Comparison of three different incision techniques in A1 pulley release on scar tissue formation and postoperative rehabilitation

Stenosing tenosynovitis of a flexor tendon, also known as trigger finger, is a common debilitating hand pathology frequently seen and treated by hand surgeons [1, 2]. First described by Alphonse Notta in 1850, the name results from the painful popping or clicking while flexing/extending the involved digit [3]. This triggering is most often due to an inflammation-derived size discrepancy of the involved flexor tendons causing impingement at the level of the hypertrophic first annular (A1-) pulley [4]. If conservative treatment such as splinting and/or corticosteroid injection does not or no longer applies as a promising treatment option, surgical release of the A1-pulley is indicated [4, 5].

Especially in the field of handsurgery, the location and pattern of the incision with regard to hand function, anatomic considerations and aesthetics are paramount for the success of the surgery [6‐8]. There is quite a plethora of different skin incisions described to approach the A1 pulley. The type of incision one surgeon will choose most likely depends on the surgical training and on his surgical mentors rather than having experienced and tested multiple incisions himself [9, 10]. Supposedly, this circumstance has led to strong convictions amongst some surgeons about which incision technique is superior over another.

Even though the A1-pulley release is considered as one of, and possibly the smallest, elective hand surgery procedure, most hand surgeons would agree that there is a considerable amount of patients that will present with a prolonged recovery period mostly due to scar formation along with subsequent irritation in daily activities or sports (e.g. golf, tennis). Adverse events between 5 and 36 % in the setting of trigger finger release have been reported [11‐15], including persistent triggering, recurrence and wound healing problems such as infections, wound dehiscence, and painful scar tissue irritation. Anecdotic events involve tendon rupture, bowstringing, and nerve damage [16, 17]. However, by far the most reported complaints are wound healing irritations as well as pain and tenderness of overabundant scar tissue [11‐13], limiting the patient’s use of his hand until weeks after the initial successful surgery.

In this prospective study, we hypothesized that the type of skin incision is a major predictor regarding the amount of postoperative scar tissue formation and the speed of recovery. Furthermore, there is no consensus recommendation on which incision technique is best for surgical release of trigger fingers. Therefore, we sought to investigate the level of scar tissue formation and degree of postoperative disability by comparing three of the most common incision techniques known to the authors: (1) horizontal at the level of the distal palmar crease, (2) horizontal 2–3 mm distal from the distal palmar crease, and (3) a longitudinal incision at the level of the A1-pulley location. We employed the “Disability of the Arm, Shoulder and Hand questionnaire” (DASH score) at different time points over a course of 12 months postoperatively and measured the volume of the resulting scar tissue quantitative ultrasound technique after 3 months [18].

Age and gender were evenly distributed in all three groups without significant differences with a mean age of 62 (±12.59) years. Thirteen women and 17 men were included. Twenty-four of 30 patients (80 %) were right-dominant and the affected fingers were evenly distributed on dominant and non-dominant hands [14 (44 %) vs 15 (47 %)], (Table 1). Furthermore, about one out of three affected fingers previously received corticosteroid injection, six fingers once, two fingers twice and one finger three times (Table 1).

The third finger was most often affected (n = 17; 53 %), followed by the ring finger (n = 8; 25 %), then index finger (n = 4; 13 %) and finally small finger (n = 3; 9 %), (Fig. 3).

We have received and included 110 complete DASH score sheets from all four time points of 128 possible DASH scores, resulting in an overall response rate of 85.9 % (Table 2).

Here, we investigated the effect of three different skin incisions to access the A1-pulley and their impact on postoperative outcomes including the DASH score as well as quantitative scar volume measurement. The total response rate of DASH questionnaires was 85.9 % allowing for reliable data analysis. In this study, the middle finger was most often affected (61 %), followed by the ring finger (29 %) and index finger (14 %). This pattern of distribution is in line with findings from other investigators [4].

About 30 % of our patients received at least once a corticosteroid injection as a semi-invasive treatment for A1-pulley stenosis. Although the aim of this study was not to investigate the effectiveness of corticosteroids, one can well conclude that a relevant amount of patients requires surgery after initial unsuccessful injection(s), which has been demonstrated extensively by other authors [21‐27].

Even though scar volume was elevated by almost 75 % in group 1 3 months post surgery compared to groups 2 and 3, these changes were statistically not significant. However, this increase in group 1 should not be neglected in terms of interpretation. We are inclined to hypothesize that an incision placed directly into a fibroseptal-anchoring structure such as the distal palmar crease stimulates a more pronounced scar tissue reaction compared to incision techniques outside this crease. This might be caused by the local disruption and the subsequent cellular stimulation of this mechanically relevant structure with its predominance of connective tissue. Furthermore, an everted wound closure technique was more complex in group 1 due to the inverted nature of the distal palmar crease. Groups 2 and 3 showed almost identical scar tissue volume levels which can be interpreted as another indicator that an incision located in the crease appears to be the most denominating factor for subsequent scar tissue formation.

All types of incisions and A1 pulley releases caused a significant improvement of symptoms when looking at DASH scores at 3 and 12 months. The most pronounced and fastest amelioration of symptoms were found in group 3 (longitudinal incision) indicated by a highly significant reduction of the DASH score already at 1 month postoperatively (p < 0.001). At this early time point, group 2 even exerted a slight increase and group 1 only a mild reduction (Figs. 4, 5a, b). We tend to explain these findings by the nature of the longitudinal incision: (1) excellent exposure of the A1 pulley, (2) facilitated everted wound closure and (3) tension forces parallel to the incision as opposed to scar stimulating perpendicular tension forces in horizontal incisions (group 1 and 2) when the fingers are extended. A slight disadvantage of the longitudinal incision might be its limitation in distal and proximal direction for the rare necessity to lengthen the incision. These circumstances taken together lead in our opinion to lesser tissue irritation and therefore accelerated wound healing with less scar formation in an early stage of wound healing.

To our surprise, we found a significant difference in the baseline DASH scores: group 1 and 3 demonstrated a significant higher baseline DASH score compared to group 2. This is clearly a coincidental flaw in this study and could have been prevented if patients would have been matched for DASH values instead of age and gender. However, this might have led to significant differences in age and/or gender distribution and additionally would have limited the blinded and randomized nature of this study. This being said, it stands to reason if the significant reduction in DASH score values of group 2 vs group 1, 12 months postoperatively, is of any clinical value.

Finally, we analyzed relative DASH score changes (delta-DASH) at all time points in all groups. The degree of reduction in DASH score level was significantly increased at all postoperative time points when group 3 was compared to group 2; however, not significant when group 3 was compared to group 1 (Fig. 5b, p < 0.05). These findings would also confirm our idea of a supremacy of the longitudinal incision over the incision 2 mm distal from the distal crease.

In summary, our findings in this study suggest an incision at the level of the distal crease as least favorable given the increased levels of scar tissue formation and the obvious surgical difficulties for adequate wound closure when compared with the two other incisions. However, after 3 and 12 months DASH scores dropped as significantly as in group 3. When finally comparing group 2 vs 3 with the aim to determine the best incision we are inclined to favor the longitudinal incision given the outstanding early first month results with a highly significant drop in DASH score values.