Clinical outcomes and repair integrity of arthroscopic rotator cuff repair using suture-bridge technique with or without medial tying: prospective comparative study

Rotator cuff tears (RCTs) comprise the majority of shoulder lesions in adult patients. The prevalence of RCTs among the general population is 22.1% and increases with age [1]. Despite widespread use, rotator cuff repair (RCR) surgeries do not always lead to clinically satisfactory outcomes; indeed, the failure rate of RCR is reportedly 40–50% [2‐4]. Rotator cuff reattachment to the bone during RCR is a challenging clinical problem. To address this problem, surgical repair techniques have been continually developed over time in an attempt to reduce re-tear rates and improve functional outcomes. Recently, arthroscopic transosseous-equivalent suture-bridge RCR, namely, the suture-bridge technique (SBT), has been widely used to enhance healing at the site of tendon insertion of the repaired rotator cuff. This repair method involves insertion of a medial row with suture anchors that utilize mattress repairs [5‐8]. However, techniques that employ a knotted medial row of anchors have been suspected to compromise vascular inflow to the healing tendon and increase the risk of type II failure (i.e., medial row failure), which is very difficult to treat [9‐13]. More recently, knotless RCR techniques that involve application of knotless medial anchors, to improve vascular circulation and prevent type II failure, have been introduced [14‐18].

Despite these innovations and documented benefits in a laboratory setting, postoperative clinical and radiological outcomes of newer SBTs, at short- to medium-term follow-up, have been equivocal [14, 18‐20]. Moreover, few studies comparing clinical and radiological outcomes between the conventional and knotless SBT have been reported.

The purpose of this study was to evaluate and compare functional outcomes and repair integrity between arthroscopic conventional and knotless SBT for full-thickness RCTs.

Preoperatively, no significant differences were observed between the groups in the mean UCLA, ASES, Constant, or VAS scores (p = 0.175, 0.111, 0.432, and 0.890, respectively; Table 3). At 1-year follow-up, the average UCLA, ASES, Constant, and VAS scores had improved significantly to 31.1, 83.5, 72.1, and 1.9, respectively, in the conventional SBT group and to 31.7, 84.4, 73.9, and 1.4, respectively, in the knotless SBT group (Table 4). The UCLA, ASES, Constant, and VAS scores improved in both groups after surgery (all p < 0.001); however, there was no significant difference between the two groups at 1-year follow-up (p = 0.434, 0.733, 0.437, and 0.951, respectively; Table 5).

At final follow-up, the average UCLA, ASES, Constant, and VAS scores had improved significantly to 32.5, 88.0, 80.4, and 1.3, respectively, in the conventional SBT group and to 33.0, 89.7, 81.2, and 1.2, respectively, in the knotless SBT group (Table 6). The UCLA, ASES, Constant, and VAS scores improved in both groups after surgery (all p < 0.001), and there were no significant differences between the two groups at 2-year follow-up (p = 0.292, 0.359, 0.709, and 0.636, respectively; Table 7).

The re-tear rate of the repaired rotator cuffs was 16.3% (8/49 shoulders) in the conventional SBT group and 29.2% (14/48 shoulders) in the knotless SBT group; this difference was not significant (p = 0.131). Two types of re-tear patterns were identified in both the conventional and knotless SBT groups: (1) unhealed tendons [2/8 (25%) and 6/14 (42.9%), respectively; Fig. 3] and (2) medially ruptured tendons with a healed footprint [6/8 (75%) and 8/14 (57.1%), respectively; Fig. 4]; different rate of re-tear pattern was statistically insignificant (p = 0.402). No intra- or perioperative complications were noted, and no patient showed neural injury, wound infection, or problems related to the suture anchor.

The re-tear rate was 22.2% (12/54 shoulders) in the Patte stage I and 23.3% (10/43 shoulders) in the stage II; this difference was not significant (p = 1.000). Also, the re-tear rate of the conventional SBT group was 16.1% (5/31 shoulders) in the stage I and 16.7% (3/18 shoulders) in the stage II; this difference was not significant (p = 1.000). The re-tear rate of the knotless SBT group was 30.4% (7/23 shoulders) in the stage I and 28.0% (7/25 shoulders) in the stage II; this difference was not significant (p = 1.000). And there were no significant differences between re-tear rate of the two groups in the Patte stage I and II (p = 0.358 and 0.616).

This study evaluated the clinical and radiographic results of knot-tying and knotless SBTs for RCTs. We applied an SBT without knot-tying to reduce tension overload at the suture-tendon interface of the medial row and the likelihood of medial cuff failure. We hypothesized that the biological advantages inherent to the knotless SBT would result in a higher healing rate than that associated with the conventional knot-tying SBT.

