Cadaveric Training for Peripheral Neuropathy: Bridging Anatomy, Precision, and Surgical Proficiency

Abstract

Background: Peripheral nerve surgeries require extensive practice to address anatomical variability and effectively manage neuropathy symptoms. While these procedures are increasingly performed by other surgical specialists, neurosurgeons bring unparalleled expertise in the central and peripheral nervous systems. Microscopic surgical techniques are essential for minimally invasive procedures, and cadaver-based education provides an invaluable medium for trainees to practice these techniques. However, few papers address these concepts in tandem. This study explores lesser-known peripheral nerve entrapments, highlights minimally invasive microscopic approaches, and advocates for cadaver-based training. Methods: Willed cadavers were embalmed through approved methods by the state anatomical board. For each decompression procedure, a 1–2 cm keyhole incision was made. Further methods are described in each nerve entrapment surgery below. Exploratory sessions with wider incisions were conducted either before or after the minimally invasive procedure to review anatomy or assess procedural success, respectively. Results: Neurosurgical medical education using cadavers allows trainees to practice techniques and enhance their skillset. Cadavers provide a valuable medium for exploring the relevant anatomy and visualizing the correct procedural steps after minimally invasive surgeries. Using microscopes for the procedures further facilitates detailed anatomical observation and technique refinement. Conclusions: Here, we show that cadaver-based medical education offers a realistic and controlled environment for exploring anatomical variability and refining surgical techniques. This method allows for a visual, mental, and tactile understanding, while performing minimally invasive procedures with a microscope on cadavers further enhances trainees’ proficiency, precision, and confidence, equipping them with the skills needed for improved surgical outcomes.

1. Introduction

Peripheral entrapment neuropathy is a widely diagnosed condition in the United States [1]. The typical etiology consists of the compression of a segment of a peripheral nerve at a specific site along its anatomical course. The mechanism of compression can vary but often arises from nerve vulnerability as it passes through a fibro-osseous tunnel or an opening in tissue [2,3]. Other compressive etiologies of nerve entrapment include stretch, overuse of a joint, or microtrauma [4]. Some common peripheral entrapment neuropathies include the radial, ulnar, and median nerves in the upper extremities, as well as the lateral femoral cutaneous, genitofemoral, sciatic, and femoral in the lower extremities [2,5]. This paper focuses on some less frequently encountered neuropathies, specifically the common peroneal, tibial, posterior interosseus, and suprascapular. Despite their lower incidence, understanding their anatomical significance and practicing surgical techniques for these conditions remains essential.

Patients often report symptoms such as paresthesia, anesthesia, and/or motor weakness that cannot be attributed to other causes, such as muscle injury [2,4]. Provocative clinical tests, clinical history, and physical examination are valuable for diagnosing peripheral entrapment neuropathies [4,5]. Additionally, imaging techniques, such as ultrasonography and magnetic resonance imaging (MRI), have gained importance for their ability to further delineate the clinical and anatomical characteristics of these neuropathies [3,6]. Most cases of peripheral nerve entrapment syndromes resolve with a conservative treatment plan, which is considered the primary therapeutic approach preferred and includes pain relief medication, physical therapy, lifestyle modification, or corticosteroid injections [7,8]. Failure of these conservative treatment methods may indicate surgical intervention for nerve decompression.

Neurosurgeons, along with other specialties, perform decompression procedures to relieve these neuropathies [1,9]. Although neurosurgery residents meet the required minimum exposure to peripheral nerve surgeries (PNSs), they perform fewer procedures compared to orthopedic and plastic surgery residents, whose exposure has increased over time [10]. Ensuring adequate training in this field for neurosurgeons remains essential to developing proficiency and fostering interest [10]. Specialized training in PNS is crucial for surgeons to effectively treat nerve entrapment, thereby enhancing patient outcomes. Cadaver-based training with microscopes, as outlined in this study, provides an effective method to enhance anatomical understanding and procedural skills, addressing gaps in neurosurgical exposure to PNS [10,11,12].

Since the 2019 COVID-19 pandemic, the use of cadavers in medical education has declined for medical students, residents, and attendings [13]. However, cadavers remain an invaluable resource for trainees to develop the technical skills and confidence necessary for performing surgical operations on living patients [11,14,15]. They offer a unique opportunity to practice surgical and neuroanatomical techniques, utilizing various tools such as microscopes, endoscopes, and surgical loupes [16]. Embalmed cadavers allow trainees to operate on life-like tissue planes and structures, simulating surgical scenarios encountered in the operating room [12].

