By implementing the protocol, we can assess the suitability of chemical neurolysis in patients who are at high surgical risk and whose main objective is pain relief.

The protocol was conducted in collaboration between the orthopedic and anesthesiology departments. Patients who were deemed inoperable by either the orthopedists and/or anesthesiologist were evaluated for inclusion and exclusion criteria to determine their eligibility for the hip neurolysis procedure. Inclusion and exclusion criteria are highlighted in Table 1.

Table 1.

Inclusion and exclusion criteria for chemical neurolysis for hip fracture.

Inclusion criteria	Exclusion criteria
Radiographic confirmation of hip fracture	Inability to assume a dorsal decubitus position
Moderate to severe uncontrolled pain at rest or with mobilization	Hemodynamic or respiratory instability
No previous ambulation	Previous total hip arthroplasty or previous denervation
Positive diagnostic block	Coagulopathy (platelets <50,000 × 103/μl or International Normalized Ratio >1.5)

After meeting the inclusion criteria and confirming the absence of any exclusion criteria, the pericapsular hip neurolysis technique was discussed with the patients and their families. Written informed consent was then obtained, ensuring that the patients and their families had a clear understanding of the procedure and its potential implications.

The procedure was performed by the same select group of anesthesiologists who are experts in regional anesthesia techniques.

It was conducted under ultrasound guidance using a low frequency 2.0–8.0 MHz curved probe (Samsung® HS40, Suwon, South Korea) with the patients in supine position. The anatomical references employed were those used for the PENG block, namely the antero-inferior iliac spine and ilio-pubic eminence. The iliopsoas tendon was identified and a 22G 100 mm echogenic Pajunk® (Geisingen, Germany) needle was inserted in-plane from lateral to medial, deep to the iliopsoas tendon until contact with the pubis ramus is made and then slightly withdrawn (Figure 1).

Figure 1.

Ultrasonography landmarks for identifying the pericapsular nerve group plane include the AIIS, the ileo-pubic eminence and the PM tendon. Under ultrasound guidance, the needle is advanced immediately lateral to the AIIS and positioned between the ileo-pubic eminence and the PM tendon. The spread of the injected substance along with the superior displacement of the psoas tendon can be observed (not shown).

AIIS: Anterior inferior iliac spine; FA: Femoral artery; FN: Femoral nerve; FV: Femoral vein; IM: Iliacus muscle; IPE: Iliopectineal eminence; IPT: Iliopsoas tendon; PcM: Pectineus muscle; PM: Psoas muscle.

Initially, a diagnostic block was performed using 5 ml of 2% lidocaine. With the needle remaining in place, the block’s efficacy was evaluated by performing external, internal rotation and flexion of the hip joint. The block was considered positive if there was a significant reduction or absence of pain during these maneuvers 10 min after the block. Subsequently, the needle’s location was confirmed and 6 ml of 99.9% ethyl alcohol was administered. Prior to needle removal, 1 ml of local anesthetic was flushed through the needle to prevent any potential damage to the surrounding soft tissues caused by the alcohol.

Regarding conventional analgesia, all patients received a prescription for intravenous paracetamol every 8 h and ketorolac every 12 h for 2 days, along with intravenous tramadol as needed during their stay, according to local protocol. Additionally, upon discharge, they were provided with prescriptions for oral paracetamol and tramadol for use as needed.

The procedure was documented in each patient’s medical record, including the details of the procedure, including information on the patient’s pre-procedural pain level, the presence of positive diagnostic block response and any relevant observations. Pain assessment was conducted at 1st day and 5 days postprocedure to evaluate the effectiveness of the intervention in providing pain relief, by performing flexion, internal and external rotation of the hip joint. Pain was assessed using the visual analog scale. Patients were classified as pain-free when their visual analog scale score was less than three, allowing for unrestricted passive and active mobilization. To facilitate the clinical evaluation and decision-making process, the American Society of Anesthesiologists physical status classification, functional capacity measured in metabolic equivalents using the Duke Activity Status Index and the Nottingham hip fracture score, a validated system for predicting 30-day mortality post-hip fracture surgery, were utilized.

Following the procedure, the patients were closely followed by the orthopedic surgery department in an outpatient setting, with a follow-up period of approximately 6 months after the procedure. During this follow-up, the efficacy of the neurolysis was re-evaluated to determine its long-term impact on pain management and functional capacity.

