Olaf Hasart

Diagnosis of periprosthetic infection following total hip arthroplasty – evaluation of the diagnostic values of pre- and intraoperative parameters and the associated strategy to preoperatively select patients with a high probability of joint infection

BackgroundThe correct diagnosis of a prosthetic joint infection (PJI) is crucial for adequate surgical treatment. The detection may be a challenge since presentation and preoperative tests are not always obvious and precise. This prospective study was performed to evaluate a variety of pre- and intraoperative investigations. Furthermore a detailed evaluation of concordance of each preoperative diagnosis was performed, together with a final diagnosis to assess the accuracy of the pre-operative assumption of PJI.MethodsBetween 01/2005 and 02/2007, a prospective analysis was performed in 50 patients, who had a two stage revision because of assumed PJI. Based on clinical presentation, radiography, haematological screening, or early failure, infection was assumed and a joint aspiration was performed. Depending upon these findings, a two stage revision was performed, with intra-operative samples for culture and histological evaluation obtained. Final diagnosis of infection was based upon the interpretation of the clinical presentation and the pre- and intraoperative findings.ResultsIn 37 patients a positive diagnosis of PJI could be made definitely. The histopathology yielded the highest accuracy (0.94) in identification of PJI and identified 35 of 37 infections (sensitivity 0.94, specificity 0.94, positive-/negative predictive value 0.97/0.86). Intra-operative cultures revealed sensitivities, specificities, positive-/negative predictive values and accuracy of 0.78, 0.92, 0.96, 0.63 and 0.82. These values for blood screening tests were 0.95, 0.62, 0.88, 0.80, and 0.86 respectively for the level of C-reactive protein, and 0.14, 0.92, 0.83, 0.29 and, 0.34 respectively for the white blood-cell count. The results of aspiration were 0.57, 0.5, 0.78, 0.29, and 0.54.ConclusionThe detection of PJI is still a challenge in clinical practice. The histopathological evaluation emerges as a highly practical diagnostic tool in detection of PJI. Furthermore, we found a discrepancy between the pre-operative suspicion of PJI and the final post-operative diagnosis, resulting in a slight uncertainty in whether loosening is due to bacterial infection or not. The variation in accuracy of the single tests may influence the detection of PJI. Level of Evidence: Diagnostic Level I.

CT evaluation of native acetabular orientation and localization: Sex-specific data comparison on 336 hip joints

BACKGROUND The reorientation of the acetabular component in total hip replacement is currently carried out under consideration of the safe zone, respecting the best possible range of motion and is influenced by wear debris of different bearings. Is the preferred orientation a reconstruction of the native anatomy and are there sex-specific differences? METHODS On the basis of 168 CT datasets (72 women, 96 men) 336 native hip joints were analysed. The abduction and anteversion of the acetabulum as well as the location of the hip center were detected. As a reference the anterior pelvic plane was used. RESULTS The 144 female hip joints showed a mean abduction of 53.0 degrees (SD 6.14 degrees ) and an anteversion of 24.63 degrees (SD 6.61 degrees ). The 192 male hip joints showed an abduction of 53.58 degrees (SD 6.68 degrees ) and an anteversion of 21.31 degrees (SD 6.17 degrees ). Significant differences were observed on comparison between the sexes in relation to the anteversion and the location of the hip center. Likewise, there was a significant correlation between the position of the hip center and the degree of anteversion. CONCLUSIONS In total hip arthroplasty a reconstruction of the native acetabular orientation is not possible, gender specific characteristics should be considered.

Improvement in the detection rate of PJI in total hip arthroplasty through multiple sonicate fluid cultures

The microbiological culture of sonicate fluid (SFC) of explanted endoprosthetic components has increased the rate of bacterial isolation in comparison to conventional microbiological methods. However, this creates the problem of interpreting cases of singular bacterial isolation through SFC, while all other microbiological samples remain negative. The aim of this study was to reference these singular positive SFC against, the histological classification of the periprosthetic membrane (PM), and the utilization of multiple SFC (separate sonication of individual endoprosthetic components). In this prospective study we compared the effect of multiple SFC for detection of periprosthetic joint infection (PJI) in patients with total hip revision surgery. All microbiological results were referenced against PM. Of the 102 cases there were 37 cases of PJI. Single SFC achieved the highest sensitivity of all individual parameters with 89% and a specificity of 72%. When multiple SFC were employed the sensitivity and specificity increased to 100%. There was a concordance of 86% between the PM and SFC. SFC achieved the highest sensitivity and it was possible to further improve the sensitivity and specificity when using multiple cultures. Multiple SFC and PM are beneficial to help reference singular bacterial isolations and achieve the diagnosis of PJI.

