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Liu S, Lu L, Chen T, Liu Y, Wei D, Miao J, Yu D, Fu X. In vivo axial load-share ratio measurement using a novel hexapod system for safe external fixator removal. BMC Musculoskelet Disord 2024; 25:353. [PMID: 38724941 PMCID: PMC11080187 DOI: 10.1186/s12891-024-07440-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 02/12/2024] [Accepted: 04/12/2024] [Indexed: 05/13/2024] Open
Abstract
BACKGROUND External fixation is widely used in the treatment of traumatic fractures; however, orthopedic surgeons encounter challenges in deciding the optimal time for fixator removal. The axial load-share ratio (LS) of the fixator is a quantitative index to evaluate the stiffness of callus healing. This paper introduces an innovative method for measuring the LS and assesses the method's feasibility and efficacy. Based on a novel hexapod LS-measurement system, the proposed method is to improve the convenience and precision of measuring LS in vivo, hence facilitating the safe removal of external fixators. METHODS A novel hexapod system is introduced, including its composition, theoretical model, and method for LS measurement. We conducted a retrospective study on 82 patients with tibial fractures treated by the Taylor Spatial Frame in our hospital from September 2018 to June 2020, of which 35 took LS measurements with our novel method (Group I), and 47 were with the traditional method (Group II). The external fixator was removed when the measurement outcome (LS < 10%) was consistent with the surgeon's diagnosis based on the clinical and radiological assessment (bone union achieved). RESULTS No significant difference was found in the fracture healing time (mean 25.3 weeks vs. 24.9 weeks, P > 0.05), frame-wearing duration (mean 25.5 weeks vs. 25.8 weeks, P > 0.05), or LS measurement frequency (mean 1.1 times vs. 1.2 times, P > 0.05). The measurement system installation time in Group I was significantly shorter compared to Group II (mean 14.8 min vs. 81.3 min, P < 0.001). The LS value of the first measurement in Group I was lower than that of Group II (mean 5.1% vs. 6.9%, P = 0.011). In Group I, the refracture rate was 0, but in Group II it was 4.3% (2/47, P > 0.05). CONCLUSION The novel hexapod LS-measurement system and involved method demonstrated enhanced convenience and precision in measuring the LS of the external fixator in vivo. The LS measurement indicates the callus stiffness of fracture healing, and is applicable to evaluate the safety of removing the fixator. Consequently, it is highly recommended for widespread adoption in clinical practice.
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Affiliation(s)
- Sida Liu
- School of Mechanical Engineering, Tianjin University, Tianjin, China
- Department of Radiotherapy, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China
- Department of Orthopedics, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China
| | - Lin Lu
- School of Mechanical Engineering, Tianjin University, Tianjin, China
- Department of Radiotherapy, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China
- Department of Orthopedics, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China
| | - Tao Chen
- School of Mechanical Engineering, Tianjin University, Tianjin, China
- Department of Radiotherapy, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China
- Department of Orthopedics, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China
| | - Yanshi Liu
- Department of Orthopedics, The Affiliated Hospital of Southwest Medical University, Luzhou, Sichuan, China
| | - Dong Wei
- Department of Orthopedics Surgery, Tianjin Academy Traditional Chinese Medicine Affiliated Hospital, Tianjin, China
| | - Jun Miao
- Department of Spine Surgery, Tianjin Hospital, Tianjin, China.
| | - Defu Yu
- Department of Orthopedics, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China.
| | - Xuefei Fu
- Department of Orthopedics, Anhui No.2 Provincial People's Hospital, Hefei, Anhui, China.
