Collar-Calcar Contact Reduces Risk for Early Periprosthetic Fracture and Subsidence in Dorr Type C Femora Using...

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Radiology

Background:

• Collared, hydroxyapatite-coated stems aim to improve stability and reduce complications like subsidence and fracture.
• Dorr C femora present unique challenges for cementless stem fixation.
• The direct anterior approach (DAA) is increasingly used for total hip arthroplasty (THA).

Purpose of the Study:

• To evaluate the association between the collar-calcar gap and periprosthetic fracture (PPF) and subsidence.
• To assess outcomes in patients with Dorr C femora undergoing THA via DAA using collared, HA-coated stems.

Main Methods:

• Retrospective analysis of 6,107 THAs, with 387 Dorr C femora using collared, HA-coated stems included.
• All surgeries performed using the direct anterior approach.
• Postoperative radiographs reviewed for collar-calcar gap; outcomes included PPF and subsidence.

Main Results:

• A collar-calcar gap was observed in 4.1% of hips (16/387).
• Periprosthetic fractures occurred exclusively in the gap group (18.8%), and subsidence was higher in the gap group (12.5%) versus the contact group (0.5%).
• The presence of a gap significantly correlated with increased rates of subsidence and PPF (P < 0.0001).

Conclusions:

• Immediate load transfer via collar-calcar contact is mechanically vital.
• Intraoperative assessment of collar-calcar contact is recommended, particularly in Dorr C bone.
• Collared, HA-coated, cementless stems are supported when secure collar-calcar contact is achieved.