Mechanism and patterns of bone loss in patients with anterior shoulder dislocation

Treatment of Shoulder Cartilage Defects in Athletes

Articular cartilage defects in the glenohumeral joint may be found in laborers, the elderly, and young athletes, among others. Various factors can contribute to cartilage damage, including prior surgery, trauma, avascular necrosis, inflammatory arthritis, joint instability, and osteoarthritis. There is a wide variety of treatment options, from conservative treatment, injections, and surgical options, including arthroscopic debridement, microfracture, osteochondral autograft transfer, osteochondral graft transplantation, autologous chondrocyte implantation, and the newly emerging techniques such as biologic augmentation. There is a challenge to determine the optimal treatment options, especially for young athletes, due to limited outcomes in the literature. However, there are many options which are viable to address osteochondral defects of the glenohumeral joint.

Location and size of the reverse Hill-Sachs lesion in patients with traumatic posterior shoulder instability

BACKGROUND

In patients with traumatic posterior shoulder instability, little is known about the precise location and size of the reverse Hill-Sachs lesion.

METHODS

Forty-nine shoulders of 47 patients with traumatic posterior instability were included in this study based on the following inclusion criteria: (1) a primary or recurrent traumatic posterior shoulder dislocation and (2) the initial event being caused by trauma. Patients were excluded if they had (1) no history of trauma, (2) prior shoulder surgery, (3) no computed tomographic (CT) examination, or (4) were seizure cases. Three-dimensional images of the humerus reconstructed from CT images were reviewed using an image analysis software. The location and size of the reverse Hill-Sachs lesion were measured and described on a clock face on the humeral head.

RESULTS

The reverse Hill-Sachs lesion was observed in 25 of 49 shoulders (51%). The reverse Hill-Sachs lesions were located between 1:37 and 2:48. The depth of the reverse Hill-Sachs lesion (mean ± standard deviation) was 5.8 ± 2.2 mm. The extent of the reverse Hill-Sachs lesion was 35° ± 12°. The average orientation of the reverse Hill-Sachs lesion, represented by an angle measured from the 12 o'clock position, was 64° ± 12° and pointing toward 2:09 on a clock face. The mean length and width of reverse Hill-Sachs lesions were 9.7 ± 4.7 mm and 11.1 ± 3.6 mm, respectively.

CONCLUSION

The reverse Hill-Sachs lesion was a semicircular compression fracture located on the anteromedial aspect of the humeral head. Compared with shoulders with anterior shoulder instability, the humeral defect was smaller and located more inferiorly in shoulders with posterior instability.

The size of the Hill Sachs defect increases during reduction of a first time shoulder dislocation in older adults: a pilot study in 20 cases

PURPOSE

To evaluate if the size of Humeral Hill-Sachs Defects (HSDs) increases during reduction in the emergency department (ED) in subjects that have a first-time anterior shoulder dislocation.

METHODS

Subjects more than 18 years old presenting to the ED a first-time anterior shoulder dislocation were included. A computed tomography was performed prior to any reduction attempt (Pre-CT). The shoulder was reduced in the emergency room with intraarticular lidocaine; if two attempts failed, the shoulder was reduced under anaesthesia. A second CT was performed after reduction of the shoulder (Post-CT). CT were evaluated using the Osirix software. A 3-dimensional reconstruction of the humeral head was performed and the maximum width of the humeral defect, maximum depth of the humeral defect and total volume of the humeral defect were measured. The relative increase in size was calculated.

RESULTS

Twenty subjects were included in the study. All subjects presented HSDs in the Pre-CT that had a width of a median of 9.9(interquartile range:2.9)mm, a depth of 7.0(3.0]mm and a volume of 355(333)mm2. The HSD in the Post-CT had a width of 10.9(3.0)mm (an increase of 7.23[8.5]%, significant differences, p = 0.0001) a depth of 7.2(2.7)mm (an increase of 9.93[20.7]%, significant differences, p < 0.0001) and a volume of 469(271) mm2 (an increase of 27.5[26.9]%, significant differences, p < 0.0001). There were size increases larger than 25% in 15/20 (75%) of subjects.

CONCLUSION

Standard reduction manoeuvres performed in a first-time anterior shoulder dislocation increase the size of the HSD. This increase in size is larger than 25% in four out of five cases.