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Gilli A, Ghirardelli S, Pozzi P, Touloupakis G, Messori M, Theodorakis E, Antonini G. Do working length and proximal screw density influence the velocity of callus formation in distal tibia fractures treated with a medial bridge plate? EUROPEAN JOURNAL OF ORTHOPAEDIC SURGERY & TRAUMATOLOGY : ORTHOPEDIE TRAUMATOLOGIE 2024; 34:523-528. [PMID: 37644334 PMCID: PMC10771589 DOI: 10.1007/s00590-023-03697-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/02/2023] [Accepted: 08/17/2023] [Indexed: 08/31/2023]
Abstract
INTRODUCTION Aim of our study was to evaluate the influence of working length and screw density on callus formation in distal tibial fractures fixed with a medial bridge plate. MATERIALS AND METHODS 42 distal tibia fractures treated with a bridge plate were analyzed. Minimum follow-up was 12 months. mRUST score (modified Radiographic Union Scale for Tibial fractures) was used to assess callus formation. Working length and screw density were measured from post-operative radiographs. RESULTS 39 (92.9%) fractures healed uneventfully. 32 (76.19%) patients showed signs of early callus formation 3 months post-surgery. In these patients a lower screw density was used compared to patients who didn't show early callus (33.4 vs. 26.6; p = 0.04). No differences was noticed in working length. CONCLUSION Bridge plate osteosynthesis is a good treatment option in distal tibia fractures. In our series increasing the working length was not associated with a faster callus formation in distal tibia fractures. Conversely, a lower screw density proximally to the fracture site was associated to a faster callus growth.
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Affiliation(s)
- Antonio Gilli
- Department of Orthopedic and Traumatology, San Carlo Borromeo Hospital, Milan, Italy.
- University of Milan, Milan, Italy.
| | - Stefano Ghirardelli
- Women's College Hospital, Orthopaedic Sports Medicine, University of Toronto, Toronto, Canada
| | - Pierrenzo Pozzi
- Department of Orthopedic and Traumatology, San Carlo Borromeo Hospital, Milan, Italy
| | - Georgios Touloupakis
- Department of Orthopedic and Traumatology, San Carlo Borromeo Hospital, Milan, Italy
| | - Matteo Messori
- Department of Orthopedic and Traumatology, San Carlo Borromeo Hospital, Milan, Italy
| | - Emmanouil Theodorakis
- Department of Orthopedic and Traumatology, San Carlo Borromeo Hospital, Milan, Italy
| | - Guido Antonini
- Department of Orthopedic and Traumatology, San Carlo Borromeo Hospital, Milan, Italy
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Roytman GR, Beitler B, LaMonica J, Spero M, Toy K, Ramji AF, Yoo B, Leslie MP, Baumgaertner M, Tommasini SM, Wiznia DH. An analytical model of lateral condylar plate working length. Clin Biomech (Bristol, Avon) 2023; 110:106129. [PMID: 37871506 PMCID: PMC10848195 DOI: 10.1016/j.clinbiomech.2023.106129] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 07/18/2023] [Revised: 10/10/2023] [Accepted: 10/17/2023] [Indexed: 10/25/2023]
Abstract
BACKGROUND The locking plate is a common device to treat distal femur fractures. Healing is affected by construct stiffness, thus many surgeon-controlled variables such as working length have been examined for their effects on strain at the fracture. No convenient analytical model which aids surgeons in determining working length has yet been described. We propose an analytical model and compare it to finite element analysis and cadaveric biomechanical testing. METHODS First, an analytical model based on a cantilever beam equation was derived. Next, a finite element model was developed based on a CT scan of a "fresh-frozen" cadaveric femur. Third, biomechanical testing in single-leg stance loading was performed on the cadaver. In all methods, strain at the fracture was recorded. An ANCOVA test was conducted to compare the strains. FINDINGS In all models, as the working length increased so did strain. For strain at the fracture, the shortest working length (35 mm) had a strain of 8% in the analytical model, 9% in the finite element model, and 7% for the cadaver. The longest working length (140 mm) demonstrated strain of 15% in the analytical model, and the finite element and biomechanical tests both demonstrated strain of 14%. INTERPRETATION The strain predicted by the analytical model was consistent with the strain observed in both the finite element and biomechanical models. As demonstrated in existing literature, increasing the working length increases strain at the fracture site. Additional work is required to refine and establish validity and reliability of the analytical model.
