Radiological evaluation of glenoid bone reaction following arthroscopic Bankart repair using all-soft suture anchors

INTRODUCTION

Glenohumeral joint instability is one of the most common orthopedic problems encountered in the current population especially among young males, athletes, and those involved in contact sports.^[1] Anterior dislocation is the most frequent type of shoulder instability accounting for about 90% of the total cases.^[1] Bankart lesion paves the way for recurrent anterior shoulder instability by creating a pocket in front of the glenoid bone of the scapula, allowing the humeral head to frequently dislocate into it.^[2] The surgical management techniques for the repair of the lesion have been constantly evolving since the last century. With the advancement in arthroscopic techniques and instrumentation, minimal invasiveness and increasing scientific evidence revealing similar clinical outcomes between patients undergoing open versus arthroscopic techniques, there has been a significant shift toward the arthroscopic Bankart repair with suture anchors being utilized as the first line of surgical management in recent times. The most significant advantage of the suture anchor method is that the glenohumeral ligament-labrum complex is directly sutured to the glenoid rim, inducing very good healing between the bone and ligament-labrum complex while also allowing detailed evaluation of coexistent intra-articular pathologies.^[3]

There have been many developments in the structure and composition of these glenoid anchors.^[4] Initially, metallic and bio-absorbable anchors were used but soon fell out of practice due to complications arising following their usage. Complications such as chondral damage, articular protrusion, anchor migration, foreign body reactions, and osteolysis which led to decreased bone stock and increased incidence of post-operative glenoid rim fractures paved way for the emergence of a newer type of suture anchor system – “all-soft suture anchors.”

These all-soft suture anchors (ASSAs) offer reduced bone resection due to smaller drill hole compared to classical suture anchors (1.4 mm vs. 3 mm), equivalent clinical results and ultimate load-to-failure as that of solid anchor systems.^[5,6] Some recent researches have shown increasing evidence of osteolysis following the usage of ASSAs with majority being animal studies.^[7] Although all-soft suture anchors offer a wide range of favorable advantages when compared to its counterparts, there are limited sequential studies executed to check for the incidence, prevalence, and time dependence of glenoid bone reactions following the implantation of all-soft suture anchors.

MATERIALS AND METHODS

Radiological evaluation

All patients were advised to undergo NCCT using 128 slice multidetector computed tomography scanner, of their operated glenohumeral region in supine position. The scan was limited to 6–8 cm distance spanning the glenohumeral joint with 1 mm slice thickness. The scan data were displayed through picture archive and communication system and the measurements were standardized to reduce the inter- and intraobserver variability. The DICOM format was imported to RadiAnt DICOM viewer software 2020.2 version and later evaluated for the presence and absence of glenoid bone reactions and further quantified if present.

Tunnel diameter was defined as “the average of the greatest width of the hole measured perpendicular to the direction of suture anchor insertion in axial, sagittal, and oblique coronal planes.” The largest diameter (D) on the axial, oblique coronal, and sagittal image was measured perpendicular to the direction of the anchor and the average of all three diameters was recorded as the width of the tunnel [Figure 1]. Quantification of glenoid bone reactions [Table 1] was graded based on Ruiz Ibán et al.^[8]

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Figure 1:

Morphology of tunnel in different views on computed tomography. (a) Tunnel diameter in the axial plane, (b) Tunnel diameter in the coronal plane, and (c) Tunnel diameter in the sagittal plane.

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Table 1: Quantification of glenoid bone reactions.

Grade 0	Complete resorption
Grade 1	Partial bony defects (or) erosions (Tunnel diameter < original tunnel diameter)
Grade 2	Tunnel dilation (original tunnel diameter < Tunnel diameter < 2 x original tunnel diameter)
Grade 3	Peri anchor cyst formation (tunnel diameter > 2 x original tunnel diameter)

RESULTS

All 15 patients were available for follow-up. There were 12 males and three females patients. Maximum number of patients was observed to be in the early half of third decade of life at the time of follow-up. The mean number of dislocations before surgery was 6 ranging from a minimum of 2 to a maximum of 10. Out of 15 patients, 11 were participating in some sort of sporting activities before surgery [Table 2].

In our study, 6 patients (40%) had Bankart lesion, 4 (26.67%) had bony Bankart, and 5 (33.33%) had Bankart lesion with significant Hill Sachs defect in the pre-operative period. None of the patients had bony Bankart with Hill Sachs defect in our study. A total of 43 all-soft suture anchors (24 single-loaded and 19 double-loaded) were used with three anchors being used for repair in 13 patients and two in two patients. Anterior apprehension test was positive in five patients at the time of first follow-up and positive in two patients at the time of second follow-up visit. Load and shift test was suggestive of normal laxity in 10, grade 1 laxity in 4 and grade 2 laxity in one patient in comparison to contralateral normal shoulder during the first follow-up. None had grade 2 laxity during the second follow-up at the end of 12 months. There was significant improvement in the functional scores (WOSI and ROWE scores) of all patients at the end of our study [Table 3]. All suture anchors were inserted along the 2’o clock to 7’o clock arc for the right (R) side and the 5’o clock to 10’o clock arc on the left (L) side. Tunnel visualized between (R) 2–3’o clock position (L) 10–9’o clock (superior) was assigned tunnel 1, tunnel 2 between (R) 3–5’o clock (L) 9–7’o clock (middle) and tunnel 3 between (R) 5–7’o clock (L) 7–5’o clock (inferior). The mean diameters of tunnels 1, 2, and 3 were calculated to be 1.85, 2.44, and 2.94, respectively, with a standard deviation of 0.91, 1.31, and 1.24, respectively [Table 4]. There was a statistically significant reduction in the diameters of tunnels 1 and 2 in the 2^nd computed tomography (CT) with P-value 0.01 and 0.02, respectively, with P < 0.005 considered statistically significant. No significant difference was found between the diameters of 3^rd tunnel on serial evaluation.

