A retrospective comparison of percutaneous radiofrequency ablation of osteoid osteoma using three anesthesia modalities

INTRODUCTION

Osteoid osteoma (OO) is a benign bone tumor most common in adolescence or young adulthood. These lesions account for 10–12% of all benign bone tumors and 2–3% of primary bone tumors with a predilection for the long bones of the lower extremities.^[1,2] Historically, surgical excision has served as the principle treatment for OO, but in recent years, percutaneous radiofrequency ablation (PRFA) has emerged as the treatment of choice and boasts superior long-term efficacy at lower cost.^[3,4]

Anesthetic management during PRFA of OO has presented several critical challenges. Periprocedural pain is often exquisite in these patients as the periosteum and marrow display increased nociceptive sensitivity in comparison to other tissues,^[5] as does the tumor itself and the nonneoplastic reactive tissues that surround the tumor.^[6,7] As such, patients typically require a general anesthetic (GA) or monitored anesthesia care (MAC) with deep sedation (DS).^[8] Unpleasant side effects from these types of anesthetics include nausea, vomiting, delayed wakeup, and sore throat.^[8] At our institution, these cases are associated with post-procedural opioids.

Regional anesthesia (RA) is a technique that has been gaining popularity in the interventional radiology (IR) suite. Specifically, it has been used by interventional oncology for renal, hepatic, and uterine tumor ablations with studies showing increased patient satisfaction with decreased periprocedural pain and opioid utilization.^[9-11]

The purpose of this study was to evaluate the safety and effectiveness of ultrasound-guided RA (USGRA) with MAC plus light sedation (LS) versus GA versus MAC with DS for PRFA of lower extremity OO.

MATERIAL AND METHODS

Inclusion and exclusion criteria

This retrospective study received Institutional Review Board approval and is HIPAA compliant. All patients with OO diagnosed through CT and referred for treatment with PRFA at a single tertiary care academic medical center between May 2016 and February 2020 were reviewed. Twenty-one cases were identified by this initial screening. Inclusion criteria were age ≥14 years and lesions of the mid-to-distal femur, leg, and foot. Younger patients were excluded as they typically receive GA for procedures due to inability to cooperate. Nineteen patients were identified by these criteria [Figure 1]. Collected demographic data included age, gender, tumor location, and tumor volume. Tumor volume was obtained by measuring tumor nidus on CT in three dimensions and calculating volume as a rectangular prism.

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Figure 1:

Visual representation of study design with inclusion and exclusion criteria.

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RESULTS

Population

The study population included 12 men and 7 women with a mean age of 20.9 ± 5.9 years (range 14–35 years). Median tumor volume was 66 mm³ [IQR 36, 150]. The most common lesion location was the tibia (10 cases), followed by the femur (4 cases), fibula (3 cases), and calcaneus (2 cases). Four patients were given pre-procedure USGRA and MAC with LS, eight patients underwent the procedure using MAC with DS, and seven were provided GA. No significant differences were observed in patient demographic or tumor characteristics between the three study groups [Table 1]. A full report of patient data is listed in Figure 2.

Table 1: Patient characteristics in the three anesthesia groups.

	General anesthesia	MAC with deep sedation	RA with MAC plus light sedation	P-valuea
n	7	8	4
Age (years)
Mean (±SD)	20.7 (5.8)	21.9 (7.3)	19.5 (3.9)	0.940
Gender (male)
Frequency (% group)	4/7 (57%)	6/8 (75%)	2/4 (50%)	0.641
Tumor location
Frequency	Femur 3/7	Femur 1/8	Femur 0/4	0.128
	Tibia 4/7	Tibia 2/8	Tibia 4/4
	Fibula 0/7	Fibula 3/8	Fibula 0/4
	Calcaneus 0/7	Calcaneus 2/8	Calcaneus 0/4
Tumor volume (mm3)
Median [IQR]	80 [36,120]	102 [29,357]	57 [39,354]	0.852

SD: Standard deviation, IQR: Interquartile range, MAC: Monitored anesthesia care, RA: Regional anesthesia. ^aKruskal–Wallis test used to compare interval data and Pearson’s Chi-squared test used to compare proportions

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Figure 2:

Patient-specific demographic, tumor, anesthetic, and periprocedural outcomes data.

