Factors That Influence the Outcome of Zone I and Zone II Flexor Tendon Repairs in Children Bassem Elhassan, MD, Steven L. Moran, MD, Cesar Bravo, MD, Peter Amadio, MD From the Mayo Medical College, Department of Orthopedic Surgery, and the Department of Plastic/Orthopedic Surgery, Division of Hand Surgery, Mayo Clinic, Rochester, MN. Purpose: To evaluate the factors that influenced the clinical results of zone I and II flexor tendon repairs in children at a single institution. Methods: Forty-one fingers (35 patients) in patients ages 2 to 14 years with zone I or II flexor tendon injuries were identified. There was a zone I tendon injury in 16 fingers and a zone II tendon injury in 25 fingers. Concomitant injuries to the digital nerves were seen in 18 fingers. Primary repair was performed within 1 week in 35 fingers and delayed repair (2–9 wk) was performed in 6 fingers. After surgery 22 fingers (21 patients) were treated with early controlled mobilization and 19 fingers (14 patients) were treated with plaster immobilization. Results: All patients were available for evaluation at a mean follow-up period of 42 months. Patients were subdivided into 2 age groups: (1) 0 to 7 years and (2) 8 to 15 years. Digital performance was evaluated by determining the percentage return of normal finger function according to a total active motion formula. Functional evaluation of all digits in both groups showed excellent or good results. Zone I repairs had better results than zone II repairs and isolated tendon repairs had better results than those with associated nerve repairs. The age of the patients nor postoperative protocol did not influence the final digital motion. Conclusions: A good outcome can be expected after repair of zone I or II flexor tendon injuries in children. (J Hand Surg 2006;31A:1661–1666. Copyright © 2006 by the American Society for Surgery of the Hand.) Type of study/level of evidence: Prognostic III. Key words: Flexor tendon, injury, children, zone I, zone II, outcome. I mprovement in the results of flexor tendon re- pairs in adults, especially those injuries involving zone II, has been reported over the past 2 de- cades. 1–9 Fewer studies 10 –19 are reported in the lit- erature on the outcome of zone I and II repairs in children. The results and the postoperative therapy in these reports have varied despite the good healing potential in children. This is in part related to the limited ability to implement a structured rehabilita- tion program in children. Postoperative immobilization protocols in children with flexor tendon injuries have been recommended by many investigators 14,15 and have been shown to improve the final result. Such findings suggest that the concept of early digital mobilization does not necessarily apply to children. In fact, some investi- gators 16,17 believe that despite immobilization, pri- mary repair of flexor tendon injuries in children produces better results than in adults. It has been suggested that the superior results seen in some series may occur because children heal more rapidly, have a better blood supply, and have greater ability to remodel scars and adhesions. 18 In most published reports in the literature on flexor tendon repairs in children, specifically involving zones I or II, the multiple variables that might have affected the repair outcome were not all determined. This article evaluates the factors influencing the clin- ical outcome of zone I and II flexor tendon repairs in children at our institution. The effects of age, post- operative mobilization protocol, zone I versus zone II injury, whether one or both tendons were lacerated in The Journal of Hand Surgery 1661