Background: The humerus shaft fracture (HSF) is a typical long bone fracture. Following non-surgical therapy, some patients experience delayed or non-union of the HSF. The most common treatment is open reduction and internal fixation (ORIF) with plates and bone grafts. However, substantial tissue dissection increases radial nerve damage and delays union. Because of its minimally invasive nature, the minimally invasive plate osteosynthesis (MIPO) method may be a suitable replacement technique. MIPO helps in protection of soft tissue and nerves in the area of the fracture. 
Methods: All patients were treated with the MIPO method using bone graft implantation. A specific six-hole locking plate was used. Physical examinations and radiological studies were used to monitor the patients' progress. UCLA and the MEPS scoring system assessed shoulder and elbow function. The average follow-up period was six months.
Result: The mean age of patients was 39.8 years (19-73 years). The mean fracture site distance from the elbow joint was 12.1 cm. The mean maximum final rotation was 3.3 degrees. The last rotation alignment was within normal limits. No shortening was detected. Average scores were 35 for UCLA and 100 for MEPS. Radial nerve damage was not reported. Malunion, delayed union, or nonunion did not occur. Mean union time was 2.8 months.
Conclusion: MIPO technique combined with bone transplant causes micromotion at the fracture site, resulting in a better and faster union. Its minimally invasive nature also helps prevent iatrogenic injury to nerves and soft tissue. Less tissue manipulation and dissection help shoulder and elbow function progress more quickly and reduce the rate of malunion. We recommend this method in delayed union and nonunion of HSF patients for better outcomes and lesser complications.