Implant for total wrist replacement
A surgical implant for total wrist replacement (TWR) includes a carpal portion and a radial portion to fully encompass both sides of the articulated joint defining wrist movement. The carpal portion is defined by a unitary structure that defines a fused form of the scaphoid, lunate and triquetrum, and bears against the radial portion for permitting articulated motion. The radial portion replaces a distal portion of the natural radius adjacent the wrist, and has the form of a “T” to combine a bearing surface with a stem adapted for implantation in the natural radius. The stem engages a receptacle or bore formed in a truncated end of the natural radius. Both the radial portion and the carpal portion patient-specific members are formed from image scans of the patient's own skeletal structures, and incorporate inverted, contralateral images of healthy structure based on an assessment of deformation in the replaced joint.
1. A surgical implant assembly, comprising:
a unitary carpal implant based on a received proximal carpal row (PCR) scan, the implant based on a fused and wrapped representation of the imaged skeletal structures including a scaphoid, lunate and triquetrum aggregated as a single solid shape, the implant further based on a contralateral, inverted image of a corresponding healthy skeletal structure of a patient anatomy;
a radial implant based on a received radial scan, the radial implant having a bearing portion and an insertion portion arranged in a substantially perpendicular orientation,
the insertion portion defining a stem engageable with a surgical recess formed in a truncated radius of the patient and having a length corresponding to a depth of the surgical recess; and
the bearing portion having an underside adapted for abutting the truncated surface and a bearing surface for engaging the radial implant and a thickness based on a preoperative length of the radius, thereby approximating the natural radius length via the bearing portion.
2. The implant of claim 1 wherein the substantially perpendicular orientation is based on a bearing angle of the preoperative radius relative to a longitudinal axis of the radius.
3. The implant of claim 1 wherein the thickness and an insertion depth of the radial implant are based on anticipated bearing forces on the radial implant and transferred to the truncated, natural radius.
4. The implant of claim 1 wherein the stem has a radial dimension based on anticipated bearing forces on the radial implant and transferred to interior walls of the surgical recess.