A proximal interphalangeal joint custom-made orthosis in trigger finger: Functional outcome

Abstract

Introduction

Trigger finger is a common and functionally limiting disorder. Finger immobilization using an orthotic device is one of the conservative treatment options for treating this condition. The most common orthosis previously described for trigger finger is metacarpophalangeal joint immobilization. There are limited studies describing the effectiveness of proximal interphalangeal joint orthosis for treatment of trigger finger.

Methods

This study was a single group pretest-posttest design. Adult patients with single digit idiopathic trigger finger were recruited and asked to wear a full-time orthoses for 6 weeks. The pre- and post-outcome measures included Quick-DASH score, the Stages of Stenosing Tenosynovitis (SST), the Visual Analogue Scale (VAS) for pain, the number of triggering events in ten active fists, and participant satisfaction with symptom improvement. Orthotic devices were made with thermoplastic material fabricated with adjustable Velcro tape at the dorsal side. All participants were given written handouts on this disease, orthotic care and gliding exercises. Paired t-tests were used to determine changes in outcome measures before and after wearing the orthosis.

Results

There were 30 participants included in this study. Evaluation after the use of PIP joint orthosis at 6 weeks revealed that there were statistically significant improvements in Quick-DASH score from enrolment (mean difference −29.0 (95%CI −34.5 to −23.4); p < 0.001), SST (mean difference −1.4 (95%CI −1.8 to −1.0); p < 0.001) and VAS (mean difference −3.4 (95%CI −4.3 to −2.5); p < 0.001). There were no serious adverse events and patient satisfaction with the treatment was high.

Conclusions

Despite our small study size, the use of proximal interphalangeal joint orthosis for 6 weeks resulted in statistically significant improvements in function, pain and triggering, and also high rates of acceptance in patients with isolated idiopathic trigger finger.

Introduction

Trigger finger or stenosing flexor tenosynovitis is a common and functionally limiting disorder that occurs with a prevalence of approximately 2% in the general population with middle-aged women most commonly affected. ¹ The symptoms include pain, stiffness, catching, or locking digits. ² The disease can limit basic activities of daily living such as grasping, holding objects, gripping, manipulating coins, and performing buttoning tasks. Most frequently, the fibro-osseus tunnel or A1 pulley located on the palmar side of the metacarpophalangeal (MCP) joint is affected. The A1 pulley holds the flexor tendon close to the phalanges, providing smooth gliding motion. Pathogenesis of trigger finger is described by Ryzewicz and Wolf as ‘‘a mismatch between the volume of the flexor tendon sheath and its contents’’. ²

Several treatment options have been described in the past such as rest, anti-inflammatory medication, joint immobilization, corticosteroid injections, and surgery. ² The European HANDGUIDE group have recommended the use of orthoses combined with corticosteroid injections as a suitable option. ³ Successful outcomes were reported in 72% of patients with symptom duration of < 4 months who were treated with combined steroid injection and orthotic treatments. ⁴ Joint immobilization alone is also successful in all fingers except for thumb and late locked fingers that cannot be passively unlocked. ⁵ Ryzewicz and Wolf suggested orthotic treatment “appears to be a reasonable option for patients with mild triggering who do not wish to undergo steroid injection”. ² Orthotic treatment may alter the biomechanics of the flexor tendons while encouraging maximal differential tendon glide. The purpose of an orthosis is to decrease the amount of mechanical friction of the flexor tendons within the tendon sheath, allowing the affected finger to rest and heal. A recent systemic review for conservative management of trigger finger suggests wearing the orthosis for 6 weeks. ⁶ Most orthoses for trigger finger described in the past have been designed to block the MCP joint to varying degrees. Studies on the effectiveness of a MCP joint orthosis reported good outcomes in 73–77% of their patients after 6 weeks wear.^5,7 However, various orthotic designs have been discussed with regard to which joint to immobilize and to what degree. A distal interphalangeal (DIP) orthosis was used by Rodgers to limit excursion of the flexor digitorum profundus tendon and to allow tenosynovitis to resolve. ⁸ Sheon chose to immobilize the proximal interphalangeal (PIP) joint using flexible elastic or cling gauze for 2 weeks but did not mention the effectiveness of this technique. ⁹ Teo et al. compared a custom-made MCP joint orthosis with a commercially available PIP joint Oval-8 orthosis and reported both orthoses were effective in reducing pain, disability and improving triggering symptoms, but the commercial PIP joint orthosis provided superiorly restricted hook fist posture, limiting the maximal differential glide between flexor digitorum superficialis (FDS) and flexor digitorum profundus (FDP), and was more effective than the MCP joint orthosis. ¹⁰ Since then, no studies have demonstrated the outcome of custom-made low profile adjustable PIP joint orthoses.

