Reverse End-to-Side Nerve Transfer for Severe Ulnar Nerve Injury: A Western Canadian Multicentre Prospective Nonrandomized Cohort Study

Advances in Modern Microsurgery

Background/Objectives: Microsurgery employs techniques requiring optical magnification and specialized instruments to operate on small anatomical structures, including small vessels. These methods are integral to plastic surgery, enabling procedures such as free tissue transfer, nerve reconstruction, replantation, and lymphatic surgery. This paper explores the historical development, advancements, and current applications of microsurgery in plastic surgery. Methods: The databases MEDLINE (via PubMed) and Web of Science were selectively searched with the term "(((microsurgery) OR (advances)) OR (robotic)) OR (AI)) AND (((lymphatic surgery) OR (peripheral nerve surgery)) OR (allotransplantation))" and manually checked for relevance. Additionally, a supplementary search among the references of all publications included was performed. Articles were included that were published in English or German up to June 2024. Results: Modern microsurgical techniques have revolutionized plastic surgery, enabling precise tissue transfers, improved nerve reconstruction, and effective lymphedema treatments. The evolution of robotic-assisted surgery, with systems like da Vinci and MUSA, has enhanced precision and reduced operative times. Innovations in imaging, such as magnetic resonance (MR) lymphography and near-infrared fluorescence, have significantly improved surgical planning and outcomes. Conclusions: The continuous advancements in microsurgery, including supermicrosurgical techniques and robotic assistance, have significantly enhanced the capabilities and outcomes of plastic surgery. Future developments in AI and robotics promise further improvements in precision and efficiency, while new imaging modalities and surgical techniques expand the scope and success of microsurgical interventions.

Alternative Nerve Coaptations: End-To-Side and Beyond

Modern end-to-side (ETS) nerve transfers have undergone several permutations since the early 1990's. Preclinical data have revealed important mechanisms and patterns of donor axon outgrowth into the recipient nerves and target reinnervation. The versatility of ETS nerve transfers can also potentially address several processes that limit functional recovery after nerve injury by babysitting motor end-plates and/or supporting the regenerative environment within the denervated nerve. Further clinical and basic science work is required to clarify the ideal clinical indications, contraindications, and mechanisms of action for these techniques in order to maximize their potential as reconstructive options.

Assessment, management, and rehabilitation of traumatic peripheral nerve injuries for non-surgeons

Electrodiagnostic evaluation is often requested for persons with peripheral nerve injuries and plays an important role in their diagnosis, prognosis, and management. Peripheral nerve injuries are common and can have devastating effects on patients' physical, psychological, and socioeconomic well-being; alongside surgeons, electrodiagnostic medicine specialists serve a central function in ensuring patients receive optimal treatment for these injuries. Surgical intervention-nerve grafting, nerve transfers, and tendon transfers-often plays a critical role in the management of these injuries and the restoration of patients' function. Increasingly, nerve transfers are becoming the standard of care for some types of peripheral nerve injury due to two significant advantages: first, they shorten the time to reinnervation of denervated muscles; and second, they confer greater specificity in directing motor and sensory axons toward their respective targets. As the indications for, and use of, nerve transfers expand, so too does the role of the electrodiagnostic medicine specialist in establishing or confirming the diagnosis, determining the injury's prognosis, recommending treatment, aiding in surgical planning, and supporting rehabilitation. Having a working knowledge of nerve and/or tendon transfer options allows the electrodiagnostic medicine specialist to not only arrive at the diagnosis and prognosticate, but also to clarify which nerves and/or muscles might be suitable donors, such as confirming whether the branch to supinator could be a nerve transfer donor to restore distal posterior interosseous nerve function. Moreover, post-operative testing can determine if nerve transfer reinnervation is occurring and progress patients' rehabilitation and/or direct surgeons to consider tendon transfers.

Current perspectives on peripheral nerve repair and management of the nerve gap

From the first surgical repair of a nerve in the 6th century, progress in the field of peripheral nerve surgery has marched on; at first slowly but today at great pace. Whether performing primary neurorrhaphy or managing multiple large nerve defects, the modern nerve surgeon has an extensive range of tools, techniques and choices available to them. Continuous innovation in surgical equipment and technique has enabled the maturation of autografting as a gold standard for reconstruction and welcomed the era of nerve transfer techniques all while bioengineers have continued to add to our armamentarium with implantable devices, such as conduits and acellular allografts. We provide the reader a concise and up-to-date summary of the techniques available to them, and the evidence base for their use when managing nerve transection including current use and applicability of nerve transfer procedures.

Compression of the Ulnar Nerve by the Arcade of Struthers: Look and You Shall Find

BACKGROUND

The arcade of Struthers was first proposed by Kane et al in 1973. Clinical investigations of this structure have been limited to small case series, focusing on the arcade as an isolated cause of compressive ulnar neuropathy. The purpose of our study was to investigate the incidence of this structure in patients undergoing ulnar nerve transposition.

METHODS

A retrospective chart review of prospectively maintained data in a single surgeon's practice was performed. Records of patients undergoing surgery for compressive ulnar neuropathy at the cubital tunnel were evaluated for documentation of a compressive arcade of Struthers. In addition, a scoping review of the literature was undertaken to better characterize current understanding of this structure and its recognition in clinical practice.

