Laurent LaFosse, MD; Christian Moody, MD; and Leonard Achenbach, MD
Shoulder anterior instability may present with different symptoms: shoulder dislocation, subluxation, or simple pain. As soon as the shoulder dislocates, the inferior glenohumeral ligament (IGHL) can be damaged along with labral detachment and a potential bony lesion. These problems when combined commonly lead to recurrent instability. In cases of isolated labrum detachment, arthroscopic reattachment provides excellent results, but in our experience as soon as the IGHL is involved during a dislocation, long-term results of soft-tissue reattachment are poor. Management of shoulder instability in young collision athletes with soft tissue stability alone remains problematic with high revision and recurrent dislocation rates.1,2 A variety of open and arthroscopic treatment methods exist and are described in this textbook. Our preferred technique not only for athletes but for patients with recurrent anterior instability, instability secondary to any bony Bankart lesions, off-track lesions including bipolar lesions, and those with humeral avulsions of the glenohumeral ligament (HAGL) is that of an arthroscopic Latarjet. The arthroscopic Latarjet has several advantages over the traditional open Latarjet procedure described in 1954.3 These advantages include better visualization of the entire joint, which allows for optimum graft placement as well as management of concomitant lesions of the posterior and superior labrum. In addition, direct visualization of the axillary nerve and surrounding hypervascular tissue allows for reducing the change of a neurovascular injury.4,5
The Latarjet procedure is successful in stabilizing the shoulder through several key mechanisms. First, the coracoid transfer provides static stability by increasing the glenoid surface area, which results in a greater articular arc, thus preventing a Hill-Sachs lesion from engaging the anterior rim. Second, the conjoint tendon serves as a dynamic reinforcement of the inferior capsule providing a “hammock” effect, particularly when the shoulder is in its most vulnerable position of abduction, external rotation. Last, the intersection between the split subscapularis tendon and the conjoint tendon provides further dynamic tension to the inferior portion of the subscapularis tendon, again with the most tension during the position of highest vulnerability.4,5 Further details describing all pathology and mechanisms of stabilization will be described in the following text.
Our technique has evolved since we first published on the arthroscopic Latarjet in 2007.4 It is important to note that this procedure should be reserved for surgeons with extensive arthroscopy expertise. We recommend becoming familiar with the anterior shoulder compartment, including the subcoracoid space when possible during routine arthroscopic procedures. Then, in a laboratory setting use a cadaver to perform the full procedure for the first time, and multiple times if possible. Finally, asking a local mentor to assist in the live setting can provide tips and troubleshooting assistance that is second to none.
THE ANTERIOR SHOULDER INSTABILITY LESION
“Anterior instability of the shoulder” is commonly used to include all symptoms of pathological anteroinferior displacement of the glenohumeral joint. However, with our expanded knowledge of the shoulder, it is critical to be more precise.
One must describe the direct correlation between the severity of the symptoms and the location of the lesion.
According the severity of the symptoms, 3 major groups of patients have been defined by the French Arthroscopic Society:
- Group I (56%): Dislocation (at least one full dislocation that needs a reduction by a person other than the patient)
- Group II (26%): Subluxation (shoulder never fully dislocates, but the patient has a sensation of shoulder instability confirmed by physical exam)
- Group III (18%): Unstable painful shoulder (the patient complains of shoulder pain and the surgeon determines the origin is an issue of instability such as labral detachment)
Further subdifferentiation includes the following:
Soft-tissue lesions range from a simple Bankart lesion to more complicated capsulolabral lesions like the anterior labroligamentous periosteal sleeve avulsion, complicated ruptures of the labrum (Detrisac II and IV), or humeral avulsion of HAGLs. In the most frequent cases of instability with dislocation (group I) concerning only soft tissues, the humeral displacement is anterior, medial, and inferior. The IGHL is always involved and most of the time, the soft tissue is badly damaged (ligament stretch or tear; humeral detachment: HAGL lesion). In addition to ligament damage, the labral ring is frequently torn, thus causing a loss of concentric forces of the intact ring that are critical to the healing process.