LEVEL OF EVIDENCE

IV, prospective cases series study.

Native Glenoid Depth and Hill-Sachs Lesion Morphology in Traumatic Anterior Shoulder Instability

BACKGROUND

Although Hill-Sachs lesions (HSLs) are assumed to be influenced by glenoid characteristics in the context of bipolar bone loss, little is known about how glenoid concavity influences HSL morphology.

PURPOSE

To investigate the relationship between the native glenoid depth and HSL morphological characteristics.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

Computed tomography images of bilateral shoulders from 151 consecutive patients with traumatic unilateral anterior shoulder instability were retrospectively reviewed. Patients were categorized into flat (<1 mm), moderate (1-2 mm), and deep (>2 mm) groups based on the native glenoid depth measured from the contralateral unaffected shoulder. The HSL morphological characteristics included size (depth, width, length, and volume), location (medial, superior, and inferior extent), and orientation (rim and center angle). The glenoid characteristics included diameter, depth, version, and bone loss. The patient, glenoid, and HSL morphological characteristics were compared among the 3 depth groups. Subsequently, the independent predictors of some critical HSL morphological characteristics were determined using multivariate stepwise regression.

RESULTS

After exclusion of 55 patients, a total of 96 patients were enrolled and classified into the flat group (n = 31), moderate group (n = 35), and deep group (n = 30). Compared with those in the flat group, patients in the deep group were more likely to have dislocation (38.7% vs 93.3%; P = .009) at the primary instability and had a significantly larger number of dislocations (1.1 ± 1.0 vs 2.2 ± 1.8; P = .010); moreover, patients in the deep group had significantly deeper, wider, larger volume, more medialized HSLs and higher incidences of off-track HSLs (all P≤ .025). No significant differences were detected among the 3 groups in HSL length, vertical position, and orientation (all P≥ .064). After adjustment for various radiological and patient factors in the multivariate regression model, native glenoid depth remained the strongest independent predictor for HSL depth (β = 0.346; P < .001), width (β = 0.262; P = .009), volume (β = 0.331; P = .001), and medialization (β = -0.297; P = .003).

CONCLUSION

The current study sheds light on the association between native glenoid depth and the morphology of HSLs in traumatic anterior shoulder instability. Native glenoid depth was independently and positively associated with HSL depth, width, volume, and medialization. Patients with deeper native glenoids were more likely to have off-track HSLs and thus require more attention in the process of diagnosis and treatment.

How much force is acting on the shoulder joint to create a Hill-Sachs Lesion or reverse Hill-Sachs Lesion?

BACKGROUND

It has not been clarified yet how much force is acting on the shoulder joint to create Hill-Sachs/reverse Hill-Sachs lesions which are commonly observed in patients with anterior or posterior shoulder instability. The purpose of this study was to determine the magnitude of force to create these bony lesions using cadaveric shoulders.

METHODS

Fourteen fresh-frozen cadaveric shoulders were used. Compression tests were performed using the universal testing machine. The specimens were randomly divided into two groups. In group A, the posterior humeral head (the bare area and articular cartilage) was first compressed against the anterior glenoid rim to simulate a Hill-Sachs lesion, followed by the anterior humeral head being compressed against the posterior glenoid rim. In group B, the same procedure was repeated in the reverse order. X-ray microcomputed tomography (microCT) was also performed.

RESULTS

The maximum compression force to create a Hill-Sachs lesion was 771 ± 214 N (mean ± SD) on the articular cartilage of the posterior humeral head, which was significantly greater than the force of 447 ± 215 N to create it on the bare area (P = 0.0086). Regarding the reverse Hill-Sachs lesions, the maximum compression force was 840 ± 198 N when it was created on the articular cartilage of the anterior humeral head, which was significantly greater than the force of 471 ± 100 N when it was created at the footprint of the subscapularis tendon (P = 0.0238). MicroCT showed multiple breakage of the trabecular bone.

CONCLUSION

A force to create a Hill-Sachs lesion or a reverse Hill-Sachs lesion was significantly greater when it was created on the humeral articular cartilage than at the non-cartilage area. Also, the force to create a reverse Hill-Sachs lesion was significantly greater than the one to create a Hill-Sachs lesion.

