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Earlier in vitro studies showed that a compliant layer between a metal surface and trabecular bone improved the load distribution. In this study, the behavior of a compliant layer of Dacron velour was investigated in vivo using a patella resurfacing in a sheep as a model. Bilateral cases were used to compare the velour interface with a direct metal-to-bone interface. For the metal patellas, a fibrous layer developed adjacent to the metal while the underlying bone formed a new subchondral-like layer. With the velour interface, fibrous tissue invaded the velour, followed later by bone, which sometimes reached the metal surface. For follow-ups of 8 months or more, the load across the interface was transferred over localised patches, for both the press-fit and velour interfaces. There was no significant difference in the areas of contact. There was evidence that this was due to the irregularity of the bony surface beneath the fibrous layer, or to bone nodules actually growing up to the metal. It was concluded that in this in vivo model, the velour layer did not retain a more uniform load distribution compared with the press-fit joint, due to the nature of the bone and fibrous tissue that formed at the interfaces.

A photoelastic coating method was used to study the strain patterns on the surface of the femur, before and after insertion of femoral stems. The anatomically shaped stems were press-fit without a collar, press-fit with a collar, and press-fit with proximal cementing to approximate a bone ingrowth situation. The strain patterns of the intact femurs were consistent with bending. The pattern changed considerably after stem insertion, probably due to the stiffening effect of the stems. Nevertheless, the collarless press-fit stem preserved 64% of the magnitude of the proximal medial strain. The collar restored the average to normal, but the surface strains varied because of the localized regions of contact between the collar and the bone. Proximal cementing gave results similar to those of the collarless press-fit. The press-fit stems often showed local patches of high strain, probably reflecting local endosteal contact points. Local high stresses at the level of the distal tip were seen in only a few instances.

Chronic (24 h) insulin treatment and/or glucose deprivation of differentiated rat L6 skeletal muscle cells resulted in an increase in glucose transport activity and a 2-3-fold increase in the number of plasma membrane-associated cytochalasin B binding sites and immunoreactive glucose transporters. In contrast to the acute effect of insulin, chronic treatment did not decrease the number of cytochalasin B binding sites or immunoreactive glucose transporter proteins present in intracellular low density microsomes. Although acute insulin stimulation of glucose transport activity was not affected by cycloheximide, chronic insulin stimulation of glucose transport activity and glucose transporter protein were decreased. In contrast, the stimulation of glucose transport activity by both acute and chronic glucose deprivation were cycloheximide-insensitive. Previously we have reported that chronic insulin treatment transiently induces the rat brain/HepG2 glucose transporter subtype (GLUT-1) mRNA, whereas glucose deprivation induces a substained increase (Walker, P. S., Ramlal, T., Donovan, J. A., Doering, T. P., Sandra, A., Klip, A., and Pessin, J. E. (1989) J. Biol. Chem. 264, 6587-6595). Consistent with these data, nuclear run-on analysis demonstrated a transient 3-fold increase in the rate of GLUT-1 glucose transporter mRNA transcription induced by either chronic insulin treatment or glucose deprivation. The combination of chronic insulin treatment with glucose deprivation resulted in a more persistent 3-4-fold increase in transcription rate than either treatment alone. These data demonstrate that prolonged insulin- and glucose-dependent regulation of glucose transporter function occurs by a complex mechanism which includes enhanced GLUT-1 mRNA transcription and glucose transporter synthesis, as well as changes in the subcellular distribution of glucose transporter proteins.

Twenty-three knees were sectioned, digitized, and standardized to determine the 'average' three-dimensional bony geometry and ligamentous attachments. Data on normal knee motion were obtained from a cadaveric study. An algorithm was written to simulate three-dimensional patella motion. Verification of the knee model was achieved by determining femoro-tibial and patello-femoral contact locations, as well as ligament length patterns, and comparing the results with published data. The criterion for maximum predicted knee motion with a prosthesis in place was the length of the posterior cruciate ligament. Three total knee replacement surfaces were mathematically generated: flat, laxity and conforming. A greater flexion angle was obtained with a flat tibial surface than for the laxity or conforming. Posterior tibial component displacement increased the range of motion, but only slightly. For all tibial surfaces, increased range of motion was achieved with a 10 degrees posterior tilt of the tibial tray. Anterior femoral component displacement increased motion due to reduction in posterior cruciate tension during flexion. The results are applicable to the design and surgical technique of total knee replacement.

