Between January 2012 and December 2016, 216 patients with mid-distal humeral shaft fractures underwent surgery at the departments of orthopedics of the Seventh Medical Center of PLA General Hospital and Beijing Chaoyang Hospital. Of these patients, 28 underwent MIPO and 56 case-matched controls underwent ORIF; all of them had complete 3-year follow-up data. Approximately 33.3% of the patients were female, and the mean age of all patients was 31.7±12.5 years. The follow-up duration was 47.1±7.4 (36–65) months (MIPO group, 47.2±2.2, range 36–60 months; ORIF group, 47.1±7.8, range 36–65 months).
There were 18 men (64.3%) and 10 women (35.7%) in the MIPO group, with a mean age of 36.0 ± 12.3 (range 18–59)). The mechanisms of injury were wrestling in 10 (35.7%) patients, throwing in 9 (32.1%), fall in 6 (21.4%), and car accidents in 3 (10.7%). The classifications were A1 in 13 (46.4%) patients, B1 in 12 (42.9%), A2 in 1 (3.6%), B3 in 1 (3.6%), and C1 in 1 (3.6%) depending on the Orthopaedic Trauma Association (OTA) classification. In the ORIF group, there were 36 males (67.9%) and 18 females (32.1%), with a mean age of 36.8 ± 12.8 (range 18–58) years. The mechanisms of injury were wrestling in 23 (41.1%) patients, throwing in 17 (30.3%), fall in 9 (16.1%), and car accidents in 7 (12.5%). The OTA classifications were A1 in 29 (51.8%) patients, B1 in 18 (32.1%), A2 in 3 (5.4%), C1 in 3 (5.4%), A3 in 2 (3.6%), and B2 in 1 (1.8%). Moreover, four (14.3%) cases in the MIPO group and 7 (12.5%) in the other group had preoperative radial nerve injury. There was no significant difference in the baseline characteristics (Table 1).
The UCLA scores in the MIPO group were great higher than the ORIF group (34.4±1.7 vs. 31.2±3.9, p=0.000). In the MIPO group, 27 (96.4%) patients showed excellent results and 1 patient (3.6%) had a poor result. In the ORIF group, there were 35 (62.5%) excellent cases, 14 (25%) good cases, and 7 (12.5%) poor cases. The MIPO group was highly significantly superior to the ORIF group in terms of UCLA scores and grades (p=0.003). The patient with poor shoulder function in the MIPO group was obese. Due to poor compliance, the shoulder joint did not undergo timely functional exercise, resulting in adhesion around the shoulder joint. In the patients with poor shoulder function in the ORIF group, 3 had nonunion, 2 had myositis ossificans, and 2 had iatrogenic radial nerve injury.
Similar results were observed for MEPS. MEPS in the MIPO group was great higher than the ORIF group (97.9±4.2 vs. 86.7±13.6, p=0.000). In the MIPO group, 27 (96.4%) patients showed excellent results and 1 (3.6%) patient had a good result. In the ORIF group, there were 37 (66.1%) excellent cases, 9 (16.1%) good cases, 8 (14.3%) fair cases, and 2 (3.6%) poor cases. The MEPS grades of the MIPO group were statistically superior to those in the ORIF group (p=0.02). One patient with myositis ossificans and one patient with intraoperative radial nerve injury had poor elbow function in the ORIF group (Table 2).
The operation time was 144.8 ± 36.1 (90–260) min in the MIPO group and 166.5 ± 54.1 (85–300) min in the ORIF group, with a significant reduction of 21.7 min (t = - 2.14, p = 0.036). Intraoperative blood loss was 112.9 ± 75.3 (30–300) mL in the MIPO group and 229.5 ± 112.7 (100–600) mL in the ORIF group, with a highly significant decrease of 116.6 mL (t=5.63, p=0.000). The bone union time was 6.2±1.6 (4–9) months in the MIPO group and 6.0±3.3 (3–20) months in the ORIF group, with no statistical difference (t=0.06, p=0.951).
Iatrogenic nerve injury was not observed in the MIPO group and 4 patients with iatrogenic radial nerve injury (7.1%) were postoperatively identified in the ORIF group with no statistical difference (X2=2.10, p=0.147). Of the patients with iatrogenic nerve injury, two recovered within 4 weeks postoperatively without intervention and two did not recover 6 months postoperatively; these patients underwent radial nerve exploration, revealing that the radial nerve was cut off in one patient and pressed under the plate in another patient.
No deep infections were observed in the MIPO group, whereas 3 cases (5.6%) in the ORIF group developed deep infection; however, all infections were treated with intravenous antibiotic therapy. No statistical difference was found between the two groups (X2=1.56, p=0.21).
All cases in the MIPO group met the standard of bone union within 9 months postoperatively. Three patients (5.6%) in the ORIF group had nonunion, and each nonunion was subsequently managed by implant removal and ORIF with bone graft. There was no statistical difference in the incidence of nonunion between the two groups (X2=1.56, p=0.21).
There were 4 patients (7.1%) with myositis ossificans in the ORIF group; however, this complication was not observed in the MIPO group with no statistical difference between the two groups (X2=2.10, p=0.15). Only one myositis ossificans needed elbow joint release to improve elbow function.
Internal fixation removal was performed in 20 cases in MIPO group without complication and in 14 cases in ORIF group with 2 complications. One patient had radial nerve injury during the surgery, whereas one patient had refracture after surgery in the ORIF group. No statistical difference was observed between two groups (X2=3.04, p=0.08) (Table 2).
The overall major complication rates in midterm follow-up were 0 and 16 (0% vs. 28.6%) in the MIPO and ORIF groups, respectively, which significantly differed between the two groups (X2=9.88, p=0.002). Survival analysis and cumulative complication incidence curves showed that the total major complication rate was highly significantly lower in MIPO group than in ORIF group (p=0.000) (Fig. 3). The Mantel–Haenszel test showed that HR (MIPO/ORIF) was 0.20 with 95% CI of 0.07–0.56, indicating that every five patients who underwent MIPO can avoid one major complication compared with those who underwent ORIF.