Characteristics and Limitations of FDG PET/CT for Imaging of Squamous Cell Carcinoma of the Head and Neck: A Comprehensive Review of Anatomy, Metastatic Pathways, and Image Findings.

OBJECTIVE: This image-based article illustrates the anatomic regions of squamous cell carcinomas of the head and neck and describes the metastatic pathways in and TNM staging for each region. Both the role and limitations of FDG PET/CT in imaging such cancers are discussed, and cases exemplifying these issues are reported. Also included is a discussion of the use of FDG PET/CT to monitor the response of squamous cell carcinomas of the head and neck to therapy, in addition to a brief comparison of PET/CT with such traditional imaging modalities as CT, MRI, and ultrasound. CONCLUSION: Understanding the characteristics of squamous cell carcinoma of the head and neck, as imaged by FDG PET/CT, is crucial for determining treatment strategy, because it helps to avoid incorrect staging and also provides an accurate assessment of treatment response.

The effects of external torque on polyethylene tibial insert damage patterns.

The forces and torques that occur during walking gait, particularly during toe-off, promote articulation in the posteromedial quadrant of tibial inserts. Retrieved components of failed knee arthroplasties show ultrahigh molecular weight polyethylene damage patterns in this region. Component-designed constraint, compromised polymer, and surgical factors account for these observations. The current authors compare the contact stresses that developed on four implant designs during toe-off for optimally aligned and externally torqued components using the finite element method. Under 16 N-m of torque, the four designs studied varied regarding their centers of rotation and magnitude of external rotation, which are related directly to their specific articulating surface geometry. Designs with conforming condylar geometry had greater rotational constraint and therefore, less external rotation. These conforming designs offer the benefits of lower stresses and tend to limit contact near the edge of the plateau. However, because of their increased rotational constraint, torque is transmitted more readily to the implant-bone interface, increasing the potential for implant loosening. The data presented serve as an indicator of the potential for polyethylene tibial component surface damage and define the role that implant geometry plays in resisting external rotation.