Rotational Stability of Scaphoid Osteosyntheses: An In Vitro Comparison of Small Fragment Cannulated Screws to Novel Bone Screw Sets.

BACKGROUND: The current standard of care for operative repair of scaphoid fractures involves reduction and internal fixation with a single headless compression screw. However, a compression screw in isolation does not necessarily control rotational stability at a fracture or nonunion site. The single screw provides rotational control through friction and bone interdigitation from compression at the fracture site. We hypothesize that osteosyntheses with novel bone screw sets (BSS) equipped with anti-rotational elements provide improved rotational stability. METHODS: Stability of osteosynthesis under increasing cyclic torsional loading was investigated on osteotomized cadaveric scaphoids. Two novel prototype BSS, oblique type (BSS-obl.) and longitudinal type (BSS-long.) were compared to three conventional screws: Acutrak2®mini, HCS®3.0 and Twinfix®. Biomechanical tests were performed on scaphoids from single donors in paired comparison and analyzed by balanced incomplete random block design. Loading was increased by 50 mNm increments with 1,000 cycles per torque level and repeated until a rotational clearance of 10°. Primary outcome measure was the number of cycles to 10° clearance, secondary outcome measure was the maximum rotational clearance for each torque level. FINDINGS: BSS-obl. performed significantly better than Acutrak2®mini and HCS® (p = 0.015, p<0.0001). BSS-long. performed significantly better than HCS® (p = 0.010). No significant difference in performance between BSS-obl. and BSS-long. (p = 0.361), between BSS obl. and Twinfix® (p = 0.50) and BSS long. and Twinfix® (p = 0.667) was detected. Within the torque range up to 200 mNm, four of 21 (19%) BSS-long. and four of 21 (19%) BSS-obl. preparations showed early failure. The same loading led to early failure in four (29%) Twinfix®, seven (50%) Acutrak2®mini and 10 (71%) HCS® of 14 screw samples, respectively. CONCLUSIONS: For both BSS and to a lesser extent for Twinfix® (as dual-component screw), higher rotational stabilities were identified in comparison to single component headless compression screws.

In vitro experimental investigation of the forces and torque acting on the scaphoid during light grasp.

The aim of this study was to measure the magnitude and direction of forces and torque within osteotomized scaphoids within cadaveric wrists during grasping movement of the hand. The mechanical contributions of clinically relevant individual wrist-crossing tendon groups were investigated. Wrists of eight forearms were immobilized in the sagittal, transverse, and coronal plane on a fixation device with unhindered axial gliding. The scaphoid was osteotomized and the fragments stabilized using an interlocking nail. The nail served as a sensor for measurement of inter-fragmentary forces orthogonal and torque around the sensor axis. Thus, torque and cantilever forces were measured which originated between the fragments through co-contraction through the activity of wrist-crossing tendons. Grasping movement of the hand induced a mean maximum torque of 0.038 ± 0.051 Nm and a force of 4.01 ± 1.71 N on the scaphoid. The isolated activation of thumb tendons resulted in a torque of 9.9 E-3 ± 7.7 E-3 Nm and a force of 1.42 ± 0.49 N. Despite immobilization of the wrist, grasping movement of the hand caused substantial forces and torque within the osteotomized scaphoid bone in varying directions and severity among different specimens. These factors may contribute to the development of nonunions and malunions in unstable scaphoid fractures through interfragmentary micromotion. © 2016 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 34:1734-1742, 2016.

Periprosthetic femoral fractures--incidence, classification problems and the proposal of a modified classification scheme.

