(a) Where the injury results in a partial impairment which is permanent and which does not result in permanent total disability, compensation shall be paid during the period of total disability, as provided in sections 642 and 643 of this title, and at the termination of total disability, the employer shall pay to the injured employee 662/3 percent of the average weekly wage, computed as provided in section 650 of this title, subject to the maximum and minimum weekly compensation rates, for a period determined by multiplying the employee's percentage of impairment of the whole person by 330 weeks. The percentage of impairment to the whole person is the percentage of impairment to the particular body part, system, or function converted to the percentage of impairment to the whole person as provided in subsection (b) of this section.

(b) Any determination of the existence and degree of permanent partial impairment shall be made only in accordance with the whole person determinations as set out in the Fifth Edition of the American Medical Association Guides to the Evaluation of Permanent Impairment. In order to utilize any subsequent edition of the American Medical Association Guides to the Evaluation of Permanent Impairment or any other appropriate guides to the evaluation of permanent impairment, the Commissioner, in consultation with the Department of Labor Advisory Council, shall adopt a rule. The Commissioner shall adopt a supplementary schedule for injuries that are not rated by the impairment guide authorized for use by the Department to determine permanent disability.

(c) Notwithstanding the provisions of subsections (a) and (b) of this section, for the purposes of determining the payment period for any permanent partial impairment to the spine, the percentage of impairment shall be determined in accordance with rules adopted by the Commissioner according to which an injury to the spine which is evaluated as a 60 percent impairment of the whole person shall provide 330 weeks of compensation.

(d) An impairment rating determined pursuant to this section shall be reduced by any previously determined permanent impairment for which compensation has been paid, but if the combination of the prior impairment rating and the rating determined pursuant to this section would result in the employee being considered permanently totally disabled, the prior rating shall not negate a finding of permanent total disability. (Amended 1959, No. 34, eff. March 12, 1959; 1963, No. 134, § 2, eff. June 6, 1963; 1977, No. 182 (Adj. Sess.), § 13, eff. May 3, 1978; 1993, No. 225 (Adj. Sess.), § 7, eff. April 1, 1995; 2007, No. 208 (Adj. Sess.), § 6.)