  The regeneration of the ruptured scapholunate interosseous ligament (SLIL)
represents a clinical challenge. Here, we propose the use of a
Bone-Ligament-Bone (BLB) 3D-printed polyethylene terephthalate (PET) scaffold
for achieving mechanical stabilisation of the scaphoid and lunate following
SLIL rupture. The BLB scaffold featured two bone compartments bridged by
aligned fibres (ligament compartment) mimicking the architecture of the native
tissue. The scaffold presented tensile stiffness in the range of 260+/-38 N/mm
and ultimate load of 113+/-13 N, which would support physiological loading. A
finite element analysis, using inverse finite element analysis for material
property identification, showed an adequate fit between simulation and
experimental data. The scaffold was then biofunctionalized using two different
methods: injected with a Gelatin Methacryloyl solution containing human
mesenchymal stem cell spheroids or seeded with tendon-derived stem cells and
placed in a bioreactor to undergo cyclic deformation. The first approach
demonstrated high cell viability, as cells migrated out of the spheroid and
colonised the interstitial space of the scaffold. These cells adopted an
elongated morphology suggesting the internal architecture of the scaffold
exerted topographical guidance. The second method demonstrated the high
resilience of the scaffold to cyclic deformation and the secretion of a
fibroblastic related protein was enhanced by the mechanical stimulation. This
process promoted the expression of relevant proteins, such as Tenomodulin,
indicating mechanical stimulation may enhance cell differentiation and be
useful prior to surgical implantation. In conclusion, the PET scaffold
presented several promising characteristics for the immediate mechanical
stabilisation of disassociated scaphoid and lunate and, in the longer-term, the
regeneration of the ruptured SLIL.
