Postoperative Dysesthesia Secondary to Thermal Injury Following Biportal Endoscopy for Lumbar Canal Stenosis: A Report of 3 Cases and Technical Details of Radiofrequency
Article information
Abstract
Postoperative dysesthesia following lumbar spine surgery is a highly bothersome symptom in the follow-up period. Although many factors contribute to this condition, the most important one is the use of radiofrequency in endoscopic spine surgery. Nonetheless, there is widespread acceptance regarding the use of radiofrequency in endoscopic spine surgery, and the literature contains few reports related to thermal damage to nerves. We describe 3 cases of nondermatomal dysesthesia syndrome in patients who had undergone lumbar unilateral biportal endoscopic surgery for lumbar spinal stenosis. All diagnostic modalities were equivocal, and no pathological lesion was identified. Therefore, we interpreted the dysesthesia as secondary to thermal damage to neural structures, resulting from the radiofrequency.
INTRODUCTION
Over the past 2 decade, minimally invasive surgery (MIS) has taken over the place of conventional surgery in number of disciplines. Adopting the principles of MIS in spine, surgery is generally performed using tubular system or endoscope and other specialised instruments like radiofrequency (RF) are required for soft tissue dissection, haemostasis and coagulation. MIS especially endoscopic spine surgery (ESS) needs clear visible operative field which warrants haemostasis as a very important component of surgeons armamentarium. RF current can be used as tool for haematosis with an added advantage of simultaneous soft tissue dissection and coagulation with a possible disadvantage injury to surrounding tissue. The reported incidence of transient paresthesia is approximately around 0.14% in biportal endoscopic surgery [1]. In this article, we describe 3 cases of nondermatomal dysesthesia following unilateral biportal endoscopic spine surgery (UBE); narrate the mechanism of action of RF and technical tips to prevent thermal damage.
CASE REPORTS
1. Case 1
A 72-year-old male patient presented with bilateral lower limb pain associated with numbness; right (RT) more than left (LT) involving L5 dermatomal distribution with Numerical Rating Scale (NRS) pain score of 6. Patient presented to us with these complaints after he underwent RT UBE L4–5 for lateral recess and central stenosis decompression at private hospital. After through history and clinical examination, neurological examination revealed normal motor power in both lower limbs, and hyperesthesia and paresthesia in L5 dermatome on LT lower limb with hyporeflexia (1+) at ankle and knee on LT side. Imaging in the form of magnetic resonance imaging (MRI) and computed tomography revealed no compressive elements at the index level (Figure 1). As MRI did not reveal any pathology, electromyography (EMG) showed left S1 radiculopathy, preganglionic lesion, complete axonotmesis and chronic L5 radiculopathy (partial but severe). Patient did not receive any root blocks, was on oral anticonvulsant medication and NRS was 3 at end of 3-month follow-up.
Axial magnetic resonance imaging at L4–5, demonstrating right laminotomy (red circle) (A) and hyperintensity (B) in the posterior musculature on the right side, suggestive of postoperative changes (red arrow).
2. Case 2
A 77-year-old man presented with a past surgical history of UBE for L4–5 for canal and lateral recess stenosis with lower extremities tingling and feeling numbness, gait disturbances with recent onset symptom worsening 17 months later. Patient had undergone UBE LT L4–5 laminectomy approach at peripheral centre. On neurological examination, hypoesthesia in L4, L5, and S1 dermatome LT > RT, grade V motor power in both lower limbs. Imaging revealed no neural compromise at operated level or no definite lesion related to patient clinical symptom (Figure 2). EMG revealed finding compatible with bilateral lower lumbosacral radiculopathy mainly involving L5 and S1 nerve root. In view of persistence symptoms, intervention in the form of transforaminal epidural steroid was planned. Post procedure his NRS was 1.
(A) Axial magnetic resonance imaging at L4–5, demonstrating left laminotomy and a resected inferior facet with hyperintensity in the posterior musculature on the left side, suggestive of postoperative changes (white arrow). (B) Axial computed tomography at L4–5, showing the laminotomy site and the resected inferior facet (black circle).
