Reverse shoulder prosthesis in the treatment of locked anterior shoulders: a comparison with classic reverse shoulder indications

ARTICLE IN PRESS J Shoulder Elbow Surg (2016) ■■, ■■–■■

www.elsevier.com/locate/ymse

Reverse shoulder prosthesis in the treatment of locked anterior shoulders: a comparison with classic reverse shoulder indications Jennifer Kurowicki, BSa, Jacob J. Triplet, BSb, Enesi Momoh, MDa, Molly A. Moor, PhDa, Jonathan C. Levy, MDa,* a

Holy Cross Orthopedic Institute, Fort Lauderdale, FL, USA College of Osteopathic Medicine, Nova Southeastern University, Fort Lauderdale, FL, USA

b

Background: Locked anterior shoulder (LAS) with static instability and anterior glenoid bone loss is challenging in the elderly population. Reverse shoulder arthroplasty (RSA) has been employed in treating these patients. No study has compared RSA for LAS with classically indicated RSA. Methods: A retrospective case-control study of patients treated with RSA for LAS with glenoid bone loss and static instability was performed using matched controls treated with primary RSA for classic indications. Twenty-four cases and 48 controls were evaluated. Average follow-up was 25.5 months, and median age was 76 years. Motion, outcome assessments, and postoperative radiographs were compared. Results: Preoperatively, LAS had significantly less rotation and lower baseline outcome scores. Glenoid bone grafting was more common (P = .05) in the control group (26%) than in the LAS group (6.3%). Larger glenospheres were used more often (P = .001) in the LAS group (75%) than in the control group (29%). Both groups demonstrated significant improvements in pain, function, and outcome scores. Postoperatively, the control group had significantly better elevation and functional outcome scores. With the exception of flexion and Simple Shoulder Test score, effectiveness of treatment was similar between groups. Postoperative acromion stress fractures were seen in 21% of LAS patients and 9% of controls (P = .023) with a predominance of type 3 fractures in LAS. Two LAS patients remained dislocated. Conclusion: Patients with LAS treated with RSA can anticipate improvements in pain and function by use of larger glenospheres, often without the need for glenoid bone grafting. Worse postoperative motion and function and a higher incidence of acromion stress fracture may be expected. Level of evidence: Level III; Retrospective Cohort Comparison; Treatment Study © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. Keywords: Reverse shoulder; anterior instability; shoulder dislocation; glenoid bone loss; shoulder subluxation; acromion fracture

All work was performed at the Holy Cross Orthopedic Institute and Holy Cross Hospital. This study was approved by the Western Institutional Review Board: No. 1-902142-1. *Reprint requests: Jonathan C. Levy, MD, Holy Cross Orthopedic Institute, 5597 N Dixie Highway, Fort Lauderdale, FL 33334, USA. E-mail address: [email protected] (J.C. Levy).

Reverse shoulder arthroplasty (RSA) has become a reliable treatment alternative for end-stage arthropathy with combined rotator cuff deficiency, representing the classic indications for the primary RSA.7,11 More recently, RSA is being used to treat additional primary pathologic processes, such as fracture sequelae,3,40 acute proximal humerus fractures,9

1058-2746/$ - see front matter © 2016 Journal of Shoulder and Elbow Surgery Board of Trustees. All rights reserved. http://dx.doi.org/10.1016/j.jse.2016.04.019

ARTICLE IN PRESS 2 osteoarthritis with static posterior subluxation,26 and locked anterior dislocations with glenoid bone loss.37 As these indications expand, it is important to recognize that not all patients treated with RSA will have similar outcomes. This has been most clearly demonstrated in comparing primary and revision RSA,3,33 but it is less appreciated for other indications. RSA has been used to treat locked anterior shoulder (LAS) in the elderly population, as management of rotator cuff deficiency together with glenoid and humeral bone loss is possible.19,37 Management of glenoid bone loss is these patients can be the most challenging aspect of these cases, often requiring bone grafting behind the glenoid baseplate. Werner et al37 reported on the successful treatment of a series of 21 patients with locked anterior dislocations, all of whom required glenoid bone grafting. In this series, 2 patients (9.5%) required revision because of baseplate loosening.37 Whereas the reports using RSA for locked anterior dislocations have been promising, no study has compared the outcomes with those of patients with more classic indications for RSA. The purpose of this study was to investigate the differences in clinical and radiographic outcomes of patients treated with RSA for LAS compared with RSA patients treated for more classic indications. Our hypothesis was that patients treated with LAS would have poorer clinical outcomes with higher complication rates.

