Biomechanical Properties of Bioabsorbable Fixation for Osteochondral Shell Allografts.

This study compares bioabsorbable nail to metal screw fixation of shell osteochondral allograft (OCAs) for compression and shear strength. Cadaveric distal femurs (n = 5) yielding six 1.5 cm shell grafts (n = 30) were used. Three different fixation methods (2.0 and 2.4 mm headed screws, and copolymer absorbable nail) were compared for statistically significant differences (p < 0.05) in contact area, contact pressure, and shear load-to-failure. No significant differences in contact areas existed among groups (224 ± 33.5 mm2; 233.9 ± 20.8 mm2, 220.6 ± 22.7 mm2; p = 0.509 for 2.4, 2.0 mm screw, and nail, respectively). No significant differences in contact pressures existed (1.7 ± 0.6 MPa/mm2, 1.5 ± 0.8 MPa/mm2, 1.4 ± 0.9 MPa/mm2; p = 0.73 for 2.4, 2.0 mm screw, and nail, respectively). Load-to-failure for each was: 280.7 ± 48.4 N for 2.4 mm screws, 245.1 ± 70.6 N for 2.0 mm screws, and 215.2 ± 39.4 N for nails. There were no statistically significant differences in load-to-failure between 2.4 and 2.0 mm screws (p = 0.29) or between 2.0 mm screws and nails (p = 0.23); however, load-to-failure in shear was significantly higher for 2.4 mm screws compared with nails (p = 0.036). Fixation of shell OCAs using a copolymer headed nail provides initial graft-recipient compression similar to fixation using 2.0 and 2.4 mm headed screws. Nails failed in shear at significantly lower load than 2.4 mm screws but not 2.0 mm screws which have proven adequate for clinical healing. This study has clinical relevance, as a copolymer bioabsorbable headed nail (SmartNail) has graft-recipient compression and shear load-to-failure properties that suggest it is viable for shell OCA fixation.

The minipig as a potential model for pedicle screw fixation: morphometry and mechanics.

BACKGROUND: While there are several different animal models for use in the characterization of spinal fixation, none have emerged as a definitive model for comparative studies in spinal fixation methods. The purpose of this study is to establish morphometric data of porcine vertebrae and to characterize the feasibility of pedicle screw fixation in porcine spines for potential comparative human study. METHODS: Four spines from 45 to 50 kg Hanford minipigs were cleaned of soft tissue and analyzed by computed tomography and dual-energy x-ray absorptiometry. Two 5 × 30-mm pedicle screws were placed in each vertebra and tested to failure using a combined moment-load protocol. RESULTS: Pedicle widths were measured from L6-T5. Widths ranged from 7.15 mm (T6) to 9.24 mm (T14). Posterior cortex to anterior cortex depth ranged from 25.9 to 32.6 mm. Mean bone mineral density was 1.0665 g/cm2 (range 1.139-1.016). Force-to-failure demonstrated mean 1171.40 N (+ 115.34). CONCLUSION: Our baseline morphometric and compositional data demonstrate that porcine vertebrae can serve as a useful model for comparative studies due to their similar pedicle widths and bone mineral density to the human vertebra. This biomechanical data could provide a baseline comparison for future studies. This study also suggests that the minipig could be a suitable model for comparative studies due to similarities in pedicle width and bone mineral density to the human vertebrae.

A Biomechanical Study of the Role of the Anterolateral Ligament and the Deep Iliotibial Band for Control of a Simulated Pivot Shift With Comparison of Minimally Invasive Extra-articular Anterolateral Tendon Graft Reconstruction Versus Modified Lemaire Reconstruction After Anterior Cruciate Ligament Reconstruction.

