title: Muscle hypoxia in rheumatoid hands: does it play a role in ulnar drift?
abstract: OBJECTIVE
  The cause of ulnar drift in patients with rheumatoid arthritis (RA) is unknown. It may occur because of external forces applied to the fingers during normal use. Alternatively, it may arise after changes in the internal forces on the anatomy of the digits owing to alterations in the supporting structures of the joints or their control mechanisms, or both. Intrinsic muscle tightness, which is commonly seen in RA hands, may be the result of adaptive shortening or a direct consequence of RA. Previous studies carried out by our group have shown that joints, tendons, and associated synovium in RA hands are consistently hypoxic. Therefore, we formed the hypothesis that there is a difference in hand/forearm muscle oxygen tension in RA versus non-RA.
  
  
  METHODS
  We measured tissue oxygen levels in the intrinsic muscles of the hands and forearm muscles of 29 patients with a diagnosis of RA, who were undergoing elective surgery. We measured oxygen levels using a microelectrode technique. A total of 31 patients without RA undergoing elective surgery served as matched controls.
  
  
  RESULTS
  Our results show that the intrinsic muscles of RA patients are significantly more hypoxic than in non-RA controls. Moreover, there is a trend in the RA group for increasing hypoxia in a radial-to-ulnar direction when comparing the different intrinsic muscle groups. We also demonstrate that forearm and thenar and hypothenar muscles are significantly more hypoxic in RA versus non-RA patients.
  
  
  CONCLUSIONS
  The intrinsic muscle weakness, intrinsic tightness, and muscle wasting observed in RA may not be due to disuse atrophy resulting from joint disease. From our data, we speculate that these changes may be the result of direct muscular involvement in RA leading to muscle hypoxia.
authors.affiliation: Kennedy Institute of Rheumatology Imperial College, London, UK. mo@akhavani.com
authors.forename: Mohammed A
authors.initials: MA
authors.lastname: Akhavani
authors.forename: Ewa M
authors.initials: EM
authors.lastname: Paleolog
authors.forename: Norbert
authors.initials: N
authors.lastname: Kang
mesh_terms: D000328:Adult; D000368:Aged; D000704:Analysis of Variance; D018501:Antirheumatic Agents; D001172:Arthritis, Rheumatoid / Q000150:complications* / Q000175:diagnosis / Q000188:drug therapy; D016022:Case-Control Studies; D017558:Elective Surgical Procedures / Q000379:methods; D005260:Female; D006227:Hand Deformities, Acquired / Q000175:diagnosis* / Q000209:etiology / Q000601:surgery; D006801:Humans; D000860:Hypoxia / Q000209:etiology / Q000503:physiopathology*; D008297:Male; D008875:Middle Aged; D018482:Muscle, Skeletal / Q000098:blood supply / Q000503:physiopathology*; D010100:Oxygen / Q000378:metabolism*; D010101:Oxygen Consumption / Q000502:physiology; D011859:Radiography; D012016:Reference Values; D012720:Severity of Illness Index; D018709:Statistics, Nonparametric; D014457:Ulna / Q000000981:diagnostic imaging / Q000503:physiopathology
chemical_list: D018501:Antirheumatic Agents; D010100:Oxygen