Associated bone lesions are created on both the humeral and glenoid side at the moment of the dislocation. These lesions are the Hill-Sachs lesion, at the level of the posterior humerus, and the Bankart/glenoid rim fractures with permanent loss of glenoid bone, which can further impair the remaining stability. Four of 5 patients who have anterior shoulder instability have a “bipolar lesion,” which is defined as having both a Hill-Sachs and glenoid bone lesion.6 Itoi described the contact zone between the glenoid and humeral head as the “glenoid track.” Based on the location of the Hill-Sachs lesion, it will either engage the glenoid and dislocate (off-track lesion) or avoid engagement and remain reduced (on-track lesion).6
WHY A CORACOID TRANSFER?
Operative Bankart repair, both open and arthroscopic, has demonstrated excellent results when used for isolated soft tissue Bankart lesions. However, in cases of unrecognized soft-tissue injury, for example, humeral avulsion of HAGL lesions, complex labral disruptions, irreparable soft-tissue damage, and in cases of bony deficiency, this technique may not be sufficient to stabilize the shoulder. For young patients (age < 20 years), overhead athletes, and those involved in contact sports, soft-tissue repair alone should be avoided.
In 2006, Boileau highlighted several reasons for failure of the Bankart procedure for anterior instability.1 The most important risk factors identified were bone loss on the glenoid or humeral sides and inferior ligament hyperlaxity. This is often a result of stretching from the initial dislocation. A combination of these abnormalities can result in up to a 75% recurrence of instability after soft-tissue repair.1,7
It seems clear that a simple Bankart repair, which reduces the labrum back on to the glenoid, cannot be expected to return soft-tissue stability to the shoulder when the HAGLs are torn or attenuated. Further to this point, where there is glenoid bone loss or an engaging Hill-Sachs lesion, a soft-tissue repair does not lengthen the glenoid articular arc, which is necessary to prevent future engagement and recurrent symptoms. In these situations another approach must be adopted.
The initial description of Bristow procedure was a simple translation into the subscapularis muscle of the conjoint tendon by sawing the bony chip of the distal part of the coracoid. The modified Bristow by Helfet8 uses a larger fragment of the coracoid tip which is fixed to the anterior glenoid neck with a single screw..
The Latarjet procedure is fixing half of the coracoid in a flat position using the advantage of congruence between the curvature of the anterior glenoid and the coracoid fragment. A larger-size bone block allows for double screw fixation with rotational stability and better compression as well as restoration of the area of glenoid bone loss. The ligamentoplasty effect is created by crossing the conjoint tendon over the inferior part of the subscapularis tendon, which is slightly reoriented in an inferior and posterior direction.4 This creates a dynamic tension applied to the inferior capsule and subscapularis especially in external rotation and therefore reinforces the anterior restraint. By augmenting the glenoid bony contour, engagement of a Hill-Sachs lesion is prevented. At present, the subscapularis muscle is split horizontally between the upper two-thirds and lower one-third and not superiorly detached with an L-like incision as described initially.
Autologous Bone and Iliac Crest Grafting
Alternatives such as autologous bone or iliac crest grafting have been routinely performed using open techniques with success and are indicated as a salvage surgery in cases of hardware failure, recurrent dislocation, or nonunion.
Isolated Transfer of the Conjoint Tendon
The isolated transfer of the conjoint tendon to the glenoid neck over the subscapularis tendon has been described to replace the sling of the torn HAGLs, but this does not address the inferior ligament weakness and/or glenoid bone loss.
The Latarjet or modified Bristow procedure are successful because they combine a bony procedure with a ligamentoplasty by the conjoint tendon transfer through the subscapularis muscle. Biomechanical studies from Itoi proved that bony reconstruction restores 100% of a native glenoid, and that association of bony reconstruction and conjoint tendon fixation provides 130% stability of a native shoulder. Capsule reconstruction on top of Latarjet does not affect the result.9
WHY AN ARTHROSCOPIC LATARJET?