PURPOSE: To determine whether the deep fibers of the iliotibial band (dITB) or the anterolateral ligament (ALL) provides more control of a simulated pivot shift and whether a minimally invasive anterolateral reconstruction (ALR) designed to functionally restore the ALL and dITB is mechanically equivalent to a modified Lemaire reconstruction (MLR). METHODS: Six matched pairs of cadaveric knees (N = 12) were subjected to a simulated pivot shift to evaluate anteroposterior translation; internal rotation; and valgus laxity at 0°, 30°, and 90° of flexion. The anterior cruciate ligament (ACL) was sectioned in all specimens, and retesting was performed. Within each pair, sequential sectioning of the ALL and dITB was performed, followed by testing; the contralateral knee was sectioned in reverse order. Knees underwent ACL reconstruction (ACLR) and repeat testing. Then, MLR (n = 6) or ALR (n = 6) was performed on matched pairs for final testing. RESULTS: Sectioning of the dITB versus ALL (after ACL sectioning) produced significantly more anterior translation at all flexion angles (P = .004, P = .012, and P = .011 for 0°, 30°, and 90°, respectively). The ACL-plus-dITB sectioned state had significantly more internal rotation at 0° versus ACL plus ALL (P = .03). ACLR plus ALR restored native anterior translation at all flexion angles. ACLR plus MLR restored anterior translation to native values only at 0° (P = .34). We found no statistically significant differences between ACLR plus ALR and ACLR plus MLR at any flexion angle for internal rotation or valgus laxity compared with the native state. CONCLUSIONS: ALR of the knee in conjunction with ACLR can return the knee to its native biomechanical state without causing overconstraint. The dITB plays a more critical role in controlling anterior translation and internal rotation at 0° than the ALL. The minimally invasive ALR was functionally equivalent to MLR for restoration of knee kinematics after ACLR. CLINICAL RELEVANCE: The dITB is more important than the ALL for control of the pivot shift. A minimally invasive extra-articular tendon allograft reconstruction was biomechanically equivalent to a modified Lemaire procedure for control of a simulated pivot shift.

Evaluation of a Novel Degradable Synthetic Biomaterial Patch for Augmentation of Tendon Healing in a Large Animal Model.

Tendon injury is common in sports. The standard of care (SOC) for tendon repair is surgical treatment. However, restored tendons often lack complete strength and functionality, and surgical repair is often unsuccessful. This controlled laboratory study investigates the healing of an Artelon patch (AP)-augmented tendon versus tendon repair alone in a preclinical canine patellar tendon defect model. Full-thickness proximal and distal flap defects were created in the patella tendons of eight purpose-bred research mongrel dogs. Dogs were randomly allocated into either the AP-augmented repair group or the SOC group (N = 8; four knees per group). Outcomes measures included limb function and pain; range of motion (ROM) and ultrasound assessment at 2, 4, and 8 weeks; and measurements of elongation, biomechanical testing, and histology at 8 weeks. Data were compared for statistically significant differences to preoperative measures and between groups (p < 0.05). The AP group had higher limb function scores compared with the SOC group at 2, 4, and 8 weeks, with statistically significant differences observed at 2 weeks (AP: 7.1 ± 1.4, SOC: 5.5 ± 0.4, p < 0.05) and 8 weeks (AP: 9.5 ± 0.7, SOC: 7.0 ± 0.9, p < 0.05). The ROM was significantly higher for the AP group at 4 weeks (AP: 105 degrees ± 4, SOC: 89 degrees ± 5, p < 0.05). Pain scores were statistically significantly lower in the AP group at 4 (AP: 0.6 ± 0.5, SOC: 2.2 ± 0.5) and 8 weeks (p < 0.05 for both comparisons). All animals in the AP group displayed full bridging tissue at week 4, while most animals of the SOC group displayed full bridging by week 8. Minimal tendon elongation was observed in both groups. Significantly more force was required to elongate tendons in the AP group compared with the SOC group (p < 0.05). Animals with AP-augmented tendon repair show an earlier regain of function, earlier regain of range of movement, less postoperative pain, and improved tendon strength when compared with animals treated with tendon repair alone.

Biomechanical Analysis of Capsular Repair Versus Arthrex TFCC Ulnar Tunnel Repair for Triangular Fibrocartilage Complex Tears.

Background: This study compares the effectiveness of a peripheral capsular repair with a knotless arthroscopic transosseous ulnar tunnel repair (TR) in restoring distal radioulnar joint (DRUJ) stability and stiffness in the setting of a massive triangular fibrocartilage complex (TFCC) tear. Methods: Eight matched pairs of fresh-frozen cadaveric forearms were tested. Each forearm was tested in supination and pronation using 3-dimensional (3D) optical tracking devices prior to any intervention. Each specimen then underwent a diagnostic wrist arthroscopy and sectioning of the TFCC's deep and superficial fibers. All specimens were then retested to assess instability secondary to the tear. The TFCC was repaired with either a peripheral capsular repair (CR) using three 2-0 polydioxanone sutures or a transosseous ulnar TR using a 2-0 FiberWire, and then retested (statistical significance; P < .05). Results: After TFCC arthroscopic sectioning, all specimens were unstable with a significant increase in translation and a significant decrease in stiffness. TFCC repair with TR resulted in displacement and stiffness similar to the native tissue. CR specimens were found to have significantly greater displacement and significantly decreased stiffness compared with the intact state. Conclusions: Arthroscopic sectioning of the TFCC resulted in DRUJ instability, as measured by stiffness and ulnar translation. TR effectively restored DRUJ stability and demonstrated no significant difference in postoperative stiffness or maximal displacement when compared with the intact specimen in pronation and supination. This study provides biomechanical evidence that an arthroscopic ulnar tunnel technique can restore stability to the DRUJ after a massive TFCC tear.