Building on the advantages of cadaver-based training, we employed a microscopic approach to align with minimally invasive surgical techniques. The operating microscope offers neurosurgeons the ability to visualize and manipulate anatomical structures at a sub-millimeter level [16,17]. The enhanced precision minimizes tissue disruption and aligns with the principles of minimally invasive surgery, which aim to improve patient outcomes [18,19]. In recent years, minimally invasive procedures for peripheral neuropathy caused by entrapment or trauma have gained popularity due to their benefits, including reduced blood loss and lower risk of infection compared to larger incisions [20,21,22]. Practicing a minimally invasive surgical approach on cadavers can provide medical students, residents, and other trainees with the techniques necessary to achieve successful outcomes [23]. However, few published studies describe the detailed procedures and learning methods for these surgeries.

Therefore, this study aims to provide an in-depth anatomical and procedural understanding of lesser-known peripheral nerve entrapment syndromes to highlight the benefits of microscopic techniques for minimally invasive surgery and to advocate for the integration of cadaver-based training to enhance surgical skills and confidence.

2. Methods

Preparation of the cadaver: To ensure the anonymity of the cadaver’s identity, the local willed body program removes clothing and personal items, documents all information, and places a coded identification tag on the ankle. The cadaver is bathed and sprayed with disinfectant on surfaces and orifices. The body is injected with 16 oz of embalming fluid that consists of ethylene glycol, formaldehyde, and methanol in the first step. The second step requires the injection of 2.75 gallons of water. Most cadavers are set inside a 10% phenol bath between 12 and 24 h prior to being in a 38–42-degree refrigerator until needed.

An attending neurological surgeon was present during every procedure and step to ensure proper techniques, methods, and success.

Tools: A #3 knife handle, #15 blade, #11 blade, ratcheted forceps, hemostats, curved hemostats, Weitlaner retractor, Gelpi retractor, and a surgical microscope.

More methods will be discussed in the sections for the nerve and its respective decompression surgery.

3. Tibial Nerve

3.1. Introduction

Tarsal tunnel syndrome (TTS) involves the compression of the tibial nerve within the tarsal tunnel, a narrow fibro-osseous canal that contains tendons, vasculature, and the tibial nerve [24,25]. Common etiologies of TTS include external compression from sources such as cysts, tumors, dilated veins, or muscle hypertrophy; fractures of the distal leg or proximal foot; and tenosynovitis [3]. Rarely, the tibial nerve can also be compressed proximally at the tendinous arch of the soleus muscle, a condition referred to as a “soleus tendinous arch entrapment” or a “soleal sling syndrome” [7]. The tibial nerve innervates the posterior leg muscles responsible for plantarflexion and toe flexion and provides sensory innervation to the sole of the foot. In both entrapment syndromes, patients report paresthesia with a burning, shooting pain in the plantar foot and digits. Constant use of the leg (walking, running, driving, or stretching) that creates dorsiflexion and eversion may exacerbate the syndromes [7,8].

3.2. Surgical Anatomy

Originating from the ventral rami of the L4-S3 spinal nerve roots, the tibial nerve is one of two terminal branches of the sciatic nerve. Although it is a continuation of the sciatic nerve, the sciatic nerve is divided into two sections: the tibial and peroneal (fibular) sections. The sciatic nerve provides motor innervation and sensory afferent fibers in the posterior leg [26]. A few centimeters superior to the popliteal fossa, the sciatic nerve bifurcates to give off the two terminal branches. The popliteal fossa is bordered by the semimembranosus muscle superior-medially, the biceps femoris muscle superior-laterally, inferior-medially by the medial head of the gastrocnemius, and inferior-laterally by the lateral head of the gastrocnemius. The contents of the popliteal fossa include the tibial nerve, popliteal vein, popliteal artery, small saphenous vein, common peroneal nerve, and the popliteal lymph nodes, from superficial to deep in a posterior to anterior view, respectively. Distally to the bifurcation, the tibial nerve gives off the medial sural cutaneous nerve. This afferent, sensory nerve branch travels superficially to both heads of the gastrocnemius muscle to unite with the sural communicating branch from the common peroneal (common fibular) nerve. After joining, these nerves contribute to the sensation of the posterolateral aspect of the leg. The remainder of the tibial nerve traverses deep to the gastrocnemius muscle and plantaris muscle to the tendinous arch of the soleus muscle to enter the deep, posterior compartment of the leg [27]. The tibial nerve travels on the posterior aspect of the tibialis posterior muscle prior to entry into the tarsal tunnel. Proximal to the tunnel, the tibial nerve bifurcates and gives off another afferent, sensory branch, the medial calcaneal nerve. Posterior to the medial malleolus, the tarsal tunnel is bordered by the flexor retinaculum superficially (the “roof”), deep by the abductor hallucis (the “floor”), and deep and lateral by the calcaneus and talus. From anterior to posterior, the tarsal tunnel houses the tendon of the tibialis posterior, the tendon of flexor digitorum, the posterior tibial artery, the posterior tibial vein, the tibial nerve, and the tendon of flexor hallucis longus. Distally to the tarsal tunnel, the tibial nerve terminates by bifurcating into the medial and lateral plantar nerves.

