Herbert Franzén

Movement pattern of the Exeter femoral stem: A radiostereometric analysis of 22 primary hip arthroplasties followed for 5 years

Background It is difficult to assess the orientation of the acetabular component on routine radiographs. We present a method for determining the spatial orientation of the acetabular component after total hip arthroplasty (THA) using computed tomography.Patients and methods Two CT-scans, 10 min apart, were obtained from each of 10 patients after THA. Using locally developed software, two independent examiners measured the orientation of the acetabular component in relation to the pelvis. The measurements were repeated after one week. To be independent of the patient position during scanning, the method involved two steps. Firstly, a 3D volumetric image of the pelvis was brought into a standard pelvic orientation, then the orientation of the acetabular component was measured. The orientation of the acetabular component was expressed as operative anteversion and inclination relative to an internal pelvic reference coordinate system. To evaluate precision, we compared measurements across pairs of CT volumes between observers and trials.Results Mean absolute interobserver angle error was 2.3° for anteversion (range 0–6.6°), and 1.1° for inclination (range 0–4.6°). For interobserver measurements, the precision, defined as one standard deviation, was 2.9° for anteversion, and 1.5° for inclination. A Students t-test showed that the overall differences between the examiners, trials, and cases were not significant. Data were normally distributed and were not dependent on examiner or trial.Interpretation We conclude that the implant angles of the acetabular component in relation to the pelvis could be detected repeatedly using CT, independently of patient positioning.

Cement interface temperature in hip arthroplasty

The temperature was measured using thermocouples in the bone-cement interface during cement curing in 30 total hip replacement operations. A modern technique was used, including lavage and precooled vacuum-mixed cement. The mean maximum temperature in the acetabulum was 43 (38-52) degrees C and in the femur 40 (29-56) degrees C. The use of a precooled femoral prosthesis did not affect the peak temperature.

Early complications after one hundred and forty-four consecutive hip revisions with impacted morselized allograft bone and cement

Background: The use of impacted morselized allograft bone and cement in hip revision arthroplasty has been popular, but studies that specifically address intraoperative and postoperative complications have been scarce.Methods: All complications that occurred during, and within the first year after, 144 consecutive hip revision arthroplasties (108 stems and 130 sockets) performed with impacted morselized allograft bone and cement were recorded. Clinical and radiographic follow-up evaluation was performed at three months and at one year after surgery for all patients except eight (seven who had died of causes unrelated to the hip surgery and one who had sustained a stroke). Of these eight patients, seven had a six-week and/or three-month follow-up evaluation.Results: Thirty-nine femoral fractures occurred in thirty-seven hips; twenty-nine of the fractures occurred during surgery and ten, within five months after surgery. Of the intraoperative femoral fractures, twelve were proximal, nine were diaphyseal, and eight involved the greater trochanter. Of the postoperative femoral fractures, one was proximal and nine were diaphyseal. Other intraoperative complications were the creation of a femoral cortical window in seven hips and incidental perforation of the femoral cortex in fourteen. Multivariate analysis showed the risk factors for femoral fracture during or after revision to be concomitant disease, greater deficiency of the femoral bone stock, and an intraoperative femoral window or perforation. Other complications included dislocation of the femoral head in nine hips, deep infection in one hip, persistence of preoperative deep infection in one hip, and superficial wound infection requiring wound débridement in two hips.Conclusions: We found the complication rate to be high after hip revision arthroplasty performed with impacted morselized allograft bone and cement. The most serious complication was postoperative diaphyseal femoral fracture.

Measurement accuracy in acetabular cup migration: A comparison of four radiologic methods versus Roentgen stereophotogrammetric analysis☆

Four different methods of radiologic evaluation of the acetabular component migration following total hip arthroplasty have been compared with roentgen stereophotogrammetry, a proven highly accurate method for studying early migration. In the Sutherland and Wetherell method the implants position is measured with a pencil and a ruler from an ordinary pelvis radiograph. New reference lines of the Wetherell method are thought to be more accurate. The Sulzer and EBRA methods are computerized. In the Sulzer method prominent bone markers are digitized and used as reference points. In the EBRA method a system of tangents on prominent pelvis structure is digitized and used to detect radiographs with similar projection. The implants position is calculated as the mean position of similar radiographs. The Sutherland, Wetherell, and Sulzer methods had almost the same accuracy, whereas the EBRA method was more accurate and could be used for pro- and retrospective studies in a large number of patients.

Early migration of femoral components revised with impacted cancellous allografts and cement : a preliminary report of five patients

We report the preliminary findings of the use of roentgen stereophotogrammetric analysis to evaluate the early migration of five femoral components after revision for mechanical loosening using impacted cancellous allograft and cement. All hips were examined at one week, four to six months and one year after surgery. All the components subsided by 0.4 to 4.9 mm during the first year. In four hips the prosthetic head was displaced 1.1 to 6.9 mm posteriorly. Fixation of the femoral components was less secure than after primary arthroplasty but the incidence and magnitude of early migration were similar to those after revision with cement alone.

