title: Thermal damage during humeral reaming in total shoulder resurfacing.
abstract: BACKGROUND
  Total shoulder resurfacing (TSR) provides a reliable solution for the treatment of glenohumeral arthritis. It confers a number of advantages over traditional joint replacement with stemmed humeral components, in terms of bone preservation and improved joint kinematics. This study aimed to determine if humeral reaming instruments produce a thermal insult to subchondral bone during TSR.
  
  
  METHODS
  This was tested in vivo on 13 patients (8 with rheumatoid arthritis and 5 with osteoarthritis) with a single reaming system and in vitro with three different humeral reaming systems on saw bone models. Real-time infrared thermal video imaging was used to assess the temperatures generated.
  
  
  RESULTS
  Synthes (Epoca) instruments generated average temperatures of 40.7°C (SD 0.9°C) in the rheumatoid group and 56.5°C (SD 0.87°C) in the osteoarthritis group (P = 0.001). Irrigation with room temperature saline cooled the humeral head to 30°C (SD 1.2°C). Saw bone analysis generated temperatures of 58.2°C (SD 0.79°C) in the Synthes (Epoca) 59.9°C (SD 0.81°C) in Biomet (Copeland) and 58.4°C (SD 0.88°C) in the Depuy Conservative Anatomic Prosthesis (CAP) reamers (P = 0.12).
  
  
  CONCLUSIONS
  Humeral reaming with power driven instruments generates considerable temperatures both in vivo and in vitro. This paper demonstrates that a significant thermal effect beyond the 47°C threshold needed to induce osteonecrosis is observed with humeral reamers, with little variation seen between manufacturers. Irrigation with room temperature saline cools the reamed bone to physiological levels and should be performed regularly during this step in TSR.
authors.affiliation: Department of Trauma and Orthopaedics, Bristol Royal Infirmary, Upper Maudlin Street, Bristol, BS2 8HW, UK.
authors.forename: Philip A
authors.initials: PA
authors.lastname: McCann
authors.forename: Partha P
authors.initials: PP
authors.lastname: Sarangi
authors.forename: Richard P
authors.initials: RP
authors.lastname: Baker
authors.forename: Ashley W
authors.initials: AW
authors.lastname: Blom
authors.forename: Rouin
authors.initials: R
authors.lastname: Amirfeyz
keywords: Humeral reaming; thermal damage; total shoulder resurfacing