Acromial base fractures after reverse total shoulder arthroplasty: report of five cases

J Shoulder Elbow Surg (2011) 20, 1178-1183

www.elsevier.com/locate/ymse

Acromial base fractures after reverse total shoulder arthroplasty: report of five cases Trevor C. Wahlquist, MS, Allan F. Hunt, MD, Jonathan P. Braman, MD* Department of Orthopaedic Surgery, University of Minnesota, Minneapolis, MN, USA Background: Most series of reverse total shoulder arthroplasty (rTSA) have reported acromial fractures, but they have not been shown to alter reported outcomes in most series. We present 5 patients with acromial base fractures where the entire deltoid origin was displaced from its anatomic location. Materials and methods: Five patients with acromial base fractures after rTSA were identified and evaluated for functional outcomes and pain relief as well as results of fracture treatment. Three were treated operatively and 3 were treated nonoperatively. One nonoperative treatment eventually required open reduction and internal fixation. Results: Function was limited after fracture, with average forward elevation of only 43 but which improved to 84 after fracture union. Pain was significant after the fracture (6.8 of 10) and improved with fracture healing (0.8 of 10). Neer Functional Outcome scores after fracture union averaged 62 of 100, consistent with unsatisfactory results. Conclusion: Acromial base fractures after rTSA are a painful and disabling complication. The outcomes appear different in this series than in other series describing acromial fractures. This may be a result of the different anatomic location of the fractures. Pain improves with fracture union, but functional returns are unpredictable. Level of evidence: Level IV, Case Series, Treatment Study. Ó 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. Keywords: Reverse total shoulder arthroplasty; acromial base fracture

The reverse total shoulder arthroplasty (rTSA) uses the deltoid muscle to compensate for deficient rotator cuff muscles.1 Patients can potentially regain function, strength, and relief of pain, but the procedure also introduces a number of new mechanical stressors. The complexity of this procedure, with regards to its anatomic change as well as the special patient population, is reflected by the large This work was approved by the Investigational Review Board of University of Minnesota and Park Nicollet Institute (No. 03835-09-A) *Reprint requests: Jonathan P. Braman, MD, 2512 S 7th St, Ste R200, Minneapolis, MN 55455 USA. E-mail address: [email protected] (J.P. Braman).

number of reported complications associated with rTSA.5,12,15,19 Primary indications for surgery are painful arthritis associated with rotator cuff deficiency and pseudoparalysis.7,8,11,17-19 Because of the relatively brief history of the rTSA, the management of some complications is poorly understood. Adding to the confusion about this relatively uncommon injury is the lack of consistency of the terminology and the inconsistent description of acromial fracture location in previous reports. We define ‘‘acromial base fracture’’ as a fracture occurring at the connection between the acromial process and the spine of the scapula at the level of the glenoid. These frequently cause the entire the acromial

1058-2746/$ - see front matter Ó 2011 Journal of Shoulder and Elbow Surgery Board of Trustees. doi:10.1016/j.jse.2011.01.029

Acromial base fractures after reverse TSA

Figure 1

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(A) Immediate postoperative and (B) postfracture radiographs show displacement of the acromial base fracture.

process to displace inferiorly (Fig. 1). The fracture is best seen on an axillary lateral view to differentiate it from other locations of acromial fracture or scapular spine fractures (Fig. 2). This location is the foundation of the boney support for the entire deltoid, as it supports all of the acromion process. The goal of this report is to give further insight into one infrequently reported complication we have found associated with this rTSA: acromial base fractures. Although published series have reported acromion fracturing after rTSA, mention of the acromial base is inconsistent. In some reports, these are lumped with os acromiale, and in others, they are included with scapular spine fractures, which is more medial than the glenoid base.14 Acromial base fractures are a problem when they occur in isolation,16 but they present a unique challenge to the rTSA, because the acromion is the origin for the entire deltoid, which becomes the primary stabilizer of the shoulder after rTSA. As a consequence, acromial fractures substantially alter the biomechanics of this deltoiddependant implant.1 Management of this fracture is unclear and variable at this time. One previous article reports reduced outcomes with nonoperative management,6 whereas others discuss operative and nonoperative treatment of ‘‘acromial fractures’’ without further details.4 Finally, deficiencies of the acromion before and after the operation are often discussed together. None of the patients presented here had preoperative acromial deficiency.

