title: Evaluation of thiol-modified hyaluronan and elastin-like polypeptide composite augmentation in early-stage disc degeneration: comparing 2 minimally invasive techniques.
abstract: METHODS
  An in vitro biomechanical and imaging study generated from an in vivo porcine model of early stage degenerative disc disease was used to evaluate mechanical property restoration, comparing 2 minimally invasive injection techniques.
  
  
  OBJECTIVE
  To evaluate the ability of an injectable hydrogel to restore the mechanical properties of spinal motion segments with early stage disc degeneration, comparing 2 minimally invasive injection techniques.
  
  
  BACKGROUND
  Treatment of early-stage disc degeneration may benefit from a combination of tissue engineering and minimally invasive therapeutic approaches. A recently developed hydrogel, thiol-modified hyaluronan elastin-like polypeptide (TMHA/EP) composite, has demonstrated potential as an injectable nucleus replacement.
  
  
  METHODS
  From a total of thirteen 35-kg Yorkshire boars, early-stage lumbar disc degeneration was introduced into 10 pigs via injection of chondroitinase ABC. After degeneration, 8 pigs received TMHA/EP augmentation; 1 disc via direct needle injection and a second using a modified kyphoplasty approach. High-resolution magnetic resonance images were acquired of the excised spinal motion segments, followed by biomechanical testing in axial compression, flexion-extension, lateral bending, and torsion.
  
  
  RESULTS
  The degenerate control motion segments were generally less stiff and more flexible than healthy controls. The injection of TMHA/EP into the degenerated nucleus produced similar mechanical stiffness to healthy controls. The direct-injected discs showed a dispersive pattern of TMHA/EP within the nucleus, whereas the modified kyphoplasty method yielded a bolus of hydrogel. Yet, mechanical behavior was comparable considering the 2 minimally invasive augmentation techniques.
  
  
  CONCLUSIONS
  The TMHA/EP composite can restore initial mechanical behavior in early-stage disc degeneration. Although both augmentation methods yielded mechanical properties comparable with healthy controls, direct injection represents a simpler technique, uses a smaller-gauge needle, does not introduce air into the disc, and yields a dispersive pattern that may be beneficial for future delivery of cells or growth factors.
authors: Orthopaedic Biomechanics Laboratory, Advanced Regenerative Tissue Engineering Centre, Sunnybrook Research Institute, Toronto, Ontario, Canada.
authors: Ashley E
authors: AE
authors: Leckie
authors: Margarete K
authors: MK
authors: Akens
authors: Kimberly A
authors: KA
authors: Woodhouse
authors: Albert J M
authors: AJ
authors: Yee
authors: Cari M
authors: CM
authors: Whyne
mesh_terms: D000818:Animals; D001696:Biomechanical Phenomena; D004195:Disease Models, Animal; D004549:Elastin / Q000737:chemistry; D006801:Humans; D006820:Hyaluronic Acid / Q000737:chemistry / Q000494:pharmacology*; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D007403:Intervertebral Disc / Q000187:drug effects / Q000503:physiopathology / Q000601:surgery; D055959:Intervertebral Disc Degeneration / Q000503:physiopathology / Q000628:therapy*; D008159:Lumbar Vertebrae / Q000187:drug effects / Q000503:physiopathology / Q000601:surgery; D019060:Minimally Invasive Surgical Procedures / Q000379:methods*; D010455:Peptides / Q000737:chemistry / Q000494:pharmacology*; D016059:Range of Motion, Articular; D013438:Sulfhydryl Compounds / Q000737:chemistry; D013552:Swine; D013997:Time Factors; D023822:Tissue Engineering / Q000379:methods; D059145:Total Disc Replacement / Q000379:methods; D016896:Treatment Outcome; D055675:Viscosupplements / Q000494:pharmacology
chemical_list: D010455:Peptides; D013438:Sulfhydryl Compounds; D055675:Viscosupplements; D020136:Hydrogel, Polyethylene Glycol Dimethacrylate; D006820:Hyaluronic Acid; D004549:Elastin