Standard versus customised locking plates for fixation of schatzker ii tibial plateau fractures

Aim3D-printed implants could improve the capture of fracture fragments for improved stability of tibial plateau fracture fixation. The aim of this study was to compare the biomechanical strength of fixation constructs using standard and customised 3D-printed proximal tibial locking plates for fixation of tibial plateau fractures.MethodsThis is a biomechanical study utilising six pairs of cadaveric tibiae. Fractures were created in an identical fashion using an osteotome and mallet, and fixed using either a standard, commercially-available proximal tibia locking plate or a customised 3D-printed plate. Design and production of the customised plates followed a “3D printing at point-of-care” model. Customised stainless steel 316 L plates were produced within a local additive manufacturing laboratory based upon pre-operative CT scans. Determination of implant choice within each cadaver pair was performed via simple randomisation. Following fracture fixation, the tibiae were skeletalised and biomechanically tested using a customised loading jig and a size-matched femoral knee prosthesis. The constructs were loaded cyclically from 100 N to approximately three times the cadaveric body-weight at 5 Hz for 10 000 cycles. Every 1000 cycles, the test was paused and the tibia was physically checked for failure. If failure had not occurred by the end of the testing cycle, the construct was loaded to failure and the load at which the construct failed was noted.ResultsFixation constructs using the 3D-printed plates performed comparably to those using the standard plates. There was no significant difference in the degree of fracture fragment displacement in both constructs. Overall longitudinal construct stiffness and load to failure was higher in the 3D-plates group but this did not reach statistical significance.ConclusionProduction of customised plates for proximal tibia fractures at point-of-care is feasible, however fixation constructs with these plates did not provide any biomechanical advantage over standard plates in terms of axial loading stiffness.     

Percutaneous methods of tibial plateau fixation

Various methods of percutaneous fixation of tibial plateau fractures are available. The optimal method of fixation is dictated by soft tissue injury, fracture characteristics, and functional demands of the patient. Unicondylar fractures are amenable to percutaneous stabilization with screws or plates although some fractures are best approached with open techniques. Hybrid and ring external fixators are most appropriate for patients with bicondylar injuries who have severe soft tissue trauma. Use of intramedullary nails to align ipsilateral shaft fractures adjacent to percutaneously fixed plateau injuries remains controversial but may be indicated for some patients with bicondylar lesions and combined plateau and shaft fractures.     

Bicondylar tibial plateau fractures: a biomechanical study

The optimal treatment of bicondylar tibial plateau fractures remains controversial. The current study was designed to answer the following questions: (1) can a lateral fixed angle plate provide similar construct stability to dual plating techniques and (2) does the size of the medial buttress plate used in dual plating techniques have an effect on construct stability? Bicondylar tibial plateau fractures were created, reduced, and instrumented in a matched pair design using a cadaveric simulated bicondylar tibial plateau fracture model. Tibias were instrumented with one of three constructs: a lateral periarticular plate and posteromedial small fragment dynamic compression plate, a lateral periarticular plate and posteromedial (1/3)-tubular plate, or a lateral fixed angle plate. Biomechanical testing was done to determine construct stiffness, maximum load to failure, and medial condylar displacement for each of the three constructs. There was no significant difference measured between the two dual plating constructs and the lateral fixed angle plate for overall construct stiffness or with respect to medial condylar fragment displacement. A lateral fixed angle plate may have clinical applications in the treatment of bicondylar tibial plateau fractures.     

A surgical protocol for bicondylar four-quadrant tibial plateau fractures

Purpose

Bicondylar tibial plateau fractures involving four articular quadrants are severe and complex injuries, and they remain a challenging problem in orthopaedic trauma. The aim of this study was to introduce a new treatment protocol with dual-incision and multi-plate fixation in the floating supine patient position as well as to report the preliminary clinical results.

Methods

From January 2006 to December 2011, 16 consecutive patients with closed bicondylar four-quadrant tibial plateau fractures (Schatzker type VI, OTA/AO 41C2/3) were treated with posteromedial inverted L-shaped and anterolateral incisions. With the posteromedial approach, three quadrants (posteromedial, anteromedial and posterolateral) can be exposed, reduced and fixed with multiple small antiglide plates and short screws in an enclosure pattern. With the anterolateral approach, after articular elevation and bone substitute grafting, a strong locking plate with long screws to the medial cortex is used to raft-buttress the reduced lateral plateau fracture, hold the entire reconstructed tibial condyles together, and contact the condyles with the tibial shaft. All patients were encouraged to exercise knee motion at an early stage. The outcome was evaluated clinically and radiologically after a minimum two-year follow-up.

