Keywords humeral fractures - joint instability - orthopedic procedures - shoulder dislocation
Palavras-chave fratura do úmero - instabilidade articular - luxação do ombro - procedimentos ortopédicos
Introduction
Although the Hill-Sachs (HS) lesion is widely known, the literature still debates
its contribution to the development of shoulder instability and its implications in
the surgical or conservative treatment of patients with this condition.
The first description of shoulder dislocation dates to ancient Egypt, around 3,000
BC, in the Edwin Smith papyrus. Malgaigne was the first author to mention a humeral
head lesion in 1855. In 1940, 2 radiologists, Harold Arthur Hill and Maurice David
Sachs, described and named the lesion.[1 ]
[2 ] The HS lesion is a depression of the humeral head in the posterolateral region in
the presence of an anterior shoulder dislocation. This compression fracture occurs
due to the impingement of the humeral head spongy bone against the anterior cortex
of the glenoid cavity.[3 ] The HS lesion is associated with bone or labral involvement on the anterior face
of the glenoid cavity and may contribute to shoulder instability.[4 ]
Current data indicate that shoulder dislocation mainly affects young and active populations,
generating concern about its socioeconomic implications.[5 ]
The incidence of HS lesions ranges from 40% to 90% in anterior shoulder dislocations
and reaches up to 100% in recurrent dislocations.[3 ]
[4 ]
[6 ] It is worth noting that an HS lesion rarely occurs in isolation, reinforcing the
concept of bipolar injury (that is, with scapular glenoid cavity involvement), which
is present in 63% of the cases.[7 ]
[8 ]
Arm positioning at the time of dislocation is relevant, since the location and inclination
of the resulting HS lesion affect shoulder stability. A dislocation occurring with
the shoulder in abduction presents a greater risk of engagement (HS lesion fitting
into the anterior glenoid rim).[9 ] More extensive HS lesions, especially in medial positions,[4 ] also increase the risk of instability due to reduced contact of the humeral head
with the articular surface of the glenoid cavity.
History and Clinical Picture
History and Clinical Picture
Patients with HS lesions typically complain of instability. They may present a history
of shoulder pain, which worsens in joint abduction or hyperextension,[3 ] or signs such as crepitation and clicking during movement. The potential for a new
dislocation increases with the number of episodes and the bone defect size. A positive
apprehension test with lower degrees of abduction (mid-range) presents a higher association
with glenoid cavity defects. In contrast, a positive result at the end of abduction
and lateral rotation (end range) results from HS lesions.[4 ]
To date, there is no description of a specific propaedeutic maneuver to evaluate HS
lesions. A routine physical examination should assess shoulder instability, including
an evaluation of generalized ligamentous laxity (Beighton criteria), and performance
of the sulcus, Gagey, apprehension, surprise, and relocation tests.[10 ]
Other tests include the hyperextension–internal rotation (HERI) test[11 ] and the bone apprehension test.[12 ] There is still controversy in the literature about the sensation of instability
in lower degrees of abduction (bone apprehension test) in detecting significant bone
loss in the glenoid cavity or humerus (HS).[12 ]
[13 ] It is crucial to confirm the finding of dislocation/instability on physical examination
under anesthesia.
Imaging Tests
The initial investigation routinely uses shoulder radiographs in classic anteroposterior
(AP), true AP, lateral, lateral scapular, and lateral axillary views ([Fig. 1 ]).
Fig. 1 Radiographs of the shoulder with a Hill-Sachs (HS) lesion in true anteroposterior
(AP), AP, axillary lateral, and scapular lateral views.
The specific radiographic investigation of the humeral bone defect from an HS lesion
can use the following radiographic views:[3 ]
Stryker notch: medial humeral head rotation to highlight the posterolateral defect.
Garth view: AP view of the shoulder in the scapular plane with a 45° caudal inclination
of the radius.
AP with medial rotation: this view can reveal the HS lesion size, depth, and orientation
in the posterolateral region of the humeral head.[14 ] Often, the AP radiographic view with lateral rotation does not show the lesion,
only a bone rarefaction medial to the greater tubercle[1 ]
[15 ] ([Fig. 2 ]).
