A prospective clinical study of the A1 pulley in trigger thumbs

Isolated A1 pulley release surgery for trigger finger leads to significant increase in tip-to-tip pinch strength

BACKGROUND

Even in the first application of patients with early complaints of trigger finger, pinch strength of the hand may be affected. Therefore, it is difficult to assess the change of strength as a result of treatment in this problem. In this study, we aimed to evaluate the change of strength taking into account both measured and expected pinch strengths before and after A1 pulley release surgery.

METHODS

Thirty fingers (9 thumbs, 12 middle, 8 ring and 1 index fingers) of 26 patients (17 women, 9 men) who underwent A1 pulley release were included into this study. The mean age of the patients was 53 (16-71). Tip-to-tip finger pinch strengths were measured pre-operatively and at 3 months postoperatively. The expected strengths were calculated using the values obtained from the healthy side and taking into account the dominance effect. In the analysis, pre-operative and postoperative measured strength/expected strength ratios were compared.

RESULTS

The mean of measured pinch strength/expected pinch strength ratio was 0.91 ± 0.3 pre-operatively and 1.14 ± 0.3 postoperatively (p < 0.05).

CONCLUSION

With the calculation method used in this study, it was found that there was a significant increase in the tip-to-tip pinch strength after surgical A1 pulley release for the trigger finger.

LEVEL OF EVIDENCE

III (Retrospective cohort study).

Morphometric study of pulleys of the thumb

Pulleys are thickened regions in flexor tendons sheaths of the digits. They are essential and act as fulcrum for the flexion and extension of the digits. The arrangement and number of pulley system differs greatly between the thumb and other digits. There is paucity of literature regarding the pulley system of thumb. We aimed to study the morphometry of the pulley system of the thumb in Indian cadavers. Dissection was carried out in 55 adult human cadaveric thumbs. The most common morphologic pattern of pulley observed in the thumb is type III (30 thumbs). The least observed is type I (4 thumbs). The mean width and standard deviation of A1, Av, oblique, and A2 pulleys are 5.06±0.87, 5.38±1.22, 4.68±1.13, and 6.04±1.41 mm, respectively. The gap distances between the pulleys were also measured. The results obtained from the present study may be helpful in surgical treatment of trigger thumb with less complication and also in reconstruction of the closed rupture of the pulley of the thumb.

MR imaging findings of trigger thumb

Trigger finger (or trigger thumb), also known as sclerosing tenosynovitis, is a common clinical diagnosis that rarely presents for imaging. Because of this selection bias, many radiologists may not be familiar with the process. Furthermore, patients who do present for imaging frequently have misleading examination indications. To our knowledge, magnetic resonance (MR) imaging findings of trigger thumb have not been previously reported in the literature. In this article, we review the entity of trigger thumb, the anatomy involved, and associated imaging findings, which include flexor pollicis longus tendinosis with a distinct nodule, A1 pulley thickening, and tenosynovitis. In addition, in some cases, an abnormal Av pulley is apparent. In the rare cases of trigger finger that present for MR imaging, accurate diagnosis by the radiologist can allow initiation of treatment and avoid further unnecessary workup.

Varied anatomy of the thumb pulley system: implications for successful trigger thumb release

PURPOSE

The anatomical arrangement of the thumb pulley system continues to be revised through ongoing investigative research, changing our previous assumptions. This study demonstrates the components and anatomical features of this pulley system in an effort to improve surgical outcomes and to clarify current misconceptions.

METHODS

Researchers procured 75 hand specimens from 41 adult cadavers through our institution's anatomical donations program. Dissections of the thumb and thenar compartment identified the various pulleys. A detailed analysis of the thumb pulleys was performed through various measurements.

RESULTS

Four different pulley categories were identified: type I (n = 5), type II (n = 29), type III (n = 29), and type IV (n = 12). The variable annular pulley was present in 70 of 75 hands (93%) in 1 of 3 arrangements: transverse, oblique, or fused with the A1 pulley.

CONCLUSIONS

The pulley system of the thumb is composed of 4 components, as opposed to the traditional view of only 3. Along with the A1 pulley, the additional variable annular pulley might contribute to stenosis in trigger thumb. This might necessitate a more extensive surgical incision and its partial release to relieve triggering.

CLINICAL RELEVANCE

Understanding the anatomical configuration of the thumb pulley system will aid in the surgical attempt to resolve triggering while avoiding complications such as bowstringing of the flexor pollicis longus tendon and iatrogenic nerve injury.

Failure of differentiation: Part II (arthrogryposis, camptodactyly, clinodactyly, madelung deformity, trigger finger, and trigger thumb)

The term "failure of differentiation" describes the phenotypes of a large number of otherwise unrelated conditions. The six conditions described here (arthrogryposis, camptodactyly, clinodactyly, Madelung deformity, trigger finger, and trigger thumb) are believed to occur because various structures failed to differentiate normally; however, they have neither common features nor a common cause. We have included information about the history and diagnosis of these conditions, the cause (if known), and the current concepts of treatment and expected outcomes.