Introduction

The upper extremities, especially hands, are body parts most commonly affected by injury [1]. It is estimated that a quarter of all injuries treated in the emergency department are related to the hand [2]. These injuries are usually seen in the young working age population employed in industrial plants, where workers are in direct contact with machines, but also in other professions, due to the more and more common, and very often inappropriate use of powered hand tools, most frequently circular saws. The circular saw is a round rotating electrical power saw, which, depending on the make and model, has 2,000 to 5,000 revolutions per minute (RPM) [3]. It is used in industry, but it is also freely available retail, and can be used at home, without any previous training. These are high-energy type injuries, which are a common cause of severe damage to the hand, with significant simultaneous damage to different tissues (Figure 1), which in 57% of cases lead to amputation [4].

Figure 1 Povrede šake zadobijene cirkularom / Circular saw injuries to the hand

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These injuries are of great socioeconomic significance, due to primary treatment costs (costs of surgery and hospital treatment), but also to secondary costs (lost wages, vocational retraining, and disability, as well as a long rehabilitation period) [5][6][7].

Materials and methods

This is a retrospective study carried out at a single medical center, between 2017 and 2021. A total of 365 patients, who had sustained circular saw injury to the hand, wrist, or forearm, were treated at the Department of Microsurgery and Reconstructive Hand Surgery of the University Clinical Center of Serbia. Injuries inflicted by other machines were excluded from the study. The demographic patient data – age of patient at the time of injury, sex, and occupation, were collected from the patient medical records (patient admission report and discharge summary). Data on the localization and type of injury, dominance (handedness) of the injured hand, the type of surgical procedures performed, and the length of hospital stay, were also collected. Additionally, data on the way that the machine was operated and on previous training pertaining to circular saw handling, were recorded.

Statistical analysis produced results on the arithmetic mean, maximum and minimum values, standard deviation, and the frequency expressed in percentages.

Results

Of the 365 patients injured by the circular saw, in the observed five-year period, there were 350 (95.8%) male and 15 (4.2%) female patients. The average age was 48.6 ± 14.71 years, with the age range of 17 to 88 years. Most of the patients sustained their injury at home (83.2%), while a significantly smaller number of persons (16.7%) was injured at their workplace. The structure of the patient sample was as follows: 146 (40%) manual laborers, 80 (21.9%) agricultural workers/farmers, 22 (6.05%) high-school and college students, 117 (32.05%) old-age pensioners. The left non-dominant hand was most commonly injured, in 56% of cases. The right dominant hand was injured in 34% percent of cases, while the right non-dominant hand and the left dominant hand were injured much less frequently (6% and 4% of cases, respectively). Most frequently the injury was to one finger (35.1%), predominantly the thumb (68.4%), followed by injury to two fingers (32.7%), while three fingers were injured in 20% of the cases. Hand injury occurred in 7.27% of cases, and forearm injury occurred in 5.45% of cases. Isolated injuries to only one structure were quite rare, only in 12.5% of patients. The injury localization is presented in Table 1.

Table 1. Lokalizacija povrede / Injury localization

Lokalizacija povrede / Injury localization	Prsti / Fingers
Jedan prst / One finger	I 86	II 26	III 7	IV /	V 7
Dva prsta / Two fingers	I + II 33	II + III 53	I + III 7	III + IV 13	IV + V 13
Tri i više prstiju / Three or more fingers	I – III 13	I – IV 7	II – IV 20	II – V 27	III – V 6
Šaka / Hand	27
Podlaktica / Forearm	20

The most commonly injured structures were extensor tendons (245), followed by phalanges (226). In all injuries, whether the damage was done only to the tendon or to the bone as well, injury to one or both digital nerves occurred, while, at the level of the wrist and forearm, damage was done to the nervus medianus, the nervus ulnaris, or both. The details on the damaged structures are presented in Table 2.

