Microsurgical Needle Retention Does Not Cause Pain or Neurovascular Injury in a Rat Model.

Abstract

Male Sprague-Dawley rats (x̄ weight: 288.9 g) were implanted with a single, 9.0 needle (n = 8) or 8.0 needle (n = 8) orthogonal to the right femoral vessels and sutured in place. A control group (n = 8) underwent sham surgery. Weekly, a cumulative health score evaluating body weight, body condition score, physical appearance, and behavior for each rat was determined. Infrared thermography (°C, FLIR one) of each hindlimb and the difference was obtained on postoperative days 15, 30, 60, and 90. On day 90, animals were euthanatized, hindlimbs were imaged via fluoroscopy, and needles were explanted. The mean, cumulative health score for all cohorts at each weekly timepoint was 0. The mean temperature difference was not significantly different on postoperative days 15 (P = 0.54), 30 (P = 0.97), 60 (P = 0.29), or 90 (P = 0.09). In seven of eight rats, 8.0 needles were recovered and visualized on fluoroscopy. In six of eight rats, 9.0 needles were recovered, but 0/8 needles were visualized on fluoroscopy. Microsurgical needle retention near neurovascular structures may be benign, and imaging for needles smaller than 8.0 may be futile. Further studies should explore microsurgical needle retention potentially through larger animal models.