Glenohumeral Arthritis: Reverse Total Shoulder Arthroplasty With Autograft Glenoid Bone Graft
Jonathan O. Wright
Joseph J. King
Derek S. Damrow,
Thomas W. Wright
INDICATIONS
With the advent of reverse total shoulder arthroplasty (RTSA) in the 1990s in Europe and the early 2000s in the United States, the shoulder surgeon now had a tool to better take on very severe glenoid defects. As opposed to anatomic shoulder arthroplasties which generally are fixed to bone with cement, the reverse shoulder has more robust glenoid fixation and can sustain significant shear forces with or without an intact rotator cuff. Today, the surgeon has multiple options to manage a deficient glenoid. Glenoid defects can be addressed from minor to severe using first minor corrective reaming, followed by augmented baseplates or glenospheres, followed by partially supported baseplates using a stilting technique, and finally, in the most severe defects, by bone grafting or custom implants.1 As opposed to the anatomic glenoid, the reverse baseplate has the unique ability to compress graft, which is beneficial for obtaining graft stability and union when bone grafting is performed.
Of note, some surgeons are using humeral head graft on most reverse shoulders to lateralize the glenosphere, commonly termed the “BIO-RSA.”2 We will defer discussion of BIO-RSA in this chapter and focus rather on bone grafting for the treatment of massive glenoid bone deficiency. We generally do not consider bone grafting until we have defects of greater than 30° of retroversion or similar in other quadrants of the native glenoid, with many defects being 40° or more. We have found that in our hands, defects of 30° or less can often be managed by a combination of reaming, metal augments, and sometimes minor stilting.
Regarding the source of bone graft, multiple sources are available. Studies have described successful glenoid bone grafting (often in the revision setting) with autograft using humeral head,3, 4 and 5 distal clavicle,6 and iliac crest7 and allograft using humeral head, femoral head, iliac crest, or femoral neck. In primary arthroplasty, it is our preference to use autograft, and we almost always use the humeral head, as it fits the defect nicely, is readily available in the surgical field, and is otherwise discarded. This is the technique that will be discussed in this chapter.
CONTRAINDICATIONS
Deciding which technique to use to treat a glenoid defect can be complex. For the technique of using humeral head autograft, we describe in this chapter, that there are several relative contraindications that should be considered.
Patient Contraindications
Current smoker
Humeral Contraindications
Deficient humeral head bone stock either due to collapse or severe cystic disease
Severe humeral head avascular necrosis
Glenoid Contraindications
Massive glenoid bony defect to the extent that the central cage/post or screw of the baseplate is unlikely to achieve adequate fixation in native bone. (In these cases, we favor patient-specific, custom implants that can gain additional fixation in the coracoid base and/or scapular spine.)
PREOPERATIVE PREPARATION
Before considering surgery, a thorough knowledge of the patient is important, and comorbidities must be considered. For patients who smoke, we will not move forward with surgical intervention until tobacco use has ceased and has been confirmed by nicotine testing. Our concerns with smoking include challenges of graft union, bone ingrowth/ongrowth to the prosthesis, and higher infection risk. Additionally, rheumatoid arthritis and osteoporosis medications need to be recognized and managed preoperatively to maximize bone quality and decrease the risk of significant immunosuppression at the time of surgery.
When faced with massive glenoid bony defects in the setting of a planned shoulder RTSA, careful preoperative planning is necessary. Our workup includes Grashey and axillary lateral radiographs as well as a high-resolution CT scan with 1 mm or thinner cuts including the entire scapula (See Figure 50-1.) Patients with severe bone loss will be readily noted on a Grashey view, as the greater
tuberosity will be medial to the lateral corner of the acromion, and on the axillary lateral the humeral head will often be medial to the base of the coracoid. In cases of severe defects, a 3D reconstruction available from the CT scan significantly aids in planning a graft for the defect. In addition to evaluating the glenoid defect, one must also make sure there is an adequate humeral head to use for graft (without severe cystic disease or avascular necrosis), or other sites must be planned for. Our typical secondary site for obtaining bone graft is the iliac crest. (Worth noting here, we have moved away from the use of structural allograft and in most revision cases, as humeral head autograft is not available, and have moved instead to using metal to fill the defect, usually in the form of major augments or custom, patient-specific implants.)