Materials and methods A retrospective case-control study of prospectively collected data from a consecutive series of patients with primary RSA for LAS was performed. Patients treated with revision shoulder arthroplasty were excluded. Cases included patients with LAS with glenoid bone loss and static instability who were treated with RSA, and controls were patients who underwent RSA for classic indications (classic rotator cuff tear arthropathy, severe arthritis with rotator cuff deficiency, massive irreparable rotator cuff tear with pseudoparesis). All RSA procedures were performed by the senior author (J.C.L.) through a deltopectoral approach with the same implant system (Reverse Shoulder Prosthesis; DJO Surgical, Austin, TX, USA). Glenosphere sizes were selected on the basis of the patient’s size and concern for joint stability. Four different glenosphere sizes were used: 32 neutral (10-mm lateralized center of rotation), 32 minus 4 (6-mm lateralized center of rotation), 36 neutral (6-mm lateralized center of rotation), and 36 minus 4 (2-mm lateralized center of rotation). Preoperative computed tomography imaging was obtained in all patients to assess glenoid bone loss and possible need for glenoid bone grafting. Glenoid bone graft, using humeral head autograft, was performed if <50% of the native glenoid would be supported by the baseplate. This decision was made during glenoid preparation. A retrospective search of our Institutional Outcome Shoulder Repository identified 24 patients who underwent RSA for LAS (cases) meeting the inclusion criteria of known LAS. Twenty-one patients were found to have chronic LAS, and 3 had acute LAS with glenoid fractures. All patients had similar disease of anterior glenoid bone loss leading to locked dislocation or subluxation with static instability. All but 1 patient had rotator cuff deficiency. Two controls were matched for each case on the basis of age, gender, hand dominance, and side of surgery. The control group thus consisted of 48

J. Kurowicki et al. Table I

Demographic characteristics

Variable

Locked anterior shoulder* (N = 24)

Control* (N = 48)

Age (years) Gender Male Female Operative side Right Left BMI (kg/m2)

76 (72-83)

77 (73-81)

6 (25) 18 (75)

11 (23) 37 (77)

14 (58) 10 (42) 27 (23-30)

27 (56) 21 (44) 27 (24-33)

BMI, body mass index. * Median (interquartile range) or number (%).

patients. The combined patient population in this study consisted of 55 women and 17 men, with a median age of 76 years (interquartile range, 73-81) and a median length of follow-up of 25.5 months (interquartile range, 17-37; Table I). Baseline preoperative and the most recent postoperative comparisons were made using a 10-point visual analog scale (VAS) score for pain and function,1,29 the American Shoulder and Elbow Surgeons (ASES) score,25,31 the Simple Shoulder Test (SST) score,23 the Single Assessment Numeric Evaluation score,39 the 12-Item Short Form Health Survey (SF-12) score,36 and the range of motion measured by an independent examiner using a goniometer. In addition, subjective satisfaction with outcome was assessed. Efficacy of treatment, as defined by Goldberg et al,12 was compared by determining the change in outcome observed. Complications were identified by chart review and thorough review of consecutive postoperative radiographs. Radiographic analysis was based on review of the most recent postoperative radiographs. These radiographs were examined by the senior author (J.C.L.) for the presence of scapular notching according to the method described by Sirveaux et al,34 humeral and glenoid component loosening,13 presence of acromion fracture based on the Levy classification,21 and recurrent anterior dislocation. Postoperative computed tomography imaging was obtained if radiographs were inconclusive and clinical suspicion was evident.

