Guido Saxler

The accuracy of free-hand cup positioning - a CT based measurement of cup placement in 105 total hip arthroplasties

We studied 105 patients who received a total hip arthroplasty between June 1985 and August 2001 using freehand positioning of the acetabular cup. Using pelvic CT scan and the hip-plan module of SurgiGATE-System (Medivision, Oberdorf, Switzerland), we measured the angles of inclination and anteversion of the cup. Mean inclination angle was 45.8°±10.1° (range: 23.0–71.5°) and mean anteversion angle was 27.3°±15.0° (range: −23.5° to 59.0°). We compared the results to the “safe” position as defined by Lewinnek et al. and found that only 27/105 cups were implanted within the limits of the safe position. We conclude that a safe position as defined by Lewinnek et al. [13] was only achieved in a minority of the cups that were implanted freehand.RésuméNous avons étudié 105 malades qui ont eu une Arthroplastie Totale de la Hanche entre juin 1985 et août 2001 avec positionnement manuel de la cupule acétabulaire. Utilisant une tomodensitométrie pelvienne et le module de hanche de SurgiGATE© - System (Medivision, Oberdorf, Suisse) nous avons mesuré les angles d’inclination et d’antéversion de la cupule. L’angle moyen d’inclination était 45.8°±10.1° (gamme: 23.0° à 71.5°) et l’angle moyen d’antéversion était 27.3°±15.0° (gamme: -23.5° à 59.0°). Nous avons comparé les résultats à l’orientation de sécurité définie par Lewinnek et al. et nous avons trouvé que seulement 27/105 cupules ont été implantées dans les limites de l’orientation correctes. Nous concluons qu’une orientation de sécurité, comme défini par Lewinnek et al. [13] n’a été obtenue que dans une minorité des cupules implantées manuellement.

The Long-term Clinical Sequelae of Incidental Durotomy in Lumbar Disc Surgery

Study Design. A retrospective, long-term follow-up study. Objectives. To find out whether incidental durotomy in lumbar disc surgery is associated with long-term sequelae. Summary of Background Data. Incidental durotomy is a frequent complication during spinal surgery. Little is known about the clinical long-term outcome. Methods. The study population comprised 1,280 patients who underwent standard discectomy of a lumbar disc herniation. A total of 41 patients with incidental durotomies (Group A) were compared with a control group (n = 41) (Group B) matched for age, sex, spinal level, and duration of follow-up. After a mean follow-up period of 10.2 years (Group A) or 10.3 years (Group B), the patients reported complaints, headache, and low back or leg pain. The patients’ activity was assessed by means of a questionnaire concerning hindrance in daily activities, the Tegner score for general activities in daily life, and the Hannover Functional Ability Questionnaire for Measuring Back Pain-Related Functional Limitations (FFbH–R). The frequency of reoperation and the intake of analgesics were included. Furthermore, the patients’ inability to work, change of profession, and retirement were registered. Results. Patients with incidental durotomy had a poorer outcome after surgery. The Tegner score was significantly decreased for the group with dural tears. Furthermore, significant more patients with incidental durotomy complained about headaches after surgery. A strong tendency for worse outcome in Group A was shown in regard to reported complaints and daily activity. The patients with incidental durotomy had a tendency to more reoperations, a longer duration of inability to work, more back-pain, and functional limitations related to back-pain (FFbH-R). Conclusion. Our study revealed that incidental durotomy in lumbar disc surgery was associated with long-term clinical sequelae. We therefore conclude that dural tears bring about poor clinical outcome at the long-term follow-up.

Localization of SP- and CGRP-immunopositive nerve fibers in the hip joint of patients with painful osteoarthritis and of patients with painless failed total hip arthroplasties

Using immunohistochemical methods we determined the presence of SP‐ and CGRP‐immunopositive nerve fibers in the hip joint of patients with femoral neck fracture (controls, group 1), painful osteoarthritis (group 2), and painless failed total hip arthroplasties (group 3). Immunoreactive nerve fibers were found in the soft tissue of the fossa acetabuli as well as in the subintimal part of the synovial layer in the hip joint capsule of groups 1 and 2. In the capsule of controls the innervation density had a median of 5.7 fibers/cm2 for CGRP‐ir and 3.2 fibers/cm2 for SP‐ir afferents. In the osteoarthritic group, the density significantly increased to a median of 15.6 fibers/cm2 for CGRP‐ir and 8.2 fibers/cm2 for SP‐ir neurons (p = 0.05). Patients with failed hip arthroplasties completely lacked these neuropeptide containing afferents. Innervation density in the fossa acetabuli of osteoarthritc patients showed a median of 14.1 fibers/cm2 for CGRP‐ir and 5.9 fibers/cm2 for SP‐ir afferents. From these data we assume that the hip joint capsule and the soft tissue of the fossa acetabuli are important triggers of nociception. This is supported by the fact, that patients with loosened total hip arthroplasties, where we failed to detect SP‐ and CGRP‐immunoreactive fibers, did not feel pain.