Use of an ultrasound-based navigation system for an accurate acetabular positioning in total hip arthroplasty: a prospective, randomized, controlled study.

The purpose of this study was to compare an ultrasound-based navigation system with an imageless navigation system with surface registration in the postoperative acetabular cup position. A prospective randomized controlled study of 2 groups of 40 patients each was performed. In the first group, cup positioning was assisted by an ultrasound-based navigation system, and in the second group, the cup was assisted by imageless navigation system with surface registration. There was significantly more outliers in the imageless navigation group. In addition, there was statistical significance in the anteversion angles and in the anteversion error between the imageless navigation and ultrasound-based navigation groups. Ultrasound-based navigation improves cup positioning in total hip arthroplasty better than an imageless navigation system by reducing the outliers, achieving a higher accuracy of anteversion.

[Histopathological diagnosis of periprosthetic joint infection following total hip arthroplasty : use of a standardized classification system of the periprosthetic interface membrane].

BACKGROUND The distinction between aseptic and septic loosening of a total hip arthroplasty is a diagnostic challenge. Therapy and clinical success depend on the correct diagnosis. Histopathological evaluation of the periprosthetic interface membrane is one possible diagnostic parameter; detailed analysis of tissue characteristics may reflect the cause of failure. This study evaluated the diagnostic value of a published histopathological consensus classification for the periprosthetic interface membrane in the identification of periprosthetic joint infection (PJI). METHODS Between 2004 and 2008, a prospective analysis was performed in 106 patients who had revisions because of assumed PJI. Based on clinical presentation, radiography, and haematological screening, infection was assumed, and a joint aspiration was performed. Based on these findings, a two-stage revision was performed, with intraoperative samples for culture and histological evaluation obtained. Final diagnosis of infection was based on the interpretation of the clinical presentation and the preoperative and intraoperative findings. The basis for histopathological evaluation was the consensus classification for the periprosthetic interface membrane. Sensitivity, specificity, and accuracy were calculated for each parameter. RESULTS In 92 patients, a positive diagnosis of PJI could be made. Histopathology yielded the highest accuracy (0.93) in identification of PJI, identifying 86 of 92 infections (69 type II, 17 type III). In 13 of the 14 noninfected hips, histopathology correlated in 13 (93%) cases (10 type I, three type IV). The accuracies of microbiological culture, C-reactive protein, and aspiration were 0.82, 0.86, and 0.54, respectively. CONCLUSION In the diagnosis of PJI, histopathological evaluation of the periprosthetic interface membrane proved very effective. To analyse the cause of prosthesis loosening, tissue samples of the periprosthetic interface membrane should be evaluated on the basis of the consensus classification in all revision surgeries.

Rekonstruktion größerer Pfannendefekte mit metallischen Augmentaten – Trabecular Metal Technology

