Factors affecting the stability of screws in human cortical osteoporotic bone : A cadaver study

• Published in: Journal of bone and joint surgery. British volume Vol. 89; no. 5; pp. 701 - 705
• Main Authors: THIELE, O. C, ECKHARDT, C, LINKE, B, SCHNEIDER, E, LILL, C. A
• Format: Journal Article
• Language: English
• Published: London British Editorial Society of Bone and Joint Surgery 01.05.2007; British Editorial Society of Bone & Joint Surgery
• Edition: British volume
• Subjects: Aged; Aged, 80 and over; Biological and medical sciences; Body Constitution; Bone Density; Bone Screws; Diseases of the osteoarticular system; Female; Femur - pathology; Femur - physiopathology; Femur Head - physiopathology; Humans; Investigative techniques, diagnostic techniques (general aspects); Medical sciences; Middle Aged; Orthopedic surgery; Osteoarticular system. Muscles; Osteoporosis, Postmenopausal - pathology; Osteoporosis, Postmenopausal - physiopathology; Osteoporosis. Osteomalacia. Paget disease; Radiodiagnosis. Nmr imagery. Nmr spectrometry; Risk Factors; Severity of Illness Index; Surgery (general aspects). Transplantations, organ and tissue grafts. Graft diseases; Human; Osteoporosis; Femur; Head; Orthopedic surgery; Stability; Treatment; Screw; Diseases of the osteoarticular system; Bone mineral density; Osteodensitometry; Cortical bone
• ISSN: 0301-620X; 2049-4394; 2044-5377; 2049-4408
• DOI: 10.1302/0301-620X.89B5.18504

We investigated several factors which affect the stability of cortical screws in osteoporotic bone using 18 femora from cadavers of women aged between 45 and 96 years (mean 76). We performed bone densitometry to measure the bone mineral density of the cortical and cancellous bone of the shaft and head of the femur, respectively. The thickness and overall bone mass of the cortical layer of the shaft of the femur were measured using a microCT scanner. The force required to pull-out a 3.5 mm titanium cortical bone screw was determined after standardised insertion into specimens of the cortex of the femoral shaft. A significant correlation was found between the pull-out strength and the overall bone mass of the cortical layer (r(2) = 0.867, p < 0.01) and also between its thickness (r(2) = 0.826, p < 0.01) and bone mineral density (r(2) = 0.861, p < 0.01). There was no statistically significant correlation between the age of the donor and the pull-out force (p = 0.246), the cortical thickness (p = 0.199), the bone mineral density (p = 0.697) or the level of osteoporosis (p = 0.378). We conclude that the overall bone mass, the thickness and the bone mineral density of the cortical layer, are the main factors which affect the stability of a screw in human female osteoporotic cortical bone.