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.

[More muscle mass in men: explanatory model for superior outcome after total hip arthroplasty]. / Mehr Muskelmasse bei Männern : Erklärungsmodell für bessere Ergebnisse nach Hüfttotalendoprothesenimplantation.

BACKGROUND: Men show better functional results after total hip arthroplasty (THA). The aim of this study was a patient-specific analysis of the hip joint muscles in comparison to the joint geometry. METHODS: In this study 93 computed tomography (CT) scans of the pelvis (45 men, 48 women) were analyzed to determine hip joint geometry and the volume of the gluteus medius (GMV), gluteus maximus (GXV) and tensor fasciae latae (TFL) muscles. The abduction muscle volumes were analyzed with respect to patient-specific adduction moments. RESULTS: The absolute total volume of the hip muscular system (TMV) was larger in men than in women (1913 ccm vs. 1479 ccm; p <0.0001). Men exhibited a more progressive increase of muscle volume as the adduction moment increases. CONCLUSIONS: Men have a greater abduction muscle mass in order to balance adduction moments occurring in the hip joint and therefore have more muscle mass to compensate the inevitable intraoperative muscle damage during THA. This argument supports the extraordinary importance of muscle sparing surgical techniques in women.

[Dislocation after total hip arthroplasty]. / Luxationen nach Hüftendoprothetik.

Dislocations after total hip arthroplasties are one of the most common complications of the procedure. According to registers, recurrent hip dislocations account for up to 30 % of the indications for a revision operation. The incidence of a dislocation is influenced by indication-associated, patient-dependent and operation-specific risk factors. 50 % of the dislocations occur within the first 3 months which confirms the high relevance of operation-specific influencing factors. The diagnosis is almost always made with the help of computed tomography, as this is the only method to determine the three-dimensional relationship of the components. A dynamic fluoroscopic examination can verify an increased translation (reduced soft-tissue tension) and thus enables a functional examination to determine the mechanism of the dislocation. By means of a classification of dislocations into five types under consideration of the implant position, the sufficiency of the pelvitrochantar musculature, the presence of an impingement, the congruence of head and acetabular liner as well as combinations of these factors it is possible to plan an adequate therapy. From the therapeutic point of view the correct positioning of the stem and head is of decisive importance. In addition therapeutic success can be realized by using larger head diameters through to tripolar sockets, reconstruction of soft tissues and, last but not least, an adequate postoperative immobilization. Even so, this treatment is associated with a high rate of complications and in the literature failure rates of up to one third, i.e., the reoccurrence of a dislocation, are reported.

[Shortening osteotomy for alloarthoplastic joint replacement for hip dislocation in adults]. / Die Verkürzungsosteotomie im Rahmen des alloarthoplastischen Gelenkersatzes bei hoher Hüftluxation im Erwachsenenalter.

OBJECTIVE: Total hip arthroplasty to create an articulating hip joint. Acetabular cup implantation in the original rotational center of the pelvis. Simultaneous femoral shortening osteotomy to prevent neurovascular damage and equalize leg length in patients with unilateral occurrence. INDICATIONS: Developmental dysplasia of the hip (DDH) in adults; type 3 and 4 dislocation according to Crowe. CONTRAINDICATIONS: Cerebrospinal dysfunction with permanent restriction of coordination ability, muscular dystrophies, and multiple malformations of the musculoskeletal system. Apparent disturbance of the bone metabolism. SURGICAL TECHNIQUE: The Watson-Jones interval approach to the hip joint is used to avoid functional disorders of the hip abductors. After preparation of the proximal femur and femoral neck resection, adjustment of the non-regularly developed acetabular cavity with reduced anterior coverage takes place. The cup component is implanted and the interval between the vastus intermedius and the vastus lateralis below the lesser trochanter examined. Loss of periosteum of the femoral cortex due to blunt spreading is to be avoided. Following the femoral shortening osteotomy initially the preparation of the distal bone segment takes place to adjust the endofemoral canal for shaft implantation in the following preparation of the metaphyseal segment. Afterwards osteotomy-bridging implantation of a cementless, distal anchoring stem design is performed. POSTOPERATIVE MANAGEMENT: Partial weight bearing of the leg with 20 kp is necessary for 6 weeks combined with therapy of existing contractures and active pelvic rotation training. Within 10 postoperative weeks full weight bearing is usually reached. After this period mobilization without crutches is possible. Inpatient rehabilitation is possible after bony recovery of the femoral osteotomy. RESULTS: From 1993 to 1999, the first 15 total hip arthroplasties were performed in adult patients with DDH; they were treated with simultaneous femoral shortening osteotomy and without additive osteosynthesis. During the midterm follow-up (4.3 years), no failure of the femoral component was observed with complication-free osseous healing of the osteotomy. One cup revision was necessary in this period. The Merle d'Aubigné score increased from 8.2 preoperatively to 15.5 points.