INTRODUCTION: The increasing incidence of periprosthetic fractures correlates directly with the year-after-year increasing frequency of primary joint replacement surgery. The most common fracture localisation is the femur. The undisputed leader in frequency is the fracture that occurs around a total hip arthroplasty. Unfortunately, no general epidemiologic data exist dealing with exact fracture incidence numbers. Furthermore, existing classifications are lacking important information like time point of fracture occurrence, type of the implanted prosthesis and implantation technique (cemented vs. cementless). Additionally, information about mechanical quality of the bone structure and the fracture type are also missing in part. METHODS: We scanned the literature for adequate and widely used classifications in the field of hip and knee arthroplasty. In a next step we analyzed those classification systems in order to find out to what extent they are able to describe the specific aspects of the fracture event. Therefore we compared the existing classifications and presented their most relevant emphasis. Furthermore, we looked at our own patient population to evaluate incidence of fracture occurrence over time and percentage of loosened components. RESULTS: The existing classification systems address themselves specifically to the task of describing fracture localization and to some extent fracture type, or combine these two in order to calculate the possibility of loosening of the implanted prosthesis. Some of the important criteria like mechanical quality of the bone stock, primary implantation technique or time point of the prosthesis loosening (prior to or because of the fracture) remain ignored. The incidence of periprosthetic femur fractures at our department increased approximately 2.5 fold over the past two decades. The risk of suffering from a periprosthetic fracture was substantially higher after THA than after TKA. We observed a loose femoral component of the THA in about 45 % of the cases. Finally, we postulate the application of a modified classification for periprosthetic fractures as an alternative to the already published ones; not only for the femur, but also universally for all joints with an arthroplasty. CONCLUSION: The classification that is introduced in this study allows, in our opinion, a differentiated reflection of the given post-traumatic pathologic changes and enables the description of the fracture itself according to a generally accepted fracture classification scheme.

Do meta-analyses reveal time-dependent differences between the clinical outcomes achieved by microfracture and autologous chondrocyte implantation in the treatment of cartilage defects of the knee?

PURPOSE: To test the hypothesis that autologous chondrocyte implantation (ACI) has a better treatment effect than microfracture (MF), and increasing superiority over the years, when performed under similar patient-specific and defect-specific conditions. METHODS: We scanned four electronic databases for controlled clinical trials or controlled prospective observational studies. We conducted random-effects meta-analyses of equivalent data using standardized mean differences as the outcome measure of choice at 1, 2, and 5-year follow-up. We assessed heterogeneity with the I (2) index and publication bias with funnel plots and Kendall's tests. RESULTS: Our literature search revealed six study populations (nine papers) which satisfied our eligibility criteria. Overall, 399 patients aged between 16 and 60 years with 1-10 cm(2) chondral defects were available. The MF and the ACI study groups were well matched regarding patient baseline characteristics. For all papers, microfracture was performed according to Steadman, whereas three generations of ACI were applied. When all were combined, non-significant superiority of ACI over MF was revealed; surprisingly, this superiority decreased over the years. However, our meta-analyses combining solely second and third-generation ACI revealed significant standardized differences, becoming smaller over the years, but always representing a large effect. Nevertheless, our approximate estimate of the difference between the treatment effects provoked by second and third-generation ACI and by MF is not indicative of clinically relevant superiority of ACI over MF at 5-year follow-up. CONCLUSIONS: Both series of meta-analyses (combining either all ACI modifications or solely the second and third generations of ACI) suggest that the treatment effects resulting from ACI and MF converge over the years.

Is a magnetic-manual targeting device an appealing alternative for distal locking of tibial intramedullary nails?

BACKGROUND: In order to enable a radiation-free, accurate and simple positioning of distal locking screws, a combined magnetic and manual targeting system has been developed by Sanatmetal®. Where a low-frequency magnetic field is initially used to detect the position of the first drill hole and three more holes can be found with a mechanical template. OBJECTIVES: Our cadaver study was performed to evaluate the accuracy and efficiency of this device. MATERIALS AND METHODS: In two runs, 30 probands (group 1: 10 students; group 2: 10 residents; group 3: 10 attendings), none of who being familiar with the device, tested the radiation-free system using 60 intact cadaver tibias. Each proband performed the surgical procedure twice in succession. RESULTS: Referring to the first attempts, 9.6, 7.2 and 7.1 minutes were the time periods required to insert the four distal screws and the relevant values for the second attempts were 8.6, 6.3 and 6.2 minutes; in both cases revealing a significant difference between group 1 and 2 and group 1 and 3. Furthermore, the mean values within each group indicated a significant decrease of the test duration. Out of the 240 drillings, only one failure (group 1) occurred, representing an accuracy of 99.58 %. Of the probands, 90 % rated the targeting device better than the free-hand technique and 77 % at least attested a high user-friendliness. CONCLUSIONS: Due to our satisfactory test results, the brief training, the steep learning curve and the radiation-free technique the new device has to be considered an appealing alternative for distal locking.

