2.3 Outcome measurement
Patient demographics (age, sex, body mass index [BMI], and coexisting disease, including hypertension and/or diabetes mellitus) and other clinical data, such as pain characteristics, including its duration and severity, and concurrent medications, were obtained from medical record reviews and patient-based outcome questionnaires or telephonic interviews. The severity of LFSS on MRI was shown with perineural fat obliteration or nerve root collapse based on the practical grading system for lumbar foraminal stenosis reported by Lee et al, where grade 0 refers to the absence of foraminal stenosis; grade 1 refers to mild foraminal stenosis showing perineural fat obliteration in 2 opposing directions, vertical or transverse; grade 2 refers to moderate foraminal stenosis showing perineural fat obliteration in 4 directions without morphologic changes, both vertical and transverse directions; and grade 3 refers to severe foraminal stenosis showing nerve root collapse or morphologic changes. In addition, we collected procedure-related information, such as the level and side of operation.
The patients’ pain severity was assessed using an NRS pain score with 0 as the lowest score (no pain at all) and 10 as the highest score (unbearable pain). Functional status was assessed using the Korean version of the 9-item Oswestry Disability Index (ODI; range from 0 to 100, where 0 means no disability). Patient satisfaction was also assessed using a 5-point Likert scale (1 = extremely dissatisfied; 2 = somewhat dissatisfied; 3 = neutral; 4 = somewhat satisfied; and 5 = extremely satisfied). In addition, the patient's symptoms were evaluated. The time of walking without radicular pain was assessed by asking “How long can you walk without having to stop to rest due to your leg pain?” via a questionnaire. At the 3-month follow-up, the patients completed questionnaires that reflected their functional status and pain intensity.
Regarding safety, complications that occurred within 3 months after the procedure were reviewed either in person or by telephone. Any complications that occurred after the procedure (motor weakness of the lower legs, sensory change, infection, etc) were recorded.
2.4 Statistical analysis
Preprocedural and postprocedural NRS pain scores, ODI, and duration of walking without radicular pain, and changes in NRS pain score (%), ODI (%), and duration of walking without radicular pain between baseline and the 3-month follow-up visit were analyzed with the Wilcoxon signed-rank test. Outcomes are shown as mean (interquartile range [IQR]), or frequency (%), as appropriate. We assessed the proportion of successful responders, defined as at least 50% decrease in the NRS pain score, accompanied by improvement in the ODI (%) and duration of walking, by the 3-month follow-up visit. Then, differences in outcomes were compared between responders and nonresponders, using the Mann–Whitney test for nonparametric data and Fisher exact test for parametric data.
Statistical analysis was performed using SPSS Statistics version 23.0 for Windows (IBM Corp., Armonk, NY). A P value <.05 was considered statistically significant.
We thoroughly reviewed the medical records of 29 consecutive patients who underwent PLF using the Claudicare; 5 of these patients were excluded due to an absence of MRI within a 3-month period (n = 2) or an unclear history of TFESI before PLF (n = 3). Finally, 24 patients were included in the study. Of these patients, more than a half (n = 15) were classified as successful responders according to the predefined criteria, with the remaining patients (n = 9) classified as nonresponders (Fig. 4).
Demographics and perioperative clinical parameters of all patients, including responders and nonresponders, are summarized in Table 1. The mean age of the patients overall was 67.5 years (IQR 58.3–74.0), and 15 were male and 9 were female. The mean BMI was 25.3 kg/m2 (IQR 23.1–29.4). Procedure levels were at L4-5 in 15 patients and at L5-S1 in 10 patients. Using MRI, grade 1 LFSS (mild foraminal stenosis) was observed in 9 patients, grade 2 (moderate foraminal stenosis) in 6 patients, and grade 3 (severe foraminal stenosis) in 9 patients, based on Lee et al's MRI grading system for LFSS. In addition, 15 patients (62.5%) showed concomitant spondylolisthesis and LFSS at the same level, and 5 (20.8%) had previously undergone open surgery at other levels. The procedures were performed via a left-sided approach in 5 patients, a right-sided approach in 6, and a bilateral approach in 13, based on radiologic findings and clinical symptoms. Seven patients were prescribed a weak opioid, tramadol, and acetaminophen mixture at baseline; there was no statistically significant difference in opioid prescription use between the responder (n = 5) and nonresponder groups (n = 2; P
= .67). None of the patients required strong opioid medication.