Extended sagittal saw cut significantly reduces fracture load in cementless unicompartmental knee arthroplasty compared to cemented tibia plateaus: an experimental cadaver study.

PURPOSE: Periprosthetic tibial plateau fractures represent a rare but serious complication in unicompartmental knee arthroplasty and are associated with extended sagittal tibial bone cuts. These can occur during the surgery, weaken the posterior cortex of the tibia and are associated with periprosthetic tibial plateau fractures. Although excellent long-term results have been reported with cemented unicompartmental knee arthroplasty, there is high interest in cementless fixation. The aim of the study was to compare fracture loads of cementless and cemented unicompartmental knee arthroplasty. METHODS: Tibial components of the Oxford Uni were implanted in six paired fresh-frozen tibiae with a defined extended saw cut (10°) at the dorsal cortex of each specimen. In one set, surgery was performed with cement fixation, and in the other, cementless components were implanted. Vertical loads were then applied under standardised conditions to fracture the specimens. RESULTS: Median loads of 3.7 (0.7-6.9) kN led to fractures in the cemented group, whereas cementless fixated tibiae fractured with a median load of 1.6 (0.2-4.3) kN (P = 0.02). CONCLUSION: The loading capacity in tibiae with cementless components is significantly less compared to cemented fixation. The results show that in case of an extended sagittal bone cut patients especially those with poor bone quality who are treated with a cementless unicompartmental knee arthroplasty are at higher risk for periprosthetic tibial fractures.

[Muscle trauma in primary total hip arthroplasty depending on age, BMI, and surgical approach: minimally invasive anterolateral versus modified direct lateral approach]. / Muskeltrauma in der primären Hüftendoprothetik unter Berücksichtigung von Alter und BMI sowie in Abhängigkeit vom operativen Zugangsweg: Minimalinvasiver anterolateraler vs. modifizierter transglutealer Zugang.

BACKGROUND: Maximum preservation of periarticular musculature is essential for the success of total hip arthroplasty. A poorer functional outcome often occurs following total hip arthroplasty, especially in older and overweight patients and is presumed to have a muscular basis. Minimally invasive hip endoprosthetics for muscle-preserving implantation have now become established in orthopedic surgery. METHODS: A primary hip endoprosthesis was implanted in a total of 39 patients using a transgluteal (modified direct-lateral, mDL, n=19) or anterolateral minimally invasive approach (ALMI, n=20). Magnetic resonance imaging was performed preoperatively as well as 3 and 12 months after the operation. Fatty atrophy (FA) of the gluteus medius muscle was evaluated as a function of body mass index (BMI), patient age and the influence of the access route. RESULTS: In the overweight group a significantly higher FA of the gluteus medius muscle was found 3 and 12 months after the operation and a significantly higher grade FA using the standard access in contrast to the normal weight group. A significantly higher FA of the gluteus medius muscle was found in the older patient group 3 and 12 months postoperation as well as a significantly higher atrophy using the mDL access. CONCLUSIONS: Muscle trauma is demonstrably reduced using a minimally invasive access, especially in older and overweight patients. In these patients there is also a substantially higher postoperative muscular atrophy after implantation of a prosthesis than in corresponding normal weight and younger patients. The higher vulnerability and poorer capacity for regeneration of periarticular musculature means that this patient group particularly profits from a minimally invasive access route.

