Single-Row Rotator Cuff Repair

Rotator cuff tears are a common cause of pain and disability among adults. Partial tears are usually treated conservatively. Complete tears might be treated conservatively in some cases; however, surgical repair is often performed in selected cases and situations where conservative treatment fails to restore function and pain relief. In addition, some patients with acute tears might be good candidates for acute surgical repair, as will be studied in this chapter. A plethora of techniques is available to repair rotator cuff tears. Among these, the surgeon faces the dilemma to choose the best treatment for the patient. Open techniques were the gold standard in the 1990s. However, the advent of arthroscopy has led the shoulder and sports surgeon community towards these. Arthroscopic rotator cuff repair has become the gold standard nowadays despite the lack of proper evidence to support this change. Furthermore, simple single-row repairs had been discarded favouring double-row techniques, yet new evidence supports the use of the former due to similar results, simplicity and cost-effectiveness. This chapter examines current evidence to help the surgeon decide between open and minimally invasive techniques and select suitable repair configurations.


Introduction
Rotator cuff tears are commonly seen in the orthopedic surgeon clinic, even more in the shoulder and elbow subspecialized professional practice. Different muscles form the rotator cuff: subscapularis, supraspinatus, infraspinatus, teres minor, and some authors also include the teres major due to its role as an internal rotator. The primary role of the rotator cuff is to stabilize the humeral head regarding the glenoid to allow the deltoid to perform the elevation of the arm. In addition, the rotator cuff externally rotates the glenohumeral joint (infraspinatus and teres minor) and contributes to internal rotation (subscapularis, assisted by the pectoralis major, teres major and latissimus dorsi) [1].
Patients with rotator cuff tears mainly complain of pain during daily living activities but also at night, when the pain can likewise interfere with proper resting. Moreover, a significant tear may impair function, limiting the active range of motion and can be the culprit of premature glenohumeral arthritis. Loss of external rotation, sometimes isolated, may appear in the onset of a posterior rotator cuff tear [1,2].
Rotator cuff tears are expected after 60 years old. They correspond with the Neer type 3 stage and can be identified in about 20-30% of the patients in this age group. Beyond 80 years old, the ratio of patients suffering from cuff tears rises to more than 60%. However, the symptoms do not correlate with the presence of tears or even the size or retraction. Most patients do not seek advice from an orthopedic surgeon and do not demand a surgical intervention. More than half of the patients where a tear is identified will also suffer from a tear in their contralateral shoulder, especially in those older than 60 years [2][3][4][5][6][7].

Classification
A plethora of classifications for rotator cuff tears has been described since the pathology became more interesting for the orthopedic community.
Neer described the evolution of rotator cuff disease in three stages. First, in individuals younger than 40 years, one can observe oedema and hemorrhage in the rotator cuff. In a second stage, the disease evolves in individuals between 40 and 60 years old, and fibrotic and tendinosis phenomena might be observed. Finally, in a third stage, usually, in patients older than 60 years, a tendon rupture is observed. Probably a fourth stage would involve rotator cuff arthropathy, with cephalad migration of the humeral head and degenerative osteoarthritis at the level of the glenoid as well as in the humeral head [15,16].
Harryman described a classification based on the number of injured tendons. It is commonly accepted in Europe that a complete tear of two or more tendons should be considered massive, and concerns about reparability should arise [19].
Ellman and Gartsman introduced in 1993 a classification differentiating partialthickness and full-thickness tears. Partial tears were classified in grade 1 (<3 mm deep, <25% thickness), grade 2 (3-6 mm, <50%) and grade 3 (>6 mm, >50%). The partial tear classification system is accepted worldwide as it helps in treatment selection, as discussed in the next section. These authors also proposed a full-thickness classification based on tear-shaped, which has been judged useful and is currently used worldwide. Five groups were described: crescent shape, L shape, Reverse L, trapezoidal shape and massive tears [20,21].
Concerning partial tears, Snyder clarified that a distinction between articular and bursal tears is mandatory as the criteria for surgery are different.
Fox and Romeo described a specific classification for subscapularis tears in 2003. Four types were proposed: Type 1, partial thickness; Type 2, complete tear of the