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Affiliation(s)
- Gregory R Roytman
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA; Biomedical Engineering, Yale University School of Engineering & Applied Science, 17 Hillhouse Avenue, New Haven, CT 06520, USA.
| | - Brian Beitler
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Julia LaMonica
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Matthew Spero
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Kendal Toy
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Alim F Ramji
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Brad Yoo
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Michael P Leslie
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Michael Baumgaertner
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA
| | - Steven M Tommasini
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA; Biomedical Engineering, Yale University School of Engineering & Applied Science, 17 Hillhouse Avenue, New Haven, CT 06520, USA
| | - Daniel H Wiznia
- Orthopaedics and Rehabilitation, Yale University School of Medicine, 47 College Place, New Haven, CT 06510, USA; Mechanical Engineering & Materials Science, Yale University School of Engineering & Applied Science, 17 Hillhouse Avenue, New Haven, CT 06520, USA
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Zdero R, Gide K, Brzozowski P, Schemitsch EH, Bagheri ZS. Biomechanical design optimization of distal femur locked plates: A review. Proc Inst Mech Eng H 2023; 237:791-805. [PMID: 37366552 DOI: 10.1177/09544119231181487] [Citation(s) in RCA: 1] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 06/28/2023]
Abstract
Clinical findings, manufacturer instructions, and surgeon's preferences often dictate the implantation of distal femur locked plates (DFLPs), but healing problems and implant failures still persist. Also, most biomechanical researchers compare a particular DFLP configuration to implants like plates and nails. However, this begs the question: Is this specific DFLP configuration biomechanically optimal to encourage early callus formation, reduce bone and implant failure, and minimize bone "stress shielding"? Consequently, it is crucial to optimize, or characterize, the biomechanical performance (stiffness, strength, fracture micro-motion, bone stress, plate stress) of DFLPs influenced by plate variables (geometry, position, material) and screw variables (distribution, size, number, angle, material). Thus, this article reviews 20 years of biomechanical design optimization studies on DFLPs. As such, Google Scholar and PubMed websites were searched for articles in English published since 2000 using the terms "distal femur plates" or "supracondylar femur plates" plus "biomechanics/biomechanical" and "locked/locking," followed by searching article reference lists. Key numerical outcomes and common trends were identified, such as: (a) plate cross-sectional area moment of inertia can be enlarged to lower plate stress at the fracture; (b) plate material has a larger influence on plate stress than plate thickness, buttress screws, and inserts for empty plate holes; (c) screw distribution has a major influence on fracture micro-motion, etc. Recommendations for future work and clinical implications are then provided, such as: (a) simultaneously optimizing fracture micro-motion for early healing, reducing bone and implant stresses to prevent re-injury, lowering "stress shielding" to avoid bone resorption, and ensuring adequate fatigue life; (b) examining alternate non-metallic materials for plates and screws; (c) assessing the influence of condylar screw number, distribution, and angulation, etc. This information can benefit biomedical engineers in designing or evaluating DFLPs, as well as orthopedic surgeons in choosing the best DFLPs for their patients.