Revision rates, complication rates, and the bone-cement interface reaction of 1,069 condylar total knee replacements were reviewed to help decide if conventional total knee replacement continues to be appropriate for the older low-demand patient. This knee replacement series was also compared with two published series of total hip replacements from the same institution. The conclusions are (1) in medium-term follow-up, total knee replacement is as good as or superior to total hip replacement and (2) based on bone-cement interface analysis, survival of total knee replacement is expected to be superior to conventional total hip replacement ten years postoperatively.

Total knee replacement has come of age, and long-term results are much better than those for total hip replacement. The designs of the late 1980s have addressed function, mobility, wear, and long-term survival for the young and active. Conventional, cemented knee arthroplasty is highly successful and well represented by the state of the art in the Kinemax total knee replacement prosthesis. This design also has the capability of treating the postseptic knee, the knee that requires extensive bone grafting, and, experimentally, the young, the active, or the overweight patient.

Bone shape and composition and the configurations and interface conditions of implant components influence the stability of the joint in various ways. A stable interface depends on overall stress and microstress distribution on the bone, particularly trabecular bone. Pressure pattern studies illustrated the effect of tibial component design on overall pressure distribution. Experiments in knee joints of sheep showed that a velour layer interposed between a metallic implant and bone induces fibrous ingrowth. It was proposed that this situation could reduce peak microstresses in trabecular bone.

Intestinal glucose uptake was measured in normal and dwarf chickens from lines selected fro high and low body weight. Jejunal tissue rings were excised from 9-week-old chicks and incubated in a medium containing .002 M glucose. Significantly more glucose (micromoles per gram dry tissue weight) was absorbed by tissues from the low weight line when compared to tissues from the high weight line. The dwarf gene, dw, had no effect on glucose Uptake.

A radiographic study of 45 knees immediately and at least two years after operation showed that the average depth of cement penetration was 1.5-3.0 mm at different locations around the interface and that there was a strong inverse relation between the development of radiolucency and initial cement penetration. In laboratory studies of penetration in the upper tibia, penetration was approximately proportional to bone pore diameter and to the square root of the applied pressure and inversely proportional to the time after initial mixing. There was a low correlation of the tensile strength of the cement-bone bond with the depth of penetration, probably due to the variability of the trabecular bone strength. Failure occurred by direct cement pullout or by partial or total fracture through the bone. In light of all factors, the suggested ideal depth of cement penetration is 3-4 mm. This penetration can be achieved by using the left-lift method about four minutes after initial cement mixing, but with some selective prepenetration around the periphery of the tibia.

The purpose of this study was to determine the forces in the glenohumeral joint for isometric abduction (including all directions of rotation) in the plane of the scapula. The lines of actions of muscles were obtained from 3 upper quarter specimens, electromyographic data was used, as well as geometrical parameters of shoulder motion. The main assumption made in the analysis was that the force in a muscle was proportional to its area times the integrated electromyographic signal. The resultant force reached a maximum of 0.89 times body weight at 90 degrees of abduction, while the shearing component up the face of the glenoid was a maximum of 0.42 times body weight at 60 degrees of abduction.

An apparatus was developed to study the movement, strength, and manipulative ability of the hand. To obtain normal values, measurements were made on 80 women and 65 men between the ages of 17 and 70 years. As a comparison, 30 female patients with severe rheumatoid arthritis were studied. There was little difference in the motion between men and women and among the different age groups. In pinch strength men were 40 percent stronger than women, but in grip strength men were twice as strong. In manipulative ability, there was a decline with age. The arthritic patients were compromised severly in both active motion and strength. In the latter they were between one third and one tenth of normal. Manipulative ability was one half of normal. A measurement system, such as described, could be used for the evaluation of results of various operative procedures.

We studied the bone adaptation in a retrieved femur six years after implantation of an Austin Moore prosthesis. Strains caused by loading of the femoral head and greater trochanter were measured in this femur as well as in the contralateral, normal femur before and immediately after postmortem implantation of a prosthesis. Immediately after implantation the strains were abnormally high, particularly in the calcar region. However, six years after implantation all strains were close to normal. This was found to be due to an increase in both the bone density and the bone area. Changes were also noted in the structure of the osteons, particularly adjacent to areas of endosteal compressive stress-transfer.