Glenoid rim morphology in young athletes with unstable painful shoulders: primarily painful vs. frankly unstable

Background

To investigate the characteristics of glenoid rim morphology in young athletes (<40 yr) with unstable painful shoulder.

Methods

This was a retrospective case series. The inclusion criteria were as follows: (1) shoulder pain during sports activity, (2) traumatic onset, (3) no complaint of shoulder instability, and (4) soft tissue or bony lesions confirmed on imaging examinations (computed tomography and magnetic resonance imaging). The above-mentioned painful cohort was then compared (in a 2:1 ratio) to a match-paired control group of patients with similar demographics but with frank anterior glenohumeral instability as defined by imaging and physical findings. The pain (not apprehension) was reproduced during the anterior apprehension test in supine position and relieved by relocation test in all patients. Glenoid rim morphology, bone union in shoulders with a fragment-type glenoid, glenoid defect size, bone fragment size, medial displacement of bone fragments (MDBF), and medial distance of erosion (MDE) were compared between painful shoulders and unstable shoulders.

Results

There were 79 painful shoulders and 165 unstable shoulders. The glenoid rim morphology was normal in 33 shoulders, erosion-type in 15 shoulders, and fragment-type in 31 shoulders among painful shoulders, whereas the respective shoulders were 19, 33, and 113 among unstable shoulders (P < .001). Bone union was complete in 15 shoulders, partial in 14 shoulders, and nonunion in 2 shoulders among painful shoulders, whereas the respective shoulders were 43, 31, and 39 among unstable shoulders (P = .001). The mean glenoid defect size was 6.0 ± 7.2% and 12.7 ± 7.4%, respectively (P < .001), and the mean bone fragment size was 5.8 ± 6.4% and 5.4 ± 4.6%, respectively, (P = .591). The mean MDBF was 1.4 ± 1.5 mm and 3.0 ± 2.2 mm, respectively (P < .001), and the mean MDE was 2.3 ± 1.2 mm and 5.2 ± 2.4 mm, respectively (P < .001). In shoulders with a smaller glenoid defect (<13.5%), the prevalence of shoulders with MDBF (<2 mm) and shoulders with MDE (<2 mm) was more frequent in painful shoulders. On the other hand, in shoulders with a larger glenoid defect (≥13.5%), erosion-type glenoid, nonunion in fragment-type glenoid and bone fragment smaller than 7.5% was not recognized in painful shoulders. Shoulders with MDBF (<2 mm) were significantly more frequent in painful shoulders (P = .009).

Conclusions

In painful shoulders normal or erosion-type glenoid was predominant, and glenoid defect size was significantly smaller than unstable shoulders. On the other hand, a large bone fragment (≥7.5%) remained and united completely or partially in all shoulders with a larger glenoid defect (≥13.5%). Bone union was obtained within 2 mm from the articular surface in most of them.

Glenoid Track Assessment at Imaging in Anterior Shoulder Instability: Rationale and Step-by-Step Guide

Anterior shoulder dislocation is the most common form of joint instability in humans, usually resulting in soft-tissue injury to the glenohumeral capsuloligamentous and labral structures. Bipolar bone lesions in the form of fractures of the anterior glenoid rim and posterolateral humeral head are often associated with anterior shoulder dislocation and can be a cause or result of recurrent dislocations. Glenoid track assessment is an evolving concept that incorporates the pathomechanics of anterior shoulder instability into its management. Currently widely endorsed by orthopedic surgeons, this concept has ramifications for prognostication, treatment planning, and outcome assessment of anterior shoulder dislocation. The glenoid track is the contact zone between the humeral head and glenoid during shoulder motion from the neutral position to abduction and external rotation. Two key determinants of on-track or off-track status of a Hill-Sachs lesion (HSL) are the glenoid track width (GTW) and Hill-Sachs interval (HSI). If the GTW is less than the HSI, an HSL is off track. If the GTW is greater than the HSI, an HSL is on track. The authors focus on the rationale behind the glenoid track concept and explain stepwise assessment of the glenoid track at CT or MRI. Off-track to on-track conversion is a primary goal in stabilizing the shoulder with anterior instability. The key role that imaging plays in glenoid track assessment warrants radiologists' recognition of this concept along with its challenges and pitfalls and the production of relevant and actionable radiology reports for orthopedic surgeons-to the ultimate benefit of patients. ©RSNA, 2023 Online supplemental material is available for this article. Quiz questions for this article are available through the Online Learning Center.

