Mapping of the Inferior Glenohumeral Ligament for Suture Pullout Strength: A Biomechanical Analysis

Background

Suture pullout during rehabilitation may result in loss of tension in the inferior glenohumeral ligament (IGHL) and contribute to recurrent instability after capsular plication, performed with or without labral repair. To date, the suture pullout strength in the IGHL is not well-documented. This may contribute to recurrent instability.

Purpose/Hypothesis

A cadaveric biomechanical study was designed to investigate the suture pullout strength of sutures in the IGHL. We hypothesized that there would be no significant variability of suture pullout strength between specimens and zones. Additionally, we sought to determine the impact of early mobilization on sutures in the IGHL at time zero. We hypothesized that capsular plication sutures would fail under low load.

Study Design

Descriptive laboratory study.

Methods

Seven fresh-frozen cadaveric shoulders were dissected to isolate the IGHL complex, which was then divided into 18 zones. Sutures in these zones were attached to a linear actuator, and the resistance to suture pullout was recorded. A suture pullout strength map of the IGHL was constructed. These loads were used to calculate the load applied at the hand that would initiate suture pullout in the IGHL.

Results

Mean suture pullout strength for all specimens was 61.6 ± 26.1 N. The maximum load found to cause suture pullout through tissue was found to be low, regardless of zone of the IGHL. Calculations suggest that an external rotation force applied to the hand of only 9.6 N may be sufficient to tear capsular sutures at time zero.

Conclusion

This study did not provide clear evidence of desirable locations for fixation in the IGHL. However, given the low magnitude of failure loads, the results suggest the timetable for initiation of range-of-motion exercises should be reconsidered to prevent suture pullout through the IGHL.

Clinical Relevance

From this biomechanical study, the magnitude of force required to cause suture pullout through the IGHL is met or surpassed by normal postoperative early range-of-motion protocols.

Glenohumeral translation during active external rotation with the shoulder abducted in cases with glenohumeral instability: a 4-dimensional computed tomography analysis

BACKGROUND

Although glenohumeral instability is common, the mechanism of instability remains unclear. The purpose of this study was to quantitatively evaluate humeral head translation during active external rotation with abduction in patients with glenohumeral instability by use of 4-dimensional computed tomography scans.

METHODS

Ten patients with unilateral glenohumeral instability with a positive fulcrum test were prospectively included in this study. Sequential computed tomography of bilateral shoulders during active external rotation at 90° of shoulder abduction was performed for 6 seconds at 5 frames per second. The 3-dimensional positions of the humeral head center in the anteroposterior, superoinferior, and mediolateral directions were calculated at 0°, 20°, 40°, 60°, and maximum shoulder abduction-external rotation from the starting position. Translation of the humeral head center from the starting position was evaluated using Dunnett multiple-comparison tests, and the differences between the affected and intact shoulders were assessed using Wilcoxon signed rank tests.

RESULTS

The humeral head center translated posteriorly, inferiorly, and medially during glenohumeral external rotation with the shoulder in the abducted position on the intact side. However, the affected humeral head showed significantly less posterior translation (P = .028), greater inferior translation (P = .047), and less medial translation (P = .037) than the contralateral side.

CONCLUSIONS

This study indicated that dysfunction of the anterior band of the inferior glenohumeral ligament causes decreased posterior, increased inferior, and decreased medial translation of the humeral head during active shoulder abduction-external rotation.

Axillary Nerve Position in Humeral Avulsions of the Glenohumeral Ligament

Background

The axillary nerve is at risk during repair of a humeral avulsion of the glenohumeral ligament (HAGL).

Purpose

To measure the distance between the axillary nerve and the free edge of a HAGL lesion on preoperative magnetic resonance imaging (MRI) and compare these findings to the actual intraoperative distance measured during open HAGL repair.

Study Design

Case series; Level of evidence, 4.

