Revision surgery of reverse shoulder arthroplasty

J Shoulder Elbow Surg (2013) 22, 1359-1370 www.elsevier.com/locate/ymse Revision surgery of reverse shoulder arthroplasty Pascal Boileau, MD*, Barbara Melis, MD, David Duperron, MD, Gr
egory Moineau, MD, Adam P. Rumian, FRCS, Yung Han, MD Department of Orthopaedic Surgery and Sports Traumatology, H^opital de L’Archet, University of Nice Sophia-Antipolis, Nice, France Background: There is limited knowledge regarding revision of reverse shoulder arthroplasty (RSA). This study assesses reasons for failure in RSA and evaluates the outcomes of revision RSA. Materials and methods: Between 1997 and 2009, 37 patients with RSA had revision surgery. Clinical and radiologic examinations performed preoperatively and at 3 months, at 6 months, and then annually postoperatively were analyzed retrospectively. Patients were reviewed with a minimum 2-year follow-up. Results: The most common causes for RSA revision were prosthetic instability (48%); humeral loosening, derotation, or fracture (21%); and infection (19%). Only 2 patients (3%) had to be reoperated on for glenoid loosening. More than 1 re-intervention was performed in 11 patients (30%) because of recurrence of the same complication or appearance of a new complication. Underestimation of humeral shortening and excessive medialization were common causes of recurrent prosthetic instability. Proximal humeral bone loss was found to be a cause for humeral loosening or derotation. Previous surgery was found as a potential cause of low-grade infection. At a mean follow-up of 34 months, 32 patients (86%) had retained the RSA whereas 2 patients (6%) had undergone conversion to humeral hemiarthroplasty and 3 (8%) to a resection arthroplasty. The mean Constant score in patients who retained the RSA increased from 19 points before revision to 47 points at last follow-up (P < .001). Conclusions: Even if revision may lead to several procedures in the same patient, preservation or replacement of the RSA is largely possible, allowing for a functional shoulder. Full-length scaled radiographs of both humeri are recommended to properly assess humeral shortening and excessive medialization before revision. Level of evidence: Level IV, Case Series, Treatment Study. Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Reversed shoulder arthroplasty; instability; infection; implant loosening; revision Reverse shoulder arthroplasty (RSA) was originally designed to treat pseudoparalysis with cuff tear arthropathy in elderly patients and was considered a ‘‘last chance’’ Ethical or review board approval is not applicable for this study. *Reprint requests: Pascal Boileau, MD, Department of Orthopaedic Surgery and Sports Taumatology, H^opital de L’Archet, University of Nice Sophia-Antipolis, 151 Route de St Antoine de Ginestiere, F-06202 Nice, France. E-mail address: [email protected] (P. Boileau). possible surgery for a functional shoulder.3,12 However, because of its success, the indications for RSA have expanded to also treat massive rotator cuff tears, failed hemiarthroplasty or total shoulder arthroplasty, acute fractures, fracture sequelae, rheumatoid arthritis, and tumors.1,4,9,16,18,22 Consequently, the number of RSAs performed and their associated complications have increased steadily. Some of these complications can be managed conservatively, whereas other complications necessitate surgical intervention including revision surgery.24 1058-2746/$ - see front matter Ó 2013 Journal of Shoulder and Elbow Surgery Board of Trustees. http://dx.doi.org/10.1016/j.jse.2013.02.004 1360 The RSA is a relatively new implant, and although there are some reports of revision RSA in the literature,8,13,17 our understanding on this topic is still limited. What are the most common complications that lead to revising an RSA? What kind of complications can be solved when revising an RSA? Is it possible to retain the RSA at the time of revision? In such a case, what is the impact of the revision surgery on the final result? These are all questions that have not yet been answered and that led us to perform a retrospective review of the patients for whom we had performed a revision of their RSA. The purposes of this study were (1) to examine the postoperative complications after RSA requiring revision, (2) to assess reasons for failure in RSA, (3) to discuss surgical strategies for revision RSA, and (4) to evaluate the outcome of revision RSA. Materials and methods A retrospective review with a minimum 2-year follow-up was conducted of all