CK/CK-MB ratio as an indirect predictor for survival in polytraumatized patients.

BACKGROUND: Accurate assessment of injury severity is critical for decision making related to the prevention, triage, and treatment of several injured patients. Early estimation of mortality risk of critically injured patients is mandatory for adequate therapeutic strategies. Current risk stratification relies on clinical diagnosis and scoring systems. In our study, we hypothesized whether a simple laboratory test, the CK/CK-MB ratio, could help improving risk prediction in severely traumatized patients. METHODS: In a 9-year period, 328 nonselected trauma patients were included in our retrospective study at a Level I Trauma Center up to September 2002. Data for this study were obtained from our computerized trauma database, established in September 1992. RESULTS: In our study population, we could show a negative correlation between Injury Severity Score (ISS) and leukocytes. A positive correlation was detected for liver enzymes and CK-MB. The correlation between ISS and Na(+) was significant. No correlation between ISS, K(+), and Hb/Ht could be observed. Exitus was associated with ISS, alteration in thrombocytes, CK, CK-MB, CRP, Crea, and Na(+). CONCLUSION: In our study population, CK-MB levels showed a significant correlation with overall surveillance in polytraumatized patients. In our opinion, this might suggest that CK-MB levels could be taken as an indirect predictor for survival. Our findings need to be proven in further prospective clinical trials.

Obesity-related juvenile form of cartilage lesions: a new affliction in the knees of morbidly obese children and adolescents.

OBJECTIVES: Overweight and obesity are afflictions that lead to an increased risk of health problems including joint problems. The aim of the study was to assess the condition of articular cartilage in obese adolescent patients suffering from knee pain. METHODS: MRI of 24 knees of 20 morbidly obese patients, mean age 14.2 years, was performed in an open 1.0 Tesla MR system, where the cartilage, the quality and structure of the menisci, and the presence or absence of surrounding changes was examined. RESULTS: In all patients a cartilage lesion in at least one region of the knee could be detected. Retropatellar cartilage lesions have been found in 19 knees. Ten cartilage lesions grade I, and four lesions grade II have been described in the lateral compartment of the knee, whereas the medial compartment showed in eight cases a grade I, in 13 cases a grade II and in two cases a grade III cartilage lesion. Meniscal changes were assessed in most patients. CONCLUSION: Morbidly obese children and adolescents show major abnormalities in the articular cartilage of the knee. Whether obesity alone is the causal factor for the development of the pattern of these changes, remains to be seen. KEY POINTS: • Morbidly obese children and adolescents often suffer from knee pain • Prospective study showed cartilage and meniscal lesions in morbidly obese adolescents • MRI is an adequate tool for assessing cartilage lesions even in morbidly obese patients • It is unclear whether cartilage abnormalities are mainly due to mechanical overload.

Growth potential of different zones of the growth plate-an experimental study in rabbits.

Despite clinical efforts to treat growth disturbances only little is known about the growth potential of the different zones of the growth plate. The aim of this study was to investigate the growth potential of different zones of the growth plate. A total of 20 New Zealand White rabbits were used for this experiment. The right and left ulna of each animal were used resulting in a total of 40 ulnae. Animals were assigned into five groups. In groups I and II resection of the metaphyseal (n = 12) or the epiphyseal (n = 6) segment of the growth plate was performed. In group III resection of the growth plate and re-implantation was performed (n = 6). In group IV the growth plate was resected and re-implanted after a 180° rotation (n = 6). Animals in group V served as controls. Histologic and radiologic examinations were performed to evaluate the growth process at 1, 2, 4, and 12 weeks following surgery. In group I, III, and IV temporary growth disturbance which was compensated within a short time was observed. Resection of the epiphyseal part resulted in growth arrest of the distal ulna in combination with normal growth of the radius which led to and valgus deformity of the limb. The results of this study indicate the importance of the reserve zone for the functioning of the growth plate.

Epidemiological and economic aspects of polytrauma management in Austria.