3. Case 3
A 68-year-old man with history of LT UBE and decompression for L4–5 lateral recess and canal stenosis (Figure 3). Postsurgery he presented to our centre with complaints of persisting varying degree of pain in RT leg in addition he also had RT buttock pain and sense of coldness in her RT lower limb and also needs socks even in summer which was reported only after surgery. On examination, no positive findings were recorded, however his pain score was 30 on numeric pain rating scale. EMG revealed no abnormality. Root block was considered due persistence of symptoms and reports transient resolution of her symptoms.
(A) Axial magnetic resonance imaging at L4–5, showing hyperintensity in the posterior musculature, suggestive of postoperative changes (yellow arrow). (B) Axial computed tomography at L4–5 showing laminotomy site and resected inferior facet on left side (yellow circle).
All 3 patients had undergone UBE at the different private centres and later transferred to the university hospital for further management
All participants were fully informed regarding study participation and provided written informed consent.
DISCUSSION
RF ablation is an effective therapeutic option for various soft tissue and bony neoplasm and has been increasingly used in setting of ESS in recent past. Arsonval D in 1981 first reported that RF wave passes through when there is rise in local temperature [2]. One year later, it was introduced into clinical practice in form of bovie knife which used RF current for cutting and cauterising tissues [2]. Radio frequency waves, microwaves, infrared radiation, ultraviolet radiation, x-rays and γ-rays are forms of electromagnetic spectrum in increasing frequency. Frequency of RF energy ranges between 3 Hz and 300 GHz. RF energy frequency varying between 400 and 500 kHz is applied in continuous sinusoidal waveform in clinical setting. The current flows into tissue from the RF is through the electrode’s active tip (which is uninsulated) and causes oscillation of ions such as sodium, chloride, and potassium at a frequency between 400 and 500 kHz. This swift ionic flow leads to friction, consequently resulting in heating with coagulation and necrosis as final result. This formed heat is primarily generated in the tissue around the electrode’s active tip and is conducted firstly to the cannula lumen (inward) and later creating concentric tissue lesions of lower temperature as the distance increases [3]. The thermal effect generated not only leads to the tissue being incised, ablated and dissected, but also promotes haemostasis and has advantages in comparison with traditional scalpels, RF facilitates rapid tissue dissection and blood less dissection [4,5] which has led to tremendous usage in ESS. However, the other important concern is damage to neural structures is the most significant and serious complication of RF usage [6-8]. Spinal nerve root might come in contact with the tip during ablation and possibly damage to the root, resulting from electrical shock, thermal damage, or mechanical stimulation [9] and other factor would be due to undue pressure exerted by RF probe while dissecting, coagulation because any undue exertion of pressure in operative field by RF generates heat which not only damages the underneath structures but also heat that gets transmitted to surrounding structures may cause additional thermal damage which would likely to explain the theory behind non dermatomal dysesthesia as described in our case reports. Thermal injury in UBE is by 2 mechanisms, direct injuries from direct contact of neural structures from RF tip after applying heat and indirect heat damage to the neural structures is caused by raised temperature of the working or epidural space after using RF [10]. Although RF can perform soft tissue dissection, coagulation and ablation, the greatest drawback is thermal damage to the surrounding tissue [11,12]. There are some case reports to describing complication of RF, Boss et al. [13] describing thermal damage to genitofemoral nerve following RF ablation of renal cell carcinoma and irreversible spinal nerve injury from dorsal ramus RF neurotomy by Abbott et al. [14]. Reports of discomfort in the area of the incision, numbness, and leg weakness following nonendoscopic discectomy have been reported [15,16].
There are different kinds of RF probes based on the manufacturing company, having adequate knowledge on probe design, adapting the proper handling techniques reduces the harmful effects and reduces the complications rates.
