Morrey Award 2023: radial head donor plug for capitellum osteochondral autograft transfer: a cadaveric biomechanical analysis

Background: Limitations to using the knee as donor cartilage include cartilage thickness mismatch and donor site morbidity. Using the radial head as donor autograft for capitellar lesions may allow for local graft harvest without distant donor site morbidity. The purpose of this study is to demonstrate the feasibility of performing local osteochondral autograft transfer from the nonarticular cartilaginous rim of the radial head to the capitellum. Additionally, we sought to determine the load to failure of the radial head after harvest. Methods: Sixteen matched cadaveric elbows were used. A Kaplan approach was performed in half of the specimens and an extensor digitorum communis split in the other half. 6-mm and 8-mm capitellar cartilage defects were created. A donor plug was harvested from the rim of the radial head and transferred to the capitellum. In half of the specimens, the donor site was backfilled with autograft from the recipient plug. The other half was backfilled with calcium phosphate cement. The radial head was removed from the specimen and biomechanical analysis performed. Results: Both surgical approaches had adequate exposure to access the lateral two-third capitellar lesions in all specimens. The medial third of the capitellum was less accessible in extensor digitorum communis split approaches (1/8) compared to the Kaplan approach (6/8; P = .01). The average cartilage thickness of the peripheral rim of the radial head and capitellum was 2.5 mm (range 1.8-3.2, standard deviation 0.4) and 2.2 mm (range 1.8-3, standard deviation 0.3), respectively. During the procedure, 2 of 8 radial heads fractured in the 8-mm plug group. No radial heads fractured in the 6-mm group (P = .47). Biomechanical testing demonstrated a mean load to failure of 1993N with no difference between groups when stratified by donor plug size or type of backfill. Conclusion: This study demonstrates that the nonarticulating peripheral cartilaginous rim of the radial head could be a local harvest site for osteochondral autograft transfer for capitellar lesions up to 8 mm in diameter. The cartilage thickness of the radial head closely approximates the capitellum. Biomechanical analysis did not demonstrate a significant difference in load to fracture when backfilling the radial head harvest site with autograft bone or calcium phosphate cement. After harvest, the radial head could withstand forces much greater than those seen across the elbow when nonweight-bearing. Further investigation is needed to determine how to mitigate the risk of iatrogenic fracture with this operation.