Subchondroplasty for the treatment of post-traumatic bone marrow lesions of the medial femoral condyle in a pre-clinical canine model.

This study characterizes long-term outcomes associated with subchondroplasty (SCP) treatment for impact-induced subchondral bone marrow lesions (BML) using a validated pre-clinical canine model. With IACUC approval, purpose-bred research hounds (n = 16) underwent arthroscopic impact injury (40N) to both medial femoral condyles. At 3 months, functional assessments, arthroscopy, and MRI were performed and knees (n = 32) were randomly assigned to SCP (3 ml fluoroscopically guided percutaneous injection of AccuFill BSM into BML bone defects) or sham injection (Control). Dogs were assessed at 3, 6, 12, and 24 months after treatment using functional assessments, radiographic evaluation, arthroscopy, and MRI. Dogs were humanely euthanatized at 3, 6, 12, or 24 months after treatment for gross, microCT, and histologic assessments. All knees had focal articular cartilage defects with associated subchondral BMLs, as well as clinical dysfunction, 3 months after injury. At the 3 and 6 months, SCP knees showed more functional impairment than Control knees, however, these differences were not statistically significant. At 1- and 2-year post-treatment, function in SCP knees was better than in Control knees with range of motion being significantly (p < 0.05) better for SCP. Radiographic, arthroscopic, MRI, gross, microCT, and histologic findings matched the functional assessments well with Control being associated with better results at the two early time points and SCP being associated with better results at 1 and 2 years. Clinical significance: SCP treatment using calcium phosphate bone void filler was associated with an initial increase in pain and dysfunction followed by symptomatic benefits for up to 2 years after treatment for post-traumatic femoral condyle BMLs in a preclinical canine model. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2709-2717, 2018.

Use of a Novel Magnesium-Based Resorbable Bone Cement for Augmenting Anchor and Tendon Fixation.

The aim of this study was to assess the efficacy and safety of a novel magnesium-based resorbable bone cement (OsteoCrete, Bone Solutions Incorporated) for anchor and tendon fixation. Cadaveric humeral testing involved straight pull-to-failure of rotator cuff suture anchors; OsteoCrete was injected through one anchor, and a second anchor served as the uninjected control. Testing was conducted 15 minutes post-injection. A canine preclinical model was used to evaluate the safety of the following parameters: Rotator cuff repair: A double-row technique was used to repair transected infraspinatus tendons; OsteoCrete was injected through both anchors in one limb, and the contralateral limb served as the uninjected control. Biceps tenodesis: The transected biceps tendon was implanted into a proximal humeral socket with a transcortical button; OsteoCrete was injected into the socket of one limb, and a screw was used for final fixation in the contralateral control limb. Nondestructive biomechanical testing and histologic assessment were performed after 12 weeks. OsteoCrete-augmented anchors showed significantly higher load-to-failure compared to that with uninjected controls. In cadaveric humeri with reduced bone quality, OsteoCrete increased the mean load-to-failure by 99%. Within the preclinical model, there were no complications or statistically significant biomechanical/histologic differences between the techniques. OsteoCrete has the potential for safely providing improved suture anchor and tissue fixation in patients with poor bone or tissue quality.

Rotator cuff healing using demineralized cancellous bone matrix sponge interposition compared to standard repair in a preclinical canine model.

This Level II study assessed clinically relevant outcomes for repair of large, retracted infraspinatus tendons (ISTs) using a demineralized bone matrix (DBM) sponge (FlexiGraft) hydrated in platelet-rich plasma (PRP) versus direct repair in a validated canine model. Adult research dogs (n = 10) were used. The IST was transected in each shoulder (n = 20) and randomized to direct repair or repair with DBM-PRP interposition at 4 weeks posttransection. At 12 weeks postrepair, dogs were sacrificed, and the repair evaluated by magnetic resonance imaging (MRI), histology, and biomechanical testing. MRI and histology scores were significantly (p < 0.05) better in the DBM-PRP shoulders. Biomechanical testing revealed significantly improved strength of the DBM-PRP repairs at 5 and 10 mm of displacement, as well as for ultimate failure load. In this canine model of retracted IST repair, DBM-PRP sponge hydrated in PRP was considered safe and effective. In addition, use of DBM-PRP was associated with improved MRI and histologic appearance, and improved strength compared to direct repair. CLINICAL SIGNIFICANCE: Based on reported failure rates for repair of large, retracted rotator cuff tears, improving tendon-to-bone healing is critical. Use of DBM combined with PRP shows potential for addressing this critical clinical need. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:906-912, 2018.

