An introduction of various spectroscopic methods to identify in vivo metal wear in total knee arthroplasty.

While the industrial community already employs multiple surface analytical techniques to study compositional wearing of various metallic and nonmetallic materials, as yet, these methods have not been widely introduced into the biological community. We report on a novel approach, using the industrial spectroscopic techniques of X-ray photoelectron spectroscopy, micro-Raman spectroscopy, and scanning electron microscopy equipped with energy dispersive spectroscopy, to identify the fine wear particulates and other impurities deposited within the knee-joint following total knee arthroplasty. In this study, synovial fluid was extracted from knee-joints scheduled for revision of total knee arthroplasty. The small debris flake formed by centrifugation of the fluid was analyzed using the spectroscopic techniques mentioned above. These nondestructive techniques were successful in identifying numerous micron and submicron sized metallic particulates that appear to emanate from both the prosthetic bearing (articulating) surfaces and from backside (nonarticulating) surfaces, even when gross wearing of the prosthetic device was not detectable by direct visual inspection intraoperatively. Most interesting is that the ratio of the in vivo metallic debris is approximately the same ratio as that of the manufactured alloy, indicating prosthetic wearing as opposed to chemical dissolution. More importantly, using these spectroscopic techniques to probe both the surface and below the surface of the synovial deposits, we identify an inhomogeneous distribution of the wear debris. This indicates the need to use multiple techniques in order to adequately identify the elemental composition of the prosthetic wear material.

Osteolytic indicators found in total knee arthroplasty synovial fluid aspirates.

Interleukin-1beta and tartrate resistant acid phosphatase concentrations in synovial fluid aspirates were examined to determine if they could be used as indicators of increased synovial inflammation and an osteolytic reaction in patients having total knee arthroplasty. Synovial aspirates were obtained from seven patients with severely osteoarthritic knees that were scheduled for primary total knee arthroplasty and from 20 patients with knees scheduled for total knee arthroplasty revision. Eleven of the revision cases involved titanium alloy prostheses and nine involved cobalt chrome alloy prostheses. The interleukin-1beta and tartrate resistant acid phosphatase concentrations were obtained and compared between the group having primary total knee arthroplasty and the group having revision total knee arthroplasty. The knees having revision surgery had higher concentrations of interleukin-1beta and tartrate resistant acid phosphatase than did the knees having primary total knee arthroplasty. These results indicate a greater inflammatory and osteolytic response in knees having revision surgery. Although the osteoarthritic knees and the knees needing revision surgery in this study are considered to have an inflammatory state, it was only after total knee arthroplasty when particulate wear debris would be present that appreciable concentrations of interleukin-1beta and tartrate resistant acid phosphatase were produced.

In vitro response of human fibroblasts to commercially pure titanium.

The generation of metal particles through surface wear of prosthetic joints has been associated with biological reactions that may lead to prosthetic component loosening. The role of the macrophage in these reactions has been studied extensively, but that of the fibroblast has not. The few fibroblast studies that there have been have shown that particles of several metals, with sizes over a wide range, can promote cytokine release and may cause cell necrosis. The intent of this study was to determine if there are metal particle exposure threshold levels that result in morphological changes and cell necrosis of fibroblasts in peri-articular tissues. Retrieved human fibroblasts (superior medial plica) were cultured in standard fashion and then were exposed to various particle dosages of commercially pure Titanium (cpTi). Cell morphological changes and necrosis were observed to occur when the total mass of the particle dosage exceeded a threshold level. These data imply that these cell responses occur at threshold levels of wear particle exposure.

Accuracy assessment of a technique for contact point determination from planar radiographs.

The purpose of this study was to determine the accuracy, precision and repeatability of a simple radiographic method which might be used in in-vivo determination of joint contact points following total joint replacement (TKA). A model of a TKA was constructed from which the anterior/posterior location of the contact point could be mathematically calculated. A radiograph was taken of the model and two observers repeatedly determined the contact point using a parallel rule. The measured locations were compared to the calculated values. The accuracy and precision of the measurement locations in comparison to the calculated values were 1.6 mm and 0.4 mm, respectively. The mean inter-observer error was 0.2 mm.

