[Gluteal insufficiency]. / Gluteale Insuffizienz.

Gluteal insufficiency or hip abductor mechanism deficiency mainly following (revision) total hip replacement is associated with highly painful complaints and severe suffering of patients. It represents a great diagnostic and therapeutic challenge. Differentiated conservative treatment pathways, open surgical and endoscopic anatomic repair techniques with intact gluteal musculature and muscle transfer are available as salvage procedures for chronic not anatomically reconstructable mass ruptures. A stepwise diagnostic and therapeutic approach is required for restoration of the quality of life and painless or almost painless mobility of affected patients in occupation and daily life.

Fiberoptic microindentation technique for early osteoarthritis diagnosis: an in vitro study on human cartilage.

In this study, the capability of a fiber optic microindenter sensor to discriminate between healthy and slightly degenerated human articular cartilage samples is demonstrated. The purely optical indenter sensor is characterized by extremely reduced dimensions (0.125 mm in diameter and 27 mm in length) in comparison to existing indenter probes offering advantages for endoscopic deployment. The indenter sensor is intended to assist the surgeon in the identification of damaged articular cartilage. From each of seven specimens of human tibia plateau three samples showing different Outerbridge grading were extracted. On each sample stress-relaxation measurements were performed with eight indentation steps, each step being 40 µm and the relaxation of the material was observed for 240 s after each step. A viscoelastic model was used to fit the relaxation and to extract the characteristic parameters according to the model. A highly significant difference in stiffness (p value <0.01) was observed between the native (grade 0) and early diseased (grade 1) human cartilage samples demonstrating the potential of the fiber optic indenter for the diagnosis of cartilage breakdown.

The microstructure and micromechanics of the tendon-bone insertion.

The exceptional mechanical properties of the load-bearing connection of tendon to bone rely on an intricate interplay of its biomolecular composition, microstructure and micromechanics. Here we identify that the Achilles tendon-bone insertion is characterized by an interface region of ∼500 µm with a distinct fibre organization and biomolecular composition. Within this region, we identify a heterogeneous mechanical response by micromechanical testing coupled with multiscale confocal microscopy. This leads to localized strains that can be larger than the remotely applied strain. The subset of fibres that sustain the majority of loading in the interface area changes with the angle of force application. Proteomic analysis detects enrichment of 22 proteins in the interfacial region that are predominantly involved in cartilage and skeletal development as well as proteoglycan metabolism. The presented mechanisms mark a guideline for further biomimetic strategies to rationally design hard-soft interfaces.

Osteoinduction and -conduction through absorbable bone substitute materials based on calcium sulfate: in vivo biological behavior in a rabbit model.

Calcium sulfate (CS) can be used as an antibiotically impregnated bone substitute in a variety of clinical constellations. Antibiotically loaded bone substitutes find specific application in orthopedic and trauma surgery to prevent or treat bone infections especially in relation to open bone defects. However, its use as a structural bone graft reveals some concerns due to its fast biodegradation. The addition of calcium carbonate and tripalmitin makes CS formulations more resistant to resorption leaving bone time to form during a prolonged degradation process. The aim of the present study was the evaluation of biocompatibility and degradation properties of newly formulated antibiotically impregnated CS preparations. Three different types of CS bone substitute beads were implanted into the tibial metaphysis of rabbits (CS dihydrate with tripalmitin, containing gentamicin (Group A) or vancomycin (Group B); Group C: tobramycin-loaded CS hemihydrate). Examinations were performed by means of x-ray, micro-computed tomography (micro-CT) and histology after 4, 6, 8 and 12 weeks. Regarding biocompatibility of the formulations, no adverse reactions were observed. Histology showed formation of vital bone cells attached directly to the implanted materials, while no cytotoxic effect in the surrounding of the beads was detected. All CS preparations showed osteogenesis associated to implanted material. Osteoblasts attached directly to the implant surface and revealed osteoid production, osteocytes were found in newly mineralized bone. Group C implants (Osteoset®) were subject to quick degradation within 4 weeks, after 6-8 weeks there were only minor remnants with little osteogenesis demonstrated by histological investigations. Group A implants (Herafill®-G) revealed similar degradation within atleast 12 weeks. In contrast, group B implants (CaSO4-V) were still detectable after 12 weeks with the presence of implant-associated osteogenesis atlatest follow-up. In all of these preparations, giant cells were found during implant degradation on surface and inside of resorption lacunae. None of the analyzed CS preparations triggered contact activation. All implants demonstrated excellent biocompatibility, with implants of Group A and B showing excellent features as osteoconductive and -inductive scaffolds able to improve mechanical stability.

