[Modified mini-Hardinge access for hip prosthesis implantation in the supine position]. / Modifizierter Mini-Hardinge-Zugang zur Implantation von Hüftgelenksprothesen in Rückenlage.

OBJECTIVE: Total hip arthroplasty with a minimal-incision technique that can be performed in the widely used supine position. The accustomed and good overview of this position allows safe positioning of the implant and combines this with the advantage of a soft tissue preserving technique. All standard instruments and implants can be further applied. INDICATIONS: Primary and secondary coxarthrosis, femoral head necrosis. CONTRAINDICATIONS: Revision surgery, severe anatomic deformity, implantation of hip resurfacing arthroplasty. SURGICAL TECHNIQUE: Supine position. The skin incision runs from the innominate tubercle proximally and falls slightly in the dorsal direction (20-30°). Incision of the iliotibial tract and exposure of the vastogluteal muscle sling. Starting from the greater trochanter, the sinewy onset of the minimal and medium gluteal muscle is split with an arched-shaped incision, which also falls proximally in the dorsal direction. Exposition of the joint capsule, longitudinal incision and resection of the ventrolateral parts. Dislocation of the hip by a combined adduction and external rotation movement. Osteotomy of the femoral neck and resection of the femoral head are performed in a figure-of-four position without adduction. To prepare the acetabulum and to insert the cup, the leg is placed in neutral position with a slight flexion of 20° in the hip. Preparation of the femur and implantation of the stem is again performed in a figure-of-four position in adduction. Reduction of the hip and stepwise wound closure. POSTOPERATIVE MANAGEMENT: Mobilization on postoperative day 1. Starting with half weight bearing and after completed wound healing rapid increase to full weight bearing. Intensive physiotherapy and rehabilitation. Thrombosis prophylaxis according to guidelines. RESULTS: The mini-incision approach has successfully been used in our clinic for years. Between September 2004 and November 2005, the less-invasive technique was evaluated in a randomized controlled trial with 51 patients (52 hips). Compared to the standard approach a significantly shorter incision length (8.9 vs. 14.0 cm) and a slightly lower blood loss (502 vs. 660 ml) were observed for the modified mini-Hardinge. Moreover, the mini-incision group showed slightly better functional results in the early course. A higher rate of implant malpositioning or a higher peri- and postoperative complication rate was not observed.

[Characteristics of 200 patients with suspected implant allergy compared to 100 symptom-free arthroplasty patients]. / Charakteristika von 200 Patienten mit Verdacht auf Implantatallergie im Vergleich zu 100 beschwerdefreien Endoprothesenträgern.

BACKGROUND: Data on implant allergies are incomplete; therefore, we compared the data on allergy history, patch test (PT) and lymphocyte transformation test (LTT) results in a patient series from the Munich implant allergy outpatient department with symptom-free arthroplasty patients. PATIENTS AND METHODS: In this study 200 arthroplasty patients with complaints involving the prosthesis (130 female, 187 knee and 13 hip prostheses) and in parallel 100 symptom-free patients (75 female, 47 knee and 53 hip prostheses) were investigated. A questionnaire-aided history including implant type, cementing, intolerance of dental materials, atopy, cutaneous metal intolerance (CMI) and PT, including a standard series with Ni, Co, Cr, seven bone cement components, including gentamicin and benzoyl peroxide and LTT for Ni, Co and Cr. RESULTS: In the knee arthroplasty patients with complaints 9.1% showed dental material intolerance, 23.5% atopy, 25.7% CMI, 18.2% metal allergies, 7.4% gentamicin allergy and 27.8% positive metal LTT (mostly to Ni). In symptom-free patients 0% showed dental material intolerance, 19.1% atopy, 12.8% CMI, 12.8% metal allergy, 0% gentamicin allergy and 17% positive metal LTT. CONCLUSIONS: Characteristics of the patients with complaints were increased intolerance of dental materials, higher rates of atopy, CMI, metal and gentamicin allergy and LTT reactivity.

Levels of Cr, Co, Ni and Mo in erythrocytes, serum and urine after hip resurfacing arthroplasty.

BACKGROUND: Hip resurfacing arthroplasty is known to increase the metal ion concentration in the serum, urine and whole blood, with potentially adverse effects on the organism. However, only few data are available about the metal ion concentrations in erythrocytes, although they are directly exposed to the higher concentrations of the serum. METHODS: The ion levels of chromium, cobalt, nickel and molybdenum in erythrocytes of 25 patients with a hip resurfacing implant were analysed with high resolution ICP-sf-MS (inductively-coupled-plasma-sector-field-mass-spectrometry). The results were compared to the ion levels in the serum and urine of the patients, and also to the ion levels of 27 control persons without an implant. RESULTS: Compared to the control group, ion levels in the erythrocytes of the hip resurfacing group were markedly increased for cobalt (0.10 vs. 3.26 microg/kg) and slightly for chromium (6.04 vs. 7.38 microg/kg). In contrast, ion levels in the serum of the hip resurfacing group were increased for cobalt (0.21 vs. 1.92 microg/l), chromium (1.48 vs. 5.64 microg/l), nickel (1.53 vs. 4.25 microg/l) and molybdenum (2.17 vs. 3.78 microg/l). CONCLUSION: Ion concentrations of cobalt and chromium are also increased in erythrocytes after hip resurfacing arthroplasty. Further research is required to evaluate the impact of the elevated ion levels on the erythrocytes, and to evaluate if metal ions also accumulate in other tissues of the body.

[Implant position of total hip arthroplasty shafts. Establishment of a new method for comparison between planned and achieved shaft positions]. / Implantatposition von Hüftendoprothesenschäften. Etablierung einer neuen Methode zum Vergleich zwischen geplanter und erreichter Schaftposition.

BACKGROUND: One of the main goals of the preoperative planning of hip prostheses is adequate shaft positioning with reconstruction of leg length and offset. The purpose of this study was to compare the planned and achieved shaft positions using a modified program for migration measurement. METHODS: In 60 cases of total hip replacement the preoperative planning was compared with the postoperative radiograph using a modified version of the well-established EBRA-FCA program. The results of this new measurement were compared to conventional measurements. In 25 cases the intraobserver and interobserver reliability was determined. RESULTS: The novel measurements correlated best with the measured distance between the greater trochanter and the center of rotation and yielded the best intraobserver and interobserver reliability. In general, cementless stems had a slightly more proximal position (0.65 mm) compared to cemented stems. CONCLUSIONS: The modified program for migration measurement facilitates a reproducible and fast comparison of the planned and achieved shaft positions thus implementing an early and objective control of postoperative shaft position.

Finite element analysis of the ovine hip: development, results and comparison with the human hip.

OBJECTIVES: The ovine hip is often used as an experimental research model to simulate the human hip. However, little is known about the contact pressures on the femoral and acetabular cartilage in the ovine hip, and if those are representative for the human hip. METHODS: A model of the ovine hip, including the pelvis, femur, acetabular cartilage, femoral cartilage and ligamentum transversum, was built using computed tomography and micro-computed tomography. Using the finite element method, the peak forces were analysed during simulated walking. RESULTS: The evaluation revealed that the contact pressure distribution on the femoral cartilage is horseshoe-shaped and reaches a maximum value of approximately 6 MPa. The maximum contact pressure is located on the dorsal acetabular side and is predominantly aligned in the cranial-to-caudal direction. The surface stresses acting on the pelvic bone reach an average value of approximately 2 MPa. CONCLUSIONS: The contact pressure distribution, magnitude, and the mean surface stress in the ovine hip are similar to those described in the current literature for the human hip. This suggests that in terms of load distribution, the ovine hip is well suited for the preclinical testing of medical devices designed for the human hip.

[Contact allergy to metals and bone cement components in patients with intolerance of arthroplasty]. / Kontaktallergieraten gegen Metalle und Knochenzementbestandteile bei Patienten mit Endoprothesenunverträglichkeit.

INTRODUCTION: Complications in arthroplasty are mostly attributed to wear particle related loosening, infections or mechanical failure. There is no investigation in a large patient series giving data about the frequency of allergic reactions to metals or bone cement components in arthroplasty with complications. METHODS: In 92 patients with cemented hip or knee arthroplasty (66 patients with complications, 26 without symptoms) patch testing and medical history were evaluated. Contact allergy rates to metals and potential bone cement components were analyzed as well as type of complaints and allergy history. RESULTS: Main complaints were pain (81.8%), reduced range of motion (54.5%) and local swelling (56.1%). Contact allergy to nickel was shown in 16/66 patients (24.2%), 6.1% were allergic to cobalt and 3.0% to chromium. 21/66 patients (31.8%) showed an allergic reaction to bone cement components (gentamicin 23.8%, benzoyl peroxide 10.6%, hydroquinone 4.5%). Sensitization rates in patients without symptoms were 3.8% to nickel as well as to cobalt and chromium, and 15.4% to gentamicin. CONCLUSION: Contact allergy rates to metals and potential bone cement components are higher in arthroplasty patients with complications than in the general population.

[Cementing techniques in hip arthroplasty: an overview]. / Zementiertechnik in der Endoprothetik des Hüftgelenks: eine Ubersicht.

