5 Emerging Indications for Reverse Total Shoulder Arthroplasty

10.1055/b-0037-146566

5 Emerging Indications for Reverse Total Shoulder Arthroplasty

Tyler J. Brolin and Thomas W. (Quin) Throckmorton

Abstract

Reverse total shoulder arthroplasty (RTSA) was initially developed and indicated for the treatment of cuff tear arthropathy in elderly low-demand patients. The ability to reliably restore shoulder elevation and abduction in the cuff-deficient shoulder was a significant advance in shoulder surgery. The success of this operation and the concomitant increase in surgeon confidence have led to the emergence of new indications for reverse arthroplasty, including comminuted proximal humeral fractures, glenoid bone loss, proximal humeral bone loss, and massive rotator cuff tears without arthritis. This chapter discusses and analyzes these newer indications for RTSA, as well as the available literature on them.

5.1 Introduction

In the past, the complex problem of an irreparable rotator cuff tear with humeral head superior migration and glenohumeral arthritis (cuff tear arthropathy [CTA]) presented a unique challenge to the shoulder surgeon. Unconstrained hemiarthroplasty was the standard of care, albeit with the surgeon and patient accepting Neer’s limited goals of pain relief with restricted shoulder function. The cuff-deficient shoulder presented a biomechanical challenge, and not until the introduction of the Grammont reverse prosthesis was there a viable option to obtain reliable shoulder elevation and abduction. This semiconstrained prosthesis with a center of rotation at the glenoid–implant interface and increased deltoid tension created a stable fulcrum that allowed patients to achieve greater shoulder elevation. This became its first indication, and since the late 1980s, reverse total shoulder arthroplasty (RTSA) has been used to treat CTA in low-demand elderly patients in Europe. It subsequently became available in the United States in 2004 after the approval of Food and Drug Administration.

Early clinical outcome data became available illustrating the RTSA’s ability to reliably restore overhead shoulder elevation in patients with CTA. This increased confidence with the prosthesis has resulted in an emergence of new indications as well as a rapid rise in the number of RTSAs implanted each year. An analysis of Medicare Part A data by Day et al showed RTSA made up 37% of all shoulder arthroplasties performed. ¹ Of these, 22% were performed for the diagnosis of shoulder osteoarthritis without rotator cuff pathology. RTSA is also being used increasingly for comminuted proximal humeral fractures. Rosas et al examined a Medicare patient population database and found nearly a threefold increase in percentage of RTSA for this indication. ² From 2009 to 2012, the percentage of RTSAs for proximal humeral fractures increased from 11 to 28%, corresponding with a reduction in hemiarthroplasty usage.

Still, there is some concern regarding the use of RTSA in younger patients with higher demand shoulders. While there is no consensus on the appropriate age of implantation, most would agree it is best suited for elderly low-demand patients; however, there are situations in which RTSA becomes one of the only salvage options. Recently, studies have begun to examine clinical outcomes in patients younger than 65 years. Sershon et al retrospectively reviewed 36 shoulders with a mean age of 54 years with an average follow-up of 2.8 years. ³ All postoperative outcome scores showed statistically significant improvement, especially in forward flexion, which increased from 56 to 121 degrees. Of note, 83% of patients had previous surgery and the average was 2.5 procedures per patient. A study by Ek et al followed 41 patients with 46 RTSAs for massive irreparable rotator cuff tears for a mean of 93 months. ⁴ Significant improvements were seen in mean relative Constant score, subjective shoulder value, active forward elevation, pain score, and strength. More importantly, implant survivorship was 98% at 5 years and 88% at 10 years, although the overall complication rate was high at 37.5%. These results are promising and have contributed to mitigating the age-based reservations.

Emerging indications for RTSA include comminuted proximal humeral fractures, posttraumatic sequelae, proximal humeral bone loss, glenoid bone loss, and massive irreparable rotator cuff tears in the elderly. Each of these indications for RTSA was born out of the lack of dependable reconstruction options in these clinical situations, most notably the unreliability of unconstrained anatomic shoulder arthroplasty. There are, however, limited long-term, high-level clinical data currently available to support the use of RTSA for these indications, and enthusiasm should be appropriately tempered until those results become available.

5.2 Proximal Humeral Fractures

Proximal humeral fractures are the third most common fracture in patients older than 65 years, behind only hip and distal radial fractures. As our population continues to age, the frequency of these fractures is expected to rise. The vast majority of these fractures can be treated nonoperatively with predictably good results. The advent of proximal humeral locking plate osteosynthesis has been a valuable addition to the surgeon’s options for treating these fractures. Elderly patients, however, are more likely to sustain comminuted three- and four-part fractures and/or fracture–dislocations, which present a different challenge and often are not appropriate for open reduction and internal fixation because of poor bone quality and an unacceptable complication rate attributed to osteonecrosis, loss of fixation, and screw cutout. Three- and four-part fractures, fracture-dislocations, and fractures with wide displacement in the medial calcar are risk factors for a poor outcome with fixation procedures in the elderly population.

In the past, hemiarthroplasty has been the reconstructive option of choice for these fractures. This became a source of frustration because hemiarthroplasty is a technically demanding operation and, despite satisfactory intraoperative execution, it often led to unpredictable results. The clinical outcomes had a bimodal distribution and were strongly dependent on healing of the greater and lesser tuberosities. Problems with tuberosity resorption, nonunion, and malunion were frequent, especially with comminuted and osteoporotic fractures. This unfortunately led to poor outcomes. However, if the tuberosities did heal in an anatomic location, the results were often quite good.

