Necrotizing Fasciitis and Targeted Muscle Reinnervation in the Upper Extremity: A Case Report

Introduction

This case presents a unique instance of necrotizing fasciitis (NF) of the upper limb developing after minor trauma in a patient without identifiable risk factors. The progression to transhumeral amputation, followed by targeted muscle reinnervation (TMR), is a rare and singular presentation in the current literature.

NF is a deep, aggressive, and rapidly progressing soft tissue infection with the potential to result in significant morbidity, including limb loss or death. While its prevalence remains low, emerging evidence suggests an increasing incidence [1]. The condition predominantly affects the extremities, with the lower extremities being the most commonly involved. Upper extremity involvement is comparatively rare, accounting for approximately 10% of cases [2]. To the best of our knowledge, reports of upper extremity NF requiring TMR after transhumeral amputation remain scarce in the literature. Despite advancements in medical and surgical management, NF continues to be associated with a mortality rate of approximately 20% [2].

Several risk factors contribute to the development of NF, including diabetes, cardiovascular diseases, smoking, alcoholism, obesity, and intravenous drug use [3]. The disease is more common in men, with a male-to-female ratio of approximately 2: 1. Clinically, it presents acutely with systemic deterioration, fever, and, in some cases, altered mental status. Cutaneous manifestations can be absent in early stages, as the infection primarily affects deep soft tissues [2].

Given the high mortality associated with NF, a high level of diagnostic suspicion is essential, and treatment should be initiated early. However, the nonspecific nature of symptoms and signs often delays appropriate management. To aid in diagnosis, the Laboratory Risk Indicator for Necrotizing Fasciitis (LRINEC) score was proposed as a diagnostic tool for early detection [4].

In severe cases, amputation can be necessary to control the infection. Amputation significantly impacts patient function and quality of life. One of the major postoperative challenges is neuroma-related pain, which has led to the development of several surgical strategies. Traditional methods, such as neuroma excision and implantation into muscle, bone, or veins, have shown variable results, with pain improvement rates of up to 82% [5–7].

TMR, originally developed to improve the control of myoelectric prostheses [8], has emerged as a promising technique for managing post-amputation neuroma pain. It involves coapting the transected nerve to a nearby small motor branch, facilitating physiological nerve regeneration.

Recent reports indicate that when performed in the acute phase of amputation, TMR can also help prevent the development of chronic neuropathic pain [9]. Compared with previously described methods, TMR appears to yield superior and sustained patient satisfaction by promoting physiological reinnervation. Outcomes, however, can vary depending on the level of amputation and patient-specific factors, such as psychiatric comorbidities, opioid use, and other health conditions that have been associated with poorer results [10].

This case is unique in that it describes the development of NF of the upper limb following minor trauma in a previously healthy patient, without identifiable risk factors. The disease course ultimately led to a transhumeral amputation, and the patient underwent TMR to manage postoperative neuroma pain. To the best of our knowledge, this combination of anatomical location, severity, and advanced nerve management has been rarely reported in the literature.

The patient was informed that the data concerning the case would be submitted for publication, and he provided consent.

Case Report

A 48-year-old male patient with a history of untreated psoriasis presented to the Emergency Department (ED) after sustaining a crush injury to the right wrist between 2 metal structures. He had no other medical history or history of alcohol, drug, or tobacco use. On physical examination, there were no skin lesions or psoriatic plaques, no swelling, and a full range of motion in the joints. A radiographic evaluation ruled out osseous injuries. The patient was subsequently discharged with a diagnosis of mild contusion and was given symptomatic treatment.

Forty-eight hours later, he returned with worsening swelling, progressive pain, and functional limitation. Upon admission to the ED, he was hemodynamically stable. Initial evaluation revealed marked swelling of the forearm and hand, with small hemorrhagic blisters at the wrist level (Figure 1), pain with passive and active finger movement, and hypoesthesia of the thenar eminence. The pain was disproportionate to the injury and refractory to standard analgesic. A computed tomography scan marked diffuse thickening of the subcutaneous tissue, without evidence of subcutaneous emphysema or obvious fascial thickening (Figure 2), prompting further laboratory evaluation. During his assessment in the ED, the patient’s condition rapidly deteriorated, with fever, tachycardia, and hypotension. Given the clinical picture of septic shock, he was transferred to the resuscitation room, where fluid treatment was initiated, blood cultures were obtained, and broad-spectrum antibiotics were administered. There was no response to initial interventions, and vasoactive agents were initiated. Laboratory test results revealed markedly elevated inflammatory markers, with C-reactive protein level of 57 mg/L (reference range <5 mg/L), white blood cell count of 26 400/μL, erythrocyte sedimentation rate of 31 mm/h, creatinine level of 3.37 mg/dL, and lactic acid level of 4.02 mmol/L. His LRINEC score was 8 (Table 1). Given the high suspicion of NF with systemic involvement, the patient was taken to the operating room for urgent fasciotomy, intraoperative culture collection, and surgical debridement (Figure 3). He was subsequently admitted to the Intensive Care Unit (ICU) under mechanical ventilation and vasoactive support, with broad-spectrum antimicrobial (vancomycin and metronidazole) therapy, awaiting culture results.

