Effects of near cortical slotted holes in locking plate constructs

Newly designed plate for the treatment of posterolateral tibial plateau fractures: a finite element analysis

BACKGROUND

This study investigated the biomechanical properties of a new plate used for the treatment of posterolateral tibial plateau fractures using finite element analysis.

METHODS

The study groups were as follows: group PM, model of the new plate with posteromedial tibial plateau fracture; group PL, model of the new plate with posterolateral tibial plateau fracture; and group PC, model of the new plate with posterior tibial plateau fracture. We used two loading modes: uniform loading on the entire plateau, and loading on the posterior plateau. Data such as the displacement of the fracture and distribution of stress on the new plate and screws were recorded and analyzed.

RESULTS

When the whole plateau was loaded, the displacement of fractures in groups PM, PL, and PC were 0.273, 0.114, and 0.265 mm, respectively. The maximum stresses on the plates in groups PM, PL, and PC were 118.131 MPa, 44.191 MPa, and 115.433 MPa. The maximum stresses on the screws in Groups PM, PL, and PC were 166.731, 80.330, and 164.439 MPa, respectively. When the posterior tibial plateau was loaded, the displacement of the fractures in groups PM, PL, and PC was 0.410, 0.213, and 0.390 mm, respectively. The maximum stresses on the plates in groups PM, PL, and PC were 194.012 MPa, 72.806 MPa, and 185.535 MPa. The maximum stresses on the screws in Groups PM, PL, and PC were 278.265, 114.839, and 266.396 MPa, respectively.

CONCLUSION

The results of this study revealed that titanium plates have good fixation effects in all groups; therefore, the use of the new plate for posterolateral tibial plateau fractures appears to be safe and valid.

Influence of the Near-Cortical Over-Drilling Technique on the Mechanical Behaviour of Locking Plate Constructs Applied in Maned Wolf's Femur

OBJECTIVE

 The aim of this study was to evaluate the influence of near-cortical over-drilling holes on the mechanical behaviour of locking plate constructs applied in maned wolf's femur by using mechanical testing and finite element method (FEM).

STUDY DESIGN

 Seven pairs of adult maned wolves (Chrysocyon brachyurus) femur bones were randomly distributed into four groups. In all groups, a 3.5 mm locking compression plate, designed with 12 combi-holes and one locked, was applied to the lateral surface of the femur. G1 (n = 4) received bicortical locking screws placed in holes 1, 3, 5, 8, 10 and 12. In G2 (n = 5), the plate was applied as used in G1, but the application of the locked screws involved the near-cortical over-drilling technique. In G3 (n = 4), the plate was applied as used in G2, but the size of the near-cortical over-drilling was larger. The combi-holes 6 and 7 were maintained over a 10 mm fracture gap without screws. All constructs were tested for failure in the axial load. The axial load was applied eccentrically to the femoral head.

RESULTS

 Statistical differences were observed in the maximum load with G3 > G1 and G3 > G2, and in the deflection with G2 > G1 and G2 > G3. The FEM showed the lowest total displacement of the bone-plate constructs as well as of the plate in G1 compared with G2 and G3.

CONCLUSION

 The near-cortical over-drilling technique used in unstable fractures induced in the maned wolf's femur showed by static axial compression test that maximum load and deflection are dependent on drill hole size induced in the near-cortex. Based on FEM, the lowest total displacement of the bone-plate constructs was observed in Group 1.

Influence of therapeutic grip exercises induced loading rates in distal radius fracture healing with volar locking plate fixation

BACKGROUND AND OBJECTIVE

Therapeutic exercises could potentially enhance the healing of distal radius fractures (DRFs) treated with volar locking plate (VLP). However, the healing outcomes are highly dependant on the patient-specific fracture geometries (e.g., gap size) and the loading conditions at the fracture site (e.g., loading frequency) resulted from different types of therapeutic exercises. The purpose of this study is to investigate the effects of different loading frequencies induced by therapeutic exercises on the biomechanical microenvironment of the fracture site and the transport of cells and growth factors within the fracture callus, ultimately the healing outcomes. This is achieved through numerical modelling and mechanical testing.

