Glenoid bone resorption after Bankart repair: finite element analysis of postoperative stress distribution of the glenoid

Inlay structure can improve bone graft stability in the Bristow procedure

BACKGROUND

Compared with the Latarjet procedure, the Bristow procedure has a lower screw-related complication rate but poor bone healing. A modified Inlay Bristow procedure has been reported to significantly improve the bone healing rate, but the biomechanical mechanism is unclear. The aim of this study was to evaluate the biomechanical stability of the bone graft between a modified Inlay Bristow procedure and the classic Bristow procedure.

METHODS

Sixteen left scapula models (Sawbones, Composite Scapula, and fourth generation) were randomly divided into 2 groups (8:8). The bone graft in the first group was fixed with a 3.5 mm screw using the Inlay structure. The bone graft in the second group was fixed with a 3.5 mm screw via the traditional method. The maximum cyclic displacement, ultimate failure load and stiffness were evaluated biomechanically. The failure type was recorded for each model.

RESULTS

Cyclic loading tests demonstrated that the maximum cyclic displacement of the Inlay procedure was significantly smaller (P = .001) than that of the classic procedure. The Inlay Bristow technique resulted in a significantly higher (P = .024) ultimate failure load than the classic Bristow technique. The stiffness of the classic group was 19.17 ± 4.01 N/mm and that of the inlay group was 22.34 ± 5.35 N/mm (P = .232). Failure was mainly due to bone graft fractures through the drill hole or glenoid bone fractures.

CONCLUSION

Inlay Bristow fixation of the bone graft in a Sawbones model provides significantly stronger fixation and better time point zero stability than classic Bristow fixation, suggesting a higher likelihood of graft union.

Arthroscopic Bankart repair with peeling osteotomy of the anterior glenoid rim preserves glenoid morphology

BACKGROUND

A decrease in the glenoid size after arthroscopic Bankart repair (ABR) was common in shoulders without osseous fragments compared with those with osseous fragments. For cases of chronic recurrent traumatic anterior glenohumeral instability without osseous fragments, we have performed ABR with peeling osteotomy of the anterior glenoid rim (ABRPO) to make an intentional osseous Bankart lesion. The aim of this study was to compare the glenoid morphology after ABRPO with it after simple ABR.

METHODS

The medical records of patients who underwent arthroscopic stabilization for chronic recurrent traumatic anterior glenohumeral instability were retrospectively reviewed. Patients with an osseous fragment, with revision surgery and without complete data were excluded. Patients were assigned to 1 of 2 groups: Group A, ABR without peeling osteotomy procedure or Group B, with ABRPO procedure. Computed tomography was performed preoperatively and 1 year after surgery. The size of the glenoid bone loss was investigated by the assumed circle method. The following formula was used to calculate the decreased size of the glenoid: (Δ) = (postoperative size of the glenoid bone loss) - (preoperative size of the glenoid bone loss). The size of the glenoid 1 year after surgery was assessed to determine if it had decreased (Δ > 0%) or not decreased (Δ ≤ 0%) relative to the preoperative size.

RESULTS

This study evaluated 39 shoulders divided into 2 groups: 27 shoulders in Group A and 12 shoulders in Group B. In Group A, postoperative glenoid bone loss was significantly greater than preoperative glenoid bone loss (7.8 ± 6.2 vs. 5.5 ± 5.3, respectively, P = .02). In Group B, postoperative glenoid bone loss was significantly lower than preoperative glenoid bone loss (5.6 ± 5.4 vs. 8.7 ± 4.0, respectively, P = .02). The P value for the interaction of group (A or B) × time (preoperative or postoperative) was 0.001. The decreased size of the glenoid was significantly larger in Group A than in Group B (2.1 ± 4.2 vs. -3.1 ± 4.5, respectively, P = .001). The rate of shoulders in which the size of the glenoid decreased 1 year after surgery relative to the preoperative size was significantly higher in Group A than in Group B (63% [17/27] vs. 25% [3/2], respectively, P = .04).

CONCLUSIONS

The study showed that ABRPO preserved the glenoid size better than simple ABR without a peeling osteotomy procedure.

