Rudi G. Bitsch

Cementing Techniques for Hip Resurfacing Arthroplasty: Development of a Laboratory Model

BACKGROUNDnHip resurfacing is extremely technique-sensitive, yet scientific investigations into cementing techniques are lacking. In this study, we tested open-cell, reticulated, carbon-foam materials in comparison with paired human femoral heads to validate a laboratory cementing model for resurfacing arthroplasty.nnnMETHODSnPaired human femoral heads prepared for resurfacing were compared with thirty and sixty-pore-per-inch fat-filled foam specimens. Two different cementing techniques were analyzed: manual application of high-viscosity cement, and half component-filling with low-viscosity cement. Real-time measurements were made of cement pressure and temperature. Cement penetration areas and depths were quantified.nnnRESULTSnWe found no significant differences between the human femoral heads and the fat-filled thirty-pore-per-inch foam models in all measured variables (pressures at the top, chamfer and outer wall, temperature at the 5-mm and 15-mm subsurface). There was no significant difference in the cement penetration of the human femoral heads and the fat-filled thirty-pore-per-inch foam models. There were a number of significant differences between the human femoral heads and the sixty-pore-per-inch foam models with use of the low-viscosity cement technique. The differences between the cementing techniques were greater than those between the three materials for most of the measurements.nnnCONCLUSIONSnFat-filling (to emulate bone marrow) of lower-density carbon foam more closely simulates the cement penetration resistance and thermal properties of human femoral heads than does the denser (unfilled) material. This model is sensitive to differences in cementing technique.

Reduction of Osteolysis with Use of Marathon Cross-linked Polyethylene: A Concise Follow-up, at a Minimum of Five Years, of a Previous Report*

We previously reported wear data at a minimum of two years following thirty-four total hip replacements with a Marathon cross-linked polyethylene liner and twenty-four replacements with a conventional (gamma-sterilized-in-air) Enduron polyethylene liner. In this current study, with sequential five-year radiographs, wear rates were determined with use of linear regression analysis. The Marathon polyethylene had average wear rates of 15.4 mm(3)/yr and 8.0 mm(3)/million cycles. The Enduron polyethylene had average wear rates of 55.5 mm(3)/yr and 29.9 mm(3)/million cycles. The adjusted volumetric wear rate of the Marathon polyethylene was 73% lower than that of the Enduron polyethylene (p = 0.001). Osteolysis developed in eight of the twenty-four hips with an Enduron liner but was not apparent in any hip with a Marathon liner.

Loosening after acetabular revision: comparison of trabecular metal and reinforcement rings. A systematic review.

The best method of revision acetabular arthroplasty remains unclear. Consequently, we reviewed the literature on the treatment of revision acetabular arthroplasty using revision rings (1541 cases; mean follow-up (FU) 5.7 years) and Trabecular Metal, or TM, implants (1959 cases; mean FU 3.7 years) to determine if a difference with regard to revision failure could be determined. Failure rates of the respective implants were compared statistically using a logistic regression model with adjustment for discrepancies in FU time. In our study, TM shows statistically significant decreased loosening rates relative to revision rings for all grades including severe acetabular defects and pelvic discontinuity. The severe defects appear to benefit the most from TM.

Mueller reinforcement rings in acetabular revision Outcome in 164 hips followed for 2-17 years