cases involving revision surgery of the RSA at our institution from 1997 to 2009 regardless of where the index RSA was performed. Revision was defined as a surgical intervention in which prosthetic components were completely or partially exchanged or removed. The patients’ surgical courses were reviewed, including operative details of their primary RSA, as well as any surgical intervention leading up to revision of their RSA. Indications for primary surgery, surgical procedures for postoperative complications, and revision surgery were tabulated. A 2-stage revision for infection was considered a single revision. Radiographic imaging and clinical outcome scores including range of motion, Constant score, patient satisfaction, and subjective shoulder value (expressed as a percentage compared with a normal shoulder) were assessed by 2 independent observers preoperatively and after patients’ revision surgery at 3 months, 6 months, and then annually until their last follow-up. Statistical analysis was performed on preoperative and postoperative data by use of descriptive statistics, as well as the Student t test or Mann-Whitney test for continuous data. Results Patient population The study consisted of 37 patients (18 men and 19 women). The mean age at primary RSA was 67 years (range, 19 to 84 years). The dominant hand was involved in 27 cases (73%). Of the patients, 28 (76%) had their primary RSA performed by the same treating surgeon at our institution and 9 (24%) had their primary RSA performed by other surgeons at outside centers. Considering that 356 primary RSAs were performed at our institution during the 12-year period studied, this represents a revision rate of 7.8%. At primary RSA implantation, a deltopectoral approach was used in 29 cases (78%) and a superolateral approach in 8 (22%). The subscapularis tendon had been reinserted in 16 of the 29 cases in which the deltopectoral approach was P. Boileau et al. used. At the time of revision, a deltopectoral approach was used in all patients. Of the patients, 32 had exchange of their prosthesis, 2 underwent conversion to hemiarthroplasty, and 3 had resection arthroplasty. For the revised implants, the following prostheses were used: Delta III (DePuy, Warsaw, IN, USA) in 23 patients, Aequalis Reverse (Tornier, Warsaw, IN, USA) in 13, and Arrow (FH Orthopedics, Mulhouse, France) in 1. A humerotomy was needed in 10 cases. Humeral fixation was obtained with the help of cerclages by use of nonabsorbable double-braided sutures. Indications for primary RSA The indications for primary RSA were failed total shoulder or hemiarthroplasty (35%), cuff tear arthropathy (27%), fracture or fracture sequelae (22%), failed rotator cuff repair (8%), and tumor (8%) (Table I). Of the patients, 25 (68%) had a history of at least 1 shoulder surgery on the affected side: humeral arthroplasty for fracture or fracture sequelae in 11 cases, open rotator cuff repair in 3, open reduction–internal fixation (ORIF) in 2, arthroscopy in 3 (long head of the biceps tenotomy, acromioplasty, debridement), anatomic total shoulder arthroplasty for post-traumatic osteoarthritis in 2, and minor surgical procedures in 4 (1 lipoma removal, 1 anterior bone block, and 2 biopsies). There was a history of preoperative infection in 1 patient and shoulder instability in 5 patients. Revision surgery for failed RSA Thirty-seven cases of revision surgery of RSA were identified (Table II). The reasons for revision were as follows: instability in 16 (43%), humeral complications in 12 (32%), infection in 9 (24%), and glenoid complications in 3 (8%). Of the patients, 32 had exchange of their prosthesis, 2 had conversion to hemiarthroplasty (1 for instability and 1 for glenoid loosening), and 3 had resection arthroplasty (all for infection). There were 21 procedures for the management of complications in addition to the revision surgery (Table II). There were 15 procedures for instability (10 closed reductions and 5 open reductions, 2 surgical evacuations for hematoma, 1 arthrolysis for stiffness, and 1 ORIF of a scapular spine fracture). The mean time between the primary RSA and first intervention was 25 months (range, 1 week to 120 months). More than 1 intervention was performed in 11 patients (30%): 2 patients had 2 interventions, 8 patients had 3 interventions, and 1 patient had 4 interventions because of recurrence or persistence of the same complication or a new subsequent complication. Instability and hematoma tended to be early complications, whereas humeral loosening and mechanical