METHODS

Five radius sawbones specimens (Pacific Research Laboratories, Vashon, USA) fixed with VLP (VRP2.0+, Austofix) were mechanically tested using dynamic test instrument (INSTRON E3000, Norwood, MA). The loading protocol used in mechanical testing involved a series of cyclic axial compression tests representing hand and finger therapeutic exercises. The relationship between the dynamic loading rate (i.e., loading frequency) and dynamic stiffness of the construct was established and used as inputs to a developed numerical model for studying the dynamic loading induced cells and growth factors in fracture site and biomechanical stimuli required for healing.

RESULTS

There is a strong positive linear relationship between the loading rate and axial stiffness of the construct fixed with VLP. The loading rates induced by the moderate frequencies (i.e., 1-2 Hz) could promote endochondral ossification, whereas relatively high loading frequencies (i.e., over 3 Hz) may hinder the healing outcomes or lead to non-union. In addition, a dynamic loading frequency of 2 Hz in combination of a fracture gap size of 3 mm could produce a better healing outcome by enhancing the transport of cells and growth factors at the fracture site in comparison to free diffusion (i.e. without loading), and thereby produces a biomechanical microenvironment which is favourable for healing.

CONCLUSION

The experimentally validated numerical model presented in this study could potentially contribute to the design of effective patient-specific therapeutic exercises for better healing outcomes. Importantly, the model results demonstrate that therapeutic grip exercises induced dynamic loading could produce a better biomechanical microenvironment for healing without compromising the mechanical stability of the overall volar locking plate fixation construct.

[Current status and progress of locking plate in the treatment of distal femoral comminuted fracture]

OBJECTIVE

To review the current status and progress of locking plate for the treatment of distal femoral comminuted fractures.

METHODS

The related literature was extensively reviewed to summarize the current status and progress in the treatment of distal femoral comminuted fracture with locking plate from four aspects: the current treatment situation, the shortcomings of locking plate and countermeasures, the progress of locking technology, locking plate and digital orthopedic technology.

RESULTS

Treatment of distal femoral comminuted fractures is challenging. Locking plates, the most commonly used fixation for distal femoral comminuted fractures, still face a high rate of treatment failure. Double plates can improve the mechanical stability of comminuted fractures, but specific quantitative criteria are still lacking for when to choose double plates for fixation. The far cortial locking screw has shown good application value in improving the micro-movement and promoting the growth of callus. The biphasic plating is a development of the traditional locking plate, but needs further clinical examination. As an auxiliary means, digital orthopedic technology shows a good application prospect.

CONCLUSION

The inherent defect of locking plate is a factor that affects the prognosis of distal femoral comminuted fracture. The optimization of locking technology combined with digital orthopedic technology is expected to reduce the failure rate of treatment of distal femoral comminuted fracture.

Biomechanics of Osteoporotic Fracture Care: Advances in Locking Plate and Intramedullary Nail Technology

Osteoporotic fractures are extremely common and will continue to increase. Methods of internal fixation must address challenges presented by architectural changes of weakened bone. The goals of surgery are to provide mechanically stable internal fixation with minimal biologic insult that provides rapid rehabilitation and early mobilization. Novel techniques and technology that reinforce preservation of periosteal blood supply and utilization of biomechanically stable constructs diminish failure rates. Advents in locking plate technology, intramedullary nail designs, bone augmentation, and multiple implant constructs maximize strength while mitigating axial, torsional, and bending failure modes to provide optimal patient outcomes.

[Research on the nature of micromovement and the biomechanical staging of fracture healing]

Objective

To explore the nature of micromovement and the biomechanical staging of fracture healing.

Methods

Through literature review and theoretical analysis, the difference in micromovement research was taken as the breakthrough point to try to provide a new understanding of the role of micromovement and the mechanical working mode in the process of fracture healing.

Results

The process of fracture healing is the process of callus generation and connection. The micromovement is the key to start the growth of callus, and the total amount of callus should be matched with the size of the fracture space. The strain at the fracture end is the key to determine the callus connection. The strain that can be tolerated by different tissues in the fracture healing process will limit the micromovement. According to this, the fracture healing process can be divided into the initiation period, perfusion period, contradiction period, connection period, and physiological period, i.e., the biomechanical staging of fracture healing.

