Chapter 3 Instability

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CHAPTER 3 | Instability

Pearls, Pitfalls, and Decision-making: ■ With bipolar bone loss, we must measure and quantify the glenoid bone loss and the humeral bone loss to determine three things: ■ Does the patient need a Latarjet reconstruction? ■ In general, if the patient has lost more than 25% of the inferior glenoid diameter, we recommend Latarjet because this group of patients has a very high failure rate with arthroscopic repair. ■ If the patient is a candidate for arthroscopic repair, should we do an arthroscopic remplissage in addi- tion to an arthroscopic Bankart repair? ■ If there is <25% glenoid bone loss, he is a candi- date for arthroscopic repair. ■ If the Hill-Sachs lesion is on-track (nonengaging) , then arthroscopic Bankart repair alone is sufficient. ■ If the Hill-Sachs lesions is off-track (engaging) , then arthroscopic remplissagemust be performed in addition to arthroscopic Bankart repair. ■ How do we determine if a Hill-Sachs lesion is on track or off track ? ■ We must calculate the width of the glenoid track (GT) as well as the width of the Hill-Sachs inter- val (HSI). If GT > HSI, the Hill-Sachs lesion is on track . If GT < HSI, the Hill-Sachs lesion is off track. ■ The glenoid track (GT) is calculated by the for- mula GT = 0.83D − d, where D = inferior diam- eter of glenoid and d = width of bone loss from glenoid. ■ The Hill-Sachs Interval (HSI) is composed of the width of the Hill-Sachs lesion (HS) plus the width of the bone bridge (BB) between the Hill- Sachs lesion and the rotator cuff attachments on the humerus. ■ Calculating the width of the glenoid track (GT) ■ In this case, a calibrated probe is used to measure the distance from the bare spot to the posterior glenoid rim (R). Since the bare spot of the glenoid represents the center of the inferior glenoid, this distance equals the radius (R) of the inferior gle- noid. So D (diameter) = 2R. In this case, R = 15, so D = 30 (Fig. 3-128). ■ To calculate the width of the lost glenoid bone, one must subtract the distance from the bare spot to the anterior glenoid rim (10 mm in this case) from the radius (R), which is 15 mm (Fig. 3-128). Therefore, D = 5. ■ Plugging these values into the formula: GT D d = 0 83. − GT = × 0 83 30 5 . − GT mm = 19 9. ■ We next measure the width of the Hill-Sachs Interval (HSI) by using the tip of the calibrated probe (4 mm length) to assess the diameter of the Hill-Sachs (HS) (Fig. 3-129) and the bone bridge (BB) (Fig. 3-130).

The Cowboy’s Conundrum: Recurrent Anterior Dislocations with Bipolar Bone Loss The Surgeon’s Solution: Arthroscopic Bankart Repair and Remplissage History: ■ A 33-year-old recreational athlete dislocated his left shoulder 6 weeks ago in a city league basketball game. He has had two previous anterior dislocations. All three dislocations required closed reduction in the emergency room. Physical Exam: ■ Full range of motion ■ Normal strength ■ Positive apprehension sign in abduction and external rotation Imaging: ■ X-rays show a moderate-sized Hill-Sachs lesion. ■ MRI shows a Bankart lesion. ■ 3D CT scan shows 10% loss of the inferior glenoid diameter. Arthroscopic Findings: ■ Bankart lesion with erosive bone loss can be seen (Fig. 3-127). ■ Moderate-sized Hill-Sachs lesion (Fig. 3-127).

Video 3-21

FIGURE 3-127  Erosive bone lesion of the glenoid accompanies the Bankart lesion. In addition, a Hill-Sachs lesion is identified at the posterior aspect of the humeral head. G, glenoid; H, humeral head.