Statistical analysis Appropriate descriptive statistics, including medians with interquartile ranges, were computed for each of the examined variables. Wilcoxon signed rank tests were performed to compare preoperative and postoperative changes in range of motion, function, and clinical outcome scores. Mann-Whitney U tests and χ2 tests were used to compare the efficacy measures of RSA in cases and controls. Data were analyzed using IBM SPSS version 23 software (IBM Corp, Armonk, NY, USA). For all statistical tests, P < .05 was used to determine significance.

Results Preoperative baseline function and outcome scores were similar among the groups with few exceptions (Table II). The control group demonstrated significantly better active external rotation

ARTICLE IN PRESS Locked anterior shoulder treated with RSA Table II Variable

3

Baseline preoperative comparison of groups Locked anterior shoulder* (N = 24)

Control* (N = 48)

Range of motion (in degrees, unless otherwise noted) Active forward 60 (30-60) 60 (30-75) flexion Active abduction 45 (30-65) 50 (40-70) Active external −10 (−20 to 20) 15 (0-30) rotation Active internal 2 (2-4) 4 (2-8) rotation (points) Preoperative clinical outcome assessments ASES function 8 (0-20) 17 (7-24) ASES total 30 (11-35) 32 (20-48) SST 1 (0-2) 2 (1-4) SANE 20 (3-49) 40 (10-50) VAS pain 7 (6-10) 7 (5-9) VAS function 1 (0-4) 3 (2-5) SF-12 (PCS) 30 (24-35) 33 (28-36) SF-12 (MCS) 48 (37-56) 43 (39-56)

†

P

Table III Preoperative and postoperative comparison of patients treated with RSA for locked anterior shoulder Variable

.289 .215 .006 .039

.024 .112 .015 .135 .674 .024 .102 .908

ASES, American Shoulder and Elbow Surgeons; SST, Simple Shoulder Test; SANE, Single Assessment Numeric Evaluation; VAS, visual analog scale; SF-12, 12-Item Short Form Health Survey; PCS, physical component summary; MCS, mental component summary. * Median (interquartile range). † Wilcoxon signed rank tests were used to calculate P values.

(−10 vs. 15; P = .006) and internal rotation (greater trochanter vs. sacrum/L4 segment; P = .039). The control group also reported significantly better outcome scores: higher SST scores (2 vs. 1; P = .015), higher ASES function scores (17 vs. 8; P = .024), and higher VAS function scores (3 vs. 1; P = .024; Table II). Significant improvements from baseline were seen for both LAS patients and controls (Tables III and IV) for all function, with the exception of internal rotation in both groups, and clinical outcome scores, with the exception of SF-12 scores for LAS patients. Intraoperative management of the glenoid differed between groups. Glenoid bone graft was used more commonly in the control group (26%, 6 patients) than in the LAS group (6%, 3 patients; P = .050). Larger diameter glenospheres were used more commonly in the LAS group, with a predominance of 36-mm glenospheres (P < .001; Table V). Postoperatively, the control group nearly universally demonstrated significantly greater function and better outcome scores (Table VI). This was true for active forward flexion (P < .001), abduction (P = .007), SST (P = .001), VAS function (P = .002), ASES function (P < .001), and ASES total (P = .002) scores. A significantly higher rate of good or excellent patient satisfaction was observed in the control group (LAS, 71%; control, 90%; P = .044). Radiographic findings of scapular notching and shoulder dislocation did not differ significantly between groups (Table VI). However, a greater percentage of patients sustained

Preoperative*

Postoperative* P†

Range of motion (in degrees, unless otherwise noted) Active forward 60 (30-60) 100 (71-120) flexion Active abduction 45 (30-65) 70 (61-90) Active external −10 (−20 to 20) 30 (20-45) rotation Active internal 2 (2-4) 4 (2-8) rotation (points) Assessments ASES function 8 (0-20) 22 (7-31) ASES total 30 (11-35) 55 (41-79) SST 1 (0-2) 6 (1-7) SANE 20 (3-49) 70 (40-90) VAS pain 7 (6-10) 1 (0-5) VAS function 1 (0-4) 7 (3-8) SF-12 (PCS) 30 (24-35) 34 (25-46) SF-12 (MCS) 48 (37-56) 46 (32-57)

