Posterior Approach to Humeral Head for Allograft Reconstruction of Hill-Sachs Lesions

Abstract

Background:

Anterior glenohumeral instability is common in athletes and is often associated with an impaction fracture of the posterolateral humeral head, known as a Hill-Sachs lesion. As humeral bone loss increases, these lesions become more likely to engage anteriorly and require surgical intervention. With greater degrees of anterior glenoid bone loss, smaller Hill-Sachs lesions can be more clinically relevant, which can necessitate treatment of the posterior humerus in addition to addressing the anterior glenoid.

Indications:

Traditional anterior open approaches to Hill-Sachs lesions require detaching the subscapularis and dislocating the shoulder for access, which compromises anterior shoulder stabilizers and is limited by arthroscopy.

Technique Description:

This open posterior approach to the humeral head was previously described with a modified deltoid split. Beginning 1.5 cm medial and inferior to the posterolateral acromion, a 5-cm incision is made in line with the posterior deltoid fibers. Electrocautery is used to maintain hemostasis, and the deltoid fascia is split, carefully avoiding the axillary nerve and posterior humeral circumflex artery. Exposure of the infraspinatus and teres minor fascia is obtained with retractors. The fascia is split in line with the interval between the infraspinatus and teres minor, and the tissue plane between the posterior rotator cuff and posterior capsule is bluntly developed. Exposure of the capsule is obtained with placement of another retractor between the 2 muscles. The Hill-Sachs lesion is palpated, and a vertical capsulotomy overlying the defect is performed to visualize the lesion in preparation for humeral head allograft reconstruction.

Results:

An open posterior approach to the humerus allows for complete visualization of the Hill-Sachs lesion, facilitating allograft reconstruction while preserving the subscapularis anteriorly and without the need for surgical dislocation of the shoulder.

Discussion/Conclusion:

A previous study has demonstrated that the described approach exposes 100% of the Hill-Sachs lesion, with the benefits of subscapularis preservation, elimination of the need for shoulder dislocation or extreme external rotation, and a perpendicular approach for instrumenting the defect. The humeral head blood supply is also preserved, with no interaction anteriorly with the anterior humeral circumflex artery, and the posterior humeral circumflex artery is kept out of the dissection field.

Patient Consent Disclosure Statement:

The author(s) attests that consent has been obtained from any patient(s) appearing in this publication. If the individual may be identifiable, the author(s) has included a statement of release or other written form of approval from the patient(s) with this submission for publication.

Graphical Abstract

This is a visual representation of the abstract.

Video Transcript

My name is Katherine Kutzer, and along with Dr. Olivia O’Reilly, Julia Ralph, Dr. Jonathan Dickens, and Dr. Brian Lau, we will present a technique for a posterior approach to the humeral head for allograft reconstruction of Hill-Sachs lesions.

These are our disclosures.

Background

Anterior glenohumeral instability is common in young athletes.^2,13 The Hill-Sachs lesion is an impaction fracture of the posterolateral humeral head, which is caused by the forceful contact of the humeral head on the anterior glenoid as the humerus relocates into the glenohumeral joint.^8,12 The incidence of Hill-Sachs lesions in those with anterior shoulder instability has been estimated as high as 90%, with some estimations approaching 100% in patients who dislocate more than once. ¹²

Indications

While these lesions are common, the literature can be inconsistent in describing defect size and glenoid engagement, the 2 most common variables for determining clinical significance. Yamamoto et al ¹⁷ popularized the “glenoid track” concept, detailing the effect of both glenoid and humeral bone loss on anterior shoulder instability. As humeral bone loss increases, these lesions become more likely to engage anteriorly and require surgical intervention. With greater degrees of anterior glenoid bone loss, smaller Hill-Sachs lesions can be more clinically relevant, which can necessitate treatment of the posterior humerus in addition to addressing the anterior glenoid. Allograft augmentation of the humeral head, commonly with a wedge graft, has previously been indicated for rare isolated Hill-Sachs injuries without anterior glenoid bone loss, with outcomes limited to case reports and small cohorts. ⁴ However, with the effect of larger anterior glenoid defects on the clinical relevance of posterior humeral defects, it stands to reason that allograft augmentation of the humeral head may be viable as part of a proposed surgical treatment for those with bipolar lesions or for those with greater than 30% humeral bone loss. ³

This is a 22-year-old man who originally presented with chronic left anterior shoulder instability. His first instability event occurred in high school while playing baseball. He underwent arthroscopic Bankart repair at the time and initially did well for 18 months before he had a recurrent instability episode during a low-energy event playing recreational sports. He went on to have multiple instability events over the next 3 years, with increasing frequency and lower energy.

