A novel arthroscopic transosseous suture-button fixation technique for anterior glenoid fractures

This study evaluated the clinical and radiological results of a new transosseous suture-button fixation technique for anterior glenoid fractures. From March 2017 to May 2021, 23 patients with anterior glenoid fractures were treated with the new technique. Demographic data, active shoulder function, and several shoulder scores were evaluated after a minimum of 6 months. Fracture reduction and button placement were assessed via computed tomography, while fracture healing and onset or progression of glenohumeral osteoarthritis were evaluated with X‑rays. Overall, 57% of the patients had relevant concomitant intra-articular injury. Clinical follow-up was performed for 22 patients (19 male, 3 female) at 15 months (6.0–34.5) after surgery. The average Constant Score was 83.2 ± 16.7 points (93.4% ± 18.8% vs. the contralateral side), the Rowe Score, 90.7 ± 10.4 points, the Melbourne Instability Shoulder Score (/100), 88.3 ± 14.5 points, the Western Ontario Shoulder Instability Index (%), 82.9 ± 16.7, and the Subjective Shoulder Value (%), 86.9 ± 16.1. Average range of motion was 171.4 ° ± 22.7 ° of flexion (contralateral side, 180 ° ± 0 °; p = 0.11) and 170.5 ° ± 23.6 ° of abduction (contralateral side, 179.6 ± 2.1; p = 0.07). No complications occurred and no revision surgery was required. The postoperative step-off of the glenoid averaged 1.55 ± 1.05 mm (0–4 mm). Radiological follow-up of 19 patients showed fracture consolidation in all cases, without secondary dislocation of the fracture or of heterotopic ossification. There was no sign hardware impingement or dislocation. There was new-onset osteoarthritis in 3 cases (15.8%). We found no correlation between the step-off and radiological signs of osteoarthritis. Anterior glenoid fractures were treated safely and reproducibly with the novel arthroscopic double-button-suture technique, but long-term results are still needed.


Introduction
Anterior glenoid fractures mainly result from anterior shoulder dislocations and can lead to chronic instability and glenohumeral osteoarthritis. The prevalence of 16% of bony lesions of the anterior glenoid in first-time shoulder dislocation has been reported to be 16% [10]. While conservative treatment can be advocated for undisplaced fractures with centered humeral head, surgery has usually been recommended for dislocated fractures (> 4 mm) with a decentered joint or for cases with relevant concomitant injuries [8,13]. Open surgical procedures using screw fixation have long been the standard of care despite the extensive soft tissue trauma of open approaches including detachment of the subscapularis tendon [22]. Thus, therapy has shifted to arthroscopic methods applying screw osteosynthesis or anchor refixation techniques resulting in lower complication and revision rates [4]. However, these methods remain challenging due to several potential intra-and postoperative pitfalls: Screw osteosynthesis requires an anterior approach endangering the neurovascular structures and penetrating through the subscapularis muscle [23,25]. The other methods applying suture anchors placed along the fracture site are usually not adequate for larger fractures. Also, the linear placement of anchors has been reported to be associated with secondary fractures of the glenoid or irritation of the joint due to non-absorbable sutures [9,16].
Thus, we have developed an all-arthroscopic transosseous technique that: -(a.) Uses a glenoid drill guide placed over the posterior portal. -(b.) Applies a double-button-suture construct placed extra-articularly for refixation.
This recently described procedure avoids the risks of open reconstruction while it still appears to provide adequate stabilization for large fragments [27]. Other similar case reports have confirmed the reproducibility of this method [1,5]. However, clinical outcome data are lacking to date. The aim of this study was to evaluate the results of this novel arthroscopic technique for anterior glenoid fractures with a minimum follow-up of 6 months.

