[Short hip stem for THA in avascular necrosis of the femoral head]. / Kurzschaftendoprothesen bei Osteonekrosen.

INTRODUCTION: Osteonecrosis of the femoral head or avascular necrosis of the femoral head (HKN) is a complex disease that, without treatment, leads to infraction of the femoral head in most cases. In these cases, only replacement of the hip joint will help, although there is no clear recommendation of an arthroplasty type. In the last two decades, the treatment of primary and secondary coxarthrosis with short-shaft prostheses with different anchoring philosophies has increased. Since short-shaft fitting is a possible option especially in younger patients, the question arises about possible fittings of advanced HKN with these stem types, especially with metaphyseal anchorage. The aim of this study was to review the existing literature on the results of short stem prosthesis in HKN and to present the advantages and disadvantages of short stem prosthesis in osteonecrosis of the femoral head. MATERIAL AND METHODS: This review analyzes the existing studies on short stem arthroplasty for HKN. RESULTS: Only a few studies exist that have analyzed clinical and radiologic outcomes of short stem replacement in HKN. CONCLUSION: The existing short- and medium-term results show mostly good outcomes. However, it is difficult to draw a general conclusion due to differences in stem design and fixation. Short stems with primary diaphyseal fixation do not show an increased risk of failed osseointegration or loosening. Constructions with primary metaphyseal fixation should undergo MRI to rule out the possibility of necrosis extending beyond the femoral neck.

CCD and offset after Nanos short stem in total hip arthroplasty.

BACKGROUND: Many short stems for total hip arthroplasty have been introduced by the manufacturers only during the last decade. One of them is the Nanos short stem (Smith and Nephew, Marl, Germany). The development of short stems was aimed at preserving bone and soft tissue by utilizing a minimally invasive approach, thus allowing a quick return to an active life. It was purpose of this study to evaluate the radiological changes after using this device. METHODS: We present the radiological results of 202 cementless THAs which were performed in 172 patients using the Nanos stem. Radiological evaluation was performed using standing anterior-posterior (AP) and lateral radiographs of the proximal femur preoperatively, postoperatively and during the follow up. We analyzed the preoperative and postoperativ CCD angle, the subsisdence, preoperative and postoperative offset, osteolysis, bone resorption, increased density, neocortex and periarthricular ossifications. RESULTS: One stem had to be revised due to subsidence four days after implantation. Two cups (BiconPlus, Smith and Nephew, Marl, Germany) had to be revised during the time of follow up due to an aseptic cup loosening. Two stems showed radiolucent lines at the implant-bone-interface at the last follow-up. An increase of bone density could be detected in 18 hips (8.9%). 14 hips showed periarticular ossifications. Measurable subsidence was detected in a total of four stems (1.9%). The preoperative neck-shaft-angle angle was 133.8 ± 4.4° (range: 118.5-146.2) and the neck-shaft-angle angle at the time of follow up was 134.6 ± 4.3° (range: 123.3-147; P< 0.05). The preoperative and postoperative offset changed from 109.3 ± 11.9 mm (range: 80.9-131.6) to 109.7 ± 12.3 mm (range: 79.7-155.6; P< 0.05). CONCLUSION: In summary, this study shows that a correct anatomical reconstruction is possible with a device of this design. The outcome is comparable to that of other short stems. Further studies should be performed in a prospective and randomized design to evaluate the advantage of such a device with a higher level of evidence.

Stiffness of callus tissue during distraction osteogenesis.

INTRODUCTION: The treatment of limb length discrepancies by distraction osteogenesis represents a significant challenge of predicting the load bearing capacity. Today, in vivo stiffness measurements by applying compressive, bending or torsional stress on the callus tissue are quantitative methods. Therefore, it is relevant to know how regenerating bone tissue regains its various stiffness characteristics. Knowledge of the development of each type of stiffness is important in order to prevent an over- or underestimation of the actual load bearing capacity. HYPOTHESIS: Various types of stiffness are supposed to evolve similar during consolidation. SUBJECTS AND METHODS: In this ex vivo study, an analysis of torsional, compressive and bending stiffness of callus tissue during consolidation was performed on 26 sheep tibiae after distraction osteogenesis. RESULTS: This study indicates differences within the quantity of stiffness during consolidation. DISCUSSION: Thus, in vivo stiffness measurements have to be interpreted carefully in order to prevent false estimation of the load bearing capacity of new bone.

