Subscapularis-sparing TSA, deltopectoral approach yield reliable radiographic results
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Traditional total shoulder arthroplasty via a deltopectoral approach has demonstrated reliable and durable clinical outcomes. However, a rate-limiting step in return to function is the time to healing of the subscapularis.
The rate of dysfunction or failure of the subscapularis tendon requiring revision surgery has been shown to be 5.8%. Up to 67% of patients have abnormal exam findings related to the subscapularis after total shoulder arthroplasty (TSA). Jeffrey D. Jackson, MD, and colleagues evaluated 15 patients with ultrasound after traditional TSA using tenotomy and repair. They showed that 46% of patients had a complete tear of their subscapularis repair at 6-month follow-up.
Given the relatively high rate of subscapularis complications in traditional shoulder arthroplasty, surgeons have developed alternative techniques to address this problem. Many of these techniques center on approaches to maintain the integrity of the subscapularis. Laurent LaFosse, MD, and colleagues developed a technique utilizing a superolateral approach and it accesses the glenohumeral joint through the rotator interval without disruption of the subscapularis. This technique demonstrated promising results, however, the approach requires elevation of the deltoid origin and open acromioplasty. It was also found to have left many residual humeral osteophytes. David P. Adkison, MD, and colleagues continued to adapt this technique to improve the difficulty with making an anatomic neck cut, removing inferior osteophytes and sizing the humeral head. They recently published on 70 patients treated with subscapularis-sparing TSA in which they found similar radiographic results compared with traditional TSA. Felix H. Savioe, MD, and colleagues performed an alternative method of the subscapularis-sparing approach through the deltopectoral interval. This technique requires tenotomy of the inferior half of the subscapularis with later repair to assist in removal of inferior osteophytes and humeral head exposure. They showed encouraging results with no complications regarding the subscapularis, however, the published results were only in cases of hemiarthroplasty. This approach does not lend itself to being able to access the glenoid.
The goal of the current technique is to combine the benefits of the deltopectoral approach in assisting with inferior osteophyte resection and humeral head sizing with the benefit of maintaining the integrity of the subscapularis tendon. This pilot study introduces a technique to expose the glenohumeral joint through a deltopectoral approach and the rotator interval, and does not require takedown of the subscapularis tendon. When necessary, an inferior access window is created to allow for removal of inferior osteophytes without tenotomy of the inferior half of the subscapularis.
Methods
Between December 2019 and February 2020, Mark A. Mighell, MD, senior author of this article, performed anatomic TSA through a deltopectoral approach and rotator interval without tenotomy of the subscapularis in 10 consecutive patients. All patients were indicated for surgery for primary glenohumeral osteoarthritis.
Consistent with the methods used by Joseph P. Iannotti, MD, and colleagues, a postoperative true anteroposterior (AP) radiograph (Grashey view) with the entire humeral prosthesis in near-perfect profile, defined by limited or less than 2-mm overlap of the metallic humeral head at the level of the osteotomy surface, was selected for analysis. The greater tuberosity and medial calcar were also in profile with minimal overlap of the prosthesis and lateral or medial bone.
Again, consistent with methods used by Iannotti, a best-fit circle was placed on a true AP image using three preserved bony landmarks. A second circle was placed to fit the curvature of the prosthetic humeral head. The center of rotation (COR) was then identified from each circle and the distance, in millimeters, between the COR of the anatomic and implant circles was calculated. Radiographs were evaluated for the presence of residual inferior humeral or glenoid osteophytes. Complications were collected during the early follow-up period. These included infection, wound dehiscence, delayed wound healing and the need for revision surgery.
Source: Mark A. Mighell, MD
Technique
The patient is positioned in a beach chair position and undergoes general anesthesia, as well as an inter-scalene regional block. The arm is supported on a padded Mayo stand. A standard deltopectoral incision is used starting in line with the deltopectoral interval, 5 cm medial to the acromioclavicular joint down towards the deltoid insertion on the humerus, 10 cm in length. Full-thickness skin flaps are elevated, the cephalic vein is taken medial and the deltopectoral interval is exposed. The superior 5 mm of the pectoralis major tendon is released and a biceps tenodesis to the pectoralis tendon is performed. When necessary, the upper border of the latissimus dorsi and teres major are released to expose an inferior window to access the inferior humeral osteophytes. A curved 0.5-inch osteotome is used to make a unicortical osteotomy of the inferior osteophytes. The osteophytes are later removed once the humeral head cut has been completed.
The biceps groove is used to guide the exposure to the rotator interval with release to the base of the coracoid followed by excision of the remaining proximal biceps tendon. The rotator interval is further exposed by excision of the remaining interval tissue to the base of the coracoid (Figure 1). A Hohmann retractor is then placed anteriorly within the glenohumeral joint with the tip on the anterior and inferior articular surface of the humeral head. This allows retraction of the subscapularis tendon. A second Hohmann retractor is placed in the joint with the tip just under the posterior and inferior articular surface of the humeral head. A third small sharp Hohmann retractor may be placed, if necessary, into the bare area of the rotator cuff to aid in retraction of the supraspinatus and infraspinatus. Adduction and extension of the humerus is helpful to aid in exposure.
