In vivo metal-ion release from porous titanium-fiber material

Dense and porous Ti, Ti-alloy, and stainless steel specimens were implanted in canine trabecular bone. After 6 and 12 months the specimens were retrieved together with bone tissue immediately adjacent. The trace metal content in the tissue samples was determined using neutron activation analysis, differential pulse polarography, graphite furnace atomic-absorption spectrophotometry, electron microprobe analysis, and laser microprobe analysis. The results are discussed in view of (i) the release of Ti ions, which is larger for porous than for bulk specimens, (ii) the various artifacts arising in electron microprobe (EMP) and laser microprobe mass analysis (LAMMA) determination of compositional gradients of trace metal-ion content in bone tissue, (iii) the absence of measurable quantities of V in bone tissue, and (iv) the difference in local tissue accumulation between Ti, released from Ti specimens, and Ni, released from stainless steel specimens.

Infection of the knee joint with Mycobacterium xenopi

Mycobacterium xenopi infection of the knee joint occurred in a 71-year-old man. Owing to the failure to recognize the "contaminant" initially as a possible etiologic agent, the joint was destroyed and eventually treated by arthrodesis.

Identification of in-vivo vibration modes of human tibiae by modal analysis

When attempting to evaluate the mechanical properties of human bones in vivo by mechanical vibration analysis, some essential requirements must be met. A quantitative relation between measured vibration parameters (e.g., natural frequency) and mechanical bone properties must be available, in-vivo vibration modes should correctly be identified and the associated natural frequencies reproducibly and accurately measured, the influence of joints and soft tissues must be known. These problems were addressed by modal analysis (i.e., experimental determination of natural frequencies, mode shapes and damping ratios) of human tibiae in the following situations: 1) dry excised tibiae, 2) fresh excised tibiae, 3) in-vivo tibiae, 4) tibiae in an amputated leg, in different steps of dissection. In the in-vivo measuring conditions used by the authors, the tibia vibration is practically free-free. Two single bending modes (at +/- 270 Hz and +/- 340 Hz, respectively), each of them corresponding with one principal direction for bending, were identified. The difference between the natural frequencies observed in vivo and those of fresh excised tibiae is almost completely caused by the effect of muscles (added mass and damping), whereas joints and skin play only a minor role. Frequency differences between fresh and dry excised tibiae are largely accounted for by the absence of bone marrow in the latter.

Freeze-drying and analysis of plant and other biological material

The freeze-drying of biological material, which is to be quantitatively analyzed (micro-amount level) for compounds of low or intermediate molecular weight, should be either omitted or handled under strict control. This is because compounds such as amino acids, sugars, flavonoids, glycosides, coenzymes, peptides, etc., might be removed from concentrates and (or) the ground biological material by the high vacuum.

The mechanical characteristics of cancellous bone at the upper femoral region

Mechanical behaviour of trabecular bone at the upper femoral region of human bones has been studied by compression tests on trabecular bone specimens removed from normal femora obtained at autopsy. Compression tests were performed along three different axes of loading on wet specimens and high loading rates. Femoral head specimens proved to be the strongest for any axis of loading. Large variation in compressive strength and modulus of elasticity is seen within and between femoral bone samples. Anisotropy and differences in anisotropy for the different regions have been observed. A significant correlation between mechanical properties (sigma max - E) and bone mineral content of the specimen was found. Tests on whole bone structures demonstrate that removal of the central part of the trabecular bone at the proximal femur reduces the strength for impact loading considerably (+/- 50%).

Patellar tendinitis: pathology and results of treatment

Patellar tendinitis can be considered as an overload lesion in athletes. Anatomical pathology reveals focal degeneration and microtearing at predisposed areas near the insertion of the quadriceps or patellar tendon. Thie prognosis and treatment are dependent on the stage of the affection. A program of conservative treatment is effective in the early stages of the disease but it fails in a high proportion (16/38) of cases in the later stages. Surgery directed towards the tendon, rather than a bony procedure, yielded favourable results in 27 out of 29 patients.

The geometrical properties of human femur and tibia and their importance for the mechanical behaviour of these bone structures

A series of non pathological human tibial and femoral bones have been tested in torsional loading at high strain rates. Elastic (torsional stiffness) and ultimate properties (Tmax) have been determined. A geometrical description of the individual bone structures has been performed by determination of the polar moment of inertia (assuming axial symmetry), variation of this parameter along the long axis of the bone and length of the specimen between the grips. A fairly accurate prediction of mechanical behaviour of bone structures could be obtained using these geometrical parameters. The high variation of elastic and ultimate properties of whole bone structures in torsional loading is primarily the result of the high variation of polar moment of inertia for the different bone specimens.

Skeletal fixation of implants by bone ingrowth into surface pores

An alternative skeletal fixation by bone ingrowth into porous coatings has been studied. Stainless steel fiber coatings using different fiber diameters (50-100 micrometer) and different pore sizes have been tested. Plugs, intramedullary rods and various types of knee prostheses have been implanted in dogs in non functional and also in functional loading conditions. Histological and mechanical evaluation of the bone implant interface has been performed. Consistent bone ingrowth was observed for implants in non functional conditions if the pore size exceeded 70 micrometer. Ingrowth in functional loading conditions requires rigid initial stability of the implant and intimate contact of implantcoating and surrounding bone tissue.

