title: Procollagen markers in microdialysate can predict patient outcome after Achilles tendon rupture.
abstract: OBJECTIVE
  Patients who sustain acute Achilles tendon rupture (ATR) exhibit variable and mostly impaired long-term functional, and patient-reported outcomes. However, there exists a lack of early predictive markers of long-term outcomes to facilitate the development of improved treatment methods. The aim of this study was to assess markers of tendon callus production in patients with ATR in terms of outcome, pain, and fatigue.
  
  
  METHODS
  Prospective cohort study; level of evidence 2. Outpatient orthopaedic/sports medicine department.
  
  
  METHODS
  A total of 65 patients (57 men, 8 women; mean age 41±7 years) with ATR were prospectively assessed.
  
  
  METHODS
  Markers of tendon callus production, procollagen type I N-terminal propeptide (PINP) and procollagen type III N-terminal propeptide (PIIINP), were assessed 2 weeks postoperatively using microdialysis followed by enzymatic quantification. Normalised procollagen levels (n-PINP and n-PIIINP) were calculated as the ratio of procollagen to total protein content. Pain and fatigue were assessed at 1 year using reliable questionnaires Achilles tendon Total Rupture Score (ATRS).
  
  
  RESULTS
  Patients exhibited fatigue (77.6%) and pain (44.1%) to some extent. Higher levels of n-PINP (R=0.38, p=0.016) and n-PIIINP (R=0.33, p=0.046) were significantly associated with less pain in the limb. Increased concentrations of PINP (R=-0.47, p=0.002) and PIIINP (R=-0.37, p=0.024) were related to more self-reported fatigue in the leg. The results were corroborated by multiple linear regression analyses.
  
  
  CONCLUSIONS
  Assessment of procollagen markers in early tendon healing can predict long-term patient-reported outcomes after ATR. These novel findings suggest that procollagen markers could be used to facilitate the development of improved treatment methods in patients who sustain ATR.
  
  
  BACKGROUND
  NCT01317160: Results. NCT02318472: Pre-results.
authors.affiliation: Integrative Orthopedic Laboratory, Department of Molecular Medicine and Surgery , Karolinska Institutet , Stockholm , Sweden.
authors.forename: Md Abdul
authors.initials: MA
authors.lastname: Alim
authors.affiliation: Integrative Orthopedic Laboratory, Department of Molecular Medicine and Surgery , Karolinska Institutet , Stockholm , Sweden.
authors.forename: Simon
authors.initials: S
authors.lastname: Svedman
authors.affiliation: Department of Psychiatry , Tiohundra AB , Norrtälje , Sweden.
authors.forename: Gunnar
authors.initials: G
authors.lastname: Edman
authors.affiliation: Integrative Orthopedic Laboratory, Department of Molecular Medicine and Surgery, Karolinska Institutet, Stockholm, Sweden; Department of Orthopedics, Karolinska University Hospital, Stockholm, Sweden.
authors.forename: Paul W
authors.identifier: 0000-0002-5520-169X
authors.initials: PW
authors.lastname: Ackermann
keywords: Achilles; Chronic; Collagen; Injuries; Tendon