Particle-Induced Osteolysis in Three-Dimensional Micro-Computed Tomography

Small-animal models are useful for the in vivo study of particle-induced osteolysis, the most frequent cause of aseptic loosening after total joint replacement. Microstructural changes associated with particle-induced osteolysis have been extensively explored using two-dimensional (2D) techniques. However, relatively little is known regarding the 3D dynamic microstructure of particle-induced osteolysis. Therefore, we tested micro-computed tomography (micro-CT) as a novel tool for 3D analysis of wear debris-mediated osteolysis in a small-animal model of particle-induced osteolysis. The murine calvarial model based on polyethylene particles was utilized in 14 C57BL/J6 mice randomly divided into two groups. Group 1 received sham surgery, and group 2 was treated with polyethylene particles. We performed 3D micro-CT analysis and histological assessment. Various bone morphometric parameters were assessed. Regression was used to examine the relation between the results achieved by the two methods. Micro-CT analysis provides a fully automated means to quantify bone destruction in a mouse model of particle-induced osteolysis. This method revealed that the osteolytic lesions in calvaria in the experimental group were affected irregularly compared to the rather even distribution of osteolysis in the control group. This is an observation which would have been missed if histomorphometric analysis only had been performed, leading to false assessment of the actual situation. These irregularities seen by micro-CT analysis provide new insight into individual bone changes which might otherwise be overlooked by histological analysis and can be used as baseline information on which future studies can be designed.

Misinterpretation of cup anteversion in total hip arthroplasty using planar radiography

IntroductionAnteroposterior pelvic radiographs are routinely used to monitor cup orientation in total hip arthroplasty (THA). Analysis of planar radiographs leads to a certain degree of measurement error for the cup anteversion (AV). With the current study, we wanted to clarify whether planar radiography can be used for accurate evaluation of the THA position.Materials and methodsThe postoperative orientation of pelvic implants in 42 patients was analyzed according to five documented mathematical algorithms using planar radiographs. Postoperative computed tomography (CT) pelvis scans were available for all patients. A CT-based navigation system was used to determine AV. ResultsThe comparison showed that all five formulas presented substantial variations for the AV angle. Of these, Widmer’s algorithm presented the smallest difference compared to the CT. Misinterpretation of postoperative planar radiographs is a common problem in THA.ConclusionPlanar radiographs are too imprecise for exact evaluation of the correct cup AV after THA. CT-based analysis may be necessary if exact values are required.

Digital templating in total hip arthroplasty with the Mayo stem

PatientsIn 40 patients undergoing total hip arthroplasty with the Mayo femoral stem we studied how preoperative digital templating corresponded to the actual intraoperative choice of implant size, position, offset and restoration of leg length.ResultsThe preoperatively planned sizes of the components showed a high rate of coincidence with the sizes used intraoperatively [Intraclass Correlation Coefficient (ICC) 0.661–0.810]. However, the agreements in offset and CCD correction were poor (ICC 0.476, 0.253). This could be statistically attributed to the change in the distance from the medial margin of the stem to the medial margin of the medial femoral cortex and the height of osteotomy. The agreement in leg length correction was moderate (ICC 0.583), which was attributed to the change in the hip rotation center and the height of osteotomy.ConclusionCareful preoperative planning was useful for accurate size choice of the Mayo prosthesis. Factors such as the height of osteotomy and the distance from the medial margin of the stem to the medial margin of the medial femoral cortex in relation to the position of the Mayo stem should be taken into account in order to restore ideal offset and leg length.

Polyethylene Particle–Induced Bone Resorption in α-Calcitonin Gene–Related Peptide–Deficient Mice†

This study investigates the impact of α‐CGRP on bone metabolism after implantation of polyethylene particles. α‐CGRP knockout mice showed less osteolysis compared with wildtype mice. The local neurogenic microenvironment might be a crucial factor in particle‐induced osteolysis.

[Effects of clinically relevant alumina ceramic, zirconia ceramic and titanium particles of different sizes and concentrations on TNF-alpha release in a human macrophage cell line].

