Predicting hamstring graft size before anterior cruciate ligament (ACL) reconstruction is crucial to avoid subsequent graft failure. Our study aims to (1) develop a generalized algorithm to predict final ACL graft diameter for single- and double-tendon hamstring grafts consisting of any number of folds, (2) evaluate our algorithm with a regression model adjusting for patient and surgical factors, and (3) assess algorithm's specificity, sensitivity, and discriminative ability, defining adequate graft size as ≥9 mm.

We conducted a retrospective review of 105 patients who underwent primary ACL reconstruction with either single- (semitendinosus or gracilis only) or double-tendon (both semitendinosus and gracilis) hamstring grafts from January 2023 to June 2024 at a tertiary institution. Magnetic resonance imaging (MRI) scans were independently measured by two junior members. The average of the measurements was taken. Predicted graft diameter is √(x·AB + y·CD), where A and B are the semitendinosus cross-sectional length and breadth, C and D are the gracilis cross-sectional length and breadth, and x and y are the number of semitendinosus and gracilis folds, respectively.

Pearson correlation shows moderate correlation between predicted and actual graft diameters (R = 0.602, p < 0.01). Univariate and multivariate linear regression, adjusted for age, gender, body mass index (BMI), and graft type, indicate that males, overweight individuals, and those with single-tendon grafts are more likely to have larger actual graft diameters (p < 0.05). Our algorithm has a sensitivity of 95.8%, specificity of 69.7%, with excellent discriminative ability (AUC = 0.889). A high 82.9% agreement rate was achieved, with Cohen's kappa of 0.578 (p < 0.05).

This study has demonstrated a practical generalized algorithm with high sensitivity (95.8%) to predict the final ACL graft diameter for single- and double-tendon hamstring grafts consisting of any number of folds using preoperative MRI measurements.

Received: 10 April 2025

Accepted: 30 August 2025

Accepted Manuscript online:
04 September 2025

Article published online:
16 September 2025

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