Antimicrobial Formulations of Absorbable Bone Substitute Materials as Drug Carriers Based on Calcium Sulfate.

Substitution of bones is a well-established, necessary procedure to treat bone defects in trauma and orthopedic surgeries. For prevention or treatment of perioperative infection, the implantation of resorbable bone substitute materials carrying antibiotics is a necessary treatment. In this study, we investigated the newly formulated calcium-based resorbable bone substitute materials containing either gentamicin (CaSO4-G [Herafill-G]), vancomycin (CaSO4-V), or tobramycin (Osteoset). We characterized the released antibiotic concentration per unit. Bone substitute materials were implanted in bones of rabbits via a standardized surgical procedure. Clinical parameters and levels of the antibiotic-releasing materials in serum were determined. Local concentrations of antibiotics were measured using antimicrobial tests of bone tissue. Aminoglycoside release kinetics in vitro per square millimeter of bead surface showed the most prolonged release for gentamicin, followed by vancomycin and, with the fastest release, tobramycin. In vivo level in serum detected over 28 days was highest for gentamicin at 0.42 µg/ml, followed by vancomycin at 0.11 µg/ml and tobramycin at 0.04 µg/ml. The clinical parameters indicated high biocompatibility for materials used. None of the rabbits subjected to the procedure showed any adverse reaction. The highest availability of antibiotics at 14.8 µg/g on day 1 in the cortical tibia ex vivo was demonstrated for gentamicin, decreasing within 14 days. In the medulla, vancomycin showed a high level at 444 µg/g on day 1, decreasing continuously over 14 days, whereas gentamicin decreased faster within the initial 3 days. The compared antibiotic formulations varied significantly in release kinetics in serum as well as locally in medulla and cortex.

Pull-out stability of anchors for rotator cuff repair is also increased by bio-absorbable augmentation: a cadaver study.

INTRODUCTION: Osteoporosis is a highly focused issue in current scientific research and clinical treatment. Especially in rotator cuff repair, the low bone quality of patients suffering from osteoporosis is an important issue. In this context, non-biological solutions using PMMA for anchor augmentation have been developed in the recent past. The aim of this study was to evaluate whether augmentation of suture anchors using bio-absorbable osteoconductive fiber-reinforced calcium phosphate results in improved failure load of suture anchors as well. MATERIALS AND METHODS: Altogether 24 suture anchors (Corkscrew FT 1 Suture Anchors, Arthrex, Naples, FL, USA) were evaluated by applying traction until pullout in 12 paired fresh frozen human cadaver humeri using a servo-hydraulic testing machine. Inclusion criteria were an age of more than 64 years, a macroscopically intact RC and an intact bone. The anchors were evaluated at the anterolateral and posteromedial aspect of the greater tuberosity. 12 suture anchors were augmented and 12 suture anchors were conventionally inserted. RESULTS: The failure load was significantly enhanced by 66.8 % by the augmentation method. The fiber-reinforced calcium phosphate could be easily injected and applied. CONCLUSION: The bio-absorbable cement in this study could be a promising augmentation material for RC reconstructions, but further research is necessary-the material has to be evaluated in vivo.

In vitro evaluation of novel antimicrobial coatings for surgical sutures using octenidine.

