Martin Rupprecht

The treatment of intertrochanteric fractures: results using an intramedullary nail with integrated cephalocervical screws and linear compression.

Objective: A new device for the treatment of intertrochanteric fractures that uses 2 cephalocervical screws in an integrated mechanism allowing linear intraoperative compression and rotational stability of the head/neck fragment has been developed. The aim of this study was to describe the results using this device for the treatment of stable and unstable intertrochanteric fractures. Design: Prospective, consecutive. Setting: Academic Trauma Center. Methods: Between March 1, 2005, and July 31, 2006, 100 consecutive patients with an intertrochanteric fracture were treated with a new trochanteric antegrade nail (InterTan; Smith-Nephew, Memphis, TN). All living patients were followed up for a minimum of 1 year postoperatively (range 12-27 months). Clinical and radiographic examinations were performed until healing and at the 1-year anniversary of the index procedure. Healing, pain with ambulation, return to activities of daily living, the modified Harris hip score, and Barthel Index were used to evaluate outcomes. Results: The mean age of the patients was 81.2 (±11.3) years. Thirty-seven patients died, 12 were too infirmed for follow-up, and 3 could not be located, leaving 48 patients available for final evaluation. The average surgical time was 41 minutes (13-95 minutes). This rose significantly with the complexity of the fracture (OTA/AO classification: A1 versus A3, P = 0.016). All fractures healed within 16 weeks (range 10-16 weeks). Radiographic analysis at healing revealed no loss of reduction, no uncontrolled collapse of the neck, no nonunions, no femoral shaft fractures, and no implant failures. Two cases in the series were poorly reduced and settled into varus malalignment. There was no varus malposition seen in the remaining 46 fractures. The mean prefracture Harris hip score (75.1 ± 13.4) was significantly reduced at the time of follow-up (70.3 ± 14.5, P = 0.003); 58% of the patients recovered their prefracture status. No significant difference was seen for the Barthel Index. Conclusions: The InterTan device appears to be a reliable implant for the treatment of intertrochanteric femoral fractures. Its design provides for stability against rotation and minimizes neck malunions (shortening) through linear intraoperative compression of the head/neck segment to the shaft. As a result of the negligible complication rate and improved clinical outcomes, this implant is now the standard treatment for all intertrochanteric fractures at our institution.

Age- and sex-related changes of humeral head microarchitecture: Histomorphometric analysis of 60 human specimens†

Fractures of the humeral head are frequent and will further increase due to demographic changes. Prior to operative fracture treatment, the regional differences of bone quality, especially of elderly people, have to be carefully considered to assure stable implant fixation. However, conclusive data concerning the variation of histomorphometric parameters are still lacking. Consequently, the purpose of this study was to analyze the age‐ and sex‐related changes in bone microarchitecture. For that reason, 60 proximal humeri were harvested from patients at autopsy. Twelve regions of interest (ROI) were defined for each centered coronar humeral head slice and the specimens were subjected to radiographic, histological, and histomorphometric analyses. We could demonstrate that in contrast to men, women over 60 years of age had a significant age‐related decrease in bone mass. The most prominent decrease was observed in the region of the greater tuberosity, which represents an osteoporotic fracture site. The most superior and medially located part of the centered coronar humeral head slice showed, independent from age and sex, the highest bone mass and can therefore be considered as the best location for subchondral screw placement. Taken together, our study revealed distinct sex‐related changes of the humeral head bone microarchitecture with aging, which should be considered in implant positioning.

Biomechanical evaluation of peri- and interprosthetic fractures of the femur.