ZusammenfassungOperationszielPfannenwechsel mit Wiederherstellung des originären Rotationszentrums. Wiederherstellung einer schmerzfreien Gelenkfunktion. Hohe Primär- sowie Sekundärstabilität. Vermeidung von zusätzlichem Knochenverlust.IndikationenKnöcherne Defekte des Azetabulums im ventrokranialen, kranialen oder dorsokranialen Areal. Größere kavitäre, zentrale oder ovale Defekte (Paprosky IIb–IIIb). Segmentale Defekte (ventral bis etwa die Hälfte der Gesamtzirkumferenz, dorsal bis etwa ein Drittel der Gesamtzirkumferenz).KontraindikationenManifeste Gelenkinfektion. Beckendiskontinuität (Paprosky IV).OperationstechnikDarstellung des Azetabulums und Detektion der Defekt-situation, sorgfältige Säuberung des ossären Lagers von Granulationsgewebe, ggf. Anfrischung des Knochens. Einpassen der metallischen Probeaugmentate. Ziel ist die Defektverkleinerung bzw. das Erreichen eines hemisphärischen Defekts (bei ovalen oder kavitären Defektsituationen) oder eines sog. „contained“ Defekts (bei segmentalen Schäden). Danach Einpassen der Probepfanne. Bei ausreichender Defektfüllung und Stabilität folgen die Einpassung des definitiven Augmentats in den Defekt und die Fixierung mit zwei oder drei Schrauben. Diese werden in die krafttragende Richtung platziert. Zusätzlich besteht die Möglichkeit der ergänzenden Anlagerung von Spongiosachips in den Arealen der Augmentate und/oder des ossären Azetabulums. Versiegelung der kaudalen Oberfläche des Augmentats (Kontaktareal zur Pfanne) mit Knochenzement sowie anschließendes Einschlagen und Verschrauben der Pressfit-Pfanne.WeiterbehandlungBei stabiler Rekonstruktion der azetabulären und femoralen Defekte ist eine Vollbelastung möglich. Bei sehr ausgedehnten ossären Defekten oder einer pelvitrochantären Insuffizienz wird eine Teilbelastung mit 20 kp für 6 Wochen empfohlen. Eine Anschlussheilbehandlung ist in fast allen Fällen möglich.ErgebnisseVon 2005 bis 2007 erfolgte bei 38 Patienten mit Pfannendefektsituationen Typ IIIa und IIIb nach Paprosky die Rekonstruktion mit dem TMT-System (Trabecular Metal Technology). Nach 25 Monaten war bei allen Patienten eine signifikante Verbesserung der Funktion zu beobachten. Der Merle-d’Aubigné-Score stieg von 6 auf 13 Punkte, der Harris-Hip-Score von 29 auf 78 Punkte. Zwei Revisionen waren wegen Migration bzw. Frühlockerung des Implantats notwendig.AbstractObjectiveRevision of cup and reconstruction of original center of rotation. High primary and secondary stability. Prevention of additional bone loss.IndicationsOsseous defects at the anterior-cranial, cranial and posterior-cranial rim of acetabulum. Larger cavitary, medial or oval defects (Paprosky IIb–IIIb). Segmental defects (anterior column up to half of host bone, posterior column up to one third of host bone).ContraindicationsInfection of total hip arthroplasty. Pelvic discontinuity (Paprosky IV).Surgical TechniqueExposure of acetabulum and detection of defects. Complete removal of soft tissue from acetabulum, reaming of sclerotic bone, if necessary. Adaptation of trial augments to close an oval defect to a round defect and to reach an uncontained defect, respectively. Adaptation of trial cup. In case of sufficient stability, fixation of final augment with two or three screws in cranial bone stock. The screws should be directed to iliosacral joint. Augmentation with allogenic bone chips is possible in the region of wedge and acetabulum as well. Sealing of rough augment surface with bone cement. Implantation of cup, fixation with screws. Application of insert.Postoperative ManagementDepending on bone defects, full weight bearing is possible. In cases of severe bone defects, reduction of weight bearing to 20 kg for 6 weeks is recommended. Postoperative physiotherapy is possible in most cases.ResultsBetween 2005 and 2007, 38 patients with acetabular defects type IIIa und IIIb according to Paprosky underwent reconstruction using the TMT system (Trabecular Metal Technology). After 25 months, a significant functional improvement was seen in all patients. The Merle d’Aubigné Score increased from 6 points preoperatively to 13 points postoperatively, the Harris Hip Score from 29 to 78 points. Two revisions were necessary because of loosening or migration of the cup.

Ultrasound-based navigation and 3D CT compared in acetabular cup position.

