Anterior instability—bone augmentation surgery: Primary and revision outcomes

Introduction

Osseous lesions in the humeral head and glenoid are commonly observed in patients with anterior shoulder instability. The prevalence of bone loss and pathologic bony changes increases with recurrent instability events. Identifying and understanding the pathologic changes in the bony architecture of the humerus and glenoid are paramount, and these lesions should be considered together. Patient-related factors, such as age and activity level, have to be considered when recommending treatment, as well as the nature of the pathologic bony changes.

The significance of acute and chronic glenoid bone loss (GBL) cannot be overstated. The presence of a glenoid bone fragment (bony Bankart lesion) is very important to identify and address following an instability event. Postreduction radiographs should always be acquired, and high-quality magnetic resonance imaging (MRI) or computed tomography (CT) scans are recommended if a fracture of the anterior glenoid rim is suspected. Evaluation of the size of GBL and how it relates to compression fractures of the humeral head is also of utmost importance.

Regardless of the mechanism of dislocation, postreduction plain radiographs should be one of the first steps of patient diagnostic workup. Radiographic imaging is more readily available in an emergent setting, and the use of this modality to assess for damage to the osseous architecture of the shoulder offers an efficient, low-cost, and low-radiation diagnostic alternative to MRI or CT. True anteroposterior (AP) view, axillary view, West Point view, and Bernageau view radiographs ( Fig. 33.1 ) are generally recommended in studies reporting the accuracy and reliability of specific patient positions for the assessment of GBL. In addition, the Stryker notch view provides good visualization of the humeral head and is useful for assessment of Hill-Sachs lesions (HSLs). For this view, the body is rotated 15 to 45 degrees so that the scapula is parallel to the film. Then, the patient abducts the shoulder and places the hand on the head or neck, and the x-ray is angled approximately 10 degrees cephalad.

In the first-time dislocator with suspected bony defects or patients with a history of multiple instability events, CT imaging with three-dimensional (3D) reconstructions should be obtained to fully evaluate for both soft tissue and bony defects. In the setting of traumatic glenoid fracture, recurrent anterior glenohumeral instability, or ligamentous hyperlaxity, CT or MRI scans may be obtained if indicated by the patient’s history and physical examination. Two-dimensional (2D) CT with 3D renderings of the pathologic shoulder are required to most accurately assess the extent and location of GBL and/or the presence and size of HSLs in cases of recurrent anterior instability and suspected attritional GBL. MRI should be obtained to assess the integrity of the labrum, capsule, glenohumeral ligaments, rotator cuff, and rotator interval. If done with standardized protocols, MRI can also achieve equivalent accuracy as CT for bone loss evaluation. However, it is important to reformat the CT or MRI and make adjustments for coronal and sagittal rotation ( Fig. 33.2 ).

A bony lesion on the humeral head (HSL) is common following first-time instability events ( Fig. 33.3 ). HSL, first described by Hill and Sachs in 1940, is a compression fracture on the posterior aspect of the humeral head and is associated with anterior shoulder dislocation. Hill and Sachs correctly identified a relationship between the presence of the HSL and unsuccessful operative treatment of anterior shoulder instability. The incidence of HSLs vary from 40% to 100% of all anterior shoulder instability events, and the incidence seems to increase with repeated dislocation events. The HSL is located on the posterosuperolateral aspect of the humeral head as it comes into contact with the anterior-inferior glenoid. The cancellous bone of the humeral head is soft and prone to compression fractures. Repeated instability events cause enlargement of the HSL. Whether an HSL contributes to risk of dislocation depends on the depth, size, or length of the HSL as well as the location of the lesion.

The HSL should be considered together with concomitant soft tissue and other bony lesions. The soft tissue lesions pertaining to anterior shoulder instability include damage to the capsulolabral structures, including the glenohumeral ligaments ( Fig. 33.4 ). Concomitant glenoid bone lesions are important when considering the significance of the HSL, overall instability, and recommendation of treatment strategy.

