Glenoid track and subcritical Hill-Sachs lesion

Background

We have proposed the concept of glenoid track ("on-track/off-track" lesion) to evaluate the risk of engagement of the Hill-Sachs lesion with the glenoid after arthroscopic Bankart repair. This concept has been widely used and many clinical validation studies have been reported. To measure the glenoid track width, we have recommended to use 3-dimensional computed tomography (CT) images. However, the CT method has the issue of radiation exposure and involves time and effort to make 3-dimensional CT images from 2-dimensional images. For these reasons, there are several reports describing the measurement method using magnetic resonance imaging. Recently, the threshold of the critical glenoid bone loss becomes lower. A zone of bone loss below the critical size is called "subcritical bone loss", which might be related to deterioration of quality of life and bone grafting is recommended. We applied the concept of "subcritical bone loss" to the glenoid track. Patients with "on-track" lesions can be divided into 2 subgroups: those with a "peripheral-track" lesion (most medial 1/4) and those with a "central-track" lesion (the rest 3/4). More recently, similar evaluation methods to evaluate the risk of "off-track" lesions have been reported: ''distance to dislocation'' and "Hill-Sachs interval/glenoid track ratio". Also, similar concept to "peripheral-track" lesion, "near-track" lesion was reported. The concept of "peripheral-track" lesion is a concept of assessing an "on-track" lesion which is very close to the medial margin of the glenoid track (subcritical bone loss).

Methods

Similar evaluation methods to evaluate the risk of "off-track" or "peripheral-track" lesions were proposed in the literature. A review was performed by searching PubMed. Journal articles published between January 2014 and January 2023 were taken into account. They were compared and their differences were explained.

Results

The "near-track" lesion concept is similar to "peripheral-track" lesion. However, the cutoff value is different: Hill-Sachs occupancy ≥ 75% is the "peripheral-track" lesion, whereas "distance to dislocation" < 8 mm is the "near-track" lesion.

Conclusion

We introduced update of the glenoid track concept including the evaluation method, peripheral-track lesion, and its clinical application.

Effective glenoid track: A novel concept for shoulder instability

Background

Assessment and quantification of bone loss in cases of shoulder instability is critical for surgical decision making. The glenoid track concept was initially developed to assess Hill Sachs lesions taking into account the native glenoid diameter of the contralateral shoulder and assessing the degree of glenoid bone loss. However, it can not be reverse calculated to determine the effect of an addition of a bone block. We have developed a novel model to help address this problem yielding an "effective glenoid track" (EGT).

Methods

Begin as we always do by using Itoi's concept for assessment of tracking based on the CT scan cuts. Next step is to calucate the Hill Sach's interval (HSI) which will require an MRI scan.

Conclusion

The EGT allows for calculation of residual tracking of Hill Sachs lesions post a bone block addition and will aid in surgical decision making.

The glenoid track concept is insufficient to predict Bankart failures: a computed tomography scan study

Background

The glenoid track concept identifies patients with "off-track" (engaging) Hill-Sachs lesions (HSLs) as poor candidates for arthroscopic Bankart repair (ABR) due to the high risk of shoulder instability recurrence.

Purpose

To retrospectively calculate the glenoid track index, using preoperative computed tomography (CT) scans, in a cohort of patients with failed ABR. We hypothesized that all patients with a failed ABR would have engaging ("off-track") HSLs on preoperative CT scan.

Type of Study

CT scan study.

Methods

Preoperative CT scan of 45 patients, seen in our facility for failed ABR, was used to retrospectively calculate the glenoid track index. The risk of recurrence was also calculated for each patient using Instability Severity Index Score (ISI-Score) and Glenoid Track Instability Management Score (GTIMS). There were 37 failed isolated ABRs and 8 associated HS remplissage. The mean t age at surgery was 24 years (range, 15-52) and instability recurred at a mean of 29 months postoperative (range, 3-167).