BACKGROUND Because of an increasing life expectancy of patients and the rising number of joint replacements, peri- and interprosthetic femoral fractures are a common occurrence in most trauma centers. This study was designed to answer two primary questions. First, whether the fracture risk increases with two intramedullary implants in one femur; and second, whether a compression plate osteosynthesis is sufficient for stabilizing an interprosthetic fracture. METHODS Twenty-four human cadaveric femurs were harvested and four groups were matched based on the basis of bone density using a peripher quantitative computer tomography (pQCT). All groups-(I) hip prosthesis with a cemented femoral stem; (II) hip prosthesis and retrograde femoral nail; (III) hip prosthesis, retrograde femoral nail, and lateral compression plate; (IV) all three implants with an additional simulated interprosthetic fracture-were biomechanically tested in a four-point bending in lateral-medial direction. RESULTS The second group with two intramedullary implants exhibited 20% lower fracture strength in comparison with group 1 with proximal femoral stem only. The stabilization of an interprosthetic fracture with a lateral compression plate (group IV) resulted in a fracture strength similar to femur with prosthesis only. CONCLUSION Two intramedullary implants reduce the fracture strength significantly. If an interprosthetic fracture occurs, sufficient stability can be achieved by a lateral compression plate. Because two intramedullary implants in the femur may decrease the fracture strength, the treatment of supracondylar femoral fractures with a retrograde nail in cases with preexisting ipsilateral hip prosthesis should be reconsidered.

What is the risk of stress risers for interprosthetic fractures of the femur? A biomechanical analysis

PurposeDue to increasing life expectancy we see a rising number of joint replacements. Along with the proximal prosthesis in the femur, more and more people have a second implant on the distal ipsilateral side. This might be a retrograde nail or a locking plate to treat distal femur fractures or a constrained knee prosthesis in the case of severe arthrosis. All these constructs can lead to fractures between the implants. The goal of this study was to evaluate the risk of stress risers for interprosthetic fractures of the femur.MethodsThirty human cadaveric femurs were divided into five groups: (1) femurs with a prosthesis on the proximal side only, (2) hip prosthesis on the proximal end and a distal femur nail, (3) femurs with both a hip prosthesis and a constrained knee prosthesis, (4) femurs with a hip prosthesis on the proximal side and a 4.5-mm distal femur locking plate; the locking plate was 230 mm in length, with ten holes in the shaft, and (5) femurs with a proximal hip prosthesis and a 4.5-mm distal femur locking plate; the locking plate was 342 mm in length, with 16 holes in the shaft.ResultsFemurs with a hip prosthesis and knee prosthesis showed significantly higher required fracture force compared to femurs with a hip prosthesis and a distal retrograde nail. Femurs with a distal locking plate of either length showed a higher required fracture force than those with the retrograde nail.ConclusionsThe highest risk for a fracture in the femur with an existing hip prosthesis comes with a retrograde nail. A distal locking plate for the treatment of supracondylar fractures leads to a higher required fracture force. The implantation of a constrained knee prosthesis that is not loosened on the ipsilateral side does not increase the risk for a fracture.

Cement augmentation of the proximal femoral nail antirotation for the treatment of osteoporotic pertrochanteric fractures—A biomechanical cadaver study

INTRODUCTION Proximal femoral fractures will gain increasing importance in the future due to the epidemiological development. Osteoporosis is often a limiting factor in the achievement of implant stability. New nailing systems offer the possibility of augmentation of the femoral neck component with cement. The aim of this study was to perform a biomechanical comparison of implant stability in osteoporotic pertrochanteric fractures using the proximal femoral nail antirotation (PFNA, Synthes GmbH, Umkirch, Germany) with cement augmented and non-augmented blades. MATERIALS AND METHODS Bone mineral density (BMD) was measured by dual-energy X-ray absorptiometry (DEXA) in six pairs of fresh-frozen human femurs. Standardised pertrochanteric fractures (AO31-A2.3) were treated with a PFNA. Cement augmentation was performed in six constructs. Axial loading was applied according to a single-leg-stance model using a hydraulic testing machine increasing to 1400N over 10,000 cycles. Biomechanical comparisons between the two groups that were comparable concerning BMD, tip-apex-distance and native stiffness were made with regard to postoperative stiffness, survived cycles, load to failure, failure mechanism and axial displacement. RESULTS The stiffness of all stabilised femurs was significantly lower than for native specimens (native 702.5±159.6N/mm vs. postoperative 275.4±53.8N/mm, p<0.001). Stiffness after instrumentation was significantly greater for the cement augmented group than for the non-augmented group (300.6±46.7N/mm vs. 250.3±51.6N/mm, respectively, p=0.001). Five of the twelve constructs survived cyclic testing. Statistically significant differences of the BMD were detected between survived and failed constructs (0.79±0.17g/cm(2) vs. 0.45±0.12g/cm(2), respectively, p=0.028). The failure loads for specimens surviving 10,000 cycles were 4611.9±2078.9N in the cement augmented group (n=3) and 4516.3N and 3253.5N in the non-augmented group (n=2). Postoperative stiffness was found to be a positive predictor of maximum force to failure (R(2)=0.83, p=0.02). CONCLUSIONS The results of this biomechanical study show that cement augmentation of the PFNA increases the implant stability in osteoporotic pertrochanteric fractures. Further studies are necessary to evaluate this procedure in providing long term clinical results.