A stylized wedge-shaped defect was created in the medial plateau of autopsy specimens of the tibia to evaluate methods for fixation in total knee arthroplasty. A series of tibial components was inserted by five different methods. With each method loading of up to 1780 N axially and a varus load of 1340 N at 28 Newton-meters were assessed. The vertical deflections of the medial and lateral sides of the tray relative to the bone were measured while bending of the stem was recorded with strain gauges. The greatest deflections occurred when cement alone filled the defect; only slight improvement resulted from the addition of two cancellous screws to buttress the metal tray. Further improvement occurred when solid spacers of Plexiglas or metal were used. Finally, the most secure support was obtained with an integral custom-made tibial component. A central stem 70 mm long carried 23%-38% of the axial load, considered useful in the situation of deficient proximal bone. A metal wedge was considered an acceptable alternative to a custom-made component and may prove useful in the reconstruction of tibial bone stock defects.

The effects of cemented acetabular components on the strains in the pelvis were determined experimentally. Four components were tested: A plain metal hemisphere; a metal hemisphere with a triflange; a hemisphere with an iliac peg; and a hemisphere with a complete flange and a peg. Loading was carried out in neutral, flexion, and extension directions. The subchondral bone was only slightly reamed, and components were cemented and tested successively. For the intact hip joint, the strains on the superior acetabular rim were much lower than those on the posterior rim. After placement of the components, the tensile strains on the rim decreased by 22-54% while the compressive strains increased by 0-25%. The bone on the medial inferior surface was subjected to 65% less tensile strain and 48% more compressive strain in neutral and extension loading. There were no great differences between the four styles of acetabular component.

Incubation of human placenta membranes with low concentrations (0.1-0.2 mM) of dithiothreitol (DTT) increased insulin binding approximately 1.4-fold, while 10 mM DTT completely inhibited insulin binding. In contrast, treatment of rat adipocyte membranes with 0.5-2.0 mM DTT increased tracer insulin binding 3- to 6-fold, while higher levels of DTT (10 mM) also fully inhibited insulin binding. Scatchard analysis of insulin binding revealed that DTT treatment of adipocyte membranes resulted in an increase in both the high and low affinity dissociation constants. Purification of adipocyte insulin receptors by wheat germ agglutinin-Sepharose chromatography, followed by insulin-agarose affinity chromatography, resulted in loss of DTT stimulation of insulin binding. Comparison of insulin receptors purified from rat adipocytes or human placenta membranes revealed no significant differences in the DTT sensitivities of insulin binding or protein kinase activities. These data suggest that the functional properties of the rat adipocyte insulin receptor are modified by its membrane environment compared to those of insulin receptors in placenta membranes or purified insulin receptors in detergent solution.

Ten fresh knee specimens with prosthetic components inserted were tested in a loading rig. Compressive and shear force were applied to the femur with the tibia held fixed. The location of the femoral-tibial contact points was measured. The contact reaction forces, the shear forces, and the rocking moments transmitted to the tibial component were calculated. The variations in the test conditions were: high and low compressive force, flexion angles of 0 degree, 45 degrees, and 90 degrees, three curvatures of tibial plastic inserts, and the posterior cruciate retained or resected. When the posterior cruciate was retained, the contact points were close to the center of the component; for cruciate resection, the contacts were close to the anterior of the component. The shear forces and rocking moments were higher for cruciate resection, but the contact reaction forces were lower. There is a wide variety of knee prosthesis designs, but the amount of inherent stability between the femoral and tibial surfaces, and whether the posterior cruciate ligament is retained or sacrificed, are two of the most important design variables. This study shows that cruciate resection increases the shear forces and the rocking moments to the tibial components and that additional fixation means may be necessary to compensate. On the other hand, cruciate retention with low conformity gives higher contact forces, which may lead to more wear in the long term. Cruciate sacrificing designs with intercondylar guiding surfaces are a separate category of design and were not considered in this study.

