Nerve trauma of the lower extremity: evaluation of 60,422 leg injured patients from the TraumaRegister DGU® between 2002 and 2015

Trauma of the upper and lower extremity is often combined with additional peripheral nerve injury (PNI). In a single-center study 920 out of 5721 patients with injured extremities suffered from associated nerve lesions with the need of nerve specific surgical procedures like suture or grafting [1]. In another series PNI could be detected by clinical examination and electrodiagnostics in 34% of patients with traumatic brain injury during the postacute care [2]. According to an investigation from the Iran National Trauma Registry database (n = 16,753 patients) 1,3% of all trauma victims suffer from PNI, but this proportion may be dependent from the socioeconomic context [3]. The situation in European countries with distinct conditions and regulations might be different and has not been elucidated in detail by now despite of its high therapeutic relevance and diminished quality of life resulting from reduced functional capacity, pain (e.g. from neuroma) and subsequent psychological impairment associated with peripheral nerve conditions [4‐6]. The objective of this study is to clarify the frequency and characteristics of nerve trauma in a large European cohort of 60,422 leg injured patients. The provided data may guide the clinician to detect nerve lesions in trauma victims presenting with certain risk factors earlier which could eventually improve their functional outcome.

All epidemiological data presented in this investigation were retrieved from the TraumaRegister DGU® (TR-DGU). The present study is in line with the publication guidelines of the TraumaRegister DGU® and registered as TR-DGU project ID 2016–014.

We evaluated 60,422 lower extremity injury cases from the above mentioned registry encoded between 2002 and 2015. A detailed comparison between leg trauma patients without recorded nerve damage (control group) and those with lower limb peripheral nerve injuries (PNI group) was made. Injuries of the lower extremity can be identified by an Abbreviated Injury Score (AIS) beginning with number 8. Only lesions with a minimum AIS grade of 2 were considered. By implementing this specification the inclusion of patients presenting only minor lesions of the legs was prevented. All involved trauma cases were registered in Germany (87,6%) or other European countries contributing to the TR-DGU. Additional detailed information about the registry itself and all currently participating countries is available at the TR-DGU website (www.​traumaregister-dgu.​de). We excluded data from non-European nations, because the determined purpose of this study is to provide information related to lower extremity nerve damage in the European socioeconomic context. All assessed cases suffered from at least one injury rated with a maximum AIS of 3 or higher. This limitation ensured that every involved leg trauma patient sustained at least one major lesion. Furthermore we suspended all registered admissions from analysis which were transferred to another hospital in the early posttraumatic period up to 48 h to eliminate systematic double assessment. Sixty thousand four hundred twenty-two individuals complied with the requirements and therefore could be included in this clinical investigation. All patients were evaluated for age, gender, trauma mechanism, injury severity scale (ISS), peripheral nervous system involvement, further involved anatomical structures (soft tissue, bones, joints, vessels) and severely affected body segments (head, thorax, abdomen, extremity). Due to the coding practice of the TR-DGU leg amputations were not classified as nerve lesions. A relevant injury to a specific body segment was defined as AIS > = 3 points. Additionally we report on nerve focused surgical procedures, ICU treatment, duration of hospital stay and Glasgow Outcome Scale (GOS) after discharge from the hospital. Injuries of the peripheral nervous system were classified into femoral, sciatic, tibial, peroneal and toe nerve lesions. Variables were analyzed using descriptive statistics (percentages and frequencies) and central tendency measures (mean and median). For small subgroups and pivotal findings the 95% confidence interval (CI) is additionally provided in parentheses.

