Accuracy of Humeral Implant Positioning Using a Canal-Sparing Total Shoulder Arthroplasty System

Abstract

Background: Accurate restoration of anatomy is critical in reestablishing proper glenohumeral joint function in total shoulder arthroplasty (TSA). However, even experienced surgeons inconsistently achieve anatomic restoration. This study evaluates whether a new canal-sparing arthroplasty system, designed using the principles of calibrated bone resection and incorporating a nonspherical humeral head prosthesis, can assist in more accurate and reliable reproduction of proximal humeral anatomy compared to a stemmed arthroplasty system. Methods: The difference between the anatomic center of rotation (COR) of the humeral head and the postoperative prosthetic COR (defined as DCOR) was measured in a consecutive case series of 110 shoulder arthroplasties performed by a single surgeon. The first 55 cases used a stemmed arthroplasty system and the subsequent 55 cases used a new canalsparing implant system that uses a multiplanar osteotomy (MPO) during humeral head preparation. Cases with DCOR !3.0 mm were deemed clinically significant outliers. Results: The average DCOR in the MPO group was 1.7 AE 1.2 mm versus 2.8 AE 1.5 mm in the stemmed group (P ¼.00005). The incidence of outliers was lower (14.5% vs 40.0%, P ¼.005), and there were more cases with a DCOR 1.0 mm (32.7% vs 3.6%, P ¼.0001) in the MPO group compared to the stemmed group. Conclusion: The MPO TSA system provided improved accuracy and precision in restoring proximal humeral anatomy compared to stemmed arthroplasty systems, even in its initial use. This alternative method of humeral replacement may increase consistency in restoring proper anatomy and kinematics in TSA.

Anatomic total shoulder arthroplasty using a stem-free ellipsoid humeral implant in patients of all ages

“…We previously reported on this technique as being reliable in replicating the preoperative anatomy and center of rotation in both a cadaveric specimen and in clinical practice. 3,17,18 The mean patient age in this group was 73 years, which is older than the groups studied by Habermeyer, Egger, Churchill, and Berth, where the mean ages were 58, 59, 66, and 67 years, respectively. 6,13,15,20 In those studies, nonstemmed arthroplasty was shown to have very low rates of loosening over time.…”

“…21,23,[25][26][27]38,59 Subsequently, authors have reported highly accurate prosthetic fit in modeling studies using elliptical implants. 3,25 Additionally, studies have demonstrated improved range of motion in external rotation with decreased eccentric glenoid loading. 10,29,30 Therefore, there may be theoretical advantages to an ellipsoid-shaped humeral implant in TSA.…”

“…This technique has been demonstrated in cadaveric and radiographic studies to be highly accurate in replicating the preoperative anatomy. 3,18 The design was inspired by the femoral component in total knee arthroplasty, which rests on dense bone just below the subchondral surface and demonstrates excellent longevity in patients over a wide age range in numerous long-term studies. 2,36,45 In order to address potential challenges encountered with a more conservative bone resection, a glenoid component with angled anchoring pegs that can be inserted from an oblique angle, in the direction of a deltopectoral incision, was developed.…”

Radiographic evaluation of humeral head reconstruction with stemmed and stemless spherical implants compared with stemless elliptical head implants

“…Postoperative anteroposterior radiographs have been shown to be accurate and consistent for detecting prearthritic parameters of the humeral head (CoR and HHH). 1 , 2 , 4 , 10 , 17 , 18 …”

Stemless Total Shoulder Arthroplasty With Orthobiologic Augmentation

“…[11][12][13] Stemless shoulder replacements have been shown to accurately represent the humeral head position independent of the humeral shaft orientation. [13][14][15] This allows for the center of rotation, inclination, retroversion, and offset to be accurately re-created. 13,15,16 In addition to fewer intraoperative complications, stemless designs preserve the humeral bone stock, which facilitates the treatment of periprosthetic fractures and cases of revision surgery.…”