Material modifications enhancing the antibacterial properties of two biodegradable poly(3-hydroxybutyrate) implants.

The aim of this study was to evaluate the antimicrobial efficacy of adding a gentamicin palmitate (GP) coating and zirconium dioxide (ZrO2) to biodegradable poly(3-hydroxybutyrate) (PHB) to reduce biofilm formation. Cylindrical pins with and without a coating were incubated in Müller-Hinton broth inoculated with 2 × 105 colony-forming units (CFU) ml-1 of Staphylococcus aureus for 2 d or 7 d, then sonicated to disrupt biofilms. Pure PHB (PHB + GP) and PHB pins with ZrO2 added (PHBzr + GP) were coated with GP and compared with PHB pins lacking a coating (PHB). Cells (CFU) were counted to quantify the number of bacteria in the biofilm and a cell proliferation assay was employed to evaluate metabolic activity, and scanning electron microscopy (SEM) was performed to visualize the structure of the biofilm. After 2 d of incubation there were significantly more cells in biofilms on PHB pins than PHB + GP and PHBzr + GP pins (p < 0.0001), and cells in the sonication fluid obtained from GP-coated pins exhibited significantly lower metabolic activity than cells from uncoated PHB pins (p < 0.0001). After 7 d of incubation metabolic activity was lowest for PHBzr + GP, with significant differences between PHB and PHBzr + GP (p = 0.001). SEM revealed more cells attached to the surface, and more structured biofilms, on pins without a coating. Coating pins with GP significantly reduced early biofilm formation on PHB implants. This could lower the potential risk of surgical site infections when using PHB implants. Addition of ZrO2 might further enhance the antibacterial properties. Such modification of the implant material should therefore be considered when developing new biodegradable PHB implants.

Results of universal ultrasound screening for developmental dysplasia of the hip: a prospective follow-up of 28 092 consecutive infants.

AIMS: The purpose of this study was to analyze the incidence of the different ultrasound phenotypes of developmental dysplasia of the hip (DDH), and to determine their subsequent course. PATIENTS AND METHODS: A consecutive series of 28 092 neonates was screened and classified according to the Graf method as part of a nationwide surveillance programme, and then followed prospectively. Abnormal hips were followed until they became normal (Graf type I). Type IIb hips and higher grades were treated by abduction in a Tübinger orthosis until normal. Dislocated hips underwent closed or open reduction. RESULTS: Overall, 90.2% of hips were normal at birth. Type IIa hips (8.9%) became normal at a median of six weeks (interquartile range (IQR) 6 to 9). Type IIc and IId hips (0.67%) became normal after ten weeks (IQR 7 to 13). There were 19 type lll and eight type lV hips at baseline. There were 24 closed reductions and one open reduction. No late presentations of DDH were detected within the first five years of life. CONCLUSION: The incidence of DDH was eight per 1000 live births. The treatment rate was 1% (n = 273). The rate of first operations on the newborn hip was 0.86, and rate of open surgery was 0.04. The cumulative rate of open surgery was 0.07. The authors take the view that early identification and treatment in abduction of all dysplastic hips in early childhood reduces the rate of open reduction and secondary DDH-related surgery later in life. Cite this article: Bone Joint J 2018;100-B:1399-1404.

[Potential of allogeneic bone grafts as antibiotic carriers : Effect of different preparation processes on efficacy]. / Allogene spongiöse Knochenpräparate als Antibiotikaträger : Einfluss verschiedener Aufbereitungsverfahren auf die Wirksamkeit.

BACKGROUND: The rising number of primary joint replacements worldwide is causing an increase of endoprosthetic revision surgery due bacterial infection. Revision surgery using non-cemented implants seems beneficial for the long-term outcome, and the use of antibiotic-impregnated bone grafts might control the infection and provide a good support for the implant. In this study, we evaluated the release of antibiotics from fresh-frozen and lyophilized allogeneic bone grafts. METHODS: Heat-treated, lyophilized and fresh frozen cryopreserved bone chips were impregnated with gentamicin sulphate, gentamicin palmitate and vancomycin, and calcium carbonate/calcium sulphate treated with antibiotics. The efficacy of each preparation was measured by drug release tests and bacterial susceptibility using B. subtilis, S. aureus and methicillin-resistant Staphylococcus aureus. RESULTS: The release of gentamicin from lyophilized bone was similar to the release rate from fresh frozen bone during the entire experiment. This might be related to the similar porosity and microstructure of the bone chips. The release of gentamicin from lyophilized and fresh frozen bone was high on the first and second days, then decreased and stayed at a low rate until the end of the second week. CONCLUSION: Depending on the surgical strategy, either polymethylmethacrylate or allogeneic bone are able to deliver sufficient concentrations of gentamicin to achieve bacterial inhibition within 2 weeks after surgery. In the case of uncemented revision of joint replacements, allogeneic bone can deliver therapeutic doses of gentamicin and peak levels immediately and a fortnight after implantation.

