Reverse Total Shoulder Arthroplasty: How to Avoid and Manage

Fig. 7.1

Constituting the soft tissue tension and balancing the global decoaptation by using a larger-sized insert

Preoperatively, in patients with external rotation deficiency or weakness, latissimus dorsi tendon transfer can be added to the RTSA to reconstitute the force couple of the shoulder. Gerber et al. reported significant improvement in the active external rotation and functional outcomes with RTSA when combined with latissimus dorsi tendon transfer [31].

7.1.3 Subscapularis Insufficiency

The basic subscapularis muscle contribution to the stability is by balancing the posterior force vectors and enhancing the compressive forces. Additionally, it prevents anterior subluxation of the humeral head by constituting an anterior barrier. This effect becomes more significant in lower abduction angles of the shoulder [32]. The etiology of the subscapularis deficiency are as follows: (1) inadequate repair during the surgery, (2) history of more than one surgery, (3) joint contracture or excessively tense subscapularis tendon owing to the component size, (4) subscapularis atrophy and weakness (Goutallier grade 3 or 4), and (5) early aggressive physical therapy. The instability rate following the RTSA is reported to be 1% after subscapularis repair and 9.5% with no repair [33]. The paramount reasons for early-onset instability in consequence of subscapularis insufficiency after RTSA with subscapularis repair are too much lateral offset and overstuffing on the ground of large-sized components. The most significant indicator of the subscapularis over-tensioning is the restriction in external rotation of the shoulder. In these patients, medialized tenodesis of the subscapularis can prevent over-tensioning and external rotation restriction, and by this means instability risk caused by subscapularis insufficiency.

Edwards et al. reported higher rates of dislocation risk in patients with no subscapularis repair in a study including prospective follow-up of RTSA procedures with and without subscapularis repair. However, they also pronounced that this group also had more complicated pathologies regarding the bone tissue besides the soft tissue deficiency [21]. Clark et al. in their retrospective study with similar patient characteristics reported no significant difference between the groups [7].

The repair of the subscapularis may not be feasible in patients with massive rotator cuff rupture including the subscapularis tendon and those with tuberculum minus pathology based on a previous fracture sequela (Fig. 7.2). The humeral component can be replaced in minimally retroverted position to decrease anterior dislocation risk when the subscapularis repair is not feasible.

../images/429740_1_En_7_Chapter/429740_1_En_7_Fig2_HTML.jpg — Fig. 7.2

Deterioration in the anatomy of the proximal humerus in a patient who developed implant insufficiency following the osteosynthesis for right proximal humerus fracture

7.1.4 Prior Surgery

The main causes of increased instability in revision cases are as follows: poor bone stock, insufficient soft tissue coverage, and destroyed anatomic landmarks. Trappey et al. reported the instability risk as 5.2% for primary RTSA and 8.3% for revision RTSA [34]. Wall et al. reported those risks as 13 and 37%, respectively [35]. Walch et al., in a multicenter study, reported the instability after RTSA performed in patients with failed anatomical arthroplasty as 11%, in post-trauma cases as 9%, and in primary rotator cuff arthropathy cases as 4% [10]. Padegimas et al. reported the prior surgery history as 66.7% in patients with instability following RTSA and 21.6% in those without instability [36]. Glenoid bone defects may develop after revision cases. These defects should be restored by glenoid component augmentation or bone grafts. As for humeral bone defects, preference of longer humeral stems will decrease the instability risk.

7.1.5 Deltopectoral Approach

This approach is a frequently preferred technique in shoulder arthroplasty because of providing a wider view and movement area. However, the subscapularis muscle is under risk with this approach which gives birth to instability related to the soft tissue damage. Although the superolateral approach offers a minimal soft tissue dissection without any subscapularis damage, the risks for axillary nerve injury and component notching because of the difficulty in reaching to the inferior aspect of the glenoid made the surgeons keep away from this approach [37–39]. Simovitch et al. reported that the notching can be prevented by optimal positioning of the glenoid component [38]. However, the notching risk increases because of the difficulty in inferiorly replacing the glenoid component. Furthermore, the deltoid muscle detachment may also lead to a functional deficit. The deltopectoral approach is especially advantageous in revision cases. Walch et al. reported the instability risk as 5.8% in 363 patients performed RTSA with a deltopectoral approach and as 1% in 94 patients with a superolateral approach [10]. Werner et al. reported the instability risk with deltopectoral approach as 6.3% after primary shoulder arthroplasty and as 9.8% after revision arthroplasty [40].