complications occurred after 1 year (Table III). Unstable RSA Prosthetic instability was the predominant cause of revision after an RSA. A total of 28 surgical interventions for Revision surgery of reverse shoulder arthroplasty Table I 1361 Summary of revision surgery of RSA categorized according to indication for primary RSA Initial diagnosis Failed HA/TSA (n ¼ 13) CTA (n ¼ 10) Fracture/fracture sequelae (n ¼ 8) Failed RCR (n ¼ 3) Tumor (n ¼ 3) Total across series Reoperation (excluding revision) Revised prosthesis Conversion to HA Prosthesis removal Total revision surgeries 5 7 6 1 2 21 12 5 7 4 4 32 d d 1 1 d 2 2 d d 1 d 3 19 12 14 7 6 58 CTA, cuff tear arthropathy; HA, hemiarthroplasty; RCR, rotator cuff repair; TSA, total shoulder arthroplasty. There was a higher incidence of failed arthroplasty and fracture treatment and a lower incidence of cuff tear arthropathy in the revision cohort compared with what has been reported for a primary RSA cohort.22 Table II Surgical treatment of 58 complications that occurred in 37 patients Complications/re-interventions No. (%) Type of treatment (n) Instability 28 (48%) Closed reduction (10)/open reduction (5) Humeral lengthening with additional metallic spacer (3) Humeral lengthening with re-implantation of long, proud humeral stem (5) Humeral lengthening with re-implantation of long, proud humeral stem þ glenoid lateralization (4) Conversion to HA (1) Humeral complications Aseptic humeral loosening (5) 12 (21%) Humeral implant derotation (5) Humeral fractures (2) Infection Glenoid/scapula complications Glenoid loosening (2) Glenoid unscrewing (1) Miscellaneous Hematoma (2) Stiffness (1) Scapular spine fracture (1) Re-interventions across series 11 (19%) Humeral stem replacement with long monoblock stem þ allograft (3) Humeral stem replacement with long stem (2) Humeral stem replacement with long monoblock stem (2) Stem replacement þ long monoblock stem þ allograft (1) Humeral stem replacement (2) Humeral stem replacement with long stem (1) ORIF with plate (1) Lavage þ debridement þ PE exchange (2) RSA replacement: 1-stage procedure (2) RSA replacement: 2-stage procedure (4) Resection arthroplasty (3) 3 (5%) Glenoid replacement (long peg þ iliac crest bone graft) (1) Conversion to HA (1) Glenoid replacement (1) 4 (7%) Evacuation þ PE exchange (2) Arthrolysis þ PE exchange (1) ORIF with plate (1) 58 HA, hemiarthroplasty; PE, polyethylene. prosthetic instability were performed in 16 patients. In 15 patients, instability was the only complication, whereas instability appeared as a new complication in 1 patient after revision for humeral implant derotation. Instability was acute (<2 months) in 81% of the patients (13 of 16) and was more frequent in patients previously operated on by a deltopectoral approach (13 of 16 patients [81%]). The supraspinatus and infraspinatus were torn in all cases, the teres minor muscle was atrophic in 8 cases, and the subscapularis tendon was absent in 10 cases (62.5%). There were no associated cases of deltoid atony or hematoma. However, 9 patients (56%) had a complete atrophy of the anterior deltoid due to previous surgery. We failed to stabilize the shoulder with conservative treatments in 67% 1362 Table III P. Boileau et al. Time of appearance of first complication after primary RSA that led to first intervention in 37 patients Acute (<2 mo) First complication (leading to first re-intervention) Instability (n ¼ 15) 12 Infection (n ¼ 7) 1 Aseptic prosthetic d loosening (n ¼ 5) Mechanical complications d (n ¼ 5) Periprosthetic fractures d (n ¼ 2) Hematoma (n ¼ 2) 2 Stiffness (n ¼ 1) d Total across series 15 (40%) (N ¼ 37) of the cases: instability recurred in 6 of the 10 cases of closed reduction and in 4 of the 5 cases of open reduction of RSA. Humeral shortening (5 to 50 mm) as measured by L€adermann et al15 was found in 11 of the 16 patients with prosthetic instability, and excessive glenoid medialization (defined as a humeral axis >15 mm medial to the lateral border of the acromion) was found in 8 patients (Fig. 1). Restoration of contralateral humeral length and a stable shoulder was successfully obtained by use of an additional metallic spacer with thicker polyethylene in 3 patients in whom shortening was less than 15 mm. In the remaining patients (with >15 mm of proximal humeral bone loss), removal of the prosthesis was needed to re-implant a longer stem proudly (ie, higher than the theoretical position of the greater tuberosity). Humeral lateralization was obtained by changing the glenosphere from 36 mm to 42 mm in 5 