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Canal-sparing total shoulder arthroplasty system may restore proximal humeral anatomy
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A canal-sparing total shoulder arthroplasty system that uses multiplanar osteotomy may restore proximal humeral anatomy with improved accuracy and precision compared to a stemmed arthroplasty system, according to published results.
William N. Levine, MD, and colleagues measured the difference between the anatomic center of rotation of the humeral head and the postoperative prosthetic center of rotation for 110 shoulder arthroplasties. Researchers included 55 cases with a stemmed arthroplasty system (Arthrex Univers II, Arthrex) and 55 cases with the new canal-sparing implant system that used a multiplanar osteotomy during humeral head preparation (Catalyst CSR Total Shoulder System, Catalyst OrthoScience). Researchers deemed cases clinically significant outliers if there was a change in center of rotation of 3 mm or more.
Results showed an average change in center of rotation of approximately 1.7 mm in the multiplanar osteotomy group vs. 2.8 mm in the stemmed group. Researchers found a lower incidence of clinically significant outliers in the multiplanar osteotomy group, with 14.5% of cases identified as outliers in the multiplanar osteotomy group compared with 40% of cases in the stemmed group. The multiplanar osteotomy group also consisted of more cases with a change of center of rotation of 1 mm or less (32.7% vs. 3.6%).
“This novel transformational prosthetic design borrowed from total knee concepts more anatomically replicates the proximal humeral anatomy by creating a series of chamfer cuts. The current study demonstrates that the center of rotation is more reproducibly and accurately replicated with the novel design compared to standard prostheses, where the humeral head is resected,” Levine told Healio.com/Orthopedics. “Clinical studies will need to be performed in the future to determine what, if any, clinical impact these findings will lead to.” – by Casey Tingle
Disclosures: The authors report no relevant financial disclosures.
Perspective
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James Gregory, MD
As shoulder arthroplasty continues to evolve, so too does the recognition of the importance of restoring normal humeral anatomy. However, as Baranek and colleagues point out, even experienced surgeons have room for improvement.
The study by Baranek and colleagues uses a single-surgeon consecutive series of shoulder arthroplasties to compare restoration of humeral head anatomy using a stemmed prosthesis with a spherical head vs. a canal-sparing prosthesis using an aspherical head. The canal-sparing prosthesis allowed for better restoration of the preoperative center of rotation, with fewer outliers. Recreating normal humeral anatomy using a stemmed prosthesis requires mastery of many variables – version, inclination, offset and eccentricity. Additionally, because the native humeral head is elliptical, a trade-off in sizing is required when a spherical prosthetic head is used.
Although the senior author on this paper is a designer of the canal-sparing prosthesis, the results appear convincing. Minimizing variables can improve precision. It remains unclear whether exact reproduction of the proximal humeral anatomy has an effect on clinical outcome, but it appears that prosthetic design can help in our quest for truly “anatomic” shoulder arthroplasty.
McGovern Medical School at UTHealth and UT Physician
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