Results

Preoperative CT scan imaging identified "off-track" bony lesions in 85% of patients (38/45) and "on-track" lesions in 15% (7/45). No significant differences were noted between the 2 groups (off-track vs. on-track) regarding patient age, hyperlaxity, sports participation, size of HS lesion, or ISI-Score. The mean glenoid bone loss was 15.7% (range, 4-36%) with mean HS width was greater than 20 mm in 66% of CT scans. The preoperative ISI-Score was predictive of failures (>3 points in all patients) with no difference between on-track and off-track patients (6.3 ± 1.7 vs. 6.6 ± 1.7, P = .453). By contrast, the GTIMS did not predict failures as there was a significant difference between GTIMS for on-track and off-track patients (2.1 ± 1.3 vs. 6.6 ± 1.7).

Conclusions

The glenoid track concept alone is insufficient to predict Bankart failures: in the present series of failed ABR, 15% of shoulders had "on-track" (non-engaging) lesions on preoperative CT scan. In patients, with "on-track" bony lesions, the ISI-Score is a useful predictive tool to detect patients at risk of failure, while the GTIMS is not.

Longer peripheral-track lesions are associated with instability after arthroscopic Bankart repair

BACKGROUND

The Glenoid track concept has enabled the categorization of Hill-Sachs lesions (HSLs) into on-track lesions and off-track lesions. Furthermore, among the on-track lesions, further categorization has been established based on the distance from the medial edge of the Hill-Sachs lesion to the medial edge of the glenoid track, into peripheral-track lesions and central-track lesions. Recent studies on peripheral-track lesions and central-track lesions within the glenoid track have shown inconsistencies in failure rates, which deserves further investigation.

METHODS

A retrospective cohort comparison of patients who underwent arthroscopic Bankart repair between 2015 and 2020 was performed. 102 patients with peripheral-track HSLs were included. The patients were divided into two groups based on the results of the postoperative apprehension test: the apprehension positive group (n=30), and the apprehension negative group (n=72). Using preoperative computed tomography and an image reconstruction program, three-dimensional images were segmented to calculate the length, width, depth, and distance of the HSLs. A multivariate logistic regression was used to determine the risk factors of recurrence, for which odds ratio (OR) and 95% confidence interval (CI) were provided.

RESULTS

A multivariate logistic regression analysis revealed that the length of the peripheral-track HSLs was a significant independent predictor of failure in this study. (OR 1.380; 95% CI 1.170-1.627; P<0.001). The receiver operating characteristics curve demonstrated a predictive power (area under the curve = 0.841) and a threshold value of 14.2 mm.

CONCLUSION

Length was the only risk factor for the recurrent instability of peripheral-track HSLs after ABR. In the context of surgical decision-making, utilizing the glenoid track concept, medical practitioners may need to evaluate instability by considering the length as a continuous factor, while differentiating between peripheral-track and central-track classifications.

Current Concepts in the Measurement of Glenohumeral Bone Loss

PURPOSE

The extent of glenohumeral bone loss seen in anterior shoulder dislocations plays a major role in guiding surgical management of these patients. The need for accurate and reliable preoperative assessment of bone loss on imaging studies is therefore of paramount importance to orthopedic surgeons. This article will focus on the tools that are available to clinicians for quantifying glenoid bone loss with a focus on emerging trends and research in order to describe current practices.

RECENT FINDINGS

Recent evidence supports the use of 3D CT as the most optimal method for quantifying bone loss on the glenoid and humerus. New trends in the use of 3D and ZTE MRI represent exciting alternatives to CT imaging, although they are not widely used and require further investigation. Contemporary thinking surrounding the glenoid track concept and the symbiotic relationship between glenoid and humeral bone loss on shoulder stability has transformed our understanding of these lesions and has inspired a new focus of study for radiologists and orthopedist alike. Although a number of different advanced imaging modalities are utilized to detect and quantify glenohumeral bone loss in practice, the current literature supports 3D CT imaging to provide the most reliable and accurate assessments. The emergence of the glenoid track concept for glenoid and humeral head bone loss has inspired a new area of study for researchers that presents exciting opportunities for the development of a deeper understanding of glenohumeral instability in the future. Ultimately, however, the heterogeneity of literature, which speaks to the diverse practices that exist across the world, limits any firm conclusions from being drawn.