cases, by performing an additional iliac crest bone graft under the baseplate in 2 cases, and by using a custom lateralized glenosphere in 1 case. Humeral complications Humeral complications were the second most common reason to revise an RSA (Tables II and III). Humeral loosening or derotation was present in 10 cases and humeral fracture in 2 cases. Humeral shortening with the presence of proximal humeral bone loss (due to tuberosity migration, lysis, or excision) was found in the 5 patients who had aseptic humeral loosening and in the 5 patients who had humeral implant derotation (2 on the left and 3 on the right) as a result of unscrewing between the diaphyseal and epiphyseal parts of the stem (P < .0001). The humeral bone loss was superior to 30 mm in all cases of humeral loosening and implant derotation. All the loose and derotated stems were revised. At the time of surgery, we observed significant polyethylene wear of the humeral cup and some metallosis in the case of Subacute (2-12 mo) Late (>12 mo) 2 2 d 1 4 5 d 5 d 2 d d 4 (11%) d 1 18 (49%) implant derotation. In addition, we observed rotation of the humeral stem in the medullary canal when moving the arm in rotation. For these reasons, we considered that humeral loosening was related to both biological (polyethylene/ metallic debris) and mechanical (rotational forces) causes. In 5 cases, a monoblock reverse stem was used to reduce excessive rotational constraints and thus to prevent recurrent humeral implant unscrewing. In 3 cases, structural proximal humeral allograft was used to reconstruct the bone stock in an effort to decrease the stresses to the fixation of the distal humeral stem (Figs. 2 and 3). In these cases, in which the bone loss was inferior to 5 cm and the patient was elderly, reconstruction of the proximal humerus was performed with a cement mantle around the prosthesis (Fig. 4). Infected RSA A total of 11 re-interventions for infection were performed in 9 patients. Of the 9 patients with infected RSAs, 6 (67%) had undergone previous surgery before the index procedure (2 cases of failed ORIF of a proximal humeral fracture with subsequent total shoulder arthroplasty for fracture sequelae, 2 cases of failed rotator cuff repair, 1 case of hemiarthroplasty for fracture, and 1 case of an anterior bone block procedure for shoulder instability). In 7 patients, the infection was the only complication. Infection appeared as a new complication in 1 patient after multiple reoperations for instability and in 1 patient after revision of the RSA for a mechanical complication (glenosphere disassembly). On microbiological cultures, we identified the following: Propionibacterium acnes (5 patients), P acnes associated with coagulase-negative Staphylococcus (1 patient), coagulase-negative Staphylococcus (1 patient), Staphylococcus epidermidis (1 patient), and Staphylococcus aureus (1 patient). Two patients underwent simple lavage and debridement with a poor functional outcome and had persistent infection Revision surgery of reverse shoulder arthroplasty 1363 Figure 1 Case of subsequent revision surgeries in the same patient for instability, humeral fracture, and humeral implant derotation. (A) Patient with proximal humeral fracture sequelae after failed ORIF. (B) The RSA was implanted too low, leading to recurrent episodes of dislocation 2 weeks after surgery. (C) After failed closed reduction, the patient was reoperated on to lengthen the humerus: a stable shoulder was successfully obtained by use of an additional metallic spacer with a thicker polyethylene cup. (D) Three years later, the patient sustained a humeral fracture treated with a plate, and 5 years later, he came back with complete humeral implant derotation as a result of unscrewing between the diaphyseal and epiphyseal parts of the stem. (E) Bilateral scaled radiographs allowed us to determine the theoretical height of the prosthesis. (F) Third revision surgery: After removal of the previous stem, a long monoblock stem was implanted proud to restore humeral length. requiring subsequent interventions (resection arthroplasty in one and 2-stage revision in the other). A single-stage revision led to the eradication of the infection in one patient and failed in the other patient. The infection was eradicated in all 4 two-stage revisions. Resection arthroplasty was performed early in the series in 3 patients with infected RSAs, eradicating the infection in all cases. Biopsy was performed at every revision surgery, and scintigraphy was performed at follow-up to monitor