Modified Didier: in this view, the patient is in ventral decubitus with the back of
the hand resting on the posterior iliac crest, the elbow in flexion, and the radius
at a 45° angle to the ground in the direction of the humeral head.[16 ]
Fig. 2 (A ) Anteroposterior radiograph with lateral rotation, not showing the HS lesion; (B ) AP radiograph with slight medial rotation, showing the HS lesion.
Radiographs have low interobserver reliability and cannot provide enough data for
preoperative planning,[17 ] since up to 60% of bone defects may be overlooked in cases using this method alone
for analysis.
Computed tomography (CT) and magnetic resonance imaging (MRI) are complementary imaging
methods ([Figs. 3 ]
[4 ]) that are more sensitive than radiographs in the detection of HS lesions.[14 ]
Fig. 3 Computed tomography (CT) scans showing the HS lesion. Two-dimensional images in the
axial, sagittal, and coronal sections. Three-dimensional images in the lateral and
posterior views.
Fig. 4 T2-weighted magnetic resonance imaging (MRI) scans showing the HS lesion the in coronal,
sagittal, and axial sections.
It has been proven that there are differences in defect measurements in two- and three-dimensional
(3D) images. Computed tomography with t3D reconstruction (3D-CT) is the gold standard
to quantify the HS defect.[7 ]
[17 ] The measurements are made in slices perpendicular to the bone defect, but they can
vary.[18 ]
[19 ]
Three-dimensional CT defines the HS lesion angulation per the line passing deep to
the injury dent and the longitudinal axis of the humeral diaphysis ([Fig. 5 ]).[17 ] The higher the angulation, the greater the risk of engagement.
Fig. 5 (A ) The smaller angle presents a lower engagement risk. (B ) A larger angle presents a higher engagement risk. We considered that the HS lesion
was the same size in A and B .
The use of MRI with 3D reconstruction (3D-MRI) is growing. Studies[20 ]
[21 ] have reported equivalent accuracy in measuring the defect of the HS lesion with
3D-CT and 3D-MRI. Three-dimensional MRI presents the advantage of not using ionizing
radiation, and it has better diagnostic potential for soft tissue injuries, such as
in the evaluation of rotator cuff attachment. In 3D-CT, this evaluation can result
in high variability and low interobserver agreement due to the difficulty in visualizing
this structure. The disadvantages of the reconstruction methods include their high
costs and limited accessibility. It is worth highlighting that measuring the size
of the HS lesion with two-dimensional CT or MRI increases the likelihood of obtaining
an overestimated measurement (diagonally), which increases the chance of classifying
the lesion as off-track and may influence the choice of the surgical technique ([Fig. 6 ]).
Fig. 6 Magnetic resonance imaging scan evaluated in the axial section (black arrow); three-dimensional
CT scan evaluated perpendicularly to the defect (blue arrow). Note that the black
arrow is larger than the blue arrow, which may overestimate the defect and change
the case management.
Differential Diagnoses
It is easier to diagnose HS lesions by associating the patient's clinical history
with imaging tests. However, it is critical to remember that some conditions can cause
bone erosions in the humeral head, simulating HS lesions, such as ankylosing spondylitis,
rheumatoid arthritis, septic arthritis, hyperparathyroidism, hydroxyapatite storage
disease, malignant tumor, or benign cysts.[14 ]
Classification
The classification of HS lesions can follow the arthroscopic visualization criteria
described by Calandra,[7 ] which rely on quantifying the defect depth. A grade-1 lesion affects the articular
cartilage alone; a grade-2 lesion extends to the subchondral bone; and a grade-3 lesion
presents a sizable subchondral defect.[16 ] However, its clinical applicability is limited.
One of the most crucial concepts in HS lesions is the glenoid track (GT), that is,
the area of contact between the glenoid cavity and the humeral head during movement
from the neutral position to the abduction and external rotation (ABER) position.[20 ] In this movement, the area of contact moves from inferomedial to superolateral in
the humeral head ([Fig. 7 ]). Cadaveric studies have shown that the area covered by the glenoid cavity corresponds
to 84%, while clinical studies indicate an 83% of coverage.[19 ]
Fig. 7 The arrow indicates the change in the contact region of the humerus with the glenoid
cavity rim in the resting position to the abduction and external rotation (ABER) position.