Results

The average operation time was 98?±?26 minutes (range 70–128) and the average duration of hospitalization was 29?±?8.6 days (range 20–41). Three cases used five plates, nine cases used four plates, and four cases used three plates. All patients were followed for a mean of 28.7?±?6.1 months (range 26–38). Fifteen incisions healed initially, while one patient developed a medial wound dehiscence and was successfully managed by debridement. All patients achieved radiological fracture union after an average of 20.2 weeks. At the two-year follow up, the average knee range of motion (ROM) was 98°?±?13.7 (range 88–125°), with a Hospital for Special Surgery (HSS) knee score of 87.7?±?10.3 (range 75–95), and SMFA score of 21.3?±?8.6 (range 12–33).

Conclusion

For bicondylar four-quadrant tibial plateau fractures, the treatment protocol of multiple medial-posterior small plates combined with a lateral strong locking plate through dual incisions can provide stable fracture fixation to allow for early stage rehabilitation. Good clinical outcomes can be anticipated.     

Functional outcomes of bicondylar tibial plateau fractures treated with dual buttress plates and risk factors: A case series

ObjectiveAlthough there are different ways to treat bicondylar tibial plateau fractures, treatment remains as a challenge to most orthopaedic surgeons. The purpose of this study was to assess the outcomes of dual buttress plates fixation in treatment of bicondylar tibial plateau fractures and to determine risk factors for outcome.MethodsClinical data for 74 patients with bicondylar tibial plateau fracture were retrospectively reviewed. Dual buttress plates were placed through two incisions. All patients were evaluated both radiographically and clinically according to Rasmussen scores and Hospital for Special Surgery (HSS) scores during the follow-up period. The data were analyzed using univariate analysis and multivariate logistic regression analysis to identify independent risk factors for functional outcome (Rasmussen functional score).ResultsRasmussen anatomic score was excellent in 34, good in 23, and fair in 17 patients. Sixty-nine patients were followed for a mean of 27 months. Functional results of excellent and good were obtained in 56(81.2%) patients by Rasmussen functional score and in 57 (82.6%) patients by HSS score. Univariate analysis showed Arbeitsgemeinschaft für Osteosynthesefragen (AO) fracture type and reduction quality were significantly related to functional results. Multivariate analysis showed that AO fracture type and reduction quality were independent risk factors for outcome.ConclusionDual buttress plates technique provided a favourable quality of fracture reduction and satisfactory clinical function. Appropriate selection for operation chance, limited soft tissue stripping and filling of osseous defects may lessen or prevent serious complications. Fracture reduction quality and AO fracture type were independent risk factors for clinical function.     

Frequency and fracture morphology of the posteromedial fragment in bicondylar tibial plateau fracture patterns

OBJECTIVES: Bicondylar tibial plateau fracture management remains therapeutically challenging, partly because of multiplanar articular comminution. This study was performed to evaluate the frequency and morphologic characteristics of the posteromedial fragment in this injury pattern. DESIGN: Retrospective chart and radiographic review. SETTING: Urban Level 1 university trauma center. PATIENTS: Fifty-seven patients sustaining 57 Orthopedic Trauma Association (OTA) C-Type bicondylar tibial plateau fractures formed the study group. MAIN OUTCOME MEASURE: Between May 2000 and March 2003, 170 OTA C-Type bicondylar tibial plateau fractures were identified using an orthopaedic database. One hundred and forty-six fractures had computed tomographic (CT) scans performed prior to definitive fixation and were reviewed using the Picture Archiving and Communication System (PACS). Sixty-six (45.2%) injuries had fractures that involved the medial articular surface. Nine with suboptimal CTs were excluded, leaving 57 injuries for review. Forty-two patients demonstrated coronal plane posteromedial fragments. Morphologic evaluation of the posteromedial fragment included articular surface area, maximum posterior cortical height (PCH), and sagittal fracture angle (SFA). RESULTS: Forty-two of 57 injuries (74%) demonstrated a posteromedial fragment that comprised a mean of 58% of the articular surface of the medial tibial plateau (range, 19%-98%) and a mean of 23% of the entire tibial plateau articular surface (range, 8%-47%). Mean posteromedial fragment height was 42 mm (range, 16-59 mm), and mean sagittal fracture angle was 81 degrees (range, 33 degrees to 112 degrees). Six patients demonstrated fracture patterns not accurately identified by the AO/OTA (Arbeitsgemeinschaft für Osteosynthesefragen/Orthopaedic Trauma Association) fracture classification system. CONCLUSIONS: A posteromedial fragment was observed in nearly one third of the bicondylar plateau fractures evaluated. The morphologic features of this fragment may have clinical implications when using currently available laterally applied fixed-angle screw/plate implants to stabilize these injuries. Alternate or supplementary fixation methods may be required when managing this injury pattern.     

