Aligned Gelatin Microribbon Scaffolds with Hydroxyapatite Gradient for Engineering the Bone-Tendon Interface.

Injuries of the bone-to-tendon interface, such as rotator cuff and anterior cruciate ligament tears, are prevalent musculoskeletal injuries, yet effective methods for repair remain elusive. Tissue engineering approaches that use cells and biomaterials offer a promising potential solution for engineering the bone-tendon interface, but previous strategies require seeding multiple cell types and use of multiphasic scaffolds to achieve zonal-specific tissue phenotype. Furthermore, mimicking the aligned tissue morphology present in native bone-tendon interface in three-dimensional (3D) remains challenging.

Safety of Releasing the Volar Capsule During Open Treatment of Distal Radius Fractures: An Analysis of the Extrinsic Radiocarpal Ligaments' Contribution to Radiocarpal Stability.

Purpose: The contribution of the extrinsic radiocarpal ligaments to carpal stability continues to be studied. Clinically, there is a concern for carpal instability from release of the volar extrinsic ligaments during volar plating of distal radius fractures in which the integrity of the dorsal ligaments may be unknown. The primary hypothesis of this study was that serial sectioning of radiocarpal ligaments would lead to progressive ulnar translation of the carpus.

Rotational Stability of Scaphoid Waist Nonunion Bone Graft and Fixation Techniques.

Purpose: Rotational instability of scaphoid fracture nonunions can lead to persistent nonunion. We hypothesized that a hybrid Russe technique would provide improved rotational stability compared with an instrumented corticocancellous wedge graft in a cadaver model of scaphoid nonunion.

Methods: A volar wedge osteotomy was created at the scaphoid waist in 16 scaphoids from matched-pair specimens.

Interlocking screw configuration influences distal tibial fracture stability in torsional loading after intramedullary nailing.

Purpose: This study evaluated the influence of fracture obliquity and locking screw configuration on interfragmentary motion during torsional loading of distal metaphyseal tibial fractures fixed by intramedullary (IM) nailing.

Methods: The stability of six IM nail locking screw configurations used to fix distal metaphyseal tibial fractures of various obliquities was evaluated. A coronal osteotomy from proximal lateral to distal medial was made in sawbone tibiae at different obliquities from 0° to 60°.

Contributions of the Capsule and Labrum to Hip Mechanics in the Context of Hip Microinstability.

Background: Hip microinstability and labral pathology are commonly treated conditions with increasing research emphasis. To date, there is limited understanding of the biomechanical effects of the hip capsule and labrum on controlling femoral head motion.

Purpose/hypothesis: The purpose of this study was to determine the relative role of anterior capsular laxity and labral insufficiency in atraumatic hip microinstability.

The Relationship Between the Tensile and the Torsional Properties of the Native Scapholunate Ligament and Carpal Kinematics.

Purpose: The purpose of this exploratory study was to examine the relationship between the tensile and the torsional properties of the native scapholunate interosseous ligament (SLIL) and kinematics of the scaphoid and lunate of an intact wrist during passive radioulnar deviation.

Methods: Eight fresh-frozen cadaveric specimens were transected at the elbow joint and loaded into a custom jig. Kinematic data of the scaphoid and lunate were acquired in a simulated resting condition for 3 wrist positions-neutral, 10° radial deviation, and 30° ulnar deviation-using infrared-emitting rigid body trackers.

Biomechanical comparison of bone-screw-fasteners versus traditional locked screws in plating female geriatric bone.

Objectives: To biomechanically compare plated constructs using nonlocking bone-screw-fasteners with interlocking threads versus locking screws with traditional buttress threads in geriatric female bone.

Methods: Eleven matched pairs of proximal and distal segments of geriatric female cadaveric tibias were used to create a diaphyseal fracture model. Nonlocking bone-screw-fasteners or locking buttress threaded screws were applied to a locking compression plate on the anterolateral aspect of the tibia placed in bridge mode.

Influence of fracture obliquity and interlocking nail screw configuration on interfragmentary motion in distal metaphyseal tibia fractures.