Treatment
The orthopedic surgeon's community has failed, to the date, to clearly identify which patients would benefit from surgical repair as the primary treatment. Most patients accept an initial attempt of conservative treatment, which is successful in most cases. They undergo a surgical rotator cuff repair if the former fails to provide pain relief and function improvement. Although this strategy is accepted worldwide, it does not provide a definitive solution for the tear, which seldom heals on its own (about 10% of small tears heal, and 10% become smaller). Tear progression is always worrisome as it may lead to non-repairability, arthritis and chronic pain. As a matter of fact, more than 50% of patients with partial tears experience a progression, which is closely correlated with the size of the index tear, and more than half of those with a full-thickness tear will suffer from an increase in the size of the tear, which may be the culprit for an increase in pain and disability. Acute traumatic tears, either in a previously asymptomatic patient or in patients with a previous history of rotator cuff disease yet compensated, with a significant loss of function, are good candidates for surgical repair without unnecessary delays [25][26][27].
The objective of the orthopedic surgeon, once the surgery is indicated and agreed upon by the patient, is to achieve sound fixation of the cuff to humeral tuberosities. Thorough attention to avoid gap formation is also a must. If the tendon is well fixed close to the bone, healing tissue will develop [28].
Despite some studies that show few differences in pain relief concerning tendon healing or retear, many others have identified a well-healed cuff as the main factor for improved strength and range of motion [28].

Open vs. arthroscopic
Open rotator cuff repair has been the gold standard when treating cuff tears. However, some concerns about infection and faster recovery have led shoulder surgeons to investigate the use of minimally invasive and arthroscopic technique.

Shoulder Surgery for RC Pathology, Arthropathy and Tumors
Neviaser et al. retrospectively reviewed a cohort of patients who underwent anterosuperior rotator cuff repair with subscapularis involvement and found no differences in the outcomes between both modalities [29].
Hasler et al. in a prospective, randomized and long-term outcome study comparing open and arthroscopic rotator cuff repair did not document any difference either clinical or radiological. In addition, they did not find any harmful consequence due to transdeltoid mini-open approach [30].
Nazari et al. studied the effects of arthroscopic and mini-open rotator cuff repairs concerning pain and range of motion and did not find significant differences at 3, 6 and 12 months between both techniques [31].
Bayle et al. studied not only clinical outcomes but rotator cuff integrity at 1-year follow-up and did not find differences in a prospective study [32].
Fink Barnes et al. studied patient satisfaction and rotator cuff integrity in a cohort and found better results concerning integrity in the open surgery group. However, no statistical differences were found between both at the end of the study [33].
To sum up, if cost or time is an issue, open rotator cuff surgery is preferred. However, if short-term results are crucial and the patient seeks a faster return to work or sport, the arthroscopic repair is the technique of choice. The patient needs to be advised that both techniques may lead to excellent results and that the community of orthopedic surgeons cannot recommend one over the other if the factors mentioned above are not taken into account.

Repair techniques
With the advent of open and mini-open techniques, some classic repair techniques were developed. Transosseous sutures were mainly implemented, where bone tunnels are created, and sutures are placed directly through them, allowing for cuff reinsertion, as depicted in Figure 1.
A single-row repair is performed by means of anchors, usually one or two, with sutures integrated into them that permit cuff repair, as depicted in Figure 2. Singlerow techniques are easier to perform arthroscopically, as well as in an open fashion.
Double-row repairs use one or two anchors in a medial row, suturing far from the tendon stump border area and a lateral row, again with one or two anchors, closer to  the end of the ruptured tendon and the lateral border of the cuff footprint along the tuberosity, as it can be seen in Figure 3.
More recent are transosseous equivalent techniques, similar to double-row techniques yet requiring only a medial row and knotless implants laterally (without sutures passing through the tendon laterally but applying those from the medial row against the tendon)(see Figures 4 and 5) [28].     who should analyze factors such as simplicity, skill, cost and time consumption when choosing the right technique for the patient [28,[34][35][36].