INTRODUCTION: In Austria, treatment of multiple trauma patients has developed into an established nationwide trauma center specialty with its own unique identity. Although it represents a substantial financial investment, it ensures supply at international standards. The question of whether multiple trauma patients should be treated only in specialized trauma centers or in several hospitals remains controversial on both national and international grounds. The aim of this study was to assess Austrian trauma departments for international comparison. MATERIAL AND METHODS: We performed a survey of all 54 Austrian trauma departments by collecting data through questionnaires. The number of staff, potential of infrastructure, and treatment strategies were obtained. RESULTS: 93.3% of the trauma departments responded to the questionnaires. In level I trauma centers the amount of trauma beds reached 11% of the total bed capacity, 13% in level II, and 18% in level III units. Level I centers showed an average of 35% of intensive care beds for trauma patients. 53% and 51% were the proportions for level II and III centers. Level I hospitals displayed an average of 28.3 trauma surgeons, while level II and III units had less doctors at their disposal in the trauma departments. On average, 94% of the patients arrived by emergency medical support at the hospital. 94% of the trauma departments used chest tubes, 70% performed craniotomies and neurovascular reconstruction. 33% of the centers were equipped to perform replantations. DISCUSSION: The data demonstrate the broad spectrum of polytrauma treatment in Austrian trauma centers. The discussed need for centralization of polytrauma care cannot be justified based on these data. Limiting from a medical perspective, however, is the lacking comparability of quality of care due to the currently missing objective quality criteria.

Clinical outcome after microfracture of the knee: a meta-analysis of before/after-data of controlled studies.

PURPOSE: The aims of this study were to systematically review the medical literature, in order to find controlled studies about microfracture in the treatment of patients with full-thickness cartilage lesions of the knee, to statistically combine these studies in order to determine a best estimate of the average treatment effect, and to gather information to detect cartilage-specific and patient-specific factors that might have an influence on the clinical outcome. METHODS: We searched four electronic databases for controlled clinical trials or controlled prospective observational studies. We pooled before/after-data of study arms using the term microfracture. RESULTS: We calculated an overall best estimate of 1.106, with [0.566; 1.646] as 95% confidence interval of the mean standardized treatment effect for a representative patient population. CONCLUSIONS: Our meta-analysis revealed a clinically relevant improvement of the postoperative clinical status as compared to the preoperative status. An increase of 22 overall KOOS points may provide a rough estimate for the mean expected treatment effect achieved by microfracturing.

Intramedullary nailing in fracture treatment: history, science and Küntscher's revolutionary influence in Vienna, Austria.

Although the first intermedullary fixation technique was already reported in 1886, successfully inter-medullary nailing did not start until November 1939 when Küntscher's revolutionary technique was applied for the first time. Whereas Küntscher initially stated that his "marrow nail" was suitable for almost every fracture type as well as for other procedures including fixation of osteotomies, joint arthrodesis and pseudarthro-sis treatment he tried to develop an own nail for every possible fracture type through the years. Undoubtedly, Küntscher has to be considered one of the most influential surgeons. Nevertheless, he was never offered a university position and a lot of people did not acknowledge his brilliancy until his death in 1972. Only in Vienna the willingness to seize Küntscher's ideas was high. Therefore, in addition to a historic overview and to fundamental knowledge referring to reamed and unreamed respectively to static and dynamic nailing Küntscher's influence on Viennese researchers is presented in our paper.

The effect of drilling and screw fixation of the growth plate--an experimental study in rabbits.

Injury of the growth plate is a specific problem in traumatology and can cause limb deformity and length discrepancy as a result of growth arrest. The purpose of this study was to evaluate alterations of the growth plate after artificially created injuries. A total of 14 New Zealand White rabbits were used for this experiment. The right and left ulna of each animal was used resulting in a total of 28 ulnae. In six animals drill holes were driven into the growth plate either from the distal/epiphyseal side or from the proximal/metaphyseal side of the physis. In six animals a fracture of the distal ulna corresponding to a Salter-Harris fracture type IV was created. This fracture was fixed by screws from either the epiphyseal or the metaphyseal side. Two animals served as controls. Histologic and radiologic examinations were performed to evaluate the growth process at 1, 2, 4, and 12 weeks following surgery. Drilling or fixation of the growth plate from the metaphyseal side resulted in temporary growth disturbance which was compensated within a short time. In contrast fixation from the epiphyseal side caused severe growth disturbances. Based on our findings K-wires or screws should be inserted from the metaphyseal side and be placed in the center of the growth plate.

