The loss of a needle during minimally invasive surgery is rare, but when it occurs, it becomes an emergency that can seriously affect patients’ lives. The recovery of lost needles has been described in the literature.Reference Macilquham, Riley and Grossberg1

The best strategy to avoid such accidents is prevention. However, once lost, there are no established protocols for searching for a lost needle. The incidence ranges between 0.06 per cent and 0.11 per cent,Reference Jayadevan, Stensland, Small, Hall and Palese2,Reference Barto, Yazbek and Bell3 and surgeons who perform minimally invasive surgery face this complication one to five times on average during their professional careers.

Because of the complex manoeuvres with endoscopic suturing, the risk of losing a needle is highest in abdominal procedures (50 per cent of cases), followed by gynaecological and urological procedures.Reference Medina, Martin, Cacciamani, Ahmadi, Castro and Sotelo4 Associated factors increase the frequency of this complication (Table 1). Therefore, the most effective measure continues to be prevention.Reference Zaman, Clarke and Schofield5

Table 1. Factors associated with needles lost during surgery

Conventional radiology remains the ‘gold standard’ for detecting lost surgical instruments.Reference Macilquham, Riley and Grossberg1,Reference Sharma, Mete, Bendapuddi, Bora and Mavuduru6–Reference Ponrartana, Coakley, Yeh, Breiman, Qayyum and Joe8 Here, we evaluate the effectiveness of a high-sensitivity metal detector compared with conventional radiology for locating a needle lost during ENT surgery.

We conducted an experiment to locate lost needle fragments (Stratafix™ size 2-0 and V-Loc™ size 9-0 suture needles) on a lamb's head using a high-sensitivity metal detector (model IP-68; Inkbird Plus, Shenzhen, China) (Figure 1).

Figure 1. High-sensitivity metal detector (model IP-68; Inkbird Plus, Shenzhen, China).

The weights of the three needle fragments, which had been cut with pliers, were measured using a digital scale (Alfresco, Jiangsu, China) (Figure 2); these were inserted 1 cm inside the posterior two-thirds of the lamb's tongue. Depth was measured with a digital tyre gauge (Katsu Tools, Harrow, UK) (Figure 3).

Figure 2. Different sizes of surgical needle fragments are weighed on a digital scale.

Figure 3. Depth measurement with a digital tyre gauge.

Three senior otolaryngologists (with more than 10 years of experience) and three junior surgeons (with less than three years of experience) attempted to locate the needle fragments using a metal detector (Appendices 1 and 2) or X-rays (Figure 4). The fragments were hidden three times for each different weight with each procedure. The time it took each surgeon to locate the remnants with each technique was recorded (Tables 2–5).

Figure 4. X-ray of a lamb's head with a surgical needle fragment in its tongue.

Table 2. Junior surgeons using metal detector for needle fragment detection

Table 3. Experienced surgeons using metal detector for needle fragment detection

Table 4. Junior surgeons using X-ray for needle fragment detection

Table 5. Experienced surgeons using X-ray for needle fragment detection

The metal detector measures 26.5 cm in length and is made of plastic. It is easy to use and transport, unlike an X-ray machine. It has a durable IP66 design that makes it waterproof; therefore, in the case of blood or other liquid spills, there should be no technical problems. The metal detector has audible and vibrating alarms to indicate the presence of metal objects, and is equipped with a protective cover and an accessory hook that help prevent its loss. Its power source is a 9 V battery that must be purchased for use. The working temperature is between –10°C and 30°C. The metal detector is easy to obtain in the domestic market.

Quantitative variables were assessed by calculating the arithmetic mean and standard deviation values. Group differences were assessed using a two-sample paired t-test, or a Mann–Whitney U rank sum test if the variable was not normally distributed. A p-value of less than 0.05 was considered significant. SPSS Statistics for Windows software (version 20; IBM, Armonk, New York, USA) was used for statistical analysis.

