Patellar Cut and Composite Thickness: The Influence on Postoperative Motion and Complications in Total Knee Arthroplasty

J Arthroplasty. 2017 Jun;32(6):1803-1807. doi: 10.1016/j.arth.2016.12.033. Epub 2016 Dec 27.


Background: Little data exist on the influence of patellar thickness on postoperative motion or complications after total knee arthroplasty (TKA). This study addresses the following questions: Is postoperative motion influenced by change in composite patellar thickness? Is change in patellar thickness associated with more complications? And do more complications occur in the knees with a patellar bone remnant (<12 mm) and a native patellar thickness <18 mm?

Methods: In total, 3655 TKAs were performed by 3 surgeons over a 28-year interval. All knees had caliper measurement of patellar thickness before the patellar cut, after implantation of the component and postoperative motion recorded in the database 1 or 2 years after TKA.

Results: Patellar composite thickness was the same (1034 knees), thicker (1617 knees), and thinner (1004 knees). A significant but weak relationship was identified between the change in patellar thickness and motion (P < .01, ρ = -0.046); an increase in "composite patellar thickness" of 10 mm would result in a 3° loss of knee motion. Significant differences were identified between change in thickness and manipulations (P < .05), ruptures (P = .01), and patellar clunk/crepitus (P < .01). Examining knees with bone remnant thicknesses (<12 mm/≥12 mm), there was no difference in fractures (P = .26). No extensor ruptures occurred in knees with remnant thickness <12 mm. Comparing knees with native bone thickness (≤18 mm/>18 mm), significant differences were found in fractures (P < .01) and patellar radiolucencies (P = .01).

Conclusion: As this data does not demonstrate a strong tendency toward losing motion when the patellar thickness is increased, the authors recommend avoiding compromise of the patellar bone stock and tendon insertion. When native patellar bone is thin (<18 mm), we recommend maintaining 12 mm of patellar bone stock and accept the increase in composite thickness.

Keywords: complications; knee arthroplasty; motion; patellar composite thickness; patellar thickness.

MeSH terms

  • Aged
  • Arthroplasty, Replacement, Knee / adverse effects
  • Arthroplasty, Replacement, Knee / statistics & numerical data*
  • Female
  • Fractures, Bone / etiology
  • Humans
  • Knee / surgery
  • Knee Joint / physiology*
  • Knee Joint / surgery
  • Knee Prosthesis
  • Male
  • Middle Aged
  • Motion
  • Patella / anatomy & histology
  • Patella / physiology
  • Patella / surgery*
  • Postoperative Complications / etiology*
  • Postoperative Period
  • Range of Motion, Articular