Open anatomical glenoid reconstruction with an iliac crest bone autograft effectively resolves off-track Hill-Sachs lesions to on-track lesions

INTRODUCTION

The purpose of this study was to determine if "off-track" Hill-Sachs lesions in patients with dynamic anteroinferior instability were transformed into "on-track" lesions using iliac bone autografts with screw fixation. The secondary purpose was to observe if postoperative bony remodeling would occur over time, resulting in recurrent "off-track" Hill-Sachs lesions with corresponding instability.

MATERIALS AND METHODS

We retrospectively reviewed clinical and CT records of 8 patients with an "off-track" Hill-Sachs lesion who underwent open anatomical glenoid reconstruction with an iliac crest bone autograft. Hill-Sachs lesions, glenoid track widths, and glenoid surface areas were measured on a preoperative and two postoperative (6 weeks, ≥ 2 years) 3D-CT models to determine graft resorption over time. All patients were available for postoperative clinical and CT final follow-up 3 years (2-4 years) postoperatively.

RESULTS

In all patients, the Hill-Sachs lesions were "on-track" 6 weeks postoperatively and remained "on-track" at final-follow-up. Compared to preoperative values, the glenoid track width and glenoid surface area both were higher 6 weeks postoperatively (p < 0.001 and p = 0.023, respectively) and at final follow-up (p < 0.001 and p = 0.023, respectively). Whereas the glenoid track width between 6 weeks and final follow-up showed no decrease (p = 0.234), glenoid surface area tended to decrease (p = 0.055). The median SSV was 93 points (85-95 points), the Rowe score 90 points (80-100 points) and the WOSI 1980 points (1783-2067 points) at final follow-up. No recurrent dislocations or subluxations were observed.

CONCLUSIONS

An open anatomical glenoid reconstruction with an iliac crest bone autograft technique using screw fixation effectively transformed "off-track" Hill-Sachs lesions to "on-track" lesions, resulting in good short-term clinical outcomes. Whereas glenoid surface area tended to be reduced by bony remodeling processes over time, the glenoid track width did not decrease at final follow-up and consequently no recurrence of "off-track" lesions occurred.

LEVEL OF EVIDENCE

Case series; Level of evidence, IV.

A numerical study of the contact geometry and pressure distribution along the glenoid track

The glenoid track geometry and the contact forces acting on the glenohumeral joint at static positions of 30°, 60°, 90° and 120° of abduction with 90° of external rotation were evaluated using a finite element model of the shoulder that, differently from most usual approximations, accounts the humeral head translations and the deformable-to-deformable non-spherical joint contact. The model was based on data acquired from clinical exams of a single subject, including the proximal humerus, scapula, their respective cartilages concerning the glenohumeral joint, and the rotator cuff and deltoid muscles. The forces acting on the glenohumeral joint were estimated using a simulation framework consisting of an optimization procedure allied with finite element analysis that seeks the minimum muscle forces that stabilize the joint. The joint reaction force magnitude increases up to 680.25 N at 90° of abduction and decreases at further positions. From 60° onward the articular contact remains at the anterior region of the glenoid cartilage and follows an inferior to superior path at the posterior region of the humeral head cartilage. The maximum contact pressure of 3.104 MPa occurs at 90° abduction. Although translating inferiorly throughout the movement, the projection of the humeral head center at the glenoid plane remains at the central region of the glenoid surface. The model results qualitatively matched the trends observed in the literature and supports the consideration of the translational degrees of freedom to evaluate the joint contact mechanics.

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.

Assessing Bone Loss in the Unstable Shoulder: a Scoping Review

PURPOSE OF REVIEW

The aim of this scoping review is to identify and summarize findings published in the literature over the past 5 years related to methods for assessment of bone loss in anterior shoulder instability.