For decades the cemented anchorage of hip prostheses, especially for elderly patients, is the standard procedure. The cementing technique has turned out to be the determining factor for the survival of the implant. In the last few years developments in this field have been able to further improve the long-term survival. Established components of the modern cementing technique are vacuum-mixed cements, medullary canal plugs, centralising elements und the use of jet-lavages. The design of the cemented shaft depends on the more important surface finish. In the most clinical studies, polished shafts turned out to be slightly superior as compared to shafts with rough surfaces.

The compression-rotation stem: an experimental study on the primary stability of a new revision hip stem.

In revision hip arthroplasty with bone defects of the proximal femur, a well-established treatment method is reconstruction with impacted allograft spongiosa chips and cemented implantation of a polished stem. Building on this principle of impacted bone grafting, a femoral implant, which is suited to uncemented hip arthroplasty as well as for uncemented revisions, was designed. This so-called compression-rotation stem (CR stem) is collarless and has flanks which compress the impacted bone chips during implantation and thereby increase the rotational stability. To evaluate the primary stability of this new shaft after impaction grafting, the micromotion was determined using six motion transducers. Under physiological loading conditions with simulation of the muscle activities at the proximal femur the application was dynamically loaded for 15,000 cycles with 1000 +/- 500 N and afterwards for 5000 cycles with 1300 +/- 1000 N. Uncemented CR stems and the control Exeter stems were implanted in a standardized manner according to the X-Change method. Therefore they were implanted into artificial femora that had been previously resected, hollowed, and filled with impacted human spongeous bone allograft to simulate bone defects. Subsequently, the femora were loaded under identical conditions and the micromotions measured. In the majority of the implantations, no significant differences could be found. In conclusion, similar clinical results for the two stems should be expected.

[Hip dislocation following THA]. / Hüftluxation nach Hüftgelenktotalendoprothesenimplantation.

In the event of a hip dislocation following THA analysis of its mechanism is the main priority. In addition, the time since the operation and the direction of the dislocation need to be taken into account. When the cause of the dislocation is analysed the formation of the neocapsule plays a part at least in the case of early dislocations (within the first 6 weeks after the operation). Most dislocations happen during this postoperative period, and these can usually be treated nonoperatively by closed reduction with only a short period of general anaesthesia. Late dislocations (in the 7th and subsequent postoperative week) generally occur because of malpositioning or migration of the components of the prosthesis and quite often do need operative treatment. Dislocation after implantation of a total hip replacement is a serious complication; it should be treated quickly, and initially it confronts the operator with many unanswered questions, from the causes to their treatment.

Proximal loading of the femur leads to low subsidence rates: first clinical results of the CR-stem.

INTRODUCTION: A new femoral stem was developed with a design that leads to compression of cancellous bone in the calcar region which results in proximal loading. The cross-sectional design of the implant provides rotational stability. MATERIALS AND METHODS: In the first clinical investigation ten patients underwent uncemented total hip arthroplasty between January 1999 and May 1999 using the CR-stem((R)) (Implantcast GmbH, Buxtehude, Germany). Results were investigated using the Harris-hip-score (HHS) and antero-posterior and lateral radiographs. Migration was evaluated with the EBRA-FCA-method with a follow-up of 7 years. RESULTS: We demonstrated a mean subsidence rate of 2.23 +/- 1.13 mm 7 years after implantation thus providing basic data for extensive testing in a clinical environment. DISCUSSION: As small subsidence rates are regarded as predictor for superior long-term results in uncemented total hip arthroplasty according to the literature, the CR-stem shows promise for excellent long-term results.

[Prognostic factors to assess the value of arthroscopy in gonarthrosis]. / Prognostische Faktoren zur Beurteilung der Wertigkeit der ASK bei Gonarthrose.

AIM: The value of athroscopy in osteoarthritis(oa) of the knee remains uncertain. Many studies claim to prove efficacy of arthroscopy in oa of the knee, while other authors report that there is no such effect. The purpose of this study was to identify factors to predict the outcome of arthroscopy in oa of the knee. METHOD: The modified Lysholm score was used to assess the outcome of arthroscopy in 49 patients after a follow up of 2.5 yrs. This was a retrospective outcome study. RESULTS: No correlation between modified Lysholm score and patient age and gender could be detected. There were significantly better outcomes in the group of patient with no deviation of axis and in the group of patients which did not show a progression of oa of the knee in the radiographs during follow-up. Even if the patients had more severe osteoarthritis. CONCLUSION: Patient selection is an important factor for a good outcome after arthroscopy in older patients with oa of the knee. Deviation of the axis and the "activity" of the osteoarthritis at the time of surgery are predictors for outcome. There is the need to establish diagnostic tools to measure the "activity" of oa of the knee before surgery.

