Hi KolarSue,
I checked my old IDC10 2021 manual.... there is Excludes 1 rule. Dx code G56.20 states unspecified upper limb lesion of ulnar nerve. There is the Excludes 1 rule says current traumatic nerve disorder see nerve injury by body region. Then dx M54.13 is Radiculopathy cervicothoracic region. Radiculopathy is pinched nerve in spine causing pain and numbness. Because of this the Excludes 1 rule does apply since related to nerve disorder.
Well I hope helped you understand
Lady T