RECENT FINDINGS

Of the 113 clinical studies included in this review, 76 reported a cutoff for glenoid bone loss when determining the patients indicated for one of the many stabilization procedures investigated. Bone loss on the glenoid side was evaluated most commonly with three-dimensional computed tomography (3D CT), and either linear or surface area-based methods were employed with the use of a best-fit circle. When combined with plain CT, the two methods comprise up to 70% of the reported measurement techniques for glenoid bone loss (79 of 113 studies). On the humeral side, Hill-Sachs lesions were assessed more heterogeneously, though plain CT or 3D CT remained the methods of choice in the majority of studies (43 of 68, 63.2%). Lastly, the glenoid track was assessed by 27 of 113 studies (23.9%), again most commonly with 3D CT (13 studies) and plain CT (seven studies). The assessment of glenoid and humeral bone loss is essential to treatment decisions for patient with recurrent anterior shoulder instability. Glenoid bone loss is most commonly assessed using cross-sectional imaging, most often 3D CT, and some variation of a best-fit circle applied to the inferior portion of the glenoid. Hill-Sachs lesion assessment was also commonly done using three-dimensional imaging; however, there was more variability in assessment methods across studies and there is an obvious need to unify the approach to humeral bone loss assessment for the purposes of improving treatment decisions and to better assess on-track and off-track lesions.

Remplissage for Anterior Shoulder Instability: History, Indications, and Outcomes

Remplissage is a nonanatomic capsulotenodesis of the infraspinatus tendon used to fill engaging or "off-track" Hill-Sachs lesions in patients at high risk of recurrent instability with isolated Bankart repair. Indications for remplissage are expanding, as the importance of subcritical bone loss and the glenoid track on patient outcomes and recurrence rates continues to be investigated. Remplissage is also suggested in patients at high risk of recurrent instability following isolated anterior labral repair, such as collision and contact athletes with Hill-Sachs lesions that have not reached the threshold of "off track." Multiple arthroscopic remplissage techniques exist including, more recently, knotless techniques.

Long-term outcomes of arthroscopic Bankart repair and Hill-Sachs remplissage for bipolar bone defects

PURPOSE

To evaluate long-term results after arthroscopic Bankart repair and Hill-Sachs remplissage (BHSR) in bipolar bone defects with less than 20% of glenoid bone loss (GBL) and to analyse risk factors for recurrent dislocation.

METHODS

From 2009-2012, 43 patients with recurrent anterior shoulder instability were treated with BHSR. Inclusion criteria were GBL < 20% and minimum of 4-yearfollow-up. There were 35 males and 8 females with a mean age of 29 years (range 16-53). The mean ISIS score was 3.6 (range 2-6). Patients were evaluated for recurrence, range of motion and functional outcomes (Walch-Duplay and Rowe score). Post-operative MRI was performed at least 6 months after surgery to evaluate infraspinatus capsulotenodesis healing. Glenoid track was assessed retrospectively from pre-operative computed tomography. Mean follow-up was 7.3 years (range 4-11).

RESULTS

At the last follow-up, good to excellent outcomes were reported in 86% of patients. Average post-operative Walch-Duplay was 87.9 (range 75-100) and ROWE 93.7 (range 70-100). Infraspinatus capsulotenodesis healing was achieved in 86%. The rate of recurrence and revision surgery was 9.3% and 13.9%, respectively. Recurrence was associated with higher ISIS score (p = 0.0191) and lower age at surgery (p = 0.0227). Four (9.3%) Hill-Sachs lesions were considered off-track. The presence of off-track Hill-Sachs was associated with higher risk of recurrence (p < 0.00001).

CONCLUSION

Arthroscopic BHSR improves shoulder instability in the setting of bipolar bone defects with less than 20% of GBL. Patient-related factors and pre-operative glenoid track should be taken into consideration to reduce the risk of recurrence.

Glenoid track measurement using magnetic resonance imaging arthrography is predictive of recurrent instability following arthroscopic shoulder stabilisation

PURPOSE

The primary aim of this study was to investigate medium-term survivorship following arthroscopic Bankart repair (ABR) for anterior glenohumeral instability. The secondary aim was to determine whether the pre-operative magnetic resonance (MR) arthrography glenoid track measurement predicted recurrent instability following ABR.

