Vancouver B2 Fractures Research Articles

On optimization of a composite bone plate using the selective stress shielding approach

Bone fracture plates are used to stabilize fractures while allowing for adequate compressive force on the fracture ends. Yet the high stiffness of conventional bone plates significantly reduces compression at the fracture site, and can lead to subsequent bone loss upon healing. Fibre-reinforced composite bone plates have been introduced to address this drawback. However, no studies have optimized their configurations to fulfill the requirements of proper healing. In the present study, classical laminate theory and the finite element method were employed for optimization of a composite bone plate. A hybrid composite made of carbon fibre/epoxy with a flax/epoxy core, which was introduced previously, was optimized by varying the laminate stacking sequence and the contribution of each material, in order to minimize the axial stiffness and maximize the torsional stiffness for a given range of bending stiffness. The initial 14×414 possible configurations were reduced to 13 after applying various design criteria. A comprehensive finite element model, validated against a previous experimental study, was used to evaluate the mechanical performance of each composite configuration in terms of its fracture stability, load sharing, and strength in transverse and oblique Vancouver B1 fracture configurations at immediately post-operative, post-operative, and healed bone stages. It was found that a carbon fibre/epoxy plate with an axial stiffness of 4.6MN, and bending and torsional stiffness of 13 and 14N·m2, respectively, showed an overall superiority compared with other laminate configurations. It increased the compressive force at the fracture site up to 14% when compared to a conventional metallic plate, and maintained fracture stability by ensuring the fracture fragments’ relative motions were comparable to those found during metallic plate fixation. The healed stage results revealed that implantation of the titanium plate caused a 40.3% reduction in bone stiffness, while the composite plate lowered the stiffness by 32.9% as compared to the intact femur. This study proposed a number of guidelines for the design of composite bone plates. The findings suggest that a composite bone plate could be customized to allow for moderate compressive force on the fracture ends, while remaining relatively rigid in bending and torsion and strong enough to withstand external loads when a fracture gap is present. The results indicate that the proposed composite bone plate could be a potential candidate for bone fracture plate applications.

The biomechanical effect of bone quality and fracture topography on locking plate fixation in periprosthetic femoral fractures

Optimal management of periprosthetic femoral fractures (PFF) around a well fixed prosthesis (Vancouver B1) remains controversial as adequate fixation needs to be achieved without compromising the stability of the prosthesis. The aim of this study was to highlight the effect of bone quality i.e. canal thickness ratio (CTR), and fracture topography i.e. fracture angle and its position in relation to the stem, on the biomechanics of a locking plate for a Vancouver B1 fracture. A previously corroborated simplified finite element model of a femur with a cemented total hip replacement stem was used in this study. Canal thickness ratio (CTR) and fracture topography were altered in several models and the effect of these variations on the von Mises stress on the locking plate as well as the fracture displacement was studied. Increasing the CTR led to reduction of the von Mises stress on the locking plate as well as the fracture movement. In respect to the fracture angle with the medial cortex, it was shown that acute angles resulted in lower von Mises stress on the plate as opposed to obtuse angles. Furthermore, acute fracture angles resulted in lower fracture displacement compared to the other fractures considered here. Fractures around the tip of the stem had the same biomechanical effect on the locking plate. However, fractures more distal to the stem led to subsequent increase of stress, strain, and fracture displacement. Results highlight that in good bone quality and acute fracture angles, single locking plate fixation is perhaps an appropriate management method. On the contrary, for poor bone quality and obtuse fracture angles alternative management methods might be required as the fixation might be under higher risk of failure. Clinical studies for the management of PFF are required to further support our findings.

A Systematic Review of Open Reduction and Internal Fixation of Periprosthetic Femur Fractures With or Without Allograft Strut, Cerclage, and Locked Plates

Few comparative studies exist for open reduction and internal fixation of Vancouver B1 and C fractures. We therefore performed a systematic review of fractures treated with or without an allograft strut, and using various fixation techniques. Thirty-seven manuscripts including 682 fractures were identified between 1992 and 2012. Percent union was similar for Vancouver B1 fractures treated with or without an allograft strut (90.7% vs. 91.5%). Time to union (4.4 vs. 6.6months) and deep infection (3.8% vs. 8.3%) were increased with use of allograft struts. Percent union and time to union were unaffected by plate type or use of cerclage. We conclude that due to increased infection and time to union, allograft struts should be used cautiously during operative treatment of Vancouver B1 factures.

A biomechanical study on proximal plate fixation techniques in periprosthetic femur fractures

IntroductionProximal plate fixation is a crucial factor in osteosynthesis of periprosthetic femur fractures. Stability and strength of different fixation concepts for proximal plate fixation were compared. Materials and methodsTwelve fresh frozen, bone mineral density matched human femora, instrumented with cemented hip endoprosthesis were osteotomized simulating a Vancouver B1 fracture. Specimens were instrumented with locking compression plates, fixed proximally with either locking attachment plate (LAP), monocortical screws, cerclage plus monocortical screws (1cerclage) or cerclages only (4cerclages). Cyclic testing was performed with monotonically increasing load until failure. Relative movements at the proximal plate–femur interface were registered by motion tracking. ResultsThe LAP construct exhibited a significantly longer cumulative survival (failure criterion 1mm separation at the proximal plate fixation) compared to the monocortical (p=0.048) and 4cerclages constructs (p=0.012) but not to 1cerclage constructs. ConclusionBicortical screw anchorage improves proximal plate fixation in periprosthetic fractures. The cerclage–screw combination is a valuable alternative especially in osteoporotic bone.