Glenoid defect size increases but the bone fragment rarely resorbs in shoulders with recurrent anterior instability

Background

With recurrent anterior instability the bone fragment of a bony Bankart lesion is often small compared to the glenoid defect. The purpose of the present study was to clarify the changes to both the bone fragment and glenoid defect over time in a single subject.

Methods

Participants were patients who underwent computed tomography (CT) at least twice after an instability event between 2004 and 2021 and had a fragment-type glenoid at first CT. The glenoid rim width (A), glenoid defect width (B), and bone fragment width (C) were measured in millimeters. If B or C increased by 1 mm or more from the first to final CT, the change was judged as "enlarged," and if B or C decreased by 1 mm or more, it was judged as "reduced"; all other cases were judged as "similar." Then, glenoid defect size and bone fragment size were calculated as B/A×100% and C/A×100%, respectively, and the changes from the first to final CT were compared.

Results

From the first to final CT, the glenoid defect was enlarged in 30 shoulders, similar in 13 shoulders, and reduced in 4 shoulders, and the bone fragment was enlarged in 18 shoulders, similar in 24 shoulders, and reduced in 5 shoulders. The mean glenoid defect size significantly increased from 10.9% to 15.3% (P < .001), and the mean bone fragment size increased from 6.4% to 7.8%, respectively (P = .005). At the final CT, in 6 shoulders a new glenoid fracture was observed at a different site from the original fracture. When they were excluded from the analyses, the mean glenoid defect size still significantly increased (from 11.2% to 15.2%; P < .001), but the mean bone fragment size did not (6.5% vs. 7.3%, respectively; P = .088).

Conclusions

In shoulders with recurrent anterior instability, glenoid defect size appears to increase significantly over time, whereas the bone fragment size remains unchanged or increases only slightly. Bone fragment resorption is quite rare, and a bone fragment appears to be small because of an enlarged glenoid defect.

New bone formation after arthroscopic Bankart repair for unstable shoulders with an erosion-type glenoid defect

BACKGROUND

The purpose of the present study was to retrospectively evaluate new bone formation after arthroscopic Bankart repair (ABR) and the influence of new bone formation on recurrence in shoulders with an erosion-type glenoid defect.

METHODS

We analyzed data on shoulders with an erosion-type glenoid defect. Participants were patients who underwent computed tomography to evaluate new bone formation after ABR performed from 2004 to 2021 and were followed for a minimum of 2 years. We investigated the factors influencing new bone formation, in particular the presence of an intraoperative bone fragment, and the influence of new bone formation and its size on postoperative recurrence.

RESULTS

A total of 100 shoulders were included. The mean glenoid defect size was 10.1% ± 6.3% (range, 1.2%-31.5%). New bone formed postoperatively in 15 shoulders (15.0%) and was seen in significantly more shoulders with an intraoperative bone fragment (11 of 18, 61.1%) than in those without a fragment (4 of 82, 4.9%; P < .001). Recurrence occurred in 22 shoulders (22.0%), and the rate of recurrence was not different between shoulders with new bone formation (3 of 15, 20.0%) and without new bone formation (19 of 85, 22.4%; P = .999). Among the 15 shoulders with new bone formation, the size of the new bone fragments relative to glenoid width was <5% in 2 shoulders, 5%-<7.5% in 8 shoulders, 7.5%-<10% in 3 shoulders, and ≥10% in 2 shoulders; in all 3 shoulders with postoperative recurrence, the relative size was <7.5%.

CONCLUSIONS

Even in shoulders with an erosion-type glenoid defect, new bone may form after ABR, especially in shoulders with an intraoperative bone fragment. However, new bone formation does not decrease the rate of postoperative recurrence.