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Affiliation(s)
- Radovan Zdero
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
| | - Kunal Gide
- Department of Mechanical Engineering, George Mason University, Fairfax, VA, USA
| | - Pawel Brzozowski
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Victoria Hospital, London, ON, Canada
- Division of Orthopaedic Surgery, Western University, London, ON, Canada
| | - Z Shaghayegh Bagheri
- Department of Mechanical Engineering, George Mason University, Fairfax, VA, USA
- Kite Research Institute, Toronto Rehab Institute, University Health Network, Toronto, ON, Canada
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Bowers KM, Wright EM, Terrones LD, Sun X, Rifkin R, Grzeskowiak R, Croy E, Seddighi R, Kleine S, Hampton C, Hecht S, Adair HS, Anderson DE, Mulon PY. In vitro analysis and in vivo assessment of fracture complications associated with use of locking plate constructs for stabilization of caprine tibial segmental defects. J Exp Orthop 2023; 10:38. [PMID: 37010659 PMCID: PMC10070588 DOI: 10.1186/s40634-023-00598-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Accepted: 03/15/2023] [Indexed: 04/04/2023] Open
Abstract
PURPOSE Locking plate fixation of caprine tibial segmental defects is widely utilized for translational modeling of human osteopathology, and it is a useful research model in tissue engineering and orthopedic biomaterials research due to its inherent stability while maintaining unobstructed visualization of the gap defect and associated healing. However, research regarding surgical technique and long-term complications associated with this fixation method are lacking. The goal of this study was to assess the effects of surgeon-selected factors including locking plate length, plate positioning, and relative extent of tibial coverage on fixation failure, in the form of postoperative fracture. METHODS In vitro, the effect of plate length was evaluated using single cycle compressive load to failure mechanical testing of locking plate fixations of caprine tibial gap defects. In vivo, effects of plate length, positioning, and relative tibial coverage were evaluated using data from a population of goats enrolled in ongoing orthopedic research which utilized locking plate fixation of 2 cm tibial diaphyseal segmental defects to evaluate bone healing over 3, 6, 9, and 12 months. RESULTS In vitro, no significant differences in maximum compressive load or total strain were noted between fixations using 14 cm locking plates and 18 cm locking plates. In vivo, both plate length and tibial coverage ratio were significantly associated with postoperative fixation failure. The incidence of any cortical fracture in goats stabilized with a 14 cm plate was 57%, as compared with 3% in goats stabilized with an 18 cm plate. Craniocaudal and mediolateral angular positioning variables were not significantly associated with fixation failure. Decreasing distance between the gap defect and the proximal screw of the distal bone segment was associated with increased incidence of fracture, suggesting an effect on proximodistal positioning on overall fixation stability. CONCLUSIONS This study emphasizes the differences between in vitro modeling and in vivo application of surgical fixation methods, and, based on the in vivo results, maximization of plate-to-tibia coverage is recommended when using locking plate fixation of the goat tibial segmental defect as a model in orthopedic research.
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Affiliation(s)
- Kristin M Bowers
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA.
| | - Ellis M Wright
- Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Lori D Terrones
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Xiaocun Sun
- Office of Information Technology, University of Tennessee, Knoxville, USA
| | - Rebecca Rifkin
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Remi Grzeskowiak
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Elizabeth Croy
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Reza Seddighi
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Stephanie Kleine
- Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Chiara Hampton
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Silke Hecht
- Small Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Henry S Adair
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - David E Anderson
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
| | - Pierre-Yves Mulon
- Large Animal Clinical Sciences, College of Veterinary Medicine, University of Tennessee, Knoxville, USA
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Wang Y, Zou Q, Wang Z, Wang W, Shen H, Lu H. Micromotion-based balanced drilling technology to increase near cortical strain. BMC Surg 2022; 22:387. [DOI: 10.1186/s12893-022-01816-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2021] [Accepted: 10/11/2022] [Indexed: 11/13/2022] Open
Abstract
Abstract
Objective
A micromotion-based balanced drilling system was designed based on a locking plate (LP) and far cortical locking (FCL) concept to maintain the balance of micromotions of the cortex on both sides of a fracture region. The system was tested by axial compression test.