.001 .001 .001 .123

.014 <.001 .001 <.001 <.001 .001 .158 .530

RSA, reverse shoulder arthroplasty; ASES, American Shoulder and Elbow Surgeons; SST, Simple Shoulder Test; SANE, Single Assessment Numeric Evaluation; VAS, visual analog scale; SF-12, 12-Item Short Form Health Survey; PCS, physical component summary; MCS, mental component summary. * Median (interquartile range). † Wilcoxon signed rank tests were used to calculate P values.

acromion fractures in the LAS group (21%) than in the control group (8%). Type 3 fractures were significantly more common among patients with LAS compared with patients with classic indications. There were 2 LAS patients who sustained postoperative dislocations that were not seen in the control group. RSA was effective for both the LAS and control groups in treating preoperative morbidity. With the exception of SST score (P = .047) and forward flexion, which improved 30° more for the control group (P = .011), there were no significant differences in the improvements observed (Table VII). There were no revision surgeries required in the control group. Two patients in the LAS group sustained recurrent dislocations. One patient was treated with multiple closed reductions and refused revision surgery. The other patient underwent 2 additional revisions and continued to remain unstable, ultimately refusing further surgery. This patient had a type 3 acromion fracture, which may have contributed to the recurrent instability.22

Discussion The RSA was originally designed for the treatment of rotator cuff tear deficiency in the setting of pseudoparesis. In recent years, indications for RSA have been expanding. These indications now include most revision shoulder arthroplasty; complex proximal humerus fractures in the elderly8,9; rheumatoid arthritis17; fracture sequelae3,40; osteoarthritis with a biconcave glenoid26; and, together with glenoid bone grafting,

ARTICLE IN PRESS 4

J. Kurowicki et al. Table IV Preoperative and postoperative comparison of patients undergoing RSA for classic indications (control) Variable

Preoperative*

Postoperative*

Range of motion (in degrees, unless otherwise noted) Active forward 60 (30-75) 130 (111-139) flexion Active abduction 50 (40-70) 88 (75-105) Active external 15 (0-30) 40 (30-50) rotation Active internal 4 (2-8) 6 (2-8) rotation (points) Clinical outcome assessments ASES function 17 (7-24) 35 (25-45) ASES total 32 (20-48) 81 (66-95) SST 2 (1-4) 8 (6-10) SANE 40 (10-50) 89 (51-98) VAS pain 7 (5-9) 0 (0-1) VAS function 3 (2-5) 9 (6-10) SF-12 (PCS) 33 (28-36) 42 (30-52) SF-12 (MCS) 43 (39-56) 52 (44-60)

P† <.001 <.001 <.001 .059

<.001 <.001 <.001 <.001 <.001 <.001 .009 .012

RSA, reverse shoulder arthroplasty; ASES, American Shoulder and Elbow Surgeons; SST, Simple Shoulder Test; SANE, Single Assessment Numeric Evaluation; VAS, visual analog scale; SF-12, 12-Item Short Form Health Survey; PCS, physical component summary; MCS, mental component summary. * Median (interquartile range). † Wilcoxon signed rank tests were used to calculate P values.

Table V

Intraoperative glenoid management

Variable

Glenosphere diameter (mm) 32 36 Glenoid bone graft

Locked anterior shoulder* (N = 24)

Control* (N = 48)

P†

<.001 6 (25) 18 (75) 3 (6)

34 (71) 14 (29) 6 (26)

.050

* Median (interquartile range). † Wilcoxon signed rank tests were used to calculate P values.

as a means of managing locked anterior dislocations.37 Each of these indications has unique challenges in terms of the patient’s disease, the surgical technique, and ultimately the results. Comparison of baseline and ultimate postoperative outcomes with those of more classic indications helps illustrate differences among these indications and helps define expectations of patients. Results of this retrospective case-controlled study suggest that whereas baseline characteristics of patients are similar between LAS patients and controls (Table II), the postoperative function and outcome scores are inferior for patients with LAS (Table VI). Pain relief for both groups was consistent, as VAS pain scores were low (LAS, 1; control, 0), and satisfaction for both groups was high (LAS, 71%; control, 90%). Remarkably, the effectiveness of RSA in improving motion

