Objective outcome measures may demonstrate continued change in functional recovery in patients with ceiling effects of subjective patient-reported outcome measures after surgery for lumbar degenerative disorders

BACKGROUND CONTEXT

The 6-minute walking test (6WT) has been previously shown to be a reliable and valid outcome measure. It is unclear if the 6WT may further help to detect differences in well performing patients that reach a ceiling effect in PROMs after surgery.

PURPOSE

To evaluate changes and timing of change in objective functional impairment (OFI) as measured with the smartphone-based 6WT in relation to patient-reported outcome measures (PROMs) after surgery for degenerative lumbar disorders (DLD).

STUDY DESIGN

Prospective observational cohort study.

PATIENT SAMPLE

Fifty consecutive patients undergoing surgery for DLD.

OUTCOME MEASURES

Patients self-determined their OFI using the 6WT application (6WT-app) and completed a set of paper-based PROMs before, 6 weeks and 3 months after surgery.

METHODS

Fifty patients undergoing surgery for DLD were assessed preoperatively (baseline), 6 weeks (6W) and 3 months (3M) postoperatively. Paired sample t-tests were used to establish significant changes in raw 6-minute walking distance (6WD) and standardized Z-scores, as well as PROMs. Pearson correlation coefficient was used to define the relationship between 6WT and PROMs. Floor and ceiling effects were assessed for each PROM (visual analogue scale [VAS], core outcome measure index [COMI], Zurich claudication questionnaire [ZCQ]).

RESULTS

Mean 6WT results improved from 377 m (standard deviation - SD 137; Z-score: 1.8, SD 1.8) to 490 m (SD 126; -0.7, SD 1.5) and 518 m (SD 112; -0.4, SD 1.41; all p<.05) at 6W and 3M follow-up. No significant improvement was observed between 6W and 3M for the ZCQ, VAS back and leg pain. While correlation between 6WT and all PROMs were weak at baseline, correlation coefficient increased to moderate at 3M. A considerable ceiling effect (best possible score) was observed, most notably for the ZCQ physical performance, VAS back and leg pain in 24%, 20%, and 16% of patient at 6W and in 30%, 24%, and 28% at 3M.

CONCLUSIONS

Objective functional tests can describe the continued change in the physical recovery of a patient and may help to detect differences in well performing groups as well as in cases where patients' PROM results cannot further improve because of a ceiling effect.

Inguinal hernia treatment in Switzerland: inpatient vs. outpatient setting - HerStAmb Study (prospective observational two-centre comparative study)

PURPOSE

Since 01/2018, AVOS (ambulant vor stationär = outpatient to inpatient) regulation has been progressively implemented in hernia surgery in Switzerland. The aim of this prospective, observational, two-centre comparative study was to compare the outcome of outpatient and inpatient post-operative care in terms of AVOS by examining the re-admission rate, complication rate and quality of life in patients with primary unilateral inguinal hernia repair.

METHODS

The study ran between 01/2019 and 04/2020 and included 237 patients with a primary unilateral inguinal hernia. Treatment setting was decided according to AVOS guidelines. Primary endpoint was re-admission rate within 6 weeks postoperatively. Secondary endpoints were the complication rate and patient outcome (quality of life) at 6 weeks follow-up postoperatively, as measured by the Short Form 36 Health Survey Questionnaire (SF-36).

RESULTS

Complications occurred in 11 (14%) inpatient patients, but none required re-admitting for revision until follow-up at 6 weeks after discharge. In the outpatient group, there were 27 (17%) complications reported, while 6 (4%) of these patients crossed over to the inpatient group immediately after surgery. None of the other complications required re-admission until follow-up at 6 weeks. No significant relationship between treatment setting and number of complications/re-admission rate (p=0.458, p=0.061) was observed. The mean outcome (SF-36) between the treatment groups was not significantly different (p=0.16-0.856).

CONCLUSION

In terms of AVOS selection criteria in Switzerland, primary unilateral inguinal hernia can be safely treated in both treatment settings. Re-admission rates, complications and quality of life do not significantly differ. Day surgery in terms of AVOS might be as effective and efficient, both from the patient's perspective and that of the institution.

TRIAL REGISTRATION NUMBER

NCT05234242.