Methods
The fracture gap was set to 2 cm, and locking screws with a diameter of 5 mm and a locking plate were used to fix it. The diameters of the two sections of the stepping drill were 3.5 mm and 5.0 mm, respectively. One of the matching drilling sleeves was a standard sleeve (eccentricity, 0 mm) and the other was an eccentric sleeve (proximal eccentricity, 1 mm). A model of the fixed locking plate (AO/ASIF 33-A3) for distal femoral fractures with a gap of 2 cm was established based on data from 42 artificial femurs (SAWBONE). According to the shape of the screw holes on the cortex, the fixed fracture models were divided into a control group (standard screw hole group X126, six cases) and an experimental group (elliptical screw hole group N, 36 cases). The experimental group was further divided into six subgroups with six cases in each (N126, N136, N1256, N1356, N12356, N123456), based on the number and distribution of the screws on the proximal fracture segment. The control, N126, and N136 groups were subjected to an axial load of 500 N, and the other groups were subjected to an axial load of 1000 N. The displacements of the kinetic head, far cortex, and near cortex were measured. The integral structural stiffness of the model and the near cortical strain were calculated. The data of each group were analyzed by using a paired t-test.
Results
When the far cortical strains were 2%, 5%, and 10%, the near cortical strains in group N126 were 0.96%, 2.35%, and 4.62%, respectively, significantly higher than those in the control group (X126) (p < 0.05). For a different distribution of the screws, when the far cortical strains were 2%, 5%, and 10%, the near cortical strains in group N126 were significantly higher than those in group N136 (p < 0.05). However, there was no significant difference between the near cortical strains in the two groups with four screws (p > 0.05). For different numbers of screws, the near cortical strains in the three-screw groups were significantly higher than those in the four-screw groups (p < 0.05), and there was no significant difference in near cortical strains among the four-, five-, and six-screw groups (p > 0.05).
Conclusion
The proposed drill and matching sleeves enabled a conventional locking compression plate to be transformed into an internal fixation system to improve the balanced motion of the near and far cortices. Thus, strain on a fracture site could be controlled by adjusting the diameter of the drill and the eccentricity of the sleeve.
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Meyer AP, Large TM. Early peri-implant fractures after distal femur fracture locked plating? EUROPEAN JOURNAL OF ORTHOPAEDIC SURGERY & TRAUMATOLOGY : ORTHOPEDIE TRAUMATOLOGIE 2022:10.1007/s00590-022-03398-6. [PMID: 36201033 DOI: 10.1007/s00590-022-03398-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/11/2022] [Accepted: 08/28/2022] [Indexed: 06/16/2023]
Abstract
PURPOSE To report the peri-implant fracture rates after locked plating of distal femur fractures and examine risk factors. METHODS Over a 7 year period, 89 AO/OTA 33A/C distal femur fractures were identified and reviewed. After excluding treatment with intramedullary nails, age under 50, those with the proximal femur protected, or those without 6 months of follow-up, 42 distal femur fractures in 41 patients, mean age 72.3 were studied. All were treated with lateral locked plating of distal femur fractures. The details of the constructs were recorded. Mean follow-up was 562 days (18.7 months). RESULTS 3/42 were open injuries, 9/42 were type C, 16/42 were type A, and 17 were periprosthetic above a knee arthroplasty. Two patients were treated with a dynamic plating construct using all far-cortical locking (FCL) screws in the diaphysis. 40 patients were treated with a variety of non-dynamic diaphyseal constructs including locking, non-locking, and four with 1-2 FCL screws distally. There was one asymptomatic nonunion. 2/2 patients in the dynamically plated group experienced a peri-implant fracture versus 1/40 in the non-dynamically plated group (p = 0.001). 3/9 with an all-locked construct versus 0/25 patients with a most proximal non-locking screw experienced a fracture. CONCLUSIONS The overall peri-implant fracture risk was 7.1% (3/42), 3/17 patients with a locking screw most proximal experienced a peri-implant fracture, 3/9 with an all-locking construct, and 2/2 patients with a dynamic construct experienced a fracture. These findings merit additional clinical and biomechanical study.
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Affiliation(s)
- Anna P Meyer
- Emory University Department of Orthopedic Surgery, Grady Memorial Hospital, Atlanta, GA, 30301, USA
| | - Thomas M Large
- Emory University Department of Orthopedic Surgery, Grady Memorial Hospital, Atlanta, GA, 30301, USA.