Pathoanatomy and incidence of the posterolateral fractures in bicondylar tibial plateau fractures: a clinical computed tomography-based measurement and the associated biomechanical model simulation

Objectives

The aim of our study is to evaluate the incidence and pathoanatomy of posterolateral fragments and analyze the associated fracture mechanism in bicondylar tibial plateau fractures.

Methods

From 1.1.2008 to 3.15.2012, all patients suffering bicondylar tibial plateau fractures were identified, scanned and analyzed at the Shanghai Clinical Trauma Center. Furthermore cadaver knees were selected into three groups of 30/60/90 knee flexion to simulate the posterolateral tibial plateau fracture by an impact device.

Results

One hundred and sixty-four (44.32 %) bicondylar tibial plateau fractures finally satisfied our requirements. Fifty-three and ninety-four cases were measured eventually in the groups of posterolateral split and depression. The posterolateral articular fragment proportion was 15.43 %. The posterolateral articular fragment angle showed an average of 12.94°. The posterolateral fragment cortical height was on average 2.96 cm. The posterolateral sagittal fragment angle averaged at 72.06°. Ninety-four cases were measured in the posterolateral depression group. The average posterolateral articular depression proportion was 16.74 %. The average posterolateral articular depression height was 2.47 cm. In the biomechanical modeling of such kinds of fracture patterns, posterolateral split fractures in 30° and 60° flexion are significantly more than those in 90° flexion. Posterolateral splits combined with anterolateral depression fractures in 30° flexion are significantly more than those in 90° flexion.

Conclusion

The incidence of posterolateral fractures is 44.32 % in bicondylar tibial plateau fractures. The morphology of posterolateral area can be referenced for the surgeon in the future clinical work. The information is also helpful for the design of locking plate and fracture modeling in biomechanical test. In addition, that posterolateral split and posterolateral depression might be caused by different injury mechanisms. Different angles of knee flexion under the axial impact loading are possibly the interpretations for these two fracture patterns.     

Treatment of complicated tibial plateau fractures with dual plating via a 2-incision technique

The operative treatment of complicated bicondylar fractures of the tibial plateau remains a challenge to most surgeons. This retrospective study was designed to evaluate the clinical and radiological outcomes of dual plating via a 2-incision technique for the repair of complicated bicondylar tibial plateau fractures. A series of consecutive patients with bicondylar tibial plateau fractures treated by open reduction and internal fixation with a double buttress plate or a combination of locking plate and buttress plate via a 2-incision technique between March 2004 and March 2008 were retrospectively analyzed. Radiological and clinical results and complications of the 2 different fixation methods were compared. Seventy-nine patients matching the criteria of this study were followed up for at least 24 months. All of the fractures healed, with 3 cases of deep infection, 7 cases of secondary loss of reduction, 3 cases of secondary loss of alignment, and 10 cases of knee instability. At 24-month follow-up, mean Hospital for Special Surgery scores were 77.8±9.4 and 79.0±7.9 in the double buttress plate group and combination group, respectively. No significant differences in clinical or radiographic outcomes were found between the 2 groups, except that the combination group needed less bone graft. Dual plating with 2 incisions provided good exposition for the reduction and fixation of complicated bicondylar tibial plateau fractures. Using a combination of locking plate and buttress plate reduced the amount of bone graft compared with the double buttress plate technique.     

