Fig. 19.1
Posterior glenoid deficiency evaluated by TC 2D “Pico technique”
Burkhart and De Beer [4] analyzed a cohort of 194 arthroscopic Bankart procedures performed on athletes in order to identify specific factors related to the recurrent instability. Bony lesion on the glenoid side, getting the glenoid to the “inverted pear” shape, and the ones at the humeral side were identified as the main factors affecting the postsurgical recurrences after the arthroscopic Bankart treatment. They assumed that the Hill-Sachs lesion [5] is at risk when its orientation matches the glenoid rim at 90° of abduction in maximal external rotation. This pattern was named “engaging Hill-Sachs lesion.” Although this observation represented a starting point, it was not definitively exhaustive.
Athletes’ needs are peculiar compared to those of the standard population; several factors, indeed, affect the sport season and the career. As a consequence, the treatment has to be related to these needs. The elite athlete is exposed to specific risks at an early age. The onset of the instability is mainly due to trauma, either in a normal shoulder or in a constitutional ligament laxity.
According to the literature [6], patients with less than 15 % of glenoid bone loss can be successfully treated by soft tissue procedures. If the deficit exceeds the 25 % of the surface, these are not sufficient. Bony procedures are indicated for these cases. In between these values, several factors influence the decision-making [7].
Bone deficiency can be due to a single dislocating episode as to recurrent ones; it also can be a consequence of attritional mechanism in overhead athletes due to the anterior capsule being stretched allowing the humeral head repetitively riding the anterior glenoid edge. Each of these sports-related mechanisms and specific instability patterns lead to different treatments and surgical approaches. The literature review shows significant differences among authors’ treatment choices for the same anatomic lesions: depending on the surgeons’ country of origin or their confidence with a procedure over another. Since objective data are the bases for supporting a treatment over another, imaging techniques have a great value when choosing bone procedures, when these can be challenged by soft tissue procedures and when soft tissue procedures are the best choice.
Another aspect, more crucial for athletes than in other population, is the choice, surgical or conservative, at the first dislocation episode.
19.2 Mechanical and Clinical Correlations
The bone loss deficit is due to the energy transmitted by the dislocating humeral head against the glenoid. High-energy dislocations, typical of collision sports (football, rugby), produce glenoid rim fractures in an acute traumatic episode. The dislocation can either occur with the arm in elevation abduction or, specific of collision sports, in mild abduction, forced extension and external rotation while the arm is caught by an antagonist player. This can lead to different orientations of the humeral bony lesion.
Low-energy mechanism of dislocation causes smoothing of the glenoid, getting its deficiency over the time. The last, affecting lax morphotype patients, is typically the one of overhead sportsmen (javelin throwers, baseball players), sometimes with no evidence of dislocations (the so-called minor instability) [8]; it is associated with stretched anterior capsule, superficial and peripheral Hill-Sachs lesions, partial articular side cuff lesions [9], and posterior capsular stiffness. The onset of the problem in these cases lacks a major trauma, where it is the rule into determining the glenoid fractures. In between these two opposite trauma patterns, the most frequent one is traumatic dislocation due to overstretched arm in external rotation and abduction, causing the avulsion from the glenoid of the labrum and its attached capsule-ligament complex (Bankart lesion) with or without a bony fragment (bony Bankart). At the time of injury, the high-energy dislocations need external maneuvers to accomplish the joint reduction, often requiring anesthesia, whereas the low-energy ones of constitutional lax shoulders do not. The time elapsed from dislocation to the joint reduction results in deepening of the Hill-Sachs lesion, since the cancellous bone of the greater tuberosity is soft. Furthermore, the rotator cuff units, stretched in the dislocating position of the humerus, act vigorously in the healthy shoulder of an athlete, getting the humeral head to be compressed against the glenoid edge: the posterior bone defect deepens and the reduction gets more difficult over the hours.
In order to give the best treatment to the athlete, we have to properly understand the natural history of the instability. The Bankart labral lesion [10] occurs in about 97 % of dislocations. Glenoid bone insufficiency stands at 20 % of patients at first dislocation, rising fast in the recurrences, to reach about 90 % in the post anterior stabilization recurrences; this is due either to the mechanical impact during the dislocation or to the loss of bone substance caused by the surgical implants.
Bony defect, either humeral or glenoid sided, impairs one of the mechanisms of shoulder stabilization. Others are the glenohumeral static stabilizers (capsule and ligaments) and the dynamic ones (the rotator cuff units and the scapula-thoracic muscles). The concavity compression depends on several factors: bone morphology, cartilage thickness, and height of the labrum. The thickness of the cartilage at the glenoid periphery gives a huge contribution to the concavity of the glenoid fossa and thus to stability; its loss is missed by CT and x-ray investigations. As these show bone damage, even initially, we can assume that half or more of the glenoid deepness is lost.
The amount of bone insufficiency to get the shoulder unstable is not well defined.