infection. Glenoid loosening and disassembly There were 2 cases of aseptic glenoid loosening, both related to technical errors in baseplate implantation: 1 was too high with superior tilt and 1 had been implanted in association with a bone graft with a central peg that was too short and did not reach the native bone (Fig. 5). A glenosphere was re-implanted lower (flush to the inferior glenoid rim) and with some inferior tilt after reconstruction of the glenoid bone stock with a structural iliac crest bone graft and a long-peg glenoid. A single case of disassembly of the glenosphere from the baseplate was observed in a first- generation Delta prosthesis (DePuy) and was associated with baseplate loosening that required revision. This patient subsequently had a recurrent infection that ultimately led to a resection arthroplasty. Shoulder function and outcome Functional results were evaluated in the 32 patients who retained their RSA. At a mean follow-up of 36 months, the mean Constant score improved significantly, from 19 points (range, 5 to 65 points) before revision to 47 points (range, 15 to 77 points) after revision (P < .0001). The mean pain score at last follow-up was 10 of 15 points (range, 1 to 15 points). At the last review, the mean active anterior elevation was 111 (range, 30 to 170 ), the mean active external rotation was 7 (range, 20 to 50 ), and functional internal rotation assessment showed that a patient’s hand could reach the buttock level on average. The mean subjective shoulder value was 50% (range, 10% to 90%), whereas 89% of the patients (24 of 27) were satisfied or very satisfied with the revision procedure. No significant difference was found in functional results between the 1364 P. Boileau et al. Figure 2 Case of revision surgery for aseptic humeral loosening with implant derotation because of proximal bone loss. (A) An RSA was implanted for failed hemiarthroplasty for fracture with tuberosity migration and lysis. (B) Ten years after RSA implantation, the patient came back with pain and loss of active elevation: The radiograph shows humeral loosening, implant derotation, and severe proximal bone loss. (C) Revision was performed with a monoblock humeral long stem (to counteract derotation forces) associated with structural proximal humeral allograft (to provide implant stability and improve deltoid tension). (D) The postoperative radiograph shows good incorporation of humeral allograft and chevron osteotomy to reduce excessive rotational constraints. patients operated on only once and those operated on more times for recurrent or associated complications. Discussion This article reports our experience of revision surgery of failed or complicated primary RSA. In agreement with previous reports,8,11,13,16,19,21-24 we found that instability, humeral complications (aseptic loosening, implant derotation, and fractures), and infection are the most common complications requiring surgical re-intervention after RSA. Similar to other series,1,3,8,21,23 we observed that complications can be associated with one another or occur subsequently and that interventions can lead to several procedures in the same patient. However, our results of revising a failed RSA are encouraging: although revision may have required several procedures in the same patient, Revision surgery of reverse shoulder arthroplasty 1365 Figure 3 Case of revision surgery for aseptic humeral loosening after RSA implanted for tumor. (A) Osteosarcoma of proximal humerus in 18year-old woman. (B) Resection of tumor and reconstruction with cemented, massive reverse prosthesis. (C) A radiograph obtained 6 years after surgery shows humeral loosening with distal perforation of the humerus by the stem and severe bone loss. (D) Postoperative radiograph showing custom-made monoblock, long stem associated with structural proximal allograft - in this case, a femoral allograft was used, and the prosthesis is uncemented with locking screws to counteract rotational forces. (E) Good functional results were observed 2 years after revision surgery. a revision RSA was possible in 86% of the patients (32 of 37), allowing preservation of shoulder function. Whereas shoulder function after RSA revision is not as good as in primary RSA (mean Constant score of 47 points compared with 58 points in our previous series of primary RSA2), 89% of the patients did benefit from the procedure and were satisfied. The risk factor for revision RSA in this study appears to be implantation of a primary RSA for previous failed surgery. Our revision RSA cohort