Glenoid fracture after arthroscopic Bankart repair: case series and biomechanical analysis

How many anchors to use in arthroscopic Bankart repairs? A biomechanical study of postage-stamp glenoid fractures

BACKGROUND

Deciding how many anchors to use in a Bankart repair is challenging because of the desire to enhance stability while avoiding a postage-stamp fracture of the glenoid rim.

METHODS

This controlled laboratory study investigated load to fracture of the anterior glenoid rim after drilling holes of varying number and diameter and inserting anchors of 2 different types and sizes, with and without perforation of the medial cortex of the glenoid, creating postage-stamp fractures using a metallic humeral head that was compressed against the anterior glenoid rim. A destructive model with a servohydraulic load frame was used to test 46 synthetic scapulae with compressive strength and elastic modulus similar to that of a human glenoid. Load to fracture of the intact glenoid was compared with groups with a varying number of anchor holes of different diameters, with anchors of different sizes and types, and with anchors perforating or not perforating the glenoid medial cortex. The percentage of force to fracture an intact specimen was used to identify relative risk of fracture: low risk >75%, moderate risk 75%-50%, and high risk <50% of intact load.

RESULTS

The load to fracture of intact glenoids was 1276 ± 42 N. Loads decreased linearly as the number of holes drilled on the glenoid rim increased. Compared with the 1.6-mm group, the 3.0-mm group had significantly lower glenoid rim strength in specimens with 4, 5, and 7 holes (P = .013, .032, and .045, respectively). All-suture anchors in 1.6-mm holes did not alter the glenoid rim strength, and up to 5 anchors were associated with low risk of fracture. Load to fracture was significantly higher with 3.0-mm rigid core bioabsorbable anchors with 4 anchors (1081 ± 6 N) compared with the 4-hole condition (838 ± 107 N; P = .033). Perforating the glenoid medial cortex with five 1.6-mm anchors significantly weakened the glenoid rim to 58% of intact (P = .012). Perforating the medial cortex weakened the glenoid rim to 52% and 42% (P < .001 for both) of intact in the 3.0-mm 4-anchor and 5-anchor constructions, constituting moderate and high risk of fracture, respectively.

CONCLUSION

Up to five 1.6-mm all-suture anchors and four 3.0-mm bioabsorbable rigid-core anchors were associated with low risk of fracture of the glenoid rim. Smaller diameter all-suture anchors best preserved structural integrity of the glenoid rim, whereas tunnel enlargement and perforation of the glenoid medial cortex were associated with moderate or high risk of a postage-stamp fracture.

Recurrent Instability after Arthroscopic Glenoid Labral Repair with a Minimum of Three Points of Fixation: Do the Number of Anchors or Fixation Points Correlate to Outcomes?

INTRODUCTION

The goal of this study was to evaluate the recurrence rate of instability following arthroscopic Bankart repairs in regard to the number and types of fixation utilized. A Bankart lesion is a tear in the anteroinferior capsulolabral complex within the shoulder, occurring in association with an anterior shoulder dislocation. These injuries can result in glenoid bone loss, decreased range of motion, and recurrent shoulder instability. Successful repair of these lesions has been reported in the literature with repair constructs that have three points of fixation. However, the definition of "one point of fixation" is yet to be fully elucidated.

MATERIALS AND METHODS

A consecutive series of arthroscopically repaired Bankart lesions were evaluated pertaining to the points of fixation required to achieve shoulder stability. This included the number, position, and types of anchors used. Patients consented to complete a series of surveys at a minimum of two years postoperatively. The primary outcome was to determine recurrent instability via the UCLA Shoulder Score, the ROWE Shoulder Instability Score, and the Oxford Shoulder Score. A secondary outcome included pain on a Visual Analog Scale (VAS).

RESULTS

There were 116 patients reviewed, 46 patients achieved three points of fixation in their surgical repair via two anchors and 70 patients achieved a similar fixation with three or more anchors. There was no significant difference in the mean age, gender, or body mass index (BMI). Patients receiving two anchors demonstrated recurrent instability 8.7% of the time (4 of 46 patients). Patients who received three or more anchors demonstrated recurrent instability 8.6% of the time (6 of 70 patients). Overall, there was no statistical significance between the number/types of anchors used. Between the two cohorts, there was no statistically significant difference found between VAS, ROWE, UCLA, and Oxford Scores. There was a significant difference in pain reported on the VAS scale with an average VAS score of 0.43 versus 2.5 in those without and with recurrent instability respectively.

CONCLUSION

Contention still exists surrounding the exact definition of "a point of fixation" in arthroscopic Bankart repairs. Three-point constructs can be created through a variety of combinations including anchors and sutures, ultimately achieving the goal of a stable shoulder.