We can use the contralateral side of the glenoid cavity to assess the size of the
bone defect; however, this assessment must be careful, as 8% of glenoid cavities present
a difference ≥ 3 mm regarding the contralateral side.
The Di Giacomo et al.[9 ] method for GT measuring includes four steps:
Measurement of the diameter of the inferior glenoid cavity using a perfect circle
(D);
Measurement of the anterior bone loss of the glenoid cavity (d);
Calculation of the GT width = (0.83 × D) − d;
Measurement of the width of the HS interval (HSI) = width of the HS + width of the
bone bridge (BB).
If HSI > GT, the HS lesion is off-track, that is, with a risk of engagement.
If GT > HSI, the HS lesion is on track, that is, with no risk of engagement[17 ] ([Fig. 8 ]).
Fig. 8 (A ) On-track lesion (Hill-Sachs interval [HSI] lesion < glenoid track [GT]); (B ) off-track lesion (HSI > GT).
Although the use of this method is frequent in the clinical practice, its intra- and
interobserver agreements are low, mainly due to the difficulty in defining the medial
margin of the HS lesion, the correct rotator cuff attachment on CT, and the overlap
of the lateral edge of the HS lesion on the medial edge of the rotator cuff attachment.[18 ]
[19 ] Another criticism to the GT method is that it does not consider joint mobility,
especially in subjects with ligamentous laxity, which may result in higher humeral
head excursion.[21 ]
Another imaging classification relies on the location of the HS defect, which was
developed from the observation that even some on-track lesions submitted to the Bankart
surgery alone evolved with failure. This classification divides the humeral head GT
into four zones, and HS lesions reaching the most medial peripheral zone (peripheral
track) presented[19 ] worse results in the Western Ontario Shoulder Instability Index (WOSI) score when
compared with other zones (central track) ([Fig. 9 ]).
Fig. 9 (A ) Central track (0 %to 75% of the GT); (B ) Peripheral track (75–100% of GT).
Other measurement methods are under development to reduce failures in on-track lesions
treated with labral repair alone. The distance to dislocation (DTD)[22 ] considers the inferior craniocaudal extension of the HS lesion.[5 ] Another method is the global track,[21 ] which uses the dome of the humeral head and its central point as a reference instead
of the rotator cuff attachment to measure the HS defect. However, these methods still
require validation and testing in the clinical practice.
Treatment
The treatment of anterior shoulder instability, which is frequently associated with
HS lesions, can be conservative in the first dislocation episode in patients with
low demand. This treatment strengthens the deltoid, rotator cuff, and scapular stabilizer
muscles. It is important to be aware of risk factors for recurrence, such as age (under
20 to 25 years), male sex, epilepsy, fall risk, ligament laxity, and participation
in activities requiring ABER or competitive sports.[7 ]
[23 ]
[24 ]
In cases with surgical indication, HS lesion treatment is not usually performed in
isolation, since the labral or ligament complex lesion is virtually always present,
and its association with the bone defect of the glenoid cavity (bipolar lesion) occurs
in 63% of the cases.[7 ]
The presence of the HS lesion is essential for therapeutic decision-making, as its
size, location, and inclination influence the treatment. Some authors[7 ]
[25 ] argue that patients with small bone defects (< 20% of the humeral head) or no engagement
can undergo isolated labral repair. Cases of larger defects or engagement may require
other procedures. As some cases of failure occur even in the absence of engagement,
there is a growing tendency to address the HS lesion in patients with anterior instability,
even in situations with borderline bone lesions, especially with the remplissage technique.[21 ]
[22 ]
[26 ]
Humeral Head Procedures
The remplissage technique was described in 1972 and comes from the French word for
“filling”. Wolf modified it to perform it arthroscopically, “filling” the HS lesion
by capsulodesis and infraspinatus tenodesis with labral repair. The prevalence of
off-track lesions is of approximately 7%.[27 ] The ability to convert the HS lesion from intra-articular to extra-articular, reducing
the engagement with the inferior edge of the glenoid cavity and the recurrent subluxation
rate, determines the success of this technique. Even though the current recurrence
rate ranges from 0% to 10%,[28 ]
[29 ] the size of the bone defect in the glenoid cavity influences these values.