Abstract Einleitung: Als großes Problem der modernen Endoprothetik gilt die aseptische Lockerung von Prothesenkomponenten. Als Initiatorzytokin des Particle Disease wird derzeit der Tumor Nekrose Faktor α (TNFα) vermutet. Ziel der Studie war es die TNFα-Ausschüttung von Makrophagen-ähnlichen Zellen (MäZ) zu untersuchen, die durch Partikel, wie sie typischerweise während Revisionsoperationen gefunden werden stimuliert wurden. Hierzu verwendeten wir Aluminiumkeramik- (Al2O3), Zirkoniumoxid- (ZrO2) und Titanpartikel (Ti) unterschiedlicher Konzentration und Größe wie sie typischerweise bei Revisionsoperationen gefunden werden. Insbesondere sollte die Frage beantwortet werden, ob unterschiedliche Partikelgrößen und Materialgruppen (Titan und Keramik) eine differente TNFα-Ausschüttung bewirken. Methode: Um ein TNFα-Profil der einzelnen Materialien zu erhalten, verwendeten wir ein etabliertes Makrophagenmodell (Rader et al. 1999) mit THP-1 Zellen (humane Leukämiezellen). Die verschiedenen Partikelgrößen wurden in unterschiedlichen Konzentrationen für 6h mit 106 MäZ inkubiert. Der Überstand wurde entnommen und durch ELISA-Technik auf die TNFα-Konzentration untersucht. Ergebnis: die Verwendung von Ti-Partikel löste in beiden verwendeten Größen (0,2 μm und 2 μm) mit jeweils 8facher und 17facher TNFα-Sekretion gegenüber der Leerprobe den stärksten Anstieg aus. Es waren jedoch deutlich höhere Mengen an Ti-Partikel der Größe 0,2 μm notwendig, um o.g. Werte zu erreichen. Al2O3-Partikel zeigten ebenfalls eine signifikante Erhöhung der TNFα-Ausschüttung, lagen jedoch mit einer 4fachen Steigerung gegenüber der Leerprobe deutlich unter den Ti-Werten. In der maximalen TNFα-Sekretion fand sich kein Unterschied beider Partikelgrößen (0,6 μm und 2,5 μm), jedoch war eine nahezu 1000fach höhere Konzentration an Al2O3-Partikel der Größe 0,6 μm notwendig. Beim direkten Vergleich von Al2O3- und Ti-Partikeln gleicher Größe und Konzentration stimulierte Ti signifikant höhere TNFα-Ausschüttungen. ZrO2 konnte keine signifikante TNFα-Sekretion hervorrufen. Schlussfolgerung: Aufgrund der vorliegenden Ergebnisse empfiehlt sich die Verwendung von Keramikgleitpaarungen, die geringere biologische Potenz aufweisen als Metall- oder PE-Gleitpaarungen. Zusätzlich sollten größere Abriebpartikel vermieden werden. Frühzeitige Revisionsoperationen vermeiden große Mengen an Abriebpartikeln, somit könnten ausgedehnte lokale Osteolysen verhindert werden. Introduction: Aseptic loosening is considered to be the main problem of modern endoprothesis. Tumor necrosis factor α (TNFα) seems to be the initiator protein of particle disease. The aim of our study was to investigate the TNFα response of macrophage like cells (MLC) after stimulation with periprosthetic particles, typically found during revision surgery. For this purpose alumina ceramic (Al2O3), circonia ceramic (ZrO2) and titanium (Ti) particles of different sizes and concentrations were used. Important was to study the effects of different sizes due to TNFα secretion and the comparison of the biological effects of alumina ceramic and titanium. Method: To obtain an TNFα profile we used an established macrophage model (Rader et al.) with THP-1 cells (human monocytic cell line). Therefore 106 MLC were incubated with different particle concentrations and sizes for 6 h. The supernatent was then investigated for TNF·using ELISA assay. Results: Ti-particles provoked in both sizes (0,2 μm and 2,5 μm) the greatest TNFα response, 8 times and 17 times as high in comparison with control. But substantially more 0,2 μm sized Ti-particles were necessary to get the above mentioned results. Al2O3-particles were not as effective as Ti, but they released fourfold more TNFα compared to control. There was no difference in TNFα-secretion comparing Al2O3- particles of different sizes (0,6 μm and 2 μm), but a 1000times greater concentration of the 0,6Ìm sized particles were needed. Using Al2O3- and Ti-particles of the same size and concentration, Ti provoked a significant higher TNFα response. ZrO2 showed no effects on TNFα release. Conclusion: Because of our results we recommend ceramic articulating surfaces, which are superior to metal on metal matings ion term of biological reactions. Additionally bigger wear particles should be avoided. Revisionoperation should be done early to avoid huge amount of wear particles and to minimize local osteolysis