Surgical procedure
The system utilized for this procedure (Smith&Nephew Co., London, UK) was developed originally for chronic instabilities by both Ettore Taverna for arthroscopic glenoid augmentation with tricortical iliac crest [26] and by Pascal Bouileau for arthroscopic coracoid transfer [3]. The respective arthroscopic surgery for glenoid fractures has been previously described by our group [27]. In summary, the procedure is performed in the beach-chair position with an en-face view on the glenoid with the arthroscope placed in the anterolateral portal. Several instruments are used through two anterior portals (in the rotator interval) for fracture reduction. Then, the anterior hook-end of the glenoid guide (. Fig. 1) is inserted through the posterior portal and placed anteriorly parallel to the glenoid. It then captures the anterior edge of the anterior fragment under the hook. Two bullets are placed on the scapula neck over the glenoid guide through an additional posteromedial skin incision (. Fig. 2). A 2.8mm cannulated drill is placed through each bullet and advanced under power until exiting from the anterior aspect of the anterior fragment. Each drill will be 5 mm below the cortical edge of the glenoid surface. After removal of the glenoid guide, the inner part of the drills is removed posteriorly leaving the cannulated part in place (. Fig. 3). Usually, only one pair of endobuttons was placed and therefore the cranial drill was removed in most cases. A flexible looped guide wire is then passed through the remaining cannulated drill from posterior to anterior and retrieved through the anterior portal.
The drill can now also be removed, finally leaving only the looped guide wire in the lower drill tunnel.
With the guide wire, all four strands of the endobutton-suture-fixation device (. Fig. 4a) are shuttled into the anterior portal, through the glenoid and out of the posteromedial incision. Thus, the anterior  Fig. 5a). b Intraoperative view: The inferior drill has been removed and the endobutton already placed anteriorly (marked with asterisk). The cannulated part of the upper drill is still in place (marked with plus sign), and a flexible looped guide wire is just passed through it from posterior to anterior and retrieved through the anterior portal with a grasper. In all but two cases, only one pair of endobuttons was placed and therefore the cranial drill was removed. c  Fig. 4b). The posterior strands are knotted over a posterior endobutton, which is then advanced until it sits firmly against the posterior face of the scapular neck. The construct is locked with a suture tensioner and finally a standard knot pusher. The capsulolabral ring can be reattached additionally on the glenoid rim applying a standard arthroscopic soft-tissue repair technique.

Patient population
According to the existing literature, surgery of glenoid fractures was indicated if fragment dislocation of at least 4 mm or a decentered humeral head on anteroposterior x-rays was present. Patients were eligible for the novel transosseous technique if a solitary fracture was present or one large main fragment (Type Scheibel 1b or 1c; [21]).
From March 2017 to May 2021, 23 patients received the novel arthroscopic procedure in the two participating centers: Three patients had surgery at the "Klinikam-Ring" Clinic and 20 patients at the Cologne-Merheim Medical Center (CMMC). There were initial plans for two other patients at CMMC to undergo the procedure, but in both cases intraoperative assessment had shown that the anterior fragment was not large enough for the endobutton to engage upon its anterior aspect. Thus, the implant was removed and a conventional arthroscopic suture anchor technique according to Sugaya [24] was performed.
Informed consent was given by all 23 patients. For the results of the clinical outcome, a minimum follow-up of 6 months was required. The study was approved by the local ethics committee of the University Witten/Herdecke (185/2019) and was conducted according to the Declaration of Helsinki.

Clinical outcome
Following surgery, patients were screened for complications related to the procedure (neurovascular injury, infection, impaired wound healing, re-operation) or events of instability or re-dislocation. At the final follow-up, all patients were assessed for clinical stability and rotator cuff strength. The range of motion of both shoulders was measured by applying a goniometer. The level of sports activities and return to work were recorded. If patients were already retired, they were asked to estimate the potential to return to their former occupation. Outcome scores were measured including the Constant Score (CS; [2,6]), Rowe Score (RS; [19]), Melbourne Instability Shoulder Score (MISS; [28]), the Western Ontario Shoulder Instability Index (WOSI; [12]), and the Subjective Shoulder Value (SSV; [7]).

Radiological assessment
The size of the glenoid lesion was calculated according to Itoi et al. [11]. The calculation was performed by en-face threedimensional (3D) computed tomography (CT). The fractures were classified according to the Scheibel classification, where acute lesions of the glenoid are categorized as "Type 1" (1a: Osteochondral avulsion lesion, 1b: Solitary glenoid rim fracture, 1c: Multifragmented glenoid rim fracture; [21]). Postoperatively, the patients underwent 3D CT of the scapula to assess fracture reduction and button placement (. Fig. 5). These CT scans were examined for fracture reduction and the remained fracture step (in millimeters) by two radiologists. For radiological follow-up, x-rays were obtained in three views (anteroposterior, y view, axial view) to assess fracture healing (. Fig. 6) and onset or progression of glenohumeral osteoarthritis according to the Samilson-Prieto classification [20].

Statistical analysis
Statistical analysis with calculation of mean values and standard deviations was performed using Microsoft Excel 2019 (Microsoft, Redmond, WA, USA). Further statistical testing was performed applying SPSS (Version 21, IBM Statistics, IBM, Armonk, NY, USA): For clinical follow-up active range of motion of the affected shoulder was compared with the contralateral shoulder using the Wilcoxon test. For comparison of patients with versus without rotator cuff injuries, the Mann-Whitney U test was applied. A value of p < 0.05 was considered significant.