Analysis of the s2 alar-iliac screw as compared with the traditional iliac screw: does it increase stability with sacroiliac fixation of the spine?

BACKGROUND CONTEXT: Arthrodesis of the lumbosacral junction continues to be a challenge in pediatric and adult spinal deformity surgery. PURPOSE: To evaluate the biomechanical rigidity of two types of lumbosacral fixation. Our hypothesis was that the use of S2 alar-iliac (S2AI) fixation will result in statistically similar biomechanical fixation as compared with use of an iliac screw with a 95% confidence interval. STUDY SETTING: Controlled biomechanical laboratory METHODS: Ten human cadaveric lumbosacral specimens were separated into two test groups: (1) S2AI (n=5) and (2) iliac screw (n=5). S2AI and iliac screws were placed according to current clinical practice techniques. Specimens were mounted in an unconstrained dual leg stance configuration for testing in flexion, extension, lateral bending, and axial rotation. These loads were induced by moving the offset loading arm 10 mm in the respective direction from the point of neutral motion with displacement control up to a 10 N-m moment, except axial rotation which used a 4 N-m moment. Optical tracking was used to monitor motion of the vertebra, pelvis, and fixation instrumentation during testing. Specimens were tested in intact and instrumented states. The stiffness values between S2AI and iliac screw configurations were compared. DISCLOSURE: The present study received external research support (>$50,000 -<$75,000) from Stryker Spine (Allendale, NJ, USA). RESULTS: There was a consistent trend of increased construct stiffness for all S2AI samples compared with the iliac screw group. However, none of the groups tested reached statistical significance for a 95% confidence interval. CONCLUSIONS: S2AI screws are just as stable as iliac screws with biomechanical testing in flexion, extension, rotation, lateral bending, and axial rotation. Given the similarities of biomechanical testing to human movements, these findings support S2AI screws as a viable option for lumbosacral fixation.

Biomechanical Comparison of Five Posterior Cruciate Ligament Reconstruction Techniques.

No surgical technique recreates native posterior cruciate ligament (PCL) biomechanics. We compared the biomechanics of five different PCL reconstruction techniques versus the native PCL. Cadaveric knees (n = 20) were randomly assigned to one of five reconstruction techniques: Single bundle all-inside arthroscopic inlay, single bundle all-inside suspensory fixation, single bundle arthroscopic-assisted open onlay (SB-ONL), double bundle arthroscopic-assisted open inlay (DB-INL), and double bundle all-inside suspensory fixation (DB-SUSP). Each specimen was potted and connected to a servo-hydraulic load frame for testing in three conditions: PCL intact, PCL deficient, and PCL reconstructed. Testing consisted of a posterior force up to 100 N at a rate of 1 N/s at four knee flexion angles: 10, 30, 60, and 90 degrees. Three material properties were measured under each condition: load to 5 mm displacement, maximal displacement, and stiffness. Data were normalized to the native PCL, compared across techniques, compared with all PCL-intact knees and to all PCL-deficient knees using one-way analysis of variance. For load to 5 mm displacement, intact knees required significantly (p < 0.03) more load at 30 degrees of flexion than all reconstructions except the DB-SUSP. At 60 degrees of flexion, intact required significantly (p < 0.01) more load than all others except the SB-ONL. At 90 degrees, intact, SB-ONL, DB-INL, and DB-SUSP required significantly more load (p < 0.05). Maximal displacement testing showed the intact to have significantly (p < 0.02) less laxity than all others except the DB-INL and DB-SUSP at 60 degrees. At 90 degrees the intact showed significantly (p < 0.01) less laxity than all others except the DB-SUSP. The intact was significantly stiffer than all others at 30 degrees (p < 0.03) and 60 degrees (p < 0.01). Finally, the intact was significantly (p < 0.05) stiffer than all others except the DB-SUSP at 90 degrees. No technique matched the exact properties of the native PCL, but the double bundle reconstructions more closely recreated the native biomechanics immediately after implantation, with the DB-SUSP coming closest to the native ligament. This study contributes new data for consideration in PCL reconstruction technique choice.

Biomechanical Evaluation of Suture Anchor Versus Transosseous Tunnel Quadriceps Tendon Repair Techniques.

