What is the standard of conduct of appointed counsel in a personal injury case?

Appointed counsel filed an opening brief that sets forth the facts and procedural history of the case and asks this court to review the record and determine whether there are any arguable issues on appeal. (People v. Wende, supra, 25 Cal.3d 436.) Defendant was advised by counsel of his right to file a supplemental brief within 30 days from the date the opening brief was filed. More than 30 days have elapsed and defendant has not filed a supplemental brief.