Conclusion

Biomechanical staging of fracture healing incorporates important mechanical parameters affecting fracture healing and introduces the concepts of time and space, which helps to understand the role of biomechanics, and its significance needs further clinical test and exploration.

The Clinical and Radiological Evaluation of Far Cortex Locking Plate in Distal Femur Fractures

Introduction Locking plates in distal femur fractures were associated with a high rate of non-union and hardware failure. To overcome these drawbacks far cortex locking (FCL) concept was introduced. It is a novel bridge plating strategy to enhance interfragmentary motion for the promotion of secondary bone healing while retaining sufficient construct strength. The present study evaluated the effects of diaphyseal FCL fixation on fracture healing for periarticular locking plates used for fixation of distal femur fractures.  Materials and methods Our cohort was of 11 consecutive patients who presented to emergency after distal femur fracture and underwent surgery with the FCL plate between January 2015 and January 2016. Clinical (KOOS) and radiological evaluation of all patients was done to look for knee scores and union. Also, other complications like infection, non-union, painful hardware, implant failure were recorded  Results No non-union or hardware failure was observed in our cohort of 11 patients. Early callus formation was seen and partial weight-bearing was started at an average of 6 weeks (5-8 weeks). Average time to clinical healing was 10 weeks (8-13 weeks) whereas radiographic union was seen at 16 weeks (14-17 weeks). One patient with an open fracture had superficial surgical wound infection which healed uneventfully after one debridement and with IV antibiotics. The average knee injury and osteoarthritis outcome score (KOOS) at final follow-up was 91 (87-95) in our cohort. Conclusion FCL is an effective method to reduce construct stiffness, promote early callus formation, decrease non-union rate and achieve biological healing while retaining sufficient strength to prevent hardware failure.

Mechanical Effects of Bone Substitute and Far-Cortical Locking Techniques in 2-Part Proximal Humerus Fracture Reconstruction: A Cadaveric Study

OBJECTIVES

To make direct comparisons of the biomechanical properties of a control (CTL) group and implants that were augmented with far cortical locking (FCL), bone substitute material (BSM), and a combination of both (ALL) to determine which fixation is most effective in reducing implant failure.

METHODS

The constructs were tested with osteopenic cadaveric specimens in a two-part fracture model. Specimens were subjected to a battery of nondestructive torsion and axial compression tests, followed by a cyclic test. Construct stiffness and cycles to failure were documented, pre- and post-test fluoroscopy was performed, and implant and bone kinematics were quantified.

RESULTS

During nondestructive testing, the BSM group exhibited significantly increased torsional and axial stiffness compared with the FCL (P = 0.006, P < 0.001) group and ALL group (P < 0.001, P = 0.006). There were no significant differences in resistance to cyclic loading between groups. Fluoroscopic analysis indicated significant differences in the motions of nonlocked cannulated screws (used in BSM and ALL) versus locked screws (used in CTL and FCL).

CONCLUSIONS

Patients with poor bone quality and proximal humerus fracture may necessitate added compliance or rigidity to achieve fixation. Both have exhibited favorable biomechanical characteristics in this cadaveric 2-part proximal humerus fracture model.

[Flexible internal fixation with locking plate for distal femoral fractures]

Objective

To analyze the effectiveness of flexible internal fixation with locking plate for distal femoral fractures.

Methods

Between January 2015 and June 2016, 21 cases of distal femoral fractures were treated. There were 5 males and 16 females with an average age of 62 years (range, 32-88 years). Injury was caused by falling in 14 cases, by traffic accident in 5 cases, and by falling from height in 2 cases. The fractures located at the left side in 13 cases and the right side in 8 cases. Twenty cases were fresh closed fractures and 1 case was open fracture. According to AO/Association for the Study of Internal Fixation (AO/OTA) typing, there were 5 cases of type 33-A1, 3 of type 33-A2, 8 of type 33-A3, 2 of type 33-C2, and 3 of type 33-C3. The time from injury to operation was 3-13 days (mean, 6.5 days).

