We have studied the characteristics of bone ingrowth of a new porous tantalum biomaterial in a simple transcortical canine model using cylindrical implants 5 x 10 mm in size. The material was 75% to 80% porous by volume and had a repeating arrangement of slender interconnecting struts which formed a regular array of dodecahedron-shaped pores. We performed histological studies on two types of material, one with a smaller pore size averaging 430 microm at 4, 16 and 52 weeks and the other with a larger pore size averaging 650 microm at 2, 3, 4, 16 and 52 weeks. Mechanical push-out tests at 4 and 16 weeks were used to assess the shear strength of the bone-implant interface on implants of the smaller pore size. The extent of filling of the pores of the tantalum material with new bone increased from 13% at two weeks to between 42% and 53% at four weeks. By 16 and 52 weeks the average extent of bone ingrowth ranged from 63% to 80%. The tissue response to the small and large pore sizes was similar, with regions of contact between bone and implant increasing with time and with evidence of Haversian remodelling within the pores at later periods. Mechanical tests at four weeks indicated a minimum shear fixation strength of 18.5 MPa, substantially higher than has been obtained with other porous materials with less volumetric porosity. This porous tantalum biomaterial has desirable characteristics for bone ingrowth; further studies are warranted to ascertain its potential for clinical reconstructive orthopaedics.

Objective. To determine whether patients with knee or hip osteoarthritis (OA) who have worse physical function preoperatively achieve a postoperative status that is similar to that of patients with better preoperative function.Methods. This study surveyed an observational cohort of 379 consecutive patients with definite OA who were without other inflammatory joint diseases and were undergoing either total hip or knee replacement in a US (Boston) and a Canadian (Montreal) referral center. Questionnaires on health status (the Short Form 36 and Western Ontario and McMaster Universities Osteoarthritis Index) were administered preoperatively and at 3 and 6 months postoperatively. Physical function and pain due to OA were deemed the most significant outcomes to study.Results. Two hundred twenty-two patients returned their questionnaires. Patients in the 2 centers were comparable in age, sex, time to surgery, and proportion of hip/knee surgery. The Boston group had more education, lower comorbidity, and more cemented knee prostheses. Patients undergoing hip or knee replacement in Montreal had lower preoperative physical function and more pain than their Boston counterparts. In patients with lower preoperative physical function, function and pain were not improved postoperatively to the level achieved by those with higher preoperative function. This was most striking in patients undergoing total knee replacement.Conclusion. Surgery performed later in the natural history of functional decline due to OA of the knee, and possibly of the hip, results in worse postoperative functional status.

Objective. To determine whether interleukin-1 (IL-1) or tumor necrosis factor ␣ (TNF␣), or both, plays a role in the excessive degradation that is observed in cultured osteoarthritic (OA) articular cartilage.Methods Conclusion. These results suggest that the autocrine/paracrine activities of TNF␣ and IL-1 in articular cartilage may play important roles in cartilage matrix degradation in OA patients but not in all patients. Inhibition of either or both of these cytokines may offer a useful therapeutic approach to the management of OA by reducing gene expression of MMPs involved in cartilage matrix degradation and favoring its repair.Osteoarthritis (OA) is a slowly progressive degenerative disease characterized by early loss of the tensile strength of articular cartilage (1), which is produced by a fibrillar network composed of type II collagen (CII) (1,2). Excessive degradation of CII (3,4), such as that induced by collagenase, is a feature of OA (5-7) and rheumatoid arthritic (3) articular cartilage. The compressive stiffness of joint cartilage depends on the swelling pressure achieved by hydration of proteoglycan (1). Thus, the net loss of proteoglycan that occurs in the early stage of OA results in reduced stiffness of the cartilage (1,6).