Medical and financial aspects of same-day bilateral total knee arthroplasties.

In this retrospective study, we compared forty-five patients who had undergone same-day bilateral total knee arthroplasties with 144 patients who had undergone unilateral total knee arthroplasty procedures. All procedures were performed by a single surgeon using a single prosthetic design between June 1994 to May 1996. The issues studied were the length of hospital stay, hospital charges, units of blood transfused, units of homologous blood transfused, and the rate and type of complications. This study also examined the usage and financial charges of extended care facilities and/or home health care following discharge from the hospital. Results show that, for patients suffering from symptomatic bilateral knee disease, the same-day bilateral total knee procedure is significantly less costly than staged bilateral procedures. The rate and type of complications seen in the same-day bilateral cases were not significantly different from complications seen in unilateral cases.

Quadriceps femoris function during knee extension following total knee arthroplasty.

Electromyographic signals (EMG) from surface electrodes over the vastus medialis, rectus femoris and vastus lateralis were monitored during isometric knee extension for 10 TKA patients and 6 control subjects. No significant side-to-side differences in normalized EMG signals from any of the monitored muscles were found when the left and right legs of the control group were compared or when the operative and the non-operative legs of the patient group were compared. However, both the operative and the non-operative legs in the patient group differed significantly (p < 0.01) in normalized EMG from the control group. This study has shown that a muscle imbalance, possibly leading to patellar tracking problems, does not routinely exist following TKA through a medial parapatellar incision.

Response of human fibroblasts to tantalum and titanium in cell culture.

The loosening of total joint arthroplasties (TKA) with associated osteolysis has been a persistent problem in orthopaedics. Wear debris from prosthetic devices including Titanium (Ti) is involved in this process. Mechanisms for this osteolytic process are unclear. The purpose of this study was to compare the biological response of Ti and Tantalum (Ta) on retrieved human fibroblasts. Fibroblasts were retrieved from human volunteers and cultured using standard techniques. Twenty-five (25) ml culture flasks were seeded with cells and when reaching confluency four concentrations of Ti and Ta were added. Their mean size was less than 3 microns for both metals and gram weights were 0.0048. 0.0096, 0.048, and 0.096 gms. After ten (10) days the cells were fixed, stained and photographed. For both Ti and Ta, the lowest concentration had little effect on the cells, while at the two higher concentrations, nearly all of the cell were killed. Since both of the metals tested are considered to be inert with respect to toxicity, these results would suggest that the observed cell death, seen equally for both metals, was due to the size and concentration of the particles and not to the metals tested. Mechanisms are currently being investigated which include mechanical as well as chemical factors.

A comparison of interleukin-1 beta in human synovial fluid of osteoarthritic and revision total knee arthroplasty.

Interleukin-1 beta levels from synovial aspirates were examined to determine if they can be used as indicators of increased synovial activity and an inflammatory reaction within total knee arthroplasty. Synovial aspirates were obtained from twelve osteoarthritic knees scheduled for total knee arthroplasty and twenty-one knees scheduled for total knee revision. Eleven of the revision cases involved titanium alloy prostheses and ten involved cobalt-chrome prostheses. Using a high sensitivity ELISA test kit, the interleukin-1 beta concentrations were compared. A significant difference in the interleukin-1 beta concentration was found between all three knee groups. The knees scheduled for revision surgery showed higher concentrations of interleukin-1 beta than osteoarthritic knees. While the knees implanted with a titanium prosthesis showed the greatest concentration of interleukin-1 beta, the osteoarthritic knees showed the lowest interleukin-1 beta concentration. Furthermore, significantly greater synovial aspirate volumes were obtained from the revision cases than from the osteoarthritic cases. This increased synovial activity is most likely attributed to the high concentration of the particulate wear debris produced from the prosthesis.

Role of the calcaneal heel pad and polymeric shock absorbers in attenuation of heel strike impact.

