Lateral pterygoid muscle enthesis reconstruction in alloplastic total temporomandibular joint replacement: An animal experiment with histological verification

In current alloplastic total temporomandibular joint replacements (TMJRs) typically the lateral pterygoid muscle (LPM) insertion is sacrificed, affecting joint function. This study assesses a novel additively manufactured TMJR (CADskills BV, Gent, Belgium) designed to enable LPM reinsertion through a scaffold feature on the implant. Thirteen TMJRs were implanted in Swifter crossbreed sheep, with follow-up CT scans after 288 days to evaluate LPM reintegration. Five specimens showed a close approximation between the LPM enthesis and the scaffold. Histological analysis with Masson-Goldner staining and microscopy revealed close bony enthesis alignment with the scaffold, although true bony ingrowth was not observed. One specimen could not be fully evaluated due to preparation issues, limiting conclusions on osseointegration. Random samples from the ramal scaffold showed good integration with the native mandible, with osteogenic activity noted, but no bony ingrowth from the reattached enthesis into the bone grafted titanium scaffold. Despite this, all samples displayed a continuous fibrotic attachment, suggesting functional restoration of the LPM. Findings indicate that while the TMJR design supports fibrotic attachment, further optimization of reattachment techniques, scaffold properties, and post-operative care may improve osseointegration and functional outcomes in future human TMJRs.