Casemix, management, and mortality of patients rreseceiving emergency neurosurgery for traumatic brain injury in the Global Neurotrauma Outcomes Study: a prospective observational cohort study

BACKGROUND

Traumatic brain injury (TBI) is increasingly recognised as being responsible for a substantial proportion of the global burden of disease. Neurosurgical interventions are an important aspect of care for patients with TBI, but there is little epidemiological data available on this patient population. We aimed to characterise differences in casemix, management, and mortality of patients receiving emergency neurosurgery for TBI across different levels of human development.

METHODS

We did a prospective observational cohort study of consecutive patients with TBI undergoing emergency neurosurgery, in a convenience sample of hospitals identified by open invitation, through international and regional scientific societies and meetings, individual contacts, and social media. Patients receiving emergency neurosurgery for TBI in each hospital's 30-day study period were all eligible for inclusion, with the exception of patients undergoing insertion of an intracranial pressure monitor only, ventriculostomy placement only, or a procedure for drainage of a chronic subdural haematoma. The primary outcome was mortality at 14 days postoperatively (or last point of observation if the patient was discharged before this time point). Countries were stratified according to their Human Development Index (HDI)-a composite of life expectancy, education, and income measures-into very high HDI, high HDI, medium HDI, and low HDI tiers. Mixed effects logistic regression was used to examine the effect of HDI on mortality while accounting for and quantifying between-hospital and between-country variation.

FINDINGS

Our study included 1635 records from 159 hospitals in 57 countries, collected between Nov 1, 2018, and Jan 31, 2020. 328 (20%) records were from countries in the very high HDI tier, 539 (33%) from countries in the high HDI tier, 614 (38%) from countries in the medium HDI tier, and 154 (9%) from countries in the low HDI tier. The median age was 35 years (IQR 24-51), with the oldest patients in the very high HDI tier (median 54 years, IQR 34-69) and the youngest in the low HDI tier (median 28 years, IQR 20-38). The most common procedures were elevation of a depressed skull fracture in the low HDI tier (69 [45%]), evacuation of a supratentorial extradural haematoma in the medium HDI tier (189 [31%]) and high HDI tier (173 [32%]), and evacuation of a supratentorial acute subdural haematoma in the very high HDI tier (155 [47%]). Median time from injury to surgery was 13 h (IQR 6-32). Overall mortality was 18% (299 of 1635). After adjustment for casemix, the odds of mortality were greater in the medium HDI tier (odds ratio [OR] 2·84, 95% CI 1·55-5·2) and high HDI tier (2·26, 1·23-4·15), but not the low HDI tier (1·66, 0·61-4·46), relative to the very high HDI tier. There was significant between-hospital variation in mortality (median OR 2·04, 95% CI 1·17-2·49).

INTERPRETATION

Patients receiving emergency neurosurgery for TBI differed considerably in their admission characteristics and management across human development settings. Level of human development was associated with mortality. Substantial opportunities to improve care globally were identified, including reducing delays to surgery. Between-hospital variation in mortality suggests changes at an institutional level could influence outcome and comparative effectiveness research could identify best practices.

FUNDING

National Institute for Health Research Global Health Research Group.

Distance to first symptoms measured by the 6-min walking test differentiates between treatment success and failure in patients with degenerative lumbar disorders

PURPOSE

The smartphone-based 6-min walking test (6WT) is an established digital outcome measure in patients undergoing surgery for degenerative lumbar disorders (DLD). In addition to the 6WTs primary outcome measure, the 6-min walking distance (6WD), the patient's distance to first symptoms (DTFS) and time to first symptoms (TTFS) can be recorded. This is the first study to analyse the psychometric properties of the DTFS and TTFS.

METHODS

Forty-nine consecutive patients (55 ± 15.8 years) completed the 6WT pre- and 6 weeks (W6) postoperative. DTFS and TTFS were assessed for reliability and content validity using disease-specific patient-reported outcome measures. The Zurich Claudication Questionnaire patient satisfaction subscale was used as external criterion for treatment success. Internal and external responsiveness for both measures at W6 was evaluated.

RESULTS

There was a significant improvement in DTFS and TTFS from baseline to W6 (p < 0.001). Both measures demonstrated a good test-retest reliability (β = 0.86, 95% CI 0.81-0.90 and β = 0.83, 95% CI 0.76-0.87, both p < 0.001). The DTFS exceeded the 6WD capability to differentiate between satisfied (82%) and unsatisfied patients (18%) with an AUC of 0.75 (95% CI 0.53-0.98) vs. 0.70 (95% CI 0.52-0.90). The TTFS did not demonstrate meaningful discriminative abilities.

