Trabecular materials show great promise for soft-tissue attachment to prosthetic implants. Results with Tantalum have been very encouraging, however, it remains unclear if this in-growth is secondary to the specific metal or its generic structure,. If structure, is there a specific tolerance with respect to porosity and pore size? In a canine model, bulk blocks of porous alumina ceramic were shown to be completely ingrown by four weeks. The type material was not a factor, and effect of pore size revealed that there is a wide tolerance in facilitating in-growth with the larger pores having the greatest attachment strength (p=0.004).
Alumina ceramic implants of fixed porosity (~ 85%) were designed in three pore size ranges (100–200, 250–400 and 600–800 μM). Using an established canine model, six implants (two of each type) were implanted in the dorsal subcutaneous tissues of tweleve mature canines and examined histologically and mechanically at four, eight and sixteen weeks with respect to type, amount and strength of soft tissue in-growth. Soft tissue in-growth was grossly evident in all implants at each time interval, and in each pore size. Microscopic examination revealed neo-vascularized in-growth throughout the implant, without evidence of inflammation or foreign body reaction. Numerous blood vessels were visible at the implant interface and within the porous alumina ceramic structure. With peel testing, the weakest attachment strength was with the small pore size with no differences between the medium and large pore sizes. An increase of attachment strength in each pore size was observed over time. This study suggests that architecture of porous structures in general, and not the type of material used, confers the biologic activity and that there is a wide tolerance for pore size in facilitating this process in soft tissue in-growth. Further study of other inert foam structures will be useful in further defining the assets and limitations of this genre of trabecular materials as a whole. Funding: Stryker Orthopaedics, Mahwah, NJ Please contact author for figures, graphs, and/or diagrams.
Reliable soft tissue attachment to prosthetic implants remains a great clinical challenge in adult reconstruction and oncology. Past efforts using tendon alone have been universally disappointing. With the introduction of trabecular metals, new possibilities present them selves in dealing with this problem. Using an established canine supraspinatus tendon model, reliable and physiologic soft tissue attachment to a trabecular metal prosthesis was achieved, with near normal strength and function. This suggests that this new genre of material can possibly provide better options in dealing with this difficult problem. Direct attachment of tendon to an endoprothesis has applications throughout the field of orthopaedics. The purpose of this study was to devise a soft-tissue attachment device using tantalum foam metal which would allow for early soft tissue reconstruction strength and long term biologic in-growth fixation. A foam metal tendon attachment prosthesis was designed. Using a validated tendon attachment model, twenty-three skeletally-mature canine supraspinatus tendons were sharply detached and then reattached to the greater tuberosity. Ultimate strength, stiffness and gross morphological changes were recorded immediately after surgery and at three and six weeks. Tendon-implant strength as percent of normal rose from thirty-nine percent at surgery, to sixty-seven percent at three weeks, and ninety-nine percent at six weeks (standard deviations thirteen, nineteen, and eighteen percent). Stiffness of construct also approached normal tendon: forty-seven percent at surgery, sixty-two percent at three weeks, and ninety-four percent at six weeks (standard deviations seventy-seven, nineteen, and eighteen percent). Supraspinatus muscle volume decreased from ninety seven (percent of normal) at surgery, to seventy-nine percent at three weeks. By six weeks, the muscle had recovered to ninety percent of normal volume. Gross and histologic analysis revealed complete tendon in-growth and attachment to the prosthesis with the formation of Sharpey’s fibers This study suggests that tendon attachment to a metallic endoprothesis is possible. Near normal physiologic strength and stiffness was achieved six weeks post surgery. Future study should ascertain the micro-anatomy of this attachment and delineate the mechanical conditions necessary for soft tissue in-growth. Funding: Zimmer, Inc., Warsaw, IN Please contact author for pictures, graphs and diagrams.
The influence of advancements in imaging and chemotherapy on patient with dedifferentiated chondrosarcoma was determined. There were forty-two cases in which twenty-seven patients received adjuvant therapy. Median survival was eight months and five-year survival was 4.8%. There was no statistical difference (p=0.62) in survival between patients who did and did not receive chemotherapy, had wide versus radical resection, or had limb sparing versus sacrificing procedures. There were no statistically significant differences between patients treated prior to 1986 and those subsequently. Despite advances, dedifferentiated chondrosarcoma continues to carry a poor prognosis. The routine adjuvant chemotherapy in this population should be questioned The long-term survival for patients that presented with dedifferentiated chondrosarcoma has historically been poor. A large clinical series has not been analyzed in the era of modern diagnostic and treatment modalities. The current study was performed to look at the influence of advancements in imaging and chemotherapy on patient outcome. A retrospective chart review of all cases of patients presenting with dedifferentiated chondrosarcoma at our institution from 1984–2000 was performed. This was done as an extension to a study published in 1986 prior to the era of modern chemotherapy. There were forty-two cases in twenty-five men and seventeen women of average age fifty-six (range twenty-four-eighty-three years). MSTS grades at presentation were IIA(5), IIB(27), and III(10). Three patients underwent biopsy only, nineteen had limb sacrificing surgery, and twenty had limb sparing procedures. Surgical margins were intralesional in three, marginal in two, wide in twenty, and radical in fourteen. Twenty-seven patients received adjuvant therapy (twenty-two chemotherapy only, two radiotherapy only, three combined therapy). Median survival was eight months and five-year survival was 4.8%. There was no statistical difference (p=0.62) in survival between patients who did and did not receive chemotherapy, had wide versus radical resection, or had limb sparing versus sacrificing procedures. There were no statistically significant differences between patients treated prior to 1986 and those subsequently. Despite advances in diagnostic modalities, surgical treatments, and adjuvant therapies, dedifferentiated chondrosarcoma continues to carry a poor prognosis. The routine use of current adjuvant chemotherapy and its inherent risks and benefits in this population should be questioned.