Six hours after admission, the patient’s condition evolved to multi-organ failure. He was febrile and hemodynamically unstable, despite maximal vasoactive support. Surgical site inspection revealed extensive necrosis of soft tissues along the fasciotomy (Figure 4). Due to the life-threatening nature of the infection, an emergency transhumeral amputation was performed. The procedure was successfully completed, leading to a rapid improvement in hemodynamic stability. Blood and intraoperative cultures grew Streptococcus pyogenes. Antimicrobial therapy was adjusted based on susceptibility testing (for clindamycin and penicillin against S. pyogenes), and the patient completed a 2-week course of intravenous antibiotics. During hospitalization, the patient underwent 2 additional surgical debridements and presented a favorable evolution, with resolution of renal and hepatic failure. He remained hospitalized for 1 month, before being discharged to continue rehabilitation on an outpatient basis.

At a 6-month follow-up, the patient reported significant pain over the medial and lateral aspects of the amputation stump, with a positive Tinel sign. Ultrasound evaluation revealed neuromas of the median and radial nerves. Given the persistent neuropathic pain, surgical intervention was planned, and TMR of the ulnar, median, and radial nerves was performed. Three months postoperatively, the patient remained asymptomatic, pain-free, and with a negative Tinel sign. At the time of this report, he was under the care of the rehabilitation team, awaiting prosthetic fitting and functional training (Figure 5).

Discussion

This case exemplifies the rapid progression and high lethality of NF in the upper extremity, an uncommon yet severe skin infection that accounts for approximately 0.3% of all skin infections, with a reported mortality up to 27% [11]. Although NF most frequently affects the extremities, involvement of the upper limbs accounts for only about 10% of cases [3]. Even more uncommon is the rapid proximal spread necessitating emergency transhumeral amputation, as observed in our patient. The combination of an uncommon location, rapid deterioration, and surgical complexity highlights the unique nature of this report. The rapid evolution to septic shock, multi-organ failure, and the necessity for emergency transhumeral amputation illustrates the aggressive nature of the disease and the importance of early recognition and intervention principles, as described in the literature [2].

Notably, our patient lacked traditional high-risk comorbidities, aside from untreated psoriasis, and presented after a seemingly minor trauma, with no visible skin lesions, further complicating the diagnosis. Most published cases involve patients with diabetes, obesity, or intravenous drug use, which are among the most common risk factors for NF. Other contributing risk factors are cardiovascular disease, smoking, alcoholism, and renal failure [3,12]. Among these, diabetes mellitus is the most prevalent, present in up to 71% of cases. The absence of these risk factors in our patient underlines the need for clinical vigilance even in “low-risk” individuals. This aligns with literature noting that up to 40% of patients with NF have no identifiable risk factors [13].

NF encompasses a diverse group of infections with distinct microbiological profiles, leading to its classification into 4 subtypes based on the causative pathogen [3]. In our patient, S. pyogenes was isolated, confirming a type II NF, which is the most frequently reported form in cases of upper limb involvement [2,14]. Consistent with our findings, Christopoulos et al identified group A Streptococcus as the most frequently isolated pathogen in hand-origin NF, present in 44.2% of cases in their systematic review [11].

The clinical presentation of NF can often be confused with other conditions, as its initial signs and symptoms overlap with those of more benign soft tissue infections. The most frequently reported findings include erythema (73%), pain (63%), and edema (49%), which are nonspecific and can lead to misdiagnosis, particularly in the early stages [2]. In some cases, no external signs are evident, as the infection primarily affects deep soft tissues, while superficial layers remain clinically unremarkable [3]. As the infection progresses, patients can develop systemic involvement, including hemodynamic instability, fever, and, in some cases, altered neurological status. Given its high mortality rate, maintaining a high index of suspicion is essential, and prompt initiation of treatment is critical. However, the low incidence of NF, combined with its nonspecific symptoms, often results in delayed diagnosis and management, further contributing to its high fatality rate [2,3]. Given this diagnostic ambiguity, laboratory testing plays a crucial role in supporting early clinical suspicion.