BACKGROUND: Sutures colonized by bacteria represent a challenge in surgery due to their potential to cause surgical site infections. In order to reduce these type of infections antimicrobially coated surgical sutures are currently under development. In this study, we investigated the antimicrobial drug octenidine as a coating agent for surgical sutures. To achieve high antimicrobial efficacy and required biocompatibility for medical devices, we focused on optimizing octenidine coatings based on fatty acids. For this purpose, antimicrobial sutures were prepared with either octenidine-laurate or octenidine-palmitate at 11, 22, and 33 µg/cm drug concentration normalized per length of sutures. Octenidine containing sutures were compared to the commercial triclosan-coated suture Vicryl® Plus. The release of octenidine into aqueous solution was analyzed and long-term antimicrobial efficacy was assessed via agar diffusion tests using Staphylococcus aureus. For determining biocompatibility, cytotoxicity assays (WST-1) were performed using L-929 mouse fibroblasts. RESULTS: In a 7 days elution experiment, octenidine-palmitate coated sutures demonstrated much slower drug release (11 µg/cm: 7%; 22 µg/cm: 5%; 33 µg/cm: 33%) than octenidine-laurate sutures (11 µg/cm: 82%; 22 µg/cm: 88%; 33 µg/cm: 87%). Furthermore sutures at 11 µg/cm drug content were associated with acceptable cytotoxicity according to ISO 10993-5 standard and showed, similar to Vicryl® Plus, relevant efficacy to inhibit surrounding bacterial growth for up to 9 days. CONCLUSIONS: Octenidine coated sutures with a concentration of 11 µg/cm revealed high antimicrobial efficacy and biocompatibility. Due to their delayed release, palmitate carriers should be preferred. Such coatings are candidates for clinical testing in regard to their safety and efficacy.

[The bovine cartilage punch model: a tool for the in vitro analysis of biomaterials and cartilage regeneration]. / Das bovine Knorpelstanzenmodell : Ein Werkzeug zur In-vitro-Analyse von Biomaterialien und Knorpelregeneration.

BACKGROUND: The limited regeneration capacity of hyaline articular cartilage requires detailed studies concerning the tissue integration of cartilage transplants with meaningful but time and/or resource-consuming and in part ethically problematic animal models or, alternatively, with in vitro test systems for implant materials. MATERIAL AND METHODS: The present study describes a regeneration model with bovine cartilage rings (outer Ø 6 mm, central defect Ø 2 mm) for insertion, cultivation and biomechanical or histological testing of cartilage replacement materials (HE and safranin O staining). In this study, resorbable polymers composed of polyglycolic acid (PGA) were analyzed. RESULTS: Biomechanical testing showed a continuous decrease of the push-out force for the PGA inserts from the cartilage rings, probably due to the resorbability of the material. Histologically, clear immigration of cells into cell-free PGA was observed even after 4 weeks of culture, but in particular after 10 weeks. In addition, storage of proteoglycans was interpreted as an initial sign of the formation of new matrix. CONCLUSION: Thus, the new regeneration model is in principle suitable for the testing of biomaterials, but shows limitations in assessing the "lateral bonding" of resorbable materials.

[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.

Morphometric differences between the medial and lateral meniscus in healthy men - a three-dimensional analysis using magnetic resonance imaging.

