Assessing Injection Techniques in the Treatment of Trigger Finger

doi:10.4236/mps.2012.24020

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Modern Plastic Surgery, 2012, 2, 83-86

http://dx.doi.org/10.4236/mps.2012.24020 Published Online October 2012 (http://www.SciRP.org/journal/mps) 83

Assessing Injection Techniques in the Treatment of

Trigger Finger

John R. Fowler1, Lauren Ogrich2, Perry Evangelista3, Alyssa A. Schaffer1

1Temple University Hospital, Department of Orthopaedics, Philadelphia, USA; 2Temple University School of Medicine, Philadelphia,

USA; 3University of Pennyslvania School of Medicine, Philadelphia, USA.

Email: [email protected]

Received June 7th, 2012; revised July 8th, 2012; accepted August 6th, 2012

ABSTRACT

Background: Trigger finger is characterized by the inability to smoothly flex and extend the digit. Corticosteroids are

an accepted non-surgical treatment option and can be delivered via two techniques. While the palmar approach is more

commonly used, some have suggested that the mid-axial approach may be less painful for patients and yield higher in-

trasheath injection rates. The purpose of this study is to compare the accuracy of the palmar and midaxial approaches

for delivery of corticosteroids into the flexor tendon sheath using radio-opaque dye in a cadaver model. Methods: A

total of 50 injections were performed, 25 via midaxial technique and 25 via palmar technique. A one inch, 25-gauge

needle was used to inject 1 mL of Isovue contrast dye into the flexor tendon sheath under live fluoroscopy. The fluoro-

scopic images were examined after injection to determine intrasheath versus extrasheath delivery of the dye, with visu-

alization of contrast filling the sheath defining a successful injection. Results: The midaxial approach had a success rate

of 52% compared to the conventional palmar approach success rate of 36%, p = 0.5. The ring finger is the most com-

mon location of trigger finger and the rates of success were equal between groups for this digit (80%). Conclusions:

Based on our findings, there is no statistical difference in the accuracy of intrasheath injection between the midaxial

technique and palmar technique. The midaxial technique can be considered as an alternative to the palmar technique for

trigger finger injection.

Keywords: Trigger Finger; Injection; Corticosteroids; Palmar and Midaxial Approaches

1. Introduction

Trigger finger, also known as stenosing tenosynovitis or

stenosing tendovaginitis, is a common condition affect-

ing nearly 100,000 Americans annually [1]. It is charac-

terized by the inability to smoothly flex and extend the

digit [1]. The patho physiology of stenosing tenosynovitis

is related to a disproportion between the volume of the

flexor sheath and its contents, the flexor tendons [1].

Non-surgical management consists of activity modifica-

tion, non-steroidal anti-inflammatory medications, and

corticosteroid injection [1]. The reported effectiveness of

corticosteroid injections has ranged from 25% - 77% [2-

6]. A recent systematic review examining the effective-

ness of corticosteroid injections found corticosteroid in-

jections to be effective in only 57% of patients [7].

Although several studies have found extra-sheath cor-

ticosteroid injections to have some benefit in the treat-

ment of trigger finger [3,8], the gold standard remains

delivery of the corticosteroid into the flexor tendon

sheath [1,9]. Two major techniques exist to deliver the

corticosteroid into the flexor tendon sheath: the palmar

approach and the midaxial approach [1,2,9]. While the

palmar approach is more commonly used, some have

suggested that the mid-axial approach may be less pain-

ful for patients and yield higher intrasheath injection

rates [1,2,9]. Studies examining the accuracy of intra-

sheath injection by conventional techniques found deliv-

ery into the tendon sheath occurs in only 37% - 50% of

patients [8,10]. If intrasheath delivery of therapeutic me-

dications is an important factor in the treatment of trigger

finger, then determining the optimal injection technique

is critical.

The purpose of this study is to compare the accuracy

of the palmar and midaxial approaches for delivery of

corticosteroids into the flexor tendon sheath using radio-

opaque dye in a cadaver model.

2. Methods

The left hands of ten embalmed cadavers were used in

this study. The cadaver hands were randomly assigned to

receive injection of corticosteroid into the flexor tendon

sheath by either the midaxial or palmar approach. For the

Assessing Injection Techniques in the Treatment of Trigger Finger

palmar injection technique, the needle was introduced at

the level of the A1 pulley and was advanced until resis-

tance was felt. The needle was withdrawn slightly to en-

sure it was no within the tendon (see Figure 1) and then

the contrast was injected. The midaxial technique was

performed as described by Carlson [7]. From the radial

border of the finger, the needle was inserted into the

midlateral area of the proximal phalanx (see Figure 2).

The needle was inserted until resistance was felt an d th en

finger was then flexed and extended to confirm that the

needle was not in the tendon itself. The contrast dye was

then injected.

