Michael A. Rauh and Anthony Miniaci
DEFINITION
The glenohumeral joint is one of the most commonly dislocated joints in the body.
With anterior dislocations, bony defects of the anterior glenoid and posterosuperior aspect of the humeral head occur with relative frequency.
One of the first descriptions of the lesions found on the humeral head was by Flower4 in 1861, with many subsequent investigators reporting on these bony defects.13
In 1940, two radiologists, Hill and Sachs,6 reported that these defects were actually compression fractures produced when the posterolateral humeral head impinged against the anterior rim of the glenoid.
Since then, Hill-Sachs lesions have been found to occur with an incidence between 32% and 51% at the time of initial anterior glenohumeral dislocation.
In shoulders sustaining a Hill-Sachs lesion at the initial dislocation, there exists a statistically significant association with recurrent dislocation.7,8
Although Hill-Sachs lesions are common after anterior glenohumeral dislocations, there are relatively few publications describing specific treatments for these humeral head defects.14,19
In general, specific surgical procedures to address Hill-Sachs lesions have not been recommended in the initial surgical management of recurrent anterior dislocations because the majority of these lesions are small to moderate in size and do not routinely cause significant symptoms of instability.
Certain subsets of patients exist with more significant bony defects and ongoing symptoms of “instability” or painful clicking, catching, or popping. This occurs even after surgical procedures directed at treating their anterior instability.
ANATOMY
With an anterior shoulder dislocation, the humeral head is positioned anterior to the glenoid rim.
The posterosuperior aspect of the humeral head then impacts upon the anterior aspect of the glenoid rim and creates the Hill-Sachs lesion (FIG 1A).
Only after the shoulder joint is relocated can the influence of the size and shape of the Hill-Sachs lesion on overall shoulder stability be determined (FIG 1B,C).
Although there is not scientific proof, our clinical experience suggests that lesions representing 25% to 30% of the articulating surface arc of the humeral head often lead to symptoms.
PATHOGENESIS
The concept of “articular arc length mismatch” has been recently put forth by Burkhart to “explain the ongoing sensation of catching or popping” arising in the shoulder with a large HillSachs lesion alone or in combination with glenoid defects.”1,2
Patients with these symptoms have often undergone previous anterior stabilization procedures and reconstruction of damaged glenohumeral ligaments at that time.
This phenomenon, debatably referred to as “instability,” occurs mainly in a position of abduction and external rotation of the shoulder.
In this position, a large “engaging” Hill-Sachs lesion encounters the anterior glenoid rim, resulting in the rim “dropping into” the Hill-Sachs lesion.
The sudden loss of smooth articular surface on the humeral side of the joint presents an irregularly contoured area to the glenoid, causing an uneasy sensation in the patient that feels much like subluxation.
As Burkhart and DeBeer pointed out, for every “Hill-Sachs lesion, there is a position of the shoulder at which the humeral bone defect will engage the anterior glenoid.”
Clinically, it is important to differentiate between “engaging” and “nonengaging” Hill-Sachs lesions.1,2
An engaging Hill-Sachs lesion is one that presents the long axis of its defect parallel to the anterior glenoid with the shoulder in a functional position of abduction and external rotation, such that the Hill-Sachs lesion encounters the rim of the glenoid.
Lesions can be considered engaging even in positions that are considered “nonfunctional,” such as in some degree of extension, or in lesser degrees of abduction.
Apprehension and instability in lesser degrees of shoulder abduction often indicate a significant bony defect that is leading to the perceived instability.14
A nonengaging Hill-Sachs lesion is one that either fails to engage the glenoid or engages the glenoid only in a nonfunctional arm position. For example, the Hill-Sachs defect can pass diagonally across the anterior glenoid with external rotation; therefore, there is continual contact of the articulating surfaces and no engagement of the Hill-Sachs lesion by the anterior glenoid.14
Hence, when a patient has symptomatic anterior instability associated with an engaging Hill-Sachs lesion with an articular arc deficit, treatment must be directed at both repairing the Bankart lesion, if present, and preventing the Hill-Sachs lesion from engaging the anterior glenoid.
We believe that the treatment of symptomatic anterior glenohumeral instability, involving an engaging Hill-Sachs lesion with an articular arc deficit, can be accomplished satisfactorily with a technique of anatomic allograft reconstruction of the humeral head using a sideand size-matched humeral head osteoarticular allograft.