Single vs. double row
Deveci et al. and Maasse et al. reported that most studies comparing single-and double-row techniques were comparing different constructs and suture configurations, and thus the results obtained are not valid. Most studies used lateral single-row configurations either in vitro or in vivo, and very few a more medial single row avoiding unnecessary tension at the level of the repair (which is a must, especially in large and retracted tears) When a proper, more medial, single-row configuration was used, the results become similar. It is not fair to compare single-row configurations performed poorly and too lateral to modern double-row techniques, and despite that, clinically relevant results have failed to be obtained [37,38].

Transsosseous vs. single row
Transosseous repairs are of everyday use during open rotator cuff repair. The use of bony tunnels avoids anchors, which is a significant advantage concerning cost and ease of revision surgery. The former is performed either by employing guides and Kirschner wires or bone needles in the osteoporotic bone. Ahmad et al. and Park et al.compared micromotion in vitro at the footprint interface and concluded that transosseous repair minimizes strain and, therefore, would be advantageous concerning tendon to bone healing. Apreleva et al., in another experimental study, demonstrated that footprint anatomy restoration was superior when using transosseous techniques [39][40][41][42].
On the contrary, other authors such as Randelly et al. in a clinical study concluded that single-row and transosseous hardware-free repairs led to the same results concerning pain, function and retear rate at 15 months. However, transosseous repairs might be more cost-effective because they avoid the use of anchors [43].
Same principles apply to partial repairs when comparing transtendon single-row techniques versus double-row suture bridges. Zafra et al. demonstrated that partial tears might be treated with similar results using both techniques [44].

Transosseous vs. double row
Traditional transosseous repair focuses on restoring cuff footprint and applying pressure on the enthesis (against tuberosity bone). On the contrary, the traditional double row focuses on suturing the tendon medial and lateral in the footprint. Waltrip et al. compared both and demonstrated that a higher stress concentration was found in the latter at the medial anchors and suturing areas, while the former had more significant stress at the tendon to bone interface level. Forces through the tendon to bone enthesis can be beneficial, and on the contrary, forces around the anchors may explain the high recurrence rate and pull-out observed in double-row repairs [28,45].

Transosseous equivalent vs. double row
Transosseous equivalent techniques mimic the effect created by traditional transosseous techniques utilizing lateral knotless anchors, which insert the sutures used in the medial row into the lateral cortex of the tuberosity. Hence, this technique mimics the effect of the classic techniques as it adds pressure forces that apply the tendon stump against the bone.
Siskoksy et al., in a cadaveric study, compared load to failure and gap formation using transosseous equivalent and double-row techniques. They concluded that load to failure was higher when using a transosseous equivalent construct. However, gap formation was similar between both [46]. The same conclusion was obtained by Costic et al. in a similar study in cadavers where cyclic loading was applied on the footprint [47]. Park et al. demonstrated in vitro that the pressure exerted by a transosseous equivalent is significantly higher than that observed in double rows. Nevertheless, it remains difficult to know the right amount of pressure or the ischemic effect of an excessive force on the tendon stump [48].

