ORIGINAL ARTICLE Unilateral external fixator in the treatment of humeral shaft fractures: results of a single center retrospective study M. Basso 1 • M. Formica 1 • L. Cavagnaro 1 • M. Federici 2 • M. Lombardi 2 • F. Lanza 2 • L. Felli 1 Received: 22 March 2017 / Accepted: 9 April 2017 Ó Istituto Ortopedico Rizzoli 2017 Abstract Background The aim of our work is to evaluate and crit- ically analyze long-term clinical and radiological data of a new unilateral external fixator (MIKAI KIT FEPÓ—Mikai S.p.A, Genoa, Italy), in the treatment of humeral shaft fractures. Materials and methods We reviewed 47 patients affected by humeral fractures that underwent surgery from July 2010 to March 2016 with unilateral external fixator. Demographic characteristics of the patients were recorded, which included age, sex and baseline comorbidities and mechanism of injury. Surgical data such as time of surgery and time of fixation according to AO-type of fracture, clinical objective and subjective outcomes were collected. Results The mean follow-up was 50.4 months (range 12–74). The patients’ average age was 41.8 years (range 14–92). Mean surgical time was 66.8 (±37.7 min); and mean time of fixation was 4.5 (±1.7 months). We observed five delayed union (10.6%); one refracture (2.1%); and one case of non-union (2.1%) who underwent a revision sur- gery with nailing. No malunion was detected. Average quick-DASH was 11.7 (±14.8). The mean Constant Score at final follow-up was 81.5 (±14). 95.8% of patients were satisfied of our treatment. According to SF-12 scores, we observed 44 (93.6%) good results and 3 (6.4%) poor results. Conclusion We suggest the use of MIKAI KIT FEPÓ as a feasible option in the treatment of humeral shaft fractures. We reported optimal clinical and radiological outcomes at long-term follow-up. We advocate more powerful evidence to validate this new possible approach. Keywords Humeral shaft fracture Á External fixation Á Radial nerve palsy Á Closed reduction Á Treatment Á Outcome Introduction Fractures of humeral shaft include approximately 2–3% of all fractures and 20% of upper extremity fractures [1]. Their average incidence is of 14 out of 100,000 [2]. Humeral shaft fractures are mostly frequent in males under 50 years, after a high-energy trauma; and in females over 70 years with osteoporotic bone [3]. Humeral shaft extends from the proximal border of pectoralis major insertion to the supracondylar ridge. In this part of humerus, the spiral grove, containing the radial nerve, serves as a useful landmark. The most dangerous complication of this type of fracture is damage to the radial nerve [4]. Radial nerve lesions occur in 11.8% of all humeral shaft fractures, mostly associated with a spiral distal third fractures [5]. Other possible complications that may happen in humeral shaft fractures are non-union, malunion or brachial artery injury. Non-union in humerus is defined as the radiographic detection of delayed consolidation after 6–8 months from treatment [6]. Angulation of more than 30° varus or valgus and more than 20° flessum or recurvatum or limb short- ening more than 3 cm are scarcely tolerated by the patient & M. Basso marco.basso24@gmail.com 1 Clinica Ortopedica, IRCCS Azienda Ospedaliera Universitaria San Martino – IST, Istituto Nazionale per la Ricerca sul Cancro, Largo Rosanna Benzi, 10, 16132 Genoa, GE, Italy 2 Department of Orthopaedics and Trauma Surgery, Azienda Ospedaliera Santa Corona, Viale 25 Aprile, 38, 17027 Pietra Ligure, SV, Italy 123 Musculoskelet Surg DOI 10.1007/s12306-017-0473-0