Backgroundu2003In revision hip arthroplasty, cages are commonly used for acetabular reconstruction in cases with loss of bone stock. It is important to follow this patient group closely, in order to better understand failure mechanisms and the chance of long-term success. Patients and methodsu2003We followed our first 164 acetabular revisions with the Mueller reinforcement ring (ARR) in 164 patients, with an average follow-up period of 6 (2–17) years. Mean age at surgery was 69 (29–92) years. 39 patients died (39 hips) during follow-up, but only 3 patients (3 hips) were lost to follow-up. Resultsu2003In the observation period, 13 of the hips had to undergo acetabular re-revision for aseptic and septic loosening. Overall survival at 5 years was 95% (CI: 89%–98%) and 90% (CI: 76%–95%) at 8 years using acetabular re-revision or implant removal for all reasons as endpoint. In addition, mechanical and clinical failure was seen in 2 cases. The mean Harris hip score was 70 points, whilst the Merle dAubigné score averaged 7 points. Radiolucent lines according to DeLee and Charnley were observed twice in zone I, 6 times in zone II and 14 times in zone III. Interpretationu2003We found that mid- to long-term survival of the ARR is acceptable. However, failure of the implant due to allograft collapse/resorption or deep infection, and also poor clinical outcome, remain major concerns in acetabular revision arthroplasty. This should be recognized when advising patients.

Are Patients’ Expectations of Hip and Knee Arthroplasty Fulfilled? A Prospective Study of 130 Patients

Total hip arthroplasty (THA) is the most successful procedure in orthopedic and trauma surgery. Patients expectations of joint replacement surgery prior to and after the procedure are often discounted. This study investigated the expectations of patients before and 3 years after THA or total knee arthroplasty (TKA). A total of 130 patients (70 hips, 60 knees) received a modified FFbH-OA survey with 6 additional questions concerning patients expectations before and 3 years after joint replacement surgery. The overall response rate was 78.8% (101 patients). Patients who underwent THA had a mean age of 63.7 years, and those who underwent TKA had a mean age of 67.4 years.Sixty-three percent of all respondents reported that their expectations had been fulfilled or exceeded 3 years postoperatively (THA, 65%; TKA, 61%). A high negative correlation in the THA group could be seen between patients expectations and clinical scores: the lower the clinical score, the less the patients expectations had been fulfilled. A statistically significant increase of change in personal relationships was found, as well as a statistically significant decrease in worries and less complications than had been expected before joint replacement.Thirty-seven percent of all respondents felt that their expectations regarding joint replacement had not been fulfilled. Looking at the results of this study, the 37% of patients whose expectations had not been fulfilled did not exhibit a lower postoperative functioning than those who were satisfied.

Effects of Vascular Perfusion on Coagulation Size in Radiofrequency Ablation of Ex Vivo Perfused Bovine Livers

Objectives:A standardized perfused ex vivo bovine liver model was used to evaluate the effect of organ perfusion on coagulation size and energy deposition during radiofrequency ablation (RFA) procedures. Materials and Methods:Bovine livers were perfused in a tank after rinsing the prepared liver vessels with anticoagulants. Tyrodes solution, oxygenated and heated to 36.5°C, was used as perfusion medium. A flow and pressure controlled pump regulated Portal vein circulation; a dialysis machine provided pulsatile arterial circulation. Impedance-guided radiofrequency ablations were performed with 4-cm LeVeen electrodes with and without underlying liver perfusion. Two-dimensional diameters (Dv, Dh) of each ablation area were measured after dissecting the livers. Results:In 4 bovine livers weighing 8.85 ± 0.83 kg per organ (min, 7.7 kg; max, 9.7 kg) altogether 40 RF ablations were performed. A total of 20 ablations were generated with underlying liver perfusion (group 1) and 20 ablations with no liver perfusion (group 2). In group 1, Dv was 28.4 ± 5.3 mm, Dh 38.6 ± 7.8 mm, and energy deposition 36.9 ± 18.0 kJ. The 20 ablation areas generated without liver perfusion displayed statistically significant differences, with Dv being 35.7 ± 6.5 mm (P = 0.001), Dh 49.5 ± 9.4 mm (P = 0.001), and energy deposition 25.5 ± 13.0 kJ (P = 0.018). Conclusion:The model reproduced the cooling effect of perfused tissue during RFA. The ablation areas produced under perfusion conditions had smaller diameters despite longer exposure times and higher energy deposition.