Table 2 demonstrates the changes in outcome variables from baseline to the 3-month follow-up. The preoperative and postoperative NRS pain scores at 3 months were 8.0 (IQR 7.0–8.8) and 3.5 (IQR 2.0–6.8), respectively, which represented an overall significant decrease of 41.4% (P
< .001). The ODI also decreased from baseline (34.5; IQR 29.5–43.3) to the 3-month follow-up (27.0; IQR 24.0–34.5) by 13.5%; however, this decrease was not statistically significant (P
= .09). The duration of walking without radicular pain significantly increased from 5.0 minutes (IQR 1.3–5.0) at baseline to 17.5 minutes (IQR 5.0–30.0) at the 3-month follow-up visit (P
The NRS pain score and duration of walking without pain at 3 months were statistically significantly different between the responder and nonresponder groups (P
< .001 and P
= .01, respectively), whereas there was no significant difference in improvement of ODI (%) between the groups (P
= .23). Among the patients overall, however, only 5 patients (20.8%) experienced the reduced weak opioid analgesics; 3 were in the responder group and 2 were in the nonresponder group (P > .99). According to the 5-point Likert scale, 3 months after the procedure, 15 patients (62.5%) reported satisfaction (score of 4 or 5 on the 5-point Likert scale); there was a statistically significant difference between the responders and nonresponders in terms of patient satisfaction (P
All adverse events that occurred during the study period were minor and temporary. One-fourth (25%, n = 6) of patients reported temporary pain during the procedure, but this was tolerable and did not require additional medication or discontinuation of the procedure. Four patients (16.7%) complained of procedure-related pain for 2 to 3 days postprocedurally, but it was spontaneously relieved without any neurological sequelae. There was no report of transient paresthesia in the lower extremity or other adverse events, such as hematoma formation, persistent motor or sensory impairment, severe pain, paresthesia, or infection.
In this study, PLF was performed with a specially designed device, the Claudicare, on an outpatient basis in 24 patients who were diagnosed with LFSS. This relatively simple and easy procedure significantly improved pain intensity and duration of walking without radicular pain in 63% of the patients (n = 15) at the 3-month follow-up visit. All patients were discharged on the day of the procedure without any serious adverse events.
There may be several advantages in using this device for PLF. First, because the largest external diameter of the instrument is as small as 3.5 mm (in the working cannula), it minimizes injury to the nerve and the surrounding tissues during the procedure via a transforaminal approach. Second, the drill is designed with a special tip and a nerve-protecting shield, allowing a physician to grind away the hypertrophied capsule of the SAP and part of the transforaminal ligaments, safely. In addition, as it is driven by a small disposable, portable battery, rather than a large standing power source, the device can be handled conveniently.
Lumbar foraminal spinal stenosis is a major cause of neuropathic low back pain. Hypertrophy of the facet joint, particularly the SAP, and transforaminal ligaments has been suggested to be a common source of LFSS, resulting in reduction of spinal canal and foraminal dimensions and compression of neural elements. A systematic review concluded that there is insufficient evidence to recommend any specific type of treatment for LFSS. Schneider et al showed that a combination of conservative therapy provides greater short-term improvement in symptoms and physical function and walking capacity. However, several different surgical procedures should be considered to treat patients who do not improve with nonoperative therapies. When focusing on the surgical options, decompression, fusion, and minimally invasive procedures are possible treatments. With the recent move toward adopting minimally invasive techniques, TFESI or percutaneous epidural adhesiolysis has been commonly used as the initial step for managing LFSS in daily clinical practice. However, TFESI may not effectively alleviate pain, particularly in cases accompanied by lateral recess stenosis, which is also frequently caused by hypertrophy of the SAP. Furthermore, although percutaneous epidural adhesiolysis has been suggested as an alternative to TFESI, it has not yielded a concretely positive outcome in LFSS patients. As a basic approach for managing LFSS, removal of the hypertrophied capsule and/or ligament by percutaneous endoscopic lumbar foraminotomy has been proposed to enlarge the narrowed lumbar foramen.[30,31] Although several studies have described the efficacy of the endoscopic technique, it involves a steep learning curve for physicians and requires hospitalization for patients, due to the relative invasiveness of the procedure, and poses a risk of procedure-related adverse events. Recently, Lee et al introduced percutaneous lumbar extraforaminotomy to resect the foraminal ligaments around the target nerve by using a specially designed instrument, which may be analogous to the concept of PLF. Lee et al's procedure showed similar efficacy as that achieved in our study; however, in comparison, PLF using the Claudicare device is relatively simple, does not require hospitalization, and is safe, with less procedure-associated pain than extraforaminotomy.