经腓骨头上入路手术治疗单纯后外侧胫骨平台骨折疗效观察

目的 探讨经腓骨头上入路手术治疗单纯后外侧胫骨平台骨折的安全性与有效性.方法 回顾性分析自2016-01-2019-10采用腓骨头上入路切开复位内固定治疗的34例单纯后外侧胫骨平台骨折.经腓骨头上入路的切口起自于Gerdy's结节,向上向后经过腓骨头上缘2 cm处作一个直切口.胫骨平台高度及关节面高度恢复后,取塑形好的...     

A biomechanical comparison between locked 3.5-mm plates and 4.5-mm plates for the treatment of simple bicondylar tibial plateau fractures: is bigger necessarily better?

Background

Evolution of periarticular implant technology has led to stiffer, more stable fixation constructs. However, as plate options increase, comparisons between different sized constructs have not been performed. The purpose of this study is to biomechanically assess any significant differences between 3.5- and 4.5-mm locked tibial plateau plates in a simple bicondylar fracture model.

Materials and methods

A total of 24 synthetic composite bone models (12 Schatzker V and 12 Schatzker VI) specimens were tested. In each group, six specimens were fixed with a 3.5-mm locked proximal tibia plate and six specimens were fixed with a 4.5-mm locking plate. Testing measures included axial ramp loading to 500 N, cyclic loading to 10,000 cycles and axial load to failure.

Results

In the Schatzker V comparison model, there were no significant differences in inferior displacement or plastic deformation after 10, 100, 1,000 and 10,000 cycles. In regards to axial load, the 4.5-mm plate exhibited a significantly higher load to failure (P = 0.05). In the Schatzker VI comparison model, there were significant differences in inferior displacement or elastic deformation after 10, 100, 1,000, and 10,000 cycles. In regards to axial load, the 4.5-mm plate again exhibited a higher load to failure, but this was not statistically significant (P = 0.21).

Conclusions

In the advent of technological advancement, periarticular locking plate technology has offered an invaluable option in treating bicondylar tibial plateau fractures. Comparing the biomechanical properties of 3.5- and 4.5-mm locking plates yielded no significant differences in cyclic loading, even in regards to elastic and plastic deformation. Not surprisingly, the 4.5-mm plate was more robust in axial load to failure, but only in the Schatzker V model. In our testing construct, overall, without significant differences, the smaller, lower-profile 3.5-mm plate seems to be a biomechanically sound option in the reconstruction of bicondylar plateau fractures.     

多轴锁定钢板治疗复杂胫骨平台骨折的初步疗效分析

目的 报告多轴锁定钢板治疗复杂胫骨平台骨折的方法及初步疗效. 方法 2006年7月至2007年6月,采用开放复位、多轴锁定钢板内固定治疗复杂胫骨平台骨折25例,闭合性骨折21例,开放性骨折4例;骨折按Schatzker分型:Ⅳ型6例,Ⅴ型16例,Ⅵ型3例;根据影像学测量结果及HSS评分标准进行临床效果评定.结果 所有患者术后获得7～15个月(平均10.5个月)随访,骨折4～6个月后骨折均获骨性愈合,术后6个月膝关节HSS评分78～96分,平均88.4分.发生皮瓣坏死1例,切口局部感染1例,无一例发生内固定松动、断裂或骨折复位丢失现象.术后1周、3个月及6个月的内翻角和后倾角比较差异无统计学意义(P>0.05). 结论胫骨平台多轴锁定钢板操作简便,锁定螺钉置入角度选择性高,内固定稳定性好,避免了原始及继发复位的丢失,是手术治疗复杂胫骨平台骨折安全、有效的内固定方法.     