CONCLUSION

Change in DTFS can differentiate between satisfied and unsatisfied patients after spine surgery. Digital outcome measures on the 6WT metric provide spine surgeons and researchers with a mean to assess their patient's functional disability and response to surgical treatment in DLD.

External Validation of the Minimum Clinically Important Difference in the Timed-up-and-go Test After Surgery for Lumbar Degenerative Disc Disease

STUDY DESIGN

Prospective observational cohort study.

OBJECTIVE

The aim of this study was to provide external validation of the minimum clinically important difference (MCID) of the Timed-up-and-go (TUG) test.

SUMMARY OF BACKGROUND DATA

The TUG test is one of the best explored and most frequently applied objective task-based functional outcome measure in patients with lumbar degenerative disc disease (DDD). The increased use of the TUG test is based on its solid psychometric properties; however, an external validation of the originally determined MCID is lacking.

METHODS

Forty-nine patients with lumbar DDD, scheduled for elective spine surgery, were assessed pre- and 6-weeks (W6) postoperative. MCID values were calculate for raw TUG test times (seconds) and standardized TUG z scores using three different computation methods and the following established patient-reported outcome measures (PROMs) as anchors: Visual Analog Scales (VAS), Core Outcome Measures Index Back, Zurich Claudication Questionnaire (ZCQ).

RESULTS

The three computation methods generated a range of MCID values, depending on the PROM used as anchor, from 0.9 s (z score of 0.3) based on the VAS leg pain to 3.0 seconds (z score of 2.7) based on the ZCQ physical function scale. The average MCID of the TUG test across all anchors and computation methods was 2.1 s (z score of 1.5). According to the average MCID of raw TUG test values or TUG z scores, 41% and 43% of patients classified as W6 responders to surgery, respectively.

CONCLUSION

This study confirms the ordinally reported TUG MCID values in patients undergoing surgery for lumbar. A TUG test time change of 2.1 seconds (or TUG z score change of 1.5) indicates an objective and clinically meaningful change in functional status. This report facilitates the interpretation of TUG test results in clinical routine as well as in research.Level of Evidence: 3.

Smartphone-based real-life activity data for physical performance outcome in comparison to conventional subjective and objective outcome measures after degenerative lumbar spine surgery

Introduction

Outcome assessments after surgery for degenerative lumbar disorders (DLDs) rely on subjective patient-reported outcomes (PROMs). New objective functional capacity tests, like the smartphone-based 6-min walking test (6WT), have been introduced but presumably also do not reflect the patient's real-life functional performance.

Research question

Pilot study to analyze changes in smartphone-based real-life activity data for physical performance outcome in patients undergoing surgery for DLD.

Material and methods

Prospective observational study of DLD patients. Objective functional capacity and subjective outcomes were measured using 6WT and PROMs. Real-life physical performance data were acquired retrospectively using Apple iPhone Health data and compared against objective capacity and subjective outcomes.

Results

Eight patients (mean 46 years, 62% male) provided 286.858 smartphone mile counts. PROMs and physical capacity (6WT) significantly improved postoperatively. 6WT results increased from 352m pre-to 555/567m at 6/12 weeks postoperatively (p ​= ​0.03). For physical performance a linear mixed effect models showed an increase in daily distance in the first 4 months after surgery (slope +0.178; p ​< ​0.001). However, those increases reversed from 4 until 12 months postoperatively (negative slope estimate of −0.076; p ​< ​0.001). Smartphone-derived physical performance measures showed a positive correlation with corresponding physical capacity in the 6WT (R ​= ​0.57,p ​= ​0.004) and negative correlations with PROMs (COMI: R ​= ​−0.62p ​= ​0.001; ZCQ-Physical-Function: R ​= ​−0.68,p ​< ​0.001; ZCQ-Symptom-Severity: R ​= ​−0.52,p ​= ​0.009).

Discussion and conclusion

Smartphone-based real-life activity data allows for longitudinal physical performance assessment. Physical performance correlated with physical capacity and patient's subjective perception of disability. However, physical performance may be more resistant to postoperative longtime change which should consult a more cautious use as objective outcome measure.

•

Smartphone-based activity data allows for continuous longitudinal physical performance assessment after lumbar spine surgery.

•

It captures both, a preoperative deterioration, and a postoperative improvement of patients' physical performance.