The implant-bone fit is critical to the longevity of press-fit total hips. Maximum contact on the internal cortical bone surface, especially proximally, produces more normal strain values and reduces micromotion and sinkage. Stem design computer software was developed to design both individualized hip stems that maximize implant-bone contact for a unique anatomy, and average anatomic hip stems in which the mean error of fit is minimized for many patients. Cadaver femurs were used to test the following two hypotheses: (1) Average anatomic stems, designed using the optimal-fit software for an average femoral geometry, improve implant-bone fit when compared with standard stems; and (2) Individualized optimal-fit stems provide an even better fit than average anatomic stems. Results showed that the average anatomical stems fit better than the standard stems. However, the individualized hip stems, designed from individual three-dimensional geometry data, fit the best.

D-Glucose deprivation of primary rat brain glial cell cultures, by incubation with 25 mM D-fructose for 24 h, resulted in a 4-5-fold induction of D-glucose transport activity. In contrast, 24-h D-glucose starvation of primary rat brain neuronal cultures had only a marginal effect (1.5-2-fold) on D-glucose transport activity. Northern blot analysis of total cellular RNA demonstrated that under these conditions the rat brain glial cells specifically increased the steady-state level of the D-glucose transporter mRNA 4-6-fold, whereas Northern blot analysis of the neuronal cell cultures revealed no significant alteration in the amount of D-glucose transporter mRNA by D-glucose deprivation. These findings demonstrated that the D-glucose-dependent regulation of the D-glucose transporter system occurred in a brain cell type-specific manner. The ED50 for the D-glucose starvation increase in the D-glucose transporter mRNA, in the glial cell cultures, occurred at approximately 3.5 mM D-glucose with maximal effect at 0.5 mM D-glucose. Readdition of D-glucose to the starved cell cultures reversed the increase in the D-glucose transporter mRNA levels and D-glucose transport activity to control values within 24 h. The increase in the D-glucose transporter mRNA was relatively rapid with half-maximal stimulation at approximately 2 h and maximal induction by 6-12 h of D-glucose deprivation. A similar time course was also observed for the starvation-induced increase in D-glucose transport activity and D-glucose transporter protein, as determined by Western blot analysis. These results document that, in rat brain glial cells, D-glucose transport activity, protein, and mRNA are regulated by the extracellular D-glucose concentration. Further, this suggests a potential role for hyperglycemia in the down-regulation of the D-glucose transport system in vivo.

Dynamic three-dimensional motion analyses of 15 fresh human knee joints subjected to combinations of flexion velocity and moment, internal and external femoral torque, and horizontal shear before and after sectioning the ACL were performed. ACL deficient specimens demonstrated marked anterior instability without rotational instability. The pivot shift phenomenon occurred with an isolated ACL deficiency and was the result of anterior instability. The pivot shift was accentuated by external femoral torque, decreased by internal femoral torque, and was present in the absence of any applied torque. The pivot shift produced a sudden directional change in the motion of both femoral condyles and may be responsible for the meniscal degeneration that accompanies chronic ACL deficiency.

A third Finnish En(a-) individual (ERP) with alloanti-Ena has been identified. Subsequent family studies revealed that ERP is distantly related to the 2 previous Finnish En(a-) propositi. Serologically, ERP's erythrocytes were found to be M-N-'N'+S-s+U+En(a-)Wr(a-b-) and were sialic acid deficient. SDS-PAGE studies confirmed that the red cell membranes lacked the MN-sialoglycoprotein, glycophorin-A. ERP's serum contained an IgG antibody which demonstrated two separable specificities, a ficin-sensitive specificity (anti-EnFS) and a ficin-resistant specificity (anti-EnFR), which reacted by the indirect antiglobulin technique. The antibodies were probably pregnancy induced, as ERP had never been transfused. A 51Cr-labelled red cell survival study showed that the antibodies were capable of causing significant destruction of incompatible red cells.

