Patellofemoral Morphology and Imaging Features of Patellar Tumors and Tumor-Like Lesions

Background: The patellofemoral joint parameters and imaging presentations of patellar tumors and tumor-like lesions are not clear. Objectives: The aim of this case-control study was to investigate patellofemoral joint parameters, clinical data and findings in patients with patellar tumors and tumor-like lesions. Patients and Methods: Twenty-nine patients with patellar diseases were enrolled. Morphological measurement was performed and analyzed in fourteen patients with patellar tumors (tumor group) and another fifteen patients without patellar diseases (control) who had complete computed tomography data as the control group. Results: Among 29 patients, there were twenty benign lesions (69.0%) and nine malignant tumors (31.0%). Benign lesions included chondroblastoma in nine patients (31.0%), giant cell tumor of bone in four (13.8%), chondroma in one (3.4%), hemangioma in one (3.4%), parosteal lipoma in one (3.4%), bone cyst in two (6.8%), aneurysmal bone cyst in one (3.4%), and fibrous dysplasia in one (3.4%). Malignant tumors were bone metastasis in four patients (13.8%), osteosarcoma in three (10.3%) including common osteosarcoma in two and well-differentiated osteosarcoma in the remaining one, chondrosarcoma in one (3.4%) and hemangiopericytoma in one (3.4%) patient. Chondroblastomas, giant cell tumors and fibrous dysplasia showed findings of expansile bone destruction lesions in imaging. Malignant tumors had bone destruction with ill-defined margins. The femoral trochlear angle was significantly greater in the tumor than the control group (P < 0.001, 159.19o ± 9.42o vs. 135.00o ± 5.50o), whereas the lateral pulley inclination (P = 0.01, 14.69o ± 8.91o vs. 20.73o ± 3.51o) and trochlear depth (P < 0.001, 3.10 ± 1.79 vs. 6.67 ± 1.26 mm) were significantly smaller in the tumor than the control group. Conclusion: The patellar tumors are mainly benign and rarely malignant. Comprehensive understanding of the distribution, incidence and imaging features of patellar tumors and patellofemoral morphological parameters can improve the diagnosis accuracy.