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Published on: February 27, 2018
Three-dimensional Volumetric Filling Ratio Predicts Stress Shielding in Short-stem Anatomic Total Shoulder
Haluk Celik1, Aakash Chauhan, Cesar Flores-Hernandez
1From the Shiley Center for Orthopaedic Research and Education (SCORE) at Scripps Clinic (Dr. Celik, Dr. Chauhan, Mr. Flores-Hernandez, Dr. D'Lima, and Dr. Hoenecke), and the Division of Sports Medicine (Dr. Celik, Dr. Chauhan, and Dr. Hoenecke), Department of Orthopaedic Surgery, Scripps Clinic, La Jolla, CA.
Introduction:
Three-dimensional (3-D) CT volumetric filling ratio (VFR) is a better predictor of proximal humerus stress shielding after short-stem anatomic total shoulder arthroplasty (aTSA) than using plain radiographs.
Methods:
Forty-four patients with short-stem aTSAs, preoperative CT scans, and a minimum 3-year radiographic follow-up were included. Patients were divided into group A (stress shielding) and group B (no stress shielding) based on the radiographic analysis. Standard implant filling ratios were measured on plain radiographs. The 3-D VFR of the metaphyseal and diaphyseal segments of the aTSA stem was measured using MIMICS (Materialise). The area under a receiver operator characteristic curve was used to determine the predictive strength of the 3-D VFR method.
Results:
The average age and radiographic follow-up was 69 years and 44 months. Group A had 19 patients and statistically higher filling ratios using 3-D VFR method than group B, whereas no notable differences were found between the groups using standard techniques. The 3-D VFR had an area under a receiver operator characteristic curve of 92%, which supports it as a good predictor of stress shielding.
Conclusions:
These methods enable early identification of patients at risk for stress shielding and can also be valuable in improving humeral stem designs.
Level Of Evidence:
Level III. Case-control study.
