Indications and limitations of locked plating

Bicortical Compression and Construct Stability With Variable Pitch Locking Screws in Cadaveric Specimens

OBJECTIVES

A variable pitch locking screw is intended to provide interfragmentary compression combined with fixed angle stability of locking plate constructs. The objective of this study was to compare variable pitch locking screws (3.5-mm KreuLock Ti locking compression screws, Arthrex Inc., Naples, FL) with standard locking screws (from the same manufacturer) in bicortical fixation scenarios in cadaver bone by assessing (1) interfragmentary compression and plate-bone compression and (2) construct biomechanical stability.

METHODS

Nine matched pairs of fresh-frozen cadaveric specimens with an average age of 67.2 years (range, 37-83) were used. Interfragmentary compression and plate-bone compression associated with insertion of single bicortical screws were compared between the variable pitch and standard locking screws at increasing levels of torque. The specimens tested were distal tibiae having a simulated longitudinal fracture. Additionally, fibulae were osteotomized to create a stable longitudinal fracture pattern and were fixed with a 5-screw plate construct with either all variable pitch or all standard locking screws. One of the 5 screws was placed across the osteotomy without lagging. Fibulae were tested cyclically with axial with torsional loading to compare displacements, rotation, and loads at failure or tested in 4-point bending to compare construct stiffness and maximum force to failure.

RESULTS

Interfragmentary and plate-bone compression forces in the distal tibia model varied across specimens but were significantly higher with variable pitch locking screws compared with standard locking screws [512 N (SD = 324 N) vs. 79 N (SD = 64 N), P = 0.002, and 242 N (SD = 119 N) vs. 104 N (SD = 123 N), P = 0.028, respectively]. In cyclic loading of fibula constructs, no significant differences were detected in construct axial displacement or angular displacement (P > 0.05). In 4-point bending, no differences were detected in maximum force or bending stiffness (P > 0.05).

CONCLUSIONS

Variable pitch locking screws produced interfragmentary compression between cortices and plate-bone compression that was greater than that produced by standard locking screws. In a stable bicortical fibula fixation scenario under external loading, the stability of variable pitch locking screw constructs was similar to constructs with standard locking screws.

Single versus double plate fixation of humeral shaft nonunion

INTRODUCTION

Humeral shaft fractures are common fractures of the diaphysis of the humerus. The aim of this study was to evaluate factors affecting the clinical outcomes of humeral nonunions surgically treated with open reduction and single- versus double-plate fixation with grafting.

MATERIALS AND METHODS

A total of 31 patients with nonunion treated with single- or double-plate screw fixation with bone grafting were retrospectively analysed. The patients were divided into two groups according to the treatment method as Group 1 (single-plate, n = 14) and Group 2 (double-plate, n = 17). Data including demographic and clinical characteristics of the patients, initial and final treatment, type of nonunion and localisation, graft use, shortening, follow-up, time to union, Quick Disabilities of the Arm, Shoulder and Hand (Quick-DASH) scores, and patient-reported cosmetic outcomes were recorded.

RESULTS

Of the patients, eight were males, and 23 were females, with a mean age of 47.6 ± 15.8 (range, 20-86) years. Initial treatment was conservative treatment (Sarmiento brace) in seven patients, plate fixation in 22 patients, and intramedullary nailing in two patients. The mean follow-up was 31.0 ± 16.9 months in Group 1 and 25.4 ± 15.6 months in Group 2. There was one nonunion in Group 1 and three in Group 2. There were no significant differences in the union rate and time to union (p = 0.378 and p = 0.262, respectively). The mean Quick-DASH scores and cosmetic results were similar between the groups (p = 0.423 and p = 0.165, respectively). Radial nerve palsy developed in three patients in Group 2, and all these patients recovered completely during follow-up.

CONCLUSIONS

Although the double-plate fixation technique has similar clinical, radiological, and functional results to single-plate fixation, it is a more invasive and expensive technique with a longer operation time. Therefore, it should not be used as the first-line treatment option for all humeral shaft nonunion. Nevertheless, the double-plate technique may be preferred to achieve in cases requiring high stability, such as hypertrophic nonunion, osteopenia and comminuted fractures.

Precontoured dynamic compression plate using patient-specific 3D-printed models in minimally invasive surgical technique for midshaft clavicle fractures

INTRODUCTION

This study introduced a novel approach for the treatment of midshaft clavicle fractures, utilizing patient-specific 3D-printed models for accurate preoperative contouring of dynamic compression plates (DCPs) and an alternative minimally invasive plate osteosynthesis (MIPO) technique with precontoured DCPs through small vertical separated incisions.

PATIENT AND METHODS

Mirror image 3D clavicular models were reproduced from 40 patients with acute displaced midshaft clavicle fractures who underwent MIPO using precontoured DCPs inserted through small, vertical separated incisions. Exclusion criteria included patients with open fractures, pathological fractures, ipsilateral limb injury, skeletal immature patients, and those who had previous clavicle fractures or surgery. Postoperative evaluation was conducted using clinical and radiographic review. The Constant-Murley and American Shoulder and Elbow Surgeons Shoulder Scores were used for clinical evaluations, and the Patient and Observer Scar Assessment Scale was used to assess surgical scars.

RESULTS

The average time to union of all fractures was 12.88 weeks (range, 8-15) without loss of reduction. The patient-specific precontