Thomas Ilchmann

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.

Measurement accuracy in acetabular cup wear. Three retrospective methods compared with Roentgen stereophotogrammetry.

The accuracy of three methods (the simple and noncomputerized Scheier-Sandel and Charnley-Duo methods and the computerized Ein Bild Roentgen Analyse [EBRA] method) for retrospective wear measurements of the acetabular cup from standard pelvis radiographs was studied. Measurements on 13 hip prostheses were compared with those obtained by roentgen stereophotogrammetry analysis. The Scheier-Sandel method had the lowest accuracy and the EBRA method had the best accuracy. The Charnley-Duo method was almost as good when starting analysis 3 months after surgery and is easier to use. The EBRA method is useful for accurate measurements on a small number of patients; the Charnley-Duo method is recommended for clinical wear studies on a larger number of patients.

Non-operative treatment versus tension-band osteosynthesis in three- and four-part proximal humeral fractures : A retrospective study of 34 fractures from two different trauma centers

Summary.Thirty-four patients with three- and four-part proximal humeral fractures from two different trauma centres were studied retrospectively. Sixteen were treated without osteosynthesis and compared with 18 patients treated with tension-band fixation. Fracture classification and clinical examination were made by the same persons in both groups. Most of the three-part fractures healed with good pain relief and good function in daily life but often with a loss of motion. Four-part fractures often led to pain, loss of motion and of function. Conservative treatment seemed superior to tension-band fixation for three-part fractures. Four-part fractures healed with better function and range of motion after tension-band fixation.Résumé.Trente-quatre patients présentant une fracture à trois ou quatre fragments de l’extrémité proximale de l’humerus ont été examinés rétrospectivement. Seize d’entre eux avaient été traités sans ostéosynthèse et comparés avec dix-huit patients stabilisée par haubanage. La classification des fractures ainsi que l’examen clinique des deux groupes ont été effectués par les mêmes personnes. Le plus grand nombre des fractures à trois fragments ont guéri avec une bonne disparition des douleurs, une bonne fonction dans la vie quotidienne mais avec une perte de mobilité. Les fractures à quatre fragments présentent des séquelles fréquentes telles que douleur et perte de fonction et de mobilité. Un traitement non stabilisateur semble supérieur à l’ostéosynthèse par haubanage pour les fractures à trois fragments. Les fractures à quatre fragments ont guéri avec une meilleure fonction et une meilleure mobilité lorsqu’elles ont été traitées par ostéosynthèse.

Polyethylene wear in Scanhip® arthroplasty with a 22 or 32 mm head:62 matched patients followed for 7-9 years

We measured radiographic polyethylene wear in patients with Scanhip arthroplasty and no clinical or radiographic signs of loosening. The patients were divided into 2 groups according to head sizes. 32 patients (33 hips) had an implant with a 22 mm and 30 patients (34 hips) with a 32 mm head. They were followed for 7-9 years. The groups were matched for diagnosis, sex, weight, age, and time of follow-up. The mean linear wear with a 22 mm head was 1.1 mm and with a 32 mm head 1.5 mm (p 0.004), which corresponds to a yearly wear rate of 0.15 mm and 0.18 mm, respectively. The mean difference in volumetric wear was greater, 420 mm3, as compared to 1239 mm3.

Migration and wear of long-term successful Charnley total hip replacements

We analysed in-vivo migration and wear over a long period of all-polyethylene acetabular cups which had not been affected by mechanical loosening. The selection criteria of regular radiological follow-up, good clinical outcome (Charnley score of 5 or 6), continued walking without crutches and no radiological signs of loosening of the acetabular cups were fulfilled by 25 Charnley total hip arthroplasties. Mean migration, measured by the Nunn method, was 0.6 mm in the medial and 0.2 mm in the cranial direction. The mean yearly rate of wear was 0.05 mm and 0.04 mm, with six and two cups having no detectable wear, as measured by the Livermore and Charnley-Cupic methods, respectively. The maximal detected wear was 3.7 mm. There were no changes in the rate of wear with time. Computerised Ein Bild Röntgen Analyse (single-image radiological analysis) measurements of 20 hips indicated plastic deformation of the cups. We conclude that long-term successful cups do not migrate and have a very low rate of wear which was not affected by ageing of the polyethylene. There was no evidence that polyethylene wear alone caused mechanical loosening of the cup but high rates of wear seem to have an adverse prognostic value in terms of the long-term survival of the prosthesis.

EBRA improves the accuracy of radiographic analysis of acetabular cup migration

EBRA (Ein Bild Röntgen Analyse) is a new computerized method measuring migration and wear of the acetabular cup, suggested to improve measurement accuracy. We evaluated possible errors of measurement and compared EBRA with standard methods. 1. We did repeated measurements on a single radiograph using the same reference lines. The reliability of the input procedure with standard measurements was significantly better than repeated digitization with EBRA. 2. In a more clinical test, a group of 10 patients was studied. 5 radiographs were taken of the same patient on the same day. EBRA improved the reliability of repeated radiographic examination significantly for migration measurements in the vertical direction. 3. To assess the inter- and intraobserver variations, repeated measurements were performed on the clinical series of pelvic radiographs of 10 patients. EBRA was significantly better than standard methods. With EBRA, errors of wear and migration measurements could be reduced, as compared to standard methods. The major improvement with EBRA was found for migration measurements in the vertical direction.