Results

All operation incisions healed primarily. Eighteen patients were followed up 12-24 months (mean, 16 months). All fractures healed, and the healing time was 8-24 weeks (mean, 16.6 weeks). The articular surface was smooth and the thigh length was recovered. No screw loosening, plate breakage, valgus or varus of the knee, stiff of the knee or non-unions occurred during follow-up. There was no significant difference in visual analogue scale (VAS) score between at 6 and 12 months after operation ( P>0.05), and the difference was significant bewteen the other time points ( P<0.05). There were significant differences in the range of motion of knee between 1 month and 3, 6, 12 months ( P<0.05); there was no significant difference between 3, 6, and 12 months ( P>0.05). There were significant differences in the Neer scores between 1, 3, 6, and 12 months after operation ( P<0.05). According to Neer score criteria, the results were excellent in 12 cases and good in 6 cases at 12 months after operation.

Conclusion

Flexible internal fixation with locking plate for distal femoral fractures can get good functional recovery.

Surgical treatment of osteoporotic fractures: An update on the principles of management

The treatment of osteoporotic fractures continues to challenge orthopedic surgeon. The fragility of the underlying bone in conjunction with the need for specific implants led to the development of explicit surgical techniques in order to minimize implant failure related complications, morbidity and mortality. From the patient's perspective, the existence of frailty, dementia and other medical related co-morbidities induce a complex situation necessitating high vigilance during the perioperative and post-operative period. This update reviews current principles and techniques essential to successful surgical treatment of these injuries.

Dynamic locked plating for fixation of distal femur fractures using near- cortical over-drilling: Preliminary results of a prospective observational study

INTRODUCTION

Nonunion after locked plating of distal femur fractures is not uncommon. Authors wanted to assess if "Dynamic" locked plating using near-cortex over-Drilling technique would provide a mechanical environment the promotes callus formation, thereby avoiding non-union encountered when applying locked plates with the conventional method.

METHODS

This study was conducted at an academic Level 1 Trauma Center. This is a prospective study conducted from November 2015 to November 2016. Follow-up was 10 months on average (ranging from 8 to 12 months). The study included 20 patients with 20 fractures (13 males, 7 females). The average patients' age was 41.2 years (18-64 years). According to the Müller AO classification of distal femur fractures (33A-C) there were 15 cases with extra-articular fractures (AO 33A), 5 patients with intra-articular fractures (AO 33C). Dynamic Locked plating using near-cortical over-drilling technique was done for all patients. Two blinded observers assessed callus score on 6-week radiographs using a 4-point ordinal scale. A 2-tailed t-test. Two-way mixed intra-class correlation testing was performed to determine reliability of the callus measurements by the 2 observers.

RESULTS

All patients achieved union, time to union was 13.4 weeks on average (range form 8-24 weeks). Delayed union was observed in 2 patients. The average callus score for fractures was 1.8 (SD 0.6). All fractures united in alignment except 1 fracture which united in valgus malalignment, the deformity was appreciated in the postoperative radiographs. No wound related complications, no loss of reduction, no catastrophic implant failure or screw breakage were detected.

CONCLUSION

Dynamic locked plating using near-cortex over-drilling is a simple technique that uses standard locked plates that promotes callus formation when used for fixing distal femur fractures.

Stress Modulation of Fracture Fixation Implants

Stress modulation is the concept of manipulating bridge plate variables to provide a flexible fixation construct that allows callus formation through uneventful secondary bone healing. Obtaining absolute stability through the anatomic reduction of all fracture fragments comes at the expense of fracture biology, whereas intramedullary nailing, which is more advantageous for diaphyseal fractures of the lower extremity, is technically demanding and often may not be possible when stabilizing many metaphyseal fractures. Overly stiff plating constructs are associated with asymmetric callus formation, early implant failure, and fracture nonunion. Numerous surgeon-controlled variables can be manipulated to increase flexibility without sacrificing strength, including using longer plates with well-spaced screws, choosing titanium or stainless steel implants, and using locking or nonlocking screws. Axially dynamic emerging concepts, such as far cortical locking and near cortical overdrilling, provide further treatment options when bridge plating techniques are used.

