Arthroscopic congruent-arc shoulder bone-block for severe glenoid bone defect: Preliminary report

Glenoid bone defect remains a surgical challenge in managing anterior shoulder instability. The technique first described by Latarjet has become the gold standard, but may fail to restore fully normal anatomy in case of severe "inverted-pear" glenoid bone defect. Likewise, the naturally "banana-shaped" coracoid process fails to match this flat shoulder. The congruent-arc modified Latarjet technique, which consists in pivoting the coracoid process through 90°, optimizes the contact surface, adapting to the glenoid curvature radius and increasing the articular surface of the graft.

The present study hypothesis was that the congruent-arc bone-block technique could be performed entirely under arthroscopy. The main study objective was to assess the postoperative increase in glenoid surface area. The secondary objective was to assess whether the technique provided anatomic glenoid reconstruction.

Five patients with inverted-pear glenoid were recruited in a preliminary prospective study. Immediate postoperative coracoid process length, width and thickness were measured on 2D CT scan and bone-block flushness was assessed using a straight-line and a circle. Glenoid surface area and coracoid graft area were also measured.

Mean coracoid process length was 2.62cm (range, 2.17-3.05cm), width 1.52cm (range, 1.28-1.75cm) and thickness 1.16cm (range, 0.9-1.3cm). Mean preoperative glenoid area was 5.62 cm² (range, 4.76-6.31cm²) and the articular area of the coracoid process was 2.78 cm² (range, 2.43-3.27cm²). The coracoid graft thus increased glenoid area by a mean 49.2% (range, 41-53%). Axial CT slices systematically showed good bone-block positioning.

The congruent-arc technique can be performed entirely under arthroscopy, and provides anatomic glenoid reconstruction. It offers an option in case of severe inverted-pear glenoid bone defect.

Prospective.

III, case-control.