Biomechanical Evaluation for Mechanisms of Periprosthetic Femoral Fractures

BACKGROUND There are a number of biomechanical tests for various treatment options of periprosthetic femoral fractures, but different loading modalities prelude their direct comparison. This study was designed to develop an experimental model of osteoporotic bone fractures near the femoral stem that is based on a simple testing protocol to increase the reproducibility. In addition, we wanted to clarify whether a femoral prosthetic stem reduces the femoral fracture strength. METHODS Twenty human cadaveric femurs were harvested, and five groups were randomized on the basis of the bone mineral density using a pQCT device. The specimens of three groups were provided with a cemented Exeter V40 stem and loaded to failure with torsion (I), anterior (II), and lateral load (III). The femurs of groups IV and V remained uninstrumented and were tested in a four-point bending assay similar to groups II and III. All biomechanical testings were realized with a servohydraulic testing machine (MTS). RESULTS There was no significant difference regarding bone mineral density of all groups. Torsional testing generated proximal intertrochanteric fractures and anterior loading resulted exclusively in supracondylar fractures. Introducing the force from the lateral side, all fracture lines occurred close to the tip of the stem, similar to a Vancouver-B fracture. Assuming that lateral load application is a main responsible mechanism of periprosthetic femoral fracture near the tip of the stem, the fracture strength of instrumented femurs was significantly reduced (group III: 4,692 N vs. group V: 6,931 N; p < 0.05). CONCLUSION Prosthetic stems reduce femoral fracture strength significantly. In an osteoporotic bone model, a four-point bending test with lateral load application seems to be a suitable approach.

Internal fixation of femoral neck fractures with posterior comminution: A biomechanical comparison of DHS® and Intertan nail®

Background and purposeInternal fixation is a therapeutic mainstay for treatment of undisplaced femoral neck fractures and fractures without posterior comminution. The best treatment for unstable and comminuted fractures, however, remains controversial, especially in older patients. The present study was designed to assess the utility of the Intertan Nail® (IT) for stabilization of comminuted Pauwels type III fractures compared to dynamic hips screw (DHS).MethodsRandomized on the basis of bone mineral density, 32 human femurs were assigned to four groups. Pauwels type III fractures were osteomized with a custom-made saw guide. In 16 specimens the posteromedial support was removed and all femurs were instrumented with an IT or a DHS. All constructs were tested with nondestructive axial loading to 700N, cyclical compression to 1,400N (10,000 cycles), and loading to failure. Outcome measures included number of survived cycles, mechanical stiffness, head displacement and load to failure.ResultsPostoperative mechanical stiffness and stiffness after cyclical loading were significantly reduced in all constructs regardless of the presence of a comminution defect (p = 0.02). Specimens stabilized with the IT had a lower construct displacement (IT, 8.5 ± 0.5 mm vs. DHS, 14.5 ± 2.2 mm; p = 0.007) and sustained higher failure loads (IT, 4929 ± 419 N vs. DHS, 3505 ± 453 N; p = 0.036) than the DHS constructs.InterpretationIn comminuted Pauwels type III fractures, the fixation with the IT provided sufficient postoperative mechanical strength, comparable rate of femoral head displacement, and a similar tolerance of physiological loads compared to fractures without comminution. The absence of the posteromedial support in comminuted fractures tended to reduce the failure load regardless of the fixation method.

[Periprosthetic fractures. Long-term results after plate osteosynthesis stabilization].