[Histopathological diagnosis of periprosthetic joint infection following total hip arthroplasty : use of a standardized classification system of the periprosthetic interface membrane]. / Histopathologische Diagnose der periprothetischen Gelenkinfektion nach Hüftgelenkersatz : Verwendung eines standardisierten Klassifikationssystems der periprothetischen Interface-Membranen.

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.

[Obturator externus impingement after total hip replacement]. / Das Obturator-externus-Impingement nach Hüftprothesenimplantation.

A patient with a painful total hip replacement that is not obviously loose presents a diagnostic challenge. One of the rare causes is psoas impingement syndrome. Because there are several periarticular muscles, further muscle impingements are possible. We report on a case of painful obturator externus muscle impingement on the acetabular cup. On magnetic resonance imaging, a pathologic contact between the obturator externus muscle and the caudal rim of the cup was seen. A positive injection confirmed the pathologic contact.

[On the biomechanics of the hip: relevance of femoral anteversion for hip contact force and loading using a short-stemmed prostheses]. / Zur Biomechanik der Hüfte : Relevanz der Schafttorsion für Hüftkontaktkraft und Krafteinleitung bei Kurzschaftprothesen.

Short-stemmed hip implants were established in total hip arthroplasty in the last years. Also patients with secondary osteoarthritis of the hip with pathological anteversion of the femoral neck are treated increasingly using this method. Therefore an investigation was performed to analyze the resulting hip contact force and femoral loading in the proximal femur at the solid model of the "standardized femur". Two different situations of femoral component anteversion were simulated. Increased hip contact forces and an increase of medial and lateral cortex loads result in the anteverted model. With present level of knowledge about the influence of the hip contact force the use of short-stemmed implants is not uncritically in patients with degenerative osteoarthritis of the hip combined with rotational disorders of the proximal femur. The selection of the tribological pairing is to be considered more strongly regarding the wear behavior.

[Implant with a mobile or a fixed bearing in unicompartmental knee joint replacemen]. / Mobile vs. feste Plattform bei unikondylärem Kniegelenkersatz.

Although the goal of anatomical and functional joint reconstruction in unicompartmental knee replacement is well defined, no uniform implant design has become established. In particular, the differential indications for implantation of an implant with a mobile or a fixed bearing are still not clear. The long-term results of mobile and with fixed bearings are comparable, but there are significant differences in resulting knee joint kinematics, tribological properties and implant-associated complications. In unicompartmental knee replacement mobile bearings restore the physiological joint kinematics better than fixed implants, although the differences to total knee arthroplasty seem minor. The decoupling of mobile bearings from the tibia implant allows a high level of congruence with the femoral implant, resulting in larger contact areas than with fixed bearings. This fact in combination with the more physiological joint kinematics leads to less wear and a lower incidence of osteolyses with mobile bearings. Disadvantages of mobile bearings are the higher complication and early revision rates resulting from bearing dislocation and impingement syndromes caused by suboptimal implantation technique or instability. Especially in cases with ligamentous pathology fixed bearings involve a lower complication rate. It seems their use can also be beneficial in patients with a low level of activity, as problems related to wear are of minor importance for this subgroup. The data currently available allow differentiations between various indications for implants with mobile or fixed bearings, so that the implants can be matched to the patient and the joint pathology in unicompartmental knee joint replacement.