Suture-bridge RCR was introduced to improve the biomechanical outcomes of RCR [5‐7]. It is more convenient to fasten the compromised tendon to the footprint anchor firmly using the suture limbs of the medial suture knots. With the SBT, the mean pressurized contact area between the tendon and the tuberosity insertion footprint has proven superior to that of the conventional double-row technique [6‐8]. The SBT also shows better ultimate-to-load failure outcomes and less gap formation than the double-row technique [6‐8]. This biomechanical superiority of the SBT may contribute, at least in part, to the low rate of structural failure of repaired cuffs. Moreover, double-row RCR, where each suture anchor is tied separately, is a technically demanding and time-consuming procedure [23].

In a study on medial rotator cuff failure after use of the arthroscopic double-row technique, Trantalis et al. [9] posited that the most likely causes of medial cuff failure were tension overload at the suture-tendon interface of the medial row, over-tensioning of the medial repair (resulting from an oblique and retrograde suture path), a relatively large hole in the rotator cuff caused by retrograde suture-passing instruments, and the effect of braided suture materials on their passage through the rotator cuff. In a study on medial rotator cuff failure after arthroscopic SBT, Cho et al. [12] suggested that the most likely causes of medial cuff failure were attempts to pass the tendon at the musculotendinous junction instead of at the tendon portion, which eventually renders the musculotendinous junction weak and vulnerable to re-tear, with an increased likelihood of strangulation, relatively rapid necrosis of the rotator cuff tendon at the medial row, and failure at the musculotendinous junction. To reduce the possibility of strangulation and relatively rapid necrosis of the rotator cuff tendon at the medial row, the type of knots used to secure the medial row, and the amount of tension used to tie them, should be considered carefully [14, 24].

Reducing unnecessary over-tension during RCT repair, developing new techniques that can distribute the load placed on the medial row may be important. Therefore, the knotless SBT may not only restore the footprint contact area of the rotator cuff, but may also reduce tension overload at the suture-tendon interface of the medial row [25, 26]. This may also reduce the likelihood of strangulation and relatively rapid necrosis of the rotator cuff tendon at the medial row [14]. As with arthroscopic double-row RCR, undue tension at the medial row due to use of conventional SBT may play a major role in repair failure [9]. This tension is usually concentrated at the medial row and is rarely exerted on the lateral row [9]. However, in knotless SBT, tension is usually concentrated at the lateral row and rarely at the medial row. Thus, pullout of the suture anchor at the lateral row after RCR may occur with the knotless SBT, particularly in patients with osteoporosis. Insufficient compression by the medial row suture limbs due to suture anchor pullout may compromise the healing of a repaired rotator cuff [27, 28].

The most frequently used portion of the Patte classification is retraction of the supraspinatus tendon in the coronal plane of MRI. The classification has been found to have moderate consent in assessing tear retraction in some reports [29, 30]. It has also been shown to have prognostic factor after RCR [31]. However, there were no significant differences of re-tear rate between Patte stage I and II. These results probably were due to confined tear size as inclusion criteria in this study, so that there was no RCT with Patte stage III. Also, there were no significant differences of re-tear rate between stages in each group. Therefore, there was no correlation between Patte stage and re-tear rate according to repair techniques.

This study had some limitations. First, although all of the US evaluations were performed by an experienced musculoskeletal radiologist, the technique remains examiner-dependent [32]. However, we did not perform the US examination ourselves to avoid surgeon bias [33]. Second, we could not evaluate preoperative muscle atrophy grades due to incomplete MRI data and the so-called Y-shaped view in some cases. Third, although there was no significant difference in the re-tear rate between groups, the likelihood of having a re-tear in the knotless SBT group was almost twice as high as in the conventional group. Therefore, this study might be under-powered to show this difference from the viewpoint of re-tear.

The study also had several strengths. First, the follow-up rate for the functional outcome and radiological evaluations was high (97%). Second, the study was prospective and enrolled homogeneous patients, with respect to tear size, who had full-thickness supraspinatus or infraspinatus tears 1–4 cm in length in the anterior-to-posterior dimension. Thus, the results can be considered reliable. Third, all of the operations were performed by the same surgeon.

The knotless SBT showed comparable functional outcomes to those of conventional SBT in medium-to-large, full-thickness RCTs at short-term follow-up. The knotless SBT had a higher re-tear rate compared with conventional SBT, although the difference was not significant.