Fixation of Fractures Around Unstable Hip Implants

As the rate of total hip replacement has escalated so has the rate of periprosthetic fractures, now reported to range between 0.1% and 18%. Typical periprosthetic fractures occur in older patients after low-energy falls, often in the context of osteoporosis and loose implants. Prevention and prophylaxis is the best approach but when a fracture occurs, Vancouver B2 fractures have typically showed better results with revision surgery compared with fixation, with reoperation rates reported from 18% to 33% with fixation. Although revision is presently accepted as the standard of care when the prosthetic stem is deemed loose or unstable, we propose that in frail, severely comorbid or debilitated geriatric patients with limited ambulatory status at baseline, urgent treatment with fixation to restore the stability of the preexisting implant may be an option. We propose that in analogy to the debilitated hip fracture patient, this patient population may benefit from prompt surgery within 24 to 48 hours with a goal of restoring stability and early mobilization. The lateral approach to the femur allows complete access to the bony anatomy and provides an extensile approach to the hip. Once the vastus is elevated, the fracture can easily be identified, explored, and implant stability can be assessed under direct visualization. If implant stability can be restored with anatomic reduction, the fracture can then be fixed with absolute stability technique around the stem. If comminution is present distal to the stem, relative stability technique can be used by bridging with a long lateral plate. If implant stability cannot be restored, revision remains an option. We propose that a shared decision process for fixation versus revision be done on a patient-by-patient basis. This process should include the patient, family, and surgeon and involve a frank assessment of patient needs and expectations, particularly in the frail patient with limited preexisting mobility.

Comment on article “Cement-in-Cement Revision for Selected Vancouver Type B1 Femoral Periprosthetic Fractures: A Biomechanical Analysis”

Comment on article “Cement-in-Cement Revision for Selected Vancouver Type B1 Femoral Periprosthetic Fractures: A Biomechanical Analysis”

RESULTS OF TREATMENT OF PERIPROSTHETIC FEMORAL FRACTURES AFTER TOTAL HIP ARTHROPLASTY

Periprosthetic fractures are the third most common reason for revision total hip arthroplasty. Surgical treatment of periprosthetic fractures belongs to the most difficult procedures due to the extensive surgery, elderly polymorbid patients and the high frequency of other complications. The aim of this study was to evaluate the results of operatively treated periprosthetic femoral fractures after total hip arthroplasty. We evaluated 47 periprosthetic fractures in 40 patients (18 men and 22 women) operated on between January 2004 and December 2010. The mean follow-up period was 27 months (within a range of 12-45 months). For the clinical evaluation, we used modified Merle d'Aubigné scoring system. In group of Vancouver A fractures, 3 patients were treated with a mean score of 15.7 points (good result). We recorded a mean score of 14.2 points (fair result) in 6 patients with Vancouver B1 fractures, 12.4 points (fair result) in 24 patients with Vancouver B2 fractures and 12.7 points (fair result) in 7 patients with Vancouver B3 fractures. In group of Vancouver C fractures, we found a mean score of 16.2 points (good result) in 7 patients. Therapeutic algorithm based on the Vancouver classification system is, in our opinion, satisfactory. Accurate differentiation of B1 and B2 type of fractures is essential. Preoperative radiographic images may not be reliable. If in doubt, checking the stability of the prosthesis fixation during surgery should be performed.

Treatment of Vancouver B1 fractures—contemporary principles for the use of locking plates

A number of factors complicate the treatment of periprosthetic fractures of the proximal femur. These include bonequality, fixationofthe stem, relationofthe fracturetothe stem, healing potential of the bone and the patient's future risk of another fall. Vancouver type B1 fractures are commonly fixed with locking plates, but even though results have im- proved, complication rate is still rather high. Recent studies suggest that most complications can be avoided if contempo- rary principles are followed; these include anatomical reduc- tion of the fracture, using long plates from the major trochanter to the supracondylar area and improved fixation over the stem. Studies are small and retrospective and further studies are necessary for more definitive conclusions.