[Allergy towards bone cement]. / Knochenzementallergie.

Bone cements based on polymethylmethacrylate are typically used for fixation of artificial joints. Intolerance reactions to endoprostheses not explained by infection or mechanical failure may lead to allergological diagnostics, which mostly focuses on metal allergy. However, also bone cement components may provoke hypersensitivity reactions leading to eczema, implant loosening, or fistula formation. Elicitors of such reactions encompass acrylates and additives such as benzoyl peroxide, N,N-dimethyl-p-toluidine, hydroquinone, or antibiotics (particularly gentamicin). Upon repeated contact with bone cement components, e.g., acrylate monomers, also in medical personnel occasionally hand eczema or even asthma may develop. Therefore, in the case of suspected hypersensitivity reactions to arthroplasty, the allergological diagnostics should include bone cement components.

[Pre- and postoperative radioligical evaluation of knee joint endoprothesis. Orthopedist's view]. / Die prä- und postoperative radiologische Evaluation der Kniegelenkendoprothese. Aus der Sicht des Orthopäden.

The implantation of a knee arthroplasty is still a demanding operation. There is still no "golden standard" available, although a lot of guidelines have been declared. Because of this fact this article should provide the radiologist with an overview of and some background knowledge for the radiological evaluation of knee arthroplasty.

The influence of the implant size on the outcome of unconstrained total knee arthroplasty.

INTRODUCTION: The influence of implant size on the results in unconstrained total knee arthroplasty has never been investigated before. PATIENTS AND METHODS: 133 patients with unconstrained total knee arthroplasty were examined (HSS Score, Knee Society Score) with consideration of the different sizes of femoral and tibial components and the thicknesses of the tibial inlays. The medium follow up was 41.2 months (8 months to 74 months). RESULTS: Although the different component sizes gained different results, the differences were not significant. The combination of two component sizes did not lead to a significant change of the results. The results of the Knee Society Score seemed to become worse with thinner polyethylene tibial inlays although these differences were not significant. CONCLUSIONS: In conclusion, implant size had no significant influence on the outcome of total knee arthroplasty. The combination of two implant sizes showed no disadvantage.

[Macerated human hip bone preparation as a substitute for fresh frozen preparations for testing the primary stability and frictional torques of cementless hip cups]. / Mazerierte Hüftpfannenpräparate als Ersatz für fresh-frozen-Präparate zur Testung von Primärstabilität und Einschraubverhalten zementfreier Hüftpfannen.

AIM: The aim of the study was to validate macerated human acetabuli as replacement for fresh frozen preparations for testing primary stability and the screwing in moments of cementless threaded hip cups. METHOD: Three fresh frozen human pelvis were tested. One half of each pelvis was macerated whereas the other half was preserved as fresh frozen preparation. In the side of every pelvis the moments of screwing-in, the micromotions, the maximum expressing force and the maximum pull-out torque were determined. RESULTS: The screwing in moments, the maximum expressing forces and the maximum pull-out torques did not change. The micromotions were reduced to half. CONCLUSION: Considering the reduction of the micromotions, macerated human acetabuli are valid replacements for fresh frozen preparations for testing the primary stability and the screwing-in behaviour of screwed pans.

[Influence of patellofemoral osteoarthritis on functional outcome after unicondylar knee arthroplasty]. / Einfluss der Retropatellararthrose auf das funktionelle Ergebnis nach unikondylären Schlittenprothesen.

BACKGROUND: Patellofemoral osteoarthritis is generally considered a contraindication for unicondylar knee arthroplasty. Therefore, even with an intact lateral compartment, bicondylar surface replacement is preferred when patellofemoral osteoarthritis is present, despite comparatively worse functional results. In the present study, the influence of patellofemoral osteoarthritis on the outcome of the Oxford III unicondylar implant was investigated. MATERIAL AND METHODS: The HSS and the patella score according to Turba were used to retrospectively evaluate the outcome of 44 Oxford III unicondylar implants at an average follow-up of 35 months. The degree of patellofemoral osteoarthritis was radiographically graded according to the Sperner score. RESULTS: The HSS score improved to an average of 92.3 points (68-99; p<0.001 vs preoperative score). With the patella score, only good and very good results were observed. At follow-up examination almost 70% of the knees showed patellofemoral osteoarthritis of degree III-IV. No correlation was found between the functional scores and the degree of patellofemoral osteoarthritis. CONCLUSION: Radiographic patellofemoral osteoarthritis seems to have no influence on the functional outcome of the Oxford III unicondylar knee arthroplasty. Therefore, unicondylar surface replacement is indicated even with radiographic evidence of patellofemoral osteoarthritis, provided that it is clinically asymptomatic.