Comparison of Comfort and Patient Preference of Common and a Novel Position for Ultrasound‐Guided Carpal Tunnel Injections

This study compared levels of discomfort among three positions for ultrasound‐guided carpal tunnel injections (USCTI) to potentially facilitate and improve the procedure's tolerability in treating carpal tunnel syndrome (CTS).

the flexor digitorum superficialis, and the flexor digitorum profundus tendons created by the carpal bones, scaphoid and lunate, and overlying transverse carpal ligament.Typical symptoms of CTS include night-time paroxysmal pain and paresthesias in the median nerve distribution of the wrist and hand.Some may experience weakness, changes in sensation and dexterity, and muscle atrophy in advanced cases.Repetitive movements, such as typing, may aggravate symptoms.Inflammation of the flexor tendons, edema or ossification of the bony floor, and dynamic intrusion of the muscle bellies of the flexor digitorum superficialis and hand intrinsics are all suspected to be causes of CTS. 1 Upon presentation, CTS commonly affects bilateral hands and the involvement of bilateral hands occurs in >80% of cases. 2 While CTS is considered a clinical diagnosis, the use of nerve conduction studies and electromyography as well as diagnostic ultrasound is common for confirmation and negation of confounding conditions like cervical radiculopathy, thought to be a likely misdiagnosis in the primary care setting. 1 In addition to its therapeutic effects, ultrasound-guided injections can confirm the diagnosis.
When considering non-operative treatment of CTS, corticosteroid injections have the highest efficacy after failure of first line therapy. 1 These have historically been performed with anatomic guidance, but the advent and integration of musculoskeletal and neuromuscular ultrasound into clinical practice and medical training has led to a growing number of these injections being performed via ultrasoundguidance.][5][6][7] Though there are several techniques to performing ultrasound-guided carpal tunnel injections (USCTI), the ulnar approach introduced by Smith et al in 2008 is favored by many interventional sonographers as it enables a safe trajectory into the confined space and permits ulnar deviation of the wrist allowing for further separation between the ulnar artery and nerve and the median nerve. 8][11] This is a significant gap in current medical literature as the injection site is small and the positions required to access the tunnel can be uncomfortable.Patient discomfort can lead to movement during procedures resulting in altered accuracy.This may lead to an increased likelihood of ineffective injections and decreased satisfaction.With healthcare models shifting away from fee-for-service payments, Medicare & Medicaid Services requiring health plans to publicly report patient satisfaction data, and health plans using patient satisfaction surveys to determine incentive compensation for physicians, there is a growing impetus for continuous improvement. 12his study sought to elucidate patient comfort and preference with positions used for performing USCTI.Three different positions, two commonly used (Hypersupination and Airplane) and one novel (total supported abduction [TSA]; referred to as Reclined-Rotated in our patient survey), were evaluated for their ease of getting into each position as well as tolerance of holding them for the expected length of an injection.The study also aimed to identify and characterize which musculoskeletal conditions may impact patient comfort and position preference to develop recommendations for positions that reflect an individual's health history.We hypothesized that the traditional Airplane position would be the most preferred by participants regardless of secondary musculoskeletal conditions affecting the neck and ipsilateral upper extremity.The presence of shoulder pain was hypothesized to negatively impact the tolerance of Hypersupination and TSA.

Material and Methods
Prospective participants were recruited from a Department of Veterans Affairs tertiary hospital's electrodiagnostic medicine (EMG) clinics with a goal n of 30.All ambulatory Veterans older than 18 years of age who were referred for evaluation of suspected carpal tunnel syndrome and presented during the 3-month span of the trial (July 2021 to October 2021) were offered to participate in this study.Exclusion criteria included acute pain or injury of the upper extremity and/or neck that may affect range of motion.Those remaining eligible individuals who consented to participate were guided through the study by a research assistant while an EMG was performed by the medical team on the contralateral arm.
The participants were guided through an electronic questionnaire administered via REDCap that captured age, gender, and secondary joint conditions (see Supplemental Information for a copy of the survey).Participants were asked whether they were suffering from pain or restriction of movement in the neck, shoulder, elbow, and/or wrist.For each area of endorsed pain, participants were guided through respective validated questionnaires.Pain surveys were adopted from sections of the Neck Disability Index (NDI), the American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form (ASES), the Patient-Rated Elbow Evaluation (PREE), and the Patient-Rated Wrist Evaluation (PRWE).
The NDI is a 5-10 minute survey adapted from the Oswestry Low Back Pain Disability Index consisting of 10 functional domains measured on a Likert scale.It has moderate level evidence for structural validity. 13The ASES has three domains-ease of use, activities of daily living, and self-evaluation-showing good reliability, high construct validity, and good responsiveness. 14The portions of the survey used in this study include quantification of shoulder pain and functional status of shoulder-involved daily activities.The PREE is a 20-question survey that evaluates pain and functional disability from elbow disorders with superior coverage of functional concerns to similar surveys. 15Finally, the PRWE is a 16-question survey also evaluating pain and functional disability from wrist disorders with good validity, reliability, and responsiveness. 16atients were asked to hold three different positions for 10 minutes each.Each position was followed by a survey of the patient's pain level via Numeric Rating Scale (NRS) before, during, and after each position, as well as their ease of getting into the positions, ability to maintain them, and any exacerbation of underlying symptoms.
The three positions studied are demonstrated in Image 1.They included two commonly used in carpal tunnel injection procedures: Hypersupinationparticipant is seated upright with arm lying adjacent to trunk with elbow flexed to $60 -90 and forearm placed in terminal supination; Airplane-participant is supine with shoulder abducted to $90 with wrist in neutral.Lastly, the novel position designated TSA was developed by the senior author to optimize ease of technical performance of the procedure was examined in this study.Here the participant is supine with arm raised above the head and rested on an elevated moldable pillow with elbow in $90 of flexion and wrist in neutral exposing the volar wrist surface.
As the Airplane position was hypothesized to be the best tolerated position, it was placed second in the order of positioning with Hypersupination and TSA alternating as first between participants.After completion of all three positions, participants were asked to select which was the most difficult to assume, most difficult to hold, and preferred position for comfort.Results were compiled anonymously and evaluated after all responses had been collected.
Demographics including rates of pain in specific body structures were summarized in a descriptive table.Visualized trends of the effect of position, order, and timing on Numeric Rating Scale (NRS) scores were analyzed with ANOVA (alpha = 0.05) after assessing assumptions of normality using Q-Q plots and the Shapiro-Wilk test.Significant results from ANOVA were further analyzed using post hoc pairwise tests with Bonferroni correction.Visualized trends of the effect of disability scores on position preference were analyzed with logistic regression.Visualized trends of the effect of position and disability scores on position preference on the before-during NRS score difference were analyzed with linear regression using position and each disability score as independent factors, with interaction effects planned if the initial model showed multiple fixed effects to be statistically significant.