Results
The study include 23 patients were included in the study. There were three women and 20 men with a mean age of 51.1 ± 16.1 years at the time of surgery. An indirect trauma mechanism with a fall on the extended arm or an abduction/ external rotation trauma was present in eight patients. In 19 patients (82.6%), the initial trauma was accompanied by a shoulder dislocation. The dominant shoulder was affected in 12 patients. None of the patients reported any history of previous shoulder dislocation.
Calculation of the size of the glenoid lesion according to Itoi showed a mean fragment size of 30.5% ± 5.4 with a minimum 18.7% and a maximum of 40.5%. In 21 patients there was a Scheibel type 1b fracture (solitary glenoid rim). Two patients had a Scheibel type 1c fracture (multifragmentary glenoid rim); however, both contained one larger main fragment.
The average time from injury to surgical treatment was 12.4 ± 11.0 days. In two cases, a second pair of endobut-tons was applied for glenoid fixation, all other 21 cases required one pair, as described above. Mean stay in hospital was 4.3 ± 1.9 days.

Concomitant injuries
Concomitant injuries were found in 21 cases, mainly Hill-Sachs lesions (16 of 23). Furthermore, concomitant injuries requiring surgical treatment were found in 13 cases (. Table 1): Four patients had injuries of the rotator cuff; two of these with a full-thickness tear of the supraspinatus tendon, one with fullthickness tears of the supraspinatus tendon plus partial tear of the infraspinatus tendon, and one patient with traumatic partial tears of both the infraspinatus and the subscapularis tendon plus a chronic retracted tear of the supraspinatus tendon. The supraspinatus tendon tears were all treated arthroscopically in a doublerow technique, except for the chronic tear, which received debridement. One patient had a dislocated fracture of the greater tuberosity that was treated with a screw osteosynthesis via a mini-open delta approach. Undislocated greater tuberosity fractures in two patients were treated Hill-Sachs lesion 2 Subscapularis tendon rupture, infraspinatus tendon rupture, chronic retracted supraspinatus tendon tear 3 Hill-Sachs lesion 4 Hill-Sachs lesion; SLAP lesion type 2 5 -6 Hill-Sachs lesion 7 Hill-Sachs lesion; SLAP lesion type 4, posterior labral lesion; acromioclavicular joint disruption Rockwood type 5; nondisplaced acromion fracture 8 Hill-Sachs lesion 9 Hill-Sachs lesion 10 Hill-Sachs lesion; SLAP lesion type 2, Pulley lesion 11 -12 Hill-Sachs lesion 13 Hill-Sachs lesion 14 Hill At the time of follow-up, no patient had suffered recurrent shoulder dislocation or a feeling of instability. We could not detect the presence of the apprehension sign in any of these patients. The evaluation of the subscapularis function revealed a negative internal rotation lag sign and belly-off sign in all patients. No patient showed clinically detectable differences in the lift-off test compared with the contralateral side. Of these patients, 21 reported return to work, and one patient had not returned to work 7 months after surgery. Furthermore, 16 patients reported that they had returned to sport at the same level, while six patients were at a slightly reduced level.
Four patients with concomitant rotator cuff tears or displaced greater tuberosity fracture were on average 7 years older than patients without these injuries to the rotator cuff mechanism (57.

Radiological results
In total, 19 patients were available for radiological follow-up. In all cases, radiological evaluation by two radiologists showed fracture consolidation without secondary dislocation of the fracture and without signs of heterotopic ossification. There were also no signs of hardware impingement or dislocation. The radiological evaluation revealed new onset of osteoarthritis in three cases (15.8%). Of these three patients with posttraumatic osteoarthritis, all showed an inferior humeral osteophyte of 1-3 mm corresponding to a grade I according to the Samilson-Prieto classification. Three other patients had a mild (grade I) preexisting osteoarthritis already upon injury, which showed no progression at the time of follow-up. Three patients with new osteoarthritis were not older at the time of surgery compared to patients without progressive osteoarthritis at follow-up (51.0 ± 19.5 years vs. 51.2 ± 16.2 years; p = 1.00). The postoperative step-off of the glenoid measured by CT averaged 1.55 ± 1.05 mm (0-4 mm). The three patients with signs of osteoarthritis had shown a step-off of 1, 1, and 4 mm, respectively. We found no correlation between the step-off and the presence of radiological signs of osteoarthritis.