PURPOSE: To evaluate the biomechanical fixation strength of suture anchor and transosseous tunnel repair of the quadriceps tendon in a standardized cadaveric repair model. METHODS: Twelve "patella-only" specimens were used. Dual-energy X-ray absorptiometry measurement was performed to ensure equal bone quality amongst groups. Specimens were randomly assigned to either a suture anchor repair of quadriceps tendon group (n = 6) or a transosseous tunnel repair group (n = 6). Suture type and repair configuration were equivalent. After the respective procedures were performed, each patella was mounted into a gripping jig. Tensile load was applied at a rate of 0.1 mm/s up to 100 N after which cyclic loading was applied at a rate of 1 Hz between magnitudes of 50 to 150 N, 50 to 200 N, 50 to 250 N, and tensile load at a rate of 0.1 mm/s until failure. Outcome measures included load to failure, displacement at 1st 100 N load, and displacement after each 10th cycle of loading. RESULTS: The measured cyclic displacement to the first 100 N, 50 to 150 N, 50 to 200 N, and 50 to 250 N was significantly less for suture anchors than transosseous tunnels. There was no statistically significant difference in ultimate load to failure between the 2 groups (P = .40). Failure mode for all suture anchors except one was through the soft tissue. Failure mode for all transosseous specimens but one was pulling the repair through the transosseous tunnel. CONCLUSIONS: Suture anchor quadriceps tendon repairs had significantly decreased gapping during cyclic loading, but no statistically significant difference in ultimate load to failure when compared with transosseous tunnel repairs. Although suture anchor quadriceps tendon repair appears to be a biomechanically superior construct, a clinical study is needed to confirm this technique as a viable alternative to gold standard transosseous techniques. CLINICAL RELEVANCE: Although in vivo studies are needed, these results support the suture anchor technique as a viable alternative to transosseous repair of the quadriceps tendon.

Suspensory Versus Interference Screw Fixation for Arthroscopic Anterior Cruciate Ligament Reconstruction in a Translational Large-Animal Model.

PURPOSE: To compare all-inside cortical-button suspensory fixation in sockets versus interference screw fixation in tunnels with respect to clinical, histologic, and biomechanical assessments of all-soft tissue (AST) tendon autografts used for anterior cruciate ligament (ACL) reconstruction in a canine model. METHODS: By use of a validated "hybrid" double-bundle ACL reconstruction technique (reconstruction of the anteromedial bundle with preservation of the native posterolateral bundle), dogs were randomly assigned to undergo either suspensory fixation in sockets (n = 6) or interference screw fixation in tunnels (n = 6). Contralateral knees were used as nonoperated controls (n = 12). Quadrupled extensor tendon autografts were used for both ACL reconstruction groups. Dogs were assessed radiographically and functionally and humanely euthanized at 12 weeks after surgery for arthroscopic, gross, biomechanical, and histologic assessments. RESULTS: Histologic assessments showed significantly (P = .018) better graft incorporation with 4-zone direct healing to bone for the grafts using suspensory fixation in sockets (16.3 ± 1.5) compared with the grafts using interference screw fixation in tunnels (14.2 ± 2.1). Furthermore, graft healing to bone was significantly better at the aperture (P = .05) and mid-socket (P = .01) location for the group that underwent suspensory fixation in sockets (16.1 ± 1.8 and 16.4 ± 1.9, respectively). CONCLUSIONS: Suspensory fixation of AST grafts in sockets was associated with superior tendon-to-bone healing compared with interference screw fixation in tunnels, with 4-zone direct graft healing to bone seen for femoral and tibial sockets only in the suspensory-fixation group. Biomechanical properties were similar between groups. CLINICAL RELEVANCE: These data provide evidence suggesting that an all-inside ACL reconstruction technique using adjustable-loop cortical-button suspensory fixation in bone sockets has potential clinical advantages for ACL reconstruction using AST grafts.

The Use of Finite Element Analysis to Enhance Research and Clinical Practice in Orthopedics.

