A Cadaveric Anatomical and Histological Study of Recipient Intercostal Nerve Selection for Sensory Reinnervation in Autologous Breast Reconstruction

Background Autologous breast reconstruction (ABR) has grown in popularity due to improved aesthetic and long-term patient reported outcomes, but data regarding sensory reinnervation of autologous flaps remain limited. Traditionally, the lateral cutaneous branch of the fourth intercostal nerve has been used for flap neurotization, but the use of the anterior cutaneous branch of the intercostal nerves (ACB) offer a more optimal location to the microsurgical field when using internal mammary vessels for the microanastomosis. This study aimed to evaluate the optimum ACB recipient site level for sensory nerve coaptation in ABR. Methods Twelve hemi-chests were dissected from six fresh cadaveric females. Costal cartilages were removed and the anterior cutaneous intercostal nerve (ACB) and the lateral (subcutaneous) division of the anterior cutaneous branch (LACB) of the intercostal nerve were exposed. Anatomical measurements were recorded, and nerve samples were evaluated histologically with carbonic anhydrase staining to differentiate sensory fascicles. Assessment of fascicular diameter, axonal counts, and fascicular area were compared. Results A total of 75 nerve specimens were assessed. The ACB was identified at all levels (100%) and the subcutaneous LACB was noted consistently in the second to fourth rib space (96% cadavers), with a median length of 43, 37.5, and 37 mm, respectively. Across all rib spaces, the fascicular and axonal counts were comparable between the LACB and ACB. Nerves in the second intercostal space had a significantly larger mean fascicular area mean (112,816 ± 157,120 µm2) compared with that in the fourth (mean 26,474 ± 38,626 µm2), p = 0.03. Axonal count of sensory fascicles was the highest in the second intercostal nerves (p < 0.05). Conclusion This study provides anatomical and histological basis to determine the optimum recipient site choice for sensory coaptation in microsurgical breast reconstruction. This would aid in operative decision-making regarding the ideal recipient anterior cutaneous intercostal nerve branches for recipient site coaptation in ABR.

An ulnar parametacarpal perforator flap for volar digital soft tissue reconstruction

We present outcomes of using a perforator-based ulnar parametacarpal flap in 25 patients for digital pulp defects. These included 17 free transfers to the thumb, index, middle and ring fingers and eight reverse pedicled transfers to the little fingers. This flap includes a dorsal sensory branch of the ulnar nerve, which was sutured to the digital nerve in all transfers. Each flap had one to three reliable perforators (mean 0.44 mm diameter) to the ulnar parametacarpal region and contained at least one perforator within 2 cm proximal to the palmar digital crease. All the 25 flaps survived completely. Twenty-two patients were followed for 15 months (range 12 to 24), and three were lost to follow-up. The mean static and moving two-point discrimination of the flap was 7 mm and 5 mm, respectively. At the donor site, sensory reinnervation was acceptable. We conclude that ulnar parametacarpal perforator flaps offer sensate, thick and glabrous skin for finger pulp repair, all in a single operative field. Level of evidence: IV

Cutaneous sensory outcomes from three transhumeral targeted reinnervation cases

Background: Although targeted muscle reinnervation has been shown to be effective in enhancing prosthetic control for upper limb amputees, restored hand sensations have been variable. An understanding of possible sensory feedback channels is crucial in working toward more effective closed-loop prosthetic control. Objectives: To compare sensory outcomes of different targeted sensory reinnervation approaches. Study design: Case series, cross-sectional, and retrospective. Methods: Three transhumeral amputees that had undergone different sensory reinnervation approaches were recruited. Skin pressure sensitivity thresholds and anatomic sensory mapping were performed using Semmes-Weinstein monofilaments. The clinical charts of the subjects were reviewed to compare the sensory maps performed during the earlier post-reinnervation period. Results: While the first two subjects achieved return of hand sensations on the stump skin in early follow-up, the maps showed attenuation over time. The last subject developed discrete sensations of all digits in the recipient cutaneous nerve territories away from the reinnervated muscles. Conclusions: These findings confirm that it is feasible to restore hand sensation after transhumeral targeted reinnervation, but there is a significant intersubject variability. The intrafascicular approach may be particularly effective in restoring digit sensation and deserves further exploration, as do factors affecting stability of the hand maps over time. Clinical relevance In addition to enabling intuitive motor control of myoelectric prosthesis, targeted reinnervation can also result in sensory restoration of the hand. Documentation of sensory mapping present after reinnervation may assist with exploring future techniques for sensory enhancement, with the goal of working toward closed-loop prosthetic control.