METHODS

Over a 9-year period (2008-2017), 215 patients underwent ABR. Median age was 26 years (IQR 22-32.5; range 14-77). There were 173 males (81%). 175 patients (81%) had available pre-operative MR arthrography, which was used to determine the presence of "off-track" bone loss. Retrospective analysis was undertaken to determine recurrence of instability at a median follow-up of 76 months (range 21-125 months). Survivorship analysis was undertaken using Kaplan-Meier methodology: the endpoints examined were repeat dislocation, revision stabilisation, and symptomatic instability.

RESULTS

56 patients (26%) presented with further instability, including 29 patients with recurrent dislocation and 15 patients required revision stabilisation. Cumulative incidence of instability was 10% at 1 year, 27% at 5 years and 28% at 7 years. No significant difference in instability was seen between men and women 7 years after stabilisation (19% vs 17%; p = 0.87). Age at time of surgery did not predict recurrence. "Off-track" lesions were identified in 29 patients (16.1%). The incidence of redislocation was significantly higher in these patients (24% vs 3%; p = 0.01; relative risk 7.2; 95% CI 2.45-20.5; p = 0.001). Recurrent instability without frank redislocation was also significantly higher in this group (60% vs 18%; RR 3.33, 95% CI 2.02-5.20; p < 0.0001).

CONCLUSIONS

This study has reported a significant rate of recurrent instability in longer-term follow-up after ABR. It has also identified pre-operative MR arthrography as an important predictor of recurrent instability, which may be used to risk stratify patients with anterior instability in a typical UK population.

LEVEL OF EVIDENCE

III (cohort study).

Influence of the glenoid track and glenoid bone loss on the apprehension test for shoulder instability

Background

The investigation of Hill-Sachs and bony Bankart lesions continues to evolve. Patients with large bone lesions can present with a positive apprehension test even at ranges below 45° of abduction and external rotation of the shoulder. Modern concepts, such as glenoid track and quantification of glenoid bone loss, have been increasingly applied to shoulder instability. The objective of this study was to assess the correlation of the glenoid track and glenoid bone loss on the apprehension test conducted at 0°, 45°, and 90° of shoulder abduction.

Methods

Ninety-four shoulders of 90 patients with anterior glenohumeral instability were retrospectively assessed. The apprehension test was performed at 0°, 45°, and 90° of shoulder abduction. Computed tomography, magnetic resonance imaging, or magnetic resonance arthrogram scans were performed to calculate the glenoid track and glenoid bone loss. A descriptive analysis, an association analysis, and a logistic regression analysis were used in this study. Logistic regression analysis was used to assess the influence of glenoid track and glenoid bone loss when the apprehension test was positive in lower degrees of abduction.

Results

A positive apprehension test at 0°, 45°, and 90° of abduction revealed significant association with off-track lesions, glenoid bone losses greater than 13.5%, and bipolar bone lesions. Shoulders classified as off-track were 36.4 times more likely to test positive at 0°, 45°, and 90° than on-track shoulders. The logistic regression analysis revealed that the positive apprehension test at 0°, 45°, and 90° of abduction seems to be more influenced by off-track lesions than by glenoid bone loss greater than the 13.5% threshold.

Conclusion

Shoulders with a positive apprehension test at 0°, 45°, and 90° are significantly associated with off-track lesions, bipolar bone lesions, and glenoid bone losses greater than 13.5%.

Off-track Hill-Sachs lesions predispose to recurrence after nonoperative management of first-time anterior shoulder dislocations

PURPOSE

The purpose of this study was to evaluate whether the presence of an off-track Hill-Sachs lesion has an impact on the recurrence rate after nonoperative management of first-time anterior shoulder dislocations.

METHODS

A retrospective cohort study was planned with a follow-up via questionnaire after a minimum of 24 months. Fifty four patients were included in the study (mean age: 29.5 years; 16 female, 38 male). All of these patients opted for primary nonoperative management after first-time traumatic anterior shoulder dislocation, in some cases even against the clinician's advice. The glenoid track and the Hill-Sachs interval were evaluated in the MRI scans. The clinical outcome was evaluated via a shoulder-specific questionnaire, ASES-Score and Constant Score. Further, patients were asked to report on recurrent dislocation (yes/no), time to recurrent dislocation, pain, feeling of instability and satisfaction with nonoperative management.

