Biomechanical assessment of composite versus metallic intramedullary nailing system in femoral shaft fractures: A finite element study

BACKGROUND

Intramedullary nails are the primary choice for treating long bone fractures. However, complications following nail surgery including non-union, delayed union, and fracture of the bone or the implant still exist. Reducing nail stiffness while still maintaining sufficient stability seems to be the ideal solution to overcome the abovementioned complications.

METHODS

In this study, a new hybrid concept for nails made of carbon fibers/flax/epoxy was developed in order to reduce stress shielding. The mechanical performance of this new implant in terms of fracture stability and load sharing was assessed using a comprehensive non-linear FE model. This model considers several mechanical factors in nine fracture configurations at immediately post-operative, and in the healed bone stages.

RESULTS

Post-operative results showed that the hybrid composite nail increases the average normal force at the fracture site by 319.23N (P<0.05), and the mean stress in the vicinity of fracture by 2.11MPa (P<0.05) at 45% gait cycle, while only 0.33mm and 0.39mm (P<0.05) increases in the fracture opening and the fragments' shear movement were observed. The healed bone results revealed that implantation of the titanium nail caused 20.2% reduction in bone stiffness, while the composite nail lowered the stiffness by 11.8% as compared to an intact femur.

INTERPRETATION

Our results suggest that the composite nail can provide a preferred mechanical environment for healing, particularly in transverse shaft fractures. This may help bioengineers better understand the biomechanics of fracture healing, and aid in the design of effective implants.

The effects of spinal cord injury on bone healing in patients with femoral fractures

BACKGROUND

Orthopedic literature states that fractures of long bones, when associated with traumatic brain injuries, frequently heal with excessive callus and faster than normal. Few studies, however, have reported these phenomena being induced by spinal cord injury (SCI). Our objective is to compare the extent of callus and the rate of healing of long-bone fractures in patients with or without SCI. Subgroup comparisons were performed among the patients with SCI in terms of different levels of SCI.

METHODS

The final mean volume of callus formation and the rate of union of nailed fractures of the femur were determined radiologically in 22 femoral fracture patients with SCI (seven cervical, six thoracic, and nine lumbar spine injury) and compared with those in a group of 22 patients with similar types of fractures but without SCI.

RESULTS

The final mean callus volume in the fracture/SCI group was significantly higher than the fracture-only group (P < 0.001). The fractures in the fracture/SCI group united in an average time of 22.86 weeks compared with 25.04 weeks in the fracture-only group (P < 0.05). We observed 84.6% (11 of 13) of patients with cervical and thoracic SCI patients with accelerated fracture healing (cervical 6 of 7, thoracic 5 of 6), but only 44.4% (4 of 9) of patients with lumbar SCI appeared to show this phenomenon (P < 0.05).

CONCLUSIONS

These results confirm that SCI may be associated with accelerated fracture healing and enhanced callus formation. Furthermore, our study revealed a trend toward enhanced osteogenesis in cervical or thoracic SCI compared with lumbar SCI.

How accurately can we predict the fracture load of the proximal femur using finite element models?

BACKGROUND

Current clinical methods for fracture prediction rely on two-dimensional imaging methods such as dual-energy X-ray absorptiometry and have limited predictive value. Several researchers have tried to integrate three-dimensional imaging techniques with the finite element (FE) method to improve the accuracy of fracture predictions. Before FE models could be used in clinical settings, a thorough validation of their accuracy is required. In this paper, we try to evaluate the current state of accuracy of subject-specific FE models that are used for prediction of the fracture load of proximal femora.

METHODS

All the studies that have used FE for prediction of fracture load and have compared the predicted fracture load with experimentally measured fracture loads in vitro are identified through a systematic search of the literature. A quantitative analysis of the results of those studies has been carried out to determine the absolute prediction error, percentage error, and linear correlations between predicted and measured fracture loads.

FINDINGS

The reported coefficients of determination (R(2)) vary between 0.773 and 0.96 while the percentage error in prediction of fracture load varies between 5 and 46% with most studies reporting percentage errors between 10 and 20%.

INTERPRETATION

We conclude that FE models, which are currently used only experimentally, are in general more accurate than clinically used fracture risk assessment techniques. However, the accuracy of FE models depends on the details of their modeling methodologies. Therefore, modeling procedures need to be optimized and standardized before FE could be used in clinical settings.

Biomechanical analyses of static and dynamic fixation techniques of retrograde interlocking femoral nailing using nonlinear finite element methods

Femoral shaft fractures can be treated using retrograde interlocking nailing systems; however, fracture nonunion still occurs. Dynamic fixation techniques, which remove either the proximal or distal locking screws, have been used to solve the problem of nonunion. In addition, a surgical rule for dynamic fixation techniques has been defined based on past clinical reports. However, the biomechanical performance of the retrograde interlocking nailing systems with either the traditional static fixation technique or the dynamic fixation techniques has not been investigated by using nonlinear numerical modeling. Three-dimensional nonlinear finite element models were developed, and the implant strength, fixation stability, and contact area of the fracture surfaces were evaluated. Three types of femoral shaft fractures (a proximal femoral shaft fracture, a middle femoral shaft fracture, and a distal femoral shaft fracture) fixed by three fixation techniques (insertion of all the locking screws, removal of the proximal locking screws, or removal of the distal locking screws) were analyzed. The results showed that the static fixation technique resulted in sufficient fixation stability and that the dynamic fixation techniques decreased the failure risk of the implant and produced a larger contact area of the fracture surfaces. The outcomes of the current study could assist orthopedic surgeons in comprehending the biomechanical performances of both static and dynamic fixation techniques. In addition, the surgeons could also select a fixation technique based on the specific patient situation using the numerical outcomes of this study.

Hip spica versus Rush pins for management of femoral diaphyseal fractures in children

BACKGROUND

Femoral fractures are common in children between 2 and 12 years of age and 75% of the lesions affect the femoral shaft. Traction followed by a plaster cast is universally accepted as conservative treatment. We compared primary hip spica with closed reduction and fixation with retrogradely passed crossed Rush pins for diaphyseal femur fracture in children. The hypothesis was that Rush pin might provide better treatment with good clinical results in comparison with primary hip spica.

MATERIALS AND METHODS

Fifty children with femoral fractures were evaluated; 25 of them underwent conservative treatment using immediate hip spica (group A) and 25 were treated with crossed retrograde Rush pins (group B). The patients ages ranged from 3 to 13 years (mean of 9 years).

RESULTS

Mean duration of fracture union was 15 weeks in group A and 12 weeks in group B. Mean duration of weight bearing 14 weeks in group and 7 weeks in group B. Mean hospital stay was 4 days in group A and 8 days in group B. Mean followup period in group A was 16 months and group B was 17 months. Complications such as angulation, shortening, infection were compared.

CONCLUSIONS

Closed reduction and internal fixation with crossed Rush pins was superior in terms of early weight bearing and restoration of normal anatomy.

Floating knee injuries: Results of treatment and outcomes

BACKGROUND

Floating knee, referred to as ipsilateral fractures of the femur and tibia, is usually associated with several complications and mortality. This study was designed to present our experience with treatment of this injury throughout; age, sex, mechanism of injury, associated injuries, method and results of treatment, and complications of floating knee are discussed.

MATERIALS AND METHODS

This retrospective study was performed between January 2006 and December 2011. All patients with floating knee injuries who were admitted to the referral educational hospitals were included. The information about the 238 cases of floating knee injuries were gathered through the 254,620 trauma files and after excluding 18 patients who died within 6 months, the remaining files were studied and the target information was recorded.

RESULTS

The most frequent age group was 20-29 years (44.5%). The floating knee injuries were more common in males (85.5%). Type (D) according to "the classification of Letts and Vincent" was observed in 38.9% cases. The most frequent mechanism of injury was car to motorcycles accidents (48.2%). The most common associated injury was pelvic fractures (86.8%). Open reduction and internal fixation was the common type of treatment (70%). The most common early and late complications were knee hemarthrosis in 31 cases (14%) and knee osteoarthritis in 30 cases (13.6%), respectively. Death during the 5 years follow up was due to circulatory disruption, followed by deep vein thrombosis (61%). There was a significant relation between the age and outcomes as it worsens with age (P-value < 0.05).

CONCLUSION

This study revealed that the complication rate associated with floating knee injuries remained high, regardless of the used treatment regimen and surgeons should focus on reducing complications while treating it.

