ABSTRACT
BACKGROUND: The sacro-femoral-pubic (SFP) parameter, calculated using the SFP angle measured on a frontal pelvis radiograph, has previously been shown to have a strong correlation with sagittal pelvic tilt (PT) measured on a lateral x-ray. The purpose of this study is to assess the validity, interobserver reliability and intraobserver reproducibility of the SFP parameter in predicting the sagittal PT. METHODS: This is a retrospective study of 100 patients with frontal and lateral radiographs of the pelvis. Two observers independently measured the SFP angle on frontal x-ray (midpoint of S1 end plate to centroid of acetabula to upper midpoint of the pubic symphysis) and PT on lateral x-ray (midpoint of sacral plate to the centroid of acetabula to vertical plane). The SFP parameter was defined using the equation: SFP parameter = 75 - SFP angle. The interobserver reliability and intraobserver reproducibility were calculated using interclass correlation coefficient (ICC). Validity of the SFP parameter was calculated using Pearson correlation coefficient. RESULTS: The intraobserver reproducibility of the SFP parameter was excellent (ICC >0.90) for both observers. The interobserver reliability of all measurements was substantial for the SFP parameter (ICC >0.80) and PT (ICC >0.70). The concurrent validity of the SFP parameter was substantial (r = 0.70). CONCLUSION: Calculating PT from a frontal radiograph using the equation for the SFP parameter is a valid, reliable, and reproducible formula that may be used to predict sagittal PT.
Subject(s)
Arthroplasty, Replacement, Hip , Femur/diagnostic imaging , Pelvis/diagnostic imaging , Pubic Bone/diagnostic imaging , Sacrum/diagnostic imaging , Acetabulum , Adolescent , Adult , Aged , Aged, 80 and over , Bone Plates , Female , Humans , Male , Middle Aged , Observer Variation , Radiography , Reproducibility of Results , Retrospective Studies , X-Rays , Young AdultABSTRACT
As a primary malignant bone tumor, osteosarcoma is second only to chondrosarcoma. Although it commonly metastasizes and is aggressive in nature, it rarely colonizes the skin. This is a report of a 22-year-old male with osteosarcoma of the pelvis and metastasis to the lungs and chest wall who developed a clinically unsuspected solitary cutaneous metastasis in the scalp. Instead of the expected cyst, incisional biopsy disclosed a solid tan nodule of chondro-osseous sarcoma. Although rare, cutaneous metastases from osteosarcoma may appear in skin, especially the scalp, or in skin over the primary tumor. New skin lesions in a patient with a history of osteosarcoma warrant investigations including imaging and biopsy.