Angulated locking plate in periprosthetic proximal femur fractures: biomechanical testing of a new prototype plate

To improve proximal plate fixation of periprosthetic femur fractures, a prototype locking plate with proximal posterior angulated screw positioning was developed and biomechanically tested. Twelve fresh frozen, bone mineral density matched human femora, instrumented with cemented hip endoprosthesis were osteotomized simulating a Vancouver B1 fracture. Specimens were fixed proximally with monocortical (LCP) or angulated bicortical (A-LCP) head-locking screws. Biomechanical testing comprised quasi-static axial bending and torsion and cyclic axial loading until catastrophic failure with motion tracking. Axial bending and torsional stiffness of the A-LCP construct were (1,633 N/mm ± 548 standard deviation (SD); 0.75 Nm/deg ± 0.23 SD) at the beginning and (1,368 N/mm ± 650 SD; 0.67 Nm/deg ± 0.25 SD) after 10,000 cycles compared to the LCP construct (1,402 N/mm ± 272 SD; 0.54 Nm/deg ± 0.19 SD) at the beginning and (1,029 N/mm ± 387 SD; 0.45 Nm/deg ± 0.15) after 10,000 cycles. Relative movements for medial bending and axial translation differed significantly between the constructs after 5,000 cycles (A-LCP 2.09° ± 0.57 SD; LCP 5.02° ± 4.04 SD; p = 0.02; A-LCP 1.25 mm ± 0.33 SD; LCP 2.81 mm ± 2.32 SD; p = 0.02) and after 15,000 cycles (A-LCP 2.96° ± 0.70; LCP 6.52° ± 2.31; p = 0.01; A-LCP 1.68 mm ± 0.32; LCP 3.14 mm ± 0.68; p = 0.01). Cycles to failure (criterion 2 mm axial translation) differed significantly between A-LCP (15,500 ± 2,828 SD) and LCP construct (5,417 ± 7,236 SD), p = 0.03. Bicortical angulated screw positioning showed less interfragmentary osteotomy movement and improves osteosynthesis in periprosthetic fractures.

A unique peri-prosthetic fracture pattern in well fixed femoral stems with polished, tapered, collarless design of total hip replacement

Peri-prosthetic fractures (PPF) are a recognised complication following hip arthroplasty. Prosthesis design and type influence PPF pattern. Surgeons rely on classification systems, such as the Vancouver, to aid treatment planning. This study highlights a specific fracture pattern that occurs with cemented well-fixed polished, tapered, collarless (PTC) stems. We reviewed a consecutive series of 21 PPF around well fixed PTC stems. The majority of the fractures were classified pre-operatively as Vancouver B2 (14/21), but there were also B1 (6/21) and A type fractures. The B2 fractures had common radiological and intra-operative findings: a spiral fracture with extensive fragmentation of bone and cement, debonding of cement from the implant, cement fracture, and a well-fixed cement–bone interface. Reconstruction of these fractures was more difficult than suggested by the radiographs. Two of the six patients who were considered to have a Vancouver B1 fracture underwent open reduction and internal fixation (ORIF), and had treatment-related complications. Retrospective review of the radiographs showed subtle features, such as subsidence of the stem into the centraliser, that are characteristic of a B2 fracture pattern. In summary, it is important to recognise this fracture pattern around secure PTC stems in order to prevent misinterpretation of the fracture as a Vancouver B1 rather than a B2, leading to failure of treatment, and to alert the surgeon that complex reconstruction will be required because of the extensive fragmentation.

Treatment of special proximal femoral fractures with less invasive stabilization system

Objective To discuss the indications, surgical techniques and outcome of less invasive stabilization system (LISS) in treatment of special proximal femoral fractures. Methods Twenty-eight patients with special proximal femoral fractures were treated with LISS from June 2005 to December 2007. All fractures could not be reduced by close reduction with traction table. There were eight patients with in-tertrochanterie fractures ( including type 31-A2.2 fractures in three, type 31-A2.3 in two, type 31-A3.1 in three and type 31-A3.3 in two according to AO classification), 19 with subtrochanteric fractures (including type ⅡA fractures in three, type ⅢB in one and type Ⅴ in 15 according to Seinsheimer classification) and one with peripheral fractures ( type Vancouver B1 fracture) of the femoral prosthesis. The data about opera-tion duration, intraoperative blood loss, postoperative complications, fracture healing time and postoperative hip function score were recorded. Results The operation lasted for mean 88 minutes (45-120 minutes), with intra-operative blood loss of average 320 ml (50 -700 ml). There occurred deep vein thrombosis of lower limb in two patients, myocardial infarction in one and lower digestive tract bleeding in one after oper-ation, with no incision complications. One patient with breast cancer was died of brain metastasis after op-eration and three lost follow-up. Other 24 patients were followed up for mean 18 months (6-33 months), which showed that 23 patients got fracture healing 2-5 months ( average 3 months) postoperatively but that one patient with type Seinsheimer V fracture had breakage of proximal locking screws six months postopera-tively because of nonunion of subtrochanteric fracture. The Harris score of the hip was 70-99 points ( aver-age 84 points). Conclusions Reverse femoral LISS has advantages of minimal invasion, easy opera-tion, stable fixation, high degree of safety and minor complications for treatment of special proximal femoral fractures. Skillful reduction, correct positioning of guide wire into hole A and avoidance of immediate weight bearing are key to success of the operation. Key words: Femoral fractures; Fracture fixation, intramedullary; Less invasive stabilizationsystem