title: Innervation patterns of thumb trapeziometacarpal joint ligaments.
abstract: OBJECTIVE
  The human thumb trapeziometacarpal (TM) joint is a unique articulation that allows stability during pinch and grip and great degrees of mobility. Because the saddle-shaped articulating surfaces of the TM joint are inherently unstable, joint congruity depends on the action of restraining ligaments and periarticular muscles. From other joints, it is known that proprioceptive and neuromuscular joint stability depend on afferent information from nerve endings within ligaments. We hypothesize that the TM joint ligaments may similarly be innervated, indicating a possible proprioceptive function of the joint.
  
  
  METHODS
  We harvested 5 TM joint ligaments in entirety from 10 fresh-frozen cadaver hands with no or only minor signs of osteoarthritis and suture-marked them for proximal-distal orientation. The ligaments harvested were the dorsal radial, dorsal central, posterior oblique, ulnar collateral, and anterior oblique ligaments. After paraffin-sectioning, we stained the ligaments using a triple-antibody immunofluorescent technique and analyzed them using immunofluorescence microscopy.
  
  
  RESULTS
  Using the triple-stain technique, mechanoreceptors could be classified as Pacinian corpuscles, Ruffini endings, or Golgi-like endings. The 3 dorsal ligaments had significantly more nerve endings than the 2 volar ligaments. Most of the nerve endings were close to the bony attachments and significantly closer (P = .010) to the metacarpal insertion of each ligament. The anterior oblique ligament had little to no innervation in any of the specimens analyzed.
  
  
  CONCLUSIONS
  The TM joint ligaments had an abundance of nerve endings in the dorsal ligaments but little to no innervation in the anterior oblique ligament. The Ruffini ending was the predominant mechanoreceptor type, with a greater density in the mobile metacarpal portion of each ligament.
  
  
  CONCLUSIONS
  Presence of mechanoreceptors in the dorsal TM joint ligaments infers a proprioceptive function of these ligaments in addition to their biomechanical importance in TM joint stability.
authors.affiliation: Department of Clinical Science and Education, Karolinska Institutet, Stockholm, Sweden. elisabet.hagert@ki.se
authors.forename: Elisabet
authors.initials: E
authors.lastname: Hagert
authors.forename: Julia
authors.initials: J
authors.lastname: Lee
authors.forename: Amy L
authors.initials: AL
authors.lastname: Ladd
mesh_terms: D005260:Female; D005384:Finger Joint / Q000294:innervation / Q000502:physiology*; D006801:Humans; D007150:Immunohistochemistry; D008023:Ligaments, Articular / Q000294:innervation* / Q000378:metabolism; D008297:Male; D008465:Mechanoreceptors / Q000378:metabolism* / Q000502:physiology; D010141:Pacinian Corpuscles / Q000378:metabolism; D011434:Proprioception / Q000502:physiology*; D013933:Thumb / Q000294:innervation / Q000502:physiology*