Eckart Mayr

A prospective randomized assessment of earlier functional recovery in THA patients treated by minimally invasive direct anterior approach: a gait analysis study.

BACKGROUND Total hip replacement using a minimally invasive surgical approach is claimed to enable recovering of motor function more quickly. The purpose of this prospective As per the stylesheet, kindly provide section headings for abstract.and randomized study was to test this claim by evaluating early patient functional outcomes by gait analysis. METHODS Seventeen patients were operated on using a traditional anterolateral approach (AL), 16 using a minimally invasive direct anterior approach (DA). Gait analysis was performed the day before surgery, and at 6 and 12 weeks after surgery. Time-distance and kinematics analyses were performed by a recently proposed anatomically-based gait analysis protocol. A static double-leg stance and five walking trials at self-selected speeds were recorded on a 9-m walkway. FINDINGS At 6 weeks follow-up, but in the DA group only, a statistically significant improvement with respect to preoperative status was observed for the percentage of single support and for the stride time. Between 6- and 12-week follow-up, the DA group showed a significant improvement in cadence, stride time and length, walking speed, hip flexion at foot contact, maximum hip flexion in swing, and hip total range of motion in the sagittal and the coronal planes. Between 6 and 12 weeks, the AL group showed significant improvements in opposite foot contact and step time, and in flexion at foot contact, maximum flexion in swing, and range of flexion at the hip joint. INTERPRETATION Minimally invasive DA patients improved in a larger number of gait parameters than patients receiving the traditional AL approach. The majority of improvements occurred between the 6- and 12-week follow-ups.

The frontal pelvic plane provides a valid reference system for implantation of the acetabular cup: Spatial orientation of the pelvis in different positions

Background The frontal pelvic plane has traditionally served as the reference plane for implantation of the acetabular cup during total hip arthroplasty, with referencing performed with the patient supine on the operating table. During daily activities in an upright position, the frontal pelvic plane changes from a horizontal to a vertical orientation. If this change in orientation is accompanied by a substantial change in pelvic inclination angle, it would mean that the use of the frontal pelvic plane as a reference plane for implantation of the acetabular cup would not be valid for proper alignment of the cup. To evaluate this possibility, we measured the change of inclination of the pelvis from the supine to the standing position. Subjects and methods We evaluated 120 patients, first positioned in a standing position and then supine on a table. Three pelvic landmarks were digitized percutaneously, and the spatial coordinates were calculated with regard to pelvic orientation in the horizontal and the vertical plane. Results We found a mean inclination of 6.7° in the standing position and 5.6° in the supine position. Patients who were more than 60 years of age who did not have coxarthrosis had a greater inclination angle (8.7°) while standing. Pelvic orientation was stable with regard to the supine and standing positions. These results were independent of sex, level of arthrosis, or status after implantation of a total hip replacement. Interpretation The frontal pelvic plane is a valid reference plane for implantation of the acetabular cup.   ▪

Reduced variability in cup positioning: the direct anterior surgical approach using navigation

Background and purpose Correct positioning of the acetabular component is important in total hip arthroplasty (THA). We evaluated the effect of an imageless navigation system on the accuracy of cup positioning using a minimally invasive direct anterior approach. Methods Hip replacements were performed in 44 cadaveric hips (22 cadavers) that were divided randomly into 2 groups. In the study group, THA was performed using an imageless navigation system. In the control group, no navigation system was used. CT scans were taken postoperatively. Using 3D reconstructions, the cup position was determined in relation to the frontal pelvic plane. The goal was to place each cup at 45° of inclination and 20° of anteversion, as recommended by the manufacturer. Results In the navigated group, there was a statistically significantly smaller range of deviation from the target angles of inclination and anteversion relative to the control group. Interpretation We conclude that imageless navigation improves the accuracy of cup placement in minimally invasive THA using the direct anterior approach.