The objective of this work was to characterize tibial plateau coverage and morphometric differences of the medial (MM) and lateral meniscus (LM) in a male reference cohort using three-dimensional imaging. Coronal multiplanar reconstructions of a sagittal double-echo steady state with water excitation magnetic resonance sequence (slice thickness: 1.5 mm, and in-plane resolution: 0.37 × 0.70 mm) were analyzed in 47 male participants without symptoms, signs or risk factors of knee osteoarthritis of the reference cohort of the Osteoarthritis Initiative. The medial and lateral tibial (LT) plateau cartilage area and the tibial, femoral and external surfaces of the MM and LM were manually segmented throughout the entire knee. This process was assisted by parallel inspection of a coronal intermediately weighted turbo spin echo sequence. Measures of tibial coverage, meniscus size, and meniscus position were computed three-dimensionally for the total menisci, the body, and the anterior and the posterior horn. The LM was found to cover a significantly greater (p < 0.001) proportion of the LT plateau (59 ± 6.8%) than the MM of the medial plateau (50 ± 5.5%). Whereas the volume of both menisci was similar (2.444 vs. 2.438 ml; p = 0.92), the LM displayed larger tibial and femoral surface areas (p < 0.05) and a smaller maximal (7.2 ± 1.0 vs. 7.7 ± 1.1 mm; p < 0.01) and mean thickness (2.7 ± 0.3 vs. 2.8 ± 0.3 mm; p < 0.001) than the medial one. Also, the LM displayed less (physiological) extrusion than the medial one. These data may guide strategies for meniscal tissue engineering and transplantation aiming to restore normal joint conditions.

Novel fatty acid gentamicin salts as slow-release drug carrier systems for anti-infective protection of vascular biomaterials.

Infections of vascular prostheses are still a major risk in surgery. The current work presents an in vitro evaluation of novel slow release antibiotic coatings based on new gentamicin fatty acid salts for polytetrafluoroethylene grafts. These grafts were coated with gentamicin sodium dodecyl sulfate, gentamicin laurate and gentamicin palmitate. Drug release kinetics, anti-infective characteristics, biocompatibility and haemocompatibility of developed coatings were compared to commercially available gelatin sealed PTFE grafts (SEALPTFE™) and knitted silver coated Dacron(®) grafts (InterGard(®)). Each gentamicin fatty acid coating showed a continuous drug release in the first eight hours followed by a low continuous release. Grafts coated with gentamicin fatty acids reduced bacterial growth even beyond pathologically relevant high concentrations. Cytotoxicity levels depending on drug formulation bringing up gentamicin palmitate as the most promising biocompatible coating. Thrombelastography studies, ELISA assays and an amidolytic substrate assay confirmed haemocompatibility of developed gentamicin fatty acid coatings comparable to commercially available grafts.

Evaluation of a new optical measuring system for experiments on fractured human mandibles: a biomechanical feasibility study in maxillofacial surgery.

OBJECTIVES: Biomechanical loading on human mandibles was performed and a new optical measurement device was introduced for the quantification of interfragmentary movement in fractured mandibles stabilized with different osteosynthesis systems. MATERIALS AND METHODS: Comparison tests were performed with monocortical non-locking double plates and bicortical single locking plate. For the experiments on a specialized test bench, 18 ex vivo fractured human cadaveric mandibles were tested. Interfragmentary motion was detected in all three spatial dimensions using the optical measurement device PONTOS®. The movement was investigated over increasing incisal force and one summarized parameter was investigated. RESULTS: For the maximal tested load of 300 N m, the resultant interfragmentary movements in the two investigated groups were 2.96 ± 1.85° for the fixation with two conventional miniplates (six hole, profile 1.0 mm) and 4.53 ± 2.49° for single bicortically fixed locking plates (four hole, profile 1.5 mm). For both plate systems, we used the 2.0 mm screw system. CONCLUSIONS: The test bench in combination with the new optical device PONTOS(®) can test the primary stability of osteosynthesis. We offer a solution to the problem of rate of twist of the mandible as well as typical rotational problem in recent measurements. Further, the method can be used for development of new osteosynthesis products. CLINICAL RELEVANCE: Pseudoarthrosis formation is a common problem based on unsatisfying fixation of the fracture gap. The here presented combination of mechanical tests and numerical simulations can provide support for an improved treatment of fractured mandibles.

[Joint-preserving surgery of the adult hip. Intertrochanteric femoral osteotomy]. / Gelenkerhaltende Hüftchirurgie im Erwachsenenalter. Intertrochantäre Femurosteotomie.

