Reduction of Patella-baja and Pseudo-patella-baja Does Not Improve Range of Motion in Patients After Mega-TKA

Abstract

Background/aim: Patella baja (PB) and pseudo-patella baja (PPB) have been shown to negatively influence outcomes after total knee arthroplasty. We hypothesized that there is a high incidence of PB and PPB after megaprosthetic total knee arthroplasty (M-TKA), and that this is associated with reduced range of motion.

Patients and methods: We retrospectively analysed all patients in our Orthopaedic Trauma Department after distal femur or proximal tibia replacement. Preoperative and one-year postoperative follow-up included measurement of range of motion and detection of PB and PPB using radiological indices.

Results: We included 44 patients (age: 73±19 years). Preoperative PB detected by ISI could be reduced from 13 (36%) to 11 (25%) (p<0.01). Preoperative vs. postoperative ISI was 0.88±0.23 vs. 1.06±0.45 (p=0.03). PPB was observed preoperatively in 23 (63%) patients vs. 24 (54%) postoperatively. Preoperative vs. postoperative CDI was 0.70±0.24 vs. 0.95±0.43 (p=0.002). Preoperative flexion was 91°±30° vs. 85°±24° postoperatively (p>0.05).

Conclusion: Both PB and PPB are frequently observed after M-TKA. A reduction in PB and PPB alone does not improve postoperative range of motion.

Keywords: Revision total knee arthroplasty; outcome; patella baja; pseudo-patella baja.