Applying the Deltoid Tuberosity Index (DTI) to assess the risk of screw cut-out. A retrospective analysis of 306 proximal humerus fractures treated with PHILOS Plate.

Abstract

Background. Reconstruction of the proximal humerus with a locking plate is often the first approach for proximal humerus fractures. Screw cut-out is the most common complication and is especially relevant in osteoporotic bone of the elderly population. The Deltoid Tuberosity Index (DTI) has recently been proposed as an indirect measure to assess osteopenia and failure rate before surgery, which may provide important information for surgical planning. Though simple and assessable, the DTI lacks scientific evidence to back its broad clinical usage. This study gives the first independent, large-sample retrospective analysis of the correlation between the local bone density, indirectly measured through the DTI, and screw cut-out.Methods. 306 cases of proximal humerus fractures treated with PHILOS plate were retrospectively analyzed. The DTI was measured in AP x-rays. The primary endpoint was screw cut-out defined as the intra-articular position of at least one screw associated to a reduction loss after surgery.Results. The mean clinical follow up was 467 days. The DTI varied from 1.10 to 2.28 (average: 1.42). Screw cut-out occurred on average in 8% of the cases and did correlate positively with a DTI ≤ 1.44 (p = 0.003). However, the rate of cut-out and correlation to DTI varied widely according to age group: within the age of 65-80 years a DTI ≤ 1.44 increased the cut-out rate from 0% to 17% (p = 0.02); on the other hand, in younger ages (< 65 years) the DTI did not correlate to cut-out and in the oldest group (> 80 years) cut-out rates were high (17-20%) independently of the DTI. Age and medial hinge displacement also correlated to cut-out. This was not the case for gender, fracture pattern and quality of surgical reduction.Conclusions. We confirm the correlation between a DTI ≤ 1.44 and screw cut-out. This correlation alone however may be too simplistic and not relevant in all age spectrum. High risk groups for screw cut-out are patients older than 65 years with a DTI ≤ 1.44 or any patient older than 80 years. Applying the DTI in the age group of 65 to 80 years offers relevant information for surgical planning in the trauma setting through a tool that is fast, cheap, and easy to perform. Level of Evidence: Level 3, Retrospective Cohort Study.