19.3 Diagnosis
19.3.1 History
The suspicion of significant bone lesions should arise from instances of a high-energy trauma, arm abducted over 70° and extended, and when the first traumatic episode is followed by subluxations for negligible traumas or by apprehension and/or instability with the arm externally rotated at less than 60° of abduction (mid-range post-traumatic instability). Similar findings of mid-range instability but without a major trauma are typical either in constitutional multidirectional instability or in unstable shoulders due to massive cuff tears (the latter much more common in older patients).
19.3.2 Physical Examination
Patient examination starts by the inspection of both shoulders, mainly the backside, focusing on muscle atrophy and scapular diskinesia. The specific tests for anterior instability are assessed: anterior load and shift test, anterior drawer test, anterior apprehension test, Jobe relocation test (fulcrum test) [9], throwing test, and bony apprehension test. The last one, similar to the standard apprehension test, is performed with the arm at a 45/60° of abduction; if positive, it means that the bony lesion is the cause of instability. The dynamic anterior jerk test is usually performed under anesthesia.
19.3.3 Imaging
The West Point radiologic view, tangential to the anterior-inferior glenoid margin, is very effective to detect its bony defect. Early after the dislocation, the patient’s compliance can be inadequate to maintain the position with arm abducted at 90°; in this case, the Garth (apical oblique) can be an alternative [11]. The patient is seated with the arm adducted and internally rotated; the x-ray beam is tilted 45° caudally and from the plane of the scapula. Hill-Sachs lesions as subluxations are thus detected. The Stryker notch view can assess the Hill-Sachs lesion and its size and orientation. The patient’s hand is placed on top of the head; the x-ray beam is tilted 10° superiorly and centered to the coracoid process, going through the humerus and aiming the cassette placed against the posterior shoulder.
The bony lesions were classified by Bigliani into three types: displaced avulsion of the glenoid rim along with the capsule attachment (type 1), medially displaced fragment (type 2), and glenoid rim erosion (type 3).
As the presence of bone insufficiency is defined and the surgical procedure has to be set, further imaging exams should be carried out in order to properly assess the bony lesions at the glenoid and the humeral sides. The arthro-MRI is useful to study soft tissue lesions and cartilage damages; its role is dominant in the diagnosis of GLAD lesions, Bankart or SLAP lesions, HAGL and RHAGL lesions, and the articular-sided rotator cuff lesions. Its two-dimensional images and the intercut distance, often too big, may underestimate the degree of bone loss, losing its significance in the evaluation of bone insufficiency. The computed tomography is the most affordable exam to evaluate bone defects. The two-dimensional CT accuracy can be impaired by variations in the glenoid version, since the beam should be exactly parallel to the glenoid surface. The goal could be impossible in individuals with glenoid having different versions among the upper and lower glenoid surface, since these come from different ossification centers. Few years ago, in order to study bone defects, several authors developed original 2D CT scan techniques [12], since it was more widely available than the 3D. All these started from Huysmans’ observation [13] that the inferior aspect of the glenoid has the shape of a true circle. It gets possible to quantify the glenoid lesions. The percentage of bone loss is determined by the difference between the radius of the best-fit circle of the intact glenoid surface and the one at level of the defect. PICO is the method we are still using today, having been using it since its release; we now complete the CT study by 3D images.
The 3D CT exam reconstruction, indeed, completed by images with subtraction of the humeral head, today is the gold standard in obtaining information about the extent and the pattern of bone injury or loss. Imaging methods quantify both the glenoid circle radius deficit and the deficiency in superior-to-inferior length.
The arthroscopic measurement of the glenoid deficit, as suggested by Burkhart, based on the bare spot can be imprecise. Kralinger et al. verified by CT that the bare spot is about 1.4 mm anterior to the true center of the best-fit circle, getting the deficit to be overestimated. Similarly, Huysmans demonstrated that the bare spot is not identifiable in all the glenoid. The arthroscopic view, on the other hand, gives nicely detailed information about the pattern of the insufficient glenoid and the extent of the defect. The most common glenoid shape is pear-like (88 %); facing the oval-shape pattern (12 %), the surgeon could overestimate the bone loss. Furthermore, he can miss proper information about the osseous fragment, hidden by scar tissue and the attached capsule labrum itself. The anterior-to-posterior glenoid diameter measures on average 24–26 mm. As beyond 25 % of bone loss, the soft tissue procedures fail; it means that 6–8 mm is the borderline to shift to an osseous augmentation procedure.
19.4 Instability with Bone Deficiency: Treatment
There is consensus about the need of surgical treatment for patients with bony instability over the nonoperative one, with limited exception of some true glenoid fractures: these last, indeed, can heal with no consequences to those structures put at the head of the stability. In the past were used just the open techniques as bone augmentation procedures; later on, new arthroscopic or combined techniques have been described for this purpose [14, 15]. These increase the armamentarium for the treatment of “instability with bone deficiency.” The actual issue is that albeit the arthroscopic procedures could allow a detailed examination of all articular structures, giving evidence of their eventual pathology, they are evolving and not yet standardized. Conversely, the open techniques allow treatment of just the bone defect and the anterior capsule lesions, not the accessory ones.