We evaluated the glenoid bone reactions and graded them as per Ruiz Ibán et al.^[8] None of the anchors showed complete resorption, partial erosions were noticed in 14 out of 43 anchors at the first CT evaluation which increased to 21 at the end of 12 months. Tunnel dilation decreased from 26 to 19 at the end of our study. Two peri-anchor cystic changes were identified in the first follow-up which remained the same on subsequent serial imaging [Table 5]. Bone volume remained stable in 2, increased in 12, and decreased in 1 shoulder. A significant improvement (reduction) in the size of the drilled tunnel was observed in both tunnels 1 and 2, but similar results could not be reflected in tunnel 3, which showed a reduction in size on serial imaging but was not statistically significant.

DISCUSSION

The number of patients opting for shoulder surgeries has drastically increased in the past two decades due to the increase in the number of overhead sporting activities, better patient education, and improved diagnostic and surgical techniques. With the advent of shoulder arthroscopy, arthroscopic Bankart repair is considered by many surgeons all over the world to be the preferred method of management of anterior instability. It is minimally invasive, avoids splitting the subscapularis muscle, and provides a detailed evaluation of intra-articular anatomy and pathology, maximal preservation of external rotation and statistically significant reduction in post-operative instability and a higher rate of return to sports and other daily activities.

Arthroscopic repair of recurrent glenohumeral instability by anatomical repair techniques has been shown to be clinically equivalent to open techniques in the long term.^[9,10] Improvement in the surgical instruments, implants, and techniques has paved the way for the increase in the consideration of these procedures as the first-line management in patients presenting with recurrent anterior instability with non-significant glenohumeral bone loss.

Arthroscopic techniques have evolved from the usage of metallic staples and bio-degradable tacks to the recent introduction of suture anchors. All-soft suture anchors are less invasive than standard implants. These are based on ultra-high molecular weight polyethylene.^[11] They minimize hardware-related complications and reduce the incidence of suture-induced arthritic changes. The tunnel drilled in the glenoid bone for anchor insertion is significantly smaller than that required for a classical suture anchor (1.4 mm vs. 3 mm), thereby reducing the risk of glenoid rim fractures and anchor pull-out.^[12]

We evaluated a total of 43 all-soft suture anchors in 15 patients. No anchor showed complete resorption in both the 1^st and 2^nd CT studies. There was an increased conversion rate from grade 2 (tunnel dilatation) to grade 1 (partial erosion) at the end of our follow-up study, as visualized in the 2^nd CT study at the end of 12 months. A total of three anchors in three patients showed grade 3 reaction (cystic change) at the time of 1^st CT scan (6^th month) which remained constant at the end of our 2^nd CT study. Two out of these three patients reported a recurrence of instability after the study period and had to undergo a revision bone block procedure (Latarjet procedure) for the same.

No anchor inserted on the anterior aspect (2–3’o clock) position showed grade 3 changes. One anchor in the anteroinferior (3–5’o clock) and two anchors in the posteroinferior (5–7’o clock) position showed grade 3 changes. Out of these three, two were single-loaded, and one was double-loaded. Lee et al.^[7] demonstrated the effect of position and angle of insertion on bio-mechanical effects of all-soft suture anchors in arthroscopic Bankart repair. He reported increased stiffness and greater ultimate to-load failure for anchors implanted at the 2:30’ o clock position in comparison to the 4 and 5:30’ o clock positions regardless of the angle of suture anchor insertion. The micromotion resulting during anchor deployment while insertion and lower ultimate load to failure in the inferiorly placed anchors can explain the increased incidence of grade 3 changes in this position. Persistent micromotion may lead to tunnel dilation and peri-anchor cyst formation, further increasing the stress on other anchors, thereby influencing similar bone reactions in them, eventually resulting in failure of the repair.

Glenoid bone loss increased in one patient and remained stable in two other patients on subsequent follow-ups. Out of which, two patients showed grade 1 instability and positive apprehension during their clinical evaluation. Yamamoto et al.,^[13] showed a decrease in glenoid bone width following arthroscopic repair, more so in patients with soft-tissue Bankart (57%) as compared to Bony Bankart (15%) which was further validated by Hirose et al.^[14] Shaha et al.^[15] reported a bone loss of more than 13.5% corresponded to sub-critical bone loss that influenced post-operative outcomes. One patient in our study had a bone loss more than the critical limit and reported persistent instability before and after surgery (grade 3 in pre-operative and grade1 in post-operative period). All-soft suture anchors were associated with some changes in the glenoid bone following insertion but showed a tendency toward healing on serial evaluation in majority of cases and were associated with lower hardware-related complications than previous generation anchors. The results of our study could be compared to that of Ruiz Ibán et al.,^[8] Tompane et al.,^[16] and Willemot et al.,^[17] who reported an increased incidence of tunnel dilation following the usage of ASSAs [Table 6]. The incidence of grade 3 cystic changes in the glenoid bone was less but their occurrence could not be ruled out. None of the above-mentioned studies performed a serial follow-up radiological evaluation of glenoid bone reactions.

CONCLUSION

We observed that the overall performance of all-soft suture anchors in arthroscopic Bankart repair was comparable to previous generation suture anchors in terms of clinical and functional outcomes and was associated with a lower complication rate than metallic and bio-degradable anchors. However, we would advocate for further long-term follow-up studies of these anchors in the future with a larger non-randomized cohort of patients.