Upper extremities are the most frequently injured body part and its peripheral nerves are easily severed by cutting or other traumatic injuries[1]. Consequently, the hand, our primary tool for environment interaction, is handicapped with potentially long-lasting deficits in a patient population that is generally young and healthy[2, 3].

Despite modern reconstructive surgery, in a significant number of patients a substantial loss of function remains[2–5]. This results from the key issues of slow or impaired nerve regeneration leading to delayed reinnervation with consecutive muscle fibrosis or painful neuromas at the site of injury. This is particularly prominent in proximal injuries, where the long regeneration distances between lesion and target organ represent a limiting factor for sufficient reinnervation[6–8]. Thereby results a considerable functional disability in the mostly young and previously healthy adult patients[2, 3, 9]. Consequently, nerve injuries are associated with long periods of recovery, sick leave and sometimes life-long functional disability[2, 10]. This is especially pronounced in work-accidents, where hands are easily injured during manual labor and thus life-long injury compensation from health-care providers may result.

So far, there are only cost analyses from small patient cohorts of Sweden and Switzerland, but none from a German collective [10, 11]. For this purpose, we analyzed data of treatment, rehabilitation and long-term compensation for work related accidents from the workers’ compensation termed the “German Social Accident Insurance” (Deutsche Gesetzliche Unfallversicherung) [12]. The aim of this system is to provide optimal treatment to those injured while working and ensuring their ability to return to work. In this study, we analyzed data on a unique set of 250 consecutive German patients treated for 268 nerve injuries. To our knowledge, it thus provides the first complete analyses of injury data, treatment costs, duration of rehabilitation and long-term socioeconomic results including life-long compensation for remaining health deficits in a large patient cohort. This analysis is therefore the biggest patient collective showing the substantial long-term effects and costs of nerve injuries of the upper extremity.

Ethical approval was obtained from the German Federal ministry of work and social affairs (AZ: Iva1-41735-75) to obtain all patient data from the German Social Accident Insurances, without the need for additional approval of individuals. Therefore, and due to the anonymous patient data analyses, no individual patient consent was sought. Patients were identified by ICD Code (G56.2, G56.3, S54.0, S44.0, S64.0, G56.3, S54.2, S44.2, S64.2, S54.0, S54.1, S64.1, S44.1, S44.4) and/or OPS search (5–044.1–4, 5–045.1–4, 5–046.1–4, 5–047.1–4, 5–048.1–4, 5–049.1–4, 5–0580.1–4, 5–051.1–4, 5–052.1–4, 5–053.1–4, 5–054.1–4, 5–055.1–4). Thereby, all patients with work-related traumatic nerve lesions of the upper extremity between 2012 and 2016 treated at the BG Trauma Center Ludwigshafen were included in the analysis. Included were primary nerve injuries located from shoulder to the fingertip, without brachial plexus injuries. Secondary nerve injuries following fractures or iatrogenic nerve injuries were excluded. Cost refunding was according to standard health treatment compensation of the German Social Accident Insurance system, which is based on the diagnosis related groups system (DRG). Cost-analyses therefore present the sum of revenues that the system provided for the treatment of patients. Patient data acquisition was done by two independent reviewers (KB, LGH) from the hospital information system in a pseudonymized manner. Data on follow up was provided on request by the German Social Accident Insurance on all included patients. This was the reason for exclusion of private injuries, since the health insurances do not provide follow-up data for research causes. The follow-up for post-acute treatment was at least 78 weeks following injury, which is considered the standard for work-related accidents in Germany. At this time, patients undergo evaluation if they suffer from a substantially reduced ability to work as a consequence of the work accident. If the patient was still undergoing treatment at that time, the follow-up was subsequently longer. The CHEERS (Consolidated Health Economic Evaluation Reporting Standards) Checklist was used as a guide for data reporting and manuscript design [13].

Peripheral nerve injuries of the upper extremity produce significant socioeconomic costs, regardless of location or clinical appearance[15, 16]. Even small injuries at the phalangeal level, especially at the thumb and index finger, can lead to significant morbidity and costs for initial treatment and if disabilities persist, life-long compensation. This is evident from our long-term costs-analysis, that indicated that 30% of patients suffering from work related traumatic nerve injuries had permanent disabilities and received financial compensation. Considering the current average life expectancy in Germany of this patient generation (1976) of 72 years [17] and their average age at injury being 39.9 years, this results in 32.1 years that have to be compensated with approximately 102.167€ per patient. Based on our calculations, these 30% of patients suffering from severe injury would total an overall socioeconomic burden of 138.798€ € for acute treatment, rehabilitation and life-long compensation or even 155.670€ when requiring gradual reintegration. This number will continually rise as life expectancy for Germans born in 2019 is calculated at 80.8 years, thus increasing overall compensation to 130.061€ and overall costs to 166.692€, if these patients were born in 2019[17].

