Anatomical grades of nerve sparing: a risk‐stratified approach to neural‐hammock sparing during robot‐assisted radical prostatectomy (RARP)

What's known on the subject? and What does the study add? During radical prostatectomy, urological surgeons have tried to identify the “cord‐like NVB” at the lateral aspect of the prostate. However, little histological or physiological investigation was conducted to verify that the NVB identified at surgery really included the cavernous nerve. Recently, there have been observations that refute the dogma that the cavernous nerve is always within the NVB. In this study, we have described a hammock‐like distribution of the nerves on which the prostate rests, demonstrating that the NVB is more a network of multiple fine dispersed nerves than a distinct structure. We presented a novel nerve‐sparing approach to complete hammock preservation. This risk‐stratified approach for determining the degree of nerve sparing based on the patient's likelihood of ipsilateral EPE seeks to categorize patients for optimal balance between oncological outcomes and functional outcomes. OBJECTIVES To report the potency and oncological outcomes of patients undergoing robot‐assisted radical prostatectomy (RARP) using a risk‐stratified approach based on layers of periprostatic fascial dissection. We also describe the surgical technique of complete hammock preservation or nerve sparing grade 1. PATIENTS AND METHODS This is a retrospective study of 2317 patients who had robotic prostatectomy by a single surgeon at a single institution between January 2005 and June 2010. Included patients were those with ≥1 year of follow‐up and who were potent preoperatively, defined as having a sexual health inventory for men (SHIM) questionnaire score of >21; thus, the final number of patients in the study cohort was 1263. Patients were categorized pre‐operatively by a risk‐stratified approach into risk grades 1–4, where risk grade 1 patients received nerve‐sparing grade 1 or complete hammock preservation and so on for risk grades 2–4, as long as intraoperative findings permitted the planned nerve sparing. We considered return to sexual function post‐operatively by two criteria: i) ability to have successful intercourse (score of ≥4 on question 2 of the SHIM) and ii) SHIM >21 or return to baseline sexual function. RESULTS There was a significant difference across different NS grades in terms of the percentages of patients who had intercourse and returned to baseline sexual function ( P < 0.001), with those that underwent NS grade 1 having the highest rates (90.9% and 81.7%) as compared to NS grades 2 (81.4% and74.3%), 3 (73.5% and 66.1%), and 4 (62% and 54.5%). The overall positive surgical margin (PSM) rates for patients with NS grades 1, 2, 3, and 4 were 9.9%, 8.1%, 7.2%, and 8.7%, respectively ( P = 0.636). The extraprostatic extension rates were 11.6%, 14.3%, 29.3%, and 36.2%, respectively ( P < 0.001). Similarly, in patients younger than 60, intercourse and return to baseline sexual function rates were 94.9% and 84.3% for NS grade 1 as compared to 85.5% and 77.2% for NS grades 2, 76.9% and 69% for NS grades 3, and 64.8% and 57.7% for NS Grade 4 ( P < 0.001). CONCLUSIONS The risk‐stratified approach and anatomical technique of neural‐hammock sparing described in the present manuscript was effective in improving potency outcomes of patients without compromising cancer control. Patients with greater degrees of NS had higher rates of intercourse and return to baseline sexual function without an increase in PSM rates.