The results of total knee arthroplasty (TKA) have improved steadily during the past decade due to refinements in design, fixation, and surgical technique. A review of the evolution of prosthetic design and of the clinical performance of the concept of cruciate-sparing knee arthroplasty provides both direction for improvement and cause for optimism. The results of 798 TKAs performed in one institution were reviewed to validate the principles and concepts of prosthetic design and surgical technique. During the years reviewed the incidence of good and excellent results rose from 67% to 92%, while revision rates declined. Failures resulting in revision were due to loosening in 1.3% of the knees, patellofemoral pain in 1.8%, and infection in 0.4%. Patients with rheumatoid arthritis (RA) achieve results similar to those of patients with osteoarthritis with regard to range of motion and pain relief; the polyarticular nature of RA results in some decrease in functional outcome, primarily related to disease in other joints. In the relatively short follow-up evaluation, the failure rate is acceptably low, and radiolucent lines, indicative of potential later failure, appear to be diminishing in frequency and extent. The improving success rate in each successive series of TKAs reviewed in this paper provides grounds for optimism regarding the future of TKA, and important lessons can be derived from the failures.

Customized knee braces for three normal subjects were instrumented to monitor the forces and moments across the hinges as the subjects performed various activities. The forces and moments were taken to represent a mismatch between actual knee motion and the motion the brace sought to impose. The different hinge designs studied were fixed axis, gear-on-gear, rack-and-pinion, and natural 3-D; they showed only moderate differences in forces. Much larger differences were seen if the hinges were offset 12 mm from the ideal placement. Posterior placement resulted in the least force and anterior placement the highest. The mismatch of knee motion to brace motion would probably lead to abnormal ligament lengths and tensions and other internal mechanical changes, as well as to pistoning and discomfort. The results of this study have implications on brace design, selection, and placement.

Differentiated rat L6 skeletal muscle cell cultures maintained in glucose-deficient medium containing 25 mM xylose displayed a rapid, reversible, time- and concentration-dependent 3-5-fold increase in glucose transport activity. Glucose deprivation in the continuous presence of insulin (24 h) resulted in an overall 9-10-fold stimulation of glucose transport activity. In contrast, acute (30 min) and chronic (24 h) insulin treatment of L6 cells maintained in high glucose (25 mM)-containing medium resulted in a 1.5- and 4-fold induction of glucose transport activity, respectively. Acute glucose deprivation and/or insulin treatment had no significant effect on the total amount of glucose transporter protein, whereas the long-term insulin- and glucose-dependent regulation of glucose transport activity directly correlated with an increase in the cellular expression of the glucose transporter protein. In situ hybridization of the L6 cells demonstrated a 3-, 4-, and 6-fold increase in glucose transporter mRNA induced by glucose deprivation, insulin, and glucose deprivation plus insulin treatments, respectively. Similarly, Northern blot analysis of total RNA isolated from glucose-deprived, insulin, and glucose-deprived plus insulin-treated cells resulted in a 4-, 3-, and 9-fold induction of glucose transporter mRNA, respectively. The continuous presence of insulin in the medium, either in the presence or absence of glucose, resulted in a transient alteration of the glucose transporter mRNA. The relative amount of the glucose transporter mRNA was maximally increased at 6-12 h which subsequently returned to the basal steady-state level within 48 h. These data demonstrate a role for insulin and glucose in the overall regulation of glucose transporter gene expression which may account for the alteration of glucose transporter activity of muscle tissue observed in pathophysiological states such as type II diabetes mellitus.

The anterior-posterior and rotatory laxities of 14 total knee prosthesis designs were measured in a loading rig with compressive, shear, and torque loads representative of physiologic loads. The measured laxities covered a wide range, both greater and smaller than that of the anatomic knee. This range was mainly due to the curvature or flatness of the plastic tibial surface and conformity with the femoral component. Pressure patterns showed the corresponding contact track and area on the tibial surfaces. It is proposed that for normal function, the laxity of the device should complement the remaining anatomic structures to produce a combined laxity resembling that of the normal knee. Excessive prosthetic laxity will lead to the risk of instability, soft tissue attenuation, edge-loading on components, and high contact stresses on the plastic. Inadequate prosthetic laxity may lead to altered kinematics and excessive stresses at the interface, running the risk of long-term loosening. The authors show the laxities of many currently used devices, providing important background information for assessing the role intrinsic prosthetic constraint might play in total joint performance in clinical analyses.

The Kinematic rotating hinge offers a solution as a salvage procedure for severely deformed and unstable "end-stage" knees. Excellent short-term results in terms of pain relief can be achieved, and motion up to 130 degrees is possible, depending on the condition of the quadriceps mechanism and the extent of scarring from previous operations. Care must be taken to avoid cortical penetration, especially in cases of hinge revisions, osteoporosis, thin-walled bones, and the presence of old cement. As with any total knee arthroplasty, care must be taken to achieve optimal rotatory alignment of the tibia beneath the femur to guarantee good patellar tracking.