7.1.6 Body Mass Index

Chalmers et al. reported the mean BMI of the patients with early instability (first 3 months) following the RTSA as 32.2 kg/m² and added that the 82% of the patients had BMI over 30 kg/m² [5]. Padegimas et al. reported the mean BMI of the patients with instability following the RTSA as 33.2 kg/m² and that of those with no instability as 29.5 kg/m² [36]. The increase in the instability risk based on the obesity may be due to inappropriately adjusted soft tissue tension during the surgery, inappropriately positioned components, and adduction of the shoulder by the lever arm effect of the excessive soft tissue around the arm. Furthermore, excessive soft tissue may predispose to decoaptation during the movement.

7.1.7 Sex

Chalmers et al. reported that the 82% of the patients who developed early (first 3 months) instability following RTSA were male [5]. Padegimas et al. reported that the 60% of the patients with instability after RTSA were male [36]. Teusink et al. gave the ratio of previous surgery history in females who developed instability following RTSA as 75% and in males as 22% [11]. The increased risk for instability in male patients may be related to higher level of activity.

With the increase in experience of the surgeons and new prosthesis designs in time, the complication rates decreased. Ekelung reported the instability rate in 236 RTSA procedure between 1995 and 2002 as 6.7% and in 457 procedures after 2006 as 0.7% [27]. The key points to avoid instability following the RTSA are appropriate deltoid tension adjustment and replacing the humeral component in neutral or minimally anteverted position [27]. Adjusting the humeral height and offset by taking the contralateral upper extremity as a reference will decrease the instability risk, especially in patients with aforementioned risk factors (Fig. 7.3). Pastor et al., in their biomechanical study, reported that the integrity of the subscapularis muscle, larger-sized glenosphere replacement, and deep humeral cup replacement are essential factors for intact anterior stability in RTSA procedures [41].

../images/429740_1_En_7_Chapter/429740_1_En_7_Fig3_HTML.jpg — Fig. 7.3

Constituting the appropriate humeral height during the RTSA procedure in a patient with right proximal humerus fracture sequela

It is recommended that an abduction orthosis of 3–6 weeks postoperatively should be prescribed to patients with aforementioned risk factors. The immobilization of the shoulder joint in abduction leads to deltoid muscle shortening and in this way increases the coaptation between the components.

7.2 Management of the Instability

In the general medical notion, the best treatment option is said to be the protection from the diseases. The surgical approach and postoperative follow-up should be planned carefully considering the potential causes of instability. A widely accepted treatment protocol has not been developed yet because of the inexactly known risk factors and etiology of the instability following the RTSA [42]. The first step of the management is to find an underlying reason for instability. The mechanism of the instability is evaluated by patient history and radiographic examination. The shoulder joint infection is sought, and if doubted, then a synovial fluid aspiration is performed for microbiological culture. The soft tissue condition, positioning of the components, and neurological condition are evaluated when the instability develops.

The time for instability following the surgery is important. Walch et al. reported that the instability following the RTSA developed in the first 3 months after the surgery in 16 of 22 (72.7%) patients [10]. Teusink et al. reported that the 62% of the instability following the surgery developed in the first 3 months [11]. The dislocation following the RTSA usually does not generate significant pain; therefore, any restriction in the range of motion must alert the surgeon and make him/her doubt of joint dislocation which should be evaluated immediately with the radiographs. The diagnosis of the subluxation is easier than the dislocation because patients can usually describe this pathology in their own words. There is no described optimal management for this pathology yet.

The deltoid muscle and axillary nerve function, glenoid and humeral component position, and bone defects are evaluated when the instability develops. If they are all normal, the closed reduction under general anesthesia or sedation is tried first (Fig. 7.4). If the joint reduces, the stability is evaluated by moving the arm through full range of motion. The deltoid muscle and axillary nerve function, glenoid and humeral component position, and bone defects are reevaluated following the reduction. The instability usually occurs in adduction, internal rotation, and extension of the shoulder; therefore, an abduction-external rotation orthosis is prescribed which prevents those unintended movements of the shoulder. Functional rehabilitation is initiated following the 6-week immobilization. Teusink et al. reported the success rate of the closed reduction with 28-month follow-up as 62% in 21 patients with instability following the RTSA and also stated that 9% of those were suffering from persistent instability symptoms. There was no significant difference in outcomes after closed reduction between the early- and late-onset instability [11]. Gerber et al. stated that the early-onset dislocations were mostly secondary to poor surgical technique and had worse outcomes following closed reduction when compared to late-onset dislocations [22].