shows that previous failed arthroplasty (35%), failed treatment for fracture/ fracture sequelae (22%), and failed cuff repair (8%) are etiologies at risk. These findings confirm our previous experience with primary RSA and that of other authors.2,22 In a large series of 240 cases, Wall et al22 also found that patients who received primary RSA for failed arthroplasty or post-traumatic arthritis had worse results and more complications than patients who received RSA for cuff tear arthropathy, osteoarthritis with cuff tear, and massive cuff tear. Our study shows that revision surgery of a failed or complicated RSA is a high-risk surgery, considering that 30% of the patients had subsequent complications after reoperation and needed further surgical interventions. The reason for this high rate of re-intervention in the same patients is clearly linked to our underestimation and underdiagnosis of humeral bone loss and/or associated low-grade infection. This was especially true in our early experience when revising reverse shoulder prostheses in patients with previous failed surgery. Prosthetic instability was the predominant cause of revision surgery and the most difficult complication to treat, evident by the high recurrence rate.3,10,21,24 An important finding of our study is that patients with humeral shortening because of proximal humeral bone loss (related to 1366 P. Boileau et al. Figure 4 Intraoperative views showing humeral reconstruction in case of limited bone loss (<5 cm) in an elderly patient. (A) Incomplete humeral osteotomy with preventive double suture cerclages in place and use of monoblock (fracture) stem prosthesis. (B) Reconstruction of proximal epiphysis with cement around the prosthesis and tied suture cerclages to close the humerotomy. tuberosity migration, lysis or excision after fractures, fracture sequelae, failed hemiarthroplasty, or tumor) and excessive medialization are at risk for instability. A first attempt at closed reduction of the dislocated RSA failed in 67% of the cases of this series, mainly because we underdiagnosed and underestimated humeral shortening and excessive glenoid medialization. At the time of revision surgery, neglecting or ignoring such humeral shortening led us to re-implant a humeral component too low and/or too medialized, which leads to insufficient deltoid tensioning and recurrent shoulder instability.2,15 Restoring deltoid tension can be difficult when revising a reverse prosthesis because the surgical landmark of the proximal epiphysis is often missing, such as in a failed prosthetic replacement for fracture or after RSA for fracture sequelae with tuberosity migration and lysis.2,15 Thus, humeral shortening (because of bone loss and/or implantation of the previous humeral component that is too low) and excessive medialization (because of glenoid bone loss and/or use of a sphere that is too small) must be anticipated before RSA revision, by asking for preoperative, fulllength, scaled radiographs of both humeri (Fig. 1). This imaging study is needed (1) to quantify humeral shortening by measuring bilateral humeral lengths according to L€adermann et al15 and (2) to quantify humeral medialization by measuring the distance between the humeral axis and the lateral border of the acromion (horizontal acromiohumeral distance). By preoperative templating, the surgeon can determine the theoretical position in height of the revision humeral implant (ie, higher than the theoretical position of the greater tuberosity) and how much lateralization is needed. On the basis of our experience from this series, we have reconsidered our approach to address the unstable RSA and have developed an algorithm that takes into account both humeral shortening and excessive medialization (Fig. 6). If the shortening is less than 15 mm (with no prosthetic stem malrotation or loosening) and if there is no excessive medialization (humeral axis <15 mm medial to lateral acromion), the problem can be easily solved (depending on the RSA prosthesis) with an additional metallic spacer and/ or thicker polyethylene insert (Fig. 1). However, if the shortening is greater than 15 mm, the surgeon should anticipate exchanging the humeral stem and implanting a longer cemented stem to the appropriate height (ie, prouder). Next, if there is excessive medialization (humeral axis >15 mm medial to acromion) or persistent prosthetic instability despite correct humeral length restoration, the surgeon should increase the glenoid offset or lateralize the glenosphere and/or reconstruct the glenoid