Computed tomography-based custom-made stem for dysplastic hips in Japanese patients

Area of Science:

• Orthopedic Surgery
• Biomaterials Engineering
• Medical Imaging

Background:

• Hip dysplasia is a common orthopedic condition requiring surgical intervention.
• Custom-made implants offer potential for improved fit and function in complex cases.
• Cementless hip arthroplasty aims for biological fixation and long-term implant stability.

Purpose of the Study:

• To evaluate the clinical and radiological outcomes of custom-made cementless femoral stems in patients with dysplastic hips.
• To assess the incidence of postoperative complications, specifically thigh pain and stress shielding.
• To analyze the relationship between implant characteristics and stress shielding in this patient cohort.

Main Methods:

• Retrospective analysis of 55 hips in 53 patients with dysplastic hips undergoing surgery.
• Custom cementless femoral stems manufactured from Ti-6Al-4V using computed tomography (CT) data.
• Proximal porous coating with hydroxyapatite (HA) applied to the stems.
• Clinical follow-up averaged 7 years, with radiological assessment using Engh's classification.

Main Results:

• Excellent bone-ingrown fixation was achieved in all hips.
• 9% of patients reported postoperative thigh pain.
• Severe stress shielding was observed in 20% of hips, characterized by lower cortical and canal flare indices and larger stem diameters.
• Overall excellent clinical results were noted despite the stress shielding issue.

Conclusions:

• Custom-made cementless femoral stems provide excellent fixation for dysplastic hips.
• Stress shielding remains a significant concern, potentially influenced by stem design and patient anatomy.
• Further optimization of custom stem design is warranted to mitigate stress shielding and enhance long-term implant performance.