- Mission Hospital, Orthopedic Trauma Services, Asheville, NC, USA.
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Sarwar A, Gee A, Bougherara H, Kuzyk PRT, Schemitsch EH, Zdero R. Biomechanical optimization of the far cortical locking technique for early healing of distal femur fractures. Med Eng Phys 2021; 89:63-72. [PMID: 33608126 DOI: 10.1016/j.medengphy.2021.02.003] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2020] [Revised: 01/22/2021] [Accepted: 02/03/2021] [Indexed: 10/22/2022]
Abstract
This finite element study optimized far cortical locking (FCL) technology for early callus formation in distal femur fracture fixation with a 9-hole plate using FCL screws proximal to, and standard locking screws distal to, the fracture. Analyses were done for 120 possible FCL screw configurations by varying FCL screw distribution and number. A hip joint force of 700 N (i.e. 100% x body weight) was used, which corresponds to a typical 140 N "toe-touch" foot-to-ground force (i.e. 20% x body weight) suggested to patients immediately after surgery. Increased FCL screw distribution (i.e. shorter plate working length) caused a decrease at the medial side and an increase at the lateral side of the axial interfragmentary motion (AIM), mildly affected shaft and condylar cortex Von Mises max stress (σMAX), increased plate σMAX, and decreased shaft FCL screw and condylar locking screw σMAX. Increased FCL screw number decreased AIM and σMAX on the shaft cortex, condylar cortex, plate, and FCL screws, but not condylar screws. The optimal FCL screw configuration had 3 FCL screws in plate holes #1, 5, and 6 (proximal to distal) for optimal AIM of 0.2 - 1 mm and reduce shear fracture motion, thereby encouraging early callus formation.
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Affiliation(s)
- Ahmed Sarwar
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
| | - Aaron Gee
- Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada
| | - Paul R T Kuzyk
- Department of Surgery, University of Toronto, Toronto, ON, Canada
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada; Department of Surgery, Western University, London, ON, Canada
| | - Radovan Zdero
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, ON, Canada; Orthopaedic Biomechanics Lab, Victoria Hospital, (Room A6-144), 800 Commissioners Road, London, ON N6A-5W9, Canada; Department of Surgery, Western University, London, ON, Canada; Department of Mechanical and Materials Engineering, Western University, London, ON, Canada.
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Gee A, Bougherara H, Schemitsch EH, Zdero R. Biomechanical design using in-vitro finite element modeling of distal femur fracture plates made from semi-rigid materials versus traditional metals for post-operative toe-touch weight-bearing. Med Eng Phys 2020; 87:95-103. [PMID: 33461680 DOI: 10.1016/j.medengphy.2020.11.015] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2020] [Revised: 11/23/2020] [Accepted: 11/29/2020] [Indexed: 01/19/2023]
Abstract
This proof-of-concept study designs distal femur fracture plates from semi-rigid materials vs. traditional metals for toe-touch weight-bearing recommended to patients immediately after surgery. The two-fold goal was to (a) reduce stress shielding (SS) by increasing cortical bone stress thereby reducing the risk of bone absorption and plate loosening, and (b) reduce delayed healing (DH) via early callus formation by optimizing axial interfragmentary motion (AIM). Finite element analysis was used to design semi-rigid plates whose elastic moduli E ensured plates permitted AIM of 0.2 - 1 mm for early callus formation. A low hip joint force of 700 N (i.e. 100% x body weight) was applied, which corresponds to a typical 140 N toe-touch foot-to-ground force (i.e. 20% x body weight) recommended to patients after surgery. Analysis was done using 2 screw materials (steel or titanium) and types (locked or non-locked). Steel and titanium plates were also analyzed. Semi-rigid plates (vs. metal plates) had lower overall femur/plate construct stiffnesses of 508 - 1482 N/mm, higher cortical bone stresses under the plate by 2.02x - 3.27x thereby reducing SS, and lower E values of 414 - 2302 MPa to permit AIM of 0.2 - 1 mm thereby reducing DH.