Results
Of the individuals approached to participate in the study, 30 people were recruited, and all completed the positioning procedures.One was excluded by listwise deletion as they did not complete the study survey.Partial survey completion was not included in the final analysis.The demographic distribution of the participants is shown in Table 1.The participants were male-predominant (79.3%) with comparable representation of each age group.Most participants did not have shoulder pain (75.9%), but all pain subgroups were well represented.

Primary Outcomes
Pain As shown in Figure 1, NRS scores before the study procedure are predominantly 0 or 1, with several outliers in each group.The median and interquartile range of NRS scores associated with Hypersupination are moderately elevated compared with Airplane and TSA positions in the During Procedure (from 2/10 to 4/10 on the NRS) and After Procedure (from 2/10 to 3/10) timing blocks.
The primary outcome measure shows a visually and statistically significant increase in pain scores while holding the Hypersupination position compared with Airplane and TSA, which were not significantly different from each other.

Ability to Assume and Hold Position
Hypersupination was unanimously reported to be the most difficult position to assume, with an increase in pain twice as much as other positions as displayed in Figure 2. Two participants found TSA the most difficult to hold; the rest found Hypersupination the most difficult to hold.While no statistically significant difference was found between TSA and Airplane, no participant chose the Airplane position for either category.Due to having more data points, participants who chose Hypersupination for difficulty in assuming or holding the position had a greater variability of index scores.

Patient Preference
Out of 29 participants, 1 participant preferred Hypersupination, 13 preferred Airplane, and 15 preferred TSA positioning.Hypersupination was the least preferred and the most painful to assume and hold.

Effect of Concurrent Neck and/or Upper Extremity Conditions
Visualization of each disability score distribution per preferred, best held, or starting position (Supp.Figure 1) or per NRS score at each position (Supp.Figure 2) showed no obvious trends.In a model using positioning and each disability score as independent factors determining the change in pain, no disability score or position contributed more to recorded pain scores.(Figure 2) A logistic regression model of positioning and each disability score as independent factors determining whether the participant was able to hold the position was performed.Compared with the Airplane position,    PRWE on the ability to hold position along with a logistic regression curve is visually consistent with this statistical finding.(Figure 3) In each model, no significant difference between the effects of Airplane and TSA positioning or the other disability scores were apparent.

Effect of Position Order
Within each timing block, the Airplane position was second in the procedure series due to study design.The 1st and 3rd ordered positions randomized around the 2nd order Airplane position show no obvious visual trend favoring any position or pain score as illustrated in Figure 1 and Supp. Figure 1C.

Limitations
The results of this study are limited by several factors.Study size is a primary limiter; with only 30 total participants assessed, the power of the study is low and results may need confirmation with larger, more diverse sample sizes.Additionally, ANOVA analysis was used despite issues with the assumptions of normality and outliers, which could increase the risks of both Type I and Type II errors in the results.The participant population also diverges from the general population in terms of demographics and occupational hazards, especially gender in this case (79.3% of participants were male).This reduces the generalizability of these results outside the Veteran and active duty service member populations of which women respectively represent 10.7% and 17.3%. 17,18inally, although the protocol used was meant to approximate the patient's experience of holding a position for the safety pre-scan and performance of an ultrasound-guided steroid injection, no actual injections were performed.The true patient and/or provider experience of these positions during an actual clinical procedure may lead to different preferences, and assessment of this should be a goal of future research.Patient satisfaction and providerprovider reliability with accuracy, positioning, unilateral vs bilateral intervention, and technique are all factors that require vigilance with monitoring and improvement to attain quality assurance.

