Editorial Commentary: Computed Tomography-based Analysis of the Arthroscopic Latarjet Procedure Suggests Graft Positioning Is More Variable than Expected

The Influence of Glenoid Bone Loss and Graft Positioning on Graft and Cartilage Contact Pressures After the Latarjet Procedure

BACKGROUND

Glenohumeral joint contact loading before and after glenoid bone grafting for recurrent anterior instability remains poorly understood.

PURPOSE

To develop a computational model to evaluate the influence of glenoid bone loss and graft positioning on graft and cartilage contact pressures after the Latarjet procedure.

STUDY DESIGN

Controlled laboratory study.

METHODS

A finite element model of the shoulder was developed using kinematics, muscle and glenohumeral joint loading of 6 male participants. Muscle and joint forces at 90° of abduction and external rotation were calculated and employed in simulations of the native shoulder, as well as the shoulder with a Bankart lesion, 10% and 25% glenoid bone loss, and after the Latarjet procedure.

RESULTS

A Bankart lesion as well as glenoid bone loss of 10% and 25% significantly increased glenoid and humeral cartilage contact pressures compared with the native shoulder (P < .05). The Latarjet procedure did not significantly increase glenoid cartilage contact pressure. With 25% glenoid bone loss, the Latarjet procedure with a graft flush with the glenoid and the humerus positioned at the glenoid half-width resulted in significantly increased humeral cartilage contact pressure compared with that preoperatively (P = .023). Under the same condition, medializing the graft by 1 mm resulted in humeral cartilage contact pressure comparable with that preoperatively (P = .097). Graft lateralization by 1 mm resulted in significantly increased humeral cartilage contact pressure in both glenoid bone loss conditions (P < .05).

CONCLUSION

This modeling study showed that labral damage and greater glenoid bone loss significantly increased glenoid and humeral cartilage contact pressures in the shoulder. The Latarjet procedure may mitigate this to an extent, although glenoid and humeral contact loading was sensitive to graft placement.

CLINICAL RELEVANCE

The Latarjet procedure with a correctly positioned graft should not lead to increased glenohumeral joint contact loading. The present study suggests that lateral graft overhang should be avoided, and in the situation of large glenoid bone defects, slight medialization (ie, 1 mm) of the graft may help to mitigate glenohumeral joint contact overloading.

How to Fashion the Bone Block for Reconstruction of the Glenoid in Anterior and Posterior Instability

BACKGROUND

Glenoid restoration techniques to address glenohumeral instability-induced anterior and posterior glenoid bone loss (AGBL and PGBL) often require reconstruction, but best-fit bone block (BFBB) modeling has not been developed.

PURPOSE

To provide glenoid bony reconstruction models for anterior and posterior instability of the shoulder using a bone loss instability cohort with high-fidelity 3-dimensional (3D) imaging.

STUDY DESIGN

Cross-sectional study; Level of evidence, 3.

METHODS

We reviewed consecutive patients indicated for operative stabilization who had posterior glenohumeral instability and suspected GBL who underwent 2-dimensional (2D) computed tomography (CT). Patients were matched by sex, laterality, and age to patients who underwent operative stabilization of anterior glenohumeral instability. Mimics software was used to convert all 2D CT scans into 3D models of the scapula. A BFBB model was designed to digitally reconstruct GBL and was used to predict the amount, anatomic configuration, and fixation configuration of bony reconstruction required in AGBL and PGBL.

RESULTS

The study included 30 patients with posterior instability and 30 patients with anterior instability; the participants' mean ± SD age was 28.8 ± 8.15 years (range, 16.0-51.0 years). Mean surface area of AGBL was 24.9% ± 7.7% (range, 14.7%-39.1%). Mean BFBB dimensions to reconstruct the anterior glenoid were determined to be a superior-inferior length of 23.9 ± 4.2 mm, anterior-posterior width of 6.4 ± 2.4 mm, and height of 1 cm. Mean angle of AGBL bone block interface relative to glenoid to reconstruct the native concavity was 79.4°± 5.9°. For PGBL, the mean surface area was 9.2% ± 5.6% (range, 3.0%-26.3%). Mean BFBB dimensions to reconstruct the posterior glenoid were a superior-inferior length of 21.9 ± 3.4 mm, width of 4.5 ± 2.3 mm, and height of 1 cm. The mean angle of PGBL bone block interface relative to the glenoid to reconstruct the native concavity was 38.6°± 14.3°. Orientation relative to the vertical glenoid axis was 77.2°± 13.8° in anterior reconstructions versus 105.9°± 10.9° in posterior reconstructions.

CONCLUSION

Patients with anterior instability required a more rectangular BFBB with a bone block-glenoid interface angle of 79°, whereas patients with posterior instability required a more trapezoidal, obtusely oriented BFBB with a bone block-glenoid interface angle of 39°. BFBBs for either AGBL or PGBL can be effectively designed, and their size and/or shape can be predicted based on approximate percentage of GBL.

Long-term Results of the Open Latarjet Procedure for Recurrent Anterior Shoulder Instability in Patients Older Than 40 Years

BACKGROUND

Subgroup analyses of the Latarjet procedure have suggested that age over 40 years is a risk factor for dislocation arthropathy.

PURPOSE

To analyze long-term results of the open Latarjet procedure for recurrent anterior shoulder dislocation in patients at least 40 years of age.

STUDY DESIGN

Case series; Level of evidence, 4.

METHODS

A total of 39 consecutive patients (40 shoulders) with a mean age of 48 years (range, 40-66 years) at surgery were evaluated at a mean follow-up of 11.0 years (range, 8-16 years). Of these, 15 patients (38%) had undergone previous soft tissue stabilization surgery. Long-term results were assessed clinically and radiographically, including computed tomography scanning at final follow-up.

RESULTS

No recurrence of dislocation was noted. Subluxation had occurred in 3 patients (8%), and apprehension persisted in 5 patients (13%). The total Walch-Duplay score averaged 89 points at the final follow-up, and the mean Subjective Shoulder Value (60%-91%) had improved significantly (P < .001). In total, 36 patients rated their result as excellent, 3 as good. Further, 6 patients (15%) underwent joint-preserving reoperation, and 1 patient (3%) had reverse total shoulder arthroplasty for severe dislocation arthropathy. Dislocation arthropathy was severe in 14 patients (37%) and had progressed by at least 2 grades in 17 patients (45%). Patients with severe dislocation arthropathy had already shown degenerative changes preoperatively as opposed to those who ultimately had no or moderate dislocation arthropathy (n = 24) (P < .001). Progression of dislocation arthropathy was associated with lateral (>1 mm) graft positioning (P < .001) and older age at surgery (r = 0.58; P < .001).

CONCLUSION

The open Latarjet procedure for recurrent anterior shoulder instability in patients older than 40 years reliably restores stability and leads to high patient satisfaction. This procedure is, however, associated with a substantial rate of advanced but clinically mild symptomatic dislocation arthropathy, which is associated with the degree of preoperative joint degeneration, older age at surgery, and lateral graft placement.