../images/429740_1_En_7_Chapter/429740_1_En_7_Fig4_HTML.jpg — Fig. 7.4

Radiographs of a patient with a history of repeated right shoulder surgery; (a) anterior-posterior radiograph before RTSA, (b) postoperative anterior-posterior radiograph, (c) postoperative first-month anterior-posterior radiograph manifesting anterior dislocation, (d) and anterior-posterior radiograph following the closed reduction

In our practice, all of the patients with dislocation following the RTSA undergo closed reduction, immobilization, and rehabilitation as the initial steps of management. Surgeons should keep in their mind that the conservative management of the instability following the RTSA is satisfactory in more than a half of the patients [43]. If the closed reduction fails, the open reduction should be performed, and the implants for any potential necessity of revision arthroplasty should be ready for this procedure. The glenoid and humeral components, polyethylene insert wear, bone defects, and soft tissue tension should be evaluated repeatedly during the surgery if the open reduction is initiated. Following the reduction, the full range of motion of the shoulder should be forced to exclude any potential mechanical impingement of residual bone or soft tissue. The residual bone and soft tissue are removed thoroughly taking care not to injure axillary nerve at the inferior aspect of the shoulder. If the stability cannot be provided, the scar tissue at the inferior aspect of the glenoid is debrided again, and then the stability is reevaluated following the soft tissue tension is enhanced (by increasing the polyethylene or humeral spacer thickness). If the stability still not provided, the components are revised. We must never forget that the outcomes of the revision cases for instability are directly related to the causes of the instability.

According to the instability direction, humeral osteotomy level is changed, and the anatomical offset is strived to regain. The version of the humeral component is adjusted [22, 23]. The glenoid bone graft can be used to enhance the lateral offset [19]. Humeral height can be increased with allografts [44]. Surely, the soft tissue tension should not be ignored to prevent any potential recurrence while making the aforementioned interventions. The humeral component aligns more medially and inferiorly with a higher neck-shaft angle (valgus) and more laterally and superiorly with a lower neck-shaft angle (varus). The anatomical neck-shaft angle is of importance to prevent the range of motion restriction on the ground of inferior impingement.

7.2.1 Restoration of the Soft Tissue Tension

The instability as a result of soft tissue looseness is managed by regaining the appropriate soft tissue tension, lengthening of the humerus, or lateralization of the joint center of rotation offset. To lengthen the humerus, (1) the neck-shaft angle can be increased (replacing the humeral component in valgus), (2) a larger humeral component size can be chosen, (3) a larger or eccentric glenosphere can be chosen, (4) the glenosphere can be replaced more inferiorly or tilted inferiorly, and (5) a thicker polyethylene insert can be chosen. To lateralize the joint center of rotation offset, the humeral component can be positioned in varus (lower neck-shaft angle), or a glenosphere with lateral offset can be chosen. To increase the offset, before a complicated intervention, like the revision of the components, simpler interventions should be made first, such as replacing with a larger-sized polyethylene insert and glenosphere.

The damaged soft tissue at the anterior aspect of the shoulder should be repaired in the case of anterior instability. If the soft tissue support is still insufficient, reinforcement with the pectoralis major tendon can be added. The force vector of the pectoralis major muscle, which is very powerful, is similar with that of the subscapularis muscle. The transfer of the pectoralis major tendon can be also considered in subscapularis insufficiency; however, its efficiency is under debate. Elhassan et al. reported the rate of the failure of pectoralis major transfer as seven in eight patients with subscapularis insufficiency following the shoulder arthroplasty [45].

The excessive soft tissue tension also should be avoided, which may result in a restricted range of motion, acromial fracture, and brachial plexus neuropraxia [46]. The factors affecting soft tissue tension are summarized in Table 7.1. The soft tissue tension should be considered before the determination of the component size. While the larger-sized components creating excessive soft tissue tension may develop early-onset soft tissue insufficiency, and so instability, small components result in soft tissue looseness leading to early-onset instability.

Table 7.1

The factors affecting the soft tissue tension

Only gold members can continue reading. Log In or Register to continue