Description of the condition

Limb amputation remains a significant global health burden, with updated estimates projecting that over 3.6 million individuals will be living with limb loss in the United States by 2050 [1]. The incidence continues to rise, driven largely by the aging population and the increasing prevalence of diabetes mellitus and peripheral vascular disease [1,2]. The most common etiologies for lower limb loss remain vascular pathology (primarily ischemia and diabetes), followed by trauma and malignancy. Conversely, upper extremity amputations in adults are predominantly traumatic in origin [2].

Demographic disparities persist as a critical issue; recent data from 2025 indicate that Black patients face up to a four-fold higher risk of major amputation compared to White patients, a gap often attributed to inequities in pre-amputation vascular care and socioeconomic determinants [3,4].

Beyond the physical loss, amputation is associated with significant morbidity, including high rates of surgical site infections, thromboembolism, and psychological distress such as anxiety and depression, which affect nearly 65% of patients in the early postoperative period [5]. Long-term mortality rates remain alarmingly high; recent cohorts report 1-year and 5-year mortality rates of approximately 24% and 48–60%, respectively, for major vascular amputations [6,7].

A critical yet often overlooked aspect of recovery is the development of neuropathic pain, primarily manifesting as Phantom Limb Pain (PLP) or Residual Limb Pain (RLP).

A central mechanism in the development of post-amputation pain is the formation of neuromas. Peripheral nerves are physiologically encased in an epineural sheath. During amputation, this sheath is disrupted, and severed axons regenerate in a disorganized manner into the surrounding scar tissue, forming a neuroma [8]. Although benign, these neuromas are frequently symptomatic, serving as ectopic foci of spontaneous neural discharge. The incidence of symptomatic neuromas varies significantly but has been reported to range from 4% to 49% in recent systematic reviews [9].

Phantom Limb Pain and Residual Limb Pain

Phantom Limb Pain (PLP) is defined as the perception of painful sensations in the absent portion of the limb. It is a highly prevalent sequela, with recent narrative reviews estimating a prevalence of over 60% in the chronic phase [10]. Its pathophysiology involves both peripheral mechanisms (neuroma discharge) and central mechanisms (cortical reorganization and spinal sensitization). PLP incidence appears largely independent of age, sex, or amputation level [10,11]. Furthermore, conservative treatments such as pharmacological management, physical therapy, and mirror therapy have yielded inconsistent preventive results [11,12].

Residual Limb Pain (RLP), distinct from PLP, is localized to the remaining stump and is often driven by the presence of symptomatic neuromas. RLP can prohibit the comfortable use of prosthetics and significantly impair quality of life. The psychological toll is profound, with patients frequently experiencing anxiety, post-traumatic stress, and affective distress [5,9].

Description of the interventions

Recently, surgical strategies have shifted from simple nerve transection to prophylactic reconstruction to mitigate these pathological processes.

• Targeted Muscle Reinnervation (TMR): Involves transferring severed motor nerve endings to the motor branches of nearby target muscles, providing a physiological “target” for regenerating axons [13].
• Regenerative Peripheral Nerve Interface (RPNI): Involves wrapping the dissected nerve end in an autologous free muscle graft. The graft revascularizes and serves as a “bio-amplifier” and target for the nerve axons to innervate, similarly preventing neuroma formation by satisfying the biological drive for axonal regeneration [14,15].

Previous systematic reviews, such as those by De Lange et al. and Mauch et al., have demonstrated that prophylactic intervention with TMR or RPNI significantly reduces the incidence of PLP and RLP compared to classical amputation [16,17]. However, these reviews encountered a scarcity of comparative studies. To date, TMR and RPNI have seldom been compared directly to one another in a comprehensive manner. Furthermore, their comparative effectiveness across different patient demographics—including the racial and ethnic disparities mentioned above—and comorbidities (diabetes, vascular disease) remains unclear. This systematic review aims to fill this gap by providing a comparison of the safety and efficacy of TMR versus RPNI.

Protocol design and registration

This systematic review protocol was developed in accordance with the Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P) statement [18,19]. The review will be conducted following the methodological guidance from the Cochrane Handbook for Systematic Reviews of Interventions and the Methodological Expectations for Cochrane Intervention Reviews (MECIR) standards [20]. The final report will comply with the PRISMA 2020 statement [21,22]. The protocol is registered in PROSPERO (CRD42024617299).

Eligibility criteria

Interventions and comparators

We will include studies comparing TMR or RPNI with classical amputation, as well as direct comparisons between TMR and RPNI. Additionally, comparisons of prophylactic versus curative applications of these techniques will be included for subgroup analysis.

For this review, “classical amputation” is defined as standard amputation (myoplasty or myodesy) where nerves are managed via traction neurectomy, simple ligation, or burial in muscle, without any additional specific reinnervation procedure or regenerative interface.

Outcomes

Currently, no standardized Core Outcome Set (COS) exists for effectiveness trials regarding post-amputation neural reinnervation techniques. Consequently, the outcome measures for this review were selected based on a preliminary analysis of key systematic reviews and primary observational studies—specifically those by De Lange et al., Mauch et al., Yuan et al. and Zimbulis et al. [13,16,17,23]—to ensure clinical relevance and comparability with existing literature.

To determine both clinical benefit and risk, outcomes are categorized into efficacy and safety domains.

Primary efficacy outcomes include the incidence of symptomatic neuroma, specifically recording whether the diagnosis relied on standardized definitions such as Arnold’s criteria [24]. These criteria classify a neuroma as symptomatic based on the presence of pain with specific characteristics in a defined neural distribution (mandatory), alongside confirmatory findings such as a positive Tinel sign, response to local anesthetic block, or imaging verification via ultrasound or magnetic resonance image. Additionally, we will assess the incidence and severity of both phantom limb pain (PLP) and residual limb pain (RLP), measured using validated scales such as the Visual Analog Scale (VAS), Numeric Rating Scale (NRS), or PROMIS.

Secondary safety outcomes encompass mortality and surgical complications, including wound dehiscence, surgical site infection (superficial or deep), hematoma, seroma, and abscess formation. We will also evaluate reoperation rates, defined as the need for stump revision, neuroma excision, or other secondary surgical procedures.

Search methods for identification of studies

A comprehensive electronic search will be performed in the following databases from inception to the present, with no language restrictions: Cochrane Central Register of Controlled Trials (CENTRAL), Web of Science, Scopus, PubMed/MEDLINE, CINAHL, Google Scholar and MedRxiv (to identify unpublished/gray literature and minimize publication bias).

The full search strategy, including keywords and boolean operators, is provided in S1 File (search strategy).

Data collection and analysis

Summary of findings

We will use the GRADE approach (Grading of Recommendations Assessment, Development and Evaluation) to assess the certainty of the evidence for the primary outcomes [33].

Ethics and dissemination

No ethical approval is needed for this review, as we will use data from previously published studies. We will spread our research in national and international medical congresses and any other non-conflicting means of publication.

Strengths and limitations of this study