3. Results

This retrospective case series studied patients with acute inoperable hip fracture from May 2022 to May 2023. During this 1-year period, a total of five patients aged over 50 years, who met the inclusion criteria, underwent the pericapsular hip neurolysis procedure. None of the patients was previously able to ambulate.

Informed consent was obtained from all patients prior to the procedure. At the 1-day follow-up, one patient experienced pain, which resolved by the 5-day evaluation. None of the patients reported pain at the 5-day follow-up and all were discharged pain-free following the procedure. There were no reported adverse effects in any of the cases.

At the 6-month follow-up, three of the patients had died due to their comorbidities but were pain-free at their last assessment 3 months after the procedure. All patients remained pain-free during the follow-up period.

Table 2 summarizes ‘patients’ hospitalization, calculated risk scores and pain assessment during follow-up.

Table 2.

Patient characteristics, hospitalization, calculated risk scores and pain assessment.

ASA Physical Status Classification	Functional capacity (METS)‡	Nottingham Hip Fracture Score predicted 30-day mortality (%)	Length of stay	Days from admission to procedure	Days from procedure to discharge	Pain before the procedure	Pain 10 min after diagnostic block†	Pain at day 1 after procedure†	Pain at day 5 after procedure†	6-month mortality	Pain at the 6th month follow-up†
IV	2.74	2,7	55	51	3	8	No	2	1	Yes	–
IV	2.74	11	11	2	8	6	No	5	2	Yes	–
IV	2.74	11	28	22	5	5	No	0	0	No	1
IV	2.74	34	6	5	1	5	No	2	2	No	2
IV	2.74	11	8	6	2	4	No	1	2	Yes	–

^†Patients were classified as pain-free for VAS scores <3, enabling unrestricted passive and active mobilization.

^‡Functional capacity in METS was estimated using DASI.

DASI: Duke Activity Status Index; MET: Metabolic equivalent; VAS: Visual analog scale.

4. Discussion

The multidisciplinary approach employed in this protocol allowed for comprehensive evaluation and enhanced patient care, particularly in the selection of individuals who would benefit from pericapsular hip neurolysis. This approach allowed us to offer a conservative treatment option for pain relief to patients who were not suitable candidates for surgical intervention. These patients had little to no chance in regaining their ability to walk, since they were previously bedridden and had a very poor functional capacity due to heavy comorbidity and sarcopenia. The focus of this treatment protocol was on providing effective pain relief and enhancing the patients’ overall care [9]. The ability to flex the hip enables the patient to assume a sitting position, while the ability to perform external rotation is essential for providing hygiene care to the patients. The pericapsular hip neurolysis offers the advantage of pain relief along with the ability for patients to sit comfortably and receive hygiene care, distinguishing it from standard conservative treatment.

In our study, the pericapsular hip neurolysis procedure was performed by a select group of anesthesiologists who possess expertise in regional anesthesia techniques. This factor significantly reduces the likelihood of procedural failure or adverse effects being attributed to a lack of skill or technical proficiency [10]. Thus, any potential failures or limitations observed in the procedure’s outcomes are less likely to be attributed to operator-related factors.

The potential adverse effects of the pericapsular hip neurolysis procedure are important to consider. These range from paresthesia, muscular weakness and, myositis to allergic reactions, systemic toxicity to local anesthetics, bowel perforation and urethral injury [8,11]. However, it is noteworthy that none of these adverse effects were observed in the patients included in our study.

In some cases, a worsening of pain within the first 24 h following pericapsular hip neurolysis can be observed. This phenomenon may be attributed to the destruction of nerve tissue during the procedure, which can lead to transient exacerbation of pain before the analgesic effects of neurolysis take full effect. Alcohol acts by damaging the nerves by denaturating proteins and fatty substance extraction, possibly causing neuritis and leading to Wallerian degeneration distal to the site of injection [11,12].

Therefore, it is not uncommon to find one patient experiencing pain at the 24-h mark in this case series. While the transient exacerbation of pain in the early postprocedural phase may raise concerns, it is crucial to reassure patients and caregivers that this phenomenon is expected and temporary.