Surgi-Max (Elliquence, Baldwin, NY, USA) of RF probes uses higher frequency 1.7 MHz with different modulations and biophysical properties that has been introduced by Hellinger et al. [17], this higher frequency helps in reduced heat and minimises tissue alteration.
Several parameters like choice of generators and probe type—90° RF probe, steerable RF probe, curved, straight, slope bevel, hook, ball (Figure 4) probe surface diameter, current settings on the generator, mode (coagulation or ablation), frequency, duration of coagulation influence the thermal effect generated on neural tissue that surgeons can control and lastly whether 30° or 0° scope used for visualisation should be taken into account as field as vision varies with different endoscope angles.
FDifferent types of radiofrequency probes and coagulators. (A) Steerable. (B) 90 degrees. (C) Bevel. (D) Curved.
The Surgi-Max Ultra RF Generator (Elliquence) emits energy at the optimum frequency for Spinal Endoscopy through its Trigger-Flex bipolar probe. The Surgi-Max generator offers a choice of modalities for different soft tissue modulation, including coagulation and ablation. Elliquence technology reduces the risk of thermal injuries by providing a localized tissue effect, and surgeons can control the duration and power setting of the energy. Elliquence offers multiple models of Trigger-Flex Bipolar Forceps with different tips and sizes, tailored to each approach for optimum performance.
There are several manufactures recommending RF parameters, Cosman explains that RF could increase the temperature of the targeted tissue above 45°C–50°C and exposure for 20 seconds or more at these high temperatures is lethal to cells [18].
Tips to prevent thermal induced nerve damage by RF probe.
(1) Continuous saline irrigation with working portal prevents rise in epidural temperature.
(2) Firm adequate control and positioning of the electrode tip especially in epidural space and near neural structures.
(3) Holding the RF probe in upright position to reduce contact area and preventing inclination in any angle to prevent contact of tissue in surrounding area (Figure 5).
Methods of using a radiofrequency probe. (A) Correct method. (B) Incorrect method.
(4) Intermittent small bursts low power of coagulation/ablation rather than continuous prolonged duration.
(5) Avoid undue pressure on the tissue to be coagulated or dissected.
(6) Clearing the blood clots and necrotic tissue before using RF, so need of good saline irrigation is required.
(7) Perform RF only when, RF probe tip is in contact with the tissue to dealt.
(8) Bleeding around the dura – steerable probe is to used (recommended 10 W) [10].
(9) Ablation mode is used for initial soft use dissection, haemostasis (recommended 60 W) [10].
(10) Coagulation mode is recommended, after dural exposure as ablation mode generates excess heat [10].
The RF energy parameters recommended (based on the Arthrocare RF device) the area above the bone (ablation mode 7 and coagulation mode 2), around epidural space (ablation mode 3 and coagulation mode 1) and near the dura only coagulation (coagulation mode 1) is recommended [19].
RF should be performed at adequate voltage and in proper direction; posterior end of RF probe should be directed against nerve root so that discharge RF current is away from the neural structure not directly on it.
To date, RF, which is used in UBE/biportal endoscopic spinal surgery, has been used in arthroscopic joint surgeries which has fewer neural structure in operative field, so it is necessary to develop RF specialized with the validation of safety for endoscopic spinal surgery to reduce the complications associated with RF.
Postoperative dysesthesia resolves over a period of 3 to 4 months and in some cases, root blocks and use on anticonvulsants can be helpful.
CONCLUSION
The RF bipolar is an excellent tool for simultaneous dissection of soft tissue and haemostasis in ESS. Appropriate usage should adhere to low power; short duration with saline irrigation with adequate inflow and out flow patency can prevent any neural structure damage.
Notes
Conflict of Interest
JSK, a member of the Editorial Board of Journal of Minimally Invasive Spine Surgery & Technique, is the corresponding author of this article. However, he played no role whatsoever in the editorial evaluation of this article or the decision to publish it. Author has no conflict of interest to declare.
Funding/Support
This study received no specific grant from any funding agency in the public, commercial, or not-for-profit sectors.