Due to advances in total joint replacement, intertrochanteric osteotomy (ITO) is performed more infrequently in spite of good clinical results. Nevertheless, there are several good indications for this joint-preserving procedure in adults. Detailed biomechanical knowledge and precise clinical examination are prerequisites for correct indications and planning of ITO. The main target of this surgical procedure is improvement of joint congruency and normalization of load transfer to protect damaged cartilage. Very good results can be obtained in hip dysplasia, non-union of the femoral neck and proximal femoral deformities if the therapeutic principles are followed. Higher failure rates have to be expected in femoral head necrosis and osteoarthritis, depending on the degree of pre-existing cartilage damage.

[Design of a high-dynamic closed-loop controlled cartilage test system]. / Hochdynamisches Prüfsystem zur biomechanischen Charakterisierung von Knorpel und seinen Regeneraten.

Articular cartilage repair methods, in particular scaffold-based autologous chondrocyte implantation, are already in clinical use. In the coming years, the European guidelines on human cell-based medicinal products by the European Medical Agency (EMA) will extend today's quality control mechanisms by additional structural analyses. As articular cartilage has complex biphasic and viscoelastic mechanical properties, a high-performance material test system is required and has already been implemented. To characterize the recovery of cartilage and cartilage replacement materials, it is necessary to measure the dynamic recovery profile. A measurement system for an application like this requires an axis acceleration of more then 50 m/s(2). Furthermore, the test system needs custom-made components to fix the biological specimen while testing. A software package consisting of a graphical user interface and an axis controller leads to highly reproducible tests. The software makes use of a position and velocity controller as well as a force controller at kilohertz speed. While using the high performance force controller it is possible to apply static and dynamic loading profiles that are independent from position or speed set points and signals.

Augmentation of antibiotic activity by low-frequency electric and electromagnetic fields examining Staphylococcus aureus in broth media.

Systemic treatment of biomaterial-associated bacterial infections with high doses of antibiotics is an established therapeutic concept. The purpose of this in vitro study was to determine the influence of magnetic, electromagnetic, and electric fields on gentamicin-based, antibiotic therapy. It has been previously reported that these fields are successful in the treatment of bone healing and reducing osteitis in infected tibia-pseudarthroses. Four separate experimental setups were used to expose bacterial cultures of Staphylococcus aureus both in Mueller-Hinton broth (MHB) and on Mueller-Hinton agar (MHA), in the presence of gentamicin, to (1) a low-frequency magnetic field (MF) 20 Hz, 5 mT; (2) a low-frequency MF combined with an additional alternating electric field (MF + EF) 20 Hz, 5 mT, 470 mV/cm; (3) a sinusoidal alternating electric field (EF AC) 20 Hz, 470 mV/cm; and (4) a direct current electric field (EF DC) 588 mV/cm. No significant difference between samples and controls was detected on MHA. However, in MHB each of the four fields applied showed a significant growth reduction of planktonically grown Staphylococcus aureus in the presence of gentamicin between 32% and 91% within 24 h of the experiment. The best results were obtained by a direct current EF, decreasing colony-forming units (CFU)/ml more than 91%. The application of electromagnetic fields in the area of implant and bone infections could offer new perspectives in antibiotic treatment and antimicrobial chemotherapy.

Novel method for reduction of virus load in blood plasma by sonication.