Materials and methods Five patients were identified as having acromial base fractures after rTSA from the practices of 2 board-certified orthopedic

surgeons (between 2005 and 2009). A thorough record review was performed on these 5 patients with a focus on function and pain before the operation, after the operation, after the fracture, and after fracture union. Also collected were data on comorbidities and other demographic information pertinent to the history of these patients. These complications occurred during a 6-year period for the 2 surgeons involved in this series. During the study period, surgeon 1 performed 272 TSAs, of which 57 were rTSAs. Surgeon 2 performed 400 TSAs, of which 40 were rTSAs. The rTSA was performed after the patient received an interscalene block, followed by general anesthesia. Patients were placed in the beach chair position for the operation. A standard deltopectoral approach was used, and when able, the previous surgical incision was incorporated. Postoperatively, the patients underwent sling immobilization for 4 to 6 weeks. Activities of daily living were then allowed from week 6 to 12, and physical therapy was begun at week 12, allowing for gentle progressive range of motion (ROM). After identification of the acromial base fracture, patients received 1 of 2 treatments. Three were treated with open reduction and internal fixation (ORIF) of the fracture. The same postoperative protocol was used for patients who required ORIF as they had undergone after rTSA. Patients with acromial base fractures who were treated nonoperatively were placed in an abduction pillow sling (Slingshot, DonJoy Orthopaedics, Vista, CA, USA) for 3 months, with no active or passive ROM, and then were reevaluated. No abduction splints were used. When a bone stimulator was used, the Exogen bone stimulator (Smith & Nephew, Memphis, TN, USA) was used 20 minutes daily according to the manufacturer’s recommendations and was applied to the point of maximal tenderness at the acromial base. Patients were monitored initially at 4- to 6-week intervals. As the patients improved in pain management and function, intervals were extended to 3 and then 6 months for follow-up (range, 1-3 years). The intent of this report is to present 5 patients with acromial base fractures after rTSA (Table I). There are no validated outcomes specifically geared toward this procedure. As

1180

T.C. Wahlquist et al. USA) superiorly and a 2.7 mm 8-hole plate posteriorly. The operation occurred in March 2009, and at follow-up at 12 months, the patient had active flexion to 40 , external rotation to 25 , internal rotation to the gluteus, and abduction to 60 . The Neer Functional Outcomes score was 42 of 100, suggesting an unsatisfactory result.

Patient 2 An 80-year-old right-handed woman presented in July 2006 after a failed left total shoulder. She is a smoker and took NSAIDS and inhaled corticosteroids. Preoperatively, the patient’s active ROM was 30 of forward flexion, 30 of abduction, and passive ROM to 180 and 150 , respectively. Also noted was 60 of passive external rotation and passive internal rotation to the lumbar spine. Simple Shoulder Test score was 1 out of 12. Preoperative pain was noted as 8 of 10. An rTSA on the left shoulder was performed (DePuy Delta, Warsaw, IN, USA). At 7 months, she had 40 of active forward elevation and 30 of external rotation, with 0 of 12 on the Simple Shoulder Test, and pain was rated at 7.5 of 10. Radiographs revealed an acromial base fracture (Fig. 1). She was tender at the posterior aspect of the spine at the base of the acromion. Upon consultation, the patient desired a nonsurgical approach as described above, using a sling and a bone stimulator. Fracture union was noted on a radiograph at 13 months. At 26 months after her rTSA, the patient reported no pain, forward flexion to 95 , external rotation to 0 , and internal rotation to L1. A Neer Functional Outcomes of 66 of 100 suggested an unsatisfactory result.

Patient 3

Figure 2 (A) A postfracture axillary radiograph demonstrates the acromial base fracture. (B) A subsequent radiographic shows evidence of healing. a consequence, Neer’s Functional Outcomes evaluation has been assessed for these patients after recovery from the base fracture10 (Table II).

Case reports Patient 1 A 70-year-old right-handed woman underwent a right rTSA (DePuy Delta, Warsaw, IN, USA) in April 2008 at another center after a failed rotator cuff repair 6 months prior. She does not smoke and regularly takes nonsteroidal anti-inflammatory drugs (NSAIDS) for pain. In February 2009, radiographs demonstrated evidence of an acromial base fracture as well as an intact rTSA, with good fixation. At that time, the patient had 50 of forward elevation and a pain score of 7.5 of 10. Her point of maximum tenderness was on the posterior aspect of the acromial base. Because of the lack of function along with the significant pain, the decision was to proceed with an ORIF of the acromion with dual plating using a 3.5 mm 7-hole plate (Zimmer, Warsaw, IN,