Fracture pattern and fixation type related to loss of reduction in bicondylar tibial plateau fractures

IntroductionBicondylar tibial plateau fractures can be treated with locked plating applied from the lateral side with or without additional application of a medial plate (dual plating). Recent studies demonstrate that these injuries can be sub-grouped based upon their morphology by computed tomography (CT). The purpose of this study is to evaluate the relationship between fracture pattern, method of fixation and loss of reduction in bicondylar tibial plateau fractures.Patients and methodsPreoperative CT scans and postoperative plain films were evaluated on a consecutive series of bicondylar tibial plateau fractures. Fracture patterns were classified by CT. Angular alignment was measured immediately postoperatively and again at clinical and radiographic union to assess loss of reduction.ResultsA total of 140 patients were studied. Sixty-six (47%) had a single large medial fragment with the articular surface intact, 19 (14%) had a medial articular fracture line with a mainly sagittal component and 55 (39%) had a coronal fracture through the medial articular surface. A total of 129 patients had been treated with lateral locked plating alone whilst 11 patients (all with a coronal fracture of the medial condyle) underwent dual plating.There was little loss of reduction (median subsidence 0.5°) when lateral locked plating was employed alone in patients with a single medial fracture fragment or with a sagittal medial fracture line. When lateral locked plating was used in the presence of a medial coronal fracture line, there was a significantly higher rate of subsidence (median 2.0°) compared to those with no medial fracture line (p = 0.002). Patients with coronal fracture lines treated with dual plating had significantly less loss of reduction that those treated with lateral locked plating (p = 0.01).ConclusionsMost patients with bicondylar tibial plateau fractures do well when treated with lateral locked plating. However, those with a medial coronal fracture line tend to have a higher rate of subsidence and loss of reduction when lateral locked plating is employed alone. These fractures may be better treated with dual plating if the soft tissues allow.Level of evidenceLevel III (retrospective comparative study).     

A clinico-radiological study of bicondylar tibial plateau fractures managed with dual locking plates

BackgroundTreatment of bicondylar intra-articular tibial plateau fractures due to high energy trauma is complex and highly prone to complications due to fracture patterns and extensive soft tissue damage.AimThe study's objective was to evaluate the clinical, radiological and functional outcome, including the complications in closed Schatzker type V and VI tibial plateau fractures managed with dual locking plates using less extensile approaches and indirect reduction techniques.Materials and methodsThirty-four patients of closed Schatzker Type V and VI treated with pre-contoured locking plates were evaluated clinically and radiologically. Dual plating was done using a less extensile anterolateral approach for lateral plate and medial/open posteromedial approach for medial plate. Functional results were evaluated using the Knee Society Score (KSS) and radiological results by the Modified Rasmussen score (MRS) for radiological assessment.ResultsThe mean age of patients in our study was 45 years (range = 26–60 years) with a male predominance of 84.4%. The average time difference between trauma and surgery was 7.6 days (range = 5–14 days) with an average length of hospital stay of 8.5 days (range = 7–18 days). Autologous bone grafting from the iliac crest was done in 10 patients (29.4%) with a sizeable metaphyseal void. The study has a mean follow-up period of 22.6 months. The complete union was seen at an average of 17.4 weeks. The average knee ROM at the last follow-up was 110.75°. Three patients had complications, 2 with wound dehiscence and 1 with deep infection.ConclusionInternal fixation with dual locking plates is biomechanically strong and stable and gives excellent to good functional outcomes. However, the timing of internal fixation is essential in such complex injuries to prevent soft tissue complications and failure. The use of rigid fixation by less extensile approaches and indirect reduction techniques helps prevent wound healing problems and allows early knee mobilization.     

复杂过伸型胫骨平台骨折的形态特征及手术策略

目的:探讨复杂过伸型胫骨平台骨折的形态特征、手术策略及临床疗效。方法:回顾性分析2017年10月至2019年1月治疗27例复杂过伸型胫骨平台骨折患者资料,男19例,女8例;年龄23~68岁,平均43.4岁。根据胫骨平台骨折Schatzker分型：Ⅳ型8例,Ⅴ型5例,Ⅵ型14例;三柱理论分型：双柱骨折8例,三柱骨折19例...     

Analysis of the Ability of a Distal Tibial Anatomical Locking Plate to Capture the Distal Tibial Fragments in Patients with Pilon Fractures

Objective

Although pilon fractures are rare in clinical practice, they are difficult to treat because of their complexity. Effective fixation of the fracture fragment is the key to the treatment of pilon fractures. Plate osteosynthesis is common clinically, but there are many types of plates and the evaluation of the effect of fixation plates is not comprehensive. This study attempted to compare the capture effect of different fixation plates on the fracture fragments based on 3D modeling and fine distinctions of fracture fragments.

