Seven-step subscapularis-sparing, windowed anterior technique used for anatomic TSA
The subscapularis-sparing, windowed anterior technique for total shoulder arthroplasty preserves the subscapularis muscle, which allows patients to confidently rehabilitate early and without sling restrictions.
Patients who meet the indications for anatomic total shoulder arthroplasty can be considered for this procedure. Patients with inflammatory or cystic arthritis, dysplastic glenoids, and patients with significant glenoid deformity were excluded.
An inferior window, which is a key aspect of the procedure, creates releases necessary for full glenoid exposure.
This technique avoids the release of the subscapularis thereby mitigating the risk of subscapularis failure. We have also found that this technique substantially improves the soft tissue balancing of the shoulder. We use a standard deltopectoral approach which offers the surgeon the options if the glenoid cannot be exposed with the subscapularis intact.
To date, we have performed this technique in 77 patients without any revisions in the early postoperative period (0 to 18 months). We found it necessary to either osteotomize the lesser tuberosity or convert the patient to reverse shoulder arthroplasty in approximately 5% of patients. The senior author’s preference is to perform RSA when significant cystic changes are present in the glenoid (Figures 1-4).
The patient is positioned in a beach chair position under general anesthesia with an interscalene regional block. A standard deltopectoral incision with the patient’s arm abducted on a Mayo stand in neutral rotation is used starting in line with the deltopectoral interval from 5 cm medial to the acromioclavicular (AC) joint to the deltoid insertion (Figure 5).
1. Superior window, anterior superior quadrant exposure
For superior window (rotator interval) and anterior superior (AS) quadrant exposure, the arm is in 30° of abduction and forward flexion. The biceps tendon is identified. The upper 10% of the pectoralis major tendon is released to allow for access to the inferior humeral osteophyte. The biceps tendon is released and tagged for later tenodesis to the pectoralis major tendon. The remainder of the biceps tendon is followed proximally and released from the supraglenoid tubercle. The rotator interval tissue is delineated and excised, releasing along the superior border of the subscapularis tendon to the base of the coracoid. This enables release of the coracohumeral ligament and a small portion of the coracoacromial ligament. A Hohmann retractor is placed above the glenoid and posterior to the coracoid. The capsule is then released anteriorly from the base of the coracoid down to the equator of the glenoid. We have coined this as the AS quadrant release (Figure 6). An anterior glenoid retractor is placed around the anterior glenoid neck and any residual labral tissue is excised.
- The biceps anchor and base of the coracoid are good landmarks for tissue that is safe to remove in the rotator interval.
- Release of the superior window generates the mobility necessary for proper exposure and releases in the inferior window.
2. Inferior window exposure, osteophyte removal
To start the inferior window exposure and osteophyte removal, the patient’s arm is in flexion, adduction and progressively externally rotated.
The inferior window is created just below the inferior border of the subscapularis starting at the medial border of the bicipital groove. The upper borders of the latissimus dorsi and the inferior capsule are released. It is critical to stay on bone (ie, periosteal release) when performing this step. The assistant should point the patient’s elbow at the surgeon’s navel (flexion) and progressively externally rotate as the release is performed. A Hohmann retractor is placed on bone through this window and retracted inferiorly and medially. Hohmann retractors are “walked” around the inferior neck as the capsule is released with increasing external rotation, flexion and adduction (The arm should be kept tucked in.). This step allows for removal of the inferior osteophyte and, most importantly, allows the humeral shaft to be translated inferiorly. This is critical for glenoid exposure (Figure 7).
A Hohmann retractor is positioned to protect the subscapularis as a curved 0.5-inch osteotome is used to remove the inferior/posterior head and osteophyte. The osteotome is levered to break it free from the far cortex (Figure 8). This step requires caution to protect the axillary nerve, which is achieved by placing the osteotome directly on bone and favoring a lateral upward trajectory toward the eventual head cut. The osteotomized fragment is removed in part or in full. In some cases, fragments are accessed through the rotator interval after the glenoid is exposed (Figure 9).
- The osteotomy is intentionally made more lateral and superior into the humeral head to allow for removal of the osteophyte and bone which would otherwise be taken during the head cut. This avoids injury to the axillary nerve/circumflex vessels.
- The inferior window is developed even in the absence of an inferior osteophyte to release the humeral capsular attachments. This allows for increased inferior translation of the humerus which is critical for glenoid exposure.
3. Humeral head cut
The humeral head cut is performed with the arm in adduction and extension.
Two narrow, sharp Hohmann retractors are used to expose the humeral head through the rotator interval. One is placed posteriorly and into the bone just medial to the insertion of the rotator cuff. Similarly, another Hohmann retractor is placed anteriorly and impacted into the bone for retraction of the subscapularis. It is essential for the assistant to remain diligent in holding the patient’s arm adducted and extended to properly expose the humeral head and allow for canal preparation. A burr is used to gain entry and 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° (Figure 10). In many patients, a small release of the anterior border of the supraspinatus or upper border of the subscapularis may be necessary. The intramedullary reamer is removed. A blunt Hohmann retractor is placed medially to protect the glenoid. A specialized saw, that oscillates only at the tip of the saw, is used to cut the humeral head up to the medial cortex. A 1-inch osteotome is used to finish the cut in a controlled fashion. The head is removed with any residual osteophyte (Figure 11).
