Resizing and Reshaping Anterior Cruciate Ligament Stump Tissue Does Not Compromise Cell Viability, and Infiltration...

To determine whether a technique to process anterior cruciate ligament (ACL) stump tissue for needle infiltration into tendon grafts for ACL reconstruction would affect the viability of the cells within the tissue or the tensile properties of infiltrated grafts.

ACL stump and Hoffa fat pad tissue was harvested from 13 ACL reconstruction patients and processed. Harvesting involved a standard arthroscopic shaver and an inline suction device. Processing involved 3 steps, 2 syringes, and 3 syringe transfer devices of decreasing size. After processing, tissue could pass through a needle for infiltration into ACL reconstruction tendon grafts. Tissue analysis was performed at each serial step of the processing technique and included cell counts and viability testing. Tensile testing involved 15 matched-pair cadaveric knees, from which bone-patellar tendon-bone (BPTB) grafts, stump tissue, and fat pad tissue were harvested. Harvested and processed tissue was infiltrated into BPTB grafts, and tensile biomechanical testing was performed.

Unprocessed tissue showed average cell viability (ACV) of 72.8% during cell viability testing. After step 1 of the process, ACV was 66.4%; after step 2, ACV was 73.1%; and after step 3, ACV was 67.1%. There was no significant difference in cell viability between processing steps (P = .528). When un-infiltrated control grafts were compared with infiltrated grafts, expected significant differences were found for weight (6.55 ± 1.51 g vs 8.91 ± 0.98 g, P < .001), width (9.53 ± 1.35 mm vs 13.74 ± 2.04 mm, P < .001), thickness (5.2 ± 1.26 mm vs 10.78 ± 2.11 mm, P < .001), and Young's modulus (94.55 ± 47.19 MPa vs 28.57 ± 16.37 MPa, P < .001). There were no significant differences in tensile failure load (536.65 ± 168.00 N vs 509.55 ± 139.31 N, P = .49), deformation at failure (9.34 ± 2.96 mm vs 9.28 ± 3.21 mm, P = .91), or stiffness (97.04 ± 32.34 N/mm vs 86.82 ± 24.37 N/mm, P = .11) between the groups.

A technique to process remnant ACL and fat pad tissue for infiltration does not affect the viability of cells within the tissue. Infiltration of tissue into BPTB graft increases overall volume and mass and does not significantly alter the graft's tensile load to failure when compared with matched controls.

Evaluation of the biomechanical properties of a graft injected with minimally manipulated biologic material obtained at the time of harvest may provide laboratory data on the procedure's safety and viability as a direct delivery method for ACL grafts. These data could contribute to future studies involving clinical application during ACL reconstruction.