Bone augmentation procedures following first-time anterior dislocation

Disimpaction of Hill-Sachs lesions

Large HSLs can be considered for disimpaction in the acute setting (<3 weeks). ^, Alternatively, an inflated balloon can be used to reduce the HSLs. There is a paucity of literature reporting clinical outcomes, and it is not a common procedure.

Bony bankart lesion

A bony Bankart lesion ( Fig. 33.5 ) is a fracture of the anterior glenoid rim and is observed following a first-time dislocation event in 9% of cases. ^, The fracture is caused when the humeral head dislocates over the anterior glenoid rim and the fracture fragment has been thought to resorb over time. Screw fixation is possible ; however, this may be difficult due to the small size of the fragment and requires alternative fixation methods. Godin et al. reported good mid-term results utilizing the arthroscopic bony Bankart bridge technique in which the capsule-labral-bony fragment is reduced and fixed with suture anchors. At a mean follow-up time of 6.7 years, the patients reported mean American Shoulder and Elbow Surgeons score of 93.1, mean QuickDASH score of 6.2, and a mean Single Assessment Numeric Evaluation score of 92.8. However, three of 13 patients reported recurring instability symptoms.

Augmentation of glenoid defects

Historically, bone augmentation has been considered in the chronic setting when GBL was above 20% to 25% ( Fig. 33.6 ). With GBL of less than 20%, most surgeons opt for soft tissue repair (Bankart repair) with and without soft tissue augmentation (capsular shift, remplissage, etc.). However, Shaha et al. demonstrated that GBL as low as 13.5% was associated with clinical failure in an active, high-demand population following arthroscopic Bankart repair. The instability severity index score (ISIS) was developed by Balg and Boileau to identify patients who are at greater risk for recurrent instability after an arthroscopic Bankart repair. Six risk factors were identified:

1.

presence of an HSL on an AP shoulder radiograph ( Fig. 33.7 B) with the shoulder in external rotation (2 points)

Fig. 33.7

(A) Right shoulder in the true anteroposterior view (Grashey view). Notice the arrows that delineate the sclerotic line due to deficiency of the anterior glenoid rim. (B) The arrows show a Hill-Sachs lesion, which is clearly visible with the left shoulder in external rotation on an anteroposterior radiograph.

(From Di Giacomo G, Peebles LA, Pugliese M, et al. Glenoid track instability management score: radiographic modification of the instability severity index score. Arthroscopy . 2020;36:56–67.)
2.

loss of contour of the inferior glenoid on a true AP shoulder radiograph (see Fig. 33.7 A) (2 points)
3.

age ≤ 20 years (2 points)
4.

athlete at a competitive level (2 points)
5.

contact sports or those involving forced overhead activity (1 point)
6.

shoulder hyperlaxity (1 point)

Patients with a score of more than 6 points on the 10-point scale have a 70% risk of recurrent instability following arthroscopic Bankart repair. Thus the authors suggested that these patients should be considered for an augmentation procedure, such as the Latarjet coracoid transfer. Phadnis et al. found a 70% recurrence of instability in 141 patients in patients scoring 4 or more points and suggested that a cut-off of 4 points be used instead of 6 points; this cut-off was confirmed in a similar study by Thomazeau et al. Although the reliability of ISIS has been demonstrated to be good in some studies, other studies did not find that ISIS predicted recurrent instability. ISIS utilizes conventional radiographs to identify presence of HSLs and GBL and does not consider the interdependency of the bone defects on the humerus and glenoid. However, the significance of humeral and GBL must be considered together.

Burkhart and De Beer were the first to describe this relationship when they distinguished between engaging and nonengaging HSLs. The HSL is said to be engaging if it docks into the anterior glenoid rim. The concept was further developed by Yamamoto et al. when they defined the glenoid track concept. In a cadaveric study, these authors defined the glenoid track on the humeral posterior articular surface, which is in contact with the glenoid in end-range movement ( Fig. 33.8 ). As long as the HSL is contained within the glenoid track, it will not engage and thus not contribute to recurrence of instability. However, if the HSL extends medially over the glenoid track, there is risk of engagement. Omori et al. demonstrated the clinical validity of the glenoid track concept in vivo and defined the glenoid track as 83% of the glenoid width when the arm was in 90 degrees of abduction.

