Proximal versus distal screw placement for biceps tenodesis: a biomechanical study

Area of Science:

• Orthopedic biomechanics
• Materials science in medical devices

Background:

• Understanding the biomechanical properties of composite humerus models is crucial for evaluating orthopedic implants.
• Interference screws are commonly used in orthopedic surgery, but their optimal placement requires further investigation.

Purpose of the Study:

• To compare the maximum and end torque of fourth-generation composite humerus models with interference screws placed proximally versus distally.
• To assess the impact of screw placement on fracture patterns in composite humeri.

Main Methods:

• Twenty-four composite humeri were randomized into control, proximal screw, and distal screw groups.
• Interference screws were inserted 1 cm proximal or distal to the pectoralis major tendon insertion.
• Maximum and end torque were measured for each specimen.

Main Results:

• The control group exhibited the highest maximum torque (81.8 Nm) and end torque (80.7 Nm).
• The distal screw group showed significantly lower maximum torque (74.3 Nm, p=0.005) and end torque (71.8 Nm, p=0.033) compared to the control group.
• Fracture patterns differed between groups, with distal placement potentially increasing the risk of proximal humeral fractures.

Conclusions:

• Distal placement of interference screws in composite humerus models significantly reduces torque capacity.
• This reduction in torque may correlate with an increased risk of proximal humeral fractures.
• Proximal screw placement appears to maintain better structural integrity compared to distal placement.