Development of a Novel Hybrid Double-bundle ACL Reconstruction Technique in a Translational Large Animal Model

Transcription

1 Development of a Novel Hybrid Double-bundle ACL Reconstruction Technique in a Translational Large Animal Model Farrah A. Monibi, DVM, Patrick Smith, MD, James P. Stannard, MD, Keiichi Kuroki, DVM, PhD, Chantelle Bozynski, DVM, MSC, Ferris Pfeiffer, PhD, Cristi Cook, DVM, MSC, James Cook, DVM, PhD. University of Missouri Columbia, Columbia, MO, USA. Disclosures: F.A. Monibi: None. P. Smith: 2; Arthrex, Spinal Simplicity. 3B; Arthrex. 4; Spinal Simplicity. J.P. Stannard: 2; Arthrex, RTI, Smith & Nephew, Sonoma. 3B; Depuy Synthes, Smith & Nephew, Sonoma. 5; Kinetic Concepts, Inc.. 7; Theime. K. Kuroki: None. C. Bozynski: None. F. Pfeiffer: None. C. Cook: None. J. Cook: 3B; Arthrex, Schwartz biomedical. 5; Arthrex, Zimmer, Synthes. Introduction: Current pre-clinical large animal models for ACL reconstruction are limited with respect to clinical applicability based on joint anatomy, arthroscopic capabilities, postoperative management, and outcome measures. Therefore, more optimal large animal models for ACL research need to be developed and validated. Dogs have potential advantages as a translational animal model for ACL research based on joint anatomy, clinical pathology, feasibility for diagnostic imaging, ability to perform arthroscopic reconstruction, postoperative rehabilitation protocols and relevant outcome measures (Cook et al, 2014). However, current limitations of canine models for ACL reconstruction include high failure rates of intra-articular grafts because of the difficulty in controlling load and motion in the early postoperative period, as well as the relatively high tibial slope of dogs (Conzemius et al, 2005; Cook 2010). Therefore, the objective of the present study was to describe and validate a novel, translational large animal model for all-inside ACL reconstruction designed to overcome these limitations. Methods: With ACUC approval, adult purpose-bred research dogs (n=12) (mean weight = 22.8 kg) underwent a novel arthroscopic hybrid double-bundle ACL reconstruction technique. Using basket forceps, the antero(cranio)medial band (~3-4 mm diameter) of the native ACL (cranial cruciate ligament) was resected. The remaining portion of the native ACL, the postero(caudo)lateral band, was left intact for this hybrid autograft bundle-native bundle technique. Quadrupled extensor tendon autografts were used for all-inside ACL reconstruction by either suspension fixation in sockets (SUSP)(n=6) or interference screw fixation in tunnels (SCREW)(n=6) (Fig. 1). Contralateral knees were used as nonoperated controls (CONT)(n=12). The dogs were restricted to their kennels with monitored daily out-ofkennel exercise in a confined area for the entire study period. Assessments of lameness, comfortable range of motion of the knee, and knee stability (anterior drawer and internal rotation) were performed weekly throughout the 12-week study period. Dogs were humanely euthanatized 12 weeks after surgery for radiographic, arthroscopic, biomechanical and histologic assessments. Results: All dogs were weightbearing on the operated limbs within 48 hours postoperatively and remained functional with lameness grades 0 to 1 out of 5 at end of study. All grafted knees were judged to be clinically stable based on palpation of cranial (anterior) drawer and internal rotation at each assessment point throughout the study (Table 1). Radiographic assessments of the operated knees obtained 12 weeks postoperatively showed no degenerative or osteoarthritic changes. Arthroscopic evaluation of the operated knees showed no apparent articular cartilage, meniscal pathology, or osteophyte formation. All grafts, except one SCREW graft with partial disruption, and one SCREW graft

2 with apparent laxity in flexion, were intact and taut through range of motion (Fig. 2), and demonstrated linear load vs. displacement curves throughout testing with force and stiffness levels that were 40-50% of the native, intact ACL (CONT) at 12 weeks after reconstruction. Histologic assessment revealed neovascularization and remodeling of the intra-articular portion of all grafts. SUSP grafts in sockets consistently showed direct attachment to bone with four zone integration architecture, while SCREW grafts in tunnels consistently showed a fibrous attachment to bone. Discussion: We report a novel canine model to study ACL reconstruction using an arthroscopic, hybrid autograft bundle-native bundle technique. Clinical, radiographic, arthroscopic, biomechanical and histologic assessments suggest that the reconstructed anteromedial bundle grafts were able to effectively resist experienced load, yet did not fail or allow for development of premature osteoarthritis as is often noted with complete ACL reconstruction in dogs. By preserving the native posterolateral bundle of the ACL with this hybrid double-bundle reconstruction, the knee joint and graft could be protected from the intense loading that is thought to cause early graft failure with rapid development of osteoarthritis in dogs following complete ACL reconstruction. Therefore, this novel translational model effectively overcomes previously reported problems associated with current large animal models for pre-clinical studies on ACL reconstruction. Significance: These data suggest that this translational large animal model allows for valid pre-clinical testing of arthroscopic ACL reconstruction techniques with capabilities for clinical and basic science assessments of outcome.

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5 ORS 2015 Annual Meeting Poster No: 1691