Magnesium hydroxide temporarily enhancing osteoblast activity and decreasing the osteoclast number in peri-implant bone remodelling.

Repeated observations of enhanced bone growth around various degradable magnesium alloys in vivo raise the question: what is the major mutual origin of this biological stimulus? Several possible origins, e.g. the metal surface properties, electrochemical interactions and biological effects of alloying elements, can be excluded by investigating the sole bone response to the purified major corrosion product of all magnesium alloys, magnesium hydroxide (Mg(OH)(2)). Isostatically compressed cylinders of pure Mg(OH)(2) were implanted into rabbit femur condyles for 2-6 weeks. We observed a temporarily increased bone volume (BV/TV) in the vicinity of Mg(OH)(2) at 4 weeks that returned to a level that was equal to the control at 6 weeks. The osteoclast surface (OcS/BS) was significantly reduced during the first four weeks around the Mg(OH)(2) cylinder, while an increase in osteoid surface (OS/BS) was observed at the same time. At 6 weeks, the OcS/BS adjacent to the Mg(OH)(2) cylinder was back within the same range of the control. The mineral apposition rate (MAR) was extensively enhanced until 4 weeks in the Mg(OH)(2) group before matching the control. Thus, the enhanced bone formation and temporarily decreased bone resorption resulted in a higher bone mass around the slowly dissolving Mg(OH)(2) cylinder. These data support the hypothesis that the major corrosion product Mg(OH)(2) from any magnesium alloy is the major origin of the observed enhanced bone growth in vivo. Further studies have to evaluate if the enhanced bone growth is mainly due to the local magnesium ion concentration or the local alkalosis accompanying the Mg(OH)(2) dissolution.

An alternative treatment method to restore limb-length discrepancy in osteoarthritis with high congenital hip dislocation.

AIM: The purpose of this study was to describe the rationale and to analyse the results of uncemented total hip arthroplasty (THA) in patients with osteoarthritis and congenital dislocation of the hip (CDH) prior to iliofemoral distraction. METHOD: Twenty hips were followed-up for 5.8 years (1-12 years). First the THA components were implanted after soft tissue release. In the interval, iliofemoral distraction with an external distraction apparatus was conducted. The second surgery consisted of an open reduction. An iliofemoral distraction of 0.8 mm/day was monitored. The treatment time was 86 days (50-210 days). In 61 days (32-94 days) the hip joints were distracted for 51 mm (41-75 mm). RESULT: The Harris Hip Score increased significantly by 47 points. The SF-36 health score showed a satisfying increase in all patients. CONCLUSION: In experienced hands this method is a relatively safe procedure for limb-length equalization in patients with severe CDH.

[Ex vivo microCT analysis of possible microfractures of the femoral head during implantation of a cementless hip resurfacing femoral component]. / Ex-vivo-microCT-Untersuchungen zu möglichen Mikrofrakturierungen des Hüftkopfs bei der Implantation eines zementfreien Oberflächenersatzes am Hüftgelenk.

AIM: Microfractures of the femoral head during implantation of the femoral components are suspected to be a cause of fractures at the implant/neck junction which represent a common failure mode in hip resurfacing arthroplasty. Callus formation observed in femoral head retrievals suggests the occurrence of microfractures inside the femoral head, which might be inadvertently caused by the surgeon during implantation. The aim of this biomechanical study was to analyse whether or not the implantation of a cementless femoral component hip resurfacing system causes microfractures in the femoral head. METHOD: After the preparation of 20 paired human cadaveric femoral heads, the cementless femoral component ESKA Typ BS (ESKA Implants GmbH & Co., Lübeck) was implanted on 9 specimens with an impaction device that generates 4.5 kN impaction force. On 9 specimens the femoral component was implanted by hand. One head was used as a fracture model, 1 specimen served as control without manipulation. The femoral component used for impaction was equipped with hinges to enable its removal without further interfering with the bone stock. Specimens were scanned with a microCT device before and after impaction and the microCT datasets before and after impaction were compared to identify possible microfractures. RESULTS: Twenty strikes per hand or with the impaction device provided sufficient implant seating. Neither the macroscopic examination nor the 2-dimensional microCT analysis revealed any fractures of the femoral heads after impaction. CONCLUSION: At least macroscopically and in the 2-dimensional microCT analysis, implantation of the cementless hip resurfacing femoral component ESKA Typ BS with 4.5 kN or by hand does not seem to cause fractures of the femoral head.