"Postage Stamp" Fractures: A Systematic Review of Patient and Suture Anchor Profiles Causing Anterior Glenoid Rim Fractures After Bankart Repair

PURPOSE

To systematically review patient and technical risk factors for anterior glenoid rim fractures through suture anchor points (i.e. "postage stamp") after arthroscopic Bankart repair.

METHODS

An independent, duplicate search of Embase, Medline, and Web of Science databases, in addition to the past 5-year annual meeting abstracts of several prominent shoulder meetings, was conducted according to R-AMSTAR and Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines to identify English-language studies reporting this complication.

RESULTS

A screen of 2,833 studies yielded 6 for inclusion herein. Data across 43 patients, aged 14 to 61 years (mean 24.4), 5% female, and who were followed for 4 to 108 months postoperatively, were reviewed. Only 1 of 6 studies (n = 2) reported postage stamp fracture in female patients. Median time from initial surgery to fracture ranged from 12 to 24 months. Five of 6 studies (n = 32) reported a median age at initial surgery of 25 years or younger (range 17-35). Four of 6 studies (n = 30) reported fracture mostly after sport involvement. All studies (n = 35) reported initial fixation with a median of 3 anchors or more, 3 of 5 studies (n = 26) reported fracture entirely after conventional knot-tying anchors, and 5 of 6 studies (n = 24) reported more fractures after absorbable suture anchor use. Fractures occurred entirely through anchor holes in 5 of 6 studies (n = 29) and mostly after osteolysis in 3 of 4 studies (n = 19). Management strategies after fracture included revision arthroscopic Bankart repair or open Bristow/Latarjet procedures.

CONCLUSION

Postage stamp fractures were reported frequently in patients who were male, age 25 years or younger, and participants in sporting activities and in fractures initially stabilized with 3 or more anchors or conventional knot-tying anchors or that experienced osteolysis around anchor sites.

LEVEL OF EVIDENCE

Level IV, systematic review of level III and IV studies.

Editorial Commentary: Is Arthroscopic Bankart Repair Using Suture Anchors on the Glenoid Appropriate Treatment for Traumatic Anterior Shoulder Instability?

Fracture of the anterior glenoid rim along the sites of suture anchor insertion is not rare after arthroscopic Bankart repair for traumatic anterior shoulder instability. In addition to the influence of the number, type, and size of the suture anchors, placing multiple anchors in a linear arrangement might impose excessive stress on the surrounding bone, leading to critical loss of osseous integrity and glenoid fracture. Although highly active young male collision or contact athletes are most at risk, such fractures sometimes occur after relatively minor trauma at a long interval after surgery, suggesting persistent impairment of bone quality. In patients with postoperative recurrence of instability, detailed examination using computed tomography is recommended.

Femoral fixation strength following soft-tissue posterolateral corner reconstruction using fibular-based technique: Biomechanical analysis of four techniques in normal and low-density synthetic bone

BACKGROUND

Optimal femoral fixation of soft-tissue grafts has been described for anterior cruciate ligament reconstruction. Posterolateral corner reconstruction differs from ACL reconstruction in two ways: (a) soft-tissue fixation into the femur requires two tails and (b) the line of force is different. Our purpose was to determine the optimal femoral fixation of soft-tissue grafts during posterolateral corner reconstructions. We hypothesized that interference screw fixation is the strongest technique in normal-density lateral femoral condyle, whereas, cortically-based fixation techniques are stronger methods in low-density lateral femoral condyle.

METHODS

We evaluated elongation during cyclic loading, yield load, peak load-to-failure, and stiffness of four soft-tissue graft femoral fixation methods during posterolateral corner reconstruction. Our model included bovine flexor tendons and contoured synthetic bones. Grafts were secured to the lateral epicondyle in normal- or low-density bone models using spiked washer, button, interference screw, or button and interference screw. Five specimens for each were tested in each bone density. Analysis of variance using Tukey-Kramer adjustment for multiple hypothesis testing was used. Six cadaver bones whose density was analyzed using computerized tomography scan quantitation were tested using interference screw fixation.

RESULTS

No method produced significantly stronger yield load or peak load-to-failure in normal-density bone. In low-density bone, cortically-based methods produced significantly higher yield load or peak load-to-failure. Yield load or peak load-to-failure was significantly higher in normal-density bone when using spiked washer or interference screw fixation.

CONCLUSION

No femoral fixation method tested produced superior yield load or peak load-to-failure. Spiked washer and interference screw fixation are inferior fixation methods in low-density bone.

CLINICAL RELEVANCE

For fibular-based posterolateral corner reconstructions, all fixation methods tested are acceptable in high-density bone, while cortical fixation methods should be considered in low-density bone.