[Revision arthroplasty of the hip : Direct anterior approach]. / Revisionsendoprothetik des Hüftgelenks : Der anteriore Zugang.

The direct anterior approach to the hip allows good exposure of acetabulum and periacetabular bones. For simple acetabular revisions it can be chosen to be small (minimally invasive); in the case of extensive periacetabular bone loss exposure of the entire ilium cranial of the acetabulum may be achieved, and the pubic bone as well as inner-pelvic structures adjacent to the acetabulum can be exposed. The internerval plane of the approach between muscles innervated by the femoral nerve and the gluteal nerves allows exposure of the ilium without endangering the nerve supply of gluteal muscles.

[Surgical access routes to the hip joint in the elderly]. / Operative Zugangswege zur Hüfte beim älteren Menschen.

There are a large number of different approaches to the hip joint. Several conventional and minimally invasive portals exist and numerous technical variations with different instrument sets are available. All approaches can be regarded as standard and can be utilized lege artis. The main differences between approaches are their potential to preserve muscles and avoid damage which would slow down rehabilitation and mobilization. In the elderly the preservation of abductor function is, in the authors' opinion, of utmost importance. A well-functioning gluteal system provides a limp-free gait, supports joint stability and reduces the probability of dislocations. The direct anterior approach has some advantages; however, minimally invasive approaches should be used with care. Surgical experience, experience with a specific approach and the availability of specialized instruments as well as sufficient training are mandatory for a successful performance. A surgeon should always choose the approach with which he has most experience.

[Arthroscopic procedure for Baker's cysts : surgical technique. Video article]. / Arthroskopische Operation der Baker-Zyste : Operationstechnik. Videobeitrag.

BACKGROUND: Baker's cysts are related to increased intra-articular pressure. The causes may be inflammatory, degenerative or traumatic disorders. Owing to the increased intra-articular pressure a cyst protrudes between the semimembranosus and the medial gastrocnemius tendons. The traditional treatment for a Baker's cyst is open resection. As an alternative, an arthroscopic procedure can be performed, which is demonstrated by the video on surgical technique that accompanies this short report. SURGICAL TECHNIQUE: From the anterolateral portal the arthroscope is advanced through the intercondylar notch (below the posterior cruciate ligament) to the posteromedial recess. Under visual control, a posteromedial portal is created followed by identification of the capsular fold separating the cyst from the joint cavity. This fold (valvular mechanism) is resected with a shaver from the posteromedial portal until a large enough connection exists between the joint and the cyst (cyst decompression). After the decompression, the arthroscope is inserted from the posteromedial portal directly into the cyst cavity. Subsequently, the inner wall of the cyst is removed with the shaver via an additional far posterior cystic portal. It is obligatory to treat the associated intra-articular pathological condition. In our video a medial meniscal lesion is treated with partial meniscectomy.

Use of lavage fluids in arthroplasty to prevent postoperative infections.

OBJECTIVE: Lavage techniques are used every day all over the world to clean wounds and surgical approaches. The solutions used vary depending on the application range; there are, for instance, normal saline, antibiotic or antiseptic solutions. This review describes the lavage solutions actually used during arthroplasty and their outcome related to postoperative infections. DATA SOURCES AND EXTRACTION: This is a retrospective review of published articles and books. The information was obtained from online browsers for scientific articles. RESULTS: The lavage fluids used in arthroscopy and those used in experimental studies were normal saline, bacitracin, castile soap, benzalkonium chloride, povidone iodine, Ringer's solution, neomycin sulphate, ethanol, chlorhexidine gluconate, cephalothin sodium, and carbenicillin indanyl sodium. CONCLUSIONS: As few clinical studies were carried out with lavage solutions, most of the results are based on experimental studies. A "golden standard" is still missing.

Effect of storage temperature on gentamicin release from antibiotic-coated bone chips.

