Mechanical Comparison of Novel Bioabsorbable Plates with Titanium Plates and Small-Series Clinical Comparisons for Metacarpal Fractures

Background: The use of bioabsorbable implants to negate the need for subsequent removal could offer major clinical advantages for the fixation of fractures. The aims of this study were to compare the mechanical properties of novel bioabsorbable plates with those of titanium plates in a fracture model and to demonstrate the clinical results of the use of these new plates for metacarpal fractures. Methods: The first set of experiments compared the mechanical properties of bioabsorbable and titanium plates. Two types of bioabsorbable plates (one-third tubular and semi-tubular in cross-section) made of hydroxyapatite/poly-L-lactide and two types of titanium plates (for 1.5 and 2.0-mm screws) were tested. Each plate was fixed on a polyether ether ketone (PEEK) rod, which was transversely cut at its midsection. The second part of the study compared the clinical results associated with the bioabsorbable and titanium plates that were used in sixteen nonrandomized consecutive patients with metacarpal fractures. Results: The bending strength and stiffness of one-third tubular bioabsorbable plate constructs were comparable with those of titanium plates for 1.5-mm screws, and those of one-half tubular bioabsorbable plates were comparable with those of titanium plates for 2.0-mm screws. The mean torsional strength (and standard deviation) of the semi-tubular bioabsorbable plates (79.0 ± 7.9 N·cm) was significantly greater than that of titanium plates for 2.0 mm screws (56.7 ± 4.0 N·cm) (p < 0.05). There were no significant differences in six-month postoperative clinical results between patients who received bioabsorbable plates and those who received titanium plates (total range of active motion, 267.0° ± 6.0° compared with 250.0° ± 28.3°; grip strength, 92.7% ± 19.7% compared with 86.4% ± 28.6% of that on the contralateral side). Conclusions: The bending strength, stiffness, and torsional strength of novel one-third or semi-tubular bioabsorbable plates, when fixed on a PEEK rod, were comparable with those for titanium plates for 1.5 or 2.0-mm screws. There were no significant differences in clinical results between these two types of plates in a small group of patients after short-term follow-up.