RESULTS

In 7 (13%) patients, an off-track Hill-Sachs lesion was present, while in 36 (67%) the lesion was on-track and 11 (20%) did not have a structural Hill-Sachs lesion at all. In total, 31 (57%) patients suffered recurrent dislocations. In the off-track group, all shoulders dislocated again (100%), while 21 (58%) in the on-track group and 3 (27%) in the no structural Hill--Sachs lesion group had a recurrent dislocation, p = 0.008. The mean age in the group with a recurrence was 23.7 ± 10.1 years, while those patients without recurrent dislocation were 37.4 ± 13.1 years old, p < 0.01. The risk for recurrence in patients under 30 years of age was higher than in those older than 30 years (OR = 12.66, p < 0.001). There were no significant differences between patients with on- and off-track lesions regarding patients' sex, height, weight and time to reduction and glenoid diameter. Off-track patients were younger than on-track patients (24.9 ± 7.3 years vs. 29.6 ± 13.6 years). However, this difference was not statistically significant.

CONCLUSION

The presence of an off-track Hill-Sachs lesion leads to significantly higher recurrence rates compared to on-track or no structural Hill--Sachs lesions in patients with nonoperative management and should be considered when choosing the right treatment option. Therefore, surgical intervention should be considered in patients with off-track Hill-Sachs lesions.

LEVEL OF EVIDENCE

IV.

[Reliability of three dimensional CT measurement of glenoid track in patients with recurrent anterior dislocation of shoulder]

OBJECTIVE

To evaluate the reliability and repeatability of three-dimensional (3D)-CT measurement of glenoid track.

METHODS

Glenoid and Hill-Sachs bone defects in 60 patients with recurrent anterior dislocation of the unilateral shoulder were evaluated by 3D-CT and analyzed by three independent observers(shoulder orthopedists) according to the Di Giacomo method. These injuries were classified to formulate a surgical protocol. All the patients were repeatedly measured 1 week later. Intraclass correlation coefficient (ICC) and coefficient of variation (COV) were used for reliability analysis.

RESULTS

Interobserver reliability was "very good" for both measurements of glenoid diameter and glenoid bone defects, and "good" for measurements of Hill-Sachs interval. Interobserver agreement was high on the assessment of the extent of the glenoid defect, and poor on track/off track assessment of the Hill-Sachs lesion. Intraobserver reliability for measurements of glenoid diameter, glenoid defect, and Hill-Sachs interval was "very good". The COV was 4.1% for glenoid diameter, 4.4% for glenoid defect, and 21.1% for Hill-Sachs interval.

CONCLUSION

The reliability and reproducibility of 3D-CT measurements of glenoid bone defects are good, but the assessment of humeral head bone defects shows large variability with poor reliability.

Glenoid track ''off-track'' as a risk factor for recurrence of anterior glenohumeral instability in postoperative patients

INTRODUCTION

Glenoid track is used to assess the engagement of Hill-Sachs lesions. The objective of this study was to identify if off-track glenoid track was a risk factor for recurrence of anterior glenohumeral instability in postoperative patients with arthroscopic anterior labrum repair.

MATERIAL AND METHODS

Sixty patients with glenohumeral instability who underwent arthroscopic repair of the anterior labrum were studied. Study group (patients with recurrence of postoperative dislocation) and control (no dislocation). Radiographic measurements were made on magnetic resonance imaging and computed tomography. Measurements of glenoid diameter, glenoid bone loss, as well as the presence and size of Hill-Sachs lesions were obtained. Later they were classified as "on-track" or "off-track".

RESULTS

Seven (11.67%) patients suffered recurrence, of which six (10%) were carriers of an off-track injury and 1 (1.67%) on-Track. 53 (88.33%) patients did not experience recurrence, of which 11 (18.33%) were carriers of an off-track injury and 42 (70%) on track. A 23.47 increased risk of recurrence of instability was interpreted in patients with "off-track" lesions compared to patients with "On track" lesions.

CONCLUSIONS

Off-track injuries were a risk factor for recurrence of instability in patients who underwent Bankart-type arthroscopic repair. This allows us to recommend that the presence of lesions be routinely studied and classified as "on-track" or "off-track" to provide a better therapeutic approach.