Physeal injuries of the proximal humerus: long-term results in seventy two patients.

PURPOSE: The aim of this study was to evaluate our treatment methods of proximal humeral physeal injuries retrospectively and elucidate the relationship between the trauma mechanism, the radiographic injury pattern, the consequent therapy and the functional outcome, and to further deduct and verify prognostic criteria. METHODS: At our Department of Trauma Surgery, 303 children and adolescent patients with fractures of the proximal humeral epiphysis were treated from 1992 to 2009. 72 cases were diagnosed as physeal fractures according to the Salter-Harris classification and were included in our study. RESULTS: 15 physeal fractures of the proximal humerus were reconstructed anatomically by open or closed reduction and produced 93.3% excellent results. 57 physeal fractures were treated in a conservative way and produced 94.7% excellent results. CONCLUSION: We state that epiphyseal injuries should to be treated depending on the age of the patient. This is the only way to decrease the rate of posttraumatic epiphysiodesis with consequent problems, including limb-length discrepancy and/or angular deformities.

Biomechanical comparison of odontoid plate fixation versus odontoid screw fixation.

STUDY DESIGN: Randomized controlled trial with statistically significant difference or statistically no significant difference (Level I). OBJECTIVE: The purpose of this study was to measure the mechanical stability of odontoid plate fixation, using a specially designed plate construct and to compare the results with those after odontoid single-screw and double-screw fixation. SUMMARY OF BACKGROUND DATA: Plate fixation of the odontoid process without C1-C2 is a possible option for the management of odontoid fractures that are not suitable for conventional screw fixation. Although earlier biomechanical works have evaluated the effectiveness of different odontoid screw fixation techniques, no study has quantified the mechanical stability of odontoid fixation by a plate device. METHODS: The second cervical vertebra was removed from 15 fresh human spinal columns. The specimens were fixed to the experimental apparatus with the load cell at the articular surface of the odontoid process. In the first test series, stiffness and failure load of the intact odontoid were measured. Type II odontoid fractures were created by a 45 degree oblique extension loading at the articular surface of the odontoid process. Afterward, the specimens were randomly assigned to 1 of the following 3 groups: in group I (n=5), the fractures were stabilized, using a specially designed plate construct, in group II, the fractures were fixed, using two 3.5 mm cortical screws, and in group III, we used 1 regular 4.5 mm cortical screw. In the second test series, stiffness and failure load of the stabilized odontoid fractures were assessed for comparison and statistical analysis. RESULTS: Group I (plate device) showed a significantly higher mean failure load than group II and group III. The mean failure load of group I, after fixation of the odontoid fracture, was 84% of the mean failure load that was necessary to create a type II odontoid fracture initially. Comparing group II (double screw technique) and group III (single screw technique), there was no significant difference regarding the mean failure load. In both groups, the mean failure load after odontoid fixation was approximately 50% of the mean failure load of the intact odontoid. Statistical analysis also revealed a significantly higher stiffness of the stabilized odontoid after plate fixation than after single- or double-screw fixation. CONCLUSIONS: Plate fixation of the odontoid process for certain type II odontoid fracture patterns provided a significantly higher biomechanical stability than the technique of odontoid screw fixation. Using a specially designed plate construct fixed with 2 cancellous screws into the body of C2 and an additional cortical screw inserted in the odontoid process, 84% of the original stability of the intact odontoid was restored. Single- or double-screw fixation of the odontoid only restored approximately 50% of the original strength.

Where is the distal fracture line location of dorsally displaced distal radius fractures?

No consensus currently exists on the facture location of dorsally displaced distal radius fractures (DRFs). We present a systematic evaluation of the distal fracture line (DFL) location of DRFs and possible influencing factors. Determining the average location of DRFs provides a basis for developing more sensitive tests to determine bone strength using a variety of imaging techniques and for developing improved biomechanical models to test fracture characteristics and surgical implants. Initial radiographs of 157 DRFs dorsally displaced DRFs in patients aged 40-74 years were identified, patient and trauma specific data were collected, and standard radiographic measurements and (AO) fracture classification were performed. The dorsal and palmar DFL locations relative to the corresponding apex of the lunate facet were measured. The DFL was located dorsally 7.9 ± 2.7 mm and palmarly 11.7 ± 3.9 mm proximal to the corresponding lunate fossa apex. The dorsal DFL was significantly distal to the palmar one (p < 0.001), but the two did not correlate (r² = 0.018, p = 0.095). DFL location was independent of age, energy of the fall, and fracture complexity.