When femoral fracture fixation fails

Most hip fractures treated with modern internal fixation techniques will heal. However, failures occasionally occur and require revision procedures. Salvage strategies employed during revision are based on whether the fixation failure occurs in the femoral neck, or in the intertrochanteric region. Patient age and remaining bone stock also influence decision making. For fractures in young patients, efforts are generally focused on preserving the native femoral head via osteotomies and repeat internal fixation. For failures in older patients, some kind of hip replacement is usually selected. Disuse osteopenia, deformity, bone loss, and stress-risers from previous internal fixation devices all pose technical challenges to successful reconstruction. Attention to detail is important in order to minimise complications. In the majority of cases, good outcomes have been reported for the various salvage strategies.

Cite this article: Bone Joint J 2013;95-B, Supple A:7–10.

Minimally invasive fixation of type B and C interprosthetic femoral fractures

INTRODUCTION

Interprosthetic femoral fractures are rare and raise unresolved treatment issues such as the length of the fixation material that best prevents secondary fractures. Awareness of the advantages of locked-plate fixation via a minimally invasive approach remains limited, despite the potential of this method for improving success rates.

HYPOTHESIS

Femur-spanning (from the trochanters to the condyles) locked-plate fixation via a minimally invasive approach provides high healing rates with no secondary fractures.

MATERIALS AND METHODS

From January 2004 to May 2011, all eight patients seen for interprosthetic fractures were treated with minimally invasive locked-plate fixation. Mean time since hip arthroplasty was 47.5 months and mean time since knee arthroplasty was 72.6 months. There were 12 standard primary prostheses and four revision prostheses; 11 prostheses were cemented and a single prosthesis showed femoral loosening. Classification about the hip prostheses was Vancouver B in one patient and Vancouver C in seven patients; about the knee prosthesis, the fracture was SoFCOT B in three patients and SOFCOT C in five patients, and a single fracture was SoFCOT D. Minimally invasive locking-plate fixation was performed in all eight patients, with installation on a traction table in seven patients.

RESULTS

Healing was obtained in all eight patients, after a mean of 14 weeks (range, 12-16 weeks). One patient had malalignment with more than 5° of varus. There were no general or infectious complications. One patient died, 32 months after surgery. The mean Parker-Palmer mobility score decreased from 6.2 pre-operatively to 2.5 at last follow-up. Early construct failure after 3 weeks in one patient required surgical revision. There was no change in implant fixation at last follow-up. No secondary fractures were recorded.

DISCUSSION

In patients with type B or C interprosthetic fractures, femur-spanning fixation not only avoids complications related to altered bone stock and presence of prosthetic material, but also decreases the risk of secondary fractures by eliminating stress riser zones. The minimally invasive option enhances healing by preserving the fracture haematoma. Thus, healing was obtained consistently in our patients, with no secondary fractures, although the construct failed in one patient.

LEVEL OF EVIDENCE

Level IV.

Intraoperative measurement of bone electrical potential: a piece in the puzzle of understanding fracture healing

INTRODUCTION

Bone electrical potentials change with the force applied. Also, fracture alters the bone electrical potential, so it becomes more electronegative. These potentials have an important role in fracture healing, bone growth and remodelling. Literature data on the influence of fracture operative treatment on bone electrical potentials, and possible consequences of this influence, are sparse. The objective of this study was to establish a method of intraoperative bone potential measurement, and to try to find a correlation between electrical potential and fracture type, osteosynthesis method and prognosis.

PATIENTS AND METHODS

52 patients with a pertrochanteric fracture were included in the study. Bone electrical potentials were measured intraoperatively using a thin Kirschner wire introduced through bone cortex at the selected point and pointed to opposite cortex, not penetrating it. Kirschner wires were connected using clamps to multimeter (YF-78 Multimeter) device. Neutral electrode (inductive rubber) was placed behind ipsilateral gluteus.

RESULTS

Near the fracture site potentials of -199 up to -267 mV were recorded. Mean measured potential of bone plate after fixation was -240 mV. Bone potentials correlated with the subtype of fracture and early mobilisation of patients.

CONCLUSIONS

Bone potentials, caused by fracture, can be measured intraoperatively; the operative procedure appears to influence their generation. Measured potentials depend on the fracture type, and could be correlated with prognosis.