•

Although smartphone-based performance correlated with physical capacity/PROMs, daily activity decreased again postoperatively

•

This discrepancy indicates that smartphone-based performance may provide a more in-depth assessment of function over time.

Spondylodiscitis due to anaerobic bacteria Veillonella parvula: Case report and literature review

Background:

While pyogenic spondylodiscitis due to Gram-positive aerobic bacteria and its treatment is well known, spondylodiscitis caused by anaerobic Gram-negative pathogen is rare. In particular, the spondylodiscitis caused by Veillonella species is an absolute rarity. Thus no established management recommendations exist.

Case Description:

A case report of a 79-year-old man with spondylodiscitis caused by Veillonella parvula with intramuscular abscess collection managed conservatively with stand-alone antibiotic therapy without a spinal stabilization procedure. A review of literature of all reported spondylodiscitis caused by Veillonella species was performed. After 3 week-intravenous therapy with the ceftriaxone in combination with the metronidazole followed by 3 weeks per oral therapy with amoxicillin/clavulanate, the complete recovery of the patient with the V. parvula infection was achieved.

Conclusion:

Treatment of the spondylodiscitis caused by Veillonella species should contain a beta-lactam with beta-lactamase inhibitor or third-generation cephalosporine. Six weeks of treatment seem to be sufficient for the complete recovery of the patient.

Responsiveness of the self-measured 6-minute walking test and the Timed Up and Go test in patients with degenerative lumbar disorders

OBJECTIVE

The 6-minute walking test (6WT) and the Timed Up and Go (TUG) test are two of the most commonly applied standardized measures of objective functional impairment that help support clinical decision-making for patients undergoing surgery for degenerative lumbar disorders. This study correlates smartphone-app-based 6WT and TUG results to evaluate their responsiveness.

METHODS

In a prospective study, 49 consecutive patients were assessed preoperatively and 6 weeks postoperatively using the 6WT, the TUG test, and commonly used patient-reported outcome measures. Raw values and standardized z-scores of both objective tests were correlated. An external criterion for treatment success was created based on the Zurich Claudication Questionnaire patient satisfaction subscale. Internal and external responsiveness for both functional tests was evaluated.

RESULTS

The mean preoperative 6WT results improved from 401 m (SD 129 m), z-score -1.65 (SD 1.6) to 495 m (SD 129 m), z-score -0.71 (SD 1.6, p < 0.001). The mean preoperative TUG test results improved from 10.44 seconds (SD 4.37, z-score: -3.22) to 8.47 seconds (SD 3.38, z-score: -1.93, p < 0.001). The 6WT showed a strong negative correlation with TUG test results (r = -66, 95% CI 0.76-0.53, p < 0.001). The 6WT showed higher internal responsiveness (standardized responsive mean = 0.86) compared to the TUG test (standardized responsive mean = 0.67). Evaluation of external responsiveness revealed that the 6WT was capable of differentiating between patients who were satisfied and those who were unsatisfied with their treatment results (area under the curve = 0.70), whereas this was not evident for the TUG test ( area under the curve = 0.53).

CONCLUSIONS

Both tests adequately quantified functional impairment in surgical candidates with degenerative lumbar disorders. The 6WT demonstrated better internal and external responsiveness compared with the TUG test. Clinical trial registration no.: NCT03977961 (clinicaltrials.gov).

ABBREVIATIONS

AUC = area under the curve; COMI = Core Outcome Measures Index; DLDs = degenerative lumbar disorders; LDH = lumbar disc herniation; LSS = lumbar spinal stenosis; PROM = patient-reported outcome measure; ROC = receiver operating characteristic; SRM = standardized responsive mean; TUG = Timed Up and Go; VAS = visual analog scale; 6WD = 6-minute walking distance; 6WT = 6-minute walking test; ZCQ = Zurich Claudication Questionnaire.

External Validation of the Timed Up and Go Test as Measure of Objective Functional Impairment in Patients With Lumbar Degenerative Disc Disease

BACKGROUND

The Timed Up and Go (TUG) test is the most commonly applied objective measure of functional impairment in patients with lumbar degenerative disc disease (DDD).

OBJECTIVE

To demonstrate external content validity of the TUG test.

