Remnant foreign bodies in the hand can be more than just a nuisance; they are often a significant cause of morbidity [1]. Prompt identification and removal of such foreign bodies are crucial since retained foreign bodies lead to late complications, such as infection or functional disability [2-4]. Therefore, in most cases, the removal of foreign bodies in soft tissues is warranted.

Soft tissue foreign bodies in the hand are sometimes dismissed as simple injuries, but accurate location and removal of them can be more clinically challenging than expected [5]. While numerous research studies have concentrated on strategies for pinpointing the location of foreign bodies, not many have provided detailed extraction techniques [6,7]. An experienced operator and specific localizing tool are mandatory in foreign body detection and removal. To remove soft tissue foreign bodies, many surgeons have made an elliptical incision roughly around the wound entry, and removed them en bloc, including the adjacent skin and soft tissues [2,5,8,9]. Although this procedure might be simple and straightforward, enduring surrounding soft tissue injury is inevitable. To minimize such damage, certain surgeons have attempted to remove foreign bodies in the hand with needle-guided technique, or using magnetic forceps [1,10].

In this study, we describe the microscope-assisted removal of foreign bodies in soft tissues with presenting intraoperative video clips. By microscopy, we could detect and remove foreign bodies exactly and safely regardless of their type, with minimal soft tissue exploration and dissection.

We conducted a retrospective review of the medical records of patients treated for foreign bodies in the hand in our department from July 2013 to May 2023. The analysis included various parameters, such as the cause of trauma, time interval from trauma to surgery, location, type, size, number of foreign bodies, patient complaints, imaging technique, and procedure types. Preoperative examinations comprised neurologic and functional tests to assess potential damage to muscles, tendons, and nerves resulting from the injury. Additionally, preoperative X-ray and ultrasonography were performed as needed.

To establish a bloodless field, a tourniquet was applied to the patient’s upper arm, followed by the administration of local anesthesia. A slit incision was then made over the suspected site of the foreign body. Under the microscope, we initially identified unhealthy granulation tissues beneath the surgical incision site. Upon locating these tissues, we gradually dissected around them and traced the location of the foreign body. Exploration of the wound was carefully performed to minimize adjacent soft tissue injuries. Complete removal of the foreign bodies was achieved using micro forceps. Finally, the incision site was safely closed with a horizontal mattress suture technique, using nylon 4−0.

A total of 16 patients aged 23 to 55 years were included in this study (Table 1). There were six male and 10 female patients. The most common cause of trauma was stab injury, which accounted for 13 cases, followed by abrasion, traffic accident, and bee sting in each case. The mean interval from the occurrence of trauma to surgical intervention was 21.1 days, with a range spanning of 2–60 days. The most affected regions in the hand were the middle finger and thumb, which comprised five and four cases each, followed by three cases of the index finger, two cases of the little finger, and one case each of the ring finger and palm. The extracted foreign bodies were glass in six cases, wood in four case, seashell particles in two cases, and fish bone, pencil tip, bee sting, and aluminum foil in one case each. The foreign bodies were sized 1 to 20 mm in length, and less than 3 mm in 13 cases. In three cases, the foreign bodies were multiple ranging from two to 14 bodies; otherwise, they were single. The chief complaints of patients included sensation of foreign bodies and pain in nine cases, swelling in three cases, and discoloration and skin lesions in one case each on previous injury sites. We checked by X-ray in all cases and an additional ultrasonography in five cases. We explored the injury site safely under the microscope in all cases.

Patients with foreign bodies in the hand present various symptoms, such as localized hump, pain, swelling and numbness. The exact localization and removal of foreign bodies are important because untreated remnants might cause late infection, chronic pain, or sustained neurologic symptoms, such as numbness of the injured site [2,3,4]. Also, retained foreign bodies could migrate from the original injury site, causing severe neuropathy [11]. Therefore, removing foreign bodies in the hand is important and challenging, because not only are such bodies difficult to detect, but it is also not easy to remove them without injuring the surrounding soft tissue.

Foreign bodies in the hand, compared to other parts of the body, are typically small, and challenging to detect and remove completely. While the microscope-assisted removal of foreign bodies has been explored in the field of otolaryngology and ophthalmology, its utility is limited, as the use of endoscopes may suffice [12,13]. Many hand surgeons still opt for en bloc excision for simplicity, despite the importance of precise removal without injuring the surrounding tissues. Some hand surgeons still seem to be hesitant to use microscopes and prefer alternative tools, like fine needles [1,8], magnets for metallic foreign bodies [10], special tooth-like forceps [10], slit lamps [14], Hartmann alligators [2], and Halsted mosquito forceps [2]. Although microscope-assisted removal offers advantages over en bloc excision, it is not commonly practiced, even among experienced hand surgeons, due to the burden of using delicate micro-instruments. Some surgeons even suggest that patients leave non-troublesome foreign bodies untouched.

Various diagnostic tools have been applied to detect foreign bodies in the hand, such as X-ray, ultrasonography, computed tomography, and magnetic resonance imaging [2,5,6]. Among them, the use of ultrasonography has been the golden standard for detecting soft tissue foreign bodies, as it has a sensitivity and specificity of (90 and 96) % respectively [2,8,15,16,17]. In our previous study, we placed a 26-gauge needle on the injury site to make a two-dimensional marking, which helped us detect the very small foreign body before a surgical approach [18].

In technical view under a microscope, locating and tracing the unhealthy granulation tissue is the key point in our procedure. Considering that the patients visit the clinic a few days or weeks after the accident (an average of 21.1 days in our study), the tissues of the body have a tendency to form a barrier with the squashed tissue, which is easily discernible from the adjacent normal tissue under the microscope. In our case 3, the foreign body was palpated as a short cord-like twig in the physical exam. However, we could completely remove the deeply penetrated sharp wig with very small particles. Furthermore, even the dark spot-like bee sting, which measured 0.3 mm, could be completely removed under the microscope, which has not previously been reported in the literature (Fig. 1C).

Surgical removal of foreign bodies in the hand has potential complications, such as neurovascular injury during the dissection, or later scar formation on the incision site [19]. However, in a microscopic setting, we could perform the most accurate and minimally invasive procedure to remove the foreign body in the hand. In one case of our study, the patient requested temporary digital paresthesia, the reason for which we suspected to be the finger tourniquet that we applied during the surgery. Therefore, we do not recommend a total surgery time of longer than 1 hour under a tourniquet, because it might cause permanent neurological complications, such as complex regional pain syndrome.

Our study has some limitations. First, the sample size may not be enough to make a standard guideline. Second, setting up a microscope for microsurgery may not be easy in many institutions. Third, even under microscopic assistance, only a skilled surgeon may be able to detect and remove foreign bodies. Fourth, this is a single-institution study, and all cases were performed by a single surgeon, so there might have been bias.

The successful detection and removal of foreign bodies in the hand have been primary concerns for many surgeons, with numerous studies exploring different methods of detecting residual foreign bodies, without delving into specific removal techniques. Despite the prevalent practice among hand surgeons to opt for en bloc excision or conservative management, we propose that the use of microscopes for the detection and removal of foreign bodies in the hand may offer the most precise and least invasive approach, combining efficiency with safety. By embracing microscope-assisted techniques, surgeons can enhance the accuracy of foreign body removal procedures, while minimizing collateral damage to the surrounding tissues, ultimately improving patient outcomes in hand surgery.