This technique involves an anatomic reconstruction that eliminates the structural pathology while maintaining the range of motion of the glenohumeral joint.
NATURAL HISTORY
One of the most clearly documented series of nonoperatively treated shoulder dislocations placed into immobilization is that of Hovelius and associates.8
FIG 1 • Posterior views of an anterior glenohumeral dislocation (A), an “engaging” Hill-Sachs lesion after relocation of the glenohumeral joint (B), and a humeral head with a large Hill-Sachs lesion (C).
They determined that the “type and duration of the initial treatment had no effect on the rate of recurrence; with a higher rate of recurrence the younger the patient.”
Overall, 52% of 247 primary anterior dislocations had no further dislocations.
Patients who were 12 to 22 years old had a 34% redislocation rate, while those who were 30 to 40 years had a rate of 9%.
Ninety-nine of 185 shoulders that were evaluated with radiographs had evidence of a Hill-Sachs lesion; and of these 99 shoulders, 60 redislocated at least once and 51 redislocated at least twice during the 10-year follow-up.
This compares with 38 (44%) of the 86 shoulders that did not have such a lesion documented (P 0.04).
Acute first-time shoulder dislocations have traditionally been treated nonoperatively with reduction followed by a form of immobilization.
Currently recommended types of immobilization after shoulder dislocations are as follows:
Simple sling immobilization with the arm in internal rotation11
Immobilization in external rotation9,10
No clear evidence has quieted this discussion.
PATIENT HISTORY AND PHYSICAL FINDINGS
All patients are initially evaluated with complete history and physical examination.
Specifics of the history include questioning for the mode of onset and timing of initial symptoms, and for the details of present symptoms, including pain, frequency, instability, and level of function.
All previous surgical procedures performed on the shoulder should be noted.
Most patients will give a history of recurrent dislocations or multiple surgical attempts to correct the instability.
Although thought to be a procedure for failed attempts at shoulder stabilization after dislocation, there are other situations that might lead the surgeon to consider this procedure initially.
Significant traumatic mechanism with an extensive HillSachs lesion (more than 25% to 30% of the articulating surface of the humeral head)
Patients with a history of grand mal seizures often have fairly large Hill-Sachs defects and significant apprehension about the use of their arm. Also, as a result of the violence of the dislocations, the amount of bone pathology present, and the inability to predict the onset of epileptic events, it is worth considering treating this group of patients with an allograft reconstruction of the humeral head defect at the index procedure, as soft tissue repairs alone may not be enough to prevent recurrent injury.
Physical examination should focus on inspection for previous scars, a thorough determination of active and passive range of motion, and evaluation of the integrity and strength of the rotator cuff.
The clinician should perform a detailed examination for glenohumeral laxity in the anterior, posterior, and inferior directions.
Examination for apprehension should be performed in multiple positions, as patients with large Hill-Sachs lesions usually exhibit apprehension that often occurs with the arm in significantly less than 90 degrees abduction and 90 degrees external rotation.13,14
A comprehensive examination should include but is not limited to:
Anterior apprehension test: Positive apprehension can be associated with anterior labral injuries.
Bony apprehension test: Apprehension with fewer degrees of abduction may indicate a significant and symptomatic bony contribution to the instability.
IMAGING AND OTHER DIAGNOSTIC STUDIES
Preoperative imaging includes a comprehensive plain film evaluation with anteroposterior (AP), true AP, axillary, and Stryker notch views of the involved shoulder (FIG 2A).
All patients require a preoperative axial imaging study (CT or MRI) to more fully define the bony architecture of the glenoid and humeral head and specifically the details of the HillSachs lesion (FIG 2B).
One must be careful when interpreting these studies, since the plane of the Hill-Sachs defect is oblique to the plane of the axial image. Therefore, the size of these defects is often underestimated in standard axial imaging.
Three-dimensional reconstruction can be a useful tool to more clearly define the size and location of the defect and to estimate the amount of the articular surface involved.
While the volume and depth of the lesion certainly affect the stability of the shoulder, even more important may be the size of the defect in the articular arc.
DIFFERENTIAL DIAGNOSIS
Anterior shoulder dislocation with or without.