RESULTS

A total of 197 patients underwent ulnar nerve transposition. The overall incidence of a compressive arcade of Struthers was noted to be 67 out of 197 (34%). All patients with a compressive arcade were noted to have an internal brachial ligament running below the nerve. Patients undergoing revision surgery were found to have a compressive arcade 51% of the time (20/39), whereas 30% of patients undergoing primary surgery were found to have a compressive arcade (47/158). Only 12 clinical studies examining the arcade of Struthers have been published in the last 20 years, the majority being single case reports.

CONCLUSIONS

Compression of the ulnar nerve by the arcade of Struthers is a common finding and can contribute to compressive ulnar neuropathy at the elbow both in primary and revision cases.

Key Considerations for Nerve Transfer Rehabilitation After Surgical Reconstruction for Brachial Plexus and Peripheral Nerve Injuries

Nerve transfer surgery is commonly used to treat patients with brachial plexus injuries. However, guidelines on postoperative rehabilitation are not clearly established. Nerve transfers require the patient to relearn how to recruit newly innervated muscle(s), which may not occur naturally or intuitively. Supervised therapy is a valuable resource to guide patients through their lengthy recovery (often >12 months) because target muscle strength is both obtained and functionally used in daily life. This article highlights 10 key principles that provide the foundation for rehabilitation following nerve transfer surgery after a brachial plexus injury. Due to the shortcomings of the current evidence base for nerve transfer rehabilitation, we have included our anecdotal experience to augment the existing literature. It is important to have a collaborative surgeon-therapist relationship to communicate regarding operative details, expected timelines for reinnervation, patient needs, and realistic expectations. We provide examples of how to tailor the exercise program to synergistically recruit both the donor and target muscle action, including how to appropriately advance exercises based on the current level of nerve return. We also discuss the role that fatigue plays in denervated muscle and how fatigue may affect the exercise demands placed on the target muscle during specific stages of recovery.

Improving outcomes in traumatic peripheral nerve injuries to the upper extremity

Peripheral nerve lesions of the upper extremity are common and are associated with devastating limitations for the patient. Rapid and accurate diagnosis of the lesion by electroneurography, neurosonography, or even MR neurography is important for treatment planning. There are different therapeutic approaches, which may show individual differences depending on the injured nerve. If a primary nerve repair is not possible, several strategies exist to bridge the gap. These may include autologous nerve grafts, bioartificial nerve conduits, or acellular nerve allografts. Tendon and nerve transfers are also of major importance in the treatment of nerve lesions in particular with long regeneration distances. As a secondary reconstruction, in addition to tendon transfers, there is also the option for free functional muscle transfer. In amputations, the prevention of neuroma is of great importance, for which different strategies exist, such as target muscle reinnervation, regenerative peripheral nerve interface, or neurotized flaps. In this article, we give an overview of the latest methods for the therapy of peripheral nerve lesions.

Perineurial Window is Critical for Experimental Reverse End-to-Side Nerve Transfer

BACKGROUND

The depth of connective tissue window in the side of a recipient nerve in reverse end-to-side transfers (RETS) remains controversial.

OBJECTIVE

To test whether the depth of connective tissue disruption influences the efficiency of donor axonal regeneration in the context of RETS.

METHODS

Sprague-Dawley rats (n = 24) were assigned to 1 of the 3 groups for obturator nerve to motor femoral nerve RETS: group 1, without epineurium opening; group 2, with epineurium only opening; and group 3, with epineurium and perineurium opening. Triple retrograde labeling was used to assess the number of motor neurons that had regenerated into the recipient motor femoral branch. Thy1-GFP rats (n = 8) were also used to visualize the regeneration pathways in the nerve transfer networks at 2- and 8-week time point using light sheet fluorescence microscopy.

RESULTS

The number of retrogradely labeled motor neurons that had regenerated distally toward the target muscle was significantly higher in group 3 than that in groups 1 and 2. Immunohistochemistry validated the degree of connective tissue disruption among the 3 groups, and optical tissue clearing methods demonstrated donor axons traveling outside the fascicles in groups 1 and 2 but mostly within the fascicles in group 3.

CONCLUSION

Creating a perineurial window in the side of recipient nerves provides the best chances of robust donor axonal regeneration across the RETS repair site. This finding aids nerve surgeons by confirming that a deep window should be undertaken when doing a RETS procedure.

Reverse End-to-Side Transfer to Ulnar Motor Nerve: Evidence From Preclinical and Clinical Studies

The disappointing outcomes of conventional nerve repair or grafting procedures for proximal ulnar nerve injuries have led the scientific community to search for better alternatives. The pronator quadratus branch of the anterior interosseous nerve has been transferred to the distal ulnar motor branch in a reverse end-to-side fashion with encouraging results. This transfer is now becoming commonly used as an adjunct to cubital tunnel decompression in patients with compressive ulnar neuropathy, underscoring the need for this knowledge transfer to the neurosurgical community. However, the mechanism of recovery after these transfers is not understood completely. We have reviewed the existing preclinical and clinical literature relevant to this transfer to summarize the current level of understanding of the underlying mechanisms, define the indications for performing this transfer in the clinic, and identify the complications and best practices with respect to the operative technique. We have also attempted to identify the major deficiencies in our current level of understanding of the recovery process to propose directions for future research.