Knotless Arthroscopic Glenoid Labral Stabilization for a 270° Tear With Concurrent Remplissage in the Lateral Decubitus Position

Labral tears resulting in 270° near-circumferential pathology predispose patients to recurrent instability and are technically challenging to repair. Furthermore, when such lesions are associated with Hill-Sachs lesions, recurrent instability risk is significantly increased and can result in substantially lower clinical outcomes. When determining a surgical treatment algorithm for shoulder stabilization, it is important to consider both humeral- and glenoid-sided pathology because subtle defects can have significant influence on recurrence and patient reported outcomes. In this Technical Note and accompanying video, we discuss our surgical technique for knotless arthroscopic stabilization for a 270° labral tear with concurrent remplissage in the setting of recurrent shoulder instability.

A Glenoid Defect of 13.5% or Larger Is Not Always Critical in Male Competitive Rugby and American Football Players Undergoing Arthroscopic Bony Bankart Repair: Contribution of Resultant Large Bone Fragment

PURPOSE

To investigate bone union and postoperative recurrence after arthroscopic bony Bankart repair (ABBR) in male competitive rugby and American football players with a subcritical glenoid defect of ≥13.5% and to compare findings with those in players with a glenoid defect of <13.5%.

METHODS

Participants were male competitive rugby or American football players with a glenoid defect and bone fragment who underwent ABBR from July 2011 to December 2018 and were followed for a minimum of 2 years. We investigated the influence of glenoid defect and bone fragment size on bone union and postoperative recurrence after ABBR.

RESULTS

We included 45 rugby players and 35 American football players. A total of 38 shoulders were assigned to the small defect group (<13.5%) and 42 to the large defect group (≥13.5%). The complete bone union rate was 47.4% in the small defect group and 71.4% in the large defect group (P = .040), and postoperative recurrence was seen in 13 (34.2%) and 5 shoulders (11.9%), respectively (P = .030). In the small defect group, the bone fragment size was <7.5% in 30 shoulders and ≥7.5% in 8 shoulders; in comparison, the respective numbers were 12 and 30 shoulders in the large defect group, and large fragments (>7.5%) were significantly more common in this group (P < .001). The complete union rate was significantly higher in shoulders with a large fragment (≥7.5%) than in those with a small fragment (<7.5%; 78.9% versus 42.9%, respectively; P = .001). The recurrence rate was 33.3% in shoulders with a small fragment (<7.5%) and 10.5% in shoulders with a large fragment (≥7.5%; P = .017) and was significantly lower in shoulders with a complete union than in those without a complete union (6.3% versus 46.9%, respectively; P < .001).

CONCLUSION

The postoperative recurrence rate after ABBR was lower in male competitive rugby and American football players with a large glenoid defect (≥13.5%) than in those with a small glenoid defect (<13.5%) and might be associated with a higher rate of complete bone union of the resultant large bone fragment (≥7.5%).

LEVEL OF EVIDENCE

III, case-control study.

Anterior Shoulder Instability Part I-Diagnosis, Nonoperative Management, and Bankart Repair-An International Consensus Statement

PURPOSE

The purpose of this study was to establish consensus statements via a modified Delphi process on the diagnosis, nonoperative management, and Bankart repair for anterior shoulder instability.

METHODS

A consensus process on the treatment using a modified Delphi technique was conducted, with 65 shoulder surgeons from 14 countries across 5 continents participating. Experts were assigned to one of 9 working groups defined by specific subtopics of interest within anterior shoulder instability.

RESULTS

The independent factors identified in the 2 statements that reached unanimous agreement in diagnosis and nonoperative management were age, gender, mechanism of injury, number of instability events, whether reduction was required, occupation, sport/position/level played, collision sport, glenoid or humeral bone-loss, and hyperlaxity. Of the 3 total statements reaching unanimous agreement in Bankart repair, additional factors included overhead sport participation, prior shoulder surgery, patient expectations, and ability to comply with postoperative rehabilitation. Additionally, there was unanimous agreement that complications are rare following Bankart repair and that recurrence rates can be diminished by a well-defined rehabilitation protocol, inferior anchor placement (5-8 mm apart), multiple small-anchor fixation points, treatment of concomitant pathologies, careful capsulolabral debridement/reattachment, and appropriate indications/assessment of risk factors.