Mechanical Construct Characteristics Predisposing to Non-union After Locked Lateral Plating of Distal Femur Fractures

OBJECTIVES

To identify discrete construct characteristics related to overall construct rigidity that may be independent predictors of nonunion after lateral locked plate (LLP) fixation of distal femur fractures.

DESIGN

Retrospective case-control study.

SETTING

Three level-1 urban trauma centers.

PATIENTS/PARTICIPANTS

Two hundred and seventy-one supracondylar femoral fractures treated with LLP at 3 affiliated level 1 urban trauma centers between August 2004 and December 2010.

METHODS

Nonunion was defined as a secondary procedure for poor healing. Construct variables included: (1) combined plate design and material variable, (2) Plate length, (3) # screws proximal to fracture, (4) total screw density (TSD), (5) proximal screw density (PSD), (6) presence of a screw crossing the main fracture, and (7) rigidity score multivariable analysis was performed using logistic regression to identify independent risk factors for nonunion.

INTERVENTION

LLP fixation.

MAIN OUTCOME MEASURE

Nonunion.

RESULTS

Nonunion rate was 13.3% (n = 36). There was a significant association between plate design/material and nonunion with 41% of stainless constructs and 10% of titanium constructs resulting in a nonunion (P < 0.001). Rigidity scores reached significance (P = 0.001) with constructs resulting in a nonunion having higher scores. No significant univariate differences with respect to number of proximal screws, plate length, total screw density, or proximal screw density were observed between healed fractures and those with nonunion. Results of the multivariate analysis confirmed that the primary significant independent predictor of nonunion was plate design/material (odds ratio, 6.8; 95% CI, 2.9-16.1; P < 0.001).

CONCLUSIONS

When treating distal femur fractures with LLP, combined plate design and material variable has a highly significant influence on the risk of nonunion independent of any other construct variable.

LEVEL OF EVIDENCE

Prognostic Level III. See Instructions for Authors for a complete description of levels of evidence.

Dynamic Locked Plating of Distal Femur Fractures

OBJECTIVES

Nonunion after locked bridge plating of comminuted distal femur fractures is not uncommon. "Dynamic" locked plating may create an improved mechanical environment, thereby achieving higher union rates than standard locked plating constructs.

SETTING

Academic Level 1 Trauma Center.

PATIENTS/PARTICIPANTS

Twenty-eight patients with comminuted supracondylar femur fractures treated with either dynamic or standard locked plating.

INTERVENTION

Dynamic plating was achieved using an overdrilling technique of the near cortex to allow for a 0.5-mm "halo" around the screw shaft at the near cortex. Standard locked plating was done based on manufacturer's suggested technique. The patients treated with dynamic plating were matched 1:1 with those treated with standard locked plating based on OTA classification and working length.

MAIN OUTCOME MEASUREMENTS

Three blinded observers made callus measurements on 6-week radiographs using a 4-point ordinal scale. The results were analyzed using a 2-tailed t test and 2-way intraclass correlations.

RESULTS

The dynamic plating group had significantly greater callus (2.0; SD, 0.7) compared with the control group (1.3: SD, 0.8, P = 0.048) with substantial agreement amongst observers in both consistency (0.724) and absolute score (0.734). With dynamic plating group, 1 patient failed to unite, versus three in the control group (P = 0.59). The dynamic group had a mean change in coronal plane alignment of 0.5 degrees (SD, 2.6) compared with 0.6 (SD, 3.0) for the control group (P = 0.9) without fixation failure in either group.

CONCLUSIONS

Overdrilling the near cortex in metaphyseal bridge plating can be adapted to standard implants to create a dynamic construct and increase axial motion. This technique seems to be safe and leads to increased callus formation, which may decrease nonunion rates seen with standard locked plating.

LEVEL OF EVIDENCE

Therapeutic Level III. See Instructions for Authors for a complete description of levels of evidence.