Di Giacomo et al. incorporated the glenoid track system into ISIS and presented the Glenoid Track Instability Management Score (GTIMS). The GTIMS is similar to ISIS, but the 4-point imaging part has been replaced by on-track/off-track status. An off-track HSL contributes 4 points to the total score and an on-track HSL contributes 0 points. Compared to ISIS, the GTIMS resulted in a more conservative recommendation with fewer Latarjet indications and more patients treated with arthroscopic Bankart. An overview of indications for stabilizing procedures based on GBL and on-track/off-track status is provided in Table 33.1 .

TABLE 33.1

Treatment Options Based on Glenoid Bone Loss (GBL) Size and Whether the Hill-Sachs Lesion (HSL) is On-Track or Off-Track

GBL (%)	On-Track HSL	Off-Track HSL
0%–13.5%	Arthroscopic Bankart repair	Arthroscopic Bankart repair + remplissage
		Open inferior capsular shift
		Latarjet procedure
13.5%–25%	Arthroscopic Bankart repair + remplissage	Arthroscopic Bankart repair + remplissage
	Open inferior capsular shift	Open inferior capsular shift
	Latarjet procedure	Latarjet procedure
>25%	Latarjet procedure	Latarjet procedure

Surgical augmentation of glenoid bone defects

Several graft options have been used in the treatment of recurrent anterior instability, including the coracoid process, iliac crest bone block, distal clavicle, and tibia bone block. Today, the most common alternative is coracoid bone block transfer followed by iliac crest bone block.

Coracoid transfer

Numerous eponyms have been used to describe coracoid transfer in the treatment of anterior shoulder instability. The procedure has been attributed to Michel Latarjet, who published a description in 1954. In the same edition of the same journal, Trillat also described an identical procedure. Four years later, Helfet described a coracoid transfer procedure that was similar to the one described by Latarjet—the main difference being that only sutures were used to fix the coracoid process. He attributed the procedure to his mentor, Rowley Bristow, hence the eponym Bristow was used for the procedure. To exacerbate the confusion, numerous modifications have been described to the original procedures.

For simplification, we will use the term Latarjet procedure for all coracoid transfers in the treatment of anterior shoulder instability. It has been proposed that the Latarjet procedure increased anterior shoulder stability by three different contributions :

1.

Restoration of GBL
2.

The sling or hammock effect of the conjoint tendon
3.

Enhanced anterior capsular resistance following repair of the attenuated capsule to the stump of the coracoacromial ligament (CAL)

Surgical technique

Patient positioning

The patient is placed in the beach chair position and the surgeon should be able to abduct and externally rotate the arm intraoperatively, and the arm is placed in an arm holder or a padded Mayo stand. A standard diagnostic arthroscopy may first be performed with the patient in the beach chair position to confirm the glenohumeral osseous deficiency warranting the Latarjet procedure or to treat concomitant intra-articular glenohumeral pathology, including the posterior and superior labrum or cartilage defects. In a revision setting, sutures, anchors, and other hardware would be removed, and the preparation of the glenoid neck and cancellous bone would be started.

The proximal portion of the standard deltopectoral approach can be utilized with the skin incision starting at the tip of the coracoid process and extending vertically 5 cm toward the axillary fold. The medial branches of the cephalic vein are cauterized, and the vein is then taken laterally.

The CAL is then exposed with the arm in abduction and external rotation ( Fig. 33.9 ). The CAL is transected approximately 1 cm from the ligament’s insertion on the coracoid, leaving sufficient tissue for later capsular repair. Placing the arm in adduction and internal rotation improves visualization of the medial aspect of the coracoid process and relaxes the neurovascular structures. The pectoralis minor is now released from the medial aspect of the coracoid, and then a periosteal elevator can be utilized to remove soft tissue in preparation for the osteotomy.