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DISCUSSION

The growth of RA techniques has provided opportunity to avoid GA, minimize opioid utilization, and decrease periprocedural pain. In the interventional space, phrenic nerve, brachial plexus, femoral and sciatic nerve, intercostal, transversus abdominus plane, and stellate ganglion blocks have been widely adopted for these purposes.^[9] Within the realm of interventional oncology, the application of RA has been limited. Although the use of RA has been studied in the ablation of renal, hepatic, and uterine fibroid tumors, implementation of RA for lower extremity musculoskeletal IR procedures has not yet been explored.^[10,12,13] Lower extremity blocks are routinely used during orthopedic surgeries and percutaneous endovascular laser ablations for venous insufficiency, but not during IR or interventional oncology musculoskeletal procedures.^[14-18]

In this study, USGRA with sciatic and tibial nerve blocks plus MAC with LS was utilized as an alternative to GA and MAC with DS for the treatment of PRFA of lower extremity OO. Conventionally, GA or MAC with DS is required as patients experience exquisite periprocedural pain, especially during ablation. As reported by Rosenthal et al., OO is a bone tumor uniquely interlaced with nerve fibers.^[6,7] This feature is thought to be responsible for the abrupt onset of pain and hemodynamic response on entering the tumor with a needle and possibly for the early post-procedural pain as well. In this analysis, the acute post-procedural pain from PRFA resolved within 2 h. The use of USGRA may be an effective means of circumventing this phenomenon, and therefore, USGRA is well positioned to serve as an alternate primary anesthetic.

The present study demonstrates that tumor ablations larger than 100 mm³ frequently required opioid analgesics. We hypothesize that tumor volume is positively associated with both periprocedural opioid administration and immediate post-procedural discomfort, but a larger cohort is needed to assess this relationship. In addition, future studies involving USGRA for PRFA of OO should utilize conscious sedation without propofol to assess blunting of the intraprocedural pain and hemodynamic response to ablation.

OO lends itself for selective nerve blockade. Nerve targeting with ultrasound guidance decreases the amount of LA needed, decreases the risk LA toxicity, and results in faster block onset and resolution.^[19] As the primary nociceptive stimulus in these procedures involves manipulation of the periosteum, marrow, tumor body, and surrounding reactive tissues, lower extremity sclerotomes should be utilized for optimal target nerve selection.^[19,20] In our retrospective review, this technique was successful in all patients. None required conversion to GA, and all blocks had complete post-procedure sensorimotor resolution.

Fall risk is temporarily elevated following delivery of lower extremity RA. This relationship is well documented in RA for orthopedics surgeries, but has not been explored in RA for IR musculoskeletal procedures.^[21,22] In the present study, no patients experienced a fall. Short-acting LAs pose a lower overall fall risk due to rapid return of sensorimotor function and should serve as first-line agents.

The main limitation of RA in the cases reviewed was a trend toward increased recovery time in the post-procedure recovery area compared to the other two groups, though non-inferior compared to the other two groups. This can be addressed with the use of short-acting agents, such as chloroprocaine and mepivacaine, which provide periprocedural analgesia with quick block resolution, thereby minimizing recovery time from anesthesia.^[23] In addition, a protocol can be put in place to have patients use a lower extremity soft brace with a wheelchair escort to expedite discharge. Of note, RA may not be suitable for young children as they routinely need GA for ablative procedures due to not being able to tolerate laying immobile for a relatively prolonged period of time and the need for a secured airway.

An inherent limitation of this study is its retrospective nature and small number of patients. We acknowledge that three of the four USGRA patients had relatively small tumor volumes in comparison to the other two groups; however, one RA patient had a very large tumor measuring 450 mm³ and experienced no immediate post-procedure pain or need for opioid analgesia. In addition, there were four different short-acting mixtures of LA for each of the patients. Future studies should aim to use one standard LA mixture for a better homogenous comparison. Moreover, patients were not evaluated in the days following PRFA. As such, the present study is unable to evaluate for differences in patient discomfort following the immediate post-procedural period. However, in our experience, we have observed that pain is most apparent immediately following PRFA and rapidly subsides within a few hours.^[24] In addition, given the duration of anesthetic effects, we do not predict that anesthetic choice would influence patient discomfort in the days following ablation.

CONCLUSION

Lower extremity USGRA with light procedural sedation can be a safe and effective primary anesthetic for PRFA of OO with non-inferior recovery time as an alternative to either GA or MAC with DS. Future studies should include more patients to show its statistical superiority.