The art of the single-row technique
Not all single-row techniques are created equal. Arthroscopic rotator cuff repair emerged in the 1990s, and logically single-row constructs were the first used by shoulder and sports medicine surgeons. Initially, a unique row formed by one or two anchors (placed in the centre of the footprint or lateral to it) was used.
Not all single-row techniques are created equal. Arthroscopic rotator cuff repair emerged in the 1990s, and logically single-row constructs were the first used by shoulder and sports medicine surgeons. Initially, a unique row formed by one or two anchors (placed in the centre of the footprint or lateral to it) was used. Despite initial promising outcomes, the retear rate was undoubtedly worrisome, which explains the subsequent interest in developing double rows or transosseous equivalent techniques.
Complex and more robust suture configurations (such as the Mason-Allen technique) are complicated to replicate arthroscopically.
Simple or mattress sutures, often used arthroscopically, may not be sufficient to hold a rotator cuff with poor-quality tissue to the bone long enough to allow for proper healing. These statements led to a quest to find a better technique by adding anchors and complexity to the repairs. However, it was not until later that some surgeons started to question if a well-performed single row would be sufficient. To do so, a more medial single row started to be used with the rationale behind it that less tension on the rotator cuff would result. This is very useful in the onset of chronic and massive tears where even after proper slide liberation, tendon retraction impedes proper footprint anatomical restoration, as depicted in Figures 6-9 [49].
Several factors may contribute to the final healing of the rotator cuff tendons to the bone. Among them, mechanical factors such as gap formation, stiffness and strength of the repair, load to failure, repair tension have already been discussed in previous sections of this chapter. However, other factors such as tendon vascularity, footprint coverage and respecting the proper biology of tendon healing are sometimes forgotten [49].
Suture bridge techniques have demonstrated in vitro superior strength, stiffness, less gap formation and more load to failure. However, this comes at the cost of vascularity disruption, high tension at the muscle to tendon junction (which may lead to a tear at this level). Transosseous equivalent techniques enhance the resistance and stability of the repair at the tendon to bone interface; nevertheless, they neglect biology as they create an ischemic environment. As a matter of fact, in vivo studies have failed to demonstrate the superiority of transosseous rotator cuff repair over single-row repair [49,50].   In the context of a single-row repair, a more medial row may enhance biology as it adds less loading forces and respects vascularity. However, footprint non-anatomic restoration may arise as a concern. By medializing the anchors in the footprint (not medial to it), a part of the surface may stay uncovered by the tendon stump. Although the real significance of this has not been established, surgeons commonly think anatomic restoration would be superior to a 'leave it alone' strategy. To cope with this problem, creating bone marrow vents through microfracture instruments would promote the formation of a neotendon and fibrocartilage. The benefits of adding mesenchymal cells to the healing area would also increase the chances of the tendon to bone healing. Yamakado et al. concluded in a prospective randomized trial comparing suture bridge configurations and single-row (medially based) repairs that both techniques lead to the same clinical results. They found that incomplete healing was more common in single-row repairs, and on the other hand, medial cuff failure was more common in patients with bridge constructs. However, the differences were not significant from a statistical point of view [49].
Another argument favoring single-row techniques is that excessive medial sutures in the cuff may lead to a myotendinous junction tear. Despite some authors that studied the use of more medial sutures in vitro, advocating for more stability of the construct, it is accepted globally that this can be dangerous as it might come with a rupture at the level of the muscle, ending up with a tendon stump anchored to the tuberosity but without a healthy muscle able to apply traction on it. Therefore, leaving a security distance from the musculotendinous junction of 10 mm is the wiser choice [51,52].  It has also been suggested that a single-row technique mimicking the Masson-Allen suture technique might increase the strength of the repair. Despite some studies confirming that these modifications of the original technique ('modified Mason Allen' or 'massive cuff suture configuration') might increase in vitro the stability of the repair (similar to the original Mason-Allen technique), they have failed to demonstrate a statistical difference or a real relevance clinically. In fact, rotator cuff repairs usually fail at the suture-tissue interface due to poor quality of the latter; therefore, the culprit might not be suture configuration. This the interest in keeping it as simple as possible [53][54][55][56][57][58].

Conclusions
Rotator cuff tear is a common etiology for pain, disability and loss of function that might be considered a burden for some health systems.
Conservative treatment may be adequate for a large number of patients; however, it is utterly crucial to identify patients who would benefit from an acute repair and not to neglect patients who still suffer and do not achieve a satisfactory result employing conservative methods.
The selection of the surgical technique for those patients who require a rotator cuff repair should be guided by the current evidence. It should favor methods that provide the best results for the patient while maintaining simplicity and cost-effectiveness at the proper levels. Therefore, a modern single-row technique with a more medial Figure 9. Final modern single-row construct. Sutures are passed through the tendon far from the musculotendinous junction and far from the border. Less footprint is covered by the cuff when using this technique; however, bone marrow vents, lateral to the footprint, may provide stem cells which will develop a neotendon.

Author details
Amhaz Escanlar S. 1 *, Jorge Mora A. 2 and Pino Miguez J. 3 1 University Hospital Complex, Santiago de Compostela, Spain 2 Reconstructive Surgery, University Hospital Complex, Santiago de Compostela, Spain 3 Pediatric Orthopedics and Spine Surgery, University Hospital Complex, Santiago de Compostela, Spain *Address all correspondence to: sameramhaz@gmail.com anchor placement and bone marrow vents in the rotator footprint is probably the technique that balances all the factors mentioned before.