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Total Shoulder Arthroplasty Using a Bone-Sparing, Precision Multiplanar Humeral Prosthesis

February 1, 2018 | Surgery
Steven S. Goldberg MD ; Eric S. Baranek MD
Author and Disclosure Information

Authors’ Disclosure Statement: Dr. Goldberg reports that he is a paid consultant and has intellectual property assigned to, and stock and stock options in, Catalyst OrthoScience, the manufacturer of the implant and instruments shown in this article. Dr. Baranek reports no actual or potential conflict of interest in relation to this article. 

Dr. Goldberg is Chief of Orthopedic Surgery, Physicians Regional Medical Center, Naples, Florida. Dr. Baranek is a Resident Physician, Department of Orthopedic Surgery, Columbia University-New York Presbyterian Medical Center, New York, New York.

Address correspondence to: Steven S. Goldberg, MD, Physicians Regional Medical Center–Pine Ridge, 6101 Pine Ridge Road, Naples, FL 34119 (tel, 239-348-4253; fax, 239-304-4929; email, Drstevengoldberg@gmail.com). 

Steven S. Goldberg MD Eric S. Baranek MD . Total Shoulder Arthroplasty Using a Bone-Sparing, Precision Multiplanar Humeral Prosthesis. Am J Orthop. February 1, 2018

TAKE-HOME POINTS

  • Bone-preserving shoulder arthroplasty is now available and rapidly growing in the US.
  • The calibrated, multiplanar instruments and prosthesis shown here allow surgeons to recreate the normal humerus shape with high precision.
  • The elliptical, non-spherical design of the humerus prosthesis has shown improved shoulder kinematics compared to standard spherical prostheses.
  • The implant rests on dense bone proximal to the anatomic neck where bone support is strong.
  • Glenoid implant insertion is routinely performed using this technique and access is facilitated by the angled bone resections.

The success of total shoulder arthroplasty (TSA) is largely dependent on how accurate the proximal humeral anatomy is reconstructed and the glenohumeral relationships are restored.1-4 Numerous studies have demonstrated a relationship of worse clinical outcomes and implant failure with nonanatomic implant placement.5-8 The majority of arthroplasty systems rely on surgeon-dependent decision-making to determine the location of the border of the articular surface and, ultimately, the amount and location of bone to be resected. Even in experienced hands, the ability to reproducibly restore the joint line is inconsistent.3

In contrast, the majority of total knee arthroplasty (TKA) systems have been designed with instrumentation that guides the surgeon precisely regarding where and how much femoral bone must be resected, and the corresponding implant is designed with the same thickness to preserve the location of the joint line. Cutting block instrumentation rather than freehand cuts enables reproducibility of TKA while being performed for an estimated 700,000 times annually in the US.9

To achieve similar high levels of reproducibility in shoulder arthroplasty, a new technique was developed based on the principle of providing instrumentation to assist the surgeon in accurately restoring the proximal humeral joint line. This technical article describes the technique of using a multiplanar instrumented cutting system and matching implants to perform TSA. The technique shown was previously studied and was found to allow surgeons to recreate the original anatomy of the humerus with very high precision.10

The undersurface of the humeral head implant demonstrating a four-plane geometry.

The humeral prosthesis described in this article has an articular surface that is slightly elliptical to more closely match the actual shape of the humerus bone.11 Biomechanical studies have demonstrated that implants designed with a nonspherical shape have more similar motion and kinematics to those of the native humeral head.12 The undersurface of the implant has a concave four-plane geometry that matches with the bone cuts created by the cutting guides (Figures 1, 2). 

Lateral view of the humeral head implant.

This provides rotation stability, and the implant rests on the strong subchondral bone of the proximal humerus proximal to the anatomic neck rather than relying on metaphyseal bone or canal fixation, as recommended by Aldoiusti.13 It also allows optimal implant placement with complete freedom with respect to inclination, version, and medial/posterior offset from the humeral canal. 

Continue to: The implant respects the relationship...

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