An 83-year-old left-handed woman underwent a left rTSA (TM Reverse, Zimmer, Warsaw, IN, USA) in June 2007 after 2 prior failed open rotator cuff repairs. She does not smoke and takes aspirin for cardiovascular benefit. Preoperatively, patient had an active ROM to 80 of forward elevation, with anterosuperior escape, 70 of abduction, 40 of external rotation, and internal rotation to the hip. Passive ROM was slightly increased from these points. The patient rated function on the Simple Shoulder Test at 0 of 12. The patient reported significant pain (7 of 10) preoperatively. A large superomedial defect was present in her glenoid, and there was cystic bone loss on her humerus that precluded its use as structural bone graft. Consequently, bone grafting using allograft femoral head was performed to the glenoid defect. At 5 months postoperatively, the patient had 45 of forward elevation, good internal and external rotation, and significant improvement of passive ROM. The patient also reported a significant decrease in pain compared with preoperatively. In April 2008, however, she reported a progressive decrease in function and an increase in pain. At this visit, the patient’s ROM was 10 of forward elevation and 30 external rotation. She was maximally tender on the posterior aspect of the shoulder at the acromial base. Radiographs demonstrated an acromial base fracture (Fig. 2) A nonoperative treatment plan, including abduction sling immobilization and bone stimulator, was used as described. Radiographic evidence of bone union was present 13 months after her rTSA, with grade 2 scapular notching13 and no further complications to date. A Neer Functional Outcomes score of 56 of 100 suggested an unsatisfactory result.

Acromial base fractures after reverse TSA Table I

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Patient demographic and outcomes data Patient 1

Patient 2

Patient3

Patient 4

Patient 5

Average

Female 70 Right Right No NSAIDS

Female 84 Left Left No ASA

Female 70 Right Left Yes NSAIDS, inhaled steroids

Female 82 Right Right No None

Male 65 Right Right Yes Malignancy

74.2 -

N/A N/A 8 3

7 7 5 0

8 10 8 0

N/A 8 9 1

N/A N/A 4 0

N/A N/A 50 40 Operative

80 45 10 10 Nonoperative

30 60 40 95 Nonoperative

70 20 N/A 150 Operative

40 90 80 125 Operative

55 79 43 84 -

None

None

Yes Mild scapular notching

Yes Glenoid loosening

ORIF with lag screw and tension band Yes None

Time to union

7.5 wks

11 wks

29 wks

11 wks

ORIF with recon plate and bone grafting Yes Delayed fixation, cellulitis around splint, proximal screw loosening 42 wks

-

Union Complications

ORIF with compression plate Yes None

Gender Age, years Handedness Surgery side Smoker Comorbidities) Pain Pre-op Post-op Postfracture Postunion Forward elevation Pre-op Post-op Postfracture Postunion Fracture treatment method Operative fixation type

7.5 8.3 6.8 0.8

-

20.1 wks

ASA, acetylsalicylic acid; NSAID, nonsteroidal anti-inflammatory drug. ) Includes diabetes, anemia, aspirin use, NSAID use, steroid use, malignancy, or infections.

Table II

Neer Functional Outcomes results

Variable Pain (35) Function (30) Strength Reaching Stability Range of motion (25) Flexion Extension Abduction External rotation Internal rotation Anatomy (10) Total (100)

Patient 1

2

3

4

5

15 8 2 4 2 9 2 1 0 3 3 10 42

35 8 2 4 2 3 0 0 0 3 0 10 56

35 14 4 8 2 7 2 0 1 0 4 10 66

30 22 8 8 6 14 4 1 2 5 2 10 76

35 14 6 4 4 11 4 0 2 3 2 10 70

underwent rTSA without complication (DePuy Delta XTEND, Warsaw, IN, USA). At 3 months, the patient had increasing pain and decreasing function over the previous 2 weeks. She had 30 of abduction and 30 of flexion, with significant pain on both. She was tender at the posterior aspect of the shoulder at the acromial base. The patient’s radiographs demonstrated a change in acromial alignment. A computed tomography (CT) scan was obtained to better characterize the fracture at the acromial base. She was placed in an abduction pillow and began to use a bone stimulator. The acromial fracture failed to heal, and ORIF was performed at 12 months using a lag screw and tension band technique with a Grafton demineralized bone graft (Grafton Eatontown, NJ, USA). At the last follow-up in December 2008, 1 year after the ORIF, she was satisfied with her shoulder. The patient had flexion of 150 and abduction of 140 with limited to no pain. The Neer Functional Outcomes score of 76 of 100 suggested an unsatisfactory result.