BACKGROUND: Aim of the present study is the evaluation of ultrasound as a physical method for virus inactivation in human plasma products prior to transfusion. Our study is focused on achieving a high level of virus inactivation simultaneously leaving blood products unaltered, measured by the level of degradation of coagulation factors, especially in third world countries where virus contamination of blood products poses a major problem. Virus inactivation plays an important role, especially in the light of newly discovered or unknown viruses, which cannot be safely excluded via prior testing. METHODS: Taking into account the necessary protection of the relevant coagulation activity for plasma, the basis for a sterile virus inactivation under shielding gas insufflation was developed for future practical use. Influence of frequency and power density in the range of soft and hard cavitation on the inactivation of transfusion-relevant model viruses for Hepatitis-(BVDV = bovine diarrhea virus), for Herpes-(SFV = Semliki Forest virus, PRV = pseudorabies virus) and Parvovirus B19 (PPV = porcine parvovirus) were examined. Coagulation activity was examined via standard time parameters to minimize reduction of functionality of coagulation proteins. A fragmentation of coagulation proteins via ultrasound was ruled out via gel electrophoresis. The resulting virus titer was examined using end point titration. RESULTS: Through CO2 shielding gas insufflation-to avoid radical emergence effects-the coagulation activity was less affected and the time window for virus inactivation substantially widened. In case of the non-lipidated model virus (AdV-luc = luciferase expressing adenoviral vector), the complete destruction of the virus capsid through hard cavitation was proven via scanning electron microscopy (SEM). This can be traced back to microjets and shockwaves occurring in hard cavitation. The degree of inactivation seems to depend on size and compactness of the type of viruses. Using our pre-tested and subsequently chosen process parameters with the exception of the small PPV, all model viruses were successfully inactivated and reduced by up to log 3 factor. For a broad clinical usage, protection of the coagulation activities may require further optimization. CONCLUSIONS: Building upon the information gained, an optimum inactivation can be reached via raising of power density up to 1200 W and simultaneous lowering of frequency down to 27 kHz. In addition, the combination of the two physical methods UV treatment and ultrasound may yield optimum results without the need of substance removal after the procedure.

Discrimination between healthy and degenerated bovine articular cartilage with a fiber Bragg grating based microindenter.

OBJECTIVE: In this study we aim to show that an optical fiber Bragg grating-based microindentation system, which has the potential to be deployed arthroscopically, can differentiate between healthy and degenerated articular cartilage, which represents an important challenge in minimally-invasive surgery. DESIGN: Twenty bovine osteochondral cylinders, extracted from the patellar groove of ten 24 months old animals were subjected to stepwise in vitro stress-relaxation indentation measurements. The indentation procedure comprised 15 indentation steps of 20 µm each, reaching a total depth of 300 µm. Ten samples remained untreated and served as a control group for healthy cartilage. A second group of ten samples was treated for 12 h with an aqueous trypsin solution (concentration 2.5%) to deplete the proteoglycans. For both groups and all indentation depths deeper than 100 µm, the step response functions of a two elements Maxwell-Wiechert model fitted well to the measured relaxation curves. RESULTS: The standard deviations of the identified stiffness parameters within each group were much smaller than the difference of the average stiffness values between both groups. Based on the measured stiffness values, the system was capable to discriminate between healthy and degenerated cartilage with a high level of significance (p < 0.001). The experimental results are also discussed in terms of the biomechanical changes of cartilage under the action of trypsin. CONCLUSION: The fiber Bragg grating microindentation system showed the capability to differentiate intact and proteoglycan depleted cartilage with high significance.

Osteochondrosis juvenilis of the medial malleolar epiphysis.

Osteochondrosis juvenilis is caused by a dysfunction of endochondral ossification. Several epiphyses and apophyses can be affected, but osteochondrosis juvenilis of the medial malleolus has not been reported. We describe a 12-year-old boy with bilateral pes planovalgus who was affected by this condition. Conservative management was successful. The presentation, aetiology and treatment are described and the importance of including it in the differential diagnosis is discussed.

[Surgical therapy of ischiofemoral impingement by lateralizing intertrochanteric osteotomy]. / Chirurgische Therapie des ischiofemoralen Impingements mittels lateralisierender intertrochantärer Korrekturosteotomie.

