General Session: Innovative Technologies I - Hall F

Presented by: W. Walsh

Author(s):

W. Walsh(1), R. Oliver(1), C. Christou(1), S. Jalota(2), F. Vizesi(2)

(1) UNSW Australia, Prince of Wales Clinical School, Randwick, NSW, Australia
(2) SeaSpine, Carlsbad, CA, United States

Abstract

Background: Graft materials that can participate as well as initiate bone healing are required in posterolateral fusion. Improving and facilitating surgical implantation of graft materials as well as avoiding graft migration are important surgical considerations. The current study examined the in vivo response of a resorbable mesh pouch containing demineralized bone matrix granules in a validated pre-clinical rabbit posterolateral fusion. The combination of osteoinductive demineralized bone granules in a resorbable mesh pouch removes the need for excipients and facilitated surgical placement.

Methods: Forty skeletally mature female NZ White rabbits were enrolled following ethical approval. A single-level posterolateral intertransverse process surgery was performed bilaterally in the lumbar spine. A pneumatic burr was used to decorticate the host transverse processes. Iliac crest autograft was used as the positive control. The Resorbable Mesh Device (RMD), composed of PLGA mesh pouch filled with 2cc of rabbit DBM, was implanted with 1 cc of iliac crest autograft. Time points of 3 days (n=2 per group), 4 and 8 weeks (n=5 per group) and 12 weeks (n=8) were evaluated using standard endpoints including radiography (X-rays, Faxitrons, Micro-computed tomography), manual palpation, histology and histomorphometry. The paraffin histology slides were analyzed under polarized light for presence of PLGA.

Results: Bilateral fusion in the RMD + autograft group improved with time in a similar manner to the autograft group. No graft migration was noted on radiographic and micro-computed tomography review. Fusion by manual palpation at the 12 week time point was 6 of 8 and 7 of 8 for the RMD and autograft groups respectively. The autograft morsels and the DBM within the device demonstrated signs of new bone formation at 4 weeks along with bony activity on the host bone margins and demonstrated formation of some cortices on the margins of the fusions at 12 weeks based on radiography and micro-CT. The Resorbable Mesh Device + Autograft demonstrated the same histological features observed in the Autograft group at 4, 8 and 12 weeks in terms of new bone formation on the host bone margins as well as in the middle of the fusion, resorption of the graft and remodeling of the fusion versus time. Newly formed woven bone was observed at the interface with the host bone as well as in some areas in the posterolateral fusion space at 4 weeks. Cartilaginous material was noted at 4 weeks which remodelled with time to bone tissue. The fusions continued to mature with time where bone formation was found. The resorbable mesh pouch was completely resorbed between 4 and 8 weeks with no evidence of adverse reactions.

Conclusions: The RMD was able to deliver the graft material without any compromise in healing. Graft containment combined with the osteoinductive capacity of DBM granules achieved fusion.