Objectives To investigate the impact of cryoneurolysis, a minimally invasive percutaneous intervention where secondary axonotmesis is selectively induced through freezing, as a treatment for pain related to knee osteoarthritis in inpatients during the first 16 weeks post upper motor neuron injury. Design This study follows a prospective, observational, longitudinal design. 15 inpatients were enrolled in this study. Treatment involved the freezing of the infrapatellar branches of the saphenous nerve and the branches of the anterior femoral cutaneous nerve. We assessed patients’ active range of motion, maximum passive range of motion (V1), the endpoint reached when moving the limb at its maximal velocity, and tone based on the Modified Ashworth Scale for knee flexion. Pain and functional ability were assessed using the WOMAC. Measurements were taken at baseline, 1 week, 1 month, and 4 months after treatment. Results Total pain score percentage for the knee significantly decreased at all follow-ups relative to baseline. On average, pain scores decreased by 44% between baseline and 1 week, and by 28% between baseline and 4 months. Additionally, knee flexion V1 improved significantly between baseline and 4 months, with a maximum increase of 45 degrees. Conclusions Cryoneurolysis is a novel treatment that can significantly reduce osteoarthritic knee pain in patients with neurological conditions such as stroke and traumatic brain injury during the subacute phase of their injury. It can also significantly increase V1. Together, these increase patient function and enable greater participation in the early stages of rehabilitation, which leads to more complete recoveries. Further studies with larger sample sizes, randomized designs, and longer follow-up durations are required to assess the clinical scope of cryoneurolysis as a treatment for the pain associated with knee osteoarthritis in the subacute phase of upper motor neuron injuries.
Introduction: Osteoarthritis (OA) is a challenging, painful condition that occurs in 33% of stroke survivors. It has been found to increase hospital-based recovery time by 1.6 days for stroke survivors, which greatly increases the demands on the medical system. Moreover, the pain it causes hinders stroke survivors’ participation in rehabilitation, particularly inpatient rehabilitation, which takes place immediately post-stroke, during the subacute phase of their recovery. The disruption of this key window, where rehabilitation can lead to the greatest improvements, can be particularly detrimental. Altogether, OA and stroke combine as comorbidities to lead to greater disability.
The way OA knee pain can hinder stroke recovery underpins the importance of effective pain management in the context of neurological conditions (NCs). Cryoneurolysis, a minimally invasive treatment where secondary axonotmesis is selectively induced via freezing, has been proposed as a treatment for OA knee pain. Its efficacy was supported by a recent multicenter, randomized, double-blind, sham-controlled trial that showed cryoneurolysis to lead to significantly decreased knee pain at 30, 60, and 90 days relative to controls in individuals with OA. However, while this study thoroughly investigated cryoneurolysis as a treatment for OA knee pain, it did not examine this in inpatients with NCs during the subacute phase of their recovery.
This study addresses this gap in the literature through a prospective cohort study of inpatients with comorbidities of knee OA and a NC where knee OA pain was treated using cryoneurolysis during the subacute phase of their recovery.
Methods:
Study
Design:
This single-center prospective longitudinal cohort study follows the STROBE guidelines. Institutional research ethics approval from the local research ethics board was received [H22-00564]. 15 inpatients with knee OA and a NC in the subacute recovery phase were recruited as determined by the examining physician.
Interventional Procedure:
Diagnostic nerve blocks (DNB) targeting sensory nerves at three locations, the infrapatellar branches of the saphenous nerve, and the anterior femoral cutaneous branches, were completed after assessment. Patients were advised to undergo cryoneurolysis to the same targets according to our previously published protocols if the DNB improved pain and range of motion.
Data Review:
Baseline measurements were taken for each patient prior to the cryoneurolysis procedure. Follow-up measurements were taken at 1 week, 1 month, and 4 months. Most patients completed a minimum of two follow-ups. The following measures were taken at baseline and follow-ups: maximum active range of motion (AROM), maximum passive range of motion (V1), Modified Ashworth Scale (MAS), and total pain score percentage and total WOMAC score percentage as calculated using the Western Ontario and McMaster Universities OA Index (WOMAC).
Repeated measures ANOVAs were completed for each measure, with levels being differentiated by time. When indicated, Greenhouse-Geisser corrections were completed for sphericity. When a significant omnibus was found, post hoc tests utilizing Bonferroni corrections were completed. Alpha was set to 0.05.
Results:
Total pain score percentage for the knee significantly decreased at all follow-ups relative to baseline. On average, pain scores decreased by 44% between baseline and 1 week, and by 28% between baseline and 4 months. Additionally, significant improvements were found for knee flexion V1 between baseline and 4 months, with a maximum increase of 45 degrees.
Discussion:
This study demonstrated that cryoneurolysis to the infrapatellar branches of the saphenous nerve and anterior femoral cutaneous branches can lead to significant and meaningful decreases in pain and increases in V1 in neurological injury survivors with knee OA in the subacute stage of recovery.
The positive results regarding pain relief in the inpatient setting align with previous research on cryoneurolysis as a treatment for knee OA. Specifically, a randomized, sham-controlled trial examining the impact of cryoneurolysis on patients with mild-to-moderate knee OA and another randomized control trial examining the impact of preoperative cryoneurolysis on postoperative pain in patients undergoing total knee arthroplasty for severe OA found cryoneurolysis to significantly decrease pain in their respective populations. Furthermore, this study explores the effects of cryoneurolysis in patients undergoing rehabilitation in the subacute phase of a NC. Most patient with NCs have comorbid conditions such as spasticity and differences in sensation not accounted for in previous research on broader populations. Combined with previous research, the findings of the present study demonstrate that the well-established effectiveness of cryoneurolysis as a treatment for knee pain is transferable to populations with NCs. Likewise, the improvements in V1for knee flexion align with and build upon previous research. For example, disability has been found to be strongly correlated with OA knee pain severity as measured by the WOMAC and inversely correlated with range of motion. These findings may explain the increase in V1 found in this study; cryoneurolysis effectively treated the pain associated with the OA, decreasing disability and increasing range of motion.
Altogether, this study provides strong evidence for the importance of cryoneurolysis in the subacute treatment of patients with NCs with knee OA. Specifically, it builds on previous research to underpin the effectiveness of cryoneurolysis as a treatment for pain in knee OA, which is strongly correlated with disability, in this population. Increased disability post-stroke during the subacute stages of rehabilitation can have long-standing negative effects, as it is when the most concentrated and impactful rehabilitation takes place. Therefore, inclusion of this procedure in clinical practice should be strongly considered along with further research on this promising application of cryoneurolysis.
Limitations: This study was limited by its sample size of 15 patients and variable follow-up times. Additionally, this was an unblinded, observational study, which did not include a control group. Future studies where these limitations are addressed would provide valuable further insight into the topic.
Conclusion: Cryoneurolysis is a novel treatment that can significantly reduce OA knee pain in patients with NCs. This decrease in pain was found to go along with a significant increase in V1. Together, these increase patient function and enable greater participation in the early stages of rehabilitation, which leads to more complete recoveries. Further prospective, multicenter studies and RCTs are required to examine the efficacy of this treatment for post-stroke populations thoroughly.
COI Unless noted below there are none. Mahdis Hashemi, MD – Disclosed research support (Pacira)
