Stiffness after primary total knee arthroplasty: a radiographic analysis with a matched-control population

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Background:The purposes of this study were (1) to evaluate standardized radiographic parameters in a population of patients who developed stiffness after primary total knee arthroplasty (TKA), and (2) to compare those to a matched control population.Methods:A retrospective review was performed to identify patients who required revision for stiffness after primary TKA. Patients with history of TKA revision or infection, as well as, those treated with isolated polyethylene exchange were excluded. Study patients were matched 1:1 with controls based on age, sex, body mass index (BMI). Radiographic measurements were performed by two blinded independent observers.Results:A total of 44 patients met the inclusion criteria. Thirty-one (70%) were females. Mean BMI was 33 kg/m2 (19-58). Univariate odds ratios showed significance for patella baja (5.776; 0.025), increased anterior condylar offset ratio (ACO) (15.265; 0.000), increased anterior implant-cortex gap (5.067; 0.038), and increased percentage of patellar displacement (PPD) (6.476; 0.016). Multivariate regression analysis showed significance for ACO (18.307; 0.001) and PPD (9.338; 0.024). No significance was observed with respect to component alignment in the coronal or sagittal planes, posterior condylar offset ratio, patellar tilt, presence of heterotopic ossification, or posterior osteophyte formation. Intraclass correlation coefficients (ICCs) ranged from good to excellent (>0.8) for all measurements performed.Conclusions:The restoration of the joint line and avoiding overstuffing the patellofemoral compartment are fundamental in preventing the development of postoperative stiffness. Poor mechanics of the patellofemoral compartment are significantly associated with the development of stiffness after primary TKA.

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