Chapter 3 Instability
CHAPTER 3 | Instability
wires in place (Fig. 3-14B). Although the 3.75-mm, fully threaded, cannulated titanium screws are self-drilling and self-tapping, it is recommended to use the 2.75-mm can- nulated drill to penetrate only the near cortex of the native glenoid prior to screw insertion. Due to the potential prox- imity of the screws to the suprascapular nerve posteriorly, it is advisable to rely on the self-drilling and self-tapping nature of the screws to penetrate the posterior glenoid cortex. The screw length depth gauge can then be used to help determine the proper screw length. Screw length is read directly from the back end of the shorter 6-inch guide wire and from the laser line of the longer 7-inch guide wire. We have found that the most common screw lengths are 34 mm for the more inferiorly positioned screw and 36 mm for the superior screw. Each screw is inserted over its guide wire using a can- nulated hex driver. One must be careful not to overtighten the screws as this may crack or damage the graft. Once the screws are almost fully seated, the surgeon double checks the position of the coracoid graft. If the position is satisfactory, the guide pins are removed and the screws are advanced to their fully seated position (Fig. 3-14C). Intraoperative AP and axillary x-rays are taken to confirm satisfactory position of the screws and graft. At this point, the surgeon assesses the stability of the Latarjet construct. One of the most amazing things about this construct is that, with the arm in abduction and external rotation and with a manually applied anteriorly directed force, the shoulder cannot be dislocated, even though the capsule has not yet been repaired. Capsular Reattachment Place 3 BioComposite SutureTak anchors (Arthrex, Inc., Naples, FL) into the native glenoid above, between, and below the cannulated screws to repair the capsule. This makes the graft an extra-articular structure and prevents its articulation directly against the humeral head, eliminating
glenoid (Fig. 3-12). The Parallel Drill Guide is invalu- able in placing the graft flush with the articular surface of the glenoid so that it is neither too far medial nor too far lateral (Fig. 3-13). It is important to be sure that the guide is angled slightly medially, toward the face of the glenoid, to achieve the proper screw insertion angle and to avoid any potential screw penetration into the articu- lar cartilage. Use a pin driver to advance the shorter (6 inches) of the two guide wires directly through the lower hole of the guide and graft and then into the glenoid neck. The guide wires are not terminally threaded to allow for better feel when the posterior glenoid cortex is penetrated. Next, advance the longer (7-inch) guide wire through the second guide cannulation (Fig. 3-14A). Next, remove the Parallel Drill Guide. Hold the graft firmly against the glenoid with an instrument (as the pegs may be tightly wedged into the coracoid drill holes) while the Parallel Drill Guide is withdrawn, leaving both guide FIGURE 3-12 Correct placement of the coracoid bone graft occurs when the graft is flush with the glenoid surface so that the arc of the glenoid is effectively extended. The Parallel Drill Guide (Arthrex, Inc., Naples, FL) facilitates proper placement of the graft. C, coracoid graft; G, glenoid.
FIGURE 3-13 Incorrect placement of coracoid bone graft. A: The graft must not be placed so that it protrudes lateral to the joint surface and acts as a bone block. Such placement produces a high incidence of late osteoarthritis. B: Conversely, it is important also to avoid medial placement of the graft because this can predispose to recurrent dislocation or subluxation.
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