Discussion
The results of this study indicate that Hypersupinationwhich continues to see wide clinical use-is the most difficult and uncomfortable position for patients to assume and hold.The other two positions tested (Airplane, TSA) were preferable for the vast majority of patients, and there was no statistical difference between the two in regard to patient reported difficulty assuming, holding, or exiting the positions.Prediction of pain increase was weakly associated with pre-existing wrist pain and disability measured by the Patient-Rated Wrist Evaluation score, but no other disability index or position contributed more to recorded pain scores.
Many real-world patients do not experience wrist pain in isolation and will present with concurrent elbow, shoulder, and/or neck pain that may or may not be related to their wrist issue.Pain and disability at all three of these additional sites were assessed with specific, validated tools, but there was no statistically significant connection found between these variables and patient preference for any one position.The lack of a clinically relevant difference of pre-existing pain and disability in affecting position tolerance for people with carpal tunnel syndrome in particular is consistent with the lack of compelling evidence for positioning interventions like ergonomic keyboards. 19,20In clinical practice, any individual patient may find a given position difficult or uncomfortable for a multitude of reasons.There is no indication, however, that any particular constellation of upper limb pain or disability can consistently predict which position will be optimal.
Carpal tunnel injections are a common procedure performed on thousands of patients each year in a variety of clinical settings.While generally considered safe, the procedure still has associated risks.The serious adverse event rate of post-injection severe pain or a sympathetic reaction ranges from 0.3% to 0.5%, and the rate of mild adverse events including mild pain and swelling range from 9% to 65%. 21Though the individual risk of harm is low, the large volume of carpal tunnel injections performed in facilities offering these services accumulates significant potential harm of which there is an opportunity to relieve a great portion with simple and effective adjustments.To minimize these risks and maximize the chance of success, it is critical that the patient and provider are positioned optimally.This is accomplished by positioning the patient in a manner that they can hold comfortably throughout the procedure, making the site of injection easily accessible to the provider, and minimizing the time and space for set-up.Our study indicates that the traditional seated Hypersupination position is difficult and uncomfortable for the majority of patients to hold and offers no clear benefit to patient or provider.While there was no statistical difference between Airplane and TSA in regard to patient comfort, the TSA position may be quicker to set-up and require less space, making it preferable in a clinical setting.These findings, especially the particular disadvantage of the Hypersupination position, agree with a similar study showing increased comfort in an ultrasound elbow examination when positioned semi-supine instead of upright-seated and supinated. 22s CTS commonly affects bilateral hands, there is a need to find comfortable positions that allow access to both injection sites.The TSA position uniquely allows for bilateral USCTI without repositioning as demonstrated in Image 2. While sparing discomfort for the patient, using the TSA position may optimize clinical efficiency while cutting healthcare expenditure via reduced overall procedure time and medical supplies.

Conclusion
When performing USCTI, patient comfort can be optimized by avoiding Hypersupination of the wrist and opting for a position like Airplane or TSA which provide similar exposure for ulnar approach injections while inducing lower levels of discomfort.Given no differences in pain, TSA positioning may be considered to offer optimized clinic workflow, procedural efficiency, and resource allocation, especially for bilateral carpal tunnel injections or when an assortment of procedures is to be performed.

Image 1 .
Ultrasound-guided carpal tunnel injection positions displays the three study positions investigated: A, Hypersupination; B, Airplane; C, TSA.A B C participants were less likely to successfully hold the Hypersupination relative to the Airplane position (Estimate = À2.61,P = 4.76 Â 10 À3 ) and participants with lower PRWE scores were statistically less likely to hold any position (Estimate = À5.01Â 10 À2 , P = 3.14 Â 10 À3 ).The distribution of the effect of

Figure 1 .
Figure 1.Position effect on numeric rating scale.The figure displays the comparison of participant raw and summarized numeric rating scale (NRS) pain scores by position maneuver, timing of assessment in relation to the position, and order performed during the study visit.AP, Airplane; HS, Hypersupination.

Figure 2 .
Figure 2. The effect of positions on change in pain.This is a forest plot that displays the comparison of the difference of the reported Numeric Rating Scale scores before and during Hypersupination and TSA against Airplane's.It further explores the independent effect of secondary joint pain and associated disability on pain.ASES, American Shoulder and Elbow Surgeons Standardized Shoulder Assessment Form; NDI, Neck Disability Index; PREE, Patient-Rated Elbow Evaluation; PWRE, Patient-Rated Wrist Evaluation.

Figure 3 .Image 2 .
Figure 3. Logistic regression of PWRE predicting ability to hold position.The figure displays the ability of participants to maintain the positions for the prerequisite duration of time plotted against their PWRE scores.PWRE, Patient-Rated Wrist Evaluation.

Table 1 .
Study Demographics Note:The table displays the demographic information and the presence of concurrent pain affecting the neck and upper extremities of the 29 participants whose results were included in statistical analysis.