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Affiliation(s)
- Aaron Gee
- Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada.
| | - Habiba Bougherara
- Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada.
| | - Emil H Schemitsch
- Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada; Department of Surgery (Division of Orthopaedic Surgery), Western University, London, Canada.
| | - Radovan Zdero
- Orthopaedic Biomechanics Lab, Room A6-144, Victoria Hospital, 800 Commissioners Road, London N6A5W9, Canada; Department of Mechanical and Industrial Engineering, Ryerson University, Toronto, Canada; Department of Surgery (Division of Orthopaedic Surgery), Western University, London, Canada; Department of Mechanical and Materials Engineering, Western University, London, Canada.
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10
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Campbell ST, Goodnough LH, Salazar B, Lucas JF, Bishop JA, Gardner MJ. How do pilon fractures heal? An analysis of dual plating and bridging callus formation. Injury 2020; 51:1655-1661. [PMID: 32434713 DOI: 10.1016/j.injury.2020.04.023] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2020] [Accepted: 04/13/2020] [Indexed: 02/02/2023]
Abstract
OBJECTIVES 1) To determine the effect of single versus dual plate metaphyseal fixation for pilon fractures on callus formation and reoperation rates, 2) to determine the effect of biomechanically matched versus unmatched fixation, and 3) to determine whether patient or surgical factors were independent predictors of bridging callus formation or need for reoperation. DESIGN Retrospective comparative study. SETTING Single level one trauma center. PATIENTS Fifty patients with AO/OTA type C2 or C3 pilon fractures treated with plate fixation. INTERVENTION Internal fixation with a plate and screw construct, with comparisons made between patients with single versus dual plate fixation, and patients treated with biomechanically matched or unmatched fixation. MAIN OUTCOME MEASUREMENTS Modified RUST (mRUST) scores at three and six months and reoperation rate. RESULTS At six months, mean mRUST scores were significantly lower in patients treated with dual metaphyseal plates compared to a single plate (8.7 vs 10.4, p=0.046) There were 15 open fractures; eight were treated with supplemental fixation, while seven were treated with single-column fixation. Open fracture (OR 51.05, p=0.008) was a risk factor for reoperation. Screw density between 0.4 and 0.5 was a protective factor against reoperation (OR 0.03, p=0.026). Biomechanically unmatched fixation did not affect mRUST scores or reoperation rates. CONCLUSIONS Pilon fractures treated with a single plate had more callus formation six months after surgery compared to those treated with dual plate fixation, and there was no difference in reoperation rates. Screw density between 0.4-0.5 was protective against reoperation. These data may serve as the basis of future work to determine the ideal fixation construct for the frequently comminuted metaphysis in pilon fractures. Further work is necessary to determine whether callus formation in these injuries is desirable. LEVEL OF EVIDENCE Three.
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Affiliation(s)
- Sean T Campbell
- Department of Orthopaedic Surgery, Stanford University Hospital, 300 Pasteur Drive Room R144, Stanford, CA, USA.
| | - L Henry Goodnough
- Department of Orthopaedic Surgery, Stanford University Hospital, 300 Pasteur Drive Room R144, Stanford, CA, USA
| | - Brett Salazar
- Department of Orthopaedic Surgery, Stanford University Hospital, 300 Pasteur Drive Room R144, Stanford, CA, USA
| | - Justin F Lucas
- Department of Orthopaedic Surgery, Santa Clara Valley Medical Center, USA
| | - Julius A Bishop
- Department of Orthopaedic Surgery, Stanford University Hospital, 300 Pasteur Drive Room R144, Stanford, CA, USA
| | - Michael J Gardner
- Department of Orthopaedic Surgery, Stanford University Hospital, 300 Pasteur Drive Room R144, Stanford, CA, USA
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