Biomechanical comparison of screw-in suture anchor-suture combinations used for Bankart repair

Biomechanical Studies for Glenoid Based Labral Repairs With Suture Anchors Do Not Use Consistent Testing Methods: A Critical Systematic Review

PURPOSE

The purpose of this systematic review was to investigate variability in biomechanical testing protocols for laboratory-based studies using suture anchors for glenohumeral shoulder instability and SLAP lesion repair.

METHODS

A systematic review of Medline, Embase, Scopus, and Google Scholar using Covidence software was performed for all biomechanical studies investigating labral-based suture anchor repair for shoulder instability and SLAP lesions. Clinical studies, technical notes or surgical technique descriptions, or studies treating glenoid bone loss or capsulorrhaphy were excluded. Risk of bias (ROB) was assessed with the ROBINS-I tool. Study quality was assessed with the Quality Appraisal for Cadaveric Studies. Heterogeneity was assessed with the I² statistic.

RESULTS

A total of 41 studies were included. ROB was serious and critical in 27 studies, moderate in 13, and low in 1; 6 studies had high quality, 21 good quality, 10 moderate quality, 2 low quality, and 2 very low quality. Thirty-one studies used and 22 studies included cyclic loading. Angle of anchor insertion was reported by 33 studies. The force vector for displacement varied. The most common directions were perpendicular to the glenoid (n = 9), and anteroinferior or anterior (n = 8). The most common outcome measures were load to failure (n = 35), failure mode (n = 23), and stiffness (n = 21). Other outcome measures included load at displacement, displacement at failure, tensile load at displacement, translation, energy absorbed, cycles to failure, contact pressure, and elongation.

CONCLUSION

This systematic review demonstrated a clear lack of consistency in those cadaver studies that investigated biomechanical properties after surgical repair with suture anchors for shoulder instability and SLAP lesions. Testing methods between studies varied substantially with no universally applied standard for preloading, load to failure and cyclic loading protocols, insertion angles of suture anchors, or direction of loading. To allow comparability between studies standardization of testing protocols is strongly recommended.

Anchor Hole Placement for Bankart Repairs and Its Interaction With Variable Size Hill–Sachs Defects-Minimizing Risk of Glenoid Rim Fractures

As the use of glenoid suture anchors in arthroscopic and open reconstruction, for instability after Bankart lesions of the shoulder, increases, an emerging problem has been the incidence of glenoid rim fractures through suture drill holes. Very little is known regarding the effect of the Hill–Sachs lesion on the glenoid's susceptibility to fracture and how drill hole location can further affect this. This study used finite element modeling techniques to investigate the risk of fracture of the glenoid rim in relation to variable sized Hill–Sachs defects impacting on the anterior glenoid edge with suture anchor holes placed in varying positions. The distribution of Von Mises (VM) stresses and the factor of safety (FOS) for each of the configurations were calculated. The greatest peak in VM stresses was generated when the glenoid was loaded with a small Hill–Sachs lesion. The VM stresses were lessened and the FOS increased (reducing likelihood of failure) with increasing size of the Hill–Sachs lesion. Placement of the suture drill holes at 2 mm from the glenoid rim showed the highest risk of failure; and when combined with a medium sized Hill–Sachs lesion, which matched the central line of the drill holes, a potentially clinically significant configuration was presented. The results of this study are useful in assisting the surgeon in understanding the interaction between the Hill–Sachs lesion size and the placement of suture anchors with the purpose of minimizing the risk of subsequent rim fracture with new injury.

Biomechanical evaluation of knotless anterior and posterior Bankart repairs

PURPOSE

The value of modern tape-like suture materials and the influence of the number of anchors inserted for arthroscopic Bankart repairs compared to the intact state have yet to be investigated. It was hypothesised: (1) suture-tape repairs will show higher biomechanical strength than common suture repairs, (2) four anchors will be stronger than three, and (3) the strength of the native capsulolabral complex will be greater than repairs.

METHODS

Six matched-paired cadaveric shoulders received Bankart lesions/reconstructions and three underwent intact state testing. Anteroinferior repairs compared suture and suture-tape repairs using three anchors, while posteroinferior repairs compared three and four suture anchors using common sutures. An established testing protocol was run for biomechanical testing.

RESULTS

There was no significant difference in the maximum loads, loads at 2 mm displacement, stiffness or energy between repair groups or between repairs and the intact state (n.s.). However, failure modes were different: 16/24 (66.7%) of the repair groups showed glenoid labrum detachment compared to 2/12 (16.7%) within the intact state group (P = 0.012).

CONCLUSIONS

While biomechanical parameters of repairs and intact states showed equivalence, failure-mode analysis reaffirms previous findings that capsulolabrum complex refixation is weaker than the native attachment. Therefore, in daily clinical practice, type of suture is secondary and insertion of a fourth anchor will be unlikely to add strength but may confer additional risk and cost.

Suture anchor fixation of bony Bankart fractures: comparison of single-point with double-point "suture bridge" technique

BACKGROUND

As an alternative to the standard single-point suture-anchor technique, a suture-bridge technique has been described for the treatment of bony Bankart fractures. There is, however, little evidence supporting one technique over the other. Purpose/

HYPOTHESIS

To compare the failure strength, fixation stability, and loading mechanics of the 2 techniques for the fixation of bony Bankart fractures. We hypothesized that use of the double-point suture-bridge technique would result in superior strength and fixation stability because of the increased compression and contact area between the bony fragment and glenoid fracture site.

STUDY DESIGN

Controlled laboratory study.

METHODS

A total of 16 shoulders (8 pairs) were tested with an intact glenoid, after creation of a 15% bony Bankart fracture, and after fragment fixation using a single-point or suture-bridge technique. Paired specimens were randomly assigned to each technique. Cyclic progressive loading was applied via a materials testing machine to the glenoid concentrically and eccentrically according to a staircase protocol. Failure strength, fragment displacement, glenoid strain load transfer, and contact area were quantified.

RESULTS

No significant differences in failure strength were found between the single-point and suture-bridge techniques (mean strength, 74 ± 28 N vs 77 ± 56 N, respectively; P = .91). Additionally, no significant differences were found for glenoid load transfer (P ≥ .318) and glenohumeral joint contact (P = .357) between the 2 techniques. Centralized loading, however, produced significant differences in fragment displacement at 5, 150, and 200 N (P ≤ .045), with the single-point technique permitting greater fragment displacement in all cases (0.06-0.28 mm). Similarly, eccentric loading caused significantly greater fragment displacement with the single-point technique at ≥25 N compared with the suture-bridge technique (mean range, 0.38-0.63 mm vs 0.14-0.19 mm, respectively; .009 ≤ P ≤ .048).

CONCLUSION

Single-point and suture-bridge techniques for the fixation of bony Bankart fragments have equivalent failure strengths and load transfers. The suture-bridge technique does provide statistically greater initial fracture fragment stability; however, the clinical implications of this are presently unknown.

CLINICAL RELEVANCE

This study will aid in the selection of the optimal repair technique for bony Bankart fractures by providing important insights into the quality of initial fixation and ultimate strength.