One thousand sixty-nine consecutive cemented Kinematic Condylar total knee arthroplasties performed by one group of orthopaedists were studied. The maximum follow-up period was 7 years. Most patients had rheumatoid arthritis or osteoarthritis, and the average patient age was 67 years (range, 12-90 years). Aseptic revisions for loosening were required for only one tibial component and six patella components. Average postoperative flexion was 2.5-107 degrees. The preoperative to postoperative change in range of flexion was not affected by the tilt angle of the tibial component in the sagittal plane. With the use of external alignment guides, the average postoperative alignment was ideal but the standard deviation was high; the standard deviation and the extremes were lower when intramedullary guides were used. There was a 14% incidence of femoral radiolucency and a 30% incidence of tibial radiolucency, which increased only slightly with time. Most radiolucencies on the tibial side were small and restricted to the extreme edges; rarely did radiolucency occur around the central peg. More than one half of the thicker radiolucencies occurred adjacent to wedge-shaped bone defects that were filled with cement.

Although promising, the available data concerning drinking-related locus of control have been almost entirely limited to treatment samples of white men. The major purpose of this study was to extend our understanding by comparing the drinking-related expectancies of three groups of Native Americans: problem drinkers, nonproblem drinkers and recovered alcoholics. Multivariate analyses were employed to control statistically for important sociodemographic differences between groups and included a test of the possibility that sex moderated the relationship between drinking status and drinking expectancies. As predicted, problem drinkers reported significantly less personal control of alcohol use than either nonproblem drinkers or recovered alcoholics. There were no significant differences between nonproblem drinkers and recovered alcoholics. Native American men were found to hold significantly more external orientations towards drinking than did women. The results were discussed in terms of comparisons with the available literature, and future research needs were identified. The findings provide indirect support for current treatment philosophies that seek to modify patient perceptions of the controllability of drinking behavior in a more internal direction.

A cement impactor achieved adequate and uniform cement penetration consistently on the upper tibial surface. The penetration obtained, from 2.5 to 5.5 mm in all areas, is within the range of penetration found desirable by previous studies. Unlike most other methods, this technique is simple and achieves good penetration in peripheral areas, which have been shown to be the earliest and most frequent sites of radiolucency at the bone-cement interface.

A computer model of 23 knees was obtained by embedding, slicing and digitizing the bone outlines and ligament co-ordinates. Using co-ordinate transformations, various three-dimensional motions were imposed on the knees, and calculations made of femoral-tibial contact error, contact point locations and ligament lengths. Significant deviations in these parameters were noted for abnormal motions including the elimination of internal-external rotation and a-p displacement and the misplacement of a hinge producing correct motion. The resulting mismatch could result in shear in soft tissues, cuff-to-skin slippage and inaccurate ligament length patterns.

Fourteen knees were studied by a method called spatial location, to determine the contact and load-bearing areas between the femur and the upper tibia in non-loaded and loaded conditions, at various angles of flexion. Under no load, contact occurred primarily on the menisci; the lateral aspects contacted at 0 degrees flexion, moving to the posterolateral aspects at 90 degrees flexion. An area of cartilage which frequently contacted was the medial tibial spine. Under loads of up to 150 kg, the lateral meniscus appeared to carry most of the load on that side of the joint, while on the medial side, the load was shared approximately equally by the meniscus and the exposed cartilage. These findings were verified on two knees by measuring contact pressure with a miniature transducer. Two implications of these findings are that the area of load-bearing is greatly increased and that the stability of the knee joint is enhanced by the menisci.

Experimental studies of flexion-extension motion were carried out on five fresh elbow autopsy specimens to determine the average axis of rotation (AAR). The AAR is defined as the best fit single axis of rotation for the full range of flexion-extension. AAR was determined on all five elbows and found to approximate the center of the capitellum and trochlea. The motion of the elbows approximated a fixed axis, and the carrying angle defined in reference to humeral shaft and forearm axis decreased from 13 degrees to 22 degrees in extension to close to zero in full flexion. The average axis of rotation, with guidelines for its anatomic location, was used as the basis for the design and placement of a hinge-distractor in treating posttraumatic elbows with poor motion.