Three-Dimensional Finite Element Analysis of a Notched Insert Design for Reverse Total Shoulder Arthroplasty to Prevent Scapular Notching

Purpose

Reverse total shoulder arthroplasty (RSA) is an effective treatment option for rotator cuff arthropathy. Scapular notching following RSA remains a major complication and has a high incidence. This finite element analysis (FEA) study provides a future reference for the optimal design of the insert component of RSA. This study aims to clarify the effect of a new design RSA with a notched insert on the range of adduction, scapular notching, and stress variation of its insert component using three-dimensional (3D) FEA.

Methods

3D nominal Grammont-type monobloc RSA implant components are modeled on the sawbones glenohumeral joint. The polyethylene insert is redesigned with notching of the inferior part. The comparison of standard and notched designs was performed by FEA for stress pressure of scapular notching and the degree of adduction. 3D mesh models are created for stress analysis to compare the results between standard and notched inserts for the adduction.

Results

The redesigned notched inserts had an additional ~ 11.2° on adduction and prevented scapular notching. The stress analysis results for the notched insert design were lower than the standard ones (4.7 vs 22.4 Kpa).

Conclusions

Notched insert design of Grammont-type RSA could provide additional adduction with lower stress on the glenoid, leading to less scapular notching. Further experimental and clinical studies on different RSA types are needed to verify this effect.

Study Design

Basic Science Study; Biomechanics and Computer Modeling.

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.

Anterior glenoid rim erosion in the early stage after arthroscopic Bankart repair affects postoperative recurrence

Background

Recent studies reported that anterior glenoid rim erosion can occur in the early period after arthroscopic Bankart repair (ABR) for traumatic anterior shoulder instability. However, it is unknown whether such erosion is a risk factor for postoperative recurrence. This study evaluated risk factors for postoperative recurrence after ABR, specifically aiming to elucidate whether reduction of postoperative glenoid width due to anterior glenoid rim erosion is one of such factors.

Methods

A total of 220 shoulders that underwent ABR alone between 2013 and 2020 were retrospectively investigated. Patient age at surgery, whether the patient was a collision/contact athlete, anchor placement, preoperative glenoid bone defect (%), localization of the Hill-Sachs lesion, and change of glenoid width (%) in the 6 months after surgery were investigated for their statistical relation to recurrence by univariate and multiple logistic regression analysis.

Results

Postoperative recurrence occurred in 32 of 220 shoulders (14.5%). In univariate analysis, being a collision/contact athlete was the only variable with a significant effect on recurrence (odds ratio [OR], 2.555; 95% confidence interval [CI], 1.123-5.814; P = .03). Change of glenoid width reduction was larger in those with recurrence than without recurrence, but the difference was not statistically significant (-7.0 ± 6.6% vs. -5.0 ± 9.3%; P = .14). However, in multivariate logistic analysis, preoperative glenoid bone defect (%) (adjusted unit OR, 1.076; 95% CI, 1.018-1.137; P = .010) and postoperative change of glenoid width (%) (adjusted unit OR, 0.946; 95% CI, 0.900-0.994; P = .028) had a significant influence on postoperative recurrence.

Conclusion

Glenoid width reduction due to anterior glenoid rim erosion after ABR is a risk factor for recurrence.

Bankart Repair With Remplissage Restores Better Shoulder Stability Than Bankart Repair Alone, and Medial or Two Remplissage Anchors Increase Stability but Decrease Range of Motion: A Finite Element Analysis

PURPOSE

To investigate the effects of the number and location of anchors for remplissage on postoperative glenohumeral biomechanics.

METHODS

A biomechanical study was conducted involving finite element model constructed based on data from the intact glenohumeral joint. Seven models were established, including a normal model, a model of Bankart lesion combined with "off-track" Hill-Sachs lesion, a model of Bankart repair alone, and 4 models of Bankart repair with remplissage based on different remplissage anchor numbers and locations. The effects of the number and location of the remplissage anchors on glenohumeral stability were studied through calculation and comparison of (1) the stress and its distribution on the joint capsule, cartilage, labrum and anchors as well as (2) the displacement of the humeral head.

RESULTS

Finite element analysis demonstrated that contact stress on the glenohumeral cartilage decreased when medial or 2 anchors were used and was minimized in the combined repair model with 2 medial anchors. The stress on remplissage anchors was greater when the anchors were placed medially. The humeral head displacement was maximized in the combined lesion model. The combined repair models with 2 medially placed anchors showed the largest slope on the force-displacement curve, indicating the largest strain on the humeral head.