Impaction bone grafting: A LABORATORY COMPARISON OF TWO METHODS

In revision total hip replacement, bone loss can be managed by impacting porous bone chips. In order to guarantee sufficient mechanical strength, the bone chips have to be compacted. The aim of this study was to determine in an in vitro simulation whether the use of a pneumatic hammer leads to higher primary stability than manual impaction. Bone mass characteristics were measured by force and distance variation of a penetrating punch, which was lowered into a plastic cup filled with bone chips. From these measurements bulk density, contact stiffness, impaction hardness and penetration resistance were calculated for different durations of impaction. We found that the pneumatic method reached higher values of impaction hardness, contact stiffness and bulk density suggesting an increase in stability of the implant. No significant differences were found between the two different methods concerning the penetration resistance. The pneumatic method might reduce the risk of fracture in vivo, as force peaks are smaller and applied for a shorter period. Results from manual impaction showed higher variability and depend much on the experience of the surgeon. The pneumatic hammer is a suitable tool to standardise the impaction process.

The effect of fixation and location on the stability of the markers in navigated total hip arthroplasty A CADAVER STUDY

In navigated total hip arthroplasty, the pelvis and the femur are tracked by means of rigid bodies fixed directly to the bones. Exact tracking throughout the procedure requires that the connection between the marker and bone remains stable in terms of translation and rotation. We carried out a cadaver study to compare the intra-operative stability of markers consisting of an anchoring screw with a rotational stabiliser and of pairs of pins and wires of different diameters connected with clamps. These devices were tested at different locations in the femur. Three human cadavers were placed supine on an operating table, with a reference marker positioned in the area of the greater trochanter. K-wires (3.2 mm), Steinman pins (3 and 4 mm), Apex pins (3 and 4 mm), and a standard screw were used as fixation devices. They were positioned medially in the proximal third of the femur, ventrally in the middle third and laterally in the distal portion. In six different positions of the leg, the spatial positions were recorded with a navigation system. Compared with the standard single screw, with the exception of the 3 mm Apex pins, the two-pin systems were associated with less movement of the marker and could be inserted less invasively. With the knee flexed to 90 degrees and the dislocated hip rotated externally until the lower leg was parallel to the table (figure-four position), all the anchoring devices showed substantial deflection of 1.5 degrees to 2.5 degrees . The most secure area for anchoring markers was the lateral aspect of the femur.

Alignment for total knee replacement: a comparison of kinematic axis versus mechanical axis techniques. A cadaver study

PurposeStandard instrumentation tries to reproduce mechanical axes based on mechanical alignment (MA) guides. A kinematic alignment (KA) technique derives its plan from pre-operative MRI-measurements. This matched-pair cadaveric study compared the resulting postoperative alignments.MethodsA prospective series of 12 torsos were acquired for a total of 24 limb specimens including intact pelvises, femoral heads, knees, and ankles.The cadavers received MRI scans to manufacture the kinematic alignment cutting guides. Two investigating surgeons performed total knee arthroplasties on randomly chosen sides using MA instruments. On the contralateral sides, KA cutting guides were used. A navigation system was used to measure final alignment.ResultsThe overall alignment showed no significant differences between the systems. In the MA group the differences between the planned and the final implantation regarding overall limb alignment ranged between 0.2° and 6.2°. In the KA group the differences between the planned and final implantation regarding overall limb alignment ranged between 0.3° and 9.1°. The differences of the deviation from plan for overall limb alignment showed no significant differences between the methods.ConclusionsThe different alignment strategies resulted in variations of the combinations of the three-dimensional component position on the femur and the tibia. However, the legs were aligned within comparable range for both chosen techniques.