It is important to note that the neurolysis technique typically requires around 24–48 h for its analgesic effects to become noticeable [12]. Therefore, the presence of pain at the 24-h assessment should not be considered a predictor of procedure failure. However, the local anesthetic administered during the diagnostic block provides initial analgesia, allowing the neurolysis procedure time to take effect and prevent significant pain.

We opted for alcohol as our neurolytic agent, in spite of phenol, given its availability at our institution. Nevertheless, alcohol may offer some advantages over phenol, such as longer duration of action, more intense neurolytic block and less systemic side effects [11].

The rationale behind pericapsular hip neurolysis primarily targeting the nerves to the anterior capsule is supported by the anatomical distribution of nociceptive innervation in the hip joint [6]. Therefore, by blocking the articular branches of the femoral and obturator nerves, which supply the anterior capsule, the procedure aims to provide effective analgesia in patients with hip fractures, even without directly targeting the posterior capsule [13]. Studies investigating the spread of injectate after the PENG block support this theory [8]. Injected volumes of 10–20 ml have been considered sufficient to adequately cover the anterior hip capsule [14]. It is important to acknowledge that alternative approaches, such as posterior neurolysis, may have their merits and could potentially provide additional pain relief in specific cases [15]. Our case series supports this notion that anterior hip capsule neurolysis within the PENG plane is sufficient to provide effective analgesia in most cases. Chemical neurolysis appears to be more effective than other techniques, such as thermal or cryoablation, likely due to the creation of a larger lesion size, which may account for anatomical variation [16].

A previous study with a larger patient cohort have demonstrated the efficacy of chemical neurolysis in pain relief; however, they aimed to target both the femoral nerve articular branches and the obturator nerve articular branches separately, requiring the use of two distinct needles [9].

We have found our approach to be equally efficacious in pain management, with some notable advantages. Firstly, by targeting the PENG plane, a familiar territory for most experienced anesthesiologists versed in regional techniques, we expedite both identification of landmarks and execution of the procedure. Moreover, the use of a single needle simplifies the technique, enhancing its reproducibility. Additionally, we achieved effective neurolysis with a lower volume of absolute alcohol, theoretically mitigating the risk of side effects.

Recent studies have shed light on the mechanisms of pain following bone fractures. There is evidence suggesting that the primary cause of pain following a fracture is the mechanical distortion of the periosteum, which is the most densely innervated part of the bone [17]. Activation and sensitization of bone nociceptors and ectopic nerve sprouting contribute to enhanced pain signaling after a fracture [18]. Therefore, treatment strategies that specifically target the periosteum, such as the injection of neurolytic agents at the fracture site or intracapsular to the hip joint, may offer additional analgesic benefits [19].

The follow-up in outpatient orthopedic consultations allowed for evaluation of long-term adequacy of analgesia provided through pericapsular hip neurolysis, assessing if sustained pain relief had been achieved. By monitoring patients in the outpatient setting, orthopedic surgeons can ensure that the analgesic effects of the procedure persist and address any concerns or adjustments needed to optimize pain management.

5. Conclusion

Our single injection chemical neurolysis approach in the PENG plane presents a promising conservative option for hip fracture management, offering a simple, effective and safe pain relief for nonsurgical candidates. Further research is warranted to validate the efficacy of this approach, as well as investigating the potential benefits of injecting neurolytic agents directly at the fracture site or intracapsular to the hip joint for enhanced pain relief. The success of this case series also emphasizes the importance of effective collaboration and communication between the orthopedic and anesthesiology teams in delivering high-quality patient care.

Author contributions

All authors contributed equally to the manuscript.

Financial disclosure

The authors have no financial involvement with any organization or entity with a financial interest in or financial conflict with the subject matter or materials discussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending or royalties.

Competing interests disclosure

The authors have no competing interests or relevant affiliations with any organization or entity with the subject matter or materialsdiscussed in the manuscript. This includes employment, consultancies, honoraria, stock ownership or options, expert testimony, grants or patents received or pending, or royalties.

Writing disclosure

No funded writing assistance was used in the creation of this manuscript.

Ethical conduct of research

All patients provided written informed consent for the procedure and inclusion in this study, except for one patient. For this patient, the legal guardian provided written consent due to the patient’s cognitive impairment from dementia, which rendered the patient incapable of understanding the risks and benefits of the procedure. The hospital’s legal department is involved in these matters to ensure compliance with local laws.