Primary rotational stability of cylindrical and conical revision hip stems as a function of femoral bone defects: An in vitro comparison

Bone stock losses in cementless femoral stem revisions compromise a stable fixation. The surgeon has to rely on his wealth of experience in deciding which stem shape to use. The aim of our study was to compare the primary rotational stability of cylindrical and conical revision hip stems subjected to femoral defects. Four current prostheses (two cylindrical, two conical) were implanted into four synthetic femora. Micro-motion was measured under torque application and femoral neck osteotomy and segmental AAOS Type I and III defects were simulated. The relative movements of all prostheses were significantly influenced by the extent of bone loss (p<0.01). Major differences were seen in fixation behavior (p<0.01). The main fixation area of conical stems is within the distal femoral isthmus, whereas cylindrical implants are dependent on proximal bone stock. In our study, cylindrical stems are advantageous for minor defects because they provide a proximal fixation. In cases of extensive substance loss, the conical implants showed lesser relative movements. These findings should be taken into account for clinical decisions.

The effect of bone lavage on femoral cement penetration and interface temperature during Oxford unicompartmental knee arthroplasty with cement.

BACKGROUNDnAseptic loosening is the most common cause for revision unicompartmental knee arthroplasty and is associated with failure of the bone-cement or cement-implant interface. The purpose of the present study was to analyze different bone lavage techniques for the bone-cement and cement-implant interfaces of the femoral component and to study the effect of these techniques on cement penetration and on interface temperature.nnnMETHODSnIn an experimental cadaver study, Oxford unicompartmental knee arthroplasty was performed in twenty-four matched-paired knees to study the effect of pulsed lavage compared with syringe lavage on femoral cement penetration and interface temperature. Interface temperature, cement penetration pressure, and ligament tension forces were measured continuously during the procedure, and cement penetration was determined by performing sagittal bone cuts.nnnRESULTSnCleansing the femoral bone stock with use of pulsed lavage (Group B) led to increased femoral cement penetration (mean, 1428 mm²; 95% confidence interval, 1348 to 1508 mm²) compared with syringe lavage (Group A) (mean, 1128 mm²; 95% confidence interval, 1038 to 1219 mm²) (p < 0.001). Interface temperature was higher in Group B (mean 22.6°C; 95% confidence interval, 20.5°C to 24.1°C) than in Group A (mean, 21.0°C; 95% confidence interval, 19.4°C to 23.0°C) (p = 0.028), but temperatures never reached critical values for thermal damage to the bone.nnnCONCLUSIONSnPulsed lavage leads to an increased femoral cement penetration without the risk of heat necrosis at the bone-cement interface.

Femoral fixation pattern in cemented Oxford unicompartmental knee arthroplasty — An experimental cadaver study

Femoral component loosening is a rare but serious complication in cemented Oxford unicompartmental knee arthroplasty (OUKA). In a cadaver study, OUKA was performed in 24 knees to evaluate the femoral fixation pattern. Due to the geometry of bone and implant, three different zones were identified. Complete cement mantles and good interdigitation were found in the spherical part of the implant (zone 1) and around the peg (zone 3), which implies that these are most important for implant fixation. The posterior plane facet (zone 2) is the weak point of the interface due to incompleteness of the cement mantle and a lack of interdigitation. This study suggests that the cancellous bone in zone 2 and the drill holes in sclerotic bone areas should be filled with cement and pressurised prior to component seating.

Cementing Techniques for Hip Resurfacing Arthroplasty: In Vitro Study of Pressure and Temperature

Cementing irregularities have been associated with femoral failures of resurfacing arthroplasties in retrieval studies. We used an in vitro model to measure pressure, temperatures, and cement penetration as a function of 6 different cementing techniques. Filling the component with cement can lead to overpenetration or increase the resistance to component seating with resultant polar cement mass. Both conditions result in high and long-lasting cement pressures, cement defects, as well as peak temperatures higher than 50°C. Manual application of cement provides complete penetration of the available fixation area with the lowest cement pressures, the smallest total cement mass, and a peak temperature of 36.0°C ± 4.1°C. Application of the principles elucidated by this study may reduce the risk of cement overpenetration and incomplete seating.