Finite element analysis (FEA) is a very powerful tool for the evaluation of biomechanics in orthopedics. Finite element (FE) simulations can effectively and efficiently evaluate thousands of variables (such as implant variation, surgical techniques, and various pathologies) to optimize design, screening, prediction, and treatment in orthopedics. Additionally, FEA can be used to retrospectively evaluate and troubleshoot complications or failures to prevent similar future occurrences. Finally, FE simulations are used to evaluate implants, procedures, and techniques in a time- and cost-effective manner. In this work, an overview of the development of FE models is provided and an example application is presented to simulate knee biomechanics for a specimen with medial meniscus insufficiency. FE models require the development of the geometry of interest, determination of the material properties of the tissues simulated, and an accurate application of a numerical solver to produce an accurate solution and representation of the field variables. The objectives of this work are to introduce the reader to the application of FEA in orthopedic analysis of the knee joint. A brief description of the model development process as well as a specific application to the investigation of knee joint stability in geometries with normal or compromised medial meniscal attachment is included. Significant increases in stretch of the anterior cruciate ligament were predicted in specimens with medial meniscus insufficiency (such behavior was confirmed in corresponding biomechanical testing). It can be concluded from this work that FE analysis of the knee can provide significant new information with which more effective clinical decisions can be made.

Multiple injections of leukoreduced platelet rich plasma reduce pain and functional impairment in a canine model of ACL and meniscal deficiency.

Platelet rich plasma (PRP) is used to treat many musculoskeletal disorders. We used a canine model to determine the effects of multiple intra-articular injections of leukoreduced PRP (ACP) on anterior cruciate ligament healing, meniscal healing, and progression of osteoarthritis (OA). With Animal Care and Use Committee (ACUC) approval, 12 dogs underwent partial ACL transection and meniscal release in one knee. At weeks 1, 2, 3, 6, and 8 after insult, dogs were treated with intra-articular injections (2 ml) of either ACP (n = 6) or saline (n = 6). Dogs were assessed over 6 months to determine comfortable range of motion (CROM), lameness, pain, effusion, kinetics, and radiographic and arthroscopic assessments. At 6-month endpoint, dogs were assessed for ACL material properties and histopathology. Saline-treated dogs had significantly (p < 0.04) more CROM loss, significantly (p < 0.01) more pain, significantly (p < 0.05) more severe lameness, significantly (p < 0.05) lower function, and significantly (p < 0.05) lower %Total Pressure Index in affected hindlimbs compared to ACP-treated dogs. Radiographic OA increased significantly (p < 0.01) over time within each group. Arthroscopically, saline-treated knees showed moderate to severe synovitis, further ACL disruption, and medial compartment cartilage loss, and ACP-treated knees showed evidence of ACL repair and less severe synovitis. ACL material properties in ACP-treated knees were closer to normal than in saline-treated knees, however, the differences were not statistically significant. ACL histopathology was significantly (p< 0.05) less severe in ACP-treated knees compared to saline-treated knees. Five intra-articular injections of leukoreduced PRP had beneficial effects for ACL healing, improved range of motion, decreased pain, and improved limb function for up to 6 months in this model.

Optimising femoral-head osteochondral allograft transplantation in a preclinical model.

BACKGROUND/OBJECTIVE: Osteochondral autografting and allografting of the femoral head have been described as treatments for avascular necrosis without segmental collapse, fracture, osteochondritis dissecans, and tumours. One long-term study reported that 80% of nonsteroid-treated patients had successful outcomes. Most data are compiled from small case reports or series. Although these results are encouraging, to the authors' knowledge, there is no basic scientific evidence regarding optimal graft source or technique reported in the peer-reviewed literature. The objective of this study was to create a translational canine model to compare femoral-head osteochondral autografts and allografts with respect to safety and efficacy. METHODS: With Institutional Animal Care and Use Committee approval, skeletally mature hound-mix dogs (n = 6) weighing >20 kg underwent aseptic surgical implantation of osteochondral grafts using a craniolateral approach to the hip, without dislocation. Three graft options were evaluated: small auto (n = 3), 6-mm-diameter autograft from the trochlear ridge of the ipsilateral knee; small allo (n = 3), 6-mm-diameter fresh (21-day storage) allograft from a size-matched canine femoral head; or large allo (n = 3), 14-mm-diameter fresh (21-day storage) allograft from a size-matched canine femoral head. Small grafts were implanted into the same femoral head of three dogs, and large grafts were implanted alone in the other three dogs. The dogs were allowed unrestricted activity in their runs, and were walked on a leash for 15 minutes 5 times/wk. The outcome measures included functional, radiographic, and arthroscopic assessments at 8 weeks, and functional, chondrocyte viability, and histologic assessments at 6 months after surgery. The pre- and postoperative data were compared for statistically significant (p < 0.05) differences. Based on data from the canine study, four human patients underwent fresh (<28-day storage) osteochondral allografting using large (>30-mm diameter) size-matched femoral-head grafts. The radiographic, quality of life, and functional assessments were captured postoperatively. RESULTS: All grafts had >80% chondrocyte viability at the time of implantation. All grafts showed radiographic evidence for integration into host bone. Small auto and small allo showed significant (p < 0.05) loss in range of motion, chondrocyte viability, and articular-cartilage integrity 8 weeks after implantation, whereas large allo maintained viability and structural integrity throughout the study period. The large-allo dogs maintained full hip range of motion and hindlimb function. A similar type of large allograft (>30 mm) was performed in the four human patients. Due to the defect size, three out of the four human patients required two large allografts at the time of implantation. At the time of this manuscript's acceptance, patient follow-up ranged from 4 months to 18 months. All human patients were full weight-bearing without an assistive device, and showed no evidence of graft failure or progressive arthrosis. CONCLUSION: These data provide initial translational and clinical evidence for large osteochondral allografts as a potential option for functional resurfacing of full-thickness cartilage defects of the femoral head.