Methods

The computed tomography (CT) images before treatment of 127 patients with pilon fractures from January 2019 to December 2021 were retrospectively collected. The fracture lines were mapped and digitally displayed as 3D images using MIMICS 21 software. APLUS distal tibia anatomical locking plate (Plate A) and ZIMMER distal tibia anatomical plate (Plate B) were placed on a pseudo-bone model and CT scans were used to determine the number of screws in the major and minor fragments of pilon fractures. The frequency of the two plates capturing the fracture fragments was recorded.

Results

Under Assumption 1 or 2, Plate A performed significantly better than Plate B in capturing the major, Chaput, Volkmann, medial malleolus, and die-punch fracture fragments. Plate A captured markedly more minor fragments than Plate B under Assumption 2 but was not significantly different from Plate B under Assumption 1. Plate A or Plate B showed no obvious difference between major and minor capture rates under the same assumption, and A1 or B1 showed a markedly higher capture rate compared with A2 or B2. In addition, there was a significant positive correlation between the major capture rate and the major fragments in B1, and a significant negative correlation between the minor capture rate and the minor fragments in Plates A and B. However, there was no correlation between the major capture rate of Plate A and the major fragments.

Conclusion

The APLUS distal tibial anatomical locking plate is superior to the ZIMMER distal tibia anatomical plate in the ability to capture distal tibial fragments in pilon fracture cases.     

Ability of modern distal tibia plates to stabilize comminuted pilon fracture fragments: Is dual plate fixation necessary?

ObjectivesThe purpose of this study was to examine the screw trajectory of ten commercially available distal tibia plates and compare them to common fracture patterns seen in OTA C type pilon fractures to determine their ability to stabilize the three most common fracture fragments while buttressing anterolateral zones of comminution.HypothesisWe hypothesized that a single plate for the distal tibia would fail to adequately stabilize all three main fracture fragments and zones of comminution in complex pilon fractures.MethodsTen synthetic distal tibia sawbones models were used in conjunction with ten different locking distal tibia plate designs from three manufacturers (Depuy Synthes, J&J Co, Paoli, PA; Smith & Nephew, Memphis, TN; and Stryker, Mawa, NJ). Both medial and anterolateral plates from each company were utilized and separately applied to an individual sawbone model. Three implants allowing variable angle screw placement were used. The location of the locking screws and buttress effect 1 cm above the articular surface was noted for each implant using axial computed tomography (CT). The images were then compared to a recently published “pilon fracture map” using an overlay technique to establish the relationship between screw location and known common fracture lines and areas of comminution. Each of the three main fragments was considered “captured” by a screw if it was purchased by at least two screws thereby controlling rotational forces on each fragment.ResultsThree of four anterolateral plates lacked stable fixation in the medial fragment. Of the 4 anterolateral plates used, only the variable angle anterolateral plate by Depuy Synthes captured the medial fragment with two screws. All four anterolateral plates buttressed the area of highest comminution and had an average of 1.25 screws in the medial fragment and an average of 3 screws in the posterolateral fragment. All five direct medial plates had variable fixation within anterolateral and posterolateral fragments with an average of 1.8 screws in the anterolateral fragment and an average of 1.3 screws in the posterolateral fragment. The Depuy Synthes variable angle anterolateral plate allowed for fixation of the medial fragment with two screws while simultaneously buttressing the zone of highest comminution and capturing both the anterolateral and posterolateral fragments with five and three screws respectively. The variable angle anteromedial plate by Depuy Synthes captured all three main fracture fragments but it did not buttress the anterolateral zone of comminution.ConclusionIn OTA 43C type pilon fractures, 8 out of 10 studied commercially available implants precontoured for the distal tibia, do not adequately stabilize the three primary fracture fragments typically seen in these injuries. Anterolateral plates were superior in addressing the coronal primary fracture line across the apex of the plafond, and buttressing the zone of comminution. None of the available plates can substitute for an understanding of the fracture planes and fragments typically seen in complex intra-articular tibia fractures and the addition of a second plate is necessary for adequate stability.Level of evidenceLevel IV.     