Historical review up to 1969 showed the emergence of conservative hemiarthroplasty resurfacings and rigid all-metal hinges. The first cemented metal-on-plastic design, introduced in 1969, began a decade in which a large number of different condylar designs were introduced. Variations of these condylar replacements in terms of femoral-tibial surface conformity, the fixation elements, and the provision for the patellofemoral joint produced wide variations of clinical results. In parallel with these condylar replacement designs, unicompartmental and both lax and fixed hinges were still used for particular indications. A review of all of the different design types showed that the most successful results were obtained with partially conforming condylar replacements with provision for the patellofemoral joint. Although cemented condylar replacement components composed the majority of the clinical reports, press-fit uncemented designs also had significant promise. The results of unicompartmental designs depended dramatically upon the indications. Present hinged replacements, whether lax or fixed-axis, produced problems that were sufficiently serious to restrict their use to cases in which condylar replacements were distinctly inadequate. Despite the success of condylar replacements at up to 10 years follow-up, a number of problems remain. These include optimizing the femoral-tibial geometry for maximum range of motion, minimum loosening, and minimum wear. Longer-term problems include improved design for long-term fixation and reduction of wear of polyethylene by optimum surface geometry, by better material quality control, or by improved materials. Whichever instrumentation system was used, surgical parameters such as component placement and sizing were shown to affect the potential range of motion. Considerations of design were given for revision cases in which condylar replacements were inadequate. Certain design suggestions were made for minimizing the serious problems used with lax or fixed-axis hinged replacements.

Twelve different tibial components were compared for fixation. The components included compartmental, anteriorly joined, posterior-cruciate retaining, and one-place with one, two, or three fixation posts; all-plastic or with a metal tray. The apparatus applied compressive load with anterior-posterior force, rotational torque, or varus-valgus moment. The relative deflections, both compressive and distractive, were measured between the component and the bone. The least deflections occurred with one-piece metal-tray components with one or two posts and with one-piece plastic components with a post on each side. Compartmental components deflected the most.

Metallic intramedullary orthopedic implants generate artifacts that can markedly degrade transaxial CT images. The artifacts, typically seen as starburst streaking, result primarily from reconstructions involving missing projection data. Two approaches are clinically available to reduce the artifacts around orthopedic implants. These are (a) the imaging of implants with lower attenuation coefficients or smaller path lengths (less attenuating objects) and (b) the planar reformatting of image data. The sizing accuracy of these two approaches was quantified using phantoms and the efficacy using cadaveric femoral specimens. Results demonstrated that metal artifacts may be reduced and accurate bony dimensional data obtained.

The cruciate ligaments (and the intercondylar eminence of the tibia) should be removed when the knee is replaced. A mechanically unlinked prosthesis can be designed which will then be capable of restoring "cruciate" stability, i.e., anteroposterior stability of the tibia in the flexed knee. A knee replaced with such a prosthesis will only be stable if the prosthesis is inserted using the correct instruments and technique. Stability depends as much on precise surgical technique as it does on prosthetic design.

A method was developed for describing the flexion-extension motion of the knee joint in a sagittal plane, by employing ciné radiography and then plotting the loci of three points on the femur relative to the tibia. Normal knees displayed similar patterns, the curves were smooth, and flexion-extension curves superimposed. A standard knee outline with standard curves was defined, with which to compare the abnormal and prosthetic knees. Arthritic knee patterns differed significantly from the normals. The curves were irregular and the flexion-extension curves were different. Instability, joint surface irregularity and muscle spasm were thought to be the main causes. The curves for the MacIntosh tibial plateaus were abnormal in a similar way to the arthritics. This may have been due to residual instability and to the replacement of only one bearing surface. The condylar replacement prostheses (the uni-condylar, duo-condylar and Geometric) tended to produce close-to-normal knee patterns, probably due to restoration of a relatively normal geometry, and to replacement of both bearing surfaces. The knees with fixed hinge prostheses (Walldius, Shiers and Guépar) showed abnormalities of motion and of the relative postion of the femur on the tibia. These features would be undesirable for the correct functioning of soft tissues around the knee. The stabilo-condylar hinge, which did not require much bone resection, gave a motion comparable to the condylar replacements.