Standard transgluteal versus minimal invasive anterior approach in hip arthroplasty: a prospective, consecutive cohort study

A minimally invasive anterior approach (MIS) was compared to a standard lateral approach in primary total hip arthroplasty. Clinical and radiological outcomes were analyzed 6 weeks, 12 weeks, one year and two years after surgery. The duration of surgery was longer, mobility one week after surgery was better and time of hospitalization was shorter for minimally invasive-treated patients. They had less pain during movement, limping, better Harris Hip Score and satisfaction after 6 weeks, which remained after 12 weeks and 1 year, but not after two years. There were two deep infections in the MIS group. Radiological results were not affected. The infections might be a point of concern, but there were no other disadvantages of the MIS approach. In fact, early rehabilitation was facilitated and clinical results were improved. Our results encourage the continuous use of the MIS anterior approach instead of the lateral approach.

Fixation and loosening of the cemented Müller straight stem: A LONG-TERM CLINICAL AND RADIOLOGICAL REVIEW

The original forged Müller straight stem (CoNiCr) has shown excellent ten- to 15-year results. We undertook a long-term survival analysis with special emphasis on radiological changes within a 20-year period of follow-up. In all, 165 primary total hip replacements, undertaken between July 1984 and June 1987 were followed prospectively. Clinical follow-up included a standardised clinical examination, and radiological assessment was based on a standardised anteroposterior radiograph of the pelvis, which was studied for the presence of osteolysis, debonding and cortical atrophy. Survival of the stem with revision for any reason was 81% (95% confidence interval (CI), 76 to 86) at 20 years and for aseptic loosening 87% (95% CI, 82 to 90). At the 20-year follow-up, 15 of the surviving 36 stems showed no radiological changes. Debonding (p = 0.005), osteolysis (p = 0.003) and linear polyethylene wear (p = 0.016) were associated with aseptic loosening, whereas cortical atrophy was not associated with failure (p = 0.008). The 20-year results of the Müller straight stem are comparable to those of other successful cemented systems with similar follow-up. Radiological changes are frequently observed, but with a low incidence of progression, and rarely result in revision. Cortical atrophy appears to be an effect of ageing and not a sign of loosening of the femoral component.

Risk factors for aseptic loosening of Müller-type straight stems: A registry-based analysis of 828 consecutive cases with a minimum follow-up of 16 years

Background and purpose Even small differences in design variables for the femoral stem may influence the outcome of a hip arthroplasty. We performed a risk factor analysis for aseptic loosening of 4 different versions of cemented Müller-type straight stems with special emphasis on design modifications (2 shapes, MSS or SL, and 2 materials, CoNiCrMo (Co) or Ti-6Al-7Nb (Ti)). Methods We investigated 828 total hip replacements, which were followed prospectively in our in-house register. All stems were operated in the same setup, using Sulfix-6 bone cement and a second-generation cementing technique. Demographic and design-specific risk factors were analyzed using an adjusted Cox regression model. Results The 4 versions showed marked differences in 15-year stem survival with aseptic loosening as the endpoint: 94% (95% CI: 89–99) for MSS Co, 83% (CI: 75–91) for SL Co, 81% (CI: 76–87) for MSS Ti and 63% (CI: 56–71) for SL Ti. Cox regression analysis showed a relative risk (RR) for aseptic loosening of 3 (CI: 2–5) for stems made of Ti and of 2 (CI: 1–2) for the SL design. The RR for aseptic stem loosening increased to 8 (CI: 4–15) when comparing the most and the least successful designs (MSS Co and SL Ti). Interpretation Cemented Müller-type straight stems should be MSS-shaped and made of a material with high flexural strength (e.g. cobalt-chrome). The surface finish should be polished (Ra < 0.4 µm). These technical aspects combined with modern cementing techniques would improve the survival of Müller-type straight stems. This may be true for all types of cemented stems.

Femoral Subsidence Assessment After Hip Replacement An Experimental Study

Background: In an experimental set up information is to be gained on the error of measurement for subsidence assessment of the stem after hip replacement. Methods: Subsidence was measured with a pencil and ruler for four different reference lines and with the computerized EBRA-FCA method. Hip flexion, rotation and abduction were simulated in a standardized way. In a second experimental set up, subsidence was simulated in defined steps. Results: In the tilt study, the maximum error of measurement was 7 mm with standard methods and 1.7 mm with the EBRA-FCA method. In the subsidence study, there was a maximum error of measurement of 1.9 mm with the standard methods. With EBRA-FCA, the maximum error of measurement was 0.2 mm when taking all radiographs into account. Conclusions: The main error of subsidence measurement is caused by tilt of the femur for standard methods and partly can be reduced by EBRA-FCA. EBRA-FCA is more reliable than standard methods but might underestimate the actual subsidence in a clinical situation.