METHODS

Consecutive adult patients, scheduled for elective lumbar spine surgery, were screened for enrollment into a prospective observational study. Disease severity was estimated by patient-reported outcome measures (PROMs; Visual Analog Scales [VAS], Core Outcome Measures Index [COMI] back, Zurich Claudication Questionnaire [ZCQ]) and the TUG test. Pearson correlation coefficients (PCCs) were used to describe the relationship between logarithmic TUG test raw values and PROMs.

RESULTS

A total of 70 patients (mean age 55.9 ± 15.4 yr; 38.6% female; 27.1% previous spine surgery; 28.6% lower extremity motor deficits) with lumbar disc herniation (50%), lumbar spinal stenosis (34.3%), or instability requiring spinal fusion (15.7%) were included. The mean TUG test time was 10.8 ± 4.4 s; age- and sex-adjusted objective functional impairment (OFI) T-score was 134.2 ± 36.9. A total of 12 (17.1%) patients had mild, 14 (20%) moderate, and 9 (12.9%) severe OFI, while 35 (50%) had TUG test results within the normal population range (no OFI). PCCs between TUG test time and VAS back pain were r = 0.37 (P = .002), VAS leg pain r = 0.37 (P = .002), COMI back r = 0.50 (P < .001), ZCQ symptom severity r = 0.41 (P < .001), and ZCQ physical function r = 0.36 (P = .002).

CONCLUSION

This external validation demonstrated similar OFI rates and PCCs between logarithmic TUG test results and PROMs compared to the original article from 2016. These findings support the TUG test being a quick, easy-to-use objective test, which provides the physician with a robust estimate of pain and functional impairment.

Patients undergoing surgery for lumbar degenerative spinal disorders favor smartphone-based objective self-assessment over paper-based patient-reported outcome measures

BACKGROUND CONTEXT

Smartphone-based applications enable new prospects to monitor symptoms and assess functional outcome in patients with lumbar degenerative spinal disorders. However, little is known regarding patient acceptance and preference towards new modes of digital objective outcome assessment.

PURPOSE

To assess patient preference of an objective smartphone-based outcome measure compared to conventional paper-based subjective methods of outcome assessment.

STUDY DESIGN

Prospective observational cohort study.

PATIENT SAMPLE

Fourty-nine consecutive patients undergoing surgery for lumbar degenerative spinal disorder.

OUTCOME MEASURES

Patients completed a preference survey to assess different methods of outcome assessment. A 5-level Likert scale ranged from strong disagreement (2 points) over neutral (6 points) to strong agreement (10 points) was used.

METHODS

Patients self-determined their objective functional impairment using the 6-minute Walking Test application (6WT-app) and completed a set of paper-based patient-reported outcome measures (PROMs) before and 6 weeks after surgery. Patients were then asked to rate the methods of outcome assessment in terms of suitability, convenience, and responsiveness to their symptoms.

RESULTS

The majority of patients considered the 6WT-app a suitable instrument (median 8.0, interquartile range [IQR] 4.0). Patients found the 6WT more convenient (median 10.0, IQR 2.0) than the Zurich Claudication Questionnaire (ZCQ; median 8.0, IQR 4.0, p=.019) and Core Outcome Measure Index (COMI; median 8.0, IQR 4.0, p=.007). There was good agreement that the 6WT-app detects change in physical performance (8.0, IQR 4.0). 78 % of patients considered the 6WT superior in detecting differences in symptoms (vs. 22% for PROMs). Seventy-six percent of patients would select the 6WT over the other, 18% the ZCQ and 6% the COMI. Eighty-two percent of patients indicated their preference to use a smartphone app for the assessment and monitoring of their spine-related symptoms in the future.

CONCLUSIONS

Patients included in this study favored the smartphone-based evaluation of objective functional impairment over paper-based PROMs. Involving patients more actively by means of digital technology may increase patient compliance and satisfaction as well as diagnostic accuracy.

Evaluation of the 6-minute walking test as a smartphone app-based self-measurement of objective functional impairment in patients with lumbar degenerative disc disease

OBJECTIVE

Digital transformation enables new possibilities to assess objective functional impairment (OFI) in patients with lumbar degenerative disc disease (DDD). This study examines the psychometric properties of an app-based 6-minute walking test (6WT) and determines OFI in patients with lumbar DDD.

METHODS

The maximum 6-minute walking distance (6WD) was determined in patients with lumbar DDD. The results were expressed as raw 6WDs (in meters), as well as in standardized z-scores referenced to age- and sex-specific values of spine-healthy volunteers. The 6WT results were assessed for reliability and content validity using established disease-specific patient-reported outcome measures.

