Mark W. Kovacik

Isokinetic lifting strength and occupational injury : a prospective study

One hundred seventy–one nurses had their back strength evaluated on an isokinetic lifting device and filled out an epidemiologic questionnaire. They were then followed prospectively for 2 years to determine the incidence of job–related low–back injuries. The data were analyzed to determine if the injury incidence correlated with any of the strength or epidemiologic variables collected during the original evaluation. Average peak force measured during the isokinetic lift was 63.8 kg + 13.6 kg at a lift speed of 30.5 cm/sec and 59.1 kg + 14.9 kg at a lift speed of 45.7 cm/sec. Sixteen nurses reported an occurrence of job–related low–back pain or injury during the 2–year prospective period. Discriminate statistical techniques showed that none of the strength or epidemiologic variables correlated with the incidence of pain or injury or explained significant amounts of variance when the variables were regressed on strength or work calculated from the lift force/lift height data. It was concluded that in this high risk population, in which loads are heavy and lifting postures are variable, the use of low–back strength or prior history of pain or injury are poor predictors as to subsequent low–back pain or injury.

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.

Osteolytic indicators found in total knee arthroplasty synovial fluid aspirates.

Interleukin-1β 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-1β 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-1β 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-1β 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.

Diminished Suture Strength After Robotic Needle Driver Manipulation

Robot-assisted minimally invasive surgery has become a routine surgical option for the treatment of prostate cancer. Despite its technical advancements, the da Vinci(®) Surgical System still lacks haptic feedback to the surgeon, resulting in a maximally applied compressive force by the robotic needle driver during every grasping maneuver. Without this perceptional sense of touch and grip control, repetitive robotic needle driver manipulation may unknowingly lead to irreparable damage to fine sutures used during delicate anastomotic repairs. For robotic prostatectomy, any such loss of integrity can potentially lead to premature breakdown of the urethrovesical anastomosis and urine extravasation, especially important for a less-than-perfectly fashioned anastomotic repair. Although it has already been established that overhandling of sutures using handheld laparoscopic instruments can lead to reduced suture strength, it has not been established to what extent this may occur after robotic surgical procedures. We present analytical data and analyses concerning the failure strength of fine sutures commonly used for urethrovesical anastomotic repair during robotic prostatectomy, after repetitive robotic needle driver manipulation. When compared with noncompromised monofilament suture controls, the average maximal failure force after repetitive robotic manipulation was significantly reduced by 35% (p < 0.0001). Similarly, the average maximal failure force of braided sutures was significantly reduced after repetitive robotic manipulation by 3% (p = 0.009). This work demonstrates that significant reductions in monofilament and braided suture strength integrity can occur after customary repetitive manipulation by robotic needle drivers in an ex vivo model, with further research warranted in the in vivo setting.

A Method for the Consistent Creation and Quantitative Testing of Postoperative Pelvic Adhesions in a Porcine Model

Introduction: The assessment of methods for the prevention of postoperative pelvic adhesions is hampered by the lack of a quantifiable adhesion measurement technique. Currently available methods for adhesion model assessment rely on qualitative grading scales; a quantitative method would have many attendant benefits, including standardized reporting. Methods: A technique was developed to generate consistent and significant adhesions in a swine model that are suitable for quantitative assessment using a Material Testing System (MTS) machine platform. In this method, the uterine horns are cannulated and then attached to the pelvic sidewall using loose silk sutures. The underlying sidewall and adjacent uterine serosa are injured with electrocautery. Following a two-week survival the entire complex of uterine horn and sidewall are excised en bloc and prepared for MTS testing. Results: Extrication of the adhesion, as measured by the MTS platform, generates a quantitative assessment of adhesion strength that can be scaled and analyzed to produce several continuous variable descriptions. Discussion: This technique represents a novel quantitative method for adhesion assessment in an animal model. This quantitative technique may then be applied to accurately assess a range of adhesion prevention techniques, producing results which can be standardized for comparison.

Cell culture response of synovial fibroblasts to prosthetic metal particles

The purpose of this study was to examine the response of the rabbit fibroblasts to varying concentrations of titanium and cobalt-chrome particles. In the five experiments that were carried out, the results were nearly identical. Where the particle concentrations were 1 or 2 particles per cell of Co-Cr or CPTi, there was little or no effect on the cells. This held for cells growing with the metals as well as when the metals were added at cell confluency. When the particle concentrations were 10 or 20 particles per cell of Co-Cr or CPTi, all or nearly all of the cells were killed. This also held for cells growing with the metals as well as when the metals were added at cell confluency. Both Co-Cr and CPTi were equally as lethal in killing the fibroblasts at the concentrations outlined above in both of the experimental designs. Little attention has been paid to the possible role of the fibroblast, and little is known concerning the response in the presence of wear debris particles outlined above in both of the experimental designs.

Interleukin-1/spl beta/ concentration in total knee arthroplasty

Interleukin-1/spl 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 nine knees scheduled for total knee arthroplasty and eleven knees scheduled for total knee revision. Using a high sensitivity ELISA test kit, the interleukin-1/spl beta/ concentrations were compared. A significant difference was found between the two knee groups. The knees scheduled for revision showed a higher concentration of interleukin-1/spl beta/. Also, the knees scheduled for revision had a significantly higher volume of synovial fluid. This increased synovial activity in the revision knee group is most likely attributed to the high concentration of the particulate wear debris produced from the prosthesis.