The indications for the use of intramedullary (IM) nails have been extended to include extra-articular distal metaphyseal tibia fractures. We hypothesize that interfragmentary motion during physiologic compressive loading of distal tibia fractures is influenced by fracture obliquity and can be modulated by interlocking screw configuration. Sawbone specimens were osteotomized with frontal plane obliquities ranging from 0° to 60° and then fixed by IM nailing with six interlocking screw configurations.

Ankle joint contact loads and displacement in syndesmosis injuries repaired with Tightropes compared to screw fixation in a static model.

Background: The effect of syndesmotic fixation on restoration of pressure mechanics in the setting of a syndesmotic injury is largely unknown. The purpose of this study is to examine the contact mechanics of the tibiotalar joint following syndesmosis fixation with screws versus a flexible fixation device for complete syndesmotic injury.

Methods: Six matched pairs of cadaveric below knee specimens were dissected and motion capture trackers were fixed to the tibia, fibula, and talus and a pressure sensor was placed in the tibiotalar joint.

The Role of Anterior Capsular Laxity in Hip Microinstability: A Novel Biomechanical Model.

Background: Hip microinstability is an increasingly recognized source of hip pain and disability. Although the clinical entity has been well described, the pathomechanics of this disease remain poorly understood.

Purpose/hypothesis: The purpose of this study was to determine the role of capsular laxity in atraumatic hip microinstability.

Augmentation of chronic rotator cuff healing using adipose-derived stem cell-seeded human tendon-derived hydrogel.

Rotator cuff (RTC) repair outcomes are unsatisfactory due to the poor healing capacity of the tendon bone interface (TBI). In our preceding study, tendon hydrogel (tHG), which is a type I collagen rich gel derived from human tendons, improved biomechanical properties of the TBI in a rat chronic RTC injury model. Here we investigated whether adipose-derived stem cell (ASC)-seeded tHG injection at the repair site would further improve RTC healing.

Knotless Anchors in Acetabular Labral Repair: A Biomechanical Comparison.

Purpose: To analyze the failure mechanism, stiffness, and pullout strength of acetabular knotless suture anchors.

Methods: Seven suture anchors were tested in high-density (0.48 g/cc) synthetic blocks.

The effects of a functionally-graded scaffold and bone marrow-derived mononuclear cells on steroid-induced femoral head osteonecrosis.

Osteonecrosis of the femoral head (ONFH) is a debilitating disease that may progress to femoral head collapse and subsequently, degenerative arthritis. Although injection of bone marrow-derived mononuclear cells (BMMCs) is often performed with core decompression (CD) in the early stage of ONFH, these treatments are not always effective in prevention of disease progression and femoral head collapse. We previously described a novel 3D printed, customized functionally-graded scaffold (FGS) that improved bone growth in the femoral head after CD in a normal healthy rabbit, by providing structural and mechanical guidance.

The Effect of Growth Differentiation Factor 8 (Myostatin) on Bone Marrow-Derived Stem Cell-Coated Bioactive Sutures in a Rabbit Tendon Repair Model.

We have reported that bioactive sutures coated with bone marrow-derived mesenchymal stem cells (BMSCs) enhance tendon repair strength in an in vivo rat model. We have additionally shown that growth differentiation factor 8 (GDF-8, also known as myostatin) simulates tenogenesis in BMSCs in vitro. The purpose of this study was to determine the possibility of BMSC-coated bioactive sutures treated with GDF-8 to increase tendon repair strength in an in vivo rabbit tendon repair model.

Bennett Fractures: A Biomechanical Model and Relevant Ligamentous Anatomy.

Purpose: This study examined a palmar beak fracture model to determine which thumb carpometacarpal (CMC) joint ligament is the primary ligament relevant to the pattern of injury.

Methods: Six fresh-frozen cadaveric wrists were used. The radius, ulna, and first metacarpal were secured and tested with a materials testing system, holding the wrist in 20° extension, 20° ulnar deviation, and 30° palmar abduction of the first metacarpal.

Functionally Graded, Bone- and Tendon-Like Polyurethane for Rotator Cuff Repair.