The capacity of the calcaneal heel pad, with and without augmentation by a polymeric shock absorbing material (Sorbothane 0050), to attenuate heel strike impulses has been studied using five fresh human cadaveric lower leg specimens. The specimens, instrumented with an accelerometer, were suspended and impacted with a hammer; a steel rod was similarly suspended and impacted. The calcaneal heel pad attenuated the peak accelerations by 80%. Attenuations of up to 93% were achieved by the shock absorbing material when tested against the steel rod; however, when tested in series with the calcaneal heel pad, the reduction in peak acceleration due to the shock absorbing material dropped to 18%. Any evaluation of the effectiveness of shock absorbing shoe materials must take into account their mechanical interaction with the body.

The use of postoperative suction drainage in total hip arthroplasty.

Two hundred eight primary total hip arthroplasties were reviewed to evaluate the effect of closed suction drainage. This review included 45 hips in which closed drains were used and 163 hips in which drains were not used. These two groups were compared for possible differences in wound problems, temperature elevations, changes in Hgb/Hct, and the need for transfusions. There was no statistically significant difference in postoperative temperatures or decrease in Hgb. However, there were four superficial wound infections in the drained group and three superficial wound infections in the non-drained group (P < .025). There were no deep infections in either group. These findings suggest closed suction drainage provides no apparent advantage in uncomplicated primary total hip arthroplasty.

The effect of patient weight on the functional outcome of total knee arthroplasty.

Overweight patients are often considered poor candidates for total knee arthroplasty. For assessment of the validity of this proscription, two-year follow-up data from 109 patients were analyzed. Hospital for Special Surgery Scores were recorded, roentgenograms were inspected for radiolucencies, and isokinetic strength tests were conducted. Surgical time, the presence and severity of radiolucencies, and isokinetic joint strength were found to have statistically significant, positive correlations with patient weight. The Hospital for Special Surgery Score was found to have negative correlations with weight for those patients weighing less than 80 kg, and it was found to have negative correlations with the percentage by which patients were heavier than their ideal weights. However, multiple regression analyses indicated that these correlations were caused by patient gender and not by any independent effect due to weight. From a clinical point of view, the results of this study suggest that orthopedists can expect their overweight total knee patients not to be at a significant postoperative functional disadvantage because of their weight during the initial, two-year postoperative period.

Effect of vacuum mixing on the mechanical properties of antibiotic-impregnated polymethylmethacrylate bone cement.

Polymethylmethacrylate bone cement, containing either no added antibiotic, 0.5 g of Vancomycin, 1.0 g of Vancomycin, or 1.0 g of Tobramycin, was mixed either in air or a vacuum chamber. Following storage in a water bath at 37 degrees C for 48 h, the specimens were tested in four-point bending. The porosity of the specimens was assessed radiographically, and their antibacterial activity was monitored for 21 days. The bending strength of the vacuum mixed specimens containing no antibiotic was 40% greater than that of similar air-mixed specimens. However, there were no significant differences in the bending strength of either the air- or vacuum-mixed specimens when any of the antibiotic dosages were added. The bending modulus of the vacuum-mixed specimens, containing no antibiotic, was significantly greater than the moduli of all the other specimen groups which did not differ from each other. Vacuum mixing reduced the apparent porosity of the specimens fivefold, and while the addition of antibiotic did not effect porosity of the air-mixed specimens, that of the vacuum-mixed specimens was doubled. Although initial rapid decreases were seen, leaching of antibiotic from the cement and antibacterial activity continued through the 21-day monitoring period.

Fracture of a fenestrated metal backing of a tibial knee component. A case report.

The case of a metal-backed tibial component that failed by metal fracture is reported. Fracture occurred through fenestrations in the metal plate surrounding the central metal stem. The fracture followed loss of bony support beneath the medial tibial plateau, which had allowed varus deformity of the replaced joint. A high tibial osteotomy procedure had preceded replacement of the joint.

Comparison of functional outcome of total hip arthroplasties involving four surgical approaches.