bone loss to gain more stability. Changing a small-diameter sphere (36 mm) by implanting a larger sphere (42 mm) can increase stability by increasing the tension on the deltoid by lateralizing and lowering the humerus, as well as by using a larger, deeper polyethylene cup. This is a simple procedure, and it was performed in 7 cases in our series with success. In cases in which lateralization is still insufficient, glenoid offset can be increased by implanting a metallic lateralized glenoid component and/or by placing a bone graft under a long-peg baseplate (Bony-Increased Offset Reverse Shoulder Arthroplasty [BIO-RSA]; Tornier, Inc., Bloomington, MN, USA).7,11 We also try to position the baseplate and sphere with a slight inferior tilt to increase coaptation between humeral and glenoid implants. Finally, reinsertion of the subscapularis tendon or the remaining anterior soft tissue must be systematically performed, and immobilization of the arm in a splint with 60 of abduction for 6 weeks is part of our treatment plan. Revision surgery of reverse shoulder arthroplasty 1367 Figure 5 Case of revision surgery for glenoid loosening after technical mistake. (A) Cuff tear arthropathy with severe glenoid bone loss in a 82-year-old woman receiving cortisone for many years. (B) Index RSA with autologous bone graft harvested from humeral head. (C) Because the central peg was too short and did not reach the native bone, glenoid loosening appeared 1 year after implantation with screw breakage. (D) Glenoid revision was performed with iliac crest bone graft and use of a long-peg glenoid in the native scapula. Humeral complications were the second most common reason necessitating revision of an RSA (Fig. 2). Our study shows that humeral bone loss is not only a cause of instability but also a cause of humeral loosening (because of excessive rotational forces at the cement-implant interface or at the cement-bone interface) and humeral implant derotation (because of excessive rotational forces within the implant, leading to unscrewing between the diaphyseal and epiphyseal parts of the stem). These findings are in accordance with a recent biomechanical study that has shown that the absence of a proximal epiphysis creates excessive rotational forces, leading to humeral implant loosening and/ or implant derotation.7 Our clinical experience supports that modular components are at risk of mechanical failure in the presence of proximal humeral bone loss. We, therefore, prefer to use a monoblock stem with proximal humeral allograft to reduce excessive rotational and varus-valgus constraints (Fig. 3). As emphasized by Chacon et al,5 the humeral allograft provides additional humeral stem stability, provides protection from humeral loosening, and restores proximal humeral bone stock, which is helpful to maintain the height of the prosthesis-bone construct and thus deltoid tension. In cases in which proximal bone loss was inferior to 5 cm and the patient was elderly, reconstruction of the proximal humerus was performed with cement around the prosthesis (Fig. 4). Infection was the third most common reason for revision. As shown by our study, low-grade infection after RSA occurred more frequently after previous surgery (ORIF or failed anatomic prosthesis or cuff repair). Lavage with debridement of soft tissues did not work in our experience, and we have stopped proposing this therapeutic option to our 1368 P. Boileau et al. Figure 6 (A) Algorithm describing our strategy for the treatment of the unstable RSA. In treating instability, if the humeral length discrepancy is less than 15 mm and if the medialization discrepancy is less than 15 mm, adding a metallic spacer and thicker polyethylene (PE) with a larger sphere is a successful option. (B) If the length discrepancy is greater than 15 mm and/or medialization is greater than 15 mm, increasing the humeral length with a longer and more proud humeral stem or increasing the glenoid offset with additional bone graft and/or lateralized glenoid component is mandatory. patients, except in some acute cases.6,14 In our opinion, resection arthroplasty should be performed only in fragile patients with resistant microbial agents and after failed attempts to eradicate the infection with revision and adapted antibiotic treatment. On the basis of our experience from this series, we recommend a 2-stage revision for the treatment of deep infection after RSA, although we acknowledge that this is based on the results of only a few patients. Surgeons should also be aware that the risk of