Standardized experimental nerve crush attempts should include the number, duration, and intensity (amount of pressure) of crushes. The authors have developed a new crushing device, a clamp with which predetermined forces can be applied to nerves. This allows the exertion of different, standardized forces to crush a nerve within a scale that produces second-degree injuries. The main advantages of the clamp are that it is small, although very robust, is purely mechanical, and is easy to handle. The jaws of the clamp are not serrated, so that pressure on the nerve is uniformly transmitted. To avoid unintended nerve damage, the edges of the jaws are smoothly rounded off. The closure of the clamp is mechanized by a spring. As the spring is exchangeable, any number of different preloads are available. The force can be varied, according to different requirements, and is applicable to variantly thick nerves in any experimental animal, thus enhancing standardization, and making cross-over comparisons of experimental study results possible.

This study was undertaken to quantify the effect of motor collateral sprouting in an end-to-side repair model allowing end organ contact. Besides documentation of the functional outcome of muscle reinnervation by end-to-side neurorrhaphy, this experimental work was performed to determine possible downgrading effects to the donor nerve at end organ level. In 24 female New Zealand White rabbits, the motor nerve branch to the rectus femoris muscle of the right hindlimb was dissected, cut, and sutured end-to-side to the motor branch to the vastus medialis muscle after creating an epineural window. The 24 rabbits were divided into two groups of 12 each, with the second group receiving additional crush injury of the vastus branch. After a period of 8 months, maximum tetanic tension in the reinnervated rectus femoris and the vastus medialis muscles was determined. The contralateral healthy side served as control. The reinnervated rectus femoris muscle showed an average maximum tetanic force of 24.9 N (control 26.2 N, p = 0.7827), and the donor- vastus medialis muscle 11.0 N (control 7.3 N, p = 0.0223). There were no statistically significant differences between the two experimental groups (p = 0.9914). The average number of regenerated myelinated nerve fibers in the rectus femoris motor branch was 1,185 +/- 342 (control, 806 +/- 166), and the mean diameter was 4.6 +/- 0.6 microm (control, 9.4 +/- 1.0 microm). In the motor branch to the vastus medialis muscle, the mean fiber number proximal to the coaptation site was 1227 (+/-441), and decreased distal to the coaptation site to 795 (+/-270). The average difference of axon counts in the donor nerve proximal to distal regarding the repair site was 483.7 +/- 264.2. In the contralateral motor branch to the vastus medialis muscle, 540 (+/- 175) myelinated nerve fibers were counted. In nearly all cross-section specimens of the motor branch to the vastus medialis muscle, altered nerve fibers could be identified in one fascicle distal and proximal to the repair site. The results show a relevant functional reinnervation by end-to-side neurorrhaphy without functional impairment of the donor muscle. It seems to be evident that most axons in the attached segment were derived from collateral sprouts. Nonetheless, the present study confirms that end-to-side neurorrhaphy is a reliable method of reconstruction for damaged nerves, which should be applied clinically in a more extended manner.

BACKGROUNDWith the move away from classical radical mastectomy to ever more skin‐sparing procedures, there has been an ongoing discussion about how much skin and subcutaneous tissue should be resected to perform an adequate mastectomy while leaving viable skin flaps. One of the common recommendations is to dissect just superficial to the superficial layer (SL) of the superficial fascia of the breast. This, in turn, has revived the old, unsolved controversy about the existence or absence of the SL, a fascia that reportedly encloses the mammary gland ventrally. In skin‐sparing mastectomies (SSM), which combine tumor resection with immediate breast reconstruction, the ideal would be to create skin flaps that are thin enough to remove all breast tissue but at the same time are thick enough to preserve flap circulation. The feasibility of meeting these two goals simultaneously and the possible role and relevance of the SL as a guide to dissection in SSM was examined in this study.METHODSSixty‐two breast resection specimens from 31 women who underwent breast reduction were examined histologically to determine whether the SL was present, whether breast tissue could be detected within or beyond this SL, the measured distance between the caudal border of the dermis and the SL or the breast tissue, and whether the thickness of the subcutaneous fat layer was correlated with the patients' physical data, such as body weight or body mass index (BMI).RESULTSThe SL was absent in 44% of resection specimens. When the SL was present, 42% of specimens contained several islands of breast tissue within the SL. No breast tissue was found beyond the SL. The minimal distance between the SL and the dermis varied from 0.2 mm to 4.0 mm; the minimal distance between the breast tissue and the dermis was 0.4 mm. In 50% of specimens, the minimal distance between the dermis and the SL or breast tissue was < 1.1 mm. A distance of ≥ 5 mm was encountered in only 17% of specimens, and a distance of ≥ 10 mm was encountered in only 5% of specimens. No significant correlation between the right and left breast was found with any of the parameters examined. A weak negative correlation was seen between the BMI and the mean thickness of the subcutaneous fat (P = 0.049; correlation coefficient [r] = −0.39; Spearman rank correlation).CONCLUSIONSHistologic evaluation revealed that the SL is not present in all breasts and, thus, cannot serve as a reliable plane of dissection. Furthermore, if the SL is present microscopically, then it often is too thin and delicate to be detectable macroscopically. Finally, even if the SL is present and visible macroscopically, the distance to the overlying skin is so small in the majority of patients that a dissection superficial to the SL would not leave viable skin flaps in skin‐sparing mastectomies. Cancer 2002;94:1619–25. © 2002 American Cancer Society.DOI 10.1002/cncr.10429