Methods

A total of 25 patients with anterior instability were diagnosed as having a HAGL lesion on MRI and proceeded to open repair. The proximity of the axillary nerve to the free edge of the HAGL lesion was measured intraoperatively at the 6-o'clock position relative to the glenoid face. Preoperative MRI was then used to measure the distance between the axillary nerve and the free edge of the HAGL lesion at the same position. Distances were compared using paired t tests and Bland-Altman analyses.

Results

The axillary nerve lay, on average, 5.60 ± 2.51 mm from the free edge of the HAGL lesion at the 6-o'clock position on preoperative MRI, while the mean actual intraoperative distance during open HAGL repair was 4.84 ± 2.56 mm, although this difference was not significant (P = .154). In 52% (13/25) of patients, the actual intraoperative distance of the axillary nerve to the free edge of the HAGL lesion was overestimated by preoperative MRI. In 36% (9/25), this overestimation of distance was greater than 2 mm.

Conclusion

The observed overestimations, although not significant in this study, suggest a smaller safety margin than might be expected and hence a substantially higher risk for potential damage. We recommend that shoulder surgeons exercise caution in placing capsular sutures in the lateral edge when contemplating arthroscopic repair of HAGL lesions, as the proximity of the nerve to the free edge of the HAGL tear is small enough to be injured by arthroscopic suture-passing instruments.

Arthroscopic autograft reconstruction of the inferior glenohumeral ligament: Exploration of technical feasibility in cadaveric shoulder specimens

Failure of primary arthroscopic Bankart repair in anterior–inferior glenohumeral instability is low, but in some cases revision surgery is required. Revision procedures show good to excellent results but typically are done open and do not respect the anatomical functionality of the joint capsule. The purpose of this cadaveric study was to explore the feasibility of a completely arthroscopic anatomical reconstruction of the inferior glenohumeral ligament using a hamstring autograft.

Is protecting the healing ligament beneficial after immobilization in external rotation for an initial shoulder dislocation?

BACKGROUND

Immobilization in external rotation is one of the treatment options for an initial dislocation of the shoulder. However, it remains unclear how long it takes for a Bankart lesion to heal.

HYPOTHESIS

Protection of a healing Bankart lesion from stretching would promote the healing process and decrease the recurrence rate after an initial dislocation of the shoulder.

STUDY DESIGN

Randomized controlled trial; Level of evidence, 2.

METHODS

This was a multicenter, prospective randomized study. Between January 2005 and August 2009, 109 patients (71 male and 38 female; mean age, 30 years) with an initial traumatic dislocation of the shoulder were enrolled. After 3 weeks of immobilization in external rotation, a shoulder motion restriction band designed to avoid stretching the anteroinferior shoulder capsule was used for 0 weeks (36 patients), 3 weeks (37 patients), or 6 weeks (36 patients). After using the band, patients were allowed to use their shoulders freely, but they were advised to avoid vigorous sport activities for at least 3 months after the injury. Any recurrent dislocation and return to sports were assessed at 2-year follow-up.

RESULTS

Of 109 patients, 90 were followed up for 2 years. The compliance rates were 60% to 72% among the groups (P = .54). The recurrence rate of dislocation was 28% in the 0-week group, 33% in the 3-week group, and 32% in the 6-week group (P = .88) according to the intention-to-treat analysis, and they were a respective 24%, 28%, and 27% according to the per-protocol analysis (P = .95). Based on the sport activity level, the recurrence rates for patients involved in contact sports (7/15, 47%) and those involved in noncontact sports (19/51, 37%) were significantly higher than for those not involved in sport activities (2/24, 8.3%) (P = .0076). Among the 3 groups, there were no significant differences in the recurrence rates. There was no significant difference in the rate of return to sports (P = .39).

CONCLUSION

No difference in the recurrence rate was seen with the use of a shoulder motion restriction band after 3 weeks of immobilization in external rotation after an initial dislocation of the shoulder.