Table VI

Postoperative comparison of groups

Variable

Locked anterior Control* shoulder* (N = 48) (N = 24)

P†

Postoperative range of motion (in degrees, unless otherwise noted) Active forward 100 (71-120) 130 (111-139) <.001 flexion Active abduction 70 (61-90) 88 (75-105) .007 Active external 30 (20-45) 40 (30-50) .116 rotation Active internal 4 (2-8) 6 (2-8) .166 rotation (points) Postoperative clinical outcome assessments ASES function 22 (7-31) 35 (25-45) <.001 ASES total 55 (41-79) 81 (66-95) .002 SST 6 (1-7) 8 (6-10) .001 SANE 70 (40-90) 89 (51-98) .079 VAS pain 1 (0-5) 0 (0-1) .025 VAS function 7 (3-8) 9 (6-10) .002 SF-12 (PCS) 34 (25-46) 42 (30-52) .090 SF-12 (MCS) 46 (32-57) 52 (44-60) .098 Good/excellent 17 (71) 43 (90) .044 patient rating of surgical outcome Postoperative radiographs Notching 4 (17) 9 (19) 1.00 Acromion fracture .023 None 19 (79) 44 (92) Type 1 0 (0) 1 (2) Type 2 1 (4) 3 (6) Type 3 4 (17) 0 (0) Dislocation 2 (8) 0 .108 ASES, American Shoulder and Elbow Surgeons; SST, Simple Shoulder Test; SANE, Single Assessment Numeric Evaluation; VAS, visual analog scale; SF-12, 12-Item Short Form Health Survey; PCS, physical component summary; MCS, mental component summary. * Median (interquartile range) or number (%). † Mann-Whitney U test was used to calculate P values for continuous values; χ2 test was used to calculate P values for categorical variables.

and outcomes was equivalent for most measurements, with the exception of SST score and active forward flexion, which saw greater improvement in the control group (Table VII). Reliability of RSA in treating LAS for elderly patients relates to the ability to manage all aspects of disease present. Patients with LAS often have massive rotator cuff tears combined with glenoid bone deficiency, periarticular scarring, periscapular muscle contractures, and variable degrees of arthritic changes and humeral head bone loss.32,37 Of these factors, glenoid bone loss can be the most challenging to manage with RSA as patients with LAS often have significant degrees of anterior glenoid bone deficiency.37 In a series of patients with neglected anterior dislocations treated with RSA and glenoid bone grafting, Werner et al37 described 2 patients with significant glenoid bone loss (66% and 80%) in whom

ARTICLE IN PRESS Locked anterior shoulder treated with RSA Table VII Variable

5

Efficacy of treatment Locked anterior shoulder* (N = 24)

Control* (N = 48)

P†

Preoperative to postoperative change in range of motion (in degrees, unless otherwise noted) Active forward 40 (25-60) 70 (45-85) .011 flexion Active abduction 20 (5-35) 40 (15-60) .061 Active external 30 (9-53) 20 (4-45) .153 rotation Active internal 2 (0-5) 0 (−2 to 4) .625 rotation (points) Preoperative to postoperative change in clinical outcome assessments ASES function 16 (−1 to 25) 20 (10-27) .197 ASES total 42 (14-58) 48 (27-64) .212 SST 5 (1-6) 6 (4-8) .047 SANE 43 (29-63) 50 (27-61) .854 VAS pain −5 (−8 to −1) −5 (−8 to −3) .463 VAS function 5 (2-7) 5 (3-7) .197 SF-12 (PCS) 3 (−4 to 17) 6 (−2 to 14) .883 SF-12 (MCS) −2 (−14 to 7) 7 (−2 to 16) .077 ASES, American Shoulder and Elbow Surgeons; SST, Simple Shoulder Test; SANE, Single Assessment Numeric Evaluation; VAS, visual analog scale; SF-12, 12-Item Short Form Health Survey; PCS, physical component summary; MCS, mental component summary. * Median (interquartile range) or number (%). † Mann-Whitney U test was used to calculate P values for continuous values; χ2 test was used to calculate P values for categorical variables.