Computational Simulation of Mechanical Microenvironment of Early Stage of Bone Healing under Locking Compression Plate with Dynamic Locking Screws

It is well known that bone healing outcomes highly depend on the mechanical microenvironment of the fracture site, and a certain degree of interfragmentary movement (IFM) is essential for indirect (i.e. natural) bone healing. The application of locking compression plate (LCP) internal fixation in the treatment of bone fracture is a common practice which leads to early mobility and full function of the fractured extremity. However should the fixation configuration be too stiff, it might result in delayed healing or asymmetric tissue development across the fracture site due to the fact that IFM in near cortex area is too small to promote healing. Dynamic locking screw (DLS) has been recently designed to tackle this problem by reducing the stiffness of LCP fixation. However, the actual mechano-regulation mechanisms in which DLS uses to regulate the healing process are still not fully understood. The objective of this paper is to develop a computational model to understand the change of mechanical microenvironment of fracture site under LCP with dynamic locking screw in comparison to standard locking screw, and how this change could potentially regulate tissue development within the fracture callus during the healing process.Keywords: bone healing, locking compression plate, dynamic locking screw, finite element modelling

Biomechanical considerations for surgical stabilization of osteoporotic fractures

The incidence of osteoporotic fractures has been steadily rising along with the aging of the population. Surgical management of these fractures can be a challenge to orthopedic surgeons. Diminished bone mass and frequent comminution make fixation difficult. Advancements in implant design and fixation techniques have served to address these challenges and when properly applied, can improve overall outcome. The purpose of this review is to describe fixation challenges of common osteoporotic fractures and provide options for successful treatment.

Retrograde nailing versus locked plating of extra-articular distal femoral fractures: comparison of 36 cases

OBJECTIVE

The purpose of this study was to retrospectively evaluate the use of locked plating (LP) and retrograde nailing (RN) for treating extra-articular distal femoral fractures.

MATERIALS AND METHODS

From January 2004 to March 2009, 36 patients with extra-articular distal femoral fractures were surgically treated at our Trauma Center. The patients were divided into two groups according to the treatment method, with 19 patients being treated by LP (LP group) and 17 patients via RN (RN group).

RESULTS

The demographics of age (p = 0.460) and gender (p = 0.481) in both LP and RN groups were similar. No differences were found with respect to postoperative malreduction, deep infection, hardware failure, operating time, knee pain, HSS score and range of knee movement. The mean intraoperative blood loss was significantly higher in the RN group (298 ± 65.2 ml, range 200-410) than in the LP group (200 ± 48.9 ml, range 130-300) (p < 0.01). However, a higher rate of union disturbance was observed in the LP group (36.8%) compared to the RN group (5.9%) (p = 0.044).

CONCLUSIONS

The overall union disturbance rate in the LP group was higher than in the RN group. However, further analysis revealed that clinical outcome may largely depend on surgical technique rather than on the choice of implant. Therefore, correct rules (the same for every procedure) should be strictly adhered to, especially in the application of LP.

A distal femoral supra-condylar plate: biomechanical comparison with condylar plate and first clinical application for treatment of supracondylar fracture

PURPOSE

An anatomical supra-condylar plate is designed and analysed by biomechanical testing.

METHODS

The biomechanical properties of the supra-condylar and condylar plate were compared in six matched pairs of cadaveric femurs. A transverse osteotomy gap was created to simulate an OTA/AO type A3 supracondylar fracture. The left and right specimens were fitted with supra-condylar and condylar plate, respectively. Nondestructive axial compression, three-point bending and torsion tests were performed, and the peak load of the bone-implant construction was measured. The fracture site suitable for supra-condylar plate application and its correlation with femoral length were calculated. The gender influence on it was also discussed.

RESULTS

The difference of stiffness between the supra-condylar and condyle groups were not significant (P > 0.05) at 363.4 and 362.5 N/mm for compression, 229.5 and 237.6 N/mm in the sagittal plane and 195.5 and 188.4 N/mm in the coronal plane for three-point bending, and 7.5 and 7.9 Nm/deg for axial torsion, respectively. The peak load was 4438 ± 136.15 N and 5215 ± 174.33 N, respectively, for the two groups. The average extent of the fracture site suitable for the application of the supra-condylar plate was 70.86 ± 4.61 mm. The femoral length and gender showed no influence on it.

CONCLUSION

Despite the limited bone contact area provided by the supra-condylar plate, its construct stiffness is comparable to the condylar plate. The supra-condylar plate can be used to treat carefully-selected extra-articular supracondylar fractures.