The advantage of this procedure is its minimally-invasive approach, avoiding the need
for bone block surgeries in the glenoid cavity and its complications. The theoretical
disadvantage of this technique is the alteration of the rotator cuff anatomy and the
shoulder biomechanics, potentially reducing lateral rotation and causing pain in the
posterosuperior region of the shoulder.[30 ] However, this is a controversial topic, with some studies demonstrating no difference
in these outcomes compared with the isolated labral repair technique, especially with
the technical development and studies on the ideal location for anchor insertion.
Other options for HS lesion treatment include two procedures: humeroplasty (for acute
defects) and osteochondral bone grafting.
Humeroplasty (elevation of the impinged fracture and support with a graft) restores
the geometry of the humeral head with no internal fixation. It is indicated for acute
injuries of up to 3 weeks presenting less than 40% articular surface involvement.[3 ]
This method consists of elevating the cartilage and filling the defect with calcium
phosphate,[31 ] restoring the local anatomy with a 5° gain in lateral rotation. Another way to elevate
the defect uses a percutaneous vertebroplasty balloon with potential videoarthroscopy
assistance,[32 ]
[33 ] with report demonstrating a 99.3% reduction in HS lesion bone defect.[7 ]
Partial arthroplasty using allograft fills the defect with an osteochondral graft
via an open or arthroscopic approach. Allografts provide better biomechanics restoration,
unlike non-anatomical grafts. The potential disadvantages include disease transmission,
procedural difficulty, graft reabsorption or failure, subluxation, and cyst formation.[7 ] In addition, differences in the size and geometry of the defect and the implant
may require humeral cartilage milling.
Glenoid Cavity Procedures
Glenoid Cavity Procedures
The treatment of glenoid cavity injuries depends on the size of the bone defect. Currently,
Bankart repair alone has limited indications. The literature[34 ] has shown an increasingly guarded prognosis regarding critical bone loss for the
performance of the Bankart repair. Adding remplissage to the Bankart repair may reduce
the number of surgical treatment failures.[23 ]
[35 ]
Bone procedures increase the surface area of the glenoid cavity and indirectly treat
potential failures resulting from the HS lesion. The most widespread techniques are
the Latarjet procedure, the Eden-Hybinette technique, and the tibial allograft.
The potential disadvantages of the bone graft techniques in the glenoid cavity are
loss of lateral rotation (on average, 11°), infection, hematoma, graft resorption,
pseudoarthrosis or fibrous union, and subscapularis injury.[23 ]
[30 ]
Arthroplasties
Partial resurfacing prostheses present the advantages of no donor site morbidity compared
with autografts and shorter surgical time. The disadvantages are the difficulty in
obtaining proper fixation and the inability to align the prosthesis surface with the
humeral articular surface.[36 ]
Another option is hemiarthroplasty, a procedure indicated for elderly patients with
an HS defect > 40% of the articular surface. An increase of 10° to 15° in retroversion
may improve stability.[7 ]
[25 ]
Other arthroplasty types are uncommon and intended for more severe instability or
complications from previous procedures.
Options with a Historical Interest
Options with a Historical Interest
Weber's derotation osteotomy is a treatment option still in use as a salvage procedure
in young patients. This technique consists of an osteotomy on the surgical neck of
the humerus and a retroversion of the humeral head in relation to the diaphysis. This
procedure presents variable outcomes and relatively high complication rates, such
as pseudarthrosis, iatrogenic fracture, and osteoarthritis.[7 ]
Final Considerations
The HS lesion plays a fundamental role in shoulder instability, and research on this
topic has exponentially increased in recent times.
The search for an algorithm for decision-making on the best treatment for patients
with anterior shoulder instability continues. However, despite all attempts and concepts
developed to date, there is no ideal option.
Therefore, it is essential to consider HS lesions and their correct treatment to improve
outcomes and achieve high success rates, with no dislocation recurrence and excellent
function according to patients' expectations. We expect that the evolution we are
witnessing will bring long-term better functional outcomes and fewer complications
to these patients who, as already discussed, are mostly young, active people, with
high expectations.
Bibliographical Record