A one inch, 25-gauge needle was used to inject 1 mL

of Isovue contrast dye into the flexor tendon sheath under

live fluoroscopy. Isovue dye was provided by the De-

partment of Radiology. The fluoroscopic images were

examined after injection to determine intrasheath versus

extrasheath delivery of the dye. A positive outcome was

defined as contrast medium tracking proximally and dis-

tally through the flexor tendon sheath on fluoroscopic

Figure 1. Photograph demonstrating palmar injection tech-

nique.

Figure 2. Photograph demonstrating the mid-axial injection

technique.

images (see Figure 3). A negative outcome was defined

as an injection that did not fill th e tendon sheath on fluo-

roscopic images (see Figure 4).

Each finger was injected on each hand for a total of 50

fingers, 25 midaxial and 25 palmar. All injections were

performed by a senior orthopaedic resident. The finger,

technique, and result were recorded for each hand and

images saved for review by the senior author. Statistical

analysis was performed using Graphpad (La Jolla, CA)

Software. Fisher’s exact test was used to determine sta-

tistical significance. A power analysis was performed

prior to the initiation of the study, which found a sample

size of 25 injections would be needed in each group to

detect a difference of 30% between groups, assuming an

alpha value of 0.05 and a beta value of 0.8.

Institutional Review Board ex emption was obtained as

this was a cadaver study withou t live subjects.

3. Results

The midaxial approach had a success rate of 52% com-

pared to the conventional palmar approach success rate

of 36%, p = 0.5. See Table 1. Injection of the thumb was

difficult regardless of the approach, yielding an overall

success rate of 0%. If this data is removed, the success

rates for the other fingers improves to 65% for the mi-

daxial and 45% for the palmar approach, p = 0.4. The

palmar approach was also found to have a 0% success

rate in the small finger, whereas the midxial approach

had a success rate of 80% in this digit. The rin g finger is

Figure 3. Positive intra-sheath injection, showing contrast

tracking throughout the sheath.

Figure 4. Negative intra-sheath injection, showing contrast

tracking outside the sheath.

Assessing Injection Techniques in the Treatment of Trigger Finger 85

Table 1. Injections by loca tion and technique

Finger Midaxial

Positive Midaxial

Negative Palmar

Positive Palmar

Negative

Thumb 0 5 0 5

Index 1 4 2 3

Long 4 1 3 2

Ring 4 1 4 1

Small 4 1 0 5

Total 13 12 9 16

the most common location of trigger finger and the rates

of success were equal between groups for this digit

(80%).

4. Discussion

Corticosteroids are often the first line of treatment for

trigger finger and have relatively high treatment success

rates. Unfortunately, intra-tendon sheath injections given

via a palmar approach injection technique are painful for

the patient and can cause tendon rupture if the injection

releases corticosteroid in the tendon itself. The midaxial

technique has similar success rates at treating the symp-

toms of the triggering d igit as the palmar approach injec-

tion technique and has been reported to be less painful

[1,3,7]. The current study specifically addressed the in-

jection technique and the ability to deliver contrast me-

dium into the flexor tendo n sheath.

This study has several limitations. The cadavers used

in this study were embalmed and this could affect the

distensibility of the flexor sheath and possibly make in-

trasheath injection more difficult. Due to the limited

availability of cadaver hand s, the number of injections to

each finger (5 in each group) is relatively low. This study

is underpowered, as an a priori power analysis found that

25 injections would be needed to show a difference of

30% in each group. The difference found in this study,

however, was only 19%, which would have required over

150 injections. It would be interesting to inject a larger

number of fingers to determine if the techniques were

more similar in success rates with a larger sample size. A

single surgeon performed all injections, introducing op-

erator bias. The determination of a positive versus nega-

tive injection is also subject to bias, although the images

were reviewed by a senior hand surgeon who was not

present for the injections and the agreement was 100%.

To our knowledge, this is the first study to use contrast

dye in a cadaver model to determine the intrasheath ac-

curacy of the palmar and midaxial injection techniques.

Although underpowered, our findings demonstrate no

difference in the accuracy of intrasheath injection be-

tween the midaxial technique (52%) and palmar tech-

nique (36%), p = 0.5. Our data is comparable to previ-

ously published studies that demonstrated intrasheath

injection rates of 37% - 57% [10-12]. We were unable to

deliver the contrast medium into the thumb flexor tendon

sheath with either approach, which also coincides with

earlier studies [8,10]. It is possible that the lack of suc-

cessful treatment of trigger finger with corticosteroid

injections is due to the inability to deliver the steroids

into the sheath.

5. Conclusion

Based on our findings, there is no statistical difference in

the accuracy of intrasheath injection between the mida-

xial technique and palmar technique. The midaxial tech-

nique can be considered as an alternative to the palmar

technique for trigger finger injection.

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