Bankart lesion
“Bony Bankart” or an anterior glenoid lesion
Hill-Sachs lesion
Combination of the above
Posterior shoulder dislocation with or without associated soft tissue and bony lesions
Inferior shoulder dislocation with or without associated soft tissue and bony lesions
NONOPERATIVE MANAGEMENT
Given a mechanism of shoulder dislocation, the presence of significant bony defects to the glenoid or the humeral head, and associated functional instability, there are not anticipated gains through nonoperative management.
SURGICAL MANAGEMENT
Several techniques have been described in the literature to address symptomatic engaging Hill-Sachs lesions.
Open anterior procedures, such as an East–West plication to limit external rotation, designed to limit external rotation such that the humeral head defect is kept from engaging1,2
Rotational proximal humeral osteotomy as described by Weber and colleagues17
Transfer of the infraspinatus into the defect to render the lesion essentially extra-articular3,18
Filling in of the Hill-Sachs defect so that it can no longer engage, using either a corticocancellous iliac graft or a femoral head osteoarticular allograft
If the defect is severe, prosthetic replacement using a hemiarthroplasty may become necessary.16
In the case of posterior glenohumeral dislocation, Gerber and coworkers5 have reported on the successful reconstruction of the humeral head by elevation of the depressed cartilage and subchondral buttressing with cancellous bone graft, as well as femoral head osteoarticular allograft reconstruction of the humeral head defect.
The indications for anatomic allograft reconstruction of the humeral head are as follows:
Ongoing symptomatic anterior glenohumeral instability or painful clicking, catching, or popping in a patient with a large engaging Hill-Sachs lesion in patients who have failed to respond to previous soft-tissue stabilization procedures
A large engaging Hill-Sachs lesion is identified before undergoing initial surgical treatment. Clinical experience suggests that lesions involving more than 25% to 30% of the articular surface may be significant.14
FIG 2 • A. AP radiograph of shoulder demonstrating a large Hill-Sachs lesion. B. Axial MRI image demonstrating large engaging Hill-Sachs lesion.
Patients at high risk of redislocation (eg, epilepsy with recurrent anterior instability and large Hill-Sachs defects, or contact athletes with combined bony defects to the glenoid and humeral head) can consider this procedure as a primary treatment option.
Contact athletes can be considered in this group, as time lost from an activity can be a significant issue. Thus, treatment focused on all bony and soft tissue lesions might lessen the likelihood that they would sustain a failed procedure and the associated delay in returning to full competition.
Contraindications to this procedure include routine medical comorbidities precluding an elective surgical procedure with general anesthetic, existing infection, or presence of a nonengaging or functionally nonengaging Hill-Sachs lesion.
Preoperative Planning
A fresh-frozen cryopreserved osteoarticular humeral head allograft is obtained from a reputable, certified tissue bank.
It is important to obtain a sideand size-matched graft as this allows for an optimal recreation of the radius of curvature of the humeral head.
The details regarding treatment, preservation, and storage then differ depending on the type of sample and the preference of the surgeon.
The graft serves mainly a structural function, and cartilage viability is probably not essential for success.
The availability of fresh-frozen tissue can be problematic, and therefore we have sometimes performed the procedure using irradiated grafts.
In 2 of 20 cases using irradiated grafts, however, we observed partial collapse of the grafts, which required reoperation and screw removal. Fortunately, this did not lead to recurrent instability.
As a result, our present protocol favors the use of freshfrozen tissue.
Allograft sizing of the humeral head is performed by sending copies of your patient’s films to the chosen bone bank for measurement.
Plain radiographs can be used as long as they were obtained with magnification markers. Acceptable markers include some form of recognizable currency, such as a United States quarter or dime, or a standard magnification marker obtained from your tissue bank.
CT or MRI scan of the proximal humerus would allow for direct sizing from the scan since the magnification effect is factored into the resulting images.
Whichever way one chooses, the tissue bank should search for a match that has a side and size match to within about 2 mm. Clinically, we have found that this tolerance yields acceptable results for this procedure.
Specific details should be arranged between the surgeon and the tissue bank.
Nevertheless, availability of an allograft is sometimes a problem.
If waiting is not an option, one may choose to use nonmatched humeral grafts or femoral head allograft.
The problem with this is that femoral heads often have evidence of osteoarthritis and loss of articular cartilage. This is a suboptimal situation and should be avoided.