Is there any difference between vacuum mixing systems in reducing bone cement porosity

Six vacuum mixing systems, Cemvac, Merck, Mitvac, Optivac, Osteobond, and Stryker, were tested using prechilled Palacos R bone cement to investigate the reduction of porosity compared to mixing at atmospheric pressure. In addition the Optivac, Osteobond, and Stryker were tested using Simplex P bone cement to find out if they were effective in reducing the porosity of a middle viscosity bone cement. All vacuum mixing systems reduced the number of macropores (> 1 mm) and micropores (0.1 mm < voids < 1 mm) and increased the density of both Palacos R and Simplex P. But only the Optivac, Stryker, and Merck systems reduced the area percentage of macropores with more than 50% compared to the control. When using Simplex P bone cement, all three mixing systems tested reduced the numbers and the area percentage of macropores compared to the control. The results show that vacuum mixing is effective in reducing the porosity in both a high viscosity cement such as Palacos R and a middle viscosity cement such as Simplex P. Not all systems tested were effective in reducing the number and size of large voids.

Secondary total hip replacement after fractures of the femoral neck

We studied the rate of revision in 84 consecutive total hip replacements performed for failed osteosynthesis of femoral neck fractures and compared it with that for primary arthroplasty for osteoarthritis. The age and sex adjusted risk of prosthetic failure was 2.5 times higher after failure of fixation, but all the excess risk was in patients over 70 years of age. There were radiographic signs of loosening of the femoral component at five to 12 years after secondary arthroplasty in six of 33 survivors. In general, the results of secondary replacement were no worse than those obtained after primary arthroplasty for femoral neck fracture. We consider that internal fixation should be the primary procedure: total hip replacement is a safe secondary procedure when osteosynthesis fails.

Combined survivorship and multivariate analyses of revisions in 799 hip prostheses. A 10- to 20-year review of mechanical loosening

From 1970 to 1980 cemented metal-on-plastic total hip replacement was performed on 799 hips with primary osteoarthritis using one surgical technique. At the 10- to 20-year follow-up there had been 97 revisions for mechanical loosening. Univariate survivorship analysis showed that an increased risk of revision was associated with male gender, young age at primary THR, the Brunswik and Lubinus snap-fit prostheses with large femoral heads (as compared with the Charnley prosthesis), and varying experience of the surgeon. Multivariate statistical analysis showed a three-fold increased risk of revision for men (p < 0.0001), an increase in relative risk of 1.8 per 10 years younger at surgery (p < 0.0001), a fivefold increase in risk for the Brunswik prosthesis (p < 0.0001) and a twofold increase for the Lubinus prosthesis (p = 0.0067). Inexperience of the surgeon, however, was not validated as a risk factor. The study shows that the true risk factors for revision can be identified accurately by combining univariate survivorship and multivariate statistical analyses.

Results of hip revision using the Exeter stem, impacted allograft bone, and cement

The Exeter stem and impacted, morselized allograft bone and cement were used in the revisions of 18 consecutive femoral components (17 patients). The primary arthroplasty had been done because of osteoarthritis. All of the femoral components were revised for the first time because of aseptic loosening. The migration pattern of the Exeter stem after revision was studied using roentgen stereophotogrammetric analysis. At 2 years after surgery, all 18 femoral stems had migrated in the distal direction (average, 2.5 mm). In addition, seven of the stems had migrated in the medial direction (average, 1.3 mm), and two stems had migrated in the lateral direction (0.5 mm and 1 mm, respectively). Sixteen of the femoral stems also had migrated in the posterior direction (average, 2.9 mm), but none migrated in the anterior direction. The migration rate decreased gradually with time during the followup. Six femoral stems continued to migrate between 1.5 and 2 years after surgery. In patients with major femoral bone deficiency at the time of hip revision, the use of impacted morselized allograft bone and cement yielded an initial fixation similar to that obtained in conventionally cemented revisions. Pain had improved in all patients at the 2-year followup.

Early loosening of femoral components after cemented revision. A roentgen stereophotogrammetric study

Roentgen stereophotogrammetric analysis was used to measure the migration of 24 cemented femoral components implanted during revision for mechanical loosening. All hips were examined one week, four months and one year after surgery; 14 hips were also examined after two years. Twenty-one components subsided 0.2 to 5.5 mm during the observation period; in 17 of these, subsidence occurred within four months of surgery. In 16 hips the prosthetic head was displaced 0.7 to 11.2 mm posteriorly. The fixation of the femoral components was less secure than after primary arthroplasty, especially in cases of femoral canal enlargement, when a standard-sized rather than a thick-stemmed prosthesis had been used, and in cases of inadequate cement filling.