2025 ISAKOS Congress in Munich, Germany

2025 ISAKOS Biennial Congress Paper


Impact of Patient Height on Proximal Radial Shaft Morphology

Michael Cobo, BS, Nashville, TN UNITED STATES
Johannes M. Sieberer, MSc, New Haven UNITED STATES
Albert L Rancu, BS, New Haven, CT UNITED STATES
Steven Tommasini, PhD, New Haven, Connecticut UNITED STATES
Daniel Wiznia, MD
Lisa L Lattanza, MD, New Haven, CT UNITED STATES

Yale University, New Haven, CT, UNITED STATES

FDA Status Not Applicable

Summary

The morphology of the proximal radius is important for selecting implant stems in radial head fractures and varies significantly due to patient height.

Abstract

Introduction

Treatment for a radial head fracture may involve an implant stem within the intramedullary canal (IC). The width and length of the implant should be chosen to best fit the morphology of the IC. If an implant is placed that does not achieve appropriate mechanical fixation, aseptic loosening may occur, requiring revision surgery. Surgeries involving the radial head have a high revision rate, 7.3%-13.6% with 30% of these resulting from aseptic loosening or insufficient mechanical fit. Previous studies identified significant variations of the proximal radial shaft morphology, indicating that a small set of standard implants might not be sufficient to cover the full spectrum of morphologies, but only analyzed averaged size females and males or did not report patient height, therefore not capture the total variance in population. This study aims to analyze and report the morphological variance physicians encounter when treating these fractures.

Methods

Three-dimensional (3D) PR and corresponding IC models were selected from high-resolution CT scan sources from the New Mexico Decedent Image database. These 3D-models were chosen based on the criteria of sex, male or female, and height, in four groups (short female (height <157.5cm), average female (160-165cm), average men (173-178cm). and tall men (>182.5cm). Ages ranged from 25-60years. The radial 3D-models were algorithmically analyzed for every 0.1mm slice for 60mm along their longitudinal axis starting from the proximal onset of the radial neck. Each slice measurement consisted of fitting an ellipsis around the outside of the cortical bone and the IC and recording the parameters of the ellipses (i.e., minor and major axis, eccentricity, midpoint, and fitting error). The data was used to characterize the mean, variance, and range of ten relevant PR landmarks, such as width of the IC and the cortical bone, distance from the radial head to the radial neck, and the bicipital tuberosity. Statistical tests (i.e., Mann-Whitney-U test, Welch-test, Student’s-test) were used to analyze intra sex differences. Intra-sex demographics were compared using Fisher’s-exact-tests. Significance was assumed at 0.05. A priori power calculation for a minimum sample size with a power level of 0.8 was conducted to detect relevant differences.

Results

One hundred fifty-one proximal radial shafts were analyzed. The demographics were: 30 short women (height:154.5±3.3cm, age:30.1±4.0 years, weight:75.8±28.6kg), 45 average women (162.1±1.8cm, 44.2±14.6years, 75.7±19.7kg), 45 average men (175.5±2.0cm,44.1±14.1years, 85.2±16.20kg), and 31 tall men (189.5±5.7cm, 45.9±12.1years, 101±23.4 kg). Landmarks were characterized for all radii. Several significant differences were found, with short females generally having narrower and tall man longer morphology than their respective average counterpart. The IC is eccentric not round with a mean eccentricity of 0.58.

Conclusion

This study found (1) significant differences between short and average-height females and (2) provides physicians and medical device manufacturers with anatomical data relevant to radial head implant stem selection and development. Understanding the different morphology of the IC in patients with varying heights, now quantified, can aid clinicians in selecting implants that yield more fixation to the IC and reduce the rate of revision surgeries, in many instances caused by aseptic loosening.