Monday, October 7, 2019

Subacromial balloon spacer- do we understand the mechanics?

The effect of the subacromial balloon spacer on humeral head translation in the treatment of massive, irreparable rotator cuff tears: a biomechanical assessment

These authors evaluated the ability of a subacromial balloon spacer to depress the humeral head in a cadaveric model of a massive, irreparable rotator cuff tear.

They noted that after the creation of a massive rotator cuff tear involving the supraspinatus and infraspinatus, the humeral head translated superiorly by an average of 3.5 mm when the deltoid was loaded to 80N. 

When the balloon was inflated to 10 mL, the normal humeral head position was not restored; when the balloon was inflated to 40 mL the it overtranslated the humeral head anteroinferiorly. When the balloon was inflated to 25 mL, the humeral head position was similar to that of before the creation of the cuff tear. 

Comment: This study found that a massive cuff tear resulted in less than 4 mm of superior translation of the humeral head. Clinical experience indicates that deltoid strengthening alone can usually compensate for this small amount of superior displacement.  This study did not demonstrate that the deltoid was more efficient after the placement of the balloon. 

This study points out that the ability of the balloon to depress the humeral head is critically dependent on the volume of fluid it contains at time zero. However, it does not present data on how long the balloon remains inflated to the desired volume. 

The role of this device in the management of irreparable cuff tears remains undefined.

Here is another recent post on the topic:

Biomechanics of Biodegradable Subacromial Balloon Spacer for Irreparable Superior Rotator Cuff Tears Study of a Cadaveric Model 

These authors used a cadaveric model to test the initial in vitro function of a subacromial balloon spacer ((InSpace; OrthoSpace)* in a simulated neutral arm position (balanced) and in active shoulder abduction (unbalanced).

They found that when the balloon was inflated with saline over the irreparable supraspinatus tear in the balanced condition, glenohumeral contact pressure increased by 122% (p = 0.006) compared with that for the irreparable tear at 0 of abduction and by 94% (p = 0.046) at 60. In the unbalanced condition, pressure decreased in the irreparable tear condition after the balloon was inflated, restoring pressure to close to that in the intact state. The balloon did not restore glenohumeral contact area to that in the intact shoulder in either the balanced or the unbalanced condition. The irreparable tear displaced the humeral head superiorly in the unbalanced condition, decreasing the acromion-humeral interval. On inflation the balloon moved the head inferiorly by 6.2 ± 1.3 mm (p < 0.001) at 0 of abduction, 4.4 ± 1.3 mm (p < 0.001) at 30, and 3.0 ± 0.8 mm (p < 0.001) at 60. The balloon increased the deltoid load after an irreparable tear by 8.2% (p = 0.022) at 0, 12.6% (p = 0.002) at 30, and 11.1% (p = 0.008) at 60. 

The authors point out that small, mostly uncontrolled clinical studies have shown that the balloon is associated with improved pain and functional scores with minimal intraoperative or postoperative complications. Unsatisfactory outcomes were reported in 1 small prospective case series with 2-year follow-up . The study with the highest level of evidence showed good results, but it could not establish whether they were a direct effect of the balloon or of additional interventions. Complications have included conversion to reverse shoulder arthroplasty and revision because of balloon migration. It has been estimated that the balloon remains inflated for up to 12 months. One magnetic resonance imaging study showed that the balloon was progressively compressed and surrounded by an inflammatory stratus from 6 to 12 months after implantation, and it degraded into a thick layer of fibrosis by 24 months.

*Kalamazoo, Michigan, March 14, 2019 (GLOBE NEWSWIRE) -- "Stryker (NYSE:SYK) announced on 3/14/2019 it has completed the acquisition of OrthoSpace, Ltd., a privately held company founded in 2009 and headquartered in Caesarea, Israel, in an all cash transaction for an upfront payment of $110 million and future milestone payments of up to an additional $110 million. OrthoSpace’s product portfolio provides a highly differentiated technology for the treatment of massive irreparable rotator cuff tears. The InSpace product is a biodegradable sub-acromial spacer, which is designed to realign the natural biomechanics of the shoulder. The technology has a long clinical history with over 20,000 patients treated across 30 countries. In the U.S., InSpace is currently under clinical study and not approved for use."

Comment: The management of irreparable rotator cuff tears needs to be based on the patient's clinical findings. The range of successful treatments extends from gentle stretching and strengthening exercises to a reverse total shoulder. 

We find that for patients with symptomatic irreparable tears with retained active elevation and without arthritis, a simple "smooth and move" procedure can restore comfort, range of motion and function, as demonstrated below. On the other hand, for those with pseudo paralysis, we find that a reverse total shoulder is the most reliable procedure. We have not yet found a place in our practice for superior capsular reconstruction or subacromial ballon catheters. 

Significant improvement in patient self-assessed comfort and function as early as six weeks after the smooth and move procedure for shoulders with irreparable rotator cuff tears and retained active elevation

These authors point out that it has been previously  documented that the smooth and move procedure—smoothing the proximal humeral surface while maintaining the coracoacromial arch—can provide clinically significant long-term improvement in function for patients having irreparable rotator cuff tears with retained active elevation (see previous blog post that is reproduced below).

