Dr. Richard S. Riggins, M.D., an orthopedic surgeon, appeals the judgment entered on the jury’s verdict awarding damages to Vivian R. Wyatt in her medical malpractice action against him. Dr. Riggins performed surgery on Wyatt and installed a device known as a ken nail to repair her fractured hip. Four months later, after the ken nail broke, Dr. Riggins performed a second surgery on Wyatt.
Wyatt filed her complaint against Dr. Riggins ten days before the expiration of the statute of limitation without an expert affidavit. Wyatt noted that an expert affidavit would be filed pursuant to OCGA § 9-11-9.1 (b). After an extension of time granted by the trial court, Wyatt filed the affidavit of Timothy M. Wright, Ph.D., to support her claim of negligence.1 Dr. Riggins filed a motion to dismiss, alleging Dr. Wright was not an expert competent to testify in this *855medical malpractice case. The trial court denied Dr. Riggins’ motion which Dr. Riggins enumerates as error.2
“The affidavit required by OCGA § 9-11-9.1 to be filed with a malpractice complaint is insufficient if it fails to show the affiant is competent to testify as an expert in the case. [Cits.]” Milligan v. Manno, 197 Ga. App. 171, 172 (397 SE2d 713) (1990). Therefore, the trial court erred in considering Dr. Wright’s affidavit as he was not competent to testify as an expert under OCGA § 9-11-9.1.
“ [Competency as an expert is not demonstrated by mere familiarity [with the standard of care]. During the course of one’s education, training, or experience as a [professor], it is possible to become ‘familiar’ with the standard of care and treatment generally employed by [a practicing surgeon]. Such familiarity would not, however, qualify one as an expert in that regard. An expert witness is one who through education, training, or experience has peculiar knowledge concerning some matter of science or skill to which his testimony relates. Absent some evidence to show that the affiant’s education, training, or experience as a [professor] would likewise demonstrate his similar expert qualifications as to [a practicing surgeon], the ‘exception’ in Milligan, supra would not be shown.” (Citations and punctuation omitted.) Chandler v. Koenig, 203 Ga. App. 684, 687 (417 SE2d 715) (1992).
There is no evidence in the present case which shows that Dr. Wright had any expertise as to the standard of care of a practicing surgeon in treating patients with biomechanical devices such as the ken nail. Dr. Wright possesses impressive credentials as a tenured professor of applied biomechanics in surgery at Cornell University Medical College. However, his credentials do not include, as they must, the ability, education, training or experience to perform the necessary surgery or prescribe any care to a patient with a bio-mechanical device. A person cannot be qualified as an expert in an area where he or she would not be lawfully qualified (by holding a valid state license) to perform the treatment which is the subject of the expert opinion.
This is not a case where an “overlap” of medical expertise allows one in a different profession to testify as to a standard of care applicable to both. See Avret v. McCormick, 246 Ga. 401 (271 SE2d 832) (1980). In Bethea v. Smith, 176 Ga. App. 467, 470 (336 SE2d 295) (1985), we determined that no overlap of expertise existed “between the orthopedic and podiatric general procedures insofar as the diagnosis and treatment of a fractured ankle [was] concerned.” In that *856case, unlike the subject case, the “expert” was a licensed, medical doctor. The trial court erred in determining Dr. Wright was competent to testify as an expert in the present case.
In light of the foregoing, we need not address Dr. Riggins’ remaining enumerations of error.
Judgment reversed.
Birdsong, P. J., Andrews, Johnson and Smith, JJ., concur. Pope, C. J., McMurray, P. J., Beasley, P. J., and Ruffin, J., dissent.The decision to grant the extension was affirmed by this court in Emory Clinic v. Wyatt, 200 Ga. App. 184 (407 SE2d 135) (1991).
Although this case has been to trial twice, Dr. Riggins adequately preserved this issue for appeal.