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Contact pressures from an instrumented hip endoprosthesis
W A Hodge1, K L Carlson, R S Fijan
1Department of Orthopaedic Surgery, Massachusetts General Hospital, Harvard Medical School, Boston 02114.
The Journal of Bone and Joint Surgery. American Volume
|October 1, 1989
Summary
This study monitored hip implant pressures in a patient for over three years. Unexpectedly high localized contact pressures were recorded, even during simple recovery activities.
Area of Science:
- Orthopedic surgery
- Biomedical engineering
- Biomechanics
Background:
- A Moore-type endoprosthesis was implanted in a 73-year-old patient with a displaced femoral neck fracture.
- Continuous monitoring of hip joint contact pressures using a pressure-measuring prosthesis was initiated.
Observation:
- Contact pressures were measured and telemetered for over 36 months post-implantation.
- Data acquisition occurred periodically, starting from the operating room.
Findings:
- Unexpectedly high localized contact pressures were observed between the acetabular cartilage and the prosthesis.
- Activities like using a bedpan or isometric exercise generated pressures comparable to normal walking.
- The highest recorded pressure was 18 MPa, occurring one year postoperatively when the patient rose from a chair.
- Elevated pressures were consistently noted in the superior and posterior regions of the acetabulum.
Implications:
- These findings highlight the potential for high, localized stress on hip joint implants and surrounding tissues.
- Understanding these pressure dynamics is crucial for improving implant design and patient rehabilitation protocols.
- Further research is needed to investigate the long-term effects of such high pressures on implant longevity and patient outcomes.