A canine hybrid double-bundle model for study of arthroscopic ACL reconstruction.

Development and validation of a large animal model for pre-clinical studies of intra-articular anterior cruciate ligament (ACL) reconstruction that addresses current limitations is highly desirable. The objective of the present study was to investigate a translational canine model for ACL reconstruction. With institutional approval, adult research hounds underwent arthroscopic debridement of the anteromedial bundle (AMB) of the ACL, and then either received a tendon autograft for "hybrid double-bundle" ACL reconstruction (n = 12) or no graft to remain ACL/AMB-deficient (n = 6). Contralateral knees were used as non-operated controls (n = 18) and matched canine cadaveric knees were used as biomechanical controls (n = 6). Dogs were assessed using functional, diagnostic imaging, gross, biomechanical, and histologic outcome measures required for pre-clinical animal models. The data suggest that this canine model was able to overcome the major limitations of large animal models used for translational research in ACL reconstruction and closely follow clinical aspects of human ACL reconstruction. The "hybrid double-bundle" ACL reconstruction allowed for sustained knee function without the development of osteoarthritis and for significantly improved functional, diagnostic imaging, gross, biomechanical, and histologic outcomes in grafted knees compared to ACL/AMB-deficient knees.

Biomarkers Affected by Impact Severity during Osteochondral Injury.

Osteochondral injury elevates the risk for developing posttraumatic osteoarthritis (PTOA). Therefore, our objective was to evaluate the relationship between impact severity during injury to cell viability and biomarkers possibly involved in PTOA. Osteochondral explants (6 mm, n = 72) were harvested from cadaveric femoral condyles (N = 6). Using a test machine, each explant (except for No Impact) was subjected to mechanical impact at a velocity of 100 mm/s to 0.25, 0.5, 0.75, 1.0, or 1.25 mm maximum compression corresponding to Low, Low-Moderate, Moderate, Moderate-High, or High impact groups. Cartilage cell viability, collagen content, and proteoglycan content were assessed at either day 0 or after 12 days of culture. Culture media were assessed for prostaglandin E2 (PGE2); nitric oxide; granulocyte macrophage colony-stimulating factor (GM-CSF); interferon gamma (IFNγ); interleukin (IL)-2, -4, -6, -7, -8, -10, -15, -18; interferon gamma-induced protein 10 (IP-10); keratinocyte-derived chemoattractant (KC); monocyte chemoattractant protein-1 (MCP-1); tumor necrosis factor alpha (TNFα); and matrix metalloproteinase-2, -3, -8, -9, -13. There was increased impact energy absorbed for the High group compared with the Moderate-High group, Moderate group, and Low-Moderate group (p = 0.011, 0.048, 0.008, respectively). At day 0, there was decreased area cell viability for the High group compared with the Low-Moderate group (p = 0.035). At day 1, PGE2 was increased for the High group compared with the Moderate, Low-Moderate, Low, and No Impact groups (p ≤ 0.01). Cumulative PGE2 was increased for the Moderate-High and High groups compared with the Moderate, Low-Moderate, Low, and No Impact groups (p ≤ 0.036). At day 1, MCP-1 was increased for the Moderate-High and High groups compared with the Low and No Impact groups (p ≤ 0.032). Impact to osteochondral explants resulted in multiple levels of severity. PGE2 was sensitive to impact severity which may justify its use as a clinically measurable biomarker after joint injury for monitoring early PTOA.

A novel system improves preservation of osteochondral allografts.