Freezing is the most common method for storing bones until use in skeletal reconstruction. However, the effect of freezing on antibiotic delivery from antibiotic-coated bone has not been evaluated. In this study, we compared antibiotic delivery in vitro from gentamicin-coated human bone stored at different temperatures. Bone chips obtained from human femur heads were chemically cleaned and mixed with gentamicin sulfate. Samples were stored for 4 months at -20 °C, 4 months at -80 °C, or evaluated immediately without freezing. Antibiotic release from the bone chips was measured using Bacillus subtilis as an indicator strain. Zones of inhibition and rates of gentamicin release were similar in all three groups. Storage at -20 and -80 °C for bone allografts has no effect on gentamicin release from chemically cleaned bone chips.

Effect of two cleaning processes for bone allografts on gentamicin impregnation and in vitro antibiotic release.

Bone allografts are a useful and sometimes indispensable tool for the surgeon to repair bone defects. Microbial contamination is a major reason for discarding allografts from bone banks. To improve the number of safe allografts, we suggest chemical cleaning of the grafts followed by antibiotic impregnation. Comparison of two chemical cleaning processes for bone allografts aiming for antibiotic impregnation and consequently delivery rates in vitro. Bone chips of 5-10 mm were prepared from human femoral heads. Two cleaning methods (cleaning A and cleaning B) based on solutions containing hydrogen peroxide, paracetic acid, ethanol and biological detergent were carried out and compared. After the cleaning processes, the bone chips were impregnated with gentamicin. Bacillus subtilis bioassay was used to determine the gentamicin release after intervals of 1-7 days. Differences were compared with non-parametric Mann-Whitney U tests. The zones of inhibition obtained from the bone grafts cleaned with both cleaning processes were similar between the groups. The concentration of the released antibiotic was decreasing gradually over time, following a similar pattern for both groups. The cleaning procedure A as well as the cleaning procedure B for bone allografts allowed the impregnation with gentamicin powder in the same concentrations in both groups. The delivery of gentamicin was similar for both groups. Both cleaning procedures were easy to be carried out, making them suitable for routine use at the bone banks.

[The direct anterior approach to the hip revision]. / Der direkte anteriore Zugang in der Revisionshüftendoprothetik.

OBJECTIVE: The objective of this paper is to describe a minimally invasive approach to revision total hip arthroplasty. INDICATIONS: Indications for revision hip arthroplasty are septic or aseptic loosening of one or both components of a hip arthroplasty. In revisions the direct anterior approach (DAA) allows for a small incision if only the cup has to be revised or in cases of stem revision; the femoral preparation can be performed strictly endofemorally from the proximal direction. The gluteal muscles can be preserved whether the approach is limited to the original interval between the musculus tensor fasciae latae and the rectus, or has to be extended. CONTRAINDICATIONS: If preservation of the gluteal muscles is desired, the DAA and its extension are the method of choice. For endofemoral revision other than detachment of the musculus tensor fasciae latae, hyperextension and adduction of the operated leg are important. If these cannot be achieved, an alternative operative strategy or a different approach should be considered. As this approach allows for extensions proximally and distally along the femur, it competes with lateral approaches to the hip joint and femur, and does not have additional specific contraindications. The availability of specific curved, angulated, or offset instruments is mandatory. SURGICAL TECHNIQUE: The starting point of the incision is found two fingerbreadths lateral and two finger breadths distal to the anterior superior iliac spine. The fascia of the musculus tensor fasciae latae is incised sharply at its midpoint. The interval is prepared strictly subfacially and medially to the musculus tensor fasciae latae to expose the hip joint. POSTOPERATIVE MANAGEMENT: For this approach we don't have any specific recommendations. Postoperative management depends mostly on the extension of the approach and the type of reconstruction performed. If the approach can be limited to the minimally invasive direct anterior portal, reduced muscle damage should result in faster rehabilitation. RESULTS: The retrospective analysis was performed on the data obtained from 48 revision operations with the minimally invasive direct anterior approach to total hip arthroplasty. The median cut-suture time was 108 min (42-282 min); patients spent a median time of 10 days (4-33 days) in the hospital from the day of the operation. The most common revision operations were cup replacement with an augmentation ring (13 out of 48), stem revision (11 out of 48), cup replacement (9 out of 48), H-TEP complete (3 out of 48), removing of ossifications (2 out of 48), cap revision (2 out of 48) and H-TEP removal with insertion of a spacer (2 out of 48). Complications attributed to the procedure were reported in 9 of the 48 cases: 1 wound-healing disorder, 1 late infection, 1 hematoma, 1 deep vein thrombosis, 1 perforation (by the spacer) and 1 ossification. Two patients were diagnosed with trochanteric pain syndrome. In one case an implant loosening was diagnosed 12 months after the revision.

Staphylococcus aureus biofilm formation and antibiotic susceptibility tests on polystyrene and metal surfaces.