Cytokine productive capacity of alveolar macrophages and Kupffer cells after femoral fracture and blunt chest trauma in a murine trauma model

INTRODUCTION

Specific cellular and inflammatory factors that contribute to the severity of pulmonary dysfunction after blunt chest trauma and osteosynthesis of femoral fractures are yet not fully understood. Therefore, we investigated alterations of the cytokine productive capacity of alveolar macrophages (AM) and Kupffer cells (KC) after femoral fracture stabilized with intramedullary pin with or without blunt chest trauma.

MATERIALS AND METHODS

In male C57BL/6N mice an intramedullary pin was implanted in an intact femur as the sham procedure. In trauma groups mice either received an isolated femoral fracture with subsequent fracture stabilization with an intramedullary pin (group Fx) or a combined trauma of blunt chest trauma and femur fracture also stabilized by an intramedullary pin (group TTFx). Animals were sacrificed 0h, 6h, 12h, 24h and 3d after trauma induction. Cytokine concentrations were measured in plasma and supernatant of cultivated AM and KC by FACS analysis. Pulmonary and hepatic infiltration of polymorphonuclear leukocytes (PMN) was determined by Ly6G-staining.

RESULTS

At 6h, isolated femoral fracture with intramedullary stabilization resulted in a significantly increased productive capacity of KC (IL-6, TNF-α, CCL2, CCL3, CCL5 and CCL7) compared to sham animals. Combined trauma additionally resulted in an increased productive capacity of AM (IL-6, TNF-α, CCL2, CCL3, CCL4, CCL5 and CCL7) at 6h and the effect was prolonged up to 3d compared to controls. Combined trauma also led to a significant higher amount of plasma CCL2 at 3d and plasma CCL7 at 6h after the insult compared to group Fx. Compared to shams, pulmonary and hepatic infiltrations of PMNs were increased in group Fx and TTFx after 6h, but in the combined trauma model the effect was prolonged up to 3d.

CONCLUSION

An intramedullary stabilized femur fracture alone results in a significant activation of the immune response. The combination of femoral fracture and blunt chest trauma however, results in an increased and prolonged activation of the inflammatory response. Transferred to the clinical setting, these results emphasize the critical role of severe chest trauma for treatment strategies of femoral fractures in multiple trauma patients.

Flexible intramedullary nailing for distal femoral fractures in patients with myopathies

PURPOSE

Distal femoral fractures are quite common in nonambulating patients with myopathies, as they present marked osteoporosis. The deterioration of preexisting knee flexion contracture is a known problem, as these fractures are usually angulated posteriorly. The goals of treatment are to reduce immobilization and bed rest to a minimum, prevent function loss, and prevent refracture. The aim of our work was to investigate if these goals can be achieved by an operative treatment with closed reduction and flexible intramedullary nailing (FIN).

METHODS

Six distal femoral fractures in four nonambulating patients with myopathies (three Duchenne muscular dystrophy and one nemaline myopathy) were treated with FIN between 2005 and 2011. Patient charts and radiographs were reviewed to determine if intra- or postoperative complications occurred and to detect the interval to wheelchair mobilization and hospital discharge. Pre- and postoperative knee flexion contracture was noted from the patient charts of our reeducation unit, where patients were already known preoperatively.

RESULTS

Wheelchair mobilization without further immobilization after an interval of 2-3 days was possible. No aggravation of knee flexion contracture was detected in our patient series. No complications associated to the operative treatment itself and no refractures in the follow up occurred.

CONCLUSION

Our experience showed that FIN is a low invasive and sufficiently stable osteosynthesis in such fractures. Left in place, nails will reinforce mechanical stability.

Navigation-assisted total knee arthroplasty for the knee retaining femoral intramedullary nail, and distal femoral plate and screws

Proper ligament balancing, restoration of the mechanical axis and component alignment are essential for the success and longevity of a prosthesis. In conventional total knee arthroplasty (TKA), an intramedullary guide is used to improve the alignment. An extramedullary guide can be used in cases of severe femoral bowing or intramedullary nailing but its use is more subjective and relies on the surgeon's experience. This paper reports two successful cases of navigation-assisted TKA for severe right knee osteoarthritis retaining a femoral intrameullary nail, and left knee osteoarthritis retaining a distal femoral plate.

Malunion following flexible intramedullary nails for tibial and femoral fractures in adolescents

PURPOSE

Flexible intramedullary nails (FIN) are increasingly used in the management of paediatric tibial and femoral fractures. Concerns have recently been raised regarding the use of FIN in older children. The aim of this study was to determine how effective FIN is in treating tibial and femoral fractures in adolescents.

