Department of Biomechanics

Patient Specific Implants

Background

Since 1977, we have designed over 2400 custom implants for patients at HSS. General indications for these patient-specific implants include small stature, severe deformity, complex revision, and clinical problems where no known solution exists.

Examples

  1. Extra Small Total Knee Replacement
  2. Swan Neck Hip Stem
  3. Coronoid Replacement

Example 1: Extra Small Total Knee Replacement


(click image to view slideshow)

 

Example 2: Swan Neck Hip Stem

A patient with developmental dysplasia of the hip (DDH) needs a total hip replacement. Engineers are tasked by the patient's surgeon to virtually insert an off-the-shelf, or standard, femoral component into a 3D reconstruction of the patient's CT scan. Due to this patient's femoral deformity, an ideal fit of the standard implant would cause a leg length discrepancy. If this off-the-shelf implant was inserted deeper to maintain limb length, proximal bone would have to be removed. Therefore, a custom implant must be designed. A swan neck hip stem is designed with a varus neck and maintains limb length without sacrificing bone stock. Figure 1 shows a swan neck hip stem next to an off-the-shelf prosthesis and Figure 2 shows a post-op x-ray of a swan neck hip stem.

Swan-neck hip stem video [0.7MB wmv]


Figure 1. Off-the-shelf (left) and custom swan neck hip prostheses (right)


Figure 2. Post-op radiograph of custom swan neck hip prosthesis

Example 3: Coronoid Replacement

Failed internal fixation (plate and screws) of comminuted fracture of the coronoid process.



Pre-op 3D CT reconstruction


Designed a coronoid replacement (hemiarthroplasty) that resurfaces the olecranon & coronoid, articulates with the humerus, and spares the intact medial coronoid tubercle.


1 yr follow-up

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