Biomechanics of complex shoulder instability

Variability in quantifying the Hill-Sachs lesion: A scoping review

Background

Currently, is there no consensus on a widely accepted measurement technique for calculating the Hill-Sachs lesion (HSL). The purpose of this review is to provide an overview of the techniques and imaging modalities to assess the HSL pre-operatively.

Methods

Four online databases (PubMed, Embase, MEDLINE, and COCHRANE) were searched for literature on the various modalities and measurement techniques used for quantifying HSLs, from data inception to 20 November 2021. The Methodological Index for Non-Randomized Studies tool was used to assess study quality.

Results

Forty-five studies encompassing 3413 patients were included in this review. MRA and MRI showed the highest sensitivity, specificity, and accuracy values. Intrarater and interrater agreement was shown to be the highest amongst MRA. The most common reference tests for measuring the HSL were arthroscopy, radiography, arthro-CT, and surgical techniques.

Conclusion

MRA and MRI are reliable imaging modalities with good test diagnostic properties for assessment of HSLs. There is a wide variety of measurement techniques and imaging modalities for HSL assessment, however a lack of comparative studies exists. Thus, it is not possible to comment on the superiority of one technique over another. Future studies comparing imaging modalities and measurement techniques are needed that incorporate a cost-benefit analysis.

Belt and suspender technique for bipolar bone loss in shoulder instability

Bipolar glenohumeral bone loss is a challenging condition to address in patients with recurrent anterior shoulder instability. In this category of patients, most isolated soft-tissue procedures such as remplissage or infraspinatus capsulotenodesis are associated with high risk of failure and instability recurrence. Even bony procedures such as Latarjet may fail to provide absolute stability, and instability may eventually recur. For a better understanding of the cause of failure in this particular type of patient, we may refer to the glenoid track concept which has been described as a useful tool for surgical planning. In fact, Latarjet procedure alone may leave a place for engagement of the Hill-Sachs defect on the anterior glenoid resulting in an off-track situation and secondary glenohumeral instability. In this technical note, we present the combination of arthroscopic remplissage and an open Latarjet procedure to treat patients with bipolar glenohumeral bone loss with good results at 31-month follow-up. Our aim is to propose these techniques as a possible rescue procedure for highly unstable shoulders combining engaged Hill-Sachs lesion and glenoid bone loss of more than 25%. We believe this technique would be a good option for patients who present other risk factors of recurrence such as past medical history of epilepsy, laxity, and psychiatric illnesses.

[Anterior shoulder instability with non critical bone loss: Bankart-Remplissage or Latarjet?]

INTRODUCTION

Significant Hill-Sachs lesions are associated with recurrent shoulder instability. Bankart-Remplissage (B+R) and Latarjet (L) are valid treatments for these injuries. Few studies compare both techniques.

OBJECTIVE

To compare functional outcome, complications and recurrent instability rate between B+R and L in patients operated for anterior shoulder instability (ASI) with significant Hill-Sachs (HS) lesions and non critical glenoid bone loss (NC-GBL).

MATERIAL AND METHODS

Retrospective cohort study with patients operated between 2010 and 2018 for ASI. 107 met inclusion criteria. Demographic data, complications, recurrence rate and subsequent procedures were obtained from their medical records. CT scan imaging was used to assess humeral and glenoid bone loss. Online questionnaires were sent for assesing functional outcomes with SSV, WOSI, VAS and qDASH. 48 patients completed the online assessment (26 B+R, 22 L). The mean follow-up was 3.8 years.

RESULTS

Comparing both groups, there were no differences in WOSI, SSV, EVA and qDASH. There was no difference in complication rate (B+R: 13 [18.8%], L: 5 [13.2%], p = 0.16), revisions (B+R: 4 [5.7%], L: 1 [2.6%], p = 0.41) and recurrent instability (B+R: 4 [5.7%], L: 1 [2.6%], p = 0.41). L in subgroup who practiced collision sports had better SSV (92.5 vs 72.5 p = 0.048) and WOSI (98.3 vs 67.3 p = 0.043). B+R in dominant extremity had worst complication rate (50 vs 9.1% p = 0.038). Association was not found between complications and recurrent instabillity according to glenoid bone defect or previous dislocation episodes.

CONCLUSION

Significant Hill-Sachs lesions with NC-GBL, both Bankart-Remplissage and Latarjet achieve satisfactory results, with similar recurrent instability and functional outcomes. Latarjet has better subjetive funtional results in collision sports and less complication in dominant extremity compared to Bankart-Remplissage.