3.3. Methods

Prior to the minimally invasive procedure, one leg was used to explore relative anatomy with a long incision (Figure 1 Left). Once confidence about the procedure increased, the other leg was prepared for the surgery. A 1.5 cm incision was made posterior to the medial malleolus. The subcutaneous tissue was carefully dissected as the tissue planes were shallow. Once the entire retinaculum and medial cutaneous nerve branch were visualized, dissection was made to release entrapment (Figure 1 Right).

4. Common Peroneal Nerve

4.1. Introduction

The common peroneal nerve, or common fibular nerve, can cause compressive neuropathy in the lower extremity [28]. Peroneal nerve entrapment neuropathy (PNEN) is the most frequent compressive neuropathy in the lower extremities [28,29,30]. Entrapment around the fibular head is the primary site of PNEN and can result from trauma (fibular fractures, blunt trauma, or knee dislocation) or non-traumatic causes (chronic or high compression from tight bandages or clothes) [28,31]. Compression typically occurs before the nerve bifurcates, resulting in both motor (loss of foot dorsiflexion and eversion) and sensory deficits. Therefore, clinical symptoms include paresthesia, anesthesia, and motor weakness (foot drop) [28,32].

4.2. Surgical Anatomy

The common peroneal nerve arises from the lumbosacral plexus, specifically the L4, L5, S1, and S2 spinal nerve roots [28,33,34]. It originates from the sciatic nerve, which bifurcates into the tibial and peroneal nerve proximal to the popliteal fossa [28,29,31,33,34]. The common peroneal nerve courses on the posterolateral part of the thigh deep to the long head of the biceps femoris prior to entry into the popliteal fossa [29,34,35]. It then courses lateral to the fibula around the bony prominence. Lateral and inferior with respect to the fibular head, the common fibular nerve bifurcates into the superficial fibular and deep fibular nerves [29,33,36].

4.3. Methods

A longitudinal, 1.5 cm incision was made around the fibular neck after palpating the fibular head. The dissection of the subcutaneous tissue was performed to expose the gastrocnemius and superficial head of the peroneus longus muscles along with the superficial fascia between these two muscle bellies. Careful division of the superficial fascia allowed the visualization of the common peroneal nerve situated deep in the fibrous band between the superficial head of the peroneus longus muscle and the soleus muscle (Figure 2). A dissection of the band was made to relieve the entrapment.

5. Posterior Interosseous Nerve

5.1. Introduction

Posterior interosseous nerve (PIN) syndrome is considered the most common compressive neuropathy affecting the radial nerve; however, it is not a common neuropathy in the general patient population [37,38]. PIN syndrome occurs due to trauma, brachial neuritis, rheumatoid arthritis, spontaneous compression, and repetitive pronation/supination activities [39]. Another cause is the hypertrophy of the recurrent radial vessels, often called the “leash of Henry” [37]. The most common site of PIN compression is the arcade of Frohse, or the proximal margin of the supinator muscle [37]. The PIN innervates the posterior forearm muscles, known as the extensors. PIN syndrome can present with weakness in finger and thumb extension but will have normal sensation [4,37,38,39,40]. As a result of the limited innervation of the extensor carpi ulnaris, patients with PIN syndrome can present with the radial deviation of the wrist during extension.

