title: Shoulder proprioception - lessons we learned from idiopathic frozen shoulder.
abstract: BACKGROUND
  Of all the most frequent soft tissue disorders of the shoulder, idiopathic frozen shoulder (IFS) offers the greatest potential for studying proprioception. Studies concerning the presence of proprioception dysfunctions have failed to determine the potential for spontaneous healing of passive shoulder stabilizers (anterior and posterior capsule, middle and inferior gleno-humeral ligaments), its relationship with passive (PJPS) and active (AJPS) shoulder proprioception for internal and external rotation (IR, ER), as well as the isokinetic muscle performance of the internal and external rotators. This study investigates these dependencies in the case of arthroscopic release of IFS.
  
  
  METHODS
  The study group comprised 23 patients (average aged 54.2) who underwent arthroscopic release due to IFS and 20 healthy volunteers. The average follow-up time was 29.2 months. The Biodex system was used for proprioception measurement in a modified neutral arm position and isokinetic evaluation. The results were analysed using the T-test, Wilcoxon and interclass correlation coefficient. P-values lower than 0.05 were considered significant.
  
  
  RESULTS
  Statistically significant differences were found between involved (I) and uninvolved (U) shoulders only in the cases of PJPS and AJPS, peak torque, time to peak torque and acceleration time for ER (p < 0.05). No statistically significant difference was noted between PJPS IR and PJPS ER or between AJPS IR and AJPS ER (p > 0.05) for the U shoulders.
  
  
  CONCLUSIONS
  The anatomical structure of anterior (capsule, middle and anterior band of inferior gleno-humeral ligament) and posterior (capsule and posterior band of inferior gleno-humeral ligament) passive shoulder restraints has no impact on the difference in PJPS values between ER and IR in a modified neutral shoulder position. The potential for spontaneous healing of the anterior and posterior passive shoulder restraints influences PJPS recovery after arthroscopic release of IFS. ER peak torque deficits negatively affect AJPS values. PJPS and AJPS of ER and IR can be measured with a high level of reproducibility using an isokinetic dynamometer with the arm in a modified neutral shoulder position. Differences greater than 15 % for PJPS and >24 % for AJPS for ER and IR can be helpful for future studies as baseline data for identification of particular passive and active shoulder stabilizers at risk.
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland. fabis@onet.eu.
authors.forename: Jaroslaw
authors.identifier: http://orcid.org/0000-0002-2148-3780
authors.initials: J
authors.lastname: Fabis
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Remigiusz
authors.initials: R
authors.lastname: Rzepka
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Anna
authors.initials: A
authors.lastname: Fabis
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Jacek
authors.initials: J
authors.lastname: Zwierzchowski
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Grzegorz
authors.initials: G
authors.lastname: Kubiak
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Arkadiusz
authors.initials: A
authors.lastname: Stanula
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Michal
authors.initials: M
authors.lastname: Polguj
authors.affiliation: Department of Arthroscopy Minimally Invasive Surgery and Sport Traumatology, Medical University of Lodz and FMC Medical Centre Lodz, Lodz, Poland.
authors.forename: Radek
authors.initials: R
authors.lastname: Maciej
mesh_terms: D000328:Adult; D000368:Aged; D001182:Arthroscopy; D001696:Biomechanical Phenomena; D002062:Bursitis / Q000175:diagnosis / Q000503:physiopathology* / Q000601:surgery; D016022:Case-Control Studies; D005260:Female; D006801:Humans; D008297:Male; D008875:Middle Aged; D053580:Muscle Strength; D053581:Muscle Strength Dynamometer; D011434:Proprioception; D016059:Range of Motion, Articular; D020127:Recovery of Function; D012785:Shoulder Joint / Q000294:innervation* / Q000601:surgery; D019415:Torque; D016896:Treatment Outcome
keywords: Frozen shoulder; Isokinetics; Passive stabilizers; Proprioception