BACKGROUND: Osteochondral allografting is an option for successful treatment of large articular cartilage defects. Use of osteochondral allografting is limited by graft availability, often because of loss of chondrocyte viability during storage. QUESTIONS/PURPOSES: The purpose of this study was to compare osteochondral allografts implanted in canine knees after 28 days or 60 days of storage for (1) initial (1 week) safety and feasibility; (2) integrity and positioning with time (12 weeks and 6 months); and (3) gross, cell viability, histologic, biochemical, and biomechanical characteristics at an endpoint of 6 months. METHODS: With Institutional Animal Care and Use Committee approval, adult dogs (n=16) were implanted with 8-mm cylindrical osteochondral allografts in the lateral and medial femoral condyles of one knee. Osteochondral allografts preserved for 28 or 60 days using either the current tissue bank standard-of-care (SOC) or a novel system (The Missouri Osteochondral Allograft Preservation System, or MOPS) were used, creating four treatment groups: SOC 28-day, MOPS 28-day, SOC 60-day, and MOPS 60-day. Bacteriologic analysis of tissue culture and media were performed. Dogs were assessed by radiographs and arthroscopy at interim times and by gross, cell viability, histology, biochemistry, and biomechanical testing at the 6-month endpoint. RESULTS: With the numbers available, there was no difference in infection frequency during storage (5% for SOC and 3% for MOPS; p=0.5). No infected graft was implanted and no infections occurred in vivo. MOPS grafts had greater chondrocyte viability at Day 60 (90% versus 53%; p=0.002). For 60-day storage, MOPS grafts were as good as or better than SOC grafts with respect to all outcome measures assessed 6 months after implantation. CONCLUSIONS: Donor chondrocyte viability is important for osteochondral allograft success. MOPS allows preservation of chondrocyte viability for up to 60 days at sufficient levels to result in successful outcomes in a canine model of large femoral condylar articular defects. CLINICAL RELEVANCE: These findings provide a promising development in osteochondral allograft technology that can benefit the quantity of grafts available for use and the quality of grafts being implanted.

The histologic and biomechanical response of two commercially available small glenoid anchors for use in labral repairs.

BACKGROUND: This study examined histologic characteristics and biomechanical performance of 2 commercially available, small glenoid anchors. METHODS: Adult research dogs (n = 6) were used for histologic analysis. Anchors were inserted into the lateral rim of the glenoid using the manufacturer's protocol. The dogs were humanely euthanatized 8 weeks after anchor implantation, and the glenoids were collected for histologic analysis. Bone socket width data were compared for statistically significant (P < .05) differences. In addition, 4 matched pairs (n = 8) of human cadaveric glenoids were instrumented with 1 BioComposite SutureTak (Arthrex, Naples, FL, USA) and 1 JuggerKnot (Biomet, Warsaw, IN, USA) suture anchor in the anterior-inferior quadrant. Anchor constructs were preloaded to 5 N, cycled from 5 to 25 N for 100 cycles, and then pulled to failure. RESULTS: All JuggerKnot anchor sites were cyst-like cavities with a rim of dense lamellar bone. All BioComposite SutureTak anchor sites contained intact anchors with close approximation of anastomosing trabeculae of lamellar bone. At 8 weeks after implantation, mean socket width of the JuggerKnot anchor sites was 6.3 ± 2.5 mm, which was significantly (P = .013) larger than the mean socket width of 2.7 ± 0.7 mm measured for the BioComposite SutureTak anchor sites. The JuggerKnot anchor demonstrated larger displacements during subfailure cyclic loading (2.9 ± 1.0 mm compared with 1.3 ± 0.4 mm) and load to failure tests (13.7 ± 6.6 mm compared with 3.2 ± 0.5 mm). Statistical differences (P < .01) existed in every category except ultimate load. CONCLUSIONS: Based on the biomechanical in human bone and histologic findings in canine subjects, the all-suture anchor may be at risk for clinical failure.

Evaluation of synthetic osteochondral implants.

This translational animal model study was designed to assess function, bone ingrowth and integration, and joint pathology associated with two different synthetic, bilayered osteochondral implants over a 3-month period after implantation into the femoral condyles of dogs. SynACart-Titanium (n = 6) and SynACart-PEEK (n = 6) (Arthrex, Naples, FL, and Sites Medical, Columbia City, IN) implants were press-fit into the lateral or medial femoral condyle (alternating location) of purpose-bred adult research dogs. Dogs were humanely euthanized 3 months after surgery and the operated knees were assessed radiographically, arthroscopically, grossly, and histologically. Based on all assessments, both types of implants were well tolerated and safe with no evidence for infection, migration, or rejection. Half of the SynACart-PEEK implants showed radiographic and histologic evidence of poor incorporation with all of these being in the lateral femoral condyle. SynACart-Titanium implants were considered effective in terms of integration into bone, lack of damage to surrounding and apposing articular cartilage, and maintenance of implant integrity and architecture for the duration of the study.