In Lee et al's study, the proportion of successful outcomes (≥50% pain reduction at 3-month follow-up visit after lumbar extraforaminotomy) was 60%, which is similar to the success rate in our study (63%, n = 15). However, we predefined successful outcomes as a combination of improvement in pain intensity and functional ability: at least 50% reduction in pain intensity, with improvement of ODI (%) and duration of walking without radicular pain. Although ODI (%) was not considerably improved, walking duration was significantly increased in the patients overall after the procedure, which suggests that PLF using the Claudicare device may contribute to improving neurogenic claudication in patients with lumbar spinal stenosis. In addition, as compared with the Lee et al's study, the prevalence of adverse events, including temporary pain during the procedure and procedure-related pain in the postprocedural period, was relatively low in this study (65% vs 25% and 45% vs 16.7%, respectively). Furthermore, no transient paresthesia in the lower extremity during the procedure or follow-up period was reported in our patients. Taken together, we deduce that PLF using the Claudicare device may be the optimal option for managing intractable LFSS on a routine outpatient basis.
During the 3-month follow-up period, none of the patients in this study underwent any additional interventional procedures, such as lumbar epidural block, which may have confounded evaluation of the effectiveness of the procedure. However, a major limitation of this study is its nonrandomized, retrospective nature, which may have been affected by characteristic confounders that include bias and variability in the quality of the available information. Furthermore, the small sample size and the short follow-up period are drawbacks in this study. Similar to other minimally invasive procedures, the proficiency of the practitioner may have influenced the outcome in this study. The duration of drilling is not standardized and could be changed by the operator. These factors might have influenced the outcomes of the study. Furthermore, we could not verify an overall reduction of analgesics use in patients, despite the fact that pain intensity and duration of walking without radicular pain were significantly improved at 3 months after the procedure. Nonetheless, out of 7 patients who took weak opioid medications, the majority (n = 5) reported a decrease in their analgesic use at the 3-month follow-up visit. Taken together, appropriately blinded, prospective clinical trials, with an acceptable number of patients monitored over a longer period of time, are warranted to verify our results.
In conclusion, PLF using the Claudicare device could be helpful for improving symptoms from lumbar foraminal stenosis. More than half of the patients in this study (63%) experienced at least 50% or more pain reduction, accompanied by improvement in functions, including the duration of walking without radicular pain by 3 months after the procedure. The prevalence of procedure-related discomfort or adverse events was trivial. Although further clinical evidence should be accumulated, we propose that PLF using the Claudicare device is an advantageous option for managing intractable LFSS on an outpatient basis.
Conceptualization: Sung Eun Sim.
Data curation: Sojeong Yoon, Seok Min Kwon.
Formal analysis: Jee Youn Moon.
Investigation: Yongjae Yoo.
Methodology: Yongjae Yoo, Jee Youn Moon.
Supervision: Jee Youn Moon, Sung Eun Sim.
Writing – original draft: Yongjae Yoo, Jee Youn Moon.
Writing – review & editing: Yongjae Yoo, Jee Youn Moon.
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Keywords:Copyright © 2019 The Authors. Published by Wolters Kluwer Health, Inc. All rights reserved.
claudicare; lumbar foraminal spinal stenosis; neurogenic claudication; percutaneous lumbar foraminoplasty