Treatment of distal third humeral shaft fractures with posterior minimally invasive plate osteosynthesis (MIPO) with segmental isolation of the radial nerve: minimum one-year follow-up.

Background: Open reduction and internal fixation with plate is one of the most widely used treatments for distal third humeral shaft fractures. The purpose of this study was to report the outcomes of the treatment of distal third humeral shaft fractures with posterior minimally invasive plate osteosynthesis (MIPO) with segmental isolation of the radial nerve.

Methods: We performed an observational, retrospective, consecutive, monocentric, continuous multioperator study. We reviewed 22 distal third humeral shaft fractures treated with posterior MIPO in our institution with an extra-articular distal humerus plate from 2018 to 2021. Inclusion was limited to functionally independent patients with displaced fractures involving the junction of the middle and distal thirds of the humerus and minimum 12-month follow-up for implant removal. We assessed clinical outcomes including range of motion; QuickDASH score; Mayo Elbow Performance Score; and Constant-Murley score.

Results: The average follow-up period of the sample was 31.7 ± 11.6 months (range, 15.7-51.3 months). The average elbow flexion and extension were 146.4° ± 7.3° (range, 120°-150°) and -0.7° ± 3.3° (range, -15° to 0°), respectively. The average shoulder anterior flexion, elevation, and abduction were 178.6° ± 3.6° (range, 170°-180°), 179.1° ± 2.9° (range, 170°-180°), and 140.9° ± 14.8° (range, 110°-160°), respectively. The average external rotation was 88.6° ± 6.4 (range, 65°-90°). The mean visual analog scale score for pain was 1.0 ± 1.6 (range, 0-5) and the mean Mayo Elbow Performance Score was 90.5 ± 9.9 (range, 70-100). The mean QuickDASH and Constant-Murley scores were 4.7 ± 6.8 (range, 0-20.5) and 95.5 ± 5.1 (range, 81-100), respectively. Two patients presented with relevant compromise of radial nerve motor function postoperatively (M3 and M2; the more compromised was preoperative injury). All patients recovered radial nerve neuropraxia within six weeks postoperatively. All fractures achieved union. The average anteroposterior and lateral axis were 175.0 ± 3.6 (168.0°-180.0°) and 177.5 ± 2.0 (173.0°-180.0°), respectively. No superficial or deep infection was reported. No cases of re-displacement of fracture, implant failure, or any other implant-related complication in follow-up were reported. No patient required plate withdrawal.

Conclusion: The results of this study demonstrate that the posterior MIPO technique is a reliable option for treating distal third shaft humeral fractures. The radial nerve must be identified and protected in all cases to prevent palsy.