If different-sized grafts or femoral head grafts are used, they may not match the curvature of the native humeral head exactly and would need to be trimmed to obtain an optimal fit.
It is important to discuss and understand the details of allograft use as it may have direct implications to your patient.
Positioning
The patient is positioned in a modified beach chair position, inclined about 45 degrees, with the upper extremity draped free.
Approach
An extended deltopectoral approach is used.
The lateral border of the conjoined tendon is identified and gently retracted medially to expose the underlying subscapularis tendon.
TECHNIQUES
RELEASE OF THE SUBSCAPULARIS MUSCLE AND CAPSULOTOMY
The entire tendon is transected vertically about 0.5 cm medial to its insertion onto the lesser tuberosity.
Tag sutures of number 2 Control Release Ethibond Excel (#DC494, Ethicon, Somerville, NJ) are placed in the lateral aspect of the subscapularis tendon as it is released from the lesser tuberosity.
The interval between the subscapularis and the anterior capsule is then carefully developed using sharp dissection, continuing medially to the neck of the glenoid.
The inferior capsule is then further isolated using careful blunt dissection.
A laterally based capsulotomy is made with the vertical limb in line with the subscapularis incision and continuing superiorly.
The anteroinferior capsule is then released off the surgical neck of the humerus with intra-articular dissection using a periosteal elevator.
ANTERIOR LABRAL INSPECTION AND BANKART RECONSTRUCTION
A standard humeral head retractor is placed into the glenohumeral joint, allowing inspection of the glenoid and anteroinferior capsulolabral structures for any pathology.
If a Bankart lesion is found, it is repaired in the usual fashion using either bony drill holes or suture anchors. The sutures can be left untied until completion of the allograft reconstruction.
EXPOSURE OF THE HILL-SACHS LESION
The humeral head retractor is withdrawn and the humerus is brought into maximal external rotation to expose the Hill-Sachs lesion.
Unroof the synovial expansion of the supraspinatus to allow the humerus to be more fully externally rotated, allowing better visualization and access to the Hill-Sachs lesion.
A flat narrow retractor (eg, Darach) is then placed over the reflected undersurface of the subscapularis tendon and behind the neck of the humerus on the posterior rotator cuff in order to lever out the humeral head (TECH FIG 1).
TECH FIG 1 • Intraoperative exposure of large Hill-Sachs lesion to be reconstructed.
HUMERAL HEAD OSTEOTOMY
With the Hill-Sachs lesion adequately exposed, a microsagittal saw is used to smooth and reshape the defect into a chevron-type configuration.
The piece of matching allograft humeral head to be inserted should resemble a deep-dish slice of pie (TECH FIG 2A,B).
The base and side of the defect can then be further smoothed using a hand rasp to achieve precise, flat surfaces.
The base (X), height (Y), length (Z), and rough outside partial circumference (C) of the defect are then measured to the nearest millimeter (TECH FIG 2C).
TECH FIG 2 • A. Diagram of the humeral head after osteotomies. B. Reshaping of Hill-Sachs lesion to prepare to receive allograft. C. Schematic representation of required measurements of the defect and graft. Base (X), height (Y), length (Z), and rough outside partial circumference (C) of the defect are then measured to the nearest millimeter.
OSTEOTOMY OF THE HUMERAL HEAD ALLOGRAFT
A corresponding piece is cut from the matched humeral head allograft that is 2 to 3 mm larger in all dimensions than the measured defect.
The allograft segment is then provisionally placed into the Hill-Sachs defect and resized in all three planes.
Excess graft is then carefully trimmed with the micro-sagittal saw and is reshaped in the other two planes as well.
Fine-tuning of graft size is then continued in one plane at a time until a perfect size match is achieved in all planes, including base (X), height (Y), length (Z), and outside partial circumference (C).
FIXATION OF THE HUMERAL HEAD ALLOGRAFT
The allograft segment is placed into the defect and aligned so as to achieve a congruent articular surface.
It is provisionally secured in place with two or three smooth 0.045-inch Kirschner wires (TECH FIG 3A,B).
The wires are then sequentially replaced with 3.5-mm fully threaded cortical or 4.0-mm cancellous screws placed in a lag fashion (TECH FIG 3C,D).
Ensure that the screw heads are countersunk so that they are below the level of the articular surface.
The joint is irrigated and taken through a range of motion to ensure that the reconstructed humeral head provides a smooth congruent articulating surface.