Helical axis analysis to quantify humeral kinematics during shoulder rotation

Information pertaining to the helical axis during humeral kinematics during shoulder rotation may be of benefit to better understand conditions such as shoulder instability. The aim of this study is to quantify the behavior of humeral rotations using helical axis (HA) parameters in three different conditions. A total of 19 people without shoulder symptoms participated in the experiment. Shoulder kinematics was measured with an optoelectric motion capture system. The subjects performed three different full range rotations of the shoulder. The shoulder movements were analyzed with the HA technique. Four parameters were extracted from the HA of the shoulder during three different full-range rotations: range of movement (RoM), mean angle (MA), axis dispersion (MDD), and distance of their center from the shoulder (D). No significant differences were observed in the RoM for each condition between left and right side. The MA of the axis was significantly lower on the right side compared to the left in each of the three conditions. The MDD was also lower for the right side compared to the left side in each of the three conditions.The four parameters proposed for the analysis of shoulder kinematics showed to be promising indicators of shoulder instability.

Concurrent validity of handheld dynamometer measurements for scapular protraction strength

BACKGROUND

Handheld dynamometers (HHD) provide quick and low-cost assessments of muscle strength and their use has been increasing in clinical practice. There is no available data related to the validity of HHD for this measurement.

OBJECTIVE

To verify the concurrent validity of scapular protraction measurements using an HHD.

METHODS

Individuals with traumatic anterior glenohumeral instability were allocated in Instability Group (n=20), healthy swimmers were allocated in Athletes Group (n=19) and healthy subjects were allocated in Sedentary Group (n=21). Concurrent validity was verified by the Pearson correlation test between HHD and isokinetic measurements. The agreement between instruments was verified by Bland-Altman plots, for each of the two HHD positions.

RESULTS

A moderate correlation was observed between seated (r=0.59) and lying supine HHD (r=0.54) and isokinetic dynamometer measurements for the all groups. Separated group analysis exhibited a strong correlation between seated HHD and isokinetic dynamometer measurements in the Instability Group (r=0.80), Sedentary Group (r=0.79) and Athletes Group (r=0.76). The Bland-Altman plot showed greater agreement in the seated position than the lying supine position when comparing measurements with the HHD and isokinetic in both the general sample and separated groups.

CONCLUSION

The HHD may be considered a valid tool for assessing scapular protraction muscle strength among healthy athletes, non-athletes and subjects with shoulder instability. We recommend to assess subjects in the seated position and to be aware that the HHD tends to overestimate the peak force, compared with the gold-standard isokinetic dynamometer.

Remplissage versus latarjet for engaging Hill-Sachs defects without substantial glenoid bone loss: a biomechanical comparison

BACKGROUND

Recurrent shoulder instability is commonly associated with Hill-Sachs defects. These defects may engage the glenoid rim, contributing to glenohumeral dislocation. Two treatment options to manage engaging Hill-Sachs defects are the remplissage procedure, which fills the defect with soft tissue, and the Latarjet procedure, which increases glenoid arc length. Little evidence exists to support one over the other.

QUESTIONS/PURPOSES

We performed a biomechanical comparison of the remplissage procedure to the traditional Latarjet coracoid transfer for management of engaging Hill-Sachs defects in terms of joint stiffness (resistance to anterior translation), ROM, and frequency of dislocation.

METHODS

Eight cadaveric specimens were tested on a shoulder instability simulator. Testing was performed with a 25% Hill-Sachs defect with an intact glenoid and after remplissage and Latarjet procedures. Joint stiffness, internal-external rotation ROM, and frequency of dislocation were assessed. Additionally, horizontal extension ROM was measured in composite glenohumeral abduction.

RESULTS

After remplissage, stiffness increased in adduction with neutral rotation (12.7 ± 3.7 N/mm) relative to the Hill-Sachs defect state (8.7 ± 3.3 N/mm; p = 0.016). The Latarjet procedure did not affect joint stiffness (p = 1.0). Internal-external rotation ROM was reduced in abduction after the Latarjet procedure (49° ± 14°) compared with the Hill-Sachs defect state (69° ± 17°) (p = 0.009). Horizontal extension was reduced after remplissage (16° ± 12°) relative to the Hill-Sachs defect state (34° ± 8°) (p = 0.038). With the numbers available, there was no difference between the procedures in terms of the frequency of dislocation after reconstruction: 84% of specimens (27 of 32 testing scenarios) stabilized after remplissage, while 94% of specimens (30 of 32 testing scenarios) stabilized after the Latarjet procedure.

CONCLUSIONS

Both procedures proved effective in reducing the frequency of dislocation in a 25% Hill-Sachs defect model, while neither procedure consistently altered joint stiffness.

CLINICAL RELEVANCE

In the treatment of shoulder instability with a humeral head bone defect and an intact glenoid rim, this study supports the use of both the remplissage and Latarjet procedures. Clinical studies and larger cadaveric studies powered to detect differences in instability rates are needed to evaluate these procedures in terms of their comparative efficacy at preventing dislocation, as any differences between them seem likely to be small.