The purpose of this study was to elucidate epidemiological patterns and characteristics of lower extremity nerve trauma in Central Europe by retrospective analysis of 60,422 leg injured patients entered into the TR-DGU database between 2002 and 2015. This investigation suggests concomitant PNI in 1,8% of patients suffering from lower extremity injury. Physicians may attend vital threats at first in situations with life threatening polytrauma or head injury which could possibly lead to underreporting of extremity lesions including nerve damage [7], but after primary stabilization of vital functions a detailed secondary survey including nerve function is mandatory according to the TR-DGU protocol which may reduce diagnostic failure. Our findings are in line with the results of other studies from various regional and socioeconomic settings which referred nerve lesion rates between 1 and 3% of all patients admitted to trauma hospitals [3, 8‐11], whereas an investigation of children suffering from traumatic brain injury revealed electrodiagnostically confirmed peripheral nerve damage in 7% of cases [12]. There was a predominant proportion of male PNI patients in this study (80%) which is congruent with the majority of previously performed trials [2, 3, 8, 11, 13‐15], but there are also exceptions with almost equal distributions between both sexes [16]. On the average PNI patients in our study were significantly younger compared to the control group (38,1 years vs. 46,7 years). This correlation agrees with the findings of the retrospective cross-sectional study performed by Saadat et al., where PNI trauma patients revealed a significant lower mean age than their counterparts without nerve damage (PNI 28,6 years; non-PNI trauma 33 years) [3]. Eser et al. refer a mean age of 31,8 years for 938 patients with PNI [14]. Generally younger patients are considered to be more vulnerable regarding nerve injury [11, 17, 18]. Our research suggests peroneal (51%) and sciatic nerves (25%) being the most frequently affected neural structures in lower extremity trauma which is supported by other trauma studies and the UVG database [9, 18, 19]. The more superficial anatomical position of the peroneal nerve could eventually lead to a surpassing trauma rate, whereas the femoral and tibial nerves may take advantage of a beneficial anatomical course [20]. A Mexican single-center series and a cross sectional study of earthquake victims exposed the sciatic nerve being the most frequently injured major nerve of the lower limb [11, 17]. In our study patients with PNI revealed a mean ISS of 22,7 compared to an average ISS of 22,1 in the control group. These results are in harmony with the mean ISS of 23,1 noticed in 162 PNI patients by Noble and colleagues, but they contradict the findings of Saadat et al. who reported lower scores for PNI trauma patients (ISS 5,5) and their counterparts without nerve involvement (ISS 7,1) [3, 8]. Only patients showing at least one lesion with an AIS of 3 or higher were included into this investigation according to the predefined inclusion criterion which could possibly contribute to generally increased ISS compared to the results of the aforementioned study. Registered ISS of this study were slightly inferior to those of pedestrian traffic collision victims (ISS 26,2) and motor vehicle passengers (ISS 25,4) in a study performed by Reith and colleagues [21]. This study suggests higher proportions of bone fractures, joint dislocations and vessel ruptures for PNI compared to the control group, as presented by Fig. 2. Garozzo et al. report on 72 patients with lumbosacral plexus lesions who suffered from additional bone damages in 83% and vascular lesions in 8% [15]. Kim et al. describe fractures to be the cause of sciatic nerve injuries in 17%, peroneal nerve lesions in 7% and tibial nerve damages in 41% in their surgical series [22‐24]. About one out of three patients with peroneal dysfunction following knee dislocation or traumatic sciatic neurotmesis sustain concomitant vascular injuries [25, 26]. Levy et al. report on the strong linkage between PNI and orthopaedic trauma including fractures in patients undergoing skiing and snowboarding accidents [27]. The PNI patients of our series had less additional head injuries than their counterparts (PNI 15%; control 27,5%). This outcome is distinguished from the results of Noble et al., which mention head injury rates of 60% in a PNI population [8]. The difference may be explained by our limited focus on PNI patients with lower extremity trauma. Data analysis from the TR- DGU highlights different injury mechanisms for both investigated cohorts. Leg trauma without nerve damage is more commonly associated with falls (control group 29,8%; PNI group 14,4%), whereas nerve injury seems to be more often a consequence of motorcycle accidents (control group 18,5%; PNI group 31,2%) and penetrating trauma (control group 3,2%; PNI group 7,9%). The correlation between penetration and nerve injury is supported by other studies dealing with PNI [3, 28]. 60% (21%) of lumbosacral plexus lesions were categorized as consequences of car crashes (motorbike accidents) by Garozzo et al., whereas only 6% of these injuries were due to falls [15]. Uzun et al. also report on traffic accidents as the main cause of nerve injuries [29]. Another study denominates nerve trauma as a result of motor vehicle collisions in 39,7% and gunshot wounds in 32,4% which underlines the significance of environmental factors regarding PNI [13]. PNI and control patients were characterized by similar ISS scores which suggests a comparable overall trauma severity for both cohorts. This creates a common basis concerning consecutive outcome measurement. The analyzed database provides information about GOS, duration of hospital stay and need for further rehabilitation therapy after discharge. GOS was analogous in both groups, but this score alone could be considered as an inappropriate parameter for comparison because of its intrinsic nature as an outcome measure after brain damage [30]. However, the majority of cases in our study did not sustain a severe head injury. Good outcome represented by GOS grade 4 or 5 signifies physical independence regarding activities of daily living which may be reached by plenty of patients with PNI despite of their burden caused by neuroma associated pain, stress and diminished health related quality of life [4, 6]. Intiso et al. found comparable good functional recoveries after intensive rehabilitation for multiply injured patients with and without PNI measured by Barthel and mRS scores [31]. More suitable comparative parameters could be the duration of hospital stay and the need for further rehabilitation after discharge. PNI may lead to immobilization promoting prolonged inpatient stay and increased rehabilitation treatment rate which causes extended periods of absenteeism with associated detrimental economical and social consequences. In our study both parameters were distinctly increased within the PNI group which is an important finding for the individual patient and also for the healthcare system. Our results are congruent with the swiss accident statistics database analysis from 1997 and other series which identified nerve trauma as a costly lesion associated with a higher risk for loss of productivity compared to injuries without nerve damage [31‐34]. Besides of the merits of this multi-centre study concerning standardized evaluation of a large number of patients comprising all age groups from different European countries the main limitation results from its retrospective character. The TR-DGU primary focuses on major trauma management which could eventually contribute to a significant underreporting of non life-threatening injuries. Therefore our presented data concerning PNI incidence rates should preferably be regarded as lower limit values for patients with significant leg injuries. Additionally total PNI incidence rates cannot be extracted from the TR-DGU database, because minor PNI lesions without admission to hospital via emergency room are beyond the scope of this registry.

Peripheral nerve injuries apparently affect about 1,8% of patients with significant lower limb trauma. In this study the most frequently afflicted neural structure was the peroneal nerve. Our study reveals an increased likelihood for young male patients to suffer from nerve involvement. The dimension of global injury severity in leg trauma patients appears to be independent of an additional nerve damage, but individuals with involvement of the peripheral nervous system generally show a different pattern of accompanying lesions, an extended inpatient stay and a higher need for subsequent rehabilitation. The most common causes of PNI in this central European based study were motorbike and car accidents, whereas lower extremity trauma without nerve damage seems to be mainly associated with car accidents and falls.