early glenoid baseplate failure developed, requiring revision surgery. Glenoid bone loss in anatomic shoulder arthroplasty has demonstrated inferior results.4,5,16,18,30 However, glenoid bone grafting in RSA has yielded more favorable results with minor rates of graft resorption.24,27,37 In a study of 9 patients treated with RSA and augmented with glenoid bone graft, Neyton et al did not find evidence of graft subsidence or glenoid loosening.27 Similarly, Melis et al followed up 29 patients treated with various glenoid bone grafts and demonstrated a partial graft resorption in only 21% of patients.24 Although various glenoid bone grafts may be used, supplementation of glenoid defects with autologous bone graft for cementless baseplate fixation in RSA has been established and shown to be reliable.2,24,27,37 Autologous bone graft from the resected humeral head provides an easily accessible graft source in primary arthroplasty and is thus used commonly during primary RSA. Werner et al37 used autologous humeral head glenoid grafting to manage neglected anterior dislocations with glenoid bone loss and recommended that the glenoid baseplate cover a minimum of 50% native glenoid. This is consistent with the mechanical testing model of glenoid bone loss with the DJO Reverse Shoulder Prosthesis baseplate used in the study reported by Formaini et al, who demonstrated that glenoid baseplate fixation in the setting of glenoid bone

loss is no different when >50% of the baseplate is supported by glenoid bone.10 In our series, all patients in the LAS group had anterior glenoid bone loss as evident on preoperative imaging and intraoperative findings. Despite universal anterior bone loss in the LAS group, only 3 patients (6.3%) required autologous bone graft. This was based on the ability to achieve at least 50% baseplate coverage with native bone after glenoid preparation. In our series, 2 patients in the LAS group sustained recurrent dislocations, both of which remain unstable despite attempts at closed reduction and, in 1 case, subsequent revision arthroplasty. This is despite the use of larger glenospheres, which were more commonly used in the LAS patients than in controls. Larger glenospheres can provide greater joint stability by filling the glenohumeral joint volume, providing improved soft tissue tension. In addition, with larger glenospheres, additional implant-bone contact is provided by backside contact of the periphery of larger glenospheres onto the native glenoid. This has been shown to minimize stress on the glenoid baseplate and to minimize micromotion.28 Interestingly, no baseplate failures were observed in our series, which is in contrast to the 9% baseplate failure rate in a similar series of patients reported by Werner et al.37 The incidence of acromion fractures in this series is higher than what has been previously reported in the literature,4,6,7,11,14,15,20,21,35,38 with 21% of LAS patients and 8% of controls sustaining acromion stress fractures. Type 3 fractures were significantly more common among patients with LAS compared with patients with classic indications (P = .023). No type 3 fractures occurred in the control group. The predominance of type 3 acromion stress fractures in the LAS group warrants further investigation. The additional stress of restoring lateralization of the humerus after medialized contractures may play a role. There are several limitations to this study. First, a single surgeon at a single institution performed all procedures reported in this study using a single implant design. Postoperative results may differ with variation in technique, learning curve, and implant selections. Second, the small sample size of LAS patients may have influenced the ability to detect differences in functional and patient-derived outcome scores between the LAS group and the control group. A larger cohort or multicenter studies would help elucidate differences between these populations of patients.

Conclusion Patients treated with RSA for LAS may expect worse postoperative function and clinical outcomes scores compared with RSA for more classic indications. However, efficacy of treatment was similar between groups. Low pain scores and high patient satisfaction with the RSA procedure were observed in both groups. LAS patients should be counseled about higher rates of postoperative acromion fractures and recurrent dislocations.

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J. Kurowicki et al.

Disclaimer Jonathan C. Levy is a paid consultant for DJO Orthopaedics and receives royalties from DJO Orthopaedics and Innomed. All the other authors, their immediate families, and any research foundation 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.

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