Patient 5 Patient 4 An 81-year-old right handed woman presented in August 2007 with a painful massive right rotator cuff tear. She does not smoke. Preoperatively, she had 70 of flexion and 70 of abduction. She

A 65-year-old right-handed man presented after 2 failed open rotator cuff repairs. He is a smoker. Preoperatively, the patient had active flexion to 40 and active abduction to 45 . He underwent rTSA (Tornier, Minneapolis, MN, USA) on his right shoulder, without complication. At 2 months, he had 90 of both flexion and

1182 abduction with limited pain during physical therapy. At the 1-year follow-up, he continued to have poor function and pain, with 80 of flexion and abduction. Tenderness was noted at the base of the acromion posteriorly. Radiographs demonstrated an acromial base fracture. ORIF was performed at 2 years postoperatively. The delay between the diagnosis and treatment of the fracture was because of difficulty the patient had travelling to our center from a distance. No functional treatment was initiated in the interim. Radiographs 2 months after ORIF indicated a downward sloping acromion. Flexion was extremely limited at this time, with only 80 of passive flexion and significant pain over the posterior aspect of the acromion. The patient underwent revision ORIF 4 months later. During surgery, it was noted that the hardware had failed at the scapular spine rather than on the acromion and demonstrated a 3cm gap. His last follow-up, 7 months after revision ORIF, indicated good function and pain control. He had flexion to 125 and abduction to 90 with internal rotation to his belt. External and internal rotation strength was 5 of 5. Final radiographs demonstrated acromial union and good placement of the plates and the reverse total shoulder prosthesis. Neer Functional Outcomes were 77 of 100, suggesting an unsatisfactory result.

Discussion The results of these 5 patients (Table I and II) demonstrate the disabling nature of an acromial base fracture in this setting. Function decreased dramatically after this fracture. Pain scores, surprisingly, did not increase after the fracture, although pain was significant at both the post-rTSA and postfracture visit. This is likely because the fracture in 4 of the 5 patients occurred without any acute trauma. This is consistent with a stress fracture, as previously reported.6 This may explain the continued pain after rTSA in these patients. It is also worth noting that the patients were typically on higher doses of pain medication at this visit then at the postfracture visit. Another potential factor in explaining the decrease in pain after fracture is the decreased activity after the fracture. Before the fracture, the shoulder was still functional and may have been used more frequently than after the fracture, when use was limited, at best. Detection of the fracture was possible in 4 of the 5 patients using plain radiographs, and no CT scanning was necessary for those patients. In the fifth patient, however, the presence of continued posterior shoulder pain and tenderness at the base of the acromion led to a CT scan that demonstrated the acromial base fracture. The Neer Functional Outcome scores demonstrated nearly universally unsatisfactory or failure results, although patient satisfaction was high. This likely represents the difference between initial function and final function. The criteria for successful postoperative results, according to Neer’s article, assume full function and pain level before the injury. Acromial base fractures represent a unique challenge to the rTSA patient, leading to an increased amount of pain

T.C. Wahlquist et al. and severely decreased function. Those patients with fractures of the scapula are at risk of poorer outcomes than those without.6 Acromial base fractures seem to be quite different from acromial spine fractures, and our experience demonstrates that they have worse results in function than the reports about spine fractures would suggest.3,9 Case reports of acromial base fractures secondary to stress have been shown in patients without rTSAs as well. The resulting function of those patients in the literature is also superior to our experience with the patients in this study.15 Individual risk factors for this type of complication remain unclear. Patients with potential predisposing factors, such as preoperative acromial lesions, have not been shown to be at higher risk than those without lesions.14 None of the patients in this series had preoperative evidence of acromial insufficiency. Finally, patients with this fracture who were treated with and without surgery both had inconsistent results. No treatment yielded predictable outcomes in function, but nonoperative and operative treatment plans were effective at reducing pain as the fractures healed. As a consequence, we cannot recommend one treatment type over another for this complication.

Conclusion A acromial base fracture disables the deltoid, and the integrity of the acromion needs to be restored to regain function. There are a number of different ways that union can be attained, with some improvement in pain and disability. These 5 patients demonstrated pain relief using both surgical and nonsurgical techniques. After radiographic union, pain scores decreased, but function remained substantially limited compared with the published results for uncomplicated rTSA.2,8 No solidified protocol currently exists for the management of acromial base fractures after rTSAs. Along with this, few acromial base fractures have been mentioned in the literature and have inconsistently been described in terms of outcomes of varying management strategies. Our sample size is too small to draw conclusions about advantages of operative and nonoperative treatment for this injury. It would be beneficial for a larger series to more carefully describe the anatomic location of the acromial fractures, because fractures at the base seem to have a more significant effect on pain and function that other acromial fractures reported in the literature. We advocate a thorough radiographic evaluation of any patient with increased pain after rTSA, especially if the symptoms localize with the physical examination to the posterior aspect of the acromial base. Increased awareness and insight into the mechanics of base fractures is needed. and management options need to be improved.

Acromial base fractures after reverse TSA

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