Subscapularis Peel for Open Reduction and Internal Fixation of Proximal Humerus Fractures With a Head Split

[Three-dimensional finite element analysis of exo-cortical placement of humeral calcar screw for reconstruction of medial column stability]

Objective

To explore the biomechanical stability of the medial column reconstructed with the exo-cortical placement of humeral calcar screw by three-dimensional finite element analysis.

Methods

A 70-year-old female volunteer was selected for CT scan of the proximal humerus, and a wedge osteotomy was performed 5 mm medially inferior to the humeral head to form a three-dimensional finite element model of a 5 mm defect in the medial cortex. Then, the proximal humeral locking plate (PHILOS) was placed. According to distribution of 2 calcar screws, the study were divided into 3 groups: group A, in which 2 calcar screws were inserted into the lower quadrant of the humeral head in the normal direction for supporting the humeral head; group B, in which 1 calcar screw was inserted outside the cortex below the humeral head, and the other was inserted into the humeral head in the normal direction; group C, in which 2 calcar screws were inserted outside the cortex below the humeral head. The models were loaded with axial, shear, and rotational loadings, and the biomechanical stability of the 3 groups was compared by evaluating the peak von mises stress (PVMS) of the proximal humerus and the internal fixator, proximal humeral displacement, neck-shaft angle changes, and the rotational stability of the proximal humerus. Seven cases of proximal humeral fractures with comminuted medial cortex were retrospectively analyzed between January 2017 and December 2020. Locking proximal humeral plate surgery was performed, and one (5 cases) or two (2 cases) calcar screws were inserted into the inferior cortex of the humeral head during the operation, and the effectiveness was observed.

Results

Under axial and shear force, the PVMS of the proximal humerus in group B and group C was greater than that in group A, the PVMS of the internal fixator in group B and group C was less than that in group A, while the PVMS of the proximal humerus and internal fixator between group B and group C were similar. The displacement of the proximal humerus and the neck-shaft angle change among the 3 groups were similar under axial and shear force, respectively. Under the rotational torque, compared with group A, the rotation angle of humerus in group B and group C increased slightly, and the rotation stability decreased slightly. All the 7 patients were followed up 6-12 months. All the fractures healed, and the healing time was 8-14 weeks, with an average of 10.9 weeks; the neck-shaft angle changes (the difference between the last follow-up and the immediate postoperative neck-shaft angle) was (1.30±0.42)°, and the Constant score of shoulder joint function was 87.4±4.2; there was no complication such as humeral head varus collapse and screw penetrating the articular surface.

Conclusion

For proximal humeral fractures with comminuted medial cortex, exo-cortical placement of 1 or 2 humeral calcar screw of the locking plate outside the inferior cortex of the humeral head can also effectively reconstruct medial column stability, providing an alternative approach for clinical practice.

Proximal humerus exposure with the inverted-L anterolateral deltoid flip approach, anterolateral deltoid splitting approach, and deltopectoral approach: A comparative cadaveric study

BACKGROUND

Reduction of the posterior aspect of proximal humerus fracture, such as far-retracted greater tuberosity or posterior articular head split fracture via a deltopectoral or deltoid splitting approach, is difficult and usually needs extensive dissection. The inverted-L anterolateral deltoid flip approach, which is developed from the deltoid splitting approach, accesses the proximal humerus via lateral deltoid flap lifting. This study compared the area and arc of surgical exposure to the proximal humerus of this proposed approach to existing approaches.

METHODS

Eleven cadaveric specimens were used. Deltopectoral and deltoid splitting approaches were carried out on the right and left shoulder, respectively. Soft tissue was retracted after completion of a surgical approach to expose the proximal humerus, and dot-to-dot marking pins were placed along the border of exposed area. An additional area with a full shoulder rotation was also marked on the deltopectoral side. An inverted-L deltoid flip approach was further carried out on a deltoid splitting side with a posterior extending incision along the acromion process and the deltoid detachment from the acromion process. The additional area of exposure was subsequently marked. All soft tissue around the proximal humerus was taken down, and the glenohumeral joint was disarticulated. Area of exposure and axial images were taken for further processing and measurement.

RESULT

An average distance of the axillary nerve from the acromion process of the deltoid splitting and the deltopectoral approaches were 49.15 mm and 57.35 mm, respectively (P < 0.05). The average area of exposure of the inverted-L deltoid flip, deltoid-splitting, deltopectoral, and deltopectoral with full rotation approaches were 2729.81mm², 1404.39mm², 1325.41mm², and 2354.78mm², respectively (P < 0.05). Mean arc of exposure lateral to bicipital groove of the inverted-L deltoid flip, deltoid splitting, deltopectoral, and deltopectoral with full rotation approaches were 151.75degrees, 105.02degrees, 61.68°, and 110.64°, respectively (P < 0.05).

CONCLUSION

The inverted-L anterolateral deltoid flip approach provides the most posterior access to the proximal humerus. However, it requires more soft tissue dissection and awareness of tension on the axillary nerve. This approach could be an alternative for displaced posterior head splits or far-retracted greater tuberosity proximal humerus fractures.