METHODS

Patients aged 11 years or older undergoing FIN for tibial and femoral fractures between 2003 and 2009 were identified. Radiographs and case notes were reviewed to identify complications.

RESULTS

Thirty-five consecutive adolescent patients underwent FIN for tibial (n = 21) and femoral fractures (n = 15), with a mean age of 12.9 years. The mean radiographic follow up was 29 weeks. Sixty percent (60%, n = 9) and 38% (n = 9) of femoral and tibial fractures, respectively, malunited. Fracture severity was associated with increased malunion for both tibial and femoral fractures (P = 0.046 and P = 0.044, respectively). Two femoral fractures took longer than 20 weeks to unite and seven tibial fractures took longer than 16 weeks to unite.

CONCLUSION

The higher than expected rates of malunion and delayed union in this study suggest that other treatments should be considered when treating adolescents with unstable tibial or femoral fractures.

Retrograde intramedullary nailing for periprosthetic supracondylar fractures of the femur after total knee arthroplasty

BACKGROUND

Periprosthetic supracondylar fractures of the femur after total knee arthroplasty are not common but are usually difficult to treat due to the advanced age of patients and frequently accompanying osteoporosis. Retrograde intramedullary nailing can be effective in promoting healing of these fractures by providing sufficient stability, but the number of beneficiaries is small due to its limited applicability and the postoperative function has rarely been assessed. This study evaluated the efficacy of retrograde intramedullary nailing for the treatment of periprosthetic supracondylar fractures of the femur using the clinical outcomes.

METHODS

Between January 2000 and May 2006, 9 patients (10 knees) with periprosthetic supracondylar fractures of the femur underwent retrograde intramedullary nailing. An open reduction and additional fixation using a shape memory alloy ring were used in 3 of them in whom a closed reduction was not successful. The clinical and radiographic findings were reviewed retrospectively in 7 patients (8 knees), excluding 2 who were unavailable for a follow-up assessment due to death. The mean follow-up period was 39 months (range, 24 to 82 months). The union and alignment of the fracture were assessed radiographically. The postoperative function was evaluated using Sanders' criteria.

RESULTS

Radiographic union was obtained in all patients after an average of 13 weeks (range, 12 to 15 weeks) postoperatively. No postoperative infection, heterotopic ossification and component loosening were observed. After union, the coronal alignment averaged 0.1 degrees valgus (range, 3.6 degrees varus to 2.6 degrees valgus) and the mean sagittal alignment was 1.9 degrees of extension (range, 0.9 degrees of flexion to 6.3 degrees of extension). The mean range of motion was 103 degrees (range, 90 degrees to 120 degrees) postoperatively. At the last follow up, there were 1 excellent, 5 good and 2 fair results according to Sanders' criteria.

CONCLUSIONS

With retrograde intramedullary nailing, excellent fracture union and good functional recovery were obtained in patients with periprosthetic supracondylar fractures.

Plating of Femoral Shaft Fractures: the Experience in an African Teaching Hospital

BACKGROUND

Femoral shaft fractures are common presentation in our trauma units. It is obvious that all these fractures cannot be treated conservatively due to the pressure on trauma beds and thus a suitable method of internal fixation that is feasible in the environment has had to be adopted.

OBJECTIVE

This study is a report of our experience with plate fixation of femoral shaft fracture in our environment.

DESIGN

A retrospective hospital based study.

PATIENT AND METHOD

All patients with femoral shaft fractures stabilized with plates and screws between 1997 and 2004 at the University College Hospital were reviewed. The case notes were retrieved and data extracted from them; all case notes entry gave sufficient information.

RESULTS

The fracture pattern showed 56 cases (35.4%) of Type 32-A, 45 cases (28.5%) of Type 32-B and 57 cases (36.1%) of Type 32-C using AO classification. The outcome of treatment was excellent to good in 125 fractures (77.2%). The average time of healing was 20 weeks (range 16-48). Fracture related complications occurred in nine fractures (5.7%) which included deep infection in four fractures (2.5%) and implant failure in five fractures (3.2%).

CONCLUSION

Femoral shaft plating gives good result if the principles of fixation is carefully followed and in developing countries where initial cost of procurement of equipments for closed nailing may not be forth coming, it thus provide a safe efficient and low cost method of fixation of femoral shaft fracture.