Keywords
sensory switching - sensory reconstruction - elbow reconstruction - sensory nerve
- sensory territory
Introduction
There are some functionally important elements for hand and arm movements in the elbow
such as muscles, tendons, and nerves; therefore, damage to soft tissue of the elbow
may cause crucial disruption of hand and arm functions. Although some options are
available for the reconstruction of general soft tissue defects, a specific strategy
for elbow reconstruction is needed in addition to the reacquirement of tactile sensation
because of its anatomy and specific functions, as this region is a weight-bearing
site and necessitated to avoid injury such as pressure sore.
With the use of free flaps, the sensory nerve can be reconstructed by suturing the
cut end of the recipient sensory nerve to the nerve in the free flap. With the use
of a pedicle flap, however, because reconstruction of the sensory nerve at the defect
is usually not possible by suturing, the sensory territory of the flap at the donor
site can be often conserved. Interestingly, some cases show a sudden transfer of sensory
territory preserved in the flap to the reconstructed site, in a “switching”-like manner.
Previous reports have described sensory relearning and reeducation after damage to
sensory nerves, phenomena that are related to the plasticity of the sensory cortex
and that may be similar to the mechanism of plasticity of the brain. Here we describe
the new concept of “sensory switching” that may be related to the plasticity of the
sensory cortex.
We describe three cases of elbow injury reconstructed with pedicle flaps containing
the sensory nerves, and discuss the concept of “sensory switching.”
Case Presentation
Case 1
A 75-year-old woman presenting with arrhythmia and undergoing catheter ablation had
her right elbow exposed to X-rays. She had angina and uterine fibroid but no metabolic
diseases including diabetes on her past history. After the catheter therapy, radiation
skin ulcer on the right elbow uccered. Although the dermatologist treated for over
1½ years, the ulcer has still remained and the patient was introduced to our department.
The left elbow was debrided ([Fig. 1A]) and reconstructed with a pedicled island forearm flap (6 × 4.5 cm) containing the
lateral cutaneous nerve of the forearm ([Fig. 1B, C]).
Fig. 1 (A–C) A radiation skin ulcer on the elbow was reconstructed with a pedicled island forearm
flap containing the lateral cutaneous nerve of the forearm. (D) Sensory switching was observed after 6 months.
Case 2
A 49-year-old man presented with skin and the underlying soft tissue defect caused
by traffic injury to his right elbow ([Fig. 2A]). He had no past history including any metabolic diseases. During 2 weeks of conservative
therapy, the wound was infected and radical debridement was necessitated. After the
debridement of infected tissue, because cortex of ulnar head was appeared, the defect
was reconstructed with a venoneuro-accompanying artery fasciocutaneous flap (VNAF)
containing the basilic vein ([Fig. 2A–C]).
Fig. 2 (A–C) A skin and subskin soft tissue defect caused by injury was reconstructed with a
venoneuro-accompanying artery fasciocutaneous flap (VNAF) containing the basilic vein.
(D) Sensory switching was observed after 4 months.
Case 3
A 75-year-old woman recognized small nodule on her right elbow. Biopsy was performed
and sarcoma was suspected. After the tumor resection, the elbow was reconstructed
with a VNAF flap containing the cephalic vein ([Fig. 3A–C]). The tumor was diagnosed as a low-grade myxofibrosarcoma and no adjuvant radiotherapy
or chemotherapy was performed.
Fig. 3 (A–C) Myxofibrosarcoma on right elbow underwent tumor resection. The elbow was reconstructed
with a venoneuro-accompanying artery fasciocutaneous flap containing the cephalic
vein. (D) Sensory switching was observed after 5 months.
The three cases showed good graft take without any adverse effects such as partial
skin necrosis and skin contracture. After the hospital discharge, patients were followed
up at the outpatient department every 1 to 2 months. Tactile sensation was checked
by touching the reconstructed region with patients' eye-closed. “Sensory switching”
was observed after 6 months in case 1 ([Fig. 1D]), 4 months in case 2 ([Fig. 2D]), and 5 months in case 3 ([Fig. 3D]).
Discussion
There are three options for the reconstruction of elbow soft tissue defects: skin
grafts, free flaps, and pedicle flaps. With skin grafts, sensory reacquirement relies
on the invasion of sensory nerves surrounding the graft; however, tactile sensation
is hardly restored. With the free flap, the end of the transected cutaneous sensory
nerve contained in the flap is sutured to the original nerve end located in the skin
defect, resulting in better axonal regeneration and sensory recovery than with a skin
graft. With a pedicle flap such as an island forearm flap, NAF or VNAF, the pedicled
sensory nerve is used. Especially with NAF or VNAF, the flap blood supply relies on
vessels accompanying and inevitably containing the sensory nerve.[1]
[2]
With the pedicle flap, remaining sensation resembling phantom pain is often observed;
also the sensation on the flap sometimes appears suddenly at the reconstructed site,
in a “switching” manner, which we describe as “sensory switching.” Magnetoencephalography
of syndactyly patients before and after surgical separation shows cortical reorganization
attributed to plasticity of the sensory cortex.[3] Moreover, the reorganization of the somatosensory cortex occurs after injury to
the median nerve. These phenomena are summarized in superb sentences by hand surgeons
“the hand speaks a new language to the brain.”[4]
Analogous to this mechanism, sensory switching on the pedicle flap may also occur
because of the plasticity of the sensory cortex. Sensory relearning and reeducation
is closely related to age after nerve transection and repair.[5]
[6]
[7] Our cases tend to be age-related “sensory switching”; however, the number is too
small to discuss about this tendency. Further study is needed in this respect.
Rehabilitation might be effective in promoting sensory switching on the basis of sensory
reeducation after nerve injury. Conventionally, training for tactile sensation by
visual stimulation is effective.[8] Other forms of stimulation, such as olfactory and auditory, also help tactile reeducation
of fingers.[9] The elbow often makes contact with other objects, for example, the chin resting
on the hands, which may stimulate sensory receptors and constitute unconscious rehabilitation.
To summarize, tactile sensation is desirable in the reconstruction of elbow injury
because of its specific functions. An especially good option in the reconstruction
of the elbow is the innervated pedicle flap. Sensory switching may rely on the plasticity
of the somatosensory cortex; however, the mechanism is unknown, and rehabilitation
is potentially necessary for promoting sensory switching. Further study is needed
for additional data.