5.2. Surgical Anatomy

The PIN is a branch of the radial nerve, which stems from the posterior cord of the brachial plexus with spinal nerve roots C5 to T1. The radial nerve travels along the posterior arm and splits into the deep and superficial branches in the anterior proximal forearm, near the level of the head of the humerus [37,40]. The deep branch of the radial nerve journeys posteriorly along the radial neck, across and above the fibrous layer of the articular capsule of the humeroulnar joint and annular ligament of the radius [38,40]. The PIN arises from the deep branch of the radial nerve, as it emerges from between the two bellies of the supinator muscle. The PIN continues down the posterior forearm, innervating the extensor carpi radialis brevis, supinator, extensor carpi ulnaris, extensor pollicis brevis and longus, extensor digitorum, extensor digiti minimi, extensor indicis, and abductor pollicis longus [37,39,40].

5.3. Methods

Palpation identified the groove between the brachioradialis and the extensor carpi radialis longus and brevis muscles. A 1.5 cm longitudinal incision was made in the grove. Careful dissection of the subcutaneous tissue was performed. The separation of the extensor digitorum and extensor carpi radialis brevis muscles exposed the PIN deep to the deep head of the supinator. The identification of the proximal edge of the supinator allowed for the visualization and dissection of superficial fibrous bands at the radio-capitellar joint and the Arcade of Frohse to allow for decompression (Figure 3).

6. Suprascapular Nerve

6.1. Introduction

Suprascapular nerve entrapment syndrome can result from various etiologies, including traumatic injury, exertional overload, iatrogenic injury, systemic lupus erythematosus, or rheumatoid arthritis [41]. Additionally, the sharp borders of the suprascapular notch may cause irritation of the nerve, often called the “sling effect” [41]. Males are more likely to have a V-shaped, or narrow, notch than females, predisposing them to nerve entrapment [42]. The suprascapular nerve supplies the supraspinatus and infraspinatus muscles, which are responsible for the abduction and lateral rotation of the humerus at the glenohumeral joint, respectively. Suprascapular nerve entrapment can cause shoulder pain and weakness with symptoms depending on the nerve entrapment location [43]. Varying causes and symptoms cause suprascapular nerve entrapment syndrome to be difficult to diagnose, thus requiring a thorough history, nerve conduction tests, or imaging for confirmation [4,43].

6.2. Surgical Anatomy

The suprascapular nerve emerges from the superior trunk of the brachial plexus (spinal nerve roots C5 and C6) and runs deep to the trapezius and laterally across the lateral cervical region. It then passes through the suprascapular notch, under the superior transverse suprascapular ligament, to the posterior scapular region [41].

6.3. Methods

The cadaver’s right scapula was used to explore relative anatomy and landmarks to increase confidence before proceeding with the minimally invasive procedure. Three surgical techniques were used and are discussed below.

• Suprascapular notch approach: Palpation of the clavicle and the spine of the scapula was performed. A 1.5 cm parallel incision, in relation to the clavicle, was made two inches medial of the spinoglenoid junction and inferior to the clavicle. Subcutaneous tissue was dissected, revealing the supraspinatus muscle. Careful retraction and dissection allowed for the visualization of the suprascapular notch with the suprascapular artery and nerve. Decompression was made by the sectioning of the transverse scapular ligament (Figure 4A). However, some patients may be experiencing entrapment from a narrow canal. Therefore, decompression would be made using a shaver to increase the width of the suprascapular notch.
• Scapular notch, superior approach: Palpation of the spine of the scapula was performed. A 1.5 cm parallel incision was made. The dissection of the subcutaneous tissue revealed the spine of the scapula to view. Blunt dissection anteriorly along the spine was performed while retracting the supraspinatus muscle. The visualization of the suprascapular artery and nerve was made prior to entering the scapular notch (Figure 4B). Relieving the entrapment was performed with a shaver to remove the excess soft tissue and the sectioning of the inferior transverse scapular ligament.
• Scapular notch, inferior approach: Palpation of the spine of the scapula was performed. A 1.5 cm parallel incision along the inferior border of the spine allowed for the dissection of subcutaneous tissue. The infraspinatus muscle was retracted inferiorly while blunt dissection continued along the inferior aspect of the scapular spine. The identification of the scapular notch revealed the suprascapular artery and nerve (Figure 4C). Relieving the entrapment was performed with a shaver to remove the excess soft tissue and the sectioning of the inferior transverse scapular ligament.