[The reconstruction of extended acetabular bone defects in revision hip arthroplasty--risk factors for migration and loosening using the pedestal cup]. / Die Rekonstruktion grosser segmentaler Knochendefekte mit der Sockelpfanne--Einflussfaktoren auf das Migrations- und Lockerungsverhalten.

AIM: For the reconstruction of extended acetabular bone defects in revision hip arthroplasty different implants and techniques are available.However, in cases with a broad operative range of new implants, specific indications must be determined. The aim of this study is to determine the risk factors for migration and loosening associated with implantation of the pedestal cup. METHOD: In a retrospective study the first 50 implantations of the pedestal cup in our hospital for high-grade acetabular defects (Paprosky classification II and III) were examined after a medium period of 26 months. Differences between radiologically loosened and osteal integrated implants in consideration of the preoperative osseous situation(defect size and morphology, bone density)as well as the implant positioning were determined as risk factors of an implant failure. RESULTS: Three (6%) intraoperative implant-associated complications occurred, which were in the phase of the initial learning curve. In the early postoperative period 10 hip dislocations (20%)occurred. Two septic loosenings (4%) and 6 aseptic loosenings (12%) were observed. In 7 further cases a significant migration of the implant was assessed in the first months after surgery, a solid osteal integration did not appear. As risk factors for an implant loosening were determined:a missing reconstruction of the defect behind the pedestal cup with allogenous bone graft(p = 0.002), a lateralisation of the rotation centre(p = 0.023), the absence of the craniolateral wall (p = 0.002) and the presence of osteoporosis(p = 0.026). CONCLUSION: The pedestal cup is an implant that is well usable in many high-grade acetabular defect situations with good mid-term results; however,contraindications do exist. In cases with a significant osteoporosis, a missing sclerosis of the cranial acetabulum as well as extended damage of the lateral ilium and its absence, respectively, alternative procedures should be considered.

[Accuracy of determination of the hip centre in navigated total knee arthroplasty]. / Genauigkeit der Bestimmung des Hüftgelenkszentrums bei der Kniegelenksnavigation.

AIM: In navigated knee arthroplasty the hip centre is determined by rotary motion of the femur (pivoting). The accuracy of this functional hip centre determination in vivo is unclear. In the following paper the accuracy of pivoting in the determination of the hip centre was examined. METHODS: Navigated (TC-PLUS, Solution, PLUS Orthopedics) total knee arthroplasty (PI Galileo, PLUS Orthopedics) was performed on 25 patients with primary arthritis of the knee joint. The position of the femoral component and the hip centre were postoperatively determined by computer tomography. Through comparison with the intraoperatively documented data, the deviation of the pivoted from the true hip centre in the frontal and sagittal planes was calculated. The degree of arthritis of the hip was determined on plain radiographs according to Kellgren. RESULTS: The mean deviation was determined to 1.0 +/- 0.7 degrees in the frontal plane and 2.5 +/- 1.6 degrees in the sagittal plane (p = 0.002). This corresponds to a mean overall deviation of 20 +/- 10 mm. The data were continuously, non-parametrically distributed without any outliers. A great range of motion (ROM) in the frontal as well as sagittal planes during pivoting resulted in a less accurate determination of the hip centre. There was no correlation to the degree of arthritis of the hip. CONCLUSION: The results indicate a recommendable ROM during pivoting for maximal accuracy of hip centre determination of 20 to 30 degrees in the sagittal plane and 30 to 40 degrees in the frontal plane. Arthritis of the hip is not a contraindication for functional determination of the hip centre.

[Variance of identification of femoral epicondyles in navigated total knee arthroplasty]. / Varianz der Epikondylenerfassung bei der navigierten Knieendoprothesenimplantation.