One hundred thirty-seven total hip arthroplasty patients had a follow-up evaluation consisting of an orthopaedic physical evaluation, isokinetic strength testing, and collection of demographic and surgical information from medical records. The intraoperative variables of surgical time and blood loss and the functional outcome status of the subjects, as demonstrated by D'Aubigne--Postel ratings and isokinetic strength tests, were compared for various trochanteric management techniques: no osteotomy; complete Charnley-type osteotomy; sharp abductor release; and a wafer technique, in which a wafer of bone was osteotomized from the trochanter to release the abductors. A comparison of the mean values for the variables indicated that the wafer and sharp techniques were superior to the complete and no osteotomy techniques. The wafer technique resulted in statistically significant superior isokinetic strength measured in adduction, flexion, and extension. Surgical time was significantly greater in the complete osteotomy cases and blood loss was least in the wafer cases, although these differences were not significant.

The use of postoperative suction drainage in total knee arthroplasty.

A retrospective review of 299 total knee arthroplasties performed between 1973 and 1983 revealed 170 knees in which postoperative suction drainage was used and 129 knees in which drains were not used. Comparison between these two groups revealed no statistically significant difference in wound problems, postoperative temperatures, or resulting range of motion. However, blood transfusions were given more than twice as often to the patients whose knees were drained (39% compared to 16%, p less than .01). The drained group also had a greater decrease in hemoglobin than the nondrained group (3.1 gm compared to 2.6 gm, p less than .01). In a review of these patients, no advantage was found for the use of postoperative suction drainage in the uncomplicated total knee arthroplasty.

An in vitro simulation study of impulsive force transmission along the lower skeletal extremity.

Several investigators have revealed that a relationship exists between articular cartilage deterioration and the mechanical stress that results from transient impulsive forces created in the lower extremity during gait. This study is an investigation of the transmission of impulse waves through the lower extremity and the effect of knee pathology and prosthetic knee replacement on their transmission. An in vitro experiment is performed using human cadaver specimens that are instrumented with accelerometers. The distal end of the tibia is impacted with a vibration shaker to simulate heel strike. The results indicate that the normal knee joint is able to attenuate 59% of the transient peak force applied to it by the tibia. This attenuation capacity is reduced by knee pathology and decreases further with implantation of a knee prosthesis. The results indicate that abnormalities at the knee may increase the risk of degenerative changes at the ankle, hip and in the spine due to increased transient impulsive forces.

Patellectomy: a clinical study and biomechanical evaluation.

This study presents a long-term follow-up and evaluation of a single technique of patellectomy involving a cruciform repair of the extensor mechanism. The techniques of evaluation, namely: clinical observation, instant center analysis and an acoustical method of cartilage evaluation provide a more thorough and objective basis for clinical study than previously reported. Cruciform repair produced results comparable to conventional methods of surgical repairs. Patellectomized knees function well in people with patellofemoral disease but not in those with panarticular disease. Patellectomy substantially alters normal joint mechanics as evidenced by persistent changes in instant center analysis. Degenerative changes caused by the patellectomy are progressive. In view of newer concepts of the function of the patella in normal joint mechanics and improved designs of total knee arthroplasty, the indications for patellectomy are now more questionable than ever before in the history of orthopedics.

A theoretical analysis of cast wedging with practical applications.

Cast wedging using vector and geometrical analysis demonstrated that the open wedge produces distraction of the fracture, the closing wedge shortening, and that the opening--closing wedge can perfectly correct skeletal deformity. The level of wedging should lie at the axis intersection, i.e., at the intersection of the long axes of the 2 major fracture fragments. An open wedge at the axis intersection is recommended for tibial shaft fractures immobilized with long leg casts; an opening--closing wedge at the axis intersection, for fractures immobilized with "pins and plaster".

An electro-acoustical technique for the detection of knee joint noise.

Distinguishing acoustical signatures of sound emitted by normal and pathological knee joints are picked up using a double microphone-differential amplifier setup. Extraneous background noise is minimized using the principle of "noise cancellation". Two identical sensitive condenser microphones and an F.M. recorder with flat responses in the audio range were used. Preliminary studies covering normal and diseased knee joints showed that their respective waveforms and spectral patterns are unique and proved to be a promising nondestructive diagnostic tool for early detection of knee joint cartilage damage.