The LRINEC score, introduced in 2004, incorporates 6 routine laboratory parameters (Table 1): C-reactive protein, white blood cell count, hemoglobin, serum sodium, creatinine, and serum glucose, to stratify patients into low, intermediate, and high-risk categories for NF [4]. A score of ≥6 has demonstrated a positive predictive value of 92% and a negative predictive value of 96%. In the present case, the patient had a LRINEC score of 8, placing him in the high-risk category and reinforcing the need for urgent surgical intervention,

According to a 2018 systematic review by Peyton and Domes [8], the LRINEC score remains a practical, cost-effective, and widely accessible tool, particularly useful for the early identification of type I and II NF. However, evidence suggests that the LRINEC score can have important limitations, particularly in upper extremity infections. Nawijn et al, in a retrospective cohort of patients with upper extremity NF, reported that the mean LRINEC score among those who died was 4, below the diagnostic threshold, whereas the mean score in amputated patients was 7 [15]. This finding suggests that while the LRINEC score remains a valuable tool, its predictive value can be lower in upper extremity cases, and clinicians should not rely on it in isolation. While magnetic resonance imaging, with its superior resolution, is considered the criterion standard for soft tissue evaluation, its availability in emergency settings can be restricted. Computed tomography, although more accessible, has lower sensitivity for detecting early fascial involvement in extremity infections [8].

Several factors have been identified that contribute to increased mortality and the likelihood of amputation in patients with necrotizing soft tissue infections. Significant predictors of mortality include advanced age (>60 years), involvement of critical anatomical sites (head, neck, trunk, and perineum), liver cirrhosis, malignancy, hypotension, elevated immature neutrophils (>10%), and serum creatinine levels exceeding 2 mg/dL [2].

The extent of necrotic spread has emerged as a key predictor regarding limb loss. Christopoulos et al, in their systematic review, found that necrosis extending proximally to the forearm correlated with increased mortality and a higher risk of amputation in NF cases originating in the hand [11,16]. In our patient, proximal extension of necrosis and rapid systemic deterioration were both present. Despite timely diagnosis and urgent surgical management, a transhumeral amputation was ultimately required to control the infection and achieve hemodynamic stabilization.

Following limb amputation, chronic pain is a frequent complication, affecting 70% to 80% of patients [17]. Phantom limb pain occurs in 51% to 82% of upper limb amputees, while residual limb pain is reported in 52% to 62% of cases, with approximately 25% linked to neuroma formation [9]. Identified risk factors for persistent pain include traumatic amputation and a transhumeral level of limb loss in upper extremity amputation [18]. In our case, the patient presented with 6 months of chronic limb pain in the tip of the stump.

Another strength of this report lies in its surgical implications. The management of chronic pain in amputees involves a range of non-surgical and surgical treatment approaches. Over the past 2 decades, TMR has emerged as a promising surgical technique for addressing neuroma-related pain and post-amputation pain. Originally described in 2002 by Dumanian et al [8] to enhance myoelectric prosthetic control, TMR was later found to be highly effective in pain relief. This procedure can be performed acutely to prevent pain or in a delayed manner to manage existing pain [19]. It helps to restore physiological function and synaptic potential, thereby reducing chronic pain and improving the patient’s quality of life. In upper limb amputations, TMR has demonstrated significant benefits, decreasing residual limb pain and phantom limb pain [20]. Although TMR has been extensively studied in lower limb amputees, reports focusing on upper limb application, especially at the transhumeral level in the context of infection, are limited. Furthermore, the present case supports recent evidence suggesting that TMR can reduce the incidence of phantom limb and residual pain. While traditional neuroma excision with muscle implantation has shown improvement in up to 82% of cases, TMR provides physiologic nerve targets and can offer superior long-term outcomes [5].

In cases of transhumeral amputation, various options exist for selecting the recipient nerve. The optimal combination for improving future myoelectric prosthetic control includes transferring the median nerve to the short head of the biceps brachii, the ulnar nerve to the brachialis, and the radial nerve to the lateral head of the triceps brachii [20,21].

This case not only highlights the potential severity of upper extremity NF, but also demonstrates the benefits of integrating TMR during acute surgical management, to improve long-term functional and pain outcomes. To the best of our knowledge, reports of TMR performed in transhumeral amputation due to NF remain limited, making this case a valuable contribution to the literature.

Conclusions

NF is a rare but life-threatening condition. Less than one-third of cases occur in the upper limb. The infection spreads rapidly, eventually involving the fascia. Clinical assessment and the use of scoring systems based on clinical and laboratory parameters, such as the LRINEC score, are essential for diagnosis. Early recognition and aggressive surgical management are necessary to save both the limb and the patient’s life; however, even with amputation, outcomes may not improve. TMR has emerged as an alternative therapy for managing phantom limb pain and chronic pain secondary to neuroma.