While other traumatic injuries as for example polytrauma are generally more expensive[18, 19], it is the frequency of hand and upper extremity injuries and the subsequent risk of nerve injury that constitutes its socioeconomic importance, especially in work related accidents. In a recent analysis from the German Trauma Registry (TraumaRegister DGU®), 3.3% of all trauma patients (private and work accidents) with upper limb affection suffered from additional peripheral nerve injury, and in a subset of motor cycle injuries this increased to 32.5%[1]. This study likewise showed that trauma patients with nerve injury compared to equally injured patients without, had significantly longer primary hospital stay of on average six days and required more inpatient rehabilitation[1]. Both duration of stay and long-term rehabilitation were indicators for higher costs and associated with longer time off work. Studies from other countries found a similar epidemiology for populations of private and work accidents[20, 21], thus indicating that the results from our study may well be translatable to private accidents. Compared to other frequent hand injuries, as for example the distal radius fracture, the costs of nerve injuries are either comparable or often higher. For example, palmar plate osteosynthesis in distal radius fractures are approximately 10 to 30% less expensive than injuries to either of the three main nerves of the hand (even distal digital nerve injuries) in the German health system [22].

As a consequence of the socioeconomic costs, the German Social Accident Insurance has highlighted the importance of peripheral nerve injuries of the upper extremity by labeling all injuries to the main nerves and the digital nerves responsible for functionally-relevant hand sensibility (digital nerves 2, 3 and 10) as most severe type of injury[23]. These phalanges are at the same time the most-frequently injured ones[11]. In Germany, it is mandatory that all these injuries are treated at specialized trauma centers that are certified to provide the highest standard of care and specialization in peripheral nerve surgery in order to minimize the risk of long-term morbidity and secondary complications. This is an effort to reduce the high socioeconomic costs of nerve injury, as are for example caused by sick leave which was on average almost five months in this cohort. Furthermore, 26% of these patients required gradual reintegration for on average 21 days, until fit for full employment. Yet, it is important to highlight that 9% of our patient cohort had sick leaves extending beyond a year, and other studies showed ratios of up to 41%[2]. These long sick leaves may result from the majority of patients (60%) being injured in trades that are associated with manual labor, such as construction or the wood and metal industry. Thereby results the susceptibility to nerve injuries, especially at the hand or phalangeal level, while heavy objects or heavy machinery are operated on. Even a small injury with affection of a digital nerve and consecutively lost sensibility, or worse a lost ability to trust the sensibility or force production of the hand in more proximal injuries, is often a substantial obstacle to return to these professions. Thus, in 4% of cases, patients had to be reintegrated into a different work situation and 2% even underwent retraining to a profession feasible despite the sustained permanent disability. These numbers are comparable to a previous study from Sweden, where 8% of patients (private and work accidents) with digital nerve injuries were not able to return to their previous work[11]. Especially, while accompanying these patients through their treatment, surgeons witness the massive consequences of a hand not trusted or felt properly, and its secondary consequences on psychological well-being, private life and the fear of losing employment. Similar is the experience in permanently disabled patients that we see for determining their loss of function after the end of treatment, where the dire sequelae of even small nerve injuries are often most evident. Psychological consequences of nerve injuries have been well-studied and affirm these observations[4, 24, 25], and may sometimes incorrectly be interpreted as an exaggeration of a seemingly small injury.

The patient selection on work accidents in this study results from the very detailed analyses of these patients by the German Social Accident Insurance as well as providing these follow up data, which is not the case for private injuries. It may be considered as a limitation and difficulty to translating its conclusions to all patients. However, while focusing on work-related accidents may select certain aspects, the overall patient characteristics were very similar to other studies without this selection. Furthermore, these patients are well observed throughout their entire treatment and thus provide a unique and unified data set, that ultimately enabled this complex analysis. In addition, the selection of primary traumatic nerve injuries and the exclusion of secondary nerve injuries (fracture-related or of iatrogenic origin) provides a well-defined cohort, that would otherwise suffer from a very heterogenic patient population, such as for example long sick leaves due to fracture healing.

A very interesting aspect of this study is that predominantly peripheral nerves of the left hand were injured (60%). Studies indicate that more 80–90% of the population are right-handed[11, 26], thus leading to the assumption that the left injured hand was used to hold an object for manipulation in these cases. As a large number of nerve injuries were caused by electrical machines such as electrical drills or saws, where the non-dominant hand is used for securing the object, this further emphasizes this conclusion and highlights a potential for injury prevention. As our analyses indicate, there are specific tools and environments that have an increased risk for upper extremity nerve injury, which may be improved and thus the injury mechanisms preventable. European Hand surgery societies (FESSH) have started programs to raise awareness for the underlying causes of hand injuries and thereby prevent the before mentioned injury mechanism[26]. As these measures have only recently been introduced, their impact is yet unknown. Given the costs of nerve injury and the subsequent effects on patient’s ability to work, it is however very likely that funding towards prevention, specialized treatment and rehabilitation is well spent.

This study is the first to provide a detailed analysis of the associated costs of upper extremity nerve injuries in a large German population. Our data indicate high costs, long-term sick leaves and substantial permanent disability in the studied population for both, proximal and distal nerve injuries. This data is important to correctly assess the magnitude of such injuries and specifically provide knowledge on the economic and social consequences. Based on this information, new strategies on prevention and treatment can be developed and thus help to define specific guidelines for peripheral nerve injuries of the upper extremity.