Novel implant for peri-prosthetic proximal tibia fractures

BackgroundRepair of peri-prosthetic proximal tibia fractures is very challenging in patients with a total knee replacement or arthroplasty. The tibial component of the knee implant severely restricts the fixation points of the tibial implant to repair peri-prosthetic fractures. A novel implant has been designed with an extended flange over the anterior of tibial condyle to provide additional points of fixation, overcoming limitations of existing generic locking plates used for proximal tibia fractures. Furthermore, the screws fixed through the extended flange provide additional support to prevent the problem of subsidence of tibial component of knee implant.MethodsThe design methodology involved extraction of bone data from CT scans into a flexible CAD format, implant design and structural evaluation and optimisation using FEM as well as prototype development and manufacture by selective laser melting 3D printing technology with Ti6Al4 V powder.ResultsA prototype tibia implant was developed based on a patient-specific bone structure, which was regenerated from the CT images of patient’s tibia. The design is described in detail and being applied to fit up to 80% of patients, for both left and right sides based on the average dimensions and shape of the bone structure from a wide range of CT images.ConclusionA novel tibial implant has been developed to repair peri-prosthetic proximal tibia fractures which overcomes significant constraints from the tibial component of existing knee implant.     

The biomechanical cost of variable angle locking screws

IntroductionVariable angle (VA) locking plates in fracture fixation surgery allow screws to be fastened to the plate within a conical “locus of vectors” in order to avoid existing prostheses, joint surfaces, or poor quality bone. Clinical failures of VA constructs in which screws have rotated at the plate/screw interface have been reported raising the concern that there may be a biomechanical cost for the increased flexibility that VA provides. The objective of this study was to test the mechanical properties of one commonly used VA locking mechanism with screws placed in both nominal and off–axis trajectories and compare these against the standard locking mechanism.MethodsVA locking screws were inserted into plates for distal femur fractures (VA Curved Condylar) at various angles (0° to 15° away from perpendicular). A control group of standard locking screws/plates was also tested. Maximum moment at the screw/plate interface and moment at two reference displacements were determined.ResultsVA screws locked perpendicular to the plate provided the greatest maximum moment and moment at the reference displacements when using the VA system, and demonstrated lower moments compared to standard locking screws/plates (p < 0.001). Based on linear regression, there was an average decrease of approximately 0.4 Nm screw-plate interface strength for every 1° increase in screw-plate angle (p < 0.001). Decreases (p<0.05) were discovered in both maximum moment and moment at the reference displacements for screws locked at 5° relative to those locked at 0°, 10° relative to 0°, and 15° relative to 10°.DiscussionStandard locking systems provided greater resistance to rotational failure at the screw/plate interface than variable angle locking systems. Variable angle systems provided the greatest resistance to rotation when the screw was inserted perpendicular to the plate. As the off-axis angle increased, the resistance to rotation at the screw/plate interface decreased almost linearly. It is unknown if these differences are clinically significant in an actual fracture construct, but recent reported failures in the distal femur suggest that they might be.ConclusionSurgeons should weigh the risks and benefits of VA systems and attempt to minimize the off-axis angle magnitude when VA systems are selected.     

Biomechanical analysis of bicondylar tibial plateau fixation: how does lateral locking plate fixation compare to dual plate fixation?

OBJECTIVES: This study is designed to test the comparative strength of lateral-only locked plating to medial and lateral nonlocked plating in a cadaveric model of a bicondylar proximal tibial plateau fracture. METHODS: Ten matched pairs of human cadaveric proximal tibia specimens were used for biomechanical testing. Cyclic loading using a materials testing device simulated initial range of motion and load bearing following surgical repair. Subsidence of the medial and the lateral condyles was measured following 10,000 cycles from 100N to 1,000N; the maximum load to failure on the medial condyle for both plate constructs was also measured. RESULTS: On the lateral side, dual plating (DP) allowed an average of 0.68 +/- 0.14 mm of subsidence, compared with 1.03 +/- 0.27 mm for the fixed-angle plate (FAP) (P = 0.077). On the medial side, DP allowed an average of 0.78 +/- 0.15 mm of subsidence, compared with 1.51 +/- 0.32 mm for the FAP (P = 0.045). No significant difference was found in the maximal load to medial condyle fixation failure between either plating construct (P = 0.204). CONCLUSIONS: The results of this study demonstrate that dual-plate fixation allows less subsidence in this bicondylar tibial plateau cadaveric model when compared to isolated locked lateral plates. This may raise concerns about the widespread use of isolated lateral locked plate constructs in bicondylar tibial plateau fractures.