In this study they sought to demonstrate that clinically significant gains in comfort, function, and active motion can be realized as early as 6 weeks after this procedure. They conducted a prospective cohort study of the 6-week clinical outcomes for 48 patients enrolled prior to a smooth and move procedure for irreparable rotator cuff tears. Prior rotator cuff repair had been attempted in 28 (70%).

In 40 patients with preoperative and 6-week postoperative measurements, the Simple Shoulder Test scores improved from an average of 3.4 ± 2.8 preoperatively to 5.7 ± 3.5 at 6 weeks (p < 0.001), an improvement that exceeded the published values for the minimal clinically important difference (MCID).

The clinical outcomes were not worse for the 18 shoulders with irreparable tears of both the supraspinatus and infraspinatus.

In 30 patients with preoperative and 6-week postoperative objective measurements of active motion, the average abduction improved from 93(± 43) to 123(± 47)° (p = 0.005) and the average flexion improved from 102(± 46) to 126(± 44)° (p = 0.023).

They concluded that in addition to its previously documented long-term effectiveness for shoulders with irreparable rotator cuff tears and retained active elevation, this study demonstrates that the smooth and move procedure provides clinically significant improvement as early as 6 weeks after surgery.

They present the case example of a 71 year old physician photographer with a failed prior cuff repair attempt. Here is the preoperative radiograph
At surgery he had no supraspinatus or infraspinatus. The debris shown below was removed from his humeroscapular motion interface

This video (used with permission of the patient) shows his function 6 weeks after surgery.

Eight weeks after surgery he was photographing north of the Arctic Circle. Here's one of his photos.

This study should be considered along with a prior study, which is discussed below.

Treatment of irreparable cuff tears with smoothing of the humeroscapular motion interface without acromioplasty

These authors sought to determine whether shoulders with irreparable rotator cuff tears and retained active elevation (>100 degrees) can be durably improved using a conservative surgical procedure that smoothes the interface between the proximal humeral convexity and the concave undersurface of the coracoacromial arch followed by immediate range of motion exercises.

The typical pathology in these cases is shown in the figure below.

The surgical approach is through a deltoid splitting incision that preserves the deltoid origin, the acromion and the coracoacromial ligament.

The coracoacromial arch is preserved to avoid the complication of anterosuperior escape that is commonly encountered when acromioplasty is performed in the presence of a large cuff tear.

The surgery includes smoothing of the prominence of the greater tuberosity that is exposed in cuff tears along with resection of adhesions in the humeroscapular motion interface and a gentle manipulation under anesthesia to resolve the stiffness that is commonly associated with chronic cuff tears. Immediate active assisted and active motion are encouraged immediately after surgery. Because no repair or reconstruction has been performed, activities, including deltoid strengthening can be resumed as soon as they are comfortable. 

They reviewed 151 patients with a mean age of 63.4 (range 40–90) years at a mean of 7.3 (range 2–19) years after this surgery. The patient data are shown below, contrasting the patients that did and did not improve by the MCID of 2 in the Simple Shoulder Test

In 77 shoulders with previously unrepaired irreparable tears, Simple Shoulder Test (SST) scores improved from an average of 4.6 (range 0–12) to 8.5 (range 1–12) (p < 0.001). Fifty-four patients (70%) improved by at least the minimally clinically important difference (MCID) of 2 SST points. 

For 74 shoulders with irreparable failed prior repairs, SST scores improved from 4.0 (range 0–11) to 7.5 (range 0–12) (p < 0.001). Fifty-four patients (73%) improved by the MCID of 2 SST points.

They provided this case example. A rancher in his mid 60s had a right rotator cuff reconstruction with freeze-dried acellular human dermal collagen tissue matrix that subsequently became infected. He presented to us with a painful stiff right shoulder. At surgery there was extensive scar throughout the humeral scapular motion interface. The subscapularis was detached but was reconstructible. The supraspinatus was absent. The upper 2/3 of the infraspinatus was absent as well. The tuberosities were prominent. He had a smooth and move procedure at which time the abundant scar in the humeral scapular motion interface was debrided. The previous sutures and Graft Jacket were excised. The bursa was removed. The prominent tuberosities were resected using a rongeur and a burr. A manipulation under anesthesia was performed to assure a full passive range of motion. Passive and active range of motion exercises were started immediately after surgery. Three years later he reported excellent shoulder comfort and function and sent us this photo of his return to one of his favorite activities

They concluded that smoothing of the humeroscapular interface can durably improve symptomatic shoulders with irreparable cuff tears and retained active elevation > 100 degrees. They point out that this conservative procedure offers an alternative to more complex procedures in the management of irreparable rotator cuff tears.
Here's a youtube describing the smooth and move in a bit more detail


We have a new set of shoulder youtubes about the shoulder, check them out at this link.

Be sure to visit "Ream and Run - the state of the art"  regarding this radically conservative approach to shoulder arthritis at this link and this link

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