Abstract
Morbidly obese patients undergoing cemented primary total knee arthroplasty (TKA)
can pose a challenging problem with implant survivorship due to greater stress at
the cement-bone interface. With the advent of additive manufacturing (three-dimensional
printing), highly porous implants are now readily available. The purpose of this study
was to review the results of primary TKA in the morbidly obese (body mass index [BMI]
≥ 40) patient using a highly porous cementless tibial baseplate. This is a retrospective
study of 167 TKAs in patients with morbid obesity undergoing primary cementless TKA
with a minimum 5-year follow-up. A total of 6 patients died and 14 were lost to follow-up,
leaving 147 TKAs in 136 patients with a mean follow-up of 66 months (range 60–79 months).
The average age was 59 years (range 36–84 years) and average BMI was 45 kg/m2 (range 39.5–63.9). Clinical results, patient-reported outcome measures, radiographs,
and complications were reviewed. There were 9 failures requiring revision, including
3 for aseptic tibial loosening (2.0%), 2 for deep infection (1.4%), 2 for patellar
resurfacing (1.4%), 1 for patella instability (0.7%), and 1 for extensor mechanism
rupture (0.7%). Knee Society Score (KSS) improved from 48 to 90 at 2- and 5-year follow-up.
KSS function score improved from 49 to 68 and 79 at 2- and 5-year follow-up, respectively.
Survivorship with aseptic loosening as the endpoint was 98.0% at 5 years. Cementless
TKA using a highly porous tibial baseplate in morbidly obese patients demonstrated
excellent clinical results with 98% survivorship at 5 years and appears to offer durable
long-term biologic fixation as an alternative to mechanical cement fixation in this
challenging group of patients.
Keywords
primary TKA - cementless fixation - morbid obesity - aseptic loosening - survivorship