Comparison of subtraction arthrography, radionuclide arthrography and conventional plain radiography to assess loosening of total knee arthroplasty / Vergleich von Subtraktionsarthrographie, Radionuklidarthrographie und konventionellem Röntgen zur Erfassung von Prothesenlockerungen in der Knierevisionschirurgie

Abstract The value of plain radiographs, digital subtraction arthrography and radionuclide arthrography was analysed in 23 cases of failed total knee arthroplasty. The preoperative diagnosis was compared with the intraoperative assessment. Sensitivity, specificity and the positive and negative predictive value for assessing a loose component were determined separately for the femoral and tibial components. At revision we found 13 loose femoral and 12 loose tibial implants. In eight cases both components were unstable. Plain radiography had a sensitivity of 77% for loosening of the femoral and 83% for the tibial component; digital subtraction arthrography 77% for the femoral and 8% for the tibial component and radionuclide arthrography 31% and 8%. The specificity for plain radiography was 90% for the femoral and 72% for the tibial implant. For subtraction arthrography it was 50% and 82% and for subtraction arthrography 70% and 82%. Radiography had the highest positive and negative predictive values for both components compared with the other two techniques. As a diagnostic tool to detect implant loosening, plain radiography is the most effective in this study. Subtraction arthrography and radionuclide arthrography are not suitable for use as routine methods for detection of total knee arthroplasty loosening. In 23 Revisionen einer Kniegelenkstotalendoprothese wurden konventionelle Röntgenbilder, digitale Subtraktionsarthrographien und Radionuklidarthrographien analysiert, um die Effizienz dieser Methoden hinsichtlich der Diagnose von Implantatlockerungen festzustellen. Die präoperative Diagnose wurde mit dem intraoperativen Befund verglichen. Sensitivität, Spezifität und der positive und negative Vorhersagewert zu Erfassung einer Prothesenlockerung wurden separat für die femorale und tibiale Komponente erfasst. Bei der Revision wurden 13 gelockerte femorale und 12 gelockerte tibiale Implantate gefunden. In acht Fällen waren beide Komponenten gelockert. Konventionelles Röntgen hatte eine Sensitivität von 77% zur Erfassung einer Lockerung des femoralen Schilds bzw. 83% für die tibiale Komponente; die digitale Subtraktionsarthrographie ergab 77% für das femorale und 8% für das tibiale Implantat; die Radionuklidarthrographie hatte eine Sensitivität von 31% und 8%. Die Spezifität für konventionelles Röntgen lag bei 90% für femoral und 72% für tibial. Für die digitale Subtraktionsarthrographie waren es 50% und 82% und für die Radionuklidarthrographie 70% und 82%. Konventionelles Röntgen hatte den höchsten positiven und negativen Vorhersagewert für beide Komponenten verglichen mit den beiden anderen Techniken. Als diagnostisches Verfahren zur Erfassung einer Prothesenlockerung stellte sich das konventionelle Röntgen in dieser Studie als die effektivste Methode heraus. Die digitale Subtraktionsarthrographie bzw. die Radionuklidarthrographie eignen sich nicht als Routineverfahren zur Erfassung einer Kniegelenkstotalendoprothesenlockerung.

The density of nociceptive SP- and CGRP-immunopositive nerve fibers in the dura mater lumbalis of rats is enhanced after laminectomy, even after application of autologous fat grafts

A considerable number of patients complain about pain after lumbar surgery. The spinal dura mater has been debated as a possible source of this pain. However, there is no information if laminectomy influences the nociceptive sensory innervation of the dura. Therefore, we quantitatively evaluated the density of SP- and CGRP-immunopositive nerve fibers in the dura mater lumbalis in an animal model of laminectomy. Twelve adult Lewis rats underwent laminectomy, in six of them the exposed dura was covered by an autologous fat graft. Further six animals without surgical treatment served as controls. Six weeks after surgery, the animals were perfused and the lumbar dura was processed immunohistochemically for the detection of CGRP- and SP-containing nerve fibers. In controls, the peptidergic nerve fibers were found predominantly in the ventral but rarely in the dorsal dura mater lumbalis. After laminectomy, the density of SP- and CGRP-immunopositive neurons significantly increased in ventral as well as in dorsal parts of the dura. Axonal spines could be observed in some cases at the site of laminectomy. The application of autologous fat grafts failed to inhibit the significant increase in the density of peptidergic afferents. Thus, we have provided the first evidence that laminectomies induce an increase in the density of putative nociceptive SP- and CGRP-immunopositive neurons in the lumbar dura mater ascribable to an axonal sprouting of fine nerve fibers. This effect was not prevented by using autologous fat grafts. It is conceivable that the neuronal outgrowth of nociceptive afferents is a cause of low back pain observed after lumbar surgery.