The aim of this study was to evaluate the outcome of a custom-made adjustable PIP joint orthosis in patients with idiopathic trigger finger with the Stages of Stenosing Tenosynovitis (SST) 2 to 5 and symptom duration of less than 6 months.

Methods

This was a single group before and after study design. Following approval by the Ethics Committee and Institutional Review Board, adult patients aged 18 years or older with single digit idiopathic trigger finger and who were treated at the orthopaedic outpatient clinic between March 2020 and May 2020 were recruited. Procedures for the screening of COVID-19 infection for patients were used according to hospital visitor policies. After screening, patients with an onset of less than 6 months and the Stages of Stenosing Tenosynovitis (SST) 2 to 5 were invited to participate. Patients were excluded if they had received prior treatment (corticosteroid injection and surgery) or if their symptoms involved triggering thumb. Pain control was not prescribed and patients were advised to withhold taking pain medication during the treatment. After reading an informative letter describing the purpose and design of the study, written informed consent was obtained from each patient.

All participants received a custom-made volar thermoplastic orthosis with dorsal adjustable Velcro tape (Figure 1). The orthosis was measured from mid proximal phalanx to mid middle phalanx and fabricated by a certified hand therapist. The PIP joint motion was immobilized at 0 degrees. MCP and DIP joints were not immobilized. Patients were instructed to wear the orthosis full time for 6 consecutive weeks, but were also advised to remove the device twice a day for hygiene and to perform gliding exercises to prevent joint stiffness.

Figure 1.

The custom-made adjustable proximal interphalangeal (PIP) joint orthosis used in the study. (a) Volar side. (b) Dorsal side. (c) Medial side.

Outcome measurement

Patient demographic data (such as age, gender, underlying disease) and clinical data relating to the trigger finger (such as onset of symptoms, dominant hand, etc.) were recorded. The primary outcome was the short-form version of the Disabilities of the Arm, Shoulder and Hand (Quick-DASH) self-reported questionnaire. ¹¹ The scores range from 0 (no disability) to 100 (most severe disability), as a measure of functional status. Secondary outcomes were the Stages of Stenosing Tenosynovitis (SST) ⁵ which assesses clinical severity and ranges from 1 (normal) to 6 (locked in a flexed position; see Table 1), the visual analogue scale (VAS) for pain intensity range from 0 (no pain) to 10 (worst possible pain), and the number of triggering events in ten active fists (NTTAF). These outcomes were assessed at baseline, and again after wearing the orthosis for 6 weeks. Patients unable to attend the outpatient department were contacted by phone at 6 weeks and interviewed to obtain their responses. In addition, data regarding the percentage of each day spent wearing the orthosis as a measure of compliance, complications (such as finger stiffness, pressure sore, and finger numbness), and patient satisfaction were also collected.

Table 1.

Stages of stenosing tenosynovitis.

Stage	Symptoms
1	Normal
2	A painful palpable nodule
3	Triggering
4	The proximal interphalangeal joint (PIP) locks into flexion and is unlocked with active PIP joint extension
5	The PIP joint locks and is unlocked with passive PIP joint extension
6	The PIP joint remains locked in a flexed position

Sample size and statistical analysis

Power calculations are based on our primary endpoint of Quick-DASH score, before and 6 weeks after having the orthosis. A previous study by Drijkoningen T. et al. estimated mean Quick-DASH scores were 24 (SD 19) before having an orthosis, and 16 (SD 16) after application of orthosis applied at night only. ¹² Our study used a full-time orthosis continuously for 6 weeks, so we estimated that we would see a greater reduction in Quick-DASH score in our patients to approximately 12 points. We estimated there would be a small correlation between the pre- and post- intervention DASH score of 0.25. Under these assumptions, enrolling 30 patients in our study would give 80% power to detect this difference at a 2-sided significance level of 5%.

The Normality of continuous variables was checked by the Shapiro Wilks W test. The distribution of continuous variables was described as mean and standard deviation (SD); categorical variables were described as number (%). Mean differences in Quick-DASH score and other secondary endpoints were analysed using a paired t-test before and after wearing the orthosis. Spearman’s correlation and linear regression techniques were used to explore associations between Quick-DASH score and patient compliance. Statistical analysis was conducted with Stata 16.0 (Statacorp, College Station, TX, USA).