7. Results

Our study relied on subjective feedback combined with an objective assessment. A total of five trainees participated, and all reported increased confidence in performing the procedure after reviewing the relevant anatomy and performing the procedure on the cadavers. The exploratory surgeries, performed with wider incisions, provided the trainees with a clearer understanding of the anatomical structures and relationships. This enhanced knowledge translated to greater precision and success during the minimally invasive procedures. Each trainee demonstrated the ability to thoroughly explain the neuroanatomy of the procedure upon the completion of the study. Additionally, the supervising neurosurgeon observed a marked improvement in the trainees’ surgical skills and accuracy throughout the sessions.

8. Discussion

Cadavers offer advantages for learning anatomy and developing strong surgical procedural skills. Their close resemblance to a living patient fortifies the trainees’ manual skills and comprehension of the dissection, particularly in the context of peripheral nerve decompression surgeries. During these cadaveric operations, the trainees actively engaged as either the primary surgeon, first assistant, or under the guidance of the neurosurgeon, providing hands-on experience essential for building surgical proficiency.

Practicing minimally invasive procedures on cadavers provides a controlled, low-risk environment for trainees to refine their skills. The use of a microscope during these procedures further enhances the precision necessary for minimally invasive approaches, as it allows the detailed visualization of neuroanatomy and improves tissue handling techniques. This combination of cadaveric training and microscopic assistance is particularly beneficial for peripheral nerve surgery (PNS), where anatomical variability in nerves can present unique challenges. Studies suggest that such training builds confidence and procedural competence, including minimally invasive procedures, and is still strongly favored by residents for education [16,39,44,45].

There are multiple different ways to embalm a human cadaver for the appropriate surgical training procedure. Our approach involved using a ‘fixed’ cadaver, as opposed to a fresh or ‘soft’ cadaver. The authors acknowledge that fixed cadavers do not ideally replicate real-time surgical conditions, such as tissue color and texture. However, they offer valuable opportunities to learn neuroanatomy and practice the tactile aspects of decompressive release surgeries. Future research might consider using different methods of embalming, such as soft cadaver embalming, to resemble fresh tissue. This will allow trainees the ability to reenact surgical scenarios more closely than fixed cadavers. Additionally, cadaver labs can be difficult and costly to maintain. However, even in resource-limited settings, the development of neurosurgical cadaver laboratories has been achieved, demonstrating that with proper planning and commitment, such facilities can be established to enhance resident education and stimulate future research [46].

Furthermore, our study included a limited number of trainees, which may restrict the generalizability of our findings. However, other studies have shown [include the studies]. Future studies with a larger cohort are needed to validate the effectiveness of cadaver-based training for minimally invasive procedures for PNS. Additionally, while the trainees reported increased confidence and skill, much of the data relied on subjective feedback. Incorporating objective metrics, such as procedural time or error rates, would provide a more comprehensive evaluation of the training’s impact.

Nevertheless, cadaver-based training has been shown to be an effective method for enhancing surgical skills and microsurgical dissections, particularly in neurosurgical residency programs [16,39,44,46]. This aligns with our findings, reinforcing that cadaver-based training, particularly when integrated with microscopic techniques, is essential for developing the precision and confidence required for minimally invasive peripheral nerve surgeries.

9. Conclusions

Medical institutions that provide cadaver skill labs and anatomical dissections offer trainees invaluable opportunities for hands-on surgical experience. Such practice enhances proficiency in surgical skills, as creating competent surgeons requires more than didactic methods. This study reinforces the value of cadaveric practice in enabling trainees (neurosurgeons, neurosurgery residents, and medical students) to simulate and refine various procedures while deepening their understanding of peripheral nerve entrapments. Cadavers offer the added benefit of tactile engagement with surgical tools, such as microscopes, compared to virtual reality platforms.

Future research should explore the long-term impacts of cadaveric training on surgical outcomes and assess its integration with emerging technologies, such as augmented reality or advanced embalming methods, to enhance realism. Evaluating the efficacy of cadaveric training in developing minimally invasive techniques across surgical fields could also provide valuable insights. These findings highlight the essential role of cadaver-based training in surgical education, ensuring that future surgeons are equipped with both theoretical knowledge and practical skills to improve patient care.