TECH FIG 3 • A. Anatomic allograft reconstruction of Hill-Sachs defect with humeral allograft provisionally held in place with two Kirschner wires. B. Diagram of allograft reconstruction of Hill-Sachs defect with humeral allograft held in place with a Kirschner wire and an AO screw. C. AP radiograph of shoulder demonstrating anatomic allograft reconstruction of Hill-Sachs defect fixed with two countersunk cortical screws. (Dashed linerepresents the area filled by the allograft.) D. Axillary view of shoulder demonstrating anatomic allograft reconstruction of Hill-Sachs defect fixed with two countersunk cortical screws.
LABRAL REPAIR AND SUBSCAPULARIS REAPPROXIMATION
The capsulotomy is closed with absorbable suture, tying any previously placed sutures used to repair the capsulolabral pathology if present.
The subscapularis tendon is then reapproximated to its stump anatomically, without shortening, using suture anchors or a soft tissue repair with nonabsorbable suture.
Allow the conjoined tendon, deltoid, and pectoralis major muscles to return to their normal anatomic positions.
A routine subcutaneous and skin closure is then performed.
Sterile dressing is applied.
The arm is placed into a shoulder immobilizer.
POSTOPERATIVE CARE
After surgery, patients are given a sling for comfort and allowed full passive range of motion immediately as tolerated.
Because of the subscapularis detachment, we protect against active and resisted internal rotation for 6 weeks.
After the initial 6-week period, patients are allowed terminal stretching and strengthening exercises.
The shoulders are imaged with repeat radiographs at 6 weeks and 6 months, and with CT scans at 6 months to assess for consolidation and incorporation of the graft.
OUTCOMES
Between 1995 and 2001, we performed and reviewed this procedure in 18 patients who had failed previous attempts at surgical stabilization.13,14
Fifteen patients had a history of traumatic anterior glenohumeral instability related to sports, and three patients had instability related to seizures or other trauma.
All had posterolateral humeral head defects (Hill-Sachs lesions) that represented greater than about 25% to 30% of the humeral head.
One patient had both anterior and posterior humeral head defects from bidirectional shoulder instability sustained as a result of a seizure disorder.
No patients had true multidirectional instability.
Patients in the formal review were assessed preoperatively and postoperatively with:
Detailed history
Physical examination
Radiographic evaluation (plain films and axial imaging [CT, MRI, or both])
Validated clinical evaluation measures (Constant-Murley shoulder scale, Western Ontario Shoulder Instability Index [WOSII], and SF-36)
Findings at the time of surgery included.
Nine patients with recurrent Bankart lesions
Nine patients with capsular redundancy only
No patients with subscapularis tears
One patient with posterior glenoid erosion
Three patients with anterior glenoid deficiency (less than 20%), which was not reconstructed
Mean length of follow-up was 50 months (range 24 to 96 months).
There were no episodes of recurrent instability. Sixteen of 18 (89%) patients returned to work.
The average Constant-Murley score postoperatively was 78.5. The WOSII, which is a validated quality-of-life scale specific to shoulder instability using a visual analog scale response format, decreased and patients were significantly improved.
Overall, this represents the first reported series of anatomic allograft reconstruction of Hill-Sachs defects for recurrent traumatic anterior instability after failed repairs.
This technique has been shown to be effective for a difficult problem with few available treatment options.
The patients demonstrated improvement in stability, loss of apprehension, and high subjective approval, allowing return to near-normal function with no further episodes of instability.
Although infrequently a cause for clinical concern, HillSachs defects can be the source of significant disability and recurrent instability in a subset of patients.
One should consider anatomic allograft reconstruction of these defects as a viable treatment alternative.
COMPLICATIONS
Complications that occurred in our series of humeral osteoarticular allograft reconstruction of the Hill-Sachs lesions included radiographic follow-up evidence of partial graft collapse in 2 of 18 patients, early evidence of osteoarthritis in 3 patients (marginal osteophytes), and 1 mild subluxation (posterior).12–14
Hardware complications developed in two patients, who complained of pain with extreme external rotation.
The screws were removed at about 2 years postoperatively in both patients, thereby relieving their symptoms.
One must weigh the risks of continued shoulder dysfunction versus the risk associated with the use of fresh osteoarticular allografts.
REFERENCES
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