RESULTS

Seventy consecutive patients and 330 volunteers were enrolled. The mean 6WD was 370 m (SD 137 m) in patients with lumbar DDD. Significant correlations between 6WD and the Core Outcome Measures Index for the back (r = −0.31), Zurich Claudication Questionnaire (ZCQ) symptom severity (r = −0.32), ZCQ physical function (r = −0.33), visual analog scale (VAS) for back pain (r = −0.42), and VAS for leg pain (r = −0.32) were observed (all p < 0.05). The 6WT revealed good test-retest reliability (intraclass correlation coefficient 0.82), and the standard error of measurement was 58.3 m. A 4-tier severity stratification classified patients with z-scores > −1 (no OFI), −1 to −1.9 (mild OFI), −2 to −2.9 (moderate OFI), and ≤ −3 (severe OFI).

CONCLUSIONS

The smartphone app-based self-measurement of the 6WT is a convenient, reliable, and valid way to determine OFI in patients with lumbar DDD. The 6WT app facilitates the digital evaluation and monitoring of patients with lumbar DDD.

Longitudinal smartphone-based self-assessment of objective functional impairment in patients undergoing surgery for lumbar degenerative disc disease: initial experience

BACKGROUND

The worldwide spread of smartphone usage enables new possibilities for longitudinal monitoring of objective functional impairment (OFI) in patients undergoing surgery for lumbar degenerative disc disease (DDD).

METHODS

Three patients, undergoing elective surgery for lumbar DDD, self-assessed OFI using a recently validated 6-min walking test (6WT) smartphone application. Results are presented as raw 6-min walking distance (6WD) as well as in reference to age- and sex-specific healthy population reference values using standardized z-scores (number of standard deviations). In parallel, patient-reported outcome measures (PROMs), including numeric rating scale (NRS) leg-pain and Core Outcome Measures Index (COMI) were obtained before (pre) and 6 weeks (6 W) as well as 3 months (3 M) after surgery. Descriptive analyses were used to compare PROMs with repeated 6WT measurements over time. The feasibility and benefits of the longitudinal OFI measurements using the 6WT app are discussed.

RESULTS

One patient presented a favorable outcome, reflected by a clinically meaningful improvement in PROMs. Correspondingly, the 6WT distance gradually improved above the normal population values ((pre 399 m (z-score - 1.96) vs. 6 W 494 m (- 0.85) vs. 3 M 557 m (- 0.1)). One patient experienced initial improvement at 6 W, followed by a decline in 6WD at 3 M which promoted further interventions with subsequent recovery ((358 m (z-score - 3.29) vs 440 m (- 2.2) vs 431 m (- 2.32) vs 471 m (- 1.78)). The last patient showed a lack of improvement in PROMs as well as in OFI (360 m (z-score 0.0) vs 401 m (0.30) vs 345 m (- 0.11)) resulting in secondary surgery.

CONCLUSION

The longitudinal assessment of OFI using the 6WT app was feasible and provided the physician with a detailed history of patients' postoperative walking capacity complementing commonly used PROMs.

Smartphone-Based Self-Assessment of Objective Functional Impairment (6-Minute Walking Test) in Patients Undergoing Epidural Steroid Injection

Epidural steroid injection (ESI) represents a popular treatment option in patients with lumbar degenerative disc disease (DDD). The main objective of the article was to determine whether the 6-minute walking test (6WT) could assist in the discrimination between ESI responders and nonresponders. We used a validated 6WT smartphone application to assess self-measured objective functional impairment (OFI) in 3 patients with DDD undergoing ESI. Patient-reported outcome measures (PROMs), including the Core Outcome Measures Index and the Oswestry Disability Index, were obtained at baseline and at the 3-, 7-, and 28-day follow-up. Descriptive analyses were used to compare PROMs with OFI over time. Two patients responded well to the ESI, illustrated by clinically meaningful improvements in PROMs. This improvement was accompanied by a substantial increase in the 6WT distance (case I: 358 m vs. 517 m and case II: 296 m vs. 625 m). One patient reported only moderate improvement in leg pain and conflicting results in the other PROMs. The 6WT demonstrated a persistent OFI (487 m vs. 488 m). This patient was considered a nonresponder and underwent surgical treatment. This case series illustrates the feasibility of the smartphone-based 6WT as a tool to assess OFI in patients undergoing ESI for lumbar DDD.