Patient-specific 3D-printed shelf implant for the treatment of hip dysplasia: Anatomical and biomechanical outcomes in a canine model

A solution for challenging hip dysplasia surgery could be a patient-specific 3D-printed shelf implant that is positioned extra-articular and restores the dysplastic acetabular rim to normal anatomical dimensions. The anatomical correction and biomechanical stability of this concept were tested in a canine model that, like humans, also suffers from hip dysplasia. Using 3D reconstructed computed tomography images the 3D shelf implant was designed to restore the radiological dysplastic hip parameters to healthy parameters. It was tested ex vivo on three dog cadavers (six hips) with hip dysplasia. Each hip was subjected to a biomechanical subluxation test, first without and then with the 3D shelf implant in place. Subsequently, an implant failure test was performed to test the primary implant fixation. At baseline, the dysplastic hips had an average Norberg angle of 88 +/- 3 degrees and acetabular coverage of 47 +/- 2% and subluxated at an average of 83 +/- 2 degrees of femoral adduction. After adding the patient-specific shelf implants the dysplastic hips had an average Norberg angle of 122 +/- 2 degrees and acetabular coverage of 67 +/- 3% and subluxated at an average of 117 +/- 2 degrees of femoral adduction. Implant failure after primary implant fixation occurred at an average of 1330 +/- 320 Newton. This showed that the patient-specific shelf implants significantly improved the coverage and stability of dysplastic hips in a canine model with naturally occurring hip dysplasia. The 3D shelf is a promising concept for treating residual hip dysplasia with a straightforward technology-driven approach; however, the clinical safety needs to be further investigated in an experimental proof-of-concept animal study.