title: Tibial Tray Thickness Significantly Increases Medial Tibial Bone Resorption in Cobalt-Chromium Total Knee Arthroplasty Implants.
abstract: Stress shielding is an uncommon complication associated with primary total knee arthroplasty. Patients are frequently identified radiographically with minimal clinical symptoms. Very few studies have evaluated risk factors for postoperative medial tibial bone loss. We hypothesized that thicker cobalt-chromium tibial trays are associated with increased bone loss.
  
  
  
  We performed a retrospective review of 100 posterior stabilized, fixed-bearing total knee arthroplasty where 50 patients had a 4-mm-thick tibial tray (thick tray cohort) and 50 patients had a 2.7-mm-thick tibial tray (thin tray cohort). A clinical evaluation and a radiographic assessment of medial tibial bone loss were performed on both cohorts at a minimum of 2 years postoperatively.
  
  
  
  Mean medial tibial bone loss was significantly higher in the thick tray cohort (1.07 vs 0.16 mm; P = .0001). In addition, there were significantly more patients with medial tibial bone loss in the thick tray group compared with the thin tray group (44% vs 10%, P = .0002). Despite these differences, there were no statistically significant differences in range of motion, knee society score, complications, or revision surgeries performed.
  
  
  
  A thicker cobalt-chromium tray was associated with significantly more medial tibial bone loss. Despite these radiographic findings, we found no discernable differences in clinical outcomes in our patient cohort. Further study and longer follow-up are needed to understand the effects and clinical significance of medial tibial bone loss.
authors.affiliation: Department of Orthopaedic Surgery, Colorado Joint Replacement, Denver, Colorado.
authors.forename: J Ryan
authors.initials: JR
authors.lastname: Martin
authors.affiliation: Department of Orthopaedic Surgery, OrthoCarolina, Charlotte, North Carolina.
authors.forename: Chad D
authors.initials: CD
authors.lastname: Watts
authors.affiliation: Department of Orthopaedic Surgery, Colorado Joint Replacement, Denver, Colorado.
authors.forename: Daniel L
authors.initials: DL
authors.lastname: Levy
authors.affiliation: Department of Orthopaedic Surgery, Colorado Joint Replacement, Denver, Colorado.
authors.forename: Todd M
authors.initials: TM
authors.lastname: Miner
authors.affiliation: Department of Orthopaedic Surgery, OrthoCarolina, Charlotte, North Carolina.
authors.forename: Bryan D
authors.initials: BD
authors.lastname: Springer
authors.affiliation: Department of Orthopaedic Surgery, Colorado Joint Replacement, Denver, Colorado; Department of Mechanical and Materials Engineering, University of Denver, Denver, Colorado; Department of Orthopedic Surgery, Joan C. Edwards School of Medicine, Marshall University, Huntington, West Virginia.
authors.forename: Raymond H
authors.initials: RH
authors.lastname: Kim
mesh_terms: D000328:Adult; D000368:Aged; D019645:Arthroplasty, Replacement, Knee / Q000009:adverse effects / Q000379:methods*; D001862:Bone Resorption / Q000601:surgery; D002857:Chromium / Q000737:chemistry*; D003035:Cobalt / Q000737:chemistry*; D005260:Female; D006801:Humans; D007719:Knee Joint / Q000601:surgery*; D007720:Knee Prosthesis; D008297:Male; D008875:Middle Aged; D019736:Prostheses and Implants; D016059:Range of Motion, Articular; D012086:Reoperation; D012189:Retrospective Studies; D012307:Risk Factors; D013977:Tibia / Q000601:surgery*
chemical_list: D002857:Chromium; D003035:Cobalt
keywords: bone resorption; cobalt–chromium; stress shielding; tibial base plate; total knee arthroplasty