CONCLUSIONS

Based on a finite element analysis, Bankart repair with remplissage restored better shoulder stability compared with Bankart repair alone in the treatment of anterior shoulder instability involving Bankart lesion combined with "off-track" Hill-Sachs lesion. When the anchor for remplissage was medially placed or 2 anchors were used, the stability of the glenohumeral joint increased but with a loss of range of motion.

CLINICAL RELEVANCE

The results of this study will assist in choosing the number and location of anchors for remplissage during shoulder stabilization surgery although with some limitations.

On-the-Edge Anchor Placement May Be Protective Against Glenoid Rim Erosion After Arthroscopic Bankart Repair Compared to On-the-Face Anchor Placement

PURPOSE

This retrospective study aimed to compare the effects of 2 different anchoring placements on glenoid rim erosion after arthroscopic Bankart repair (ABR).

METHODS

Shoulders that underwent ABR from January 2013 to July 2020 were divided into 2 groups according to anchor placement (on-the-face, group F; on-the-edge, group E). We retrospectively calculated the percent change of glenoid width (Δ) on the first postoperative computed tomography scan (CT; performed within 6 months) and second postoperative CT (performed at 6 to 12 months) relative to the width on the preoperative CT and compared percent changes between the 2 groups. Also, we investigated the influence of preoperative glenoid structures (normal, erosion, bony Bankart) and the postoperative recurrence rate.

RESULTS

We examined 225 shoulders in 214 patients (group F, n = 151; group E, n = 74). At first CT, anchoring placement was significantly associated with postoperative decrease of glenoid width (group F, -7.6% ± 7.9%; group E, -0.1% ± 9.7%; P < .0001). The difference between groups F and E was significant in shoulders with a preoperative glenoid defect (bony Bankart, -6.6% ± 8.8% vs 2.5% ± 11.2%, respectively; P < .0001; erosion, -6.6% ± 6.2% vs -2.6% ± 5.3%, respectively; P = .03). In 112 shoulders, CT was performed twice; Δ was -6.9% ± 7.3% in group F (n = 64) and -1.7% ± 10.1% in group E (n = 48; P = .005) at the first CT and -3.2% ± 10.0% and 1.0% ± 10.6% (P = .10), respectively, at the second CT, indicating recovery of glenoid width in both groups. The postoperative recurrence rate in patients with at least 2 years' follow-up was 14.7% in group F and 14.6% in group E.

CONCLUSIONS

In the early stage after ABR, on-the-edge glenoid anchor placement was associated with less glenoid rim erosion than on-the-face anchor placement.

LEVEL OF EVIDENCE

Level III, retrospective comparative trial.

Anterior Shoulder Instability Part II-Latarjet, Remplissage, and Glenoid Bone-Grafting-An International Consensus Statement

PURPOSE

The purpose of this study was to establish consensus statements via a modified Delphi process on the Latarjet procedure, remplissage, and glenoid-bone grafting for anterior shoulder instability.

METHODS

A consensus process on the treatment utilizing 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 technical approaches identified in the statements on the Latarjet procedure and glenoid bone-graft were that a subscapularis split approach should be utilized, and that it is unclear whether a capsular repair is routinely required. Furthermore, despite similar indications, glenoid bone-grafting may be preferred over the Latarjet in patients with bone-loss greater than can be treated with a coracoid graft, and in cases of surgeon preference, failed prior Latarjet or glenoid bone-grafting procedure, and epilepsy. In contrast, the primary indications for a remplissage procedure was either an off-track or engaging Hill-Sachs lesion without severe glenoid bone loss. Additionally, in contrast to the bone-block procedure, complications following remplissage are rare, and loss of shoulder external rotation can be minimized by performing the tenodesis via the safe-zone and not over medializing the fixation.

CONCLUSION

Overall, 89% of statements reached unanimous or strong consensus. The statements that reached unanimous consensus were the prognostic factors that are important to consider in those undergoing a glenoid bone-grafting procedure including age, activity level, Hill-Sachs Lesion, extent of glenoid bone-loss, hyperlaxity, prior surgeries, and arthritic changes. Furthermore, there was unanimous agreement that it is unclear whether a capsular repair is routinely required with a glenoid bone graft, but it may be beneficial in some cases. There was no unanimous agreement on any aspect related to the Latarjet procedure or Remplissage.

LEVEL OF EVIDENCE

Level V, expert opinion.