Mechanical Properties and Clinical Results of Novel Bioabsorbable Plates for the Treatment of the Hand Fractures

Abstract

The use of bioabsorbable implants that would negate the need for subsequent removal could offer major clinical advantages for the fixation of fractures. However, previous bioabsorbable plates have had several issues with regard to clinical usage. 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 these new plates for hand fractures. Materials and Methods: The first set of experiments compared the mechanical properties of bioabsorbable and titanium plates. Two types of bioabsorbable plates made of hydroxyapatite/poly-L-lactide (1/3-and 1/2-circle in crosssection) and two types of titanium plates (for 1.5-and 2.0mm 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 studies demonstrated the clinical results of bioabsorbable plates used in 62 cases of 70 hand fractures including 39 metacarpal, 20 distal ulna, 5 distal radius, and 6 radial head fractures since July 2008. The mean age of the patients was 48.4 years (range, 13-89). The follow-up period ranged from 3 month to 4 years 9 months. Results: The bending strength and stiffness of 1/3-circle bioabsorbable plate constructs were comparable with those of titanium plates for 1.5-mm screws, and those of 1/2-circle bioabsorbable plates were comparable with those of titanium plates for 2.0-mm screws. The torsional strength of 1/2-circle bioabsorbable plates (mean ± standard deviation: 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 < .05). The nonunion rate was 2.9% (2 cases in radial head fractures/70 cases). About 4.3% (3/70 cases) was necessary for implant removal because of loose screws in 2 cases of metacarpal fractures and limited range of motion in 1 case of radial head fracture. For the consecutive cases with metacarpal fractures, there were no significant differences in 6-month postoperative clinical results between patients receiving bioabsorbable plates after July 2008 and titanium plates before July 2008 (267.0 ± 6.0 vs 250.0 ± 28.3 degrees of total range of active motion, and 92.7 ± 19.7 vs 86.4 ± 28.6% of contralateral grip strength). Conclusions: The bending strength, stiffness, and torsional strength of novel 1/3-or 1/2-circle bioabsorbable plates, when fixed on a PEEK rod, were comparable with those for titanium plates for 1.5-or 2.0-mm screws. The clinical study of bioabsorbable plates used in hand fractures revealed satisfactory results for union rate, range of motion, and grip strength. For metacarpal fractures, there were no significant differences in clinical results between bioabsorbable and titanium plates.