57 Surgical Technique for Converting a Failed Total Shoulder Arthroplasty to Reverse Shoulder Arthroplasty

10.1055/b-0039-167706

57 Surgical Technique for Converting a Failed Total Shoulder Arthroplasty to Reverse Shoulder Arthroplasty

Derek Cuff

Abstract

Complications after anatomic total shoulder arthroplasty can lead to failure of this procedure resulting in poor function and pain for the patient. Reverse shoulder arthroplasty has become a reliable salvage operation to treat a failed anatomic total shoulder operation. In this chapter, we discuss the preoperative considerations, surgical exposure, techniques for implant removal, techniques for reconstruction, and the postoperative care associated with this operation. Understanding these techniques and potential surgical pitfalls can allow for successful conversion of a failed anatomical total shoulder arthroplasty to a reverse shoulder arthroplasty in an effort to improve the patient’s function and surgical outcome.

57.1 Goals of Procedure

The indications for reverse shoulder arthroplasty (RSA) have expanded significantly since its introduction as a treatment for advanced cuff-tear arthropathy. One of those expanded indications is the use of RSA as a salvage treatment for a failed anatomic total shoulder arthroplasty (TSA). ¹ The goal of this procedure is to revise a failed TSA to an RSA in an effort to provide implant stability, decreased pain, and improved function for the patient and will be described in detail in this chapter.

57.2 Indications/Contraindications

There are both early- and late-failure mechanisms that can occur after anatomic TSA, necessitating the need for revision to RSA. Early failures may occur due to complications related to the rotator cuff and the subscapularis repair that is routinely done at the completion of the index TSA. Failure of the repair can lead to subscapularis insufficiency, which results in anterior instability with recurrent subluxations or dislocations of the implant markedly affecting the patient’s function in the months or early years following surgery. Instability secondary to a failed TSA in an anterior or posterior direction is an indication for revision to RSA to provide stability and improved function.

A more delayed failure mechanism requiring revision of TSA to RSA can occur in a subset of patients who develop large degenerative rotator cuff tears as they age, eventually leading to poor function and failure of their index arthroplasty after many years ( Fig. 57.1 ). Loosening of the glenoid component is another delayed failure mechanism that can occur after anatomic TSA necessitating revision to RSA. Failure of the glenoid–cement or bone–cement interface over time can lead to loosening of the glenoid component, affecting the patient’s function and level of pain. In these cases, there may be bone loss on the glenoid side making it difficult to place a new polyethylene glenoid component. RSA offers strong and more reliable glenoid fixation in these glenoid bone loss cases and is a good indication for this difficult problem.

**Fig. 57.1** A total shoulder arthroplasty 8 years out from the index procedure. This implant was implanted slightly proud, which most likely led to progressive cuff failure and proximal migration of the humeral component.

RSA requires an intact and firing deltoid muscle to power the implant. A contraindication to revising a TSA to an RSA would include some type of axillary nerve injury that occurred at the index TSA resulting in permanent nerve injury. Careful assessment of the neurologic status of the operative arm with respect to the axillary nerve and deltoid function should be evaluated on physical examination prior to indicating a patient for revision of the TSA to RSA.

57.3 Preoperative Preparation

Prior to performing the surgical procedure, there are several factors that must be considered. Gathering information about the index TSA is important and obtaining the patient’s prior operative report can aid in surgical planning. Understanding which company’s product was used, and any specifics in regard to that implant can be valuable as manufactures may have extraction instruments specific to that implant, which may aid in the removal of the components at the time of surgery. The prior operative report also allows for the review of the previous surgical technique and any difficulties or complications that may have occurred during the prior surgery.

There is specific instrumentation we have available for all revision of TSA to RSA cases that may be utilized on both the humeral side and the glenoid side of this revision. For the humerus, we have a set of flexible osteotomes available as these may be used to free the proximal portion of the implant from bony ingrowth or cement around the stem. A forked skid instrument is typically used to remove the modular head of the TSA and is on the field. A high-speed burr is available to remove proximal bone around a collared stem if necessary. A carbide-tip punch (Smith & Nephew, Memphis, TN) is on the field as this instrument is often used to disimpact the humeral stem. Finally, a microsagittal saw is available in case a humeral episiotomy is required in effort to split the humerus to remove a well-fixed stem, and cables are available as well to repair this humeral split.

On the glenoid side, a set of solid curved osteotomes are available to assist in removing a polyethylene pegged or keeled glenoid. In these cases, bone graft may be needed if large glenoid defects are encountered and a femoral head allograft is available on all cases if structural grafting is required. Smaller contained glenoid defects may be packed with cancellous allograft chips and demineralized bone matrix putty and they are available in case they are required.

57.4 Operative Technique: Tips and Pearls

57.4.1 Exposure

The patient is placed under general anesthesia and fully paralyzed for the duration of the procedure. The patient is placed in the beach-chair position with the operative extremity draped free and a padded Mayo stand placed under the elbow to support the arm and assist with arm positioning during the case. A deltopectoral approach is used for this procedure. An attempt is made to incorporate or utilize the patient’s previous incision; however, if the old incision is not appropriately positioned over the deltopectoral interval, we will not let it define our approach and will create a new incision centered directly over the interval.

A no. 10 blade is used for the surgical incision and electrocautery is used to dissect through the subcutaneous tissue. In these revision cases due to previous dissection and scar tissue, it can be difficult to identify the deltopectoral interval. At the superior aspect of the interval, there predictably is a proximal fat triangle defining the interval with the pectoralis major medially and the anterior deltoid laterally. The interval can be identified here, and as the interval is developed, the cephalic vein can be taken in either the medial or the lateral direction when encountered.

After the interval is developed, it is critical to free up the subdeltoid, subacromial, and subcoracoid spaces to mobilize the shoulder and release adhesions that may have formed from the previous surgery. The deltoid may be scarred onto the lateral humerus and dissection is started distally just above the deltoid insertion on the deltoid tuberosity and moves proximally to mobilize the deltoid off the lateral humerus in an effort to develop the subdeltoid space. The subacromial space is then developed and a Cobb elevator can assist in releasing adhesions in this area. The subcoracoid space must then be defined and this is done by identifying the conjoint tendon and then carefully releasing adhesion underneath the conjoint tendon and typically this is done with careful spreading using a tonsil along with a combination of blunt finger dissection.

At this point, the anterosuperior rotator cuff can be visualized. If the revision surgery is being done secondary to subscapularis failure and anterosuperior rotator cuff tearing after the index TSA, then with the simple release of the anterior capsular scar tissue the humeral head will be visualized. If it is a revision in which the subscapularis is still intact, then a subscapularis peel technique is utilized. The subscapularis is released using electrocautery directly off the lesser tuberosity, and with gentle external rotation of the shoulder with the elbow adducted against the body, the shoulder will be atraumatically dislocated and the humeral head of the implant is exposed.

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