Decreased Patellar Fractures and Subluxation With Patellar Component Replacement at Stage-One Spacer.

BACKGROUND

Periprosthetic joint infection is a devastating complication of total knee arthroplasty and is often treated with 2-stage revision. We retrospectively assessed whether replacing the patellar component with articulating stage-one spacers was associated with improved outcomes compared to spacers without patellar component replacement.

METHODS

A total of 139 patients from a single academic institution were identified who underwent an articulating stage-one revision total knee arthroplasty and had at least 1-year follow-up. Of the 139 patients, 91 underwent patellar component removal without replacement, while 48 had a patellar component replaced at stage-one revision. Patellar fracture and reinfection at any point after stage-one were recorded. Knee range of motion (ROM), patellar thickness, lateral tilt, and lateral displacement were measured at 6-weeks post stage-one. Chi-square, Fisher's exact, and t-tests were utilized for comparisons. There were no significant demographic differences between groups.

RESULTS

Patellar component replacement at stage-one revision was associated with fewer patellar fractures (2.1 versus 12.1%, P = .046), less lateral patellar displacement (1.7 versus 16.0 mm, P < .01), and improved pre to postoperative knee ROM 6 weeks after stage-one (+5.9 versus -11.4°, P = .03). There was no difference in reinfections after stage-2 revision for the replaced or unreplaced patellar groups (15.4 versus 15%, P = 1.000). While the mean time between stage-one and stage-2 was not different (5.2 versus 4.5 months, P = .50), at one-year follow-up, significantly more patients in the patellar component replacement group were satisfied and refused stage-2 revision (45.8 versus 3.3%, P < .001).

CONCLUSIONS

Replacing the patellar component at stage-one revision is associated with a decreased rate of patellar fracture and lateral patellar subluxation, improved ROM, and possible increased patient satisfaction, as reflected by nearly half of these patients electing to keep their spacer. There was no difference in reinfection rates between the cohorts.