The only question presented by this appeal is whether the Commission erred in denying plaintiff any compensation for permanent partial disability as a result of the injury by accident on 4 June 1976.

G.S. § 97-2(9) provides: “The term ‘disability’ means incapacity because of injury to earn the wages which the employee was receiving at the time of injury in the same or any other employment.” Under our Workers’ Compensation Act, therefore, loss of earning capacity is the criterion for the determination of disability. Ashley v. Rent-A-Car Co., Inc., 271 N.C. 76, 155 S.E. 2d 755 (1967); Dail v. Kellex Corp., 233 N.C. 446, 64 S.E.2d 438 (1951). See also Willis v. Reidsville Drapery Plant, 29 N.C. App. 386, 224 S.E.2d 287 (1976).

In its Finding of Fact # 5, the Industrial Commission determined that plaintiff obtained a thirty percent (30%) permanent partial disability as a result of his “surgery” in February 1976 and in its Finding of Fact # 8, the Commission determined that plaintiff “still has a 30 percent permanent partial disability of the back; and there has been no change in his disability rating since the disability rating following the injury by accident sustained on 4 June 1976.” [Emphasis added.] Assuming that these findings are supported by competent evidence in the record, the Commission has failed to make the critical finding whether plaintiff suffered any permanent partial disability as a result of the compensable 4 June 1976 injury., The statement by the Commission in Finding of Fact # 8 that Dr. Mason “expressed the opinion that plaintiff’s disability was unchanged” is not a finding but merely a recital of Dr. Mason’s opinion. Furthermore, if the Commission had found as a fact that plaintiff’s “disability” was “unchanged,” we could not say that such a finding was supported by the evidence in this record.

Because of the equivocal nature of Dr. Mason’s testimony, we can understand the Commission’s failure to make the critical finding as to permanent partial disability. While in the ordinary case “disability” can be measured in terms of percentage, where, as here, the claimant has a pre-existing “disability” to the same part of the body *133which is affected by a subsequent compensable injury, “disability” must be measured in terms of capacity to earn wages. Only after plaintiff’s disability, both before and after the 4June injury, is related to and expressed in terms of plaintiff’s capacity to function as a truck driver can the Commission determine whether plaintiff is entitled to any compensation for permanent partial disability to his back as a result of the 4 June injury. Before the Commission can make such findings, it is necessary that there be a new hearing to clarify the medical testimony.

That portion of the Opinion and Award requiring defendant to pay temporary total disability and plaintiff’s medical expenses arising out of the accident, and approval of attorney’s fees for plaintiff’s counsel is affirmed; that portion of the opinion and award denying plaintiff any compensation for permanent partial disability is vacated and the cause is remanded to the Industrial Commission for a further hearing with respect to whether plaintiff sustained any permanent partial disability as a result of the 4 June 1976 accident, more definitive findings thereto, and the entry of an appropriate order.

Affirmed in part; vacated and remanded in part.