Intraoperative landmarks are used in image-free navigation systems. The ultrasound-based navigation systems try to overcome the problems of positional deviation associated with soft tissue. Our study analyzed the accuracy of ultrasound-based navigation of cup positioning compared with postoperative 3-dimensional (3D) computed tomography scans of cup positioning. Twenty-five ultrasound-navigated total hip arthroplasties (THAs) were analyzed. The difference between the intraoperative cup orientation (navigation) and the postoperative cup position (CT) was evaluated. The average difference between intraoperative navigation and postoperative CT measurements was 2.8 degrees (SD+/-1.8 degrees ) for abduction and 2.2 degrees (SD+/-1.6 degrees ) for anteversion. Therefore, we recommend ultrasound-based navigation as an exact tool for cup positioning in THA.

Histopathologische Diagnose der periprothetischen Gelenkinfektion nach Hüftgelenkersatz

BACKGROUND The distinction between aseptic and septic loosening of a total hip arthroplasty is a diagnostic challenge. Therapy and clinical success depend on the correct diagnosis. Histopathological evaluation of the periprosthetic interface membrane is one possible diagnostic parameter; detailed analysis of tissue characteristics may reflect the cause of failure. This study evaluated the diagnostic value of a published histopathological consensus classification for the periprosthetic interface membrane in the identification of periprosthetic joint infection (PJI). METHODS Between 2004 and 2008, a prospective analysis was performed in 106 patients who had revisions because of assumed PJI. Based on clinical presentation, radiography, and haematological screening, infection was assumed, and a joint aspiration was performed. Based on these findings, a two-stage revision was performed, with intraoperative samples for culture and histological evaluation obtained. Final diagnosis of infection was based on the interpretation of the clinical presentation and the preoperative and intraoperative findings. The basis for histopathological evaluation was the consensus classification for the periprosthetic interface membrane. Sensitivity, specificity, and accuracy were calculated for each parameter. RESULTS In 92 patients, a positive diagnosis of PJI could be made. Histopathology yielded the highest accuracy (0.93) in identification of PJI, identifying 86 of 92 infections (69 type II, 17 type III). In 13 of the 14 noninfected hips, histopathology correlated in 13 (93%) cases (10 type I, three type IV). The accuracies of microbiological culture, C-reactive protein, and aspiration were 0.82, 0.86, and 0.54, respectively. CONCLUSION In the diagnosis of PJI, histopathological evaluation of the periprosthetic interface membrane proved very effective. To analyse the cause of prosthesis loosening, tissue samples of the periprosthetic interface membrane should be evaluated on the basis of the consensus classification in all revision surgeries.