- The cut segment is used to help estimate the size of the head. Preoperative 3D software planning is performed on all cases. Generally, a 52 mm x 17 mm head works in most males and a 40 mm x 14 mm head works in most females. The final implant choice, however, is determined intraoperatively. The humerus is broached and the final broach is left in place to protect the humerus during glenoid exposure and preparation.
- The saw should cut through all but the medial cortex of the humeral head and a large osteotome should be used to finish the cut. This avoids injury to the face of the glenoid with the saw.
- After the humeral head cut is completed, check for any posterior and inferior humeral osteophytes that may have not been accessible through the inferior window prior to when the head cut was made.
4. Glenoid exposure
Glenoid exposure is done with the arm in abduction and slight internal rotation. The anterior glenoid exposure is completed by releasing the anterior capsule off the anterior neck of the glenoid. Once this is completed, the posterior labrum and capsule are also released thereby allowing the humeral head to translate inferiorly. The surgeon uses the small glenoid neck retractor to assist in performing the releases. The humerus is translated inferiorly as the releases are performed. Following the 360° release of the capsule from the glenoid, a small Hohmann retractor is placed superiorly and two glenoid neck retractors are placed on either side of the inferior glenoid, the first is seated posterior-inferiorly and the second anterior-inferiorly with traction force on these retractors directed predominantly inferiorly.
- Alteration of retractor placement combined with strategic releases allows for optimal tensioning and detensioning, which helps gain adequate exposure.
- The 360° release is an essential component of the procedure that allows for inferior translation of the humerus.
- If inferior translation of the humerus is met with resistance, consider going back to the inferior window exposure step to ensure complete release of the inferior humeral capsular attachments.
5. Glenoid component implantation
For glenoid component implantation, the arm is abducted with slight internal rotation. The glenoid is sized and a central pin is placed in it. The glenoid is reamed using cannulated reamers. A central hole is drilled and the pin is removed. Manufacturer guidelines are then followed for preparation of a self-pressurizing keeled component, which the senior author has found easier to use for this technique. The trial component is used to confirm seating and sizing of the glenoid component (Figure 12). Cement mixed with methylene blue is placed and the final prosthesis is impacted.
Both pegged and keeled components can be used with this technique. In patients who have limited glenoid exposure, keeled glenoid components have been easier to place than pegged glenoid components.
6. Humeral component implantation
The humeral component implantation is performed with the arm in adduction, extension and slight external rotation.
The arm is adducted and extended using the small sharp Hohmann retractors to expose the humerus. The broach is removed. The humeral implant is prepared on the back table to be implanted as a monolithic component. Heavy sutures are then placed in the medial aspect of both the supraspinatus and subscapularis tendons (Figure 13). The sutures are used like a purse string to retract the tendons away as the implant is seated. A freer elevator is used to prevent entrapment of the subscapularis and supraspinatus tendons from beneath the humeral head. The humeral component is then fully seated. Retractors are removed and the shoulder is evaluated for overall soft tissue balance. The shoulder remains balanced with this technique through preservation of the soft tissue restraints and recreation of the bony anatomy with properly sized implants. It can be difficult to place the humeral head over the taper of the stem due to soft tissue tension; therefore, we recommend early assembly and monolithic insertion of the humeral component.
- Use of the largest stem that fully engages the diaphysis helps to avoid coronal plane alignment. If the head cut is suboptimal, the trial broach positioning will allow this to be identified and corrected. With a stemless implant, a suboptimal head cut will lead to malpositioning. It is also difficult to seat a stemless implant through this exposure. For these reasons, using a stemmed implant is necessary when performing this technique.
- Use heavy sutures and a freer to retract the rotator cuff during final seating of the assembled monolithic implant.
7. Rotator interval closure
Rotator interval closure is done with the arm in abduction and internal rotation (Figure 14.)
The anterior border of the supraspinatus and the superior border of the subscapularis are brought together using a #5 nonabsorbable braided suture to close the rotator interval. If a release of the anterior portion of the supraspinatus or the superior portion of the subscapularis was done, these are repaired using #2 nonabsorbable polyethylene core sutures in a transosseous fashion. An additional #2 suture is used to close-down the remaining lateral portion of the rotator interval and tenodese the biceps to the upper border of the pec major. This marks the completion of the procedure (Video) with standard skin closure to follow.
- For more information:
- George Haidamous, MD, a shoulder and elbow fellow, and Mark A. Mighell, MD, can be reached at Florida Orthopedic Institute, Foundation for Orthopaedic Research & Education, 13020 Telecom Parkway N., Tampa, FL 33637. Haidamous’s email: firstname.lastname@example.org. Mighell’s email: email@example.com.
- John P. Ross, MD, can be reached at Northwest Orthopedic Surgery, 3030 Salt Creek Lane, Suite 100, Arlington Heights, IL 60005; email: firstname.lastname@example.org.