Acute compartment syndrome in children: a case series in 24 patients and review of the literature.

Trauma-associated acute compartment syndrome (ACS) of the extremities is a well-known complication in adults. There are only a handful of articles that describe the symptoms, the diagnostic procedure and treatment of ACS in children. The aim of this study was to analyse the diagnostic procedures in children compared to adolescents with ACS to obtain evidence for the diagnosis, treatment and outcome of children with ACS. Twenty-four children and adolescents with ACS have been treated at the Department of Trauma Surgery of the Medical University of Vienna, Austria. Two age-related groups were investigated to compare the diagnostic and therapeutic algorithm: group A comprising children aged 2-14 years (n = 12) and group B comprising adolescents aged 15-18 years (n = 12). Patient characteristics, diagnosis and therapy-associated data, complications and clinical outcome were analysed. In both groups we found fractures in most of our patients (n = 19) followed by contusion of the soft tissues (n = 3). In group A most of our patients were injured as pedestrians in car accidents (n = 5) followed by low-energy blunt trauma (n = 3). The most common region of injury and traumatic ACS was the lower leg (n = 7) followed by the feet (n = 3). For fracture stabilisation most of the patients (n = 6) received an external fixator. The mean time from admission to the fasciotomy was 27.9 hours. In four patients a compartment pressure measurement was performed with pressure levels from 30 to 75 mmHg. A histological examination of soft tissue was performed in five patients. From fasciotomy to definitive wound closure 2.4 operations were necessary. The mean hospital stay was 18.9 days. In group B most of our patients had a motorcycle accident (n = 5). The most common region for traumatic ACS in this group was also the lower leg (n = 9). In most of the patients (n = 6) intramedullary nails could be implanted. The mean time from admission to the fasciotomy was 27.1 hours. In six patients a compartment pressure measurement was performed with pressures from 25 to 90 mmHg. In five patients a histological examination was performed. From fasciotomy to definitive wound closure 2.3 operations were necessary. The mean hospital stay was 18.4 days. Secondary fasciotomy closure was performed in all cases. A split-skin graft was only necessary in three patients (13%). We avoided primary closure in the same setting when the fasciotomy was performed. Thus, we found no difference between the two groups in the diagnostic procedures, the indication for fasciotomy, the number of operations needed from fasciotomy to definitive wound closure, time of hospitalisation and clinical outcome. The rate of permanent complications was 4.2% (one patient from group A), which means that nearly all patients experienced full recovery after fasciotomy. ACS represents a surgical emergency and the indication should be determined early even in doubtful cases to avoid complications.

Fractures of the head and neck of the femur in children: an outcome study.

Fractures of the head and neck of the femur in children are very rare, occurring only after a high-velocity trauma, e.g. a fall from a height. This analysis shows the clinical course of traumatic femoral head and neck fractures in paediatric patients. Predisposing factors for poor outcome or fracture complications, such as non-union or femoral head necrosis, are described. Between 1993 and 2006, 16 paediatric patients with proximal femoral fractures were treated at the Level One Trauma Centre of the Medical University of Vienna. The minimum follow-up was two years. Inclusion criteria were age less then 16 years, intact growth plate and a proximal femoral fracture according to the classification by Delbet and Colonna. Exclusion criteria were pathological fractures or fractures of the subtrochanteric region (6/16). Ten patients met the inclusion criteria. Two patients were lost to follow-up. Therefore eight patients were included in the study. All patients except one were operated upon within 48 h after the injury ("primary") and healed without further complications. A single case was managed by "secondary" surgical treatment, two weeks after the initial trauma resulting in femoral head necrosis that healed without any subjective complaints. This case series confirms the importance of early surgical fixation of proximal femoral fractures in paediatric patients. An operative intervention later then 48 h after the initial trauma may increase the risk of complications such as femoral head necrosis, particularly in Delbet type I fractures (traumatic slipped capital femoral epiphysis).

Management and outcome of interprosthetic femoral fractures.