Physical examination was pertinent for tenderness to palpation at the posterior joint line, pain at terminal external rotation, positive anterior apprehension with relocation and at mid-range, and a 3+ anterior load and shift.

Radiographs of the left shoulder demonstrated blunting of the subchondral bone of the anterior glenoid, as well as a large Hill-Sachs lesion posteriorly.

Magnetic resonance imaging (MRI) of the shoulder better demonstrates the large Hill-Sachs lesion, measuring 27.5 mm across at its widest portion.

Three-dimensional computed tomography (3D CT) reconstruction better delineates the extent of the anterior glenoid bone loss.

There is no universally accepted technique.^10,11 In this patient, utilizing diameter-based measurement, humeral bone loss was measured at 26.4%, and glenoid bone loss was measured at 22.1%.

The glenoid track was evaluated on MRI and 3D CT. The Hill-Sachs interval either closely approached or exceeded the glenoid track, lending concern for an off-track engaging lesion. ⁹

The main considerations for osteochondral allograft were the broad nature of the Hill-Sachs lesion and its engagement with the glenoid. Considering these along with the extent of glenoid bone loss and patient goals, the patient was indicated for right shoulder arthroscopic distal tibial allograft augmentation of the glenoid and open posterior humerus osteochondral allograft transplantation. The anterior stabilization portion of the procedure was performed arthroscopically, as described by Wong and Urquhart. ¹⁶ The open portion of the procedure was performed using a modified open posterior approach to the humeral head with press-fit allograft plugs, a technique that will be described as follows.

Technique Description

The patient is placed in the beach-chair position, with the arm positioned in a proprietary arm holder, placed on a padded Mayo stand, or left free. The arthroscopic portion of the procedure is performed first, with the posterior portal slightly lateral to allow access to the joint and the Hill-Sachs lesion through the eventual open approach.

A 5-cm vertical incision is planned, beginning approximately 2 cm distal to the posterolateral border of the acromion, extending distally and slightly laterally in line with the deltoid fibers. Sharp dissection is carried through the skin, and hemostasis is obtained. The dissection is carried down to the level of the deltoid fascia. Full-thickness flaps are created medially and laterally in the layer above the deltoid fascia, and a self-retaining retractor is placed.

The deltoid fascia is split in line with its underlying muscle fibers. Care is taken to extend the fascial split proximally and to avoid distal dissection to prevent the approach from extending toward the quadrangular space. The posterior muscular raphe is identified, and the deltoid muscle fibers are split. This exposes the underlying subdeltoid bursa, which lies atop the deep fascia. The self-retaining retractor is placed for optimal visualization, and any subdeltoid bursal tissue is removed, revealing the underlying infraspinatus and teres minor muscle bellies. Moving the self-retaining retractor deeper into the deltoid split clearly demonstrates the intervening muscle fascia separating the more superior muscle belly of the infraspinatus and the more inferior muscle belly of the teres minor.

Here we can see intraoperative depictions of this deeper interval and the clear delineation between the muscle bellies of the infraspinatus and teres minor. Care is taken to restrict the remaining dissection to the plane between the infraspinatus and teres minor.

The overlying deep fascia sits upon the 2 muscle bellies of the deep interval. The deep fascia is incised horizontally. The plane between the superior infraspinatus and inferior teres minor is bluntly developed, with care to remain in line with the muscle fibers. Any adhesions between the 2 muscles are eliminated, and to aid in the development of the interval, the infraspinatus is retracted superiorly. The capsule lies at the base of the interval. To achieve excellent visualization of the posterior capsule, and another self-retaining retractor is placed.

Intraoperatively, you can see the exposure to the posterior capsule obtained by the approach. The visualization is maintained with the use of self-retaining retractors, allowing for hands-free exposure.

The posterior capsule is intact overlying the glenohumeral joint. We can see the approach has taken us to the posterior aspect of the humeral head, and the posterior glenoid is palpated in the medial extent of the exposure. The Hill-Sachs lesion can be palpated to identify the appropriate location for capsulotomy. A vertical incision is made full-thickness through the capsule centered over the Hill-Sachs defect, with care to develop medial and lateral leaflets for later closure. The posterior aspect of the humeral head is exposed, and the articular margin is centered in the capsulotomy. The infraspinatus muscle belly can be further retracted proximally for exposure of the superior aspect of the posterior humeral head. The capsulotomy can also be extended as needed for increased exposure. For some patients, the depth of the approach may necessitate a supplementary light source for maximal visualization.