A burr or rongeur is used on the superior surface of the humeral head just posterior to the biceps groove to allow easy entry of the canal finder. After the canal finder has established the intramedullary path, intramedullary reamers are used to ream up to a scratch fit of the diaphysis. A custom humeral head cutting guide with a 135° neck shaft angle is pinned into place using the forearm as a guide to set retroversion at 30°. The supraspinatus and subscapularis tendon insertions are used for placement of the laterally based cutting guide (Figure 2). In some patients, a small release of the anterior border of the supraspinatus may be necessary for the cutting guide to fit appropriately. The intramedullary reamer is removed. A precision saw is used to cut the humeral head. The saw is used to cut from lateral to medial leaving the medial cortex intact to avoid iatrogenic injury to the glenoid articular surface. An osteotome is used to finish the cut of the medial cortical bone in a controlled fashion. After the head cut is complete, the inferior osteophytes are removed using a combination of osteotomes, rongeurs and pituitaries while using access through both the inferior window and rotator interval. The humerus is then broached with the final broach being left in place to protect the humerus during glenoid exposure and preparation.
Humeral retractors are removed and attention is turned to the glenoid. The arm is supported on the padded Mayo stand. A Bankart retractor is placed posteriorly at the 7 o’clock position (in a right shoulder). The humerus is retracted inferiorly. The arm is maintained in the adducted position during glenoid preparation. The labrum is excised and a 360° release of the capsule is performed. A second Bankart retractor is placed anteriorly and the anterior capsule is sequentially released along the neck of the glenoid. A small Hohmann retractor is then placed at the coracoid base for improved exposure of the glenoid (Figure 3). At this time, any remaining cartilage is removed using a Cobb elevator. The glenoid is sized and a central pin is placed. The glenoid is reamed using cannulated reamers. A central hole is drilled and the pin is removed (Figure 4). Manufacturer guidelines are followed for preparation of a self-pressurizing keeled component. A keeled component has been found to facilitate bony preparation and actual placement of the implant with this particular technique when compared with a pegged component. A trial component is then placed to assess seating and sizing of the glenoid component. Cement mixed with methylene blue is placed. The final prosthesis is impacted.
All retractors are removed from the glenoid and the previously used humeral retractors are replaced. A limitation of this technique is the difficulty in placing a humeral head component to trial. Preoperative planning is used to predict the correct humeral head implant size. Calculations for estimation of the humeral head are done using the dimensions of the native humeral head as described by Iannotti. Utilizing these data, we estimate the humeral head implant to be between 0.75 and 0.85 of the diameter of native humeral head [Example calculation: (Native humeral head diameter/2) X 0.75-0.85]. In addition, the removed native humeral head is used to confirm the sizing choice (Figure 5).
The broach is removed and the humerus is exposed using assistance from double-pronged Gelpi retractors on the anterior and posterior rotator cuff. The implant stem is impacted into place. The stem is left 3 mm proud to allow for seating of the Morse taper of the humeral head (Figure 6). The humeral head is impacted into place and the stem is seated the rest of the way. Retractors are removed and the shoulder is evaluated for overall soft tissue balance of the glenohumeral joint with posterior pushback and 50% with recoil.
If a release of the anterior portion of the supraspinatus or the superior portion of the subscapularis is necessary, these are repaired using #2 FiberWire suture (Arthrex) in a transosseous fashion. After this repair, the rotator interval is closed using the lateral most portions of the subscapularis and supraspinatus.
Postoperative rehabilitation
After surgery, the patient is placed in a sling until the regional block wears off, after which the sling is worn for comfort only. The patient starts with gentle shoulder pendulums for range of motion and progresses motion and activity as pain allows. Formal physical therapy begins at 6 weeks to maintain continuity of care with therapists at our center until new protocols are in place. We ask patients to limit heavy weight-bearing for 3 months. Doing this allows for bony ingrowth of the humeral stem.
Results, conclusion
Nine of 10 patients underwent anatomic TSA with sparing of the subscapularis tendon as described. One patient with a B2 glenoid required conversion to standard lesser tuberosity osteotomy due to difficult exposure of the glenoid. There were no complications reported in any patients in the intraoperative or early postoperative period. The humeral component COR averaged 2.5 mm from the COR of best fit. Incomplete humeral osteophyte removal was noted in four patients, although the bulk of the osteophytes were removed in those cases.
Failure or dysfunction of the subscapularis tendon after takedown and repair in TSA continues to be a common problem. It is the goal of subscapularis-sparing techniques to limit problems associated with the subscapularis in the correctly selected patient and allow an expedited recovery with minimal time in immobilization. We recommend using the subscapularis-sparing technique in patients with an A1, A2, B0 or B1 Walch classification. In patients with greater glenoid deformity, such as a B2 glenoid, the exposure is difficult and a traditional approach may be more appropriate for these patients. In patients whose deformity is too great for glenoid exposure, use of a deltopectoral approach allows for easy conversion to a traditional TSA approach with a lesser tuberosity osteotomy, tenotomy or subscapularis peel. The ease of surgery continues to improve with each case as experience increases. Further studies are needed to confirm the efficacy and reproducibility of these encouraging early results. Subscapularis-sparing TSA using a deltopectoral approach and the rotator interval without subscapularis tenotomy for glenohumeral exposure produces reliable radiographic results with no major complications in the early clinical follow-up period.
For more information:
Andrew M. Lee, MD, is a shoulder and elbow surgery fellow; Mark A. Mighell, MD, is a shoulder and elbow surgeon; and Ryan A. Neeley, DO, is a shoulder and elbow surgery fellow at Florida Orthopedic Institute. They can be reached at 13020 N. Telecom Parkway, Temple Terrace, FL 33637. Lee’s email: andrewmlee2@gmail.com. Mighell’s email: mmighell@floridaortho.com. Neeley’s email: rneeley@floridaortho.com.
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