Prosthetic devices to improve joint mechanics in arthroplasty

1. A kit consisting of:

a humeral stem having a central longitudinal axis, the humeral stem configured to attach to a resected bone;

a plurality of proximal components,

wherein each individual proximal component within the plurality has a different volume to any other individual proximal component within the plurality,

wherein each individual proximal component within the plurality has a proximal end, a distal end, a medial portion and a lateral portion,

wherein the medial portion of each individual proximal component within the plurality connects to an articulating component of a humeral side of a shoulder prosthesis when the humeral side of the shoulder prosthesis is fully assembled, the articulating component having an articular surface,

wherein the volume of each individual proximal component is configured to wrap a patient's deltoid muscle around the lateral portion of the proximal component to a desired degree by lateralizing where the patient's deltoid muscle wraps around the device to achieve a desired wrapping angle,

wherein the lateral portion of each individual proximal component is configured to allow the patient's deltoid muscle to slide over an outer surface of the lateral portion of the proximal component when the patient's deltoid muscle wraps around the device in a manner such that the patient's deltoid muscle is allowed to move freely with respect to the proximal component,

wherein the outer surface of the lateral portion of each individual proximal component is a polished surface configured to prevent abrasion or damage to the deltoid muscle as it slides over the outer surface of the lateral portion of the proximal component,

wherein the outer surface of the lateral portion of each individual proximal component has a curvature that is discontinuous with a curvature of the articular surface of the articulating component of the humeral side of the shoulder prosthesis when the proximal component connects to the articulating component of the humeral side of the shoulder prosthesis when the humeral side of the shoulder prosthesis is fully assembled,

wherein the outer surface of the lateral portion of each individual proximal component further comprises a lower portion, extending distally below a proximal end of the humeral stem, and

wherein each individual proximal component is configured to lockingly attach to the proximal end of the humeral stem component.

2. The kit of claim 1 wherein the proximal components include suture bores for soft tissue fixation.

3. The kit of claim 1 further wherein the humeral stem includes an offset taper.

4. The kit of claim 1 wherein the proximal components are modular.

5. The kit of claim 1 wherein the proximal components are configured to allow a surgeon to selectively optimize muscle moment arm, muscle tensioning and muscle stability.

6. A prosthetic device,

wherein the prosthetic device is modular, and consists of:

a humeral stem component having a proximal end, a central longitudinal axis, and a distal end,

wherein the humeral stem component is configured to attach the prosthetic device to a resected bone; and

a one-piece proximal component having a proximal end, a distal end, a medial portion and a lateral portion,

wherein the medial portion of the proximal component connects to an articulating component of a humeral side of a shoulder prosthesis when the humeral side of the shoulder prosthesis is fully assembled, the articulating component having an articular surface,

wherein the volume of the proximal component is configured to wrap a patient's deltoid muscle around the lateral portion of the proximal component to a desired degree by lateralizing where the patient's deltoid muscle wraps around the device to achieve a desired wrapping angle;

wherein the lateral portion of the proximal component is configured to allow the patient's deltoid muscle to slide over an outer surface of the lateral portion of the proximal component when the patient's deltoid muscle wraps around the device in a manner such that the patient's deltoid muscle is allowed to move freely with respect to the proximal component;

wherein the outer surface of the lateral portion of the proximal component is a polished surface configured to prevent abrasion or damage to the deltoid muscle as it slides over the outer surface of the lateral portion of the proximal component;

wherein the outer surface of the lateral portion of the proximal component has a curvature that is discontinuous with a curvature of the articular surface of the articulating component of the humeral side of the shoulder prosthesis when the proximal component connects to the articulating component of the humeral side of the shoulder prosthesis when the humeral side of the shoulder prosthesis is fully assembled,

wherein the outer surface of the lateral portion of the proximal component further comprises a lower portion, extending distally below the proximal end of the humeral stem; and

wherein the proximal component is lockingly attached to the proximal end of the humeral stem component.

7. The prosthetic device of claim 6 wherein the proximal component includes suture bores for soft tissue fixation.