Reverse shoulder arthroplasty is an established treatment for rotator cuff tear arthropathy of the shoulder. In cases of deformity of the glenoid with limited bone stock, implantation of a noncustomized glenoid implant can be challenging. In this technical article, we report 2 cases with severe glenoid deformity. The first case is a 74-year-old woman presenting with rotator cuff tear arthropathy of the shoulder with a severely deformed glenoid. The second case is a 63-year-old woman with deformity of the glenoid after hemiarthroplasty of the shoulder. Both patients were successfully treated with a 3D-printed customized glenoid implant, combined with a noncustom glenosphere and humeral stem.

CASE 1

We present a 74-year-old woman with severe, progressive arthrosis of the right shoulder. On the preoperative computed tomography (CT) of the shoulder, a severe deformed glenoid could be seen, Walch C according to the Walch classification,1 with a posterosuperior defect of the glenoid (Fig. 1). On ultrasound examination, the rotator cuff was degenerative and functionally and anatomically deficient.

FIGURE 1:

Case 1: Preoperative x-ray and computed tomography.

CASE 2

The second case is that of a 63-year-old woman with rheumatoid arthritis, 20 years after placement of a hemiarthroplasty of the right shoulder (Fig. 2). She was treated for a severe central deformity of the glenoid, type A2 according to the Walch classification. Ultrasonography showed a degenerative and functionally and anatomically deficient rotator cuff.

FIGURE 2:

Case 2: Preoperative x-ray and computed tomography (image on the right was mirrored).

Because of the severe deformity of the glenoid in both patients, the results using a standard glenoid prosthesis were expected to give suboptimal results. Therefore, we decided to use a 3D-printed custom-made Glenius Glenoid Reconstruction implant (Materialise NV, Leuven, Belgium). This modular implant consists of a printed titanium glenoid component (Fig. 3), which aims to exactly fit the deformed glenoid. The bone side of the implant is porous to stimulate bony ingrowth. On the external side of the glenoid component, a noncustom glenosphere could be attached. There are many challenges with the use of customized glenoid implants. First, it takes a few weeks for the customized implant manufacturing according to the preoperative plan, and therefore they can only be used in elective cases. Second, the surgical approach to gain exposure to the landmarks for implantation is challenging, and, lastly, extensive surgical releases are required to implant the glenoid component flush with the glenoid articular surface. Informed consent was obtained from both participants included in the report. This informed consent includes also publication of the cases and photographs.

FIGURE 3:

3D-printed implant.

PREOPERATIVE PLANNING

The CT scans were anonimized and sent to the manufacturer of the prosthesis. The implants with desired bone contact were digitally planned by the Materialise engineers according to the surgeon’s instructions using software developed by the same company. The length and direction of the screws were planned to optimize grip and positioning of the screws. In contrast to a standard baseplate, there is no central peg; primary fixation only relies on peripheral screws. After validation of the preoperative planning report by the surgeon, the manufacturer proceeded with the customized implant manufacturing. In addition to the customized implant, the surgeon is also provided with a plastic 3D model of the implant and scapula and a drill guide, all of which can be sterilized and used intraoperatively for test fitting.

SURGICAL TECHNIQUE

We used a deltopectoral approach to the shoulder joint in both patients. The surface of the glenoid was debrided but not reamed; small 2 mm drill holes were diffusely drilled to create a bleeding surface of the bone. The glenoid baseplate was fixated using 5 locking screws, and provided strong fixation. After fixation of the custom-made implant, a 36 mm glenosphere (Aequalis Reversed, Tornier) was attached to the custom-made implant with a screw. In the first patient, a noncustom cemented Aequalis fracture stem (Tornier) size 11 was used. The humeral stem used for hemiarthroplasty in the second patient was removed first by creating a bone window to facilitate the removal of the cement. A noncustom Aequalis regular stem size 11 was used. The bone window was closed with the aid of cerclage wires.

POSTOPERATIVE OUTCOME

Both shoulders were immobilized in a sling for 6 weeks. Postoperative radiographics on day 1, after 3 and 12 months (Figs. 4, 5), showed a good position of the implant. After follow-up of 12 months, both patients were free of pain (Numeric Rating Scale, 0) and were satisfied with the prosthesis. Patient 1 had a total active elevation (raising the arm in the scapular plane2) of 100 degrees. Patient 2 also had a total active elevation of 100 degrees and requested the same surgery for her other shoulder with a similar situation.

FIGURE 4:

Case 1: Postoperative x-ray after 12-month follow-up.

FIGURE 5:

Case 2: Postoperative x-ray after 12-month follow-up.

DISCUSSION

A 3D-printed titanium glenoid reverse shoulder prosthesis was implanted in 2 patients with severe deformity of the glenoid. This type of implant is currently reserved for rare cases in which standard implants using standard techniques cannot be used. The field of 3D printing in shoulder arthroplasty is still unexplored. There is growing attention for 3D-printed patient-specific instruments in aiding the placement of the glenoid component.3,4 This procedure is often called “3D-printed shoulder arthroplasty,” as both the implant and the surgical instruments were custom made.

To our knowledge, only 1 study by Chammaa et al5 described promising results with the implantation of a custom-made shoulder prosthesis. A computer aided design/computer aided manufacturing anatomic shoulder arthroplasty was placed in 37 patients with severe glenoid bone loss. However, the use of 3D printing in reversed shoulder arthroplasty has not described before. Second, the described computer aided design/computer aided manufacturing prosthesis consists of an oversized hip-like glenoid shell. The concept of the Glenius prosthesis, as described in this case report, however, is not much different than that of the standard reversed prosthesis, and uses the standard glenosphere and humeral stem.

With the use of 3D-printed arthroplasty, there are some theoretical risks, which have not occurred in this case report. First, there is a possibility that at the time of surgery, the glenoid is more deformed than it was when the CT was performed. Second, (metal) artefacts could trouble the preoperative planning. In the worst case scenario, this could lead to a prosthesis that will not fit the glenoid appropriately, or screws that are incorrectly placed. Therefore, the manufacturer recommends to operate within 6 months of the CT scan date, and to have the CT scanned following a defined Materialise Glenius scan protocol.

In cases with severe glenoid deformity and bone loss, other less likely treatment options include standard-fit reverse shoulder prosthesis combined with large bone grafts. With the use of preoperative planning, this was described to improve range of motion and outcome scores, with a radiographic ingrowth of the graft in 94% of cases.6 3D-printed arthroplasty has the theoretical advantage of better realization of preoperative planning, because its shape is defined by the production process, which is not the case with a bone graft. Other options include shoulder arthrodesis (not suitable for previous hemiarthroplasty with severe erosion like case 2) and resection arthroplasty. These options will probably limit function more than a custom prosthesis. However, based only on this report, we cannot yet conclude that 3D-printed shoulder arthroplasty leads to better clinical outcome.

This case report describes only 2 patients with short follow-up. Therefore, we cannot assess long-term functional results and the bony ingrowth in the prosthesis. Further, a custom-made prosthesis is, of course, far more expensive than a standard-fit prosthesis. Furthermore, cost-effectiveness still has to be studied. To conclude, 3D-printed reverse arthroplasty of the shoulder is a promising technique to treat highly complex cases; however, before 3D-printed custom-made reverse shoulder prostheses could be included in the standard of care, further research is necessary.

CONCLUSIONS

We implanted a 3D-printed custom-made shoulder prosthesis in 2 patients with rotator cuff tear arthropathy of the shoulder with a severely deformed glenoid. At the last follow-up at 12 months, they were free of pain and were satisfied with the surgery.

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