Correlation study of forearm reference length and Apparent femur length for intramedullary nailing in Adults seen at Mulago hospital

Abstract

Background: The gold standard procedure for adult diaphyseal femoral fracture fixation is interlocking intramedullary nailing. Systematic preoperative planning includes the determination of appropriate nail length and size. This is vital for the success of this procedure. The main aim of this study was to determine the correlation between forearm reference lengths and apparent femur length and its association with height; therefore providing a guide for estimating femoral nail length in our adult population. Method: This was a cross sectional analytical study using a digital vernier caliper and stadiometer to measure forearm reference length, apparent femur length and standing height respectively. A total of 211(844 limbs) normal patient attendants were recruited into the study. Linear measurements included forearm reference length (FRL), apparent femur length (AFL) and the standing height (SH). Both the right and left upper and lower limbs were measured. Descriptive statistics were used to summarize the data. Student t-test was used for statistical comparison and Pearson’s correlation coefficient was used for statistical correlation. A p-value of less than 0.05 was considered statistically significant. Results: The mean FRL was 42.6 cm [p<0.001, 95% CI; 42.2-43.1] and 38.9 cm [p<0.001, 95% CI; 38.5-39.3] in males and females respectively. The mean AFL was 42.5 cm [p<0.001, 95% CI; 42.0-42.9] in males and 38.8 cm [p<0.001, 95%CI; 38.3-39.2] in the females. The overall mean forearm reference length and apparent femur length were 40.8 cm [SD, ±2.92] and 40.64 cm [SD,±3.01] respectively. The mean difference for the two measurements was equal in both sexes. Pearson correlation coefficient [r=0.98, p<0.001] was similar in both sexes as well. There was no significant variation with height in all age groups. viii Conclusion: There is significantly strong positive correlation between forearm reference length and apparent femur length. Forearm reference length therefore represents the maximum length of the nail that can be used in the femur. The length of the femur nail can be predicted by the forearm reference length in both sexes. In addition, there is no significant variation in apparent femur length and forearm reference length with the standing height of an individual.