Allograft – a surgical graft of tissue transplanted into one individual from another individual of the same species. For example: a tendon (allograft) from a human donor transplanted into a recipient/patient with a knee injury.

Autograft – a surgical graft of tissue transplanted from one part of the body to another in the same organism. For example, a patient’s sural nerve (autograft) used as graft material for the same patient’s nerve repair surgery.

Axon – the part of a nerve cell (neuron) that transmits electrical signals to another cell, such as muscle or sensory cells. Depending on the location of the neuron, the length of the axon can vary widely and can be several feet in length.

Basal lamina – the innermost tube or membrane layer of the nerve extracellular matrix which surrounds an individual axon and through which a regenerating axon grows; also called the endoneurium.

Conduit – a natural or synthetic single hollow tube-like structure used in tension-free peripheral nerve repair.

Compression injury – ‘pinching’ of the nerve due to space constraints, which can lead to pain, loss of function or numbness in the affected area. Common nerve compression injuries include carpal tunnel syndrome and cubital tunnel syndrome.

Direct repair/direct coaptation – a surgical procedure where two ends of an injured peripheral nerve are sutured together to attempt to restore nerve function. Direct coaptation can be an effective treatment for peripheral nerve injury when no tension is generated after suturing the nerve stumps.

Distal– medical term for the part of the body situated farthest from the central point of attachment. For example, the distal ending (stump) of a peripheral nerve is the portion located farthest from the spinal cord relative to the injury site.

Endoneurium – the innermost tube or membrane layer of the nerve extracellular matrix which surrounds an individual axon and through which a regenerating axon grows; also called the basal lamina.

Epineurium – the outermost sheath layer of the nerve extracellular matrix. Typically, it binds together multiple fascicles where each fascicle contains multiple axon and filled basal lamina tubes. It also forms the nerve trunk and provides structural integrity to the nerve.

Extracellular matrix – the tissue support matrix outside of the cell; in nerve it consists of a series of concentric sheaths or tubes comprised of collagen and proteins.

Fascicle– an internal subdivision of the nerve surrounded by the perineurium; bundles of basal lamina

Fully Severed Nerve – a nerve that has been completely cut and has a gap between the nerve.

Myelin Sheath - insulating material wrapped around axons in peripheral nerves to help facilitate signal transmission along cells

Nerve Transfer – the surgical transfer of a functioning nerve to take over an area of lost function from nerve damage

Neuroma – a mass/tangled bundle of nerve fibers and scar tissue. Neuromas can be extremely painful to patients, and may require surgical intervention to alleviate the pain.

Neuron – the functional unit of the nervous system. It is also called the nerve cell.

Partially Severed Nerve – a nerve that has been cut but is still connected at some point.

Perineurium– the nerve extracellular matrix sheath that encompasses multiple endoneurial tubes to form a single fascicle.

Proximal – medical term for a point in the body located closer to the point of reference relative to another structure. For example, the proximal ending (stump) of a peripheral nerve is the portion located closest to the spinal cord relative to the injury site.

Remodeling – process by which an implanted biomaterial is replaced by the patient’s own tissue.

Revascularization – process by which blood supply to a body part, organ, or biomaterial is established. Revascularization plays a key role in wound healing by allowing nutrient delivery and waste removal.

Schwann cells - specialized cells that support peripheral nerves by producing the myelin sheath, aiding in the cleanup process of Wallerian Degeneration, and guiding new axon growth

Soft tissue attachments – a fibrous band or structure that causes abnormal adherence of tissues. For example, soft tissue attachments can constrict a nerve, leading to pain, numbness, and/or loss of function.

Tinel sign - a tingling sensation caused by light tapping over a nerve; a sign of nerve regeneration

Wallerian Degeneration - the process of breaking down axons and clearing cellular debris in an injured nerve making room for new axons to grow