Preoperative estimation of humerus intramedullary nail length using clinical landmarks

Intramedullary interlocking nailing is one of the accepted methods of treating humerus diaphyseal fractures. Appropriate nail length and diameter are of paramount importance to achieve a stable fracture fixation. Estimating the nail length can be as challenging in certain cases as it is important. This study aims to provide an easy-to-use formula utilizing clinical measurements from contra lateral arm to accurately estimate humeral nail length.

This descriptive cross-sectional study was conducted at 3 tertiary care hospitals in Mangalore, India. Patients above the age of 18 years coming to the outpatient department with elbow, shoulder or arm complaints requiring radiological investigation from July 2021 to July 2022 were included. Patients with fractures or dislocations of upper limbs, malunited or non-united fractures of upper limbs, congenital or developmental deformities and patients with open growth plates were excluded. Patients' variables (like age and gender), radiological humerus length and contralateral arm clinical measurements were recorded. An independent samples t-test was used for univariate analysis, and linear regression analysis was done to estimate the desired nail length using the clinical measurement of the humerus (cm) in both genders separately. The significance level was set at p < 0.05.

Our study included 204 participants of which 108 were male and 96 were female. The formula for predicting humeral nail length in males is (-2.029) + (0.883 × clinical measurement). The formula for females is 1.862 + (0.741 × clinical measurement). A simplified formula to determine humeral nail length is 0.9 clinical length - 2 cm (in males) and 0.7 × clinical length + 2 cm (in females).

To improve the stability of fixation with intramedullary nails it is imperative to select the appropriate nail length. There have been studies that devised reliable methods of determining nail lengths in the tibia and femur using preoperative clinical measurements. A similar clinical method of determining humeral nail length is lacking in the literature. Our study was able to correlate radiological lengths of the humerus medullary canal with clinical measurements performed using anatomical landmarks to arrive at a formula. This allows for a reliable and easy nail length determination preoperatively.