Results

Thirty-five participants were initially screened; 2 were excluded because of late stage (SST) and switched to open release. Thirty-three patients were enrolled and 2 were lost to follow up, and 1 voluntarily dropped out. Thus, a total of 30 patients with 30 trigger digits were included in the analysis. Of these, 19 patients were women and 11 were men, with a mean age of 59 years (SD ± 12, range 43–72). The digits affected included ring finger (n = 18), followed by middle finger (n = 10) and index finger (n = 2). In 87% of the patients, the trigger finger affected the dominant hand (n = 26). The mean symptom duration was 3.7 months (SD ± 2.16, range 0.5–6). Descriptive data of participants is shown in Table 2.

Table 2.

Participant characteristics baseline.

Characteristic	Value (n = 30)
Affected finger
Index	2 (6.7)
Middle	10 (33.3)
Ring	18 (60)
Affected hand
Right	16 (53.3)
Left	14 (46.7)
Associated disease
Diabetes	5 (16.7)
Rheumatoid arthritis	1 (3.3)
Others	13 (43.3)
Mean (SD) symptom duration in months	3.7 (2.16)

SD: standard deviation.Note: Values are N (%) unless otherwise indicated.

Primary and secondary outcome measures are summarized in Table 3. The mean Quick-DASH score decreased from 44.2 (SD ±18.5, range 3.6–75) at enrolment to 15.3 (SD ± 11.4, range 0–40.6) after 6 weeks of orthosis wearing: a mean change of −29.0 (−34.5 to −23.4); P < 0.001. The mean pain score decreased from 5.3 (SD ±2.7, range 0–10) at enrolment to 1.9 (SD ±1.8, range 0–6) after orthotic treatment, equating to a mean change of −3.4 (−4.3 to −2.5); P < 0.001. The mean SST significantly decreased from 3.7 (SD ±1.1, range 2–6) to 2.3 (SD ±1.2, range 1–5) at 6 weeks. Mean patient compliance over the 6-week treatment period was 66.1 (SD ±19.97, range 20–100).

Table 3.

Mean (SD) values of continuous test scores pre- and post-intervention, and mean difference in change (95%CI) from baseline to six weeks.

Outcomes	Mean (SD) pre-intervention score (baseline)	Mean (SD) post-intervention score (after six weeks)	Mean change (95%CI) from pre- to post-intervention	P
Quick-DASH score	44.2 (18.45)	15.3 (11.41)	−29.0 (−34.5 to −23.4)	<0.001
VAS	5.3 (2.65)	1.9 (1.75)	−3.4 (−4.3 to −2.5)	<0.001
SST	3.7 (1.05)	2.3 (1.24)	−1.4 (−1.8 to −1.0)	<0.001
NTTAF	6.3 (3.31)	2.3 (2.43)	−4.0 (−5.0 to −2.9)	<0.001

QuickDASH: quick disabilities of the arm, shoulder and hand (0–100); VAS: visual analogue scale (0–10); SST: stages of stenosing tenosynovITIS (1–6); NTTAF: number of triggering events in ten active fists (0–10); SD: standard deviation; 95%CI: 95% confidence interval; P: P-value from paired t-test for comparison of post- and pre-intervention scores.

Spearman’s coefficient demonstrated a negative monotonic relationship between Quick-DASH score reduction and percent patient compliance (Spearman’s rho = −0.53; P = 0.004). We further explored this association using a scatterplot and linear regression model of Quick-DASH score reduction and percent compliance, which also demonstrated this negative relationship (regression line slope (red line in Figure 2) = −0.39 (95%CI −0.65 to −0.12), indicating that increasing compliance use was associated with significantly greater reductions in Quick-DASH score.

Figure 2.

Scatter plot showing relationship between Quick-DASH score reduction and percentage of use. The red line shows inverse linear relationship.

Neither finger stiffness nor numbness were reported by any study participant. Only 2 of 30 patients reported having grade I pressure sores (painful redness of skin without loss of skin dermis) at the medial and lateral side of the middle phalanx, but all healed without further progression. Although patients complained of discomfort during the first week, all except one patient in the study were satisfied with their treatment outcomes. The patient who was dissatisfied voluntarily withdrew from the study.

