Comparison of Locking Plate Alone and Locking Plate Combined with 3D Printed Polymethylmethacrylate Augmentation in Treating Proximal Humerus Fractures in the Elderly.

Background: Locking plates are widely used in open reduction internal fixation (ORIF) for proximal humeral fracture (PHF). However, the optimal surgical treatment of unstable, displaced PHF in elderly patients remains controversial. This study aimed to compare the radiological and clinical outcomes of surgical treatment of PHF in the elderly with locking plate (LP) alone and locking plate combined with 3D printed polymethylmethacrylate (PMMA) prosthesis augmentation (LP-PA).

Methods: From May 2015 to April 2021, a total of 97 patients aged ≥ 60 years with acute unstable PHF who underwent osteosynthesis with either LP (46 patients) or LP-PA (51 patients) were retrospectively analyzed. For the LP-PA group, a customized proximal humeral prosthesis made of PMMA cement was intra-operatively fabricated by a three-dimensional (3D) printed prototype mold for the humeral medial support. Radiological outcomes were analyzed by measuring the value of neck-shaft angle (NSA) and humeral head height (HHH). The clinical outcomes were evaluated using Constant-Murley Score (CMS), Disabilities of the Arm Shoulder and Hand (DASH) score, American Shoulder and Elbow Surgeons (ASES) score, and the shoulder range of motion (ROM). Pain was measured using a visual analogue scale (VAS).

Results: At the one-year follow-up, all fractures healed radiologically and clinically. The mean changes of NSA and HHH over the follow-up period were markedly smaller in the LP-PA group (3.8 ± 0.9° and 1.7 ± 0.3 mm) than those in the LP group (9.7 ± 2.1° and 3.2 ± 0.6 mm, both P < 0.0001). The LP-PA group also presented lower DASH score (17.1 ± 3.6), higher ASES score (89.5 ± 11.2) and better ROM in forward elevation (142 ± 26°) and external rotation (59 ± 11°) compared to the LP group (28.9 ± 4.8 for DASH score, P < 0.0001; 82.3 ± 9.0 for ASES score, P < 0.001; 129 ± 21° for forward elevation, P = 0.008; and 52 ± 9° for external rotation, P = 0.001). There was no significant difference in overall complication rate between the two groups, although the complication rate of screw perforation was higher in the LP-PA group (P = 0.172).

Conclusions: For PHF in elderly patients, the combination of LP fixation and PMMA prosthesis augmentation effectively improved humeral head support and reduction maintenance, providing satisfactory outcomes both radiologically and clinically. This technique also reduced the incidence of screw perforation associated with plate fixation alone, making it a reasonable option to ensure satisfactory clinical outcomes.