Contamination during removal of cement in revision hip arthroplasty

Instruments used in surgery which rotate or vibrate at a high frequency can produce potentially contaminated aerosols. Such tools are in use in cemented hip revision arthroplasties. We aimed to measure the extent of the environmental and body contamination caused by an ultrasound device and a high-speed cutter. On a human cadaver we carried out a complete surgical procedure including draping and simulated blood flow contaminated with Staphylococcus aureus (ATCC 12600). After cemented total hip arthroplasty, we undertook repeated extractions of cement using either an ultrasound device or a high-speed cutter. Surveillance cultures detected any environmental and body contamination of the surgical team. Environmental contamination was present in an area of 6 x 8 m for both devices. The concentration of contamination was lower for the ultrasound device. Both the ultrasound and the high-speed cutter contaminated all members of the surgical team. The devices tested produced aerosols which covered the whole operating theatre and all personnel present during the procedure. In contaminated and infected patients, infectious agents may be present in these aerosols. We therefore recommend the introduction of effective measures to control infection and thorough disinfection of the operating theatre after such procedures.

Environmental and body contamination through aerosols produced by high-speed cutters in lumbar spine surgery.

Study Design. A cadaver study to evaluate contamination in the operating room through the use of a high-speed bone cutter. Objectives. To determine the grade of contamination of animate and inanimate objects through an aerosol intraoperatively, produced by a high-speed cutter during lumbar laminectomy. Summary of Background. In spinal surgery, high-speed cutters are used that produce an aerosol consisting of a mixture of irrigation solution, blood, and tissue debris. Such aerosols can be contaminated with potential pathogens. The surgical personnel and the environment are therefore exposed to a contamination risk. Methods. Laminectomies at three points (L2–L4) were performed on a human cadaver using a high-speed cutting device. The aerosol produced by the irrigation solution was contaminated with Staphylococcus aureus ATCC 12600. To detect the contamination of the environment and of the surgical team, surveillance cultures were used. Results. By air sampling, staphylococci were detected in the operating room at an extension of 5 by 7 m. The surgical team showed extensive face and body contamination with S. aureus. Despite protection by a barrier drape, similar contamination was observed on both the cadaver’s head and the anesthesiologist. Conclusions. The use of high-speed cutters in spinal surgery produces an aerosol that can be contaminated with blood-borne pathogens from infected patients. This aerosol is spread over the whole surgical room and contaminates the room and all personnel present. It is therefore critical to ensure that effective infection control measures are performed, not only by the surgeons but by everyone present in the operating room. The room itself must be sufficiently disinfected after such procedures.

The Efficacy of Using Search Engines in Procuring Information About Orthopaedic Foot and Ankle Problems from the World Wide Web

This study has attempted to demonstrate the feasibility of obtaining information specific to foot and ankle orthopaedics from the World Wide Web (WWW). Six search engines (Lycos, AltaVista, Infoseek, Excite, Webcrawler, and HotBot) were used in scanning the Web for the following key words: “cavus foot,” “diabetic foot,” “hallux valgus,” and “pes equinovarus.” Matches were classified by language, provider, type, and relevance to medical professionals or to patients. Sixty percent (407 sites) of the visited websites contained information intended for use by physicians and other medical professionals; 30% (206 sites) were related to patient information; 10% of the sites were not easily classifiable. Forty-one percent (169 sites) of the websites were commercially oriented homepages that included advertisements.

Correlation between radiographic assessment and quality of life after total knee arthroplasty

The correlation between radiographic and clinical outcome was investigated for total knee arthroplasty. One hundred three total knee arthroplasties in 98 patients were investigated at an average follow-up of 10.8 years (range, 2-17 years). For radiographic evaluation the Radiographic Evaluation System of the Knee Society was used. For assessment of clinical outcome four disease-specific scores, and the Nottingham Health Profile were applied. A significant correlation was found between the extent of radiolucent lines of the tibial component and the Nottingham Health Profile (correlation coefficient: 0.61, p<0.0001). For the disease-specific scores the correlation was low (correlation coefficient: 0.30-0.50). For the prosthetic alignment no significant correlation was found (p<0.05). The current results show that a correlation was found between radiological assessment and several clinical scores. We suggest that a quality-of-life score should be included in the follow-up evaluation of total knee arthroplasty.