['Although most humeral nonunions are successfully treated with a single procedure, some humeral nonunions are more difficult to heal and require multiple procedures. Current literature does not provide evidence describing how the prognosis for surgical repair in patients who develop humeral diaphyseal nonunions may be affected by initial operative versus nonoperative treatment.', 'The purpose of this study was to assess whether operative versus nonoperative treatment of acute humeral shaft fractures impacts outcome of subsequent repairs of humeral nonunions (NU) including the need for additional surgery and a comparison of pain relief (Visual Analogue Scale for pain) and functional outcome (Short Musculoskeletal Functional Assessment).', 'Thirty-four patients with humeral shaft nonunion were evaluated of which 15 patients had been treated operatively (OF), and 19 patients had been treated nonoperatively (NO) for their initial humerus shaft fracture. All patients underwent plating with autogenous bone graft or allograft ± bone morphogenic protein (BMP) 2 or 7 as their final NU repair surgery prior to healing. We compared functional outcome and pain for both cohorts and determined risk factors for requiring more than 1 nonunion repair surgery.', 'The mean time of final follow-up was 14.7\u2009±\u200910.4\xa0months. Thirty-three of 34 NUs (97.1%) healed. Patients who underwent OF of their original fracture were more likely to require more than 1 NU repair surgery (66.7 vs. 0%, p\u2009<\u20090.01). Of the 15 patients who underwent initial OF, 33.0% required 1 NU surgery, 33.0% required 2 NU surgeries, and 33.0% required 3 NU surgeries. Patients who underwent initial OF were more likely to require >6\xa0months to achieve union (40.0 vs. 10.5%, p\u2009=\u20090.04). At final follow-up, there was no difference in functional outcome or pain scores. Initial OF was the only independent predictor of needing more than 1 NU repair surgery (OR 70.1 CI 2.8-1762.3) to achieve healing.'] Does initial Surgical Treatment of Humeral Shaft Fracture predict Difficulty Healing when Humeral Shaft Nonunion Occurs?