intraoperative fracture increased with the number of revisions. We now do not hesitate to perform a formal humerotomy (10 cases in this series) if we anticipate difficult humeral prosthesis extraction.20 This study is a retrospective cohort study, prone to selection bias, and the series is small and heterogeneous with a mean follow-up of 34 months. Despite these limitations, this study represents valuable clinical experience of treating complications of RSA, highlighting which complications are the most difficult to treat successfully, allowing recommendations to be made with regard to management strategies and providing information to guide surgeons as to the expected outcomes after intervention. The different underlying causes of failures are analyzed separately, and the results of the different surgical treatments are reported. Other strengths of this study include examination by independent observers, minimal loss to follow-up (despite the advanced age of many of the patients), and detailed clinical and radiologic analysis. Conclusions In addressing the purposes of this study, we conclude the following: 1. The most frequent causes for revision surgery after a failed RSA are prosthetic instability, humeral loosening or derotation, and infection. Surgeons must anticipate that these complications can be associated to treat them all at the first revision surgery and avoid further re-interventions in the same patient. 2. Previous failed surgery is a risk factor for revision RSA, specifically failed arthroplasty (35%), failed treatment for fracture or fracture sequelae (22%), and failed cuff repair (8%). Revision surgery of reverse shoulder arthroplasty 3. Humeral shortening (ie, proximal bone loss related to tuberosity migration, lysis, or excision) and excessive medialization are prevalent in instability and are underestimated by the surgeon. Thus, in treating prosthetic instability, lengthening (thicker polyethylene, metallic spacer, or re-implantation of a prouder/longer humeral stem) and lateralizing the humerus (larger/lateralized glenosphere with or without glenoid bone grafting) must both be considered. 4. Humeral shortening or proximal bone loss (>50 mm) is also prevalent in aseptic humeral loosening or implant derotation. Thus, in the treatment of aseptic humeral loosening or derotation, a monoblock humeral stem with a structural proximal humeral allograft should be considered to reduce excessive rotational and varus-valgus constraints. 5. Previous multiple failed surgeries are a risk factor for low-grade infection and are also underestimated and underdiagnosed by the surgeon. In the treatment of infection, a 2-stage revision gives predictable success. 6. Before revising a failed RSA, the surgeon must anticipate both mechanical and biological problems by systematically asking for (1) full-length, scaled radiographs of both humeri, which are mandatory to properly assess humeral shortening and excessive medialization, and (2) CRP (C-reactive protein), bone scan, articular puncture, and biopsies, which are mandatory to eliminate a possible associated low-grade infection. 7. In case of humeral bone loss and/or low-grade infection, the surgeon must be prepared to exchange the humeral component. A controlled humerotomy is strongly recommended to avoid intraoperative fracture. 8. Providing that one has a clear surgical strategy, preservation of shoulder function with a a revision RSA, preservation of shoulder function with a revision RSA is largely possible. Conversion to hemiarthroplasty or resection arthroplasty remains as an ultimate salvage procedure when options for revision surgery have been exhausted or in the case of persistent infection in a very frail patient. Disclaimer Pascal Boileau reports that he has received royalties from Tornier for work related to the subject of this article. All the other authors, their immediate families, and any research foundations with which they are affiliated have not received any financial payments or other benefits from any commercial entity related to the subject of this article. 1369 References 1. Affonso J, Nicholson GP, Frankle MA, Walch G, Gerber C, GarzonMuvdi J, MccFarland EG. Complications of the reverse prosthesis: prevention and treatment. Instr Course Lect 2012;61:157-68. 2. Boileau P, Gonzalez JF, Chuinard C, Bicknell R, Walch G. Reverse total shoulder arthroplasty after failed rotator cuff surgery. J Shoulder Elbow Surg 2009;18:600-6. http://dx.doi.org/10.1016/j.jse.2009. 03.011 3. 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