AIM: We compared the MBEC™-HTP assay plates made of polystyrene with metal discs composed of TMZF(®) and CrCo as substrates for biofilm formation. METHODS AND RESULTS: Staphylococcus aureus was grown on polystyrene and on metal discs made of titanium and chrome-cobalt. Antibiotic susceptibility was assessed by examining the recovery of cells after antibiotic exposure and by measuring the biofilm inhibitory concentration (BIC). The minimal inhibitory concentration (MIC) was assessed with planktonic cells. Bacterial growth was examined by scanning electron microscopy. The antibiotic concentration for biofilm inhibition (BIC) was higher than the MIC for all antibiotics. Microscopic images showed the biofilm structure characterized by groups of cells covered by a film. CONCLUSIONS: All models allowed biofilm formation and testing with several antibiotics in vitro. Gentamicin and rifampicin are the most effective inhibitors of Staph. aureus biofilm-related infections. We recommend MBEC™-HTP assay for rapid testing of multiple substances and TMZF(®) and CrCo discs for low-throughput testing of antibiotic susceptibility and for microscopic analysis. SIGNIFICANCE AND IMPACT OF THE STUDY: In vitro assays can improve the understanding of biofilms and help developing methods to eliminate biofilms from implant surfaces. One advantage of the TMZF(®) and CrCo discs as biofilm in vitro assay is that these metals are commonly used for orthopaedic implants. These models are usable for future periprosthetic joint infection studies.

Impaction bone grafting: a laboratory comparison of two methods.

In revision total hip replacement, bone loss can be managed by impacting porous bone chips. In order to guarantee sufficient mechanical strength, the bone chips have to be compacted. The aim of this study was to determine in an in vitro simulation whether the use of a pneumatic hammer leads to higher primary stability than manual impaction. Bone mass characteristics were measured by force and distance variation of a penetrating punch, which was lowered into a plastic cup filled with bone chips. From these measurements bulk density, contact stiffness, impaction hardness and penetration resistance were calculated for different durations of impaction. We found that the pneumatic method reached higher values of impaction hardness, contact stiffness and bulk density suggesting an increase in stability of the implant. No significant differences were found between the two different methods concerning the penetration resistance. The pneumatic method might reduce the risk of fracture in vivo, as force peaks are smaller and applied for a shorter period. Results from manual impaction showed higher variability and depend much on the experience of the surgeon. The pneumatic hammer is a suitable tool to standardise the impaction process.

Migration of hip revision stems into the knee joint: alternative treatment modalities: technical note.

We report two unusual cases of stem penetration of long shaft femoral prosthesis into the knee joint after revision total hip arthroplasty. In both patients, the protruded tip of the stem interfered with the tibial plateau and averted the knee joint from full range of motion. To avoid further extensive surgery, the tips of the femoral stem were excised using a high speed-cutter. Both patients had immediate improvement in range of motion postoperatively, fast and uncomplicated rehabilitation, immediate pain relief, and good radiological results. If this rare complication occurs, we recommend for a primary intervention to cut the tip of the stem because replacement of the prosthesis would be a long lasting and very exhaustive surgery for affected patients.

Uncompromised quality of the cement mantle in Exeter femoral components implanted through a minimally-invasive direct anterior approach. A prospective, randomised cadaver study.

A complete cement mantle is important for the longevity of a total hip replacement. In the minimally-invasive direct anterior approach used at the Innsbruck University hospital, the femoral component has to be inserted into the femoral canal by an angulated movement. In a cadaver study, the quality and the extent of the cement mantle surrounding 13 Exeter femoral components implanted straight through a standard anterolateral transgluteal approach were compared with those of 13 similar femoral components implanted in an angulated fashion through a direct anterior approach. A third-generation cementing technique was used. The inner and outer contours of the cement mantles was traced from CT scans and the thickness and cross-sectional area determined. In no case was the cement mantle incomplete. The total mean thickness of the cement mantle was 3.62 mm (95% confidence interval 3.59 to 3.65). The mean thickness in the group using the minimally-invasive approach was 0.16 mm less than that in the anterolateral group. The distribution of the thickness was similar in the two groups. The mean thickness was less on the anteromedial and anterolateral aspect than on the posterior aspect of the femur. There is no evidence that the angulated introduction of Exeter femoral components in the direct anterior approach in cadavers compromises the quality, extent or thickness of the cement mantle.

The effect of fixation and location on the stability of the markers in navigated total hip arthroplasty: a cadaver study.

