An alternative method to create extramedullary references in total knee arthroplasty.

Area of Science:

• Orthopedic surgery
• Biomechanical engineering
• Medical device technology

Background:

• Traditional extramedullary alignment in total knee arthroplasty (TKA) often relies on the femoral head center (FHC) and anterosuperior iliac spine.
• This method can lead to variations in achieving neutral limb alignment.

Purpose of the Study:

• To evaluate a novel extramedullary alignment system for TKA that utilizes the overall limb mechanical axis (MA) as a reference.
• To compare the accuracy of the MA method against the conventional FHC method in TKA.

Main Methods:

• A retrospective review of 1018 TKAs was conducted, comparing the FHC group (508 knees) with the MA group (510 knees).
• Radiographic analysis focused on coronal plane limb and prosthesis alignments at two months post-surgery.
• The study included patients with varus osteoarthritis of the knee.

Main Results:

• The MA group demonstrated significantly better accuracy in postoperative limb and femoral component alignments compared to the FHC group.
• Overall limb alignment within 0° ± 5° of the mechanical axis was achieved in 96.1% of the MA group versus 86.6% in the FHC group.
• Femoral component coronal alignment accuracy was also higher in the MA group (98.4%) than the FHC group (92.5%).

Conclusions:

• Using the overall lower limb's mechanical axis as an extramedullary reference improves the accuracy of prosthesis alignment in TKA.
• The MA method provides a more reliable system for achieving correct limb and component alignment during total knee arthroplasty.