Discussion
Surgical treatment of glenoid fractures remains challenging. Recent evidence has shown that open surgery is associated with higher complication rates and worse clinical outcomes than arthroscopic procedures, probably due to the soft tissue trauma requiring detachment of the subscapularis tendon [4,14].
Thus, multiple arthroscopic methods have been published, which also involve several potential problems and pitfalls: Anterior screw placement perpendicular to the fracture line necessitates an arthroscopic trajectory that endangers the brachial plexus and vessels [23]. Also, hardware problems regularly require revision surgery, especially impingement of screw heads [25]. Thus, a myriad of refixation procedures have been described using suture anchors at the fracture site, for example, by Porcellini [18], Sugaya [24], or Millett [15]. However, these techniques are usually less applicable for large fragments. Also, Nakawaga et al. found that placing multiple soft suture anchors in a linear arrangement for Bankart repairs might be associated with postoperative recurrence of instability due to new glenoid fractures along the suture anchor insertion sites [16]. In addition, Greenstein et al. demonstrated in a cadaveric model that placement of intraarticular sutures during arthroscopic bony Bankart repair techniques may harm the humeral head cartilage and suggested further investigation of alternative, cartilage-sparing arthroscopic techniques for anterior glenoid fractures [9]. All these arthroscopic methods have in common that the implants are drilled and placed from anteriorly. Thus, we have described an all-arthroscopic transosseous technique that (a) uses standard portals and a glenoid drill guide placed over the posterior portal thereby sparing the subscapularis tendon and the anterior neurovascular structures, and (b) applies a double-button-suture construct placed extra-articularly for stable refixation that is cartilage-sparing and avoids glenohumeral hardware or su-ture impingement [27]. In the present study, 23 anterior glenoid fractures were treated safely and reproducibly with this novel method with excellent clinical and radiological short-term results.
Few retrospective studies have previously examined both the clinical and radiological outcomes of glenoid fractures following arthroscopic surgery: Scheibel et al. published the results of a large cohort applying suture anchors and chondral darts [21]. With a minimum follow-up of 24 months, 21 patients showed good to excellent clinical results (CS 84.5 points, RS 90.8 points, MISS 96.2 points, WOSI 89.2%, SSV 92.1%), but there was progression or new-onset osteoarthritis in 28.6%. While the clinical scores are very similar to the results of our present study, we found osteoarthritis in 15.8% of cases. However, we evaluated the patients with a minimum of only 6 months and mean followup was just after 15 months, which represents the major limitation of our study. Further follow-up will have to delineate the long-term development of posttraumatic osteoarthritis in these patients. Interestingly, Scheibel et al. also found a high rate of relevant intra-articular concomitant lesions in about 78% of cases. Lin et al. found better pain outcomes of arthroscopic treatment compared to open surgery as it enabled accurate management of associated intra-articular lesions that were found in 50% of cases of the arthroscopic group [14]. In the current study, in 13 of 23 patients (57%) relevant concomitant lesions were found intra-articularly requiring arthroscopic treatment. Especially injury of the rotator cuff was associated with inferior outcome scores, but this might also be due to the short followup [17]. However, considering these high rates of concomitant injuries in our and other studies, magnetic resonance imaging should be recommended for patients with glenoid fractures who receive conservative therapy.
In this context, Wieser et al. recently reported that conservative treatment of displaced glenoid fractures with a mean follow-up of 9 years showed good clinical scores and fracture healing in 30 patients [29]. However, 23% had post-fracture onset of osteoarthritis and one patient had to be treated with arthroplasty. Despite conservative therapy, magnetic resonance imaging results were not reported, which could have helped to assess the role of concomitant lesions. Also, six patients had been excluded from follow-up as they had undergone surgery elsewhere. Thus, due to the absence of any prospective evidence, the optimal treatment algorithm for glenoid fractures remains a matter of debate.

Limitations
Several limitations of the present study have to be mentioned. We conducted a retrospective analysis, and there was no control group. We only presented a shortterm follow-up. Only x-rays with three views were obtained for the follow-up, as we believed that these were sufficiently valid for assessment and that CT scans would expose the patients to too much radiation. Finally, a main limitation of the surgical method presented here is that it is not applicable for smaller fragments or comminuted fractures: As described earlier, if the anterior fragment is too small (from medial to lateral) then the anterior button cannot engage upon the fragment, but will cut out medially. As for the two cases excluded from this study, the implant was just removed through the anterior portal and a standard arthroscopic method (e.g., the Sugaya technique) was applied.