BACKGROUND Due to the increasing age of patients and the rising number of joint replacements, the incidence of periprosthetic fractures (PPF) is also increasing. The treatment should be selected with knowledge of the prefracture interface status and the type of fracture involved. The aim of this study was to evaluate our treatment of PPF with long-term follow-up. PATIENTS AND METHODS From 1988 to 2006, 99 patients with PPF were treated in our department. In 86 cases a plate osteosynthesis was used. After a mean time of 7.3+/-2.8 years, we studied 56 patients and monitored their complications. RESULTS The most diagnosed fracture was Johansson type III (44%). Seventy-one patients were treated with a conventional and 15 with locking-plate osteosynthesis. In 15 cases (17.5%) we found severe complications (3 breaks and 3 dislocations of the plates, 6 cases of pseudarthrosis, 2 deep wound infections, and 1 case of postoperative bleeding). CONCLUSION Due to the minor frequency of severe complications, plate osteosynthesis of a periprosthetic fracture with a loosened interface is a good therapeutic option for individual patients, particularly for geriatric patients and those without disorders specific to a loosened interface.

Combined treatment of congenital pseudarthrosis of the tibia, including recombinant human bone morphogenetic protein-2: A CASE SERIES

The use of recombinant human bone morphogenetic protein-2 (rhBMP-2) for the treatment of congenital pseudarthrosis of the tibia has been investigated in only one previous study, with promising results. The aim of this study was to determine whether rhBMP-2 might improve the outcome of this disorder. We reviewed the medical records of five patients with a mean age of 7.4 years (2.3 to 21) with congenital pseudarthrosis of the tibia who had been treated with rhBMP-2 and intramedullary rodding. Ilizarov external fixation was also used in four of these patients. Radiological union of the pseudarthrosis was evident in all of them at a mean of 3.5 months (3.2 to 4) post-operatively. The Ilizarov device was removed after a mean of 4.2 months (3.0 to 5.3). These results indicate that treatment of congenital pseudarthrosis of the tibia using rhBMP-2 in combination with intramedullary stabilisation and Ilizarov external fixation may improve the initial rate of union and reduce the time to union. Further studies with more patients and longer follow-up are necessary to determine whether this surgial procedure may significantly enhance the outcome of congenital pseudarthrosis of the tibia, considering the refracture rate (two of five patients) in this small case series.

Temporary screw epiphyseodesis of the distal tibia: a therapeutic option for ankle valgus in patients with hereditary multiple exostosis.

Background Ankle valgus in multiple hereditary exostoses (HME) is frequently seen and may result in activity related pain, deformity, or even early degenerative arthritis. Standard treatment protocols do not exist. The effect of medial screw hemiepiphysedesis of the distal tibia to correct ankle valgus is evaluated in this patient population. Methods A retrospective review of 9 patients with HME and ankle valgus deformity (15 affected extremities) who were treated by a screw hemiepiphyseodesis of the medial physis of the distal tibia is presented. Mean age at time of operation was 11.8±1.6 years (range: 9.6 to 14.7 y). All patients underwent clinical and radiological evaluation. To define the magnitude of ankle valgus we evaluated tibial tilt angle and Malhotra stations preoperatively, at time of screw removal and/or at time of the most recent clinical follow-up. Results In 11 extremities the screws were removed after an average time of 22.6±8.0 months (range: 12 to 35 mo) and all patients were examined after a mean time of 36.7±18.7 months after hemiepiphyseodesis (range: 13 to 69 mo). The mean preoperative tibiotalar tilt was 14.3±4.4 degrees (range: 9 to 22 degrees). At time of screw removal the tibiotalar tilt was normalized to 0.4±1.7 degrees (range: −2 to 4 degrees), according to a mean rate of correction of 0.58±0.23 degrees by the month (range: 0.23±0.92 degrees). With follow up 4 ankles demonstrated a change in the fibular station. None of the patients overcorrected into a severe varus, one patient developed a recurrent ankle valgus. Conclusions The temporary screw hemiepiphyseodesis of the distal tibial physis is an effective, technically simple, and minimally invasive technique to correct ankle valgus deformity in children with HME. Level of Evidence IV.