The uncemented primary Bicontact stem in revision total hip arthroplasty in young patients.

AIM: The purpose of this study was to evaluate the uncemented primary Bicontact stem (B.Braun-Aesculap, Tuttlingen, Germany) as a possible adequate alternative to other revision systems in revision total hip arthroplasty. METHODS: Twenty patients aged up to 58 years (34-58 years, mean age 5.7 +/- 5.8 years) with minor bone defects underwent a revision total hip arthroplasty with the uncemented primary Bicontact stem. The patients were assessed clinically and radiologically at follow-up (follow-up: 8.0 +/- 3. years). RESULTS: The postoperative Harris Hip Score, Motion and Pain Score improved significantly. There was only one further revision in these patients because of infection and only one case with mild stress shielding. CONCLUSION: The uncemented primary Bicontact stem seems to be a good alternative to other revision systems in total hip revision arthroplasty in young patients.

[Intraoperative femoral fractures during the implantation of the cementless BiCONTACT stem: a matched-pair analysis of 84 patients]. / Intraoperative Femurfrakturen bei der Implantation des zementfreien BiCONTACT-Schaftes: eine Matched-Pair-Analyse von 84 Patienten.

AIM: Intraoperative periprosthetic femoral fractures (PFF) during the implantation of primary non-cemented total hip arthroplasties (THA) are an increasing problem. Thus, the goal of this study was to analyse the postoperative performance of primary non-cemented THA in patients with intraoperative PFFs, with respect to the patient's subjective health-related satisfaction. METHOD: 42 PFFs in 1216 primary THAs using the non-cemented BiCONTACT stem were monitored. Patients were compared to a control group of 42 non-cemented THA patients without intraoperative fracture complications, using the matched-pair analysis. Preoperative and after 2.2 years (0.8-3.2 years), patients were followed-up clinically and radiographically. Clinical parameters were Harris hip score, SF-36 health score, function and pain score and postoperative complications. Radiographic parameters were bone union, stem and trochanter migration. Fractures were graded using the Vancouver classification. RESULTS: Results showed a significant increase in both Harris hip score and motion score and a significant decrease in pain score in both groups (p<0.001). The SF-36 health score increased significantly in nearly every dimension in both groups. Except for 2 patients with trochanter migrations of 25 and 20 mm, all fractures showed bony union. In 3 patients the stems subsided by 4.7 +/- 2.9 mm. The stems showed no further migration at final follow-up. 2 patients without intraoperative fractures underwent stem revision. Overall increases and postoperative complication rates were not significantly different between the groups. CONCLUSION: Mid-term THA performance and patient satisfaction are not influenced by intraoperative Vancouver A and B1 fractures during implantation of the non-cemented BiCONTACT stem compared to a collective without intraoperative fractures during implantation.

[Analysis of 10-year survival after flexion osteotomy for femoral head necrosis]. / 10-Jahres-Uberlebensanalyse der Flexionsosteotomie bei Femurkopfnekrose.

AIM: We have investigated the value of flexion osteotomy for femoral head necrosis with regard to the survival rate. METHOD: We examined 40 patients who were treated by flexion osteotomy for femoral head necrosis at the Hannover Medical School in the years 1969 to 1995. The mean follow-up period was 14.1 years. RESULTS: The mean survival time of the flexion osteotomies was 9.6 years. In 23 of the 40 patients, it failed within 10 years after surgery, which implies a 10-year survival rate of 42.5 %. For these 23 patients, the implantation of a total hip arthroplasty (THA) became necessary after an average time of 6.6 years. CONCLUSION: Due to the poorly predictable success of the flexion osteotomy and the comparatively poor patient satisfaction, the indication for flexion osteotomy in such cases should be reconsidered.

Saving Implants BMP-2 Application in Revision Total Hip Surgery.