Advantages over open Latarjet include the following:
- Placement of the bone graft is more accurate under arthroscopic control. Several views can be afforded by the arthroscopic technique that not only improve graft placement but will reduce the chances of overhang and impingement.
- Unlike open surgery, arthroscopic surgery allows for the treatment of concomitant pathologies such as superior labrum anterior and posterior tears and posterior labral lesions.
- Double instabilities can be treated during the same surgical procedure using both anterior and posterior bone blocks when employing arthroscopic methods. This is not possible through a single open approach.
- Even though the strength of the bone block fixation allows early mobilization, the risk of adhesions and shoulder stiffness is higher with an open technique over arthroscopy.
- If during an intended Bankart repair the tissue is determined to not be repairable, then an arthroscopic Latarjet offers an alternative solution to traditional open surgery and potentially having to reposition the patient.
- As in other joints, arthroscopy offers the advantages of less postoperative pain, earlier mobility, quicker rehabilitation, and faster return to sport.
- Improved cosmetic result for the patients with an arthroscopic technique.
Drawbacks of arthroscopic Latarjet include the following:
- There is a high level of difficulty during many steps of the procedure.
- There are risks linked to swelling.
- Potential malpositioning of the graft and of the screws may be caused by the difficulties of scapula positioning.
- There are neurologic and vascular risks.
- Arthroscopic Latarjet is not possible if operating conditions are not optimum, which is highly dependent on a perfect fit with the anesthesiology team.
It is important to keep in mind that conversion from arthroscopic to open Latarjet is possible at any stage.
INDICATIONS FOR ARTHROSCOPIC LATARJET
Once a detailed history, clinical examination and radiological investigations are performed, an intra operative assessment of the ligamentous stability can determine the appropriate operation. The following scenarios will provide examples of different surgical indications.
Glenoid Bone Loss
Many authors have reported failure of soft-tissue repair due to glenoid bone loss.10 The mechanical consequences of the anteroinferior glenoid erosion has been proven by biomechanics studies and assessed by different x-ray, computed tomography (CT) scan techniques, and arthroscopic visualization (inverted pear).11 In some cases, the bony fragment can be replaced and arthroscopically repaired by anchors and sutures. However, this is always smaller than the original glenoid and is not as strong and supportive as a bony block.
This is a common cause for recurrent instability and can manifest as a bony Bankart lesion or a true fracture of the anterior or inferior glenoid rim. Standard anteroposterior x-rays may show a fracture or a more subtle loss of contour of the anteroinferior glenoid rim. A decrease in the apparent density of the inferior glenoid line often signifies an erosion of the glenoid rim between 3 and 6 o’clock. An axillary view or better, a Bernageau view may show flattening of this area of the glenoid when bone loss has occurred.12 In summary, assessment of the degree of bone loss can be made through a variety of methods including plain radiographs, specific MRI sequences, CT scan with 3D volume rendering, arthroscopic assessment and measurement.13 CT reconstructions provide more robust static measurements than those afforded by the arthroscopic view. Arthroscopically, the distance from the glenoid rim as measured from the bare spot can assist the surgeon in identifying an inverted-pear glenoid, confirming substantial bone loss and the likely failure of an isolated soft-tissue repair. Even when the bony fragment is present, replacing it is not always sufficient to restore the bony glenoid articular arc because of the difficulties in the healing of this necrotic bone. In these cases a bone reconstruction as performed by the Latarjet procedure should be considered.
Humeral Bone Loss
The location and the depth of the Hill-Sachs lesion vary with each case: sometimes small and superficial, sometimes deep, extended, and exceptionally, double. Its location and depth is responsible for persistent instability, even in cases of well-done Bankart repair. Its precise assessment is difficult but can be approached by simple x-ray in internal rotation and 2-dimensional or 3-dimensional CT scan. Remplissage of the infraspinatus tendon has been described with satisfactory results but external rotation is limited and long-term results have not been reported.