Background This study describes the long-term clinical and functional outcomes of patients with post-traumatic Cierny-Mader (C-M) Type III and IV chronic osteomyelitis (CO), managed by considering individual patient differences. Methods Twenty patients who developed CO of the long bones after trauma were included in this study. Data on the demographic characteristics of the patients, clinical and radiological characteristics, and surgical methods applied were collected. The classification system defined by C-M was used for CO classification. The Short Form-36 (SF-36) quality of life scale was used to evaluate the functional outcomes and quality of life of the patients at the end of follow-up. Results The participants included 16 males and four females, with an average age of 39.3 ± 14.5 years. The mean duration of CO was 6.8 ± 7.5 years. The anatomical location of the CO was in the tibia in 15 patients, in the femur in four, and in the radius in one. The mean follow-up time after CO reconstruction was 4.5 ± 1.05 years. According to the C-M anatomical classification, there were nine patients with Type III and 11 with Type IV. According to the C-M physiological classification, there was one patient with Class A, 16 with Class B1, and three with Class B2. Different combinations of surgical procedures were performed on each patient. The average number of surgical interventions performed on the patients was 3.1 ± 1.1. Culture growth was detected in 13 patients. At the end of follow-up, the patients' SF-36 scores were lower than those in the normal population. Conclusion Due to the varied histories of CO and individual differences, it is quite challenging to plan a standard treatment procedure for CO in clinical practice. Successful treatment can be achieved with a long-term multidisciplinary approach and individualized, well-planned treatment methods.