The three junior ENT surgeons detected the needle with the metal detector in an average time of 5.03 ± 1.8 minutes, which included the time needed to use the mouth opener and bring the instrument close to the anatomical location (Table 6). The average time taken by these surgeons to move the X-ray equipment and take radiographs was 13.7 ± 2.8 minutes (p < 0.005).

Table 6. Time taken for junior surgeons to detect needle fragments and significance level between techniques

In contrast, the three experienced ENT surgeons detected the needle remnants using the metal detector in an average time of 3.6 ± 1.2 minutes (Table 7). The time taken for these surgeons to detect the foreign body with X-ray was 12.6 ± 2.8 minutes (p < 0.001).

Table 7. Time taken for experienced surgeons to detect needle fragments and significance level between techniques

To our knowledge, this is the first study investigating the use of a metal detector to identify a lost needle during surgery compared with radiology. In cases involving a lost needle, minimally invasive surgery is the first-line procedure.Reference Möhrenschlager, Ring, Henkel and Jessberger7 Given the delicate anatomy of the upper airways and the importance of their functions, lost needles must be located quickly and effectively. Some studies have reported that the detection sensitivity rate of imaging studies inside the operating theatre is strongly correlated with needle size. The X-ray detection sensitivities for needles sized 11–24 mm and those over 25 mm are 85 per cent and 99 per cent, respectively; however, it is only 29 per cent for needles sized 4–10 mm.Reference Jayadevan, Stensland, Small, Hall and Palese2,Reference Ponrartana, Coakley, Yeh, Breiman, Qayyum and Joe8

The main problem with radiology is the time spent before use to prevent excess radiation exposure to patients. This can lead to increased costs and medical resources. Radiology is also associated with increased operating time and anaesthesia time, and the transport of equipment and personnel for performing the X-rays.

Several step-by-step protocols for optimal needle recovery have been described in the literature,Reference Jayadevan, Stensland, Small, Hall and Palese2,Reference Sharma, Mete, Bendapuddi, Bora and Mavuduru6 but none of these protocols includes the use of a metal detector by the surgical team. However, Jayadevan et al. Reference Jayadevan, Stensland, Small, Hall and Palese2 reported that the effectiveness of articulated magnetic recovery devices, such as the ConMed Magnetic Retriever (ConMed, Utica, New York, USA), can increase recovery speed by up to 10 times.

• Lost and broken needles in upper airway surgery necessitate halting the surgery to search for the missing pieces, given the significant morbidity if not recovered

• To date, only conventional radiology recovery has been used, but this involves additional time and transport of equipment during surgery

• Modern metal detectors are useful for detecting this foreign body; they save time for the surgeon and avoid radiation to the patient

• The authors’ experience is satisfactory, and metal detectors are present during all upper airway surgical procedures

Instruments that can locate a lost needle fragment are needed because such occurrences remain controversial, and the possible health consequences for the patient, as well as the legal implications for the surgeon, remain a concern. If a needle is large enough to cause a serious injury, it should be identified on a simple X-ray.Reference Small, Gainsburg, Mercado, Link, Hedican and Palese9 However, needles often break, leaving only remnants in the body; these can be identified using computed tomography (CT), especially if they are embedded within an organ.Reference Barto, Yazbek and Bell3 The disadvantages of this approach include the impossibility of performing CT at the time of intervention and the associated exposure to high radiation.

The main limitation of this study is that it was carried out on an animal corpse; thus, the anatomical variations between lambs and humans are a concern. For ethical reasons, this study is difficult to perform on humans. The personal experience of the authors using a metal detector is satisfactory, and this device is always present in the operating theatre when oral surgery is performed.

The loss of a needle during surgery remains a possibility, and prevention is crucial. The present study suggests that a metal detector can be a useful tool for locating a needle lost during ENT surgery because it requires less time than conventional radiology to use and avoids exposing patients to radiation.