Glenoid track evaluation by a validated finite-element shoulder numerical model

BACKGROUND

The limits of the glenoid track have been defined through methods that do not take properly into account the physiological articular forces involved in the articular contact, which may interfere with its size. Finite elements numerical models can simulate joint forces more realistically.

OBJECTIVE

To evaluate the glenoid track in a finite element numerical model of the shoulder.

METHODS

We developed a finite element numerical model of the shoulder, based on imaging exams of a volunteer, including the proximal humerus, scapula, their respective articular cartilages, and the rotator cuff muscles. An algorithm to balance the weight of the arm calculated muscle, wrapping, and articular reaction forces. The model has freedom of translation in three axes. The articular contact characteristics and glenoid track's dimensions according to the literature references were evaluated in 60°, 90° and 120° of abduction, all at the 90° external rotation.

RESULTS

The model's anatomy and physiology were validated. The value of the glenoid track (according to Yamamoto's parameters) was 86% of glenoid length at 90° abduction before loading of forces, and 79% afterwards. The glenoid track at 60°, 90° and 120° of abduction (Omori's parameters) corresponded, respectively, to 71%, 88% and 104% of glenoid length before loading of forces, and 76%, 84% and 103% afterward.

CONCLUSION

The numerical model is suitable for the shoulder articular contact evaluation. The articular contact analysis ratifies the glenoid track concept and contributes to its evolution. This value is influenced by glenohumeral joint forces, which should be considered for the analysis.

LEVEL OF EVIDENCE

Basic Science Study; Computer Modelling.

Anterior Instability: What to Look for

Most first-time anterior glenohumeral dislocations occur as the result of trauma. Many patients suffer recurrent episodes of anterior shoulder instability (ASI). The anatomy and biomechanics of ASI is addressed, as is the pathophysiology of capsulolabral injury. The roles of imaging modalities are described, including computed tomography (CT) and MR imaging with the additional value of arthrography and specialized imaging positions. Advances in 3D CT and MR imaging particularly with respect to the quantification of humeral and glenoid bone loss is discussed. The concepts of engaging and nonengaging lesions as well as on-track and off-track lesions are examined.

Off-track Hill-Sachs lesions do not increase postoperative recurrent instability after arthroscopic Bankart repair with selective Remplissage procedure

PURPOSE

This study aimed to compare clinical outcomes and recurrence rates after arthroscopic Bankart repair with selective Remplissage procedure, between patients with off-track and on-track Hill-Sachs lesions.

METHODS

Patients who underwent arthroscopic Bankart repair with selective Remplissage procedure for recurrent anterior shoulder instability and were followed up for at least 2 years were included. Patients with a glenoid defect greater than 25% were excluded. According to the glenoid track concept, patients were divided into group I (off-track lesions) and group II (on-track lesions). After Bankart repair, an additional Remplissage procedure was performed selectively in patients who sustained engagement of the humeral head. The clinical outcomes and recurrence rates were evaluated.

RESULTS

A total of 193 patients (23 in group I and 170 in group II) were enrolled. No significant differences were found in clinical outcomes (n.s.) or recurrence rates (n.s.) between the two groups, despite larger glenoid defects in group I (group I:17.1 ± 6.1%, and group II:13.0 ± 6.4%, P = 0.003). In all patients, the incidence of off-track lesions was not significantly different according to the occurrence of postoperative recurrence (n.s.), whereas the glenoid defect size showed a significant difference (with recurrence: 17.9 ± 3.9%, and without recurrence: 13.2 ± 6.5%, P = 0.002).

CONCLUSIONS

The presence of an off-track lesion did not alter the clinical outcomes and recurrence rates after arthroscopic Bankart repair with selective Remplissage procedure. The glenoid defect size rather than the presence of an off-track lesion can more reliably predict postoperative recurrence. Arthroscopic Bankart repair with selective Remplissage procedure is considered one surgical option for the treatment of off-track lesions.

LEVEL OF EVIDENCE

III.

