Background: Patella baja is a potentially disabling and difficult-to-treat complication following total knee arthroplasty (TKA). We investigated whether complete or partial excision of the fat pad has an effect on the length of the patellar tendon following TKA.
Methods: A retrospective review of patient radiographs was performed. One hundred and eleven consecutive patients who underwent primary TKA for osteoarthritis using the same components by two consultants were selected. Seventy-two patients underwent complete excision of the fat pad, whilst 39 had partial excision as per consultant practice. Patellar height was measured using the Caton-Deschamps Index (CDI) on immediate postoperative radiographs and at a minimum follow-up of 1 year.
Results: In the complete excision group, the mean CDI changed from 0.54 immediately postoperatively to 0.45 at a minimum follow-up of 1 year (p < 0.0001) indicating shortening of the patellar tendon, and eight patients reported anterior knee pain. The partial excision group's mean CDI changed from 0.76 to 0.75 (p = 0.231). An analysis of variance showed that the effect of complete fat pad excision on patella tendon length was significant, F(1, 109) = 15.273, p < 0.001.
Conclusion: At a minimum follow-up of 1 year, the patellar tendon length shortened significantly in the group of patients with complete fat pad excision. With partial excision, there was no significant change in tendon length. Complete excision of the fat pad should therefore be avoided wherever possible in an attempt to avoid patella baja.
Level of evidence: II.
Keywords: Infrapatellar fat pad; Knee arthroplasty; Patella baja; Patellar tendon shortening.