The standard open approach for anterior shoulder instability procedures is the deltopectoral approach. It is, ideal to give access to the anterior structures, not optimal to treat the posterior Hill-Sachs lesion. To approach them, the takedown of the long biceps and forced maneuvers of internal rotation and extension are necessary. This event, when complete detachment of the subscapularis is met, can result to muscle changes with some postoperative insufficiency, crucial in case of revision surgery [16]. Other lesions such as the posterior and superior labrum tears are hidden to the anterior operative field.
19.4.1 Hill-Sachs Defects
The defect on the humeral side is one of the two bony predisposing factors (the other being the glenoid deficiency) for recurrence of dislocation after Bankart repair in athletes.
There is no evidence that the size of the defect is significant for stability. Most authors state it is between 20 and 40 %. Sekya reported that a defect as small as 12 % can somehow be mechanically significant to affect stability [17]. Yamamoto studied the relationship of humeral and glenoid contact introducing the concept of “glenoid track” [18]; then recently, Di Giacomo et al. [19] published the concept of “in track” and “off track” of the Hill-Sachs lesion, defining the latter as the one at risk for dislocation.
Nonanatomic procedures are mainly focused on the external rotation limitation. The subscapularis and the capsule are shortened by doubling them (Putti-Platt) or are detached and transferred laterally (Magnuson-Stack). All these can lead to osteoarthritis and are not indicated for athletes, since they badly affect the external rotation.
The humeral osteotomy, as proposed by Weber, is practically abandoned: performed at the superior margin of the pectoralis major attachment, which puts the humeral defect somehow away, far from the anterior glenoid rim.
Several anatomic techniques have been proposed; their aim is to give back convexity to the humeral head. The use of a fluoroscopic-guided humeral tamp, inserted through a cortical window just lateral to the biceps groove, to elevate the depressed humeral head has been described as other similar techniques are described. Several authors suggest to fill the humeral defect by bone graft through a posterior approach, limited or not, or an anterior extended one. The graft is fixed by headless screws or contoured and inserted press-fit. Graft failure and resorption are possible complications. The described mosaicplasty could be inadequate since the plugs are unstable.
The attempt of reduction under anesthesia of fixed posterior dislocations with reverse Hill-Sachs lesions limited to less than 25 % of the articular surface is possible within 3 weeks from trauma. In the pattern of fixed posterior dislocation, the reverse Hill-Sachs lesions, anterior, are well addressed by the standard deltopectoral approach: in these cases, the humeral filling by graft is often the procedure of choice [20], even in athletes. The large defects, involving half humeral head, can be managed by humeral head replacement, partial (hemi-cap) or not. This should be avoided in young patients. The significant defects can be assessed by several procedures: the MacLaughlin (the subscapularis inserted into the defect) or its modification suggested by Neer (the lesser tuberosity is transferred). Subscapularis weakness can be the effect of its medialization.
The most actual procedure as treatment of the Hill-Sachs lesion in the anterior shoulder instability, named “remplissage,” has been proposed by Purchase in 2008: the posterior humeral side defect is filled by capsule and infraspinatus tendon. This refers to the procedure originally proposed by Connolly in 1972.
The remplissage technique consists of a few steps: freshening the defect’s surface by peeling the cartilage islands to the subchondral bone, getting a dense, bleeding surface; going to the subacromial space shaving the soft tissues, thus obtaining space for the suture tightening; going back inside to insert anchors; passing the anchors’ sutures through the infraspinatus and capsule; and tightening the sutures. We skip the subacromial step, boring, accepting some few deltoid fibers could be involved within the suture limbs.
Several authors support the efficacy of filling the Hill-Sachs lesion by the infraspinatus tendon as effective to gain stability, but few articles describe its related effects on movement restriction or side symptoms. These aspects are crucial when regarding an overhead sportsman, whose performance is strictly dependent on the amplitude of the external rotation of the abducted arm. Just one level 2 prospective study (Nourissat) [21] compares two groups of patients with humeral side defect, without glenoid bone deficiency: one treated by the added remplissage, the other by just the Bankart repair. He found limitation of movement at 1 year after the remplissage procedure. The mean value of this are: ER1 13°, ER2 18.5, forward elevation 14°, and IR 2 vertebra levels. Although not statistically significant, there is a slight difference with the Bankart procedure alone. One third of patients in the remplissage group had residual pain after 2 years. The author suggests the incomplete tendinous healing its cause; conversely we mean that this can be explained by the early impingement of the articular side cuff, medialized, and the posterior glenoid rim (internal impingement). This irritative mechanism is likely to affect overhead elite athletes reducing the indication of the infraspinatus tenodesis versus the competitor Latarjet procedure.
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