Intraoperatively, we can see that the vertical capsulotomy exposes the Hill-Sachs lesion and its extension into the articular surface medially.

A deep retractor can be placed in the capsulotomy, and the humerus can be manipulated for exposure. Care is taken to avoid aggressive abduction and external rotation, but these positions are not required to access the Hill-Sachs lesion. Humeral head allograft augmentation may proceed with any number of techniques, including circular plugs, ellipsoid plugs, or wedge shapes, depending on the size and shape of the Hill-Sachs lesion.

Intraoperatively, the use of dual self-retaining retractors and a K-wire shows the entirety of the Hill-Sachs lesion. Here, we can see the more than adequate exposure to proceed with humeral head allograft augmentation. This patient underwent augmentation with circular allograft plugs in a stacked “snowman” configuration. The lesion is sized with a dowel correlating to the diameter of the planned allograft plug. A pin is drilled through the center of the sizing dowel. The pin is overdrilled with the circular reamer to a depth of at least 10 mm. The depth of the drilled lesion is measured in the 12-, 3-, 6-, and 9-o’clock positions. A dilator is placed in the recipient site while the graft is prepared on the back table. The allograft plug is drilled with the circular saw using the same diameter as the reamed recipient site. The plug is sized and gently impacted into place.

After intra-articular procedures are complete, the posterior capsule is reapproximated with braided absorbable suture, with care not to overtighten the repair. The deep interval does not require closure. The superficial deltoid fascia can be reapproximated with suture. Skin closure can proceed per surgeon preference.

Results

Postoperatively, patients are kept nonweightbearing to the operative extremity in a sling with an abduction pillow but are allowed to begin gentle pendulum motions and passive range of motion forward flexion and external rotation exercises with therapist or cane assistance. Range of motion and therapy activities may be limited by the concomitant anterior stabilization procedure. This approach leaves the subscapularis intact anteriorly; therefore, rehabilitation exercises do not rely on protecting a subscapularis repair.

Recommendations on returning to sport are often dictated by the concomitant anterior stabilization procedure. The study institution utilizes multifaceted functional testing to help guide the postoperative rehabilitation process. First-time functional testing is recommended at 4 months postoperatively, with anticipated full return to sport projected 6 to 9 months postoperatively.

Discussion/Conclusion

There are multiple advantages to this modified approach in the setting of isolated humeral head grafting and emerging arthroscopic anterior stabilization techniques. The subscapularis and anterior capsule are preserved, leaving anterior shoulder stabilizers intact. The blood supply of the humeral head is also preserved, with no concern for disruption of the anterior or posterior humeral circumflex arteries. The approach does not require manual dislocation of the humerus from the glenohumeral joint, and the humerus can be gently maneuvered to expose the Hill-Sachs lesion without forceful disruption of the joint. The entirety of the Hill-Sachs defect can be visualized with a perpendicular angle of approach to instrumenting the lesion, compared to a parallel or oblique angle of instrumentation in anterior open approaches. The drawbacks of the technique include a second incision and approach when addressing concomitant anterior pathology arthroscopically. The technique is less familiar than other commonly utilized approaches, and surgeons may feel more comfortable with a utilitarian deltopectoral approach. The main complications from the authors’ experiences are early stiffness and a small amount of reduced external rotation.

There are multiple approaches employed in practice to address the Hill-Sachs lesion; considerations for each of these are listed here.

There are few described posterior approaches to the glenohumeral joint in the existing literature.^7,15 The current technique described was originally described by Bond et al ¹ in the Orthopaedic Journal of Sports Medicine in 2024. Further study is needed into patient outcomes and return to play after this approach.

There are multiple options to address Hill-Sachs lesions.^5,6,13,14,18 Remplissage fills the lesion while also acting as a tether for the humeral head, but some studies relay concerns of loss of external rotation, particularly for large lesions engaging with the glenoid. ¹⁰ Osteochondral allografts can be crafted in multiple ways, including circular plugs, wedges, and ellipsoid shapes. Circular plugs and ellipsoids benefit from press-fit fixation, while larger wedge shapes may require screw fixation. This may result in wear, cyst formation, or subsequent need for hardware removal. Multiple allograft sources can be utilized, including the humeral head, femoral head, and talar dome, with care taken to attempt to match the radius of curvature of the native humeral head. Partial humeral head resurfacing replaces the defect with a metal circular implant, which avoids the complications of allograft but introduces those that accompany hardware placement.

Our references can be seen here. We thank you for your attention to this video technique.