Since satisfactory shoulder function after RTSA is not solely governed by tuberosity healing, it was proposed as an option for three- and four-part proximal humeral fractures in elderly patients. Early clinical outcomes began to show more consistent and predictable outcomes. Cuff and Pupello compared hemiarthroplasty and RTSA for proximal humeral fractures in elderly patients in a prospective cohort with greater than 2 years of follow-up. ⁵ American Shoulder and Elbow Surgeons (ASES) scores and Simple Shoulder Test (SST) scores were higher for the RTSA group and forward elevation was increased with RTSA (139 degrees), compared to hemiarthroplasty (100 degrees). There also was higher patient-reported satisfaction in the RTSA cohort (91 vs. 61%). Chalmers et al prospectively evaluated patients who had RTSA for proximal humeral fractures and matched them with age- and sex-matched control groups of patients who had hemiarthroplasty and open reduction and internal fixation. ⁶ Although the numbers in each group were small, significantly more patients in the RTSA group achieved more than 90 degrees of forward elevation and more than 30 degrees of external rotation. The average numbers of physical therapy sessions were 2.2, 47.7, and 43.6, respectively, for RTSA, hemiarthroplasty, and open reduction and internal fixation groups. When the cost of implants and physical therapy sessions were analyzed, RTSA compared favorably, which may provide an overall cost savings. A systematic review of 15 studies that met inclusion criteria echoed these results. ⁷ RTSA had on average 21 degrees greater forward elevation and higher outcome scores, but did have slightly less external rotation. Importantly, there was no difference in the complication rate.

There are some relevant technical considerations when considering reverse arthroplasty for fracture. First, intraoperative attention to deltoid tension is important to decrease the risk of postoperative dislocation and maximize the deltoid lever arm. Second, and still controversial, there is evidence that tuberosity repair positively affects clinical outcomes and active range of motion. Gallinet et al retrospectively reviewed patients who had RTSA for fractures and had either tuberosity repair or resection. ⁸ Of the patients who had tuberosity repair, 66% of the greater tuberosities and 100% of the lesser tuberosities healed. Constant scores and all areas of motion were significantly better in the group with tuberosity repair compared to those with no repair. Mean shoulder elevation was 117 degrees in the repair group compared to 95.7 degrees in the resection group. External rotation at the side was 14.8 degrees and at 90 degrees of abduction was 37.8 degrees for the repair group and 0 and 3.6 degrees, respectively, in the group without tuberosity repair. Outcomes improved even further with tuberosity consolidation.

5.3 Glenoid Bone Loss

The traditional indication for RTSA and many of the emerging indications center on the presence of a nonfunctional rotator cuff due to rotator cuff tear, fracture, proximal humeral bone loss, or malunion. However, this has recently been expanded to include a subset of patients with glenohumeral arthritis with glenoid bone loss and an intact rotator cuff. The anatomic total shoulder arthroplasty has been successful in treating glenohumeral osteoarthritis with good functional results, pain relief, and long-term survivorship; however, glenoid component loosening remains the main indication for revision. Eccentric loading of the glenoid component is associated with the increased likelihood of loosening due to a “rocking horse” phenomenon. Excessive glenoid retroversion and posterior humeral head subluxation appear to be risk factors for early failure. Increased retroversion may be involved not only in glenoid loosening but also in inferior functional results and decreased patient satisfaction. Correction of glenoid retroversion to less than 10 degrees has been recommended, but it is technically demanding and in certain situations is not feasible because of excessive wear.

Walch et al studied the use of RTSA to treat glenohumeral osteoarthritis in cuff-intact patients with a biconcave or Walch type B2 glenoid because of their experience with the anatomic unconstrained shoulder arthroplasty in this situation. They retrospectively reviewed 92 anatomic total shoulder arthroplasties in patients with primary osteoarthritis and a biconcave glenoid. ⁹ At an average of 77 months, there was a revision rate of 16.3% and a glenoid loosening rate of 20.6%. Importantly, factors associated with glenoid loosening included depth of posterior bone erosion, humeral head subluxation, and glenoid retroversion. In this study, the complication rate was 62% when the intermediate glenoid retroversion was greater than 30 degrees and only 20% when less than 30 degrees.

Current options for managing glenoid bone loss include asymmetric reaming, bone grafting, augmented glenoid components, and RTSA. Eccentric reaming or “high-side reaming” is effective in cases of lesser deformity, but should be limited to 15 degrees of correction because of the loss of bone stock and the risk of vault penetration with greater correction. ¹⁰ , ¹¹ Posterior glenoid bone grafting is an option to restore the glenohumeral joint line as well as glenoid version. Some authors have reported success with this technique. Potential complications include graft resorption, nonunion, loss of fixation, and implant subsidence. Recently, a stepped, posterior augmented glenoid component has been introduced as an alternative to glenoid bone graft. This theoretically eliminates graft-related complications while also allowing correction of glenoid deformity. Data are limited on this implant, and future long-term studies are needed. Also, both glenoid bone grafting and placement of an augmented glenoid are technically demanding operations and concerns for reproducibility are justified.

To our knowledge, the first study to examine the use of RTSA for primary glenohumeral osteoarthritis with a biconcave glenoid was reported by Mizuno et al. ¹² This was a retrospective review of 27 RTSAs implanted in the setting of Walch B2 glenoids with more than 2 years of follow-up. The Constant score increased from 31 preoperatively to 76 postoperatively, and 93% of patients were satisfied. Active forward elevation increased from 89 to 152 degrees and external rotation increased from 3 to 27 degrees postoperatively, both statistically significant. The complication rate was 15%, with glenoid loosening seen in one patient and no postoperative posterior instability. The authors concluded that RTSA is a viable option to treat static posterior glenohumeral instability and severe glenoid erosion. The results of this study are certainly promising for this difficult situation; however, further long-term reports are needed to confirm the success of this strategy to treat glenoid bone loss.

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