(1) Rules for evaluation of permanent dorso-lumbar and lumbosacral impairments are as follows:

(a) Muscle spasm or involuntary guarding, bony or fibrous fusion, any arthritic condition, internal fixation devices or other physical finding shall be considered, in selecting the appropriate category, only insofar as productive of low back impairment.

(b) Gradations of clinical findings of low back impairments in terms of "mild," "moderate" or "marked" shall be based on objective medical tests.

(c) All of the low back categories include the presence of complaints of whatever degree.

(d) Any and all neurological deficits, complaints, and/or findings in other bodily areas or systems which are the result of dorso-lumbar and lumbosacral impairments, except for objectively demonstrated bladder and/or bowel sphincter impairments, shall be evaluated by the descriptions contained in the categories of dorso-lumbar and lumbosacral impairments.

(e) Bladder and/or bowel sphincter impairments deriving from dorso-lumbar and lumbosacral impairments shall be evaluated separately.

(f) Low back as used in these rules and categories includes the lumbar and adjacent areas.