Reconstruction of large acetabular defects using trabecular metal augments

ZusammenfassungOperationszielPfannenwechsel mit Wiederherstellung des originären Rotationszentrums. Wiederherstellung einer schmerzfreien Gelenkfunktion. Hohe Primär- sowie Sekundärstabilität. Vermeidung von zusätzlichem Knochenverlust.IndikationenKnöcherne Defekte des Azetabulums im ventrokranialen, kranialen oder dorsokranialen Areal. Größere kavitäre, zentrale oder ovale Defekte (Paprosky IIb–IIIb). Segmentale Defekte (ventral bis etwa die Hälfte der Gesamtzirkumferenz, dorsal bis etwa ein Drittel der Gesamtzirkumferenz).KontraindikationenManifeste Gelenkinfektion. Beckendiskontinuität (Paprosky IV).OperationstechnikDarstellung des Azetabulums und Detektion der Defekt-situation, sorgfältige Säuberung des ossären Lagers von Granulationsgewebe, ggf. Anfrischung des Knochens. Einpassen der metallischen Probeaugmentate. Ziel ist die Defektverkleinerung bzw. das Erreichen eines hemisphärischen Defekts (bei ovalen oder kavitären Defektsituationen) oder eines sog. „contained“ Defekts (bei segmentalen Schäden). Danach Einpassen der Probepfanne. Bei ausreichender Defektfüllung und Stabilität folgen die Einpassung des definitiven Augmentats in den Defekt und die Fixierung mit zwei oder drei Schrauben. Diese werden in die krafttragende Richtung platziert. Zusätzlich besteht die Möglichkeit der ergänzenden Anlagerung von Spongiosachips in den Arealen der Augmentate und/oder des ossären Azetabulums. Versiegelung der kaudalen Oberfläche des Augmentats (Kontaktareal zur Pfanne) mit Knochenzement sowie anschließendes Einschlagen und Verschrauben der Pressfit-Pfanne.WeiterbehandlungBei stabiler Rekonstruktion der azetabulären und femoralen Defekte ist eine Vollbelastung möglich. Bei sehr ausgedehnten ossären Defekten oder einer pelvitrochantären Insuffizienz wird eine Teilbelastung mit 20 kp für 6 Wochen empfohlen. Eine Anschlussheilbehandlung ist in fast allen Fällen möglich.ErgebnisseVon 2005 bis 2007 erfolgte bei 38 Patienten mit Pfannendefektsituationen Typ IIIa und IIIb nach Paprosky die Rekonstruktion mit dem TMT-System (Trabecular Metal Technology). Nach 25 Monaten war bei allen Patienten eine signifikante Verbesserung der Funktion zu beobachten. Der Merle-d’Aubigné-Score stieg von 6 auf 13 Punkte, der Harris-Hip-Score von 29 auf 78 Punkte. Zwei Revisionen waren wegen Migration bzw. Frühlockerung des Implantats notwendig.AbstractObjectiveRevision of cup and reconstruction of original center of rotation. High primary and secondary stability. Prevention of additional bone loss.IndicationsOsseous defects at the anterior-cranial, cranial and posterior-cranial rim of acetabulum. Larger cavitary, medial or oval defects (Paprosky IIb–IIIb). Segmental defects (anterior column up to half of host bone, posterior column up to one third of host bone).ContraindicationsInfection of total hip arthroplasty. Pelvic discontinuity (Paprosky IV).Surgical TechniqueExposure of acetabulum and detection of defects. Complete removal of soft tissue from acetabulum, reaming of sclerotic bone, if necessary. Adaptation of trial augments to close an oval defect to a round defect and to reach an uncontained defect, respectively. Adaptation of trial cup. In case of sufficient stability, fixation of final augment with two or three screws in cranial bone stock. The screws should be directed to iliosacral joint. Augmentation with allogenic bone chips is possible in the region of wedge and acetabulum as well. Sealing of rough augment surface with bone cement. Implantation of cup, fixation with screws. Application of insert.Postoperative ManagementDepending on bone defects, full weight bearing is possible. In cases of severe bone defects, reduction of weight bearing to 20 kg for 6 weeks is recommended. Postoperative physiotherapy is possible in most cases.ResultsBetween 2005 and 2007, 38 patients with acetabular defects type IIIa und IIIb according to Paprosky underwent reconstruction using the TMT system (Trabecular Metal Technology). After 25 months, a significant functional improvement was seen in all patients. The Merle d’Aubigné Score increased from 6 points preoperatively to 13 points postoperatively, the Harris Hip Score from 29 to 78 points. Two revisions were necessary because of loosening or migration of the cup.

Influence of body mass index and thickness of soft tissue on accuracy of ultrasound and pointer based registration in navigation of cup in hip arthroplasty

BACKGROUND Precise identification of bony landmarks by use of pointer based navigation systems is influenced by thickness of soft tissue. Ultrasound-based navigation systems try to overcome the problems of positional deviation associated with soft tissue. The aim of the study was to investigate the influence of the BMI and the thickness of the soft tissue on the post-operative cup position and accuracy in the application of an ultrasound-based (US CAOS) and a pointer-based navigation system (P CAOS). METHODS 82 patients received a hip replacement in minimally invasive surgery in two cohorts: US CAOS group: using ultrasound navigation (n = 39) and P CAOS group: using a pointer-based navigation (n = 43). RESULTS There was a significant difference in anteversion and anteversion error between the groups. In addition, we observed a significant correlation between the thickness of the presymphysial soft tissue and the anteversion error in both groups. We also detected a significant correlation between the anteversion error and the BMI in both groups. However, the absolute error in anteversion with increasing thickness of the soft tissue layer was slighter in the ultrasound-based group compared to pointer-based navigation. CONCLUSIONS The accuracy of the ultrasound-based and pointer-based navigation systems are influenced by the BMI and the thickness of the soft tissue layer above the symphysis. However, ultrasound-based navigation seems to have advantages with thicker soft tissue layers, as seen in overweight and obese patients.