BACKGROUND: The aims of this study were the quantification of the accuracy of registration of the epicondylar axis (EA) in navigated total knee arthroplasty (TKA) and the identification of presumed factors influencing this accuracy. METHODS: A total of 32 navigated TKAs were performed and the surgical EA registered. Postoperatively, the difference from the surgical EA determined by computed tomography was calculated. Presumed factors influencing the accuracy were sex, preoperative malalignment, stability and range of motion, operated side, body mass index, and component size. RESULTS: The absolute error was calculated to be 1.4+/-1.3 degrees . Alignment according to the intraoperatively defined axes would have resulted in three outliers (>3 degrees malalignment). The operated side was the only factor showing a significant effect on the accuracy. The absolute error in left knee joints was calculated to be 0.9+/-0.7 degrees (max. 2.4 degrees ) and in right knee joints to be 2.0+/-1.5 degrees (max. 5 degrees, p=0.021). CONCLUSIONS: The surgeon stood on the patient's right side in every case, so that right knee joints were operated from the lateral and left ones from the medial side. A medial position of the surgeon to the knee joint during registration of EA is recommended because it results in a higher accuracy than a lateral position.

[Reduction of arthrosis associated knee pain through a single intra-articular injection of synthetic hyaluronic acid]. / Die einmalige intraartikuläre Injektion eines synthetischen Hyaluronsäurepräparates reduziert arthroseassoziierte Kniegelenkschmerzen.

AIM: Conventional hyaluronic acids need three to five injections for therapeutic success, whereas Durolane), a synthetic hyaluronic acid, needs only a single injection. Clinical outcome using Durolane should be compared with the results of studies using hyaluronic acids or glucocorticoids. METHOD: Fifty patients with primary gonarthrosis stages I-III (Kellgren Score) were investigated for knee function, pain intensity, and quality of life. The knee and osteoarthritis outcome score (KOOS), visual analogue scale (VAS), and European quality of live score (EQ-5D), as well as motion of the knee were measured. Patients were investigated before, and 2, and 24 weeks after injection. RESULTS: Two weeks after injection, the subjective function of knee and quality of life had increased significantly. In the following 22 weeks, all parameters increased significantly (quality of life and activity +19%; range of motion active 109 vs. 115 degrees ; pain, 55 vs. 41 mm (VAS); all p<0.01). CONCLUSION: We conclude that a single injection of Durolane can reduce arthrosis associated knee pain sufficiently. Our data are comparable with those published in clinical studies using other hyaluronic acids. The effects of Durolane are delayed but more sustained compared than those found for glucocorticoids. Because of the single injection, we see an advantage in using Durolane compared to other conventional hyaluronic acids and glucocorticoids.

[Axial correction in knee revision arthroplasty]. / Achskorrektur bei Knietotalendoprothesenrevisionen.

Implant malalignment is a major cause for early loosening, increased wear, painful limitation of motion, and patient dissatisfaction in total knee arthroplasty. Validated diagnostic algorithms and a deeper understanding of the pathological mechanisms underlying functional deficits and pain resulting from malalignment explain the increasing number of revision operations on unloosened prostheses, which are now nearly as common as revisions for implant loosening. Common reasons are component malpositioning are a shifted joint line, or a non-physiological patella position. The success of any revision procedure basically depends on: (1) correct component positioning, (2) equal and symmetrical flexion and extension gaps, (3) restoration of joint line, and (4) a physiological patella height. The adequate grade of implant constraint has to be determined intra-operatively. A higher loosening rate of constrained implants as well as increased wear and painful limitation of motion in case of instability have to be taken into account. In the present work, a diagnostic and therapeutic algorithm for malalignment of knee prostheses is presented.

[Secondary hypertrophic osteoarthropathy in colitis ulcerosa--a case demonstration]. / Sekundäre hypertrophe Osteoarthropathie bei Colitis ulcerosa -- eine Falldemonstration.

We report the case of a patient suffering from ulcerative colitis with secondary hypertrophic osteoarthropathy. We describe the pathological findings and present a model of the pathogenesis in the Strümpell-Pierre-Marie-Bamberger syndrome.