Abstract
Purpose
The coronoid process is an integral component for elbow stability. In the setting of a comminuted coronoid fracture, where repair is not possible, a prosthetic device may be beneficial in restoring elbow stability. The hypothesis of this in-vitro biomechanical study was that an anatomic coronoid prosthesis would restore stability to the coronoid deficient elbow.
Method
A metal coronoid prosthesis was designed and developed based on CT-derived images adjusted for cartilage thickness. The kinematics and stability of eight fresh-frozen male cadaveric arms (mean age 77.4 years, range 69–92 years) were quantified in the intact state; after collateral ligament sectioning and repair (control state); after a simulated 40% transverse coronoid fracture; and after implantation of a coronoid prosthesis. Elbow flexion was simulated passively with the arm oriented in the varus position and the forearm in pronation. Varus-valgus angulation (VV) and internal-external rotation (IE) of the ulna relative to the humerus were quantified with an electromagnetic tracking system (Flock of Birds, Ascension Technologies, Burlington, VT, static accuracy: 1.8mm position, 0.5 orientation).
Results
No significant difference was found between the intact elbow and the native coronoid control state with collateral ligament repair (mean standard deviation) (VV=0.13.1, p=0.9; IE=0.82.59, p=0.4). A significant decrease in stability was observed following the 40% coronoid fracture (VV=5.73.4, p<0.01; IE=10.93.35, p<0.001). Following coronoid hemi-arthroplasty, no significant difference in stability was found between the coronoid prosthesis and the control state (VV=0.22.7, p=1.0; IE=1.33.0, p=0.8).
Conclusion
An anatomic coronoid prosthesis restores the stability of the coronoid deficient elbow similar to the intact state. Further studies are needed to determine the optimum fixation method of this device and to determine the range of sizes which would be required for the successful commercialization of this device for patient use. Clinical trials will be required to confirm the favourable findings of this in-vitro investigation.
