UINavigationControllerのデフォルトの戻るボタンを除去する ref: http://qiita.com/MTattin/items/2e43926869585e7011ae

file0.swift

///
/// CstmNV - 戻るボタン非表示
///
class CstmNC: UINavigationController {
    ///
    // MARK: ------------------------------ life cycle
    ///
    ///
    ///
    override func pushViewController(_ viewController: UIViewController, animated: Bool) {
        super.pushViewController(viewController, animated: animated)
        ///
        /// デフォルトの戻るボタンを非表示
        ///
        viewController.navigationItem.backBarButtonItem = nil
        viewController.navigationItem.hidesBackButton = true
    }
}
///
// MARK: ------------------------------ UINavigationBarDelegate
///
///
///
extension CstmNC: UINavigationBarDelegate {
    ///
    ///
    ///
    func navigationBar(_ navigationBar: UINavigationBar, shouldPush item: UINavigationItem) -> Bool {
        ///
        /// サイズを調整 - ここでitemに対して戻るボタンの非表示をしようとしても上手くいかなかったのでpushViewController側で実装
        ///
        item.titleView?.frame = navigationBar.frame
        return true
    }
}

file1.swift

///
/// CstmNV - 戻るボタン非表示
///
class CstmNC: UINavigationController {
    ///
    // MARK: ------------------------------ life cycle
    ///
    ///
    ///
    override func viewDidLayoutSubviews() {
        super.viewDidLayoutSubviews()
        ///
        /// デフォルトの戻るボタンを非表示
        ///
        self.visibleViewController?.navigationItem.backBarButtonItem = nil
        self.visibleViewController?.navigationItem.hidesBackButton = true
        ///
        /// titleViewに制約設定
        ///
        if #available(iOS 11.0, *) {
            if let v: UIView = self.visibleViewController?.navigationItem.titleView {
                v.translatesAutoresizingMaskIntoConstraints = false
                ///
                /// 
                vとv.superview?に対して制約設定
                iOS10と合わせるなら上下0、左右8の制約を指定すればOK
                ///
                ///
                v.superview?.layoutIfNeeded()
            }
        }
    }
    ///
    ///
    ///
    override func pushViewController(_ viewController: UIViewController, animated: Bool) {
        super.pushViewController(viewController, animated: animated)
        ///
        /// デフォルトの戻るボタンを非表示
        ///
        viewController.navigationItem.backBarButtonItem = nil
        viewController.navigationItem.hidesBackButton = true
        viewController.navigationItem.titleView?.frame = self.navigationBar.frame
    }
}