Table 2. Distribucija povređenih struktura / Distribution of injured structures

Struktura / Structure
Ekstenzorna tetiva / Extensor tendon	EPL 66	EDC II/ EIP 46	EDC III 40	EDC IV 20	EDC V/ EDM 13	EKSTENZORI PODLAKTICE 60
Fleksorna tetiva / Flexor tendon	FPL 46	FDS/FDP II 73	FDS/FDP III 40	FDS/FDP IV 20	FDS/FDP V 7	FLEKSORI PODLAKTICE 20
Metakarpalna kost / Metacarpal bone	I 29	II 22	III 7	IV 8	V 5
Falanga / Phalange	I 73	II 74	III 52	IV 23	V 4

EPL – extensor pollicis longus; EDC – extensor digitorum communis; EIP – extensor indicis proprius; EDM- extensor digiti minimi; FPL – flexor pollicis longus; FDS – flexor digitorum superficialis; FDP – flexor digitorum profundus

All patients were surgically treated. In total, 995 procedures were performed. The most commonly performed operation was tenorrhaphy (44.67%), followed by fracture fixation (29.3%). Finger reamputation was performed in 6.67% of cases, neurorrhaphy in 6%, and tendon reinsertion in 4% of cases. There was a total of 46 replantations (4.67%), and 27 revascularizations (2.67%). Skin defect was covered by a split-thickness skin graft in 2% of cases. The average length of hospital stay was 9.04 ± 3.91 days, with a range of 3 to 29 days.

Discussion

There were 95.8% of male patients in our study. The absolute dominance of the male sex can also be found in other studies, with similar percentages [1][4][8]. This is explained by the fact that men more commonly hold jobs that involve the use of powered hand tools. The average age of the patients involved in the study was 48.6 ± 14.71. In studies by other authors, we found similar data: 46.8 and 47 years [4][8]. Only in one study did we find data on a significantly younger average age (31.24 years), which predominantly depends on the age structure of the population of a particular country [1].

A relatively small number of persons (16.7%) sustained their injury in the workplace. The majority of injuries was sustained in the home (cutting wood in rural households, amateur woodwork, or less frequently a hobby). Almost the same ratio can also be found in literature [9]. This difference can be attributed to the fact that people working in industry have been trained to work with these machines. When collecting data on previous training for operating a circular saw, all of the patients belonging to the second group stated that they had undergone no such training.

When we look at the frequency of injury to the left and right hands, the left hand was more commonly injured (60%). This can be explained by the fact that, when working with the circular saw, the dominant hand holds the machine, while the non-dominant hand holds the material being cut, near the blade, which is in correlation with the results presented in the study by Hassine et al. [1]. The population of Serbia is predominantly right-handed [10]. When working with table circular saws, both hands are at equal risk [9]. In the same way, the highest incidence of thumb injury is explained (when only one digit is injured, thumb injuries account for 68.4% of such cases), as is the incidence of injury to the radial side of the hand, when two fingers are injured (78.1%). When working, these fingers are closest to the blade [4]. The injury to one digit, the thumb and the radial side of the hand, is also stated by other authors [4][5][9].

Of all the structures, tendons were the ones most commonly injured – approximately equally extensor and flexor tendons (245 versus 206). Other authors also reported a high incidence in tendon injury, especially extensor tendons [1][11]. The most frequently performed surgical procedure was tenorrhaphy (44.67%), followed by fracture fixation (29.3%). The total number of reamputations was 66 (6.67%), while in a different study, it was found that reamputation was, in fact, the most frequent primary procedure [1]. Whether reamputation or replantation is to be performed, depends on the level and severity of the injury, but also on the availability of specialized tertiary institutions. Most frequently, reamputation of the second and third finger was performed (60%), as is also reported in the study by Hassine et al. [1]. Replantation of the fingers and the hand was performed in 4.6% of the cases (46 patients), (Figure 2).

Figure 2 Replantacija drugog i trećeg prsta / Replantation of the second and third finger

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Figure 3 Široka zona povrede sa elementima avulzije / Wide zone of injury with elements of avulsion

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Bearing in mind the nature of the wound itself, which includes avulsion and a wide tissue injury zone (Figure 3), as well as the damage to fine neurovascular structures, surgical treatment, in the sense of replantation, may pose a significant challenge.

Conclusion

Due to the very nature of the tool itself (high RPM and sharp blade), operating a circular saw is a high-risk activity. The injuries sustained are extremely severe, they can cause significant functional deficit, and they also have great socioeconomic impact. Lack of previous training on how to properly operate the machine and the misuse of this tool, resulting from the removal of the protective parts of the machine, represent obvious risk factors for injury. The clinical and epidemiological analysis of the injuries is, therefore, exceptionally significant, as it can be the key to preventing these injuries.

Dodatak

Conflict of interest

None declared.