tuberosity will be medial to the lateral corner of the acromion, and on the axillary lateral the humeral head will often be medial to the base of the coracoid. In cases of severe defects, a 3D reconstruction available from the CT scan significantly aids in planning a graft for the defect. In addition to evaluating the glenoid defect, one must also make sure there is an adequate humeral head to use for graft (without severe cystic disease or avascular necrosis), or other sites must be planned for. Our typical secondary site for obtaining bone graft is the iliac crest. (Worth noting here, we have moved away from the use of structural allograft and in most revision cases, as humeral head autograft is not available, and have moved instead to using metal to fill the defect, usually in the form of major augments or custom, patient-specific implants.)
 FIGURE 50-1 Case example of preoperative radiographs and CT scan. A, Grashey view, showing the greater tuberosity medialized to approximately the level of the lateral acromion, B, Axillary lateral view, showing medialization to the level of the coracoid base, C, axial CT image showing severe posterior wear of the glenoid, and D, 3D reconstruction of the scapula with excellent visualization of the glenoid defect. |
We are currently using preoperative planning software for all these cases when possible. When that isn’t possible and we are using the CT scan alone, we always reformat the CT scans in the plane of the scapula, as CT scans are formatted in the plane of the body, which can be misleading. Regarding baseplate positioning, we always plan so that baseplates are either neutrally or slightly inferiorly inclined, as superior inclination will lead to higher shear forces at the baseplate/graft/bone interface which should be avoided. It is best to review the plan immediately before surgery so that the plan, including the starting point, the planned glenoid reaming and drilling, and the planned size and orientation of the graft are all fresh in the surgeon’s mind. Intraoperative navigation is very helpful for sizing and orienting the graft, and this is our preference whenever possible. With navigation, bony fixation can be enhanced as the surgeon can essentially “visualize” the glenoid behind the bone graft via the navigation screen, allowing for more accurate placement of the baseplate fixation into native bone. We feel that it is important that adequate implantation of an ingrowth post or cage be in the native bone to achieve some fixation, although the exact amount of ingrowth surface to be placed into the native bone has not been fully elucidated.
TECHNIQUE
Preoperatively plan. The first step is always to perform a careful preoperative plan, as noted above (Figure 50-2.). [Of note, our preferred implant system for this technique is the Exactech Equinoxe Reverse System (Gainesville, FL), so the included figures and some of the steps will be specific to this implant system, although the technique can easily be adapted to use a surgeon’s preferred implant.]
Perform a standard approach to the shoulder. We typically use a deltopectoral approach, as this allows placement of the coracoid tracker for navigation, although the anterosuperior approach is also reasonable based on surgeon preference if intraoperative navigation will not be used.
After the humerus has been exposed, ream the humeral head with humeral head resurfacing reamers to remove any remaining cartilage (Figure 50-3).
Perform a large cut of the humeral head (Figure 50-4). We recommend using a large osteotome to complete the posterior cut (particularly if walking a trainee through the procedure) to avoid the unpleasantness of dropping the humeral head.
Completely expose the glenoid. Ensure that the entire glenoid can be visualized (Figure 50-5).
Shape the humeral head autograft to fit the defect. We prefer to create a graft that is slightly larger than needed initially, particularly superiorly, as this allows for the placement of percutaneous fixation into areas of the graft that will not engage the baseplate. These slightly oversized areas can be removed after baseplate fixation if concerning for impingement (Figure 50-6).Related posts:
Proximal Humerus Fracture: Hemiarthroplasty
Proximal Humerus Fracture: Open Reduction, Internal Fixation—Locking Plate
Anterior Instability: Open Bankart Repair
Arthroscopic Distal Tibial Allograft for Anterior Instability
Glenohumeral Arthritis: Total Shoulder Arthroplasty With Augmented Glenoid
Glenohumeral Arthritis: Hemiarthroplasty With Concentric Glenoid Reaming (Ream and Run)
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