Faculty Bibliography

A new canine model utilizing an implantable chamber with multiple bone ingrowth channels has been used to study the response of intramedullary bone to various implant materials and surfaces. The first group of dogs received implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated (HA-coated) titanium alloy, and polyethylene. A pattern of early initial bone ingrowth by 2 weeks, becoming maximal at 6 to 12 weeks with remodeling to a more mature lamellar bone, and later resorption by 24 weeks was seen for all test groups, with fibrous tissue interfaces covering the smooth test coupons at all time points. Significantly increased bone ingrowth in the sputter-HA coated group was found only at 6 weeks. The second group of dogs received implants with channels lined by surface-roughened coupons of either titanium or plasma-HA-coated titanium, half of which were also packed with a crystalline-HA grouting at the time of surgery. At both 6 and 12 weeks, bone ingrowth was greatly enhanced by the presence of the plasma-HA coating or the crystalline-HA grouting as compared to the uncoated titanium channels. Histologically, bone was seen to bond directly to the plasma-HA coating and the crystalline-HA grouting. A thin fibrous tissue layer was noted between bone and the titanium in most areas, but evidence of direct bone contact to the metal surface was seen. Mechanical testing in tension of intact coupon-bone-coupon units revealed significant strength of the bone-plasma-HA bond, with failure initiating at the metal-HA interface with forces of 15.3 N at 6 weeks, increasing to 44.8 N at 12 weeks. Plasma-HA-lined channels with crystalline-HA packing required similar forces for failure. No significant adhesion strength was noted for the titanium channels at 6 weeks, and only the crystalline-HA-filled channels displayed measurable strength of the bone-titanium interface at 12 weeks, with a force of 9 N needed for failure

A new animal model for examining the intramedullary bone response to various implant materials and surfaces is presented, utilizing an implantable chamber with multiple bone ingrowth channels placed through a cortical defect in the lateral aspect of the distal femur. Twelve adult mongrel dogs received bilateral implants containing channels lined by smooth-surfaced coupons of titanium, titanium alloy, sputter-hydroxyapatite-coated titanium alloy, and UHMW polyethylene. A pattern was detected for all test groups of early initial bone ingrowth by two weeks, which became maximal at six to twelve weeks, followed by remodelling to a more mature lamellar bone and later resorption by 24 weeks, with fibrous tissue interfaces covering the smooth test coupons of all groups at all times. Significantly increased bone ingrowth in the sputter-HA coated group was found only at six weeks

The growth of tendon cell colonies on synthetic fiber materials used as soft tissue implants was compared to the growth of such cell colonies on flat plastic surfaces used as standard cell culture substrates. Fundamental differences in growth characteristics were observed, and a mathematical model was developed

Spontaneous gastroduodenal perforation (SGDP) occurs in cancer patients receiving cytotoxic drugs, corticosteroids, or radiation therapy as primary or adjuvant treatment for their tumors. A retrospective review identified 12 patients from 1974 to 1987 at the Memorial Sloan-Kettering Cancer Center who underwent surgery for SGDP while receiving anticancer therapy. There were five gastric and seven duodenal perforations. Vague abdominal pain was the most common symptom. Exploration was delayed in six patients because of an absence of physical findings. All patients received a Graham omental patch. The in-hospital operative mortality was 33%, with all major complications occurring in those that died. There were no prognostic indicators identified that would preoperatively predict outcome. Aggressive surgical intervention is advised in all patients who have a reasonable chance of worthwhile palliation if not cure

Hydroxyapatite ceramics have been used as bone implants in a number of experimental systems and clinical applications. We have developed a unique experimental model that allows study of the interface between bone and implant materials. A comparison of titanium and hydroxyapatite materials, using this model, has demonstrated the osteoconductive nature of hydroxyapatite and its ability to bond directly to bone

A composite of HA particulate and calcium sulfate hemihydrate has been developed. When this dry material is mixed with either sterile saline or water, the resulting mixture begins to gel. While in the gel or dough state, the composite can be manually inserted or injected under pressure into a bone defect where it sets in situ. The calcium sulfate acts as a binder to hold the HA particles in place. The subsequent resorption of the calcium sulfate leaves controlled porosity for bone ingrowth and attachment to the nonresorbable HA particulate. The combination of calcium sulfate and HA results in a composite with handling properties superior to those of HA alone. Calcium sulfate has a long history of medical use as an implant material. The biocompatibility of the material has been clearly established. The combination of HA and calcium sulfate is likewise extremely compatible as demonstrated in the present studies. Bone ingrowth concomitant with resorption occurs rapidly with efficient conduction of bone from particle to particle. Based on the experiments presented herein, the composite of HA and calcium sulfate may be a useful alternative or adjunct to autogenous bone grafting. Many questions, however, remain regarding long-term tissue response and bone remodeling as well as the efficacy of this material relative to bone grafting