OBJECTIVE: Lateralizing, derotating intertrochanteric varus osteotomy to increase the ischiofemoral space to counter painful impingement of the lesser trochanter and the os ischium with resulting entrapment of quadratus femoris muscle. INDICATIONS: Symptomatic ischiofemoral impingement (IFI) caused by Coxa valga et antetorta, Coxa valga or Coxa antetorta, or a short femoral neck. CONTRAINDICATIONS: Anatomic configuration suggestive of IFI in asymptomatic patients. Symptomatic IFI caused by another underlying pathology. Valgus deformity of the knee. SURGICAL TECHNIQUE: Measurement of femoral antetorsion. Planning of the osteotomy, lateralization, varus angle for correction, rotation and offset correction, leg length change, and osteosynthesis plate. General or spinal anesthesia in supine or lateral position. Skin incision (15 cm) beginning lateral of the greater trochanter tip, distally along the axis of the femur. Preparation onto the femur by L­shaped dissection of the vastus lateralis from the bone. A Kirschner(K-)wire is then positioned along the anterior femoral neck to designate the femoral neck antetorsion. A triangle set on the lateral femoral cortexis is used to determine the osteotomy angle. In the thus determined angle, a second K­wire is shot centrally along the femoral neck axis just inferior to its cranial cortex. About 5 mm distal to the second wire, the entry for the blade is prepared using a drill. Using the blade setting instrument, the blade is introduced into the femoral neck, then slightly pulled back. The rotation is then marked on the anterior femoral cortex proximal and distal to the planned osteotomy and the osteotomy is performed. A blade plate without displacement is impacted. The osteotomy is then reduced, the distal fragment pulled laterally onto the plate, and the screws inserted after compression of the osteotomy with a tension device. POSTOPERATIVE MANAGEMENT: Touch-toe bearing for 6 weeks, then radiological assessment of osteotomy healing before an increase in weight bearing (15 kg/week). Hip flexion limited to 90° for 6 weeks. Elective implant removal after 12-18 months. RESULTS: Studies of this lateralizing varus osteotomy have not been published. The 25-year results of the conventional derotating intertrochanteric varus osteotomy technique show good functional results and low complication rates, with non-union being the most common. Arthroscopic resection of the lesser trochanter has been reported as a surgical alternative in the treatment of IFI in case reports and small series. Advantages of the osteotomy are the restoration of biomechanics and preservation of iliopsoas tendon insertion.

The natural alpha angle of the femoral head-neck junction: a cross-sectional CT study in 1312 femurs.

Aims: Asphericity of the femoral head-neck junction is common in cam-type femoroacetabular impingement (FAI) and usually quantified using the alpha angle on radiographs or MRI. The aim of this study was to determine the natural alpha angle in a large cohort of patients by continuous circumferential analysis with CT. Methods: CT scans of 1312 femurs of 656 patients were analyzed in this cross-sectional study. There were 362 men and 294 women. Their mean age was 61.2 years (18 to 93). All scans had been performed for reasons other than hip disease. Digital circumferential analysis allowed continuous determination of the alpha angle around the entire head-neck junction. All statistical tests were conducted two-sided; a p-value < 0.05 was considered statistically significant. Results: The mean maximum alpha angle for the cohort was 59.0° (sd 9.4). The maximum was located anterosuperiorly at 01:36 on the clock face, with two additional maxima of asphericity at the posterior and inferior head-neck junction. The mean alpha angle was significantly larger in men (59.4°, sd 8.0) compared with women (53.5°, sd 7.4°; p = 0.0005), and in Caucasians (60.7°, sd 9.0°) compared with Africans (56.3°, sd 8.0; p = 0.007) and Asians (50.8°, sd 7.2; p = 0.0005). The alpha angle showed a weak positive correlation with age (p < 0.05). If measured at commonly used planes of the radially reconstructed CT or MRI, the alpha angle was largely underestimated; measurement at the 01:30 and 02:00 positions showed a mean underestimation of 4° and 6°, respectively. Conclusion: This study provides important data on the normal alpha angle dependent on age, gender, and ethnic origin. The normal alpha angle in men is > 55°, and this should be borne in mind when making a diagnosis of cam-type morphology. Cite this article: Bone Joint J 2018;100-B:570-8.