Effect of hydroxyapatite impregnation on skeletal bonding of porous coated implants

Skeletal fixation of permanent implants by new methods such as fixation by mechanical interlocking of bone with porous prosthetic coatings or chemical bonding with bioactive materials shows growing potential. This paper reports on the resulting skeletal fixation of a combined porous and bioactive material. Metal plugs with a porous metal fiber coating impregnated with hydroxyapatite were implanted for 2, 4, and 12 weeks and were compared to the parent porous, nonbioactive, metal fiber material. Statistical analysis of the interfacial failure shear stress, as obtained by mechanical testing, shows there is a marked influence of hydroxyapatite impregnation on the rate of bone ingrowth and the strength of the interfacial bond the few weeks following surgery. Microscopical examination reveals that the apparent stimulation of bone ingrowth into the surface pores of the implant is the reason for the increased rate of bond formation. The results are of particular clinical interest: with an increased rate of bone ingrowth, weight bearing might be allowed much earlier, thus reducing the recuperation period.

Short term bonding behaviour of bioglass coatings on metal substrate

Bioglass specimens were implanted in 11 dogs for periods ranging between two and twelve weeks in order to study the short term bonding behaviour of bioglass coated on metal. Metal fibre porous coated specimens without bone growth inducive microlayer were implanted as controls. The conclusions reached pertain to the validity of push out test results, bioglass short term bonding and the effect of the dipping procedure to coat bioglass on metal: 1. It is impossible to compare the bonding effectiveness of bonding materials tested under slightly differing circumstances, and a fortiori at different laboratories, 2. there is no sufficient evidence to establish a difference in bone bonding strength with regard to trabecular bone of bioglass and metal fibre porous coated specimens at 2 and 4 weeks; at 12 weeks, however, a higher interfacial failure shear strength is obtained with the control porous specimens, 3. bone bonding may be hampered by compositional differences arising as a result of the processing of a bioglass on metal coating. Technologically it is, however, possible to exclude this problem.

Clinical study on internal fixation of femoral neck fractures

A clinical study on the results of internal fixation of femoral neck fractures treated by multiple Knowles pinning was undertaken and correlated with the results of an experimental study. Experimentally, failures were produced by downwards migration of the Knowles pins. This phenomenon accounts for the settling of the femoral head on the neck and the frequency of non-union or malunion in patients with subcapital fractures. The type of fracture, type of reduction and age correlate with failure rate. This has to be explained by biomechanical considerations based upon the mode of failure of the internal fixation. A Garden stage III and IV, a varus or anatomical reduction of the fracture and an old age predispose to failure of the internal fixation and consequent non-union.

Experimental study on internal fixation of femoral neck fractures

The relative strength and the failure mode of internal fixation by multiple pinning and nailing was investigated on 35 specimens. Internal fixation consisted of 3, 5 and 7 Knowles pins, a Smith-Petersen nail or a sliding nail plate. The strength of a specimen with a triflanged nail is only half of that with multiple Knowles pins. There is no significant difference in strength of 3, 5, or 7 pin specimens. The strength of an internal fixation with a sliding nail plate is not superior to the strength of multiple pinning. The mode of failure for the different types of internal fixation is primarily a crush fracture of the supporting trabecular bone at the femoral neck with downward and outward migration of the pins or nail. Except with the fixation with 3 pins where an initial bending could be observed, failure is not a plastic deformation of the internal fixation device.

[Sex hormone binding globulin (SHBG), a new metabolic in vitro thyroid function test]

SHBG (sex hormone binding globulin) is a carrier protein for the sex hormones testosterone and estradiol with a molecular weight of about 95000 dalton. It can be used as a metabolic test of thyroid function. SHBG was measured by the adsorption method of Mickelson and Petra; the SHBG contained in serum is incubated with 3H-5alpha-dihydrotestosterone and adsorbed to a cellulose filter. Thirty-eight female patients with hyperthyroidism before treatment had markedly elevated levels of SHBG (x +/- SD: 4.85 +/- 2.4 microgram DHT/100 ml) compared with normal controls (1.50 +/- 0.57; p is less than 0.001). A good correlation between the thyroid hormones and SHBG could be domonstrated which was better for T3 than for T4:r =0.76 (p is less than 0.001) for T3 and r= 0.65 (p is less than 0.001) for T4. This agrees with the clinical finding that the circulating T3 level is a better index of the metabolic severity of thyrotoxicosis than T4. After radioiodine treatment SHBG returns to normal values in euthyroid patients (1.38 +/- 0.8; n = 15) and remains elevated in persistent hyperthyroidism (3.99 +/-1,6; n = 67). Even in patients with persistent biochemical hyperthyroidism who are completely euthyroid on clinical examination, SHBG remains high. Despite lack of evidence of clinical hyperthyroidism, this metabolic test demonstrates the biologic significance of merely biochemical hyperthyroidism. Estimation of SHBG as a metabolic thyroid function test in vitro is of special value for the evaluation of patients showing discrepancies between the clinical and biochemical states and for borderline hyperthyroidism.

Patellar tendinitis (jumper's knee)

A jumper's knee is an overload lesion of patellar or quadriceps tendon near its insertion at the lower or upper pole of the patella. If conservative treatment fails, an operation can be performed in Phase 3 where disabling symptoms, are present. The necrotic tissue in the patellar tendon is excised. The early results of this surgery are encouraging.