CONCLUSION

Overall, 77% of statements reached unanimous or strong consensus. The statements that reached unanimous consensus were the aspects of patient history that should be evaluated in those with acute instability, the prognostic factors for nonoperative management, and Bankart repair. Furthermore, there was unanimous consensus on the steps to minimize complications for Bankart repair, and the placement of anchors 5-8 mm apart. Finally, there was no consensus on the optimal position for shoulder immobilization.

LEVEL OF EVIDENCE

Level V, expert opinion.

Remaining Large Bone Fragment of a Bony Bankart Lesion in Shoulders With a Subcritical Glenoid Defect: Association With Recurrent Anterior Instability

BACKGROUND

A preoperative glenoid defect of 13.5% or larger is recognized as a subcritical glenoid defect at arthroscopic Bankart repair (ABR) for collision/contact athletes or military personnel.

PURPOSE

To clarify the prevalence and size of remaining bone fragments in shoulders with a subcritical glenoid defect at recurrent anterior instability and to investigate the influence on postoperative recurrence after ABR for younger competitive athletes.

STUDY DESIGN

Cohort study; Level of evidence, 4.

METHODS

The study included 96 shoulders with recurrent instability that underwent ABR between July 2011 and March 2018 for shoulders with a subcritical glenoid defect. The patients were divided into 2 groups according to the glenoid defect size (13.5%-<20%, medium; ≥20%, large). The bone fragment size in each defect group was retrospectively investigated and classified into 4 groups (no, 0%; small, >0%-<5%; medium, 5%-<10%; large, ≥10%). The postoperative recurrence rate for each combination of glenoid defect size and bone fragment size was investigated for competitive athletes aged <30 years. The fragments, when present, were repaired to the glenoid.

RESULTS

The glenoid defect size was 13.5%-<20% in 60 shoulders (medium defect group) and ≥20% in 36 shoulders (large defect group). The mean bone fragment size was 6.7% ± 5.1% and 8.9% ± 4.9%, respectively (P = .042). In the medium defect group, there were 15 shoulders (25%) without a bone fragment, 6 shoulders (10%) with a small fragment, 23 shoulders (38.3%) with a medium fragment, and 16 shoulders (26.7%) with a large fragment. In the large defect group, the respective numbers were 2 shoulders (5.6%), 6 shoulders (16.7%), 14 shoulders (38.9%), and 14 shoulders (38.9%). A medium or large bone fragment was more common in the large defect group (P = .252). Among 64 younger competitive athletes who underwent ABR with a minimum of 2 years of follow-up, postoperative recurrence was recognized in 7 of 38 (18.4%) athletes in the medium defect group, but it was not recognized in any of the 26 athletes in the large defect group (P = .036). Postoperative recurrence was recognized in 4 of 12 (33.3%) athletes with a small fragment or no fragment and in 3 of 52 (5.8%) athletes with a medium or large fragment (P = .019).

CONCLUSION

A larger bone fragment frequently remained in shoulders with a subcritical glenoid defect at recurrent instability. The postoperative recurrence rate after ABR for younger competitive athletes was low when a remaining larger bone fragment was repaired.

Editorial Commentary: It Is Not the Size, But the Location of Hill-Sachs Lesion That Matters

The risk of a Hill-Sachs lesion (HSL) to engage the anterior glenoid rim depends on the location of the medial margin of the HSL relative to the anterior rim of the glenoid. The same-sized HSL can be engaging or nonengaging depending upon the size of the glenoid. In order to assess these bony lesions (bipolar lesion) together, the glenoid track concept has been introduced: an on-track lesion (stable) and an off-track lesion (unstable). Three-dimensional computed tomography (3D-CT) confirms that more medialized HSLs have larger volume, greater width, more surface area loss, and higher lesion angles (HS angle), and are more inferior in the humeral head. We know that medialization of the HSL is a definitive risk factor to make it off track, whereas the volume, surface area, and width are all subordinate risk factors dependent on the medialization. On the other hand, while we know very little about the orientation of the HSL, recent research shows a significant association between the medialization and orientation of the HSL. However, we do not know whether the orientation is an independent risk factor or dependent on the medialization. There are two things I emphasize when I look at a HSL: 1) do not look at the HSL alone, but look at the glenoid as well, and 2) the risk of the HSL depends on the location of the medial margin of the HSL relative to the glenoid, not on the volume, depth, or length.