In navigated total hip arthroplasty, the pelvis and the femur are tracked by means of rigid bodies fixed directly to the bones. Exact tracking throughout the procedure requires that the connection between the marker and bone remains stable in terms of translation and rotation. We carried out a cadaver study to compare the intra-operative stability of markers consisting of an anchoring screw with a rotational stabiliser and of pairs of pins and wires of different diameters connected with clamps. These devices were tested at different locations in the femur. Three human cadavers were placed supine on an operating table, with a reference marker positioned in the area of the greater trochanter. K-wires (3.2 mm), Steinman pins (3 and 4 mm), Apex pins (3 and 4 mm), and a standard screw were used as fixation devices. They were positioned medially in the proximal third of the femur, ventrally in the middle third and laterally in the distal portion. In six different positions of the leg, the spatial positions were recorded with a navigation system. Compared with the standard single screw, with the exception of the 3 mm Apex pins, the two-pin systems were associated with less movement of the marker and could be inserted less invasively. With the knee flexed to 90 degrees and the dislocated hip rotated externally until the lower leg was parallel to the table (figure-four position), all the anchoring devices showed substantial deflection of 1.5 degrees to 2.5 degrees . The most secure area for anchoring markers was the lateral aspect of the femur.

Infection of a total hip arthroplasty with Prevotella loeschii.

Infection is a serious complication of total hip replacement. It has been proposed that 6% of all infections after total hip arthroplasty may be of dental origin through hematogenous spread. However, no conclusive evidence that the mouth is a definitive source for infection of a total hip replacement has been reported. In the current case, Prevotella loeschii, a pigmented bacteroides species was identified in a total hip replacement. Prevotella loeschii is an organism which exclusively inhabits the dental region. Hematogenous spread of Prevotella loeschii may occur after penetration of the mucosal barrier in cases of endodontic or periodontic lesions, pericoronitis, or complications of tooth extraction. The involvement of Prevotella loescheii in an infection in a patient who had a total hip arthroplasty is strong evidence for the mechanism of a hematogenous infection from a dental source.

Contamination during removal of cement in revision hip arthroplasty. A cadaver study using ultrasound and high-speed cutters.

Instruments used in surgery which rotate or vibrate at a high frequency can produce potentially contaminated aerosols. Such tools are in use in cemented hip revision arthroplasties. We aimed to measure the extent of the environmental and body contamination caused by an ultrasound device and a high-speed cutter. On a human cadaver we carried out a complete surgical procedure including draping and simulated blood flow contaminated with Staphylococcus aureus (ATCC 12600). After cemented total hip arthroplasty, we undertook repeated extractions of cement using either an ultrasound device or a high-speed cutter. Surveillance cultures detected any environmental and body contamination of the surgical team. Environmental contamination was present in an area of 6 x 8 m for both devices. The concentration of contamination was lower for the ultrasound device. Both the ultrasound and the high-speed cutter contaminated all members of the surgical team. The devices tested produced aerosols which covered the whole operating theatre and all personnel present during the procedure. In contaminated and infected patients, infectious agents may be present in these aerosols. We therefore recommend the introduction of effective measures to control infection and thorough disinfection of the operating theatre after such procedures.

Retrograde injection of a nutrient vein with cement in cemented total hip arthroplasty.

An 80-year-old woman received a cemented total hip arthroplasty. The surgery was performed without intraoperative complications. Postoperative radiographs and a computed tomography scan revealed a nutrient vein perforating the femur, which was retrogradely filled with cement. An abdominal and thoracic computed tomography scan showed no further dissemination of cement.

Knee pain caused by a fiducial marker in the medial femoral condyle: a clinical and anatomic study of 20 cases.

After 2-pin-based ROBODOC hip arthroplasty procedures, 10 of 18 patients reported persistent severe pain at the site of pin implantation in the medial femoral condyle. In a cadaver study, we found that the infrapatellar branch of the saphenous nerve, the saphenous nerve and the anterior cutaneous branches of the femoral nerve had been injured by the pins. At least one of these nerves was injured in 11 of the 20 specimens examined. Our findings indicate that the knee-pain may be partly caused by injuries to these nerves.

Multiple previous surgeries, infection, and preoperative radiation: a cause for arterial rupture in closed reduction?

We report a patient who underwent revision hip arthroplasty with preoperative radiation after a septic loosening of the primary hip prosthesis. Subsequently the patient presented with a dislocation of the hip. During the closed reduction with general anesthesia, a rupture of the arteria profunda femoris occurred. The patient was treated by angiographic obliteration of the arteria profunda femoris followed by an open reduction and augmentation of the acetabular component.