INTRODUCTION: Interprosthetic femoral fractures following ipsilateral hip and knee arthroplasty are a rare but serious complication in clinical practice. In most cases, adequate management of these injuries might constitute a challenging problem. However, the literature provides only few data regarding the treatment and outcome of interprosthetic femoral fractures, and there are only few classifications available, which might assist in finding an appropriate treatment concept. The purpose of this study was to analyse our experience in the management of interprosthetic femoral fractures following ipsilateral hip and knee joint replacement. MATERIALS AND METHODS: We reviewed the clinical and radiographic records of 23 patients (15 female and eight male, average age: 79.2 years) with an interprosthetic fracture after ipsilateral hip and knee joint replacement between 1992 and 2008. For the classification of interprosthetic femoral fractures, the fractures were divided into three types, depending on the fracture site and the adjacency to the prostheses. All patients underwent operative stabilisation, either by lateral plate fixation (n=19), by revision arthroplasty using a long stem (n=2) or by plate fixation and revision arthroplasty (n=2). RESULTS: Referring to the clinical outcome, 16 patients returned to their pre-injury activity level and were satisfied with their clinical outcome. In six patients, we saw a relevant decrease of hip or knee function and severe limitations in gait and activities of daily living. We had a mean Harris Hip Score (HHS) of 78.4 points, and a mean Knee injury and Osteoarthritis Outcome Score (KOOS) of 71.8 points. Relating to the radiographic outcome, successful fracture healing was achieved in 19 of 22 patients (86%) within 6 months. Failures of reduction and fixation were noted in four (18%) of 22 patients. CONCLUSION: We had a satisfactory outcome following individualised treatment of interprosthetic femoral fractures following ipsilateral hip and knee joint replacement. Compared to the rare data in current literature, we had promising functional result and high rate of bony fusion. Regarding the complexity and challenges in many of these cases, interprosthetic fractures require an adequate analysis of the fracture aetiology and a suitable transfer into the best possible treatment concept.

Surgery for pathological proximal femoral fractures, excluding femoral head and neck fractures: resection vs. stabilisation.

Pathological femoral head and neck fractures are commonly treated by arthroplasty. Treatment options for the trochanteric region or below are not clearly defined. The purpose of this retrospective, comparative, double-centre study was to analyse survival and influences on outcome according to the surgical technique used to treat pathological proximal femoral fractures, excluding fractures of the femoral head and neck. Fifty-nine patients with 64 fractures were operated up on between 1998 and 2004 in two tertiary referral centres and divided into two groups. One group (S, n = 33) consisted of patients who underwent intramedullary nailing alone, and the other group (R, n = 31) consisted of patients treated by metastatic tissue resection and reconstruction by means of different implants. Median survival was 12.6 months with no difference between groups. Surgical complications were higher in the R group (n = 7) vs. the S group (n = 3), with no statistically significant difference. Patients with surgery-related complications had a higher survival rate (p = 0.049), as did patients with mechanical implant failure (p = 0.01). Survival scoring systems did not correlate with actual survival. Resection of metastases in patients with pathological fractures of the proximal femur, excluding femoral head and neck fractures, has no influence on survival. Patients with long postoperative survival prognosis are at risk of implant-related complications.

The influence of scaffold architecture on chondrocyte distribution and behavior in matrix-associated chondrocyte transplantation grafts.

Scaffold architecture and composition are important parameters in cartilage tissue engineering. In this in vitro study, we compared the morphology of four different cell-graft systems applied in clinical cartilage regeneration and analyzed the cell distribution (DAPI nuclei staining) and cell-scaffold interaction (SEM, TEM). Our investigations revealed major differences in cell distribution related to scaffold density, pore size and architecture. Material composition influenced the quantity of autogenous matrix used for cellular adhesion. Cell bonding was further influenced by the geometry of the scaffold subunits. On scaffolds with widely spaced fibers and a thickness less than the cell diameter, chondrocytes surrounded the scaffold fibers with cell extensions. On those fibers, chondrocytes were spherical, suggesting a differentiated phenotype. Fiber sizes smaller than chondrocyte size, and widely spaced, are therefore beneficial in terms of improved adhesion by cell shape adaptation. They also support the differentiated stage of chondrocytes by preventing the fibroblast-like and polygonal cell shape, at least briefly.