OBJECTIVE: Besides others, there are two major problems in total hip replacement surgery which result in implant failure. First there is aseptic loosening due to a lack of implant biocompatibility or micromovements and second periimplant wear debris induced osteolysis which limits the survival rate of an implant. Regarding to recent data there are only limited therapeutic strategies to heal these bony defects without arthroplasty revision surgery. Since the investigation and characterization of adult mesenchymal stem cells (MSCs) from bone marrow, a cell and tissue engineering based therapy might be a promising solution to heal endoprosthesis associated bony defects. Moreover the application of growth factors in bone reconstructive surgery is another treatment concept to promote local bone regeneration. PATIENT AND METHODS: We report about a 73-year old patient with a painful weight bearing and a large, wear debris induced pelvic osteolysis after total hip arthroplasty. To prevent from salvage surgical procedures and preserve bone, a healing attempted was performed by filling the critical bony defect zone with a BMP-2/MSC composit. RESULTS: Clinical and radiological follow-ups showed a progressive bony healing of the critical size defect area without any complications. Fifteen months after application the patient is still pain free, has no limitations in daily life or sport activities. CONCLUSION: The case embarks on a strategy of non-embryonic stem cell and growth factor application to heal bony defects at patients with total hip endoprosthesis.

Comparison of various types of stiffness as predictors of the load-bearing capacity of callus tissue.

The ability to predict load-bearing capacity during the consolidation phase in distraction osteogenesis by non-invasive means would represent a significant advance in the management of patients undergoing such treatment. Measurements of stiffness have been suggested as a promising tool for this purpose. Although the multidimensional characteristics of bone loading in compression, bending and torsion are apparent, most previous experiments have analysed only the relationship between maximum load-bearing capacity and a single type of stiffness. We have studied how compressive, bending and torsional stiffness are related to the torsional load-bearing capacity of healing callus using a common set of samples of bone regenerate from 26 sheep treated by tibial distraction osteogenesis. Our findings showed that measurements of torsional, bending and compressive stiffness were all suitable as predictors of the load-bearing capacity of healing callus. Measurements of torsional stiffness performed slightly better than those of compressive and bending stiffness.

[Navigator concept. Optimizing the procedure for navigated total knee arthroplasty]. / Das Navigatorkonzept. Prozessoptimierung in der navigierten Knieendoprothetik.

BACKGROUND: This study addresses work sharing during navigation-assisted total knee arthroplasty. Specifically, the concept is introduced of a "navigator" assistant who operates the navigation system during surgery while the surgeon concentrates on the primary steps of surgery. METHODS: In a prospective study of 40 total knee arthroplasties, one group of patients was treated using the navigator concept, a second group was treated using a conventional navigation setup, and a third group was treated with conventional internal and external alignment jigs. Surgery time and outcome parameters were compared. RESULTS: Results show a significant difference in surgery time between the three groups. The conventional and navigator concept groups showed similar surgery times; however, the navigation group without navigation concept exhibited longer surgery time. CONCLUSIONS: The navigator concept represents a highly effective principle to minimize surgery time needed during navigated total knee arthroplasty.

[Improved osseointegration of titanium implants after surface coating with polymers in a rabbit model]. / Verbesserte Osteointegration von Titanimplantaten nach Oberflächenbeschichtung mit Polymeren im Kaninchenmodell.

In this study we present the first results of the investigation of polymer-coated titanium implants implanted in the proximal tibia and distal femora of New Zealand white rabbits. The results of DEXA scans, micro-CT, and histological analysis showed an increase of osseointegration. We suggest that controlled release kinetics after coupling of these polymers with BMP-2 can additionally increase osseointegration.

[Correction of forearm deformities in children with multiple cartilaginous osteochondromas]. / Deformitätenkorrektur am Unterarm bei Kindern mit multipler kartilaginärer Exostosenkrankheit.

AIM: Deformity of the forearm with shortening and bowing is common in children with multiple cartilaginous osteochondromas. The objective of this study was to evaluate the benefit of ulnar lengthening using an external fixateur in these patients. METHOD: 9 patients (10 cases) underwent surgery of the forearm between 1995 and 2001 and were evaluated using a standard protocol. The mean follow-up was 33.6 months, the mean age at operation 8.9 years. All patients were treated with ulnar lengthening, in 6 cases combined with an excision of the osteochondromas. RESULTS: Four out of ten patients did show an improvement in postoperative forearm rotation, two deteriorated and 4 presented unchanged. Wrist motion improved in 7 patients and remained unchanged in 3. The postoperative radial articular angle showed an improvement in 6, the carpal slip in 9 of the patients. The preoperative radial head dislocation in one patient remained unchanged postoperatively. CONCLUSION: The authors advocate this therapeutic concept for the correction of forearm deformity in multiple hereditary osteochondromas to prevent a progression of the deformity and to establish carpal stability. A significant improvement of forearm and wrist function could not be reached.

