Optimization of Anterior Incision Placement for Distal Biceps Repair.

Introduction Damage to the posterior interosseous nerve (PIN) is a known complication when using a cortical button during distal biceps tendon repair. Prior studies show that the trajectory of the drill through the biceps tuberosity can affect the distance from the PIN. We develop a mathematical model to predict the location of the tuberosity based on a palpable bony landmark and patient demographic factors. Methods The medical charts and elbow radiographs of (n = 82) adult patients were retrospectively reviewed. Using standard radiographic software, two observers measured the distance from the olecranon tip to the center of the biceps tuberosity. Multivariate regression analysis was used to build a linear model. The model was cross-validated with five arms from three distinct cadavers. A surgical wire was guided into the volar aspect of each forearm using the model, and a dissection was then performed to assess the proximity of the surgical wire to the insertion of the biceps tendon on the radial tuberosity. Results Olecranon-tuberosity distance (OTD) ranged from 52.3 mm to 77.2 mm (mean 66.5 mm). Univariate analyses revealed males had significantly longer OTD (mean 69.3 mm) compared to females (mean 61.2 mm, t-test, p < 0.001). Increased body mass index (BMI) weakly correlated with increased distance (Pearson's r = 0.22, p = 0.048). Height showed strong positive correlation with increased distance (r = 0.77, p < 0.001). Multivariate regression revealed that significant predictive factors for olecranon-tuberosity distance were height (coefficient = 35.8, p < 0.001), BMI (coefficient = 0.14, p = 0.032), and male sex (coefficient = 3.17, p = 0.0039). The average error in the cadaveric validation, measured as distance from the surgical wire to the distal biceps insertion was 1.8 mm. Conclusion A highly accurate mathematical model can be used to predict the location of the biceps tuberosity in relation to the palpable tip of the olecranon, based only on height, BMI, and sex of the patient. Knowledge of this distance can guide accurate placement of the skin incision when a transverse single-incision approach is utilized for repair of the distal biceps tendon using a cortical button. Diagnostics showed the model to be less accurate near the extremes of the measurement. Since patients with a target incision point far removed from average would most benefit from such a model, we will continue by identifying and enrolling patients at the low and high ends of the range. We further hypothesize that the technique described above could be similarly applied to benefit other procedures.