Discussion

This study evaluated the clinical outcomes of custom-made PIP joint orthosis for treatment of patients presenting with SST 2–5 trigger digit and onset of less than 6 months. This kind of orthosis resulted in statistically significant reduction in pain (improvement of Quick-DASH score and pain score) and improved trigger symptoms (decrease of NTTAF and SST scores). The minimum change required to detect clinical improvement by Quick-DASH is a reduction of 8.0 points. ¹³ The plausible magnitude of improvement in our study according to the 95%CI around the mean improvement ranges from 23 to 34.5 points, indicating that the improvements observed in our study are clinically significant. Likewise, the 95%CI around the mean reduction in pain score by VAS was −3.4 with 95%CI ranging −4.3 to −2.5. This also indicates that > 50% of patients in our study achieved a reduction in pain score of 3, which is considered the minimal clinically important difference. ¹⁴ There were no major complications. Only 2 from 30 patients reported minimal adverse effects.

The purpose of orthosis is to decrease flexor tendon friction within the tendon sheath, allowing the affected finger to rest. The most commonly used orthosis for trigger finger is MCP joint immobilization, but there is no consensus on the best approach.^5,7,15,16 Evan et al. reported using a MCP joint orthosis in 55 digits with a 73% success rate. ⁷ An alternative MCP joint orthosis with less bulky design was described by Lindner-Tons and Ingell. ¹⁷ Various degrees of MCP joint position have been described in previous studies. Colbourn et al. evaluated the effectiveness of a MCP joint orthosis with the MCP joints positioned in 10–15 degree of flexion in 28 participants with 93% of participants reporting improvement in triggering symptoms. ¹⁵ Rodgers et al. reported an 83% success rate with use of a distal interphalangeal (DIP) joint orthosis. ⁸ Tarbhai et al. compared 2 types of orthoses between MCP joint orthosis and DIP joint orthosis and found that treatment with the MCP joint orthosis was successful in 77% of the patients, whereas DIP joint orthosis was successful in 47% of the patients. ¹⁶ Sheon and Swezy used PIP joint orthosis for treatment of trigger finger, but they did not demonstrate effective outcomes.^9,18 Teo et al. reported effectiveness of custom-made MCP joint orthosis compared with commercial Oval-8 PIP joint orthosis and found that both orthosis were effective in reducing pain and improve triggering symptoms, but while QuickDASH score improved with both orthoses, only the PIP joint orthosis demonstrated a statistically significant improvement after treatment. ¹⁰ Many authors have recommended full-time orthosis use to maximize symptom improvement, and this is consistent with the inverse relationship we observed between compliance and functional improvement.^9,10,18 Since triggering of the little finger has the lowest incidence, ¹ we did not have any cases of triggering in the little finger during the enrolment phase of our study.

Both MCP joint orthosis and PIP joint orthosis appear to be effective in reducing pain and triggering symptom because both orthoses limit maximal glide between FDS and FDP, allowing the tendons to rest. ¹⁰ In our study, patients were prescribed to wear a full-time orthosis during daily activities and also during sleep. Our custom-made adjustable design PIP joint orthosis was different from a commercial PIP joint orthosis from a previous study ¹⁰ due to its low profile and adjustability to custom-fit the patient’s finger. Orthotic outcome evaluation was performed after 6 weeks from the first visit in our study, so ongoing evaluation and follow-up of these patients is necessary to assess the recurrence of symptoms post-orthotic treatment. The PIP block orthosis limits finger flexion more than the MCP block orthosis. Most patients complained of discomfort while wearing the orthosis in the first week, but with continued use, triggering symptoms resolved and patients reported high satisfaction with the orthosis. Our results therefore concur with a previous study in terms of effectiveness of orthosis treatment and the duration the orthosis was worn per day. ¹⁰ Only one patient with triggering of the index finger felt their symptoms did not improve and elected to switch to intra-tendon sheath steroid injection before final follow-up (1 out of 33 patients). It would be appropriate to study this patient group further and obtain a sub-analysis for the satisfaction rates such as underlying disease and severity. A larger number of the patients is recommended to assess these associations in a future study.

The small sample size and lack of control group are significant limitations of this study. Our follow-up time was limited to six weeks, and some patients had a six-week assessment conducted by phone due to the COVID situation. Whether or not symptoms will recur with further follow-up is unknown and an issue for future study.

Conclusions

In patients with mild to moderate clinical severity and recent symptom onset of trigger, a PIP joint orthosis worn for 6 weeks resulted in statistically and clinically significant improvements in function, pain and triggering. Prescription of a custom-made PIP joint orthosis which has a low profile and is custom-fit is recommended as an alternative orthosis for patients in whom MCP or DIP joint immobilization would be inconvenient.