[Injectable carrier system for growth factor application in minimally invasive stimulation of bone healing]. / Injizierbare Trägersysteme für die Wachstumsfaktorapplikation zur minimal-invasiven Knochenheilungsstimulation.

The characterization and cloning of growth factors for bone healing provide an enormous potential for minimally invasive treatment procedures for bone defects or fractures. However, the clinical application of injection vehicles for these growth factors must be made user-friendlier. In this study, two different injection vehicles were tested for their practicability and efficacy to enhance callus maturation during distraction osteogenesis. Calcium phosphate carriers showed a rather low user-friendliness and were less efficient in the animal model of distraction osteogenesis in sheep. Collagen carriers provided both a higher practicability for injection procedures and a higher efficacy.

[Kyphoscoliosis in Wiedemann-Rautenstrauch-syndrome (neonatal progeroid syndrome)]. / Kyphoskoliose beim Wiedemann-Rautenstrauch-Syndrom (neonatales Progerie Syndrom).

AIM: The Wiedemann-Rautenstrauch syndrome (neonatal progeroid syndrome, WR syndrome) is a rare autosomal recessive disorder including premature aging already at birth. Most of the patients show an aged face, a craniofacial dysmorphism, decreased subcutaneous fat tissue, a significant developmental delay, and have a short life expectation. We present the second patient described in literature reaching an age of 16 years. Furthermore this patient developed a progressive scoliosis during childhood which to our knowledge has not been reported before among individuals affected by Wiedemann-Rautenstrauch syndrome. The pathogenetic features of the spinal deformity are discussed and the operative management is described. METHOD: The patient underwent a three-stage correction of her spinal deformity (anterior thoracic and lumbar release and posterior release, correction of the deformity with instrumentation and fusion) supported by Halo traction and physiotherapy. RESULTS: At the latest follow-up 12 months postoperatively the patient showed a stable correction from 78 degrees to 38 degrees in the frontal plane with physiologic sagittal alignment both clinically and radiologically. CONCLUSION: The scoliosis of our patient with Wiedemann-Rautenstrauch syndrome showed radiologically and clinically the characteristics of a neuromuscular curve. Since the curve showed a significant progression and high rigidity operative correction and fusion was indicated. We recommend a staged operative management to minimize the high risks of the operations and possible complications from cardiological and respiratory dysfunction associated with WR syndrome.

Bone turnover during distraction osteogenesis in an experimental sheep model.

Biochemical serum markers of osteoblastic activity and collagen turnover were measured in a sheep model of distraction osteogenesis. Significant increases of the bone formation marker osteocalcin were found during the first part of the consolidation phase and peaked at a time point equalling the distraction phase. Collagen turnover parameters pyridinoline and the specific type I collagen marker desoxypyridinoline consistently increased during the distraction and consolidation phases. While pyridinoline peaked at a time point similar to osteocalcin, desoxypyridinoline increased to a later stage in consolidation, indicating continuous turnover of bone-specific type I collagen. The results indicate a characteristic pattern of osteoblast cellular activation during distraction osteogenesis with possible consequences for the timing of treatment.

[Assessment of bone healing during callus distraction by an automatic torsional stiffness metering system]. / Erfassung der Knochenheilung während der Kallusdistraktion durch ein automatisiertes torsionales Steifigkeitsmesssystem.

The present article describes a newly developed device for the quantitative assessment of torsional in vivo stiffness of regenerating bone under callus distraction. Both the design and function of this device, and its use during bony consolidation are discussed. The device exhibited an accuracy of +/- 18% for stiffness under 0.1 Nm/degree, and +/- 5% stiffness above 0.1 Nm/degree. The average accuracy was +/- 14%. The data scatter for the stiffness measurement ranged between +/- 1.43% and +/- 7.68% (average: +/- 3.99%). The precision of a test machine was between +/- 0.01% and +/- 11.3% (average: +/- 3.65%). The method has the following advantages over existing methods for investigating healing: 1. no need to dismantle the external fixation for measurement; 2. preservation of the bone axis with minimal risk of misalignment during the bone healing process; 3. minimal technical requirements, with easy, noninvasive measurement; 4. no exposure to X-radiation.