Critical considerations in engineering biomaterials for rotator cuff repair include bone-tendon-like mechanical properties to support physiological loading and biophysicochemical attributes that stabilize the repair site over the long-term. In this study, UV-crosslinkable polyurethane based on quadrol (Q), hexamethylene diisocyante (H), and methacrylic anhydride (M; QHM polymers), which are free of solvent, catalyst, and photoinitiator, is developed. Mechanical characterization studies demonstrate that QHM polymers possesses phototunable bone- and tendon-like tensile and compressive properties (12-74 MPa tensile strength, 0.

Headless compression screw for horizontal medial malleolus fractures.

Background: Horizontal medial malleolus fractures are caused by the application of rotational force through the ankle joint in several orientations. Multiple techniques are available for the fixation of medial malleolar fractures.

Methods: Horizontal medial malleolus osteotomies were performed in eighteen synthetic distal tibiae and randomized into two fixation groups: 1) two parallel unicortical cancellous screws or 2) two Acutrak 2 headless compression screws.

Tensile and Torsional Structural Properties of the Native Scapholunate Ligament.

Purpose: The ideal material for reconstruction of the scapholunate interosseous ligament (SLIL) should replicate the mechanical properties of the native SLIL to recreate normal kinematics and prevent posttraumatic arthritis. The purpose of our study was to evaluate the cyclic torsional and tensile properties of the native SLIL and load to failure tensile properties of the dorsal SLIL.

Methods: The SLIL bone complex was resected from 10 fresh-frozen cadavers.

Comparison of mechanical compressive properties of commercial and autologous fibrin glues for tissue engineering applications.

Background: Fibrin glues are widely used in orthopedic surgery as adhesives and hemostatic agents. We evaluated the compressive properties of selected fibrin glues in order to identify which are appropriate for tissue regeneration applications subject to compression.

Methods: Uniaxial unconfined compression tests were performed on fibrin gels prepared from commercial and autologous products: (1) Evicel (Ethicon), (2) Tisseel (Baxter), (3) Angel (Arthrex), and (4) ProPlaz (Biorich).

Customized, degradable, functionally graded scaffold for potential treatment of early stage osteonecrosis of the femoral head.

Osteonecrosis of the femoral head (ONFH) is a debilitating disease that results in progressive collapse of the femoral head and subsequent degenerative arthritis. Few treatments provide both sufficient mechanical support and biological cues for regeneration of bone and vascularity when the femoral head is still round and therefore salvageable. We designed and 3D printed a functionally graded scaffold (FGS) made of polycaprolactone (PCL) and β-tricalcium phosphate (β-TCP) with spatially controlled porosity, degradation, and mechanical strength properties to reconstruct necrotic bone tissue in the femoral head.

Gliding Resistance After Epitendinous-First Repair of Flexor Digitorum Profundus in Zone II.

Purpose: The importance of flexor tendon repair with both core and epitendinous suture placement has been well established. The objective of this study was to determine whether suture placement order affects gliding resistance and bunching in flexor digitorum profundus tendons in a human ex vivo model.

Methods: The flexor digitorum profundus tendons of the index, middle, ring, and little fingers of paired cadaver forearms were tested intact for excursion and mean gliding resistance in flexion and extension across the A2 pulley.

Cyclic and Load to Failure Properties of All-Suture Anchors in Synthetic Acetabular and Glenoid Cancellous Bone.

Purpose: To evaluate the cyclic displacement, maximum load to failure, and failure mode of multiple all-suture anchors (ASAs) in 2 different densities of sawbones cancellous bone substitute.

Methods: Anchors tested included the Suturefix Ultra 1.7 mm, JuggerKnot 1.

Buttress Plating Versus Anterior-to-Posterior Lag Screws for Fixation of the Posterior Malleolus: A Biomechanical Study.

Objectives: The preferred method of fixation for posterior malleolus fractures remains controversial, and practices vary widely among surgeons. The purpose of this study was to compare anterior-to-posterior (AP) lag screws with posterior buttress plating for fixation of posterior malleolus fractures in a human cadaveric model.

Methods: Posterior malleolus fractures involving 30% of the distal tibial articular surface were created in 7 pairs of fresh frozen cadaveric ankles.