The relationship between the glenoid track and the range of shoulder motion: A cadaver study

INTRODUCTION

The concept of the glenoid track has been proposed to evaluate the risk of dislocation. The glenoid track width was demonstrated to be 84% of the glenoid width in cadaveric shoulders and 83% in live shoulders.

HYPOTHESIS

The glenoid track width seems to be affected by the range of motion.

PURPOSE

The purpose of this study was to determine the relationship between the glenoid track and the range of shoulder motion.

METHODS

Ten fresh-frozen cadaveric shoulders were used. The specimen was fixed to a shoulder-positioning device. The anterior rim of the glenoid was marked on the humeral head using a Kirschner wire with the arm in 60° of abduction. This marking was repeated with the arm in (1) horizontal flexion/extension and (2) internal/external rotations (0° to max). The distances from the Kirschner wire markings to the footprint of the rotator cuff tendon were measured.

RESULTS

The greater the angle of the horizontal extension or external rotation, the smaller the glenoid track width, whereas the greater the angle of the horizontal flexion or internal rotation, the greater the glenoid track width. There was a negative relationship between them. The horizontal flexion/extension motion was demonstrated to affect the glenoid track width more than the internal/external rotation motion.

CONCLUSION

The glenoid track width decreased with the increase of horizontal extension. We should consider the range of horizontal extension angle when applying the glenoid track concept in clinical practice.

TYPE OF STUDY

Laboratory study.

Understanding the Hill-Sachs Lesion in Its Role in Patients with Recurrent Anterior Shoulder Instability

PURPOSE OF REVIEW

The purpose of this study is to provide an update to the orthopedic field in regard to treatment of the Hill-Sachs lesion and anterior shoulder instability. The review highlights the most current knowledge of epidemiology, clinical evaluation, and surgical methods used to treat Hill-Sachs lesions. It also details the relevant clinical and surgical findings that have been made throughout the literature in the past couple of years.

RECENT FINDINGS

The most recent literature covering the Hill-Sachs lesion has focused on the relatively new and unexplored topic of the importance of concomitant injuries while treating a humeral head defect. The glenoid track concept has been clinically validated as a method to predict engagement. 3D-CT has become the "gold standard" for Hill-Sachs imaging; however, it has been noted that 3D-MRI produces results that are not significantly different from CT. Also, it has been found that when the arm is in a position of abduction during the primary injury, there is a higher risk of engagement and subsequent dislocation. Recent studies have demonstrated successful results stemming from purely arthroscopic procedures in treating Hill-Sachs lesions. Anterior shoulder instability, specifically the Hill-Sachs lesion, is an area of orthopedic study that is highly active and constantly producing new studies in an attempt of gaining the best outcomes for patients. The past few years have yielded many excellent discoveries, but there is still much more work to be done in order to fully understand the role of the Hill-Sachs lesion in anterior shoulder instability.

The glenoid track: a review of the clinical relevance, method of calculation and current evidence behind this method

In the setting of bipolar bone injury, orthopedic surgeons are currently making use of the glenoid track method to guide surgical management. Using preoperative CT or MR imaging, this method allows the identification of patients who are more likely to fail a primary capsuloligamentous Bankart repair. As the glenoid track method becomes increasingly used in preoperative planning, it is important for the radiologist to become familiar with its concept and method of calculation. This review article aims to concisely summarize the current literature and the clinical implications of the glenoid track method.

Applying the Glenoid Track Concept in the Management of Patients with Anterior Shoulder Instability

PURPOSE OF REVIEW

The purpose of this paper is to evaluate the recent evolution in the treatment of anterior shoulder instability and the dynamic interaction between the glenoid and Hill-Sachs lesion.

RECENT FINDINGS

Through the glenoid track concept, glenoid- and humeral-sided bone loss are evolving away from being approached as separate entities. Recent cadaveric studies have validated the glenoid track concept. Moreover, a recent clinical study has demonstrated a much higher rate of failure after arthroscopic Bankart repair for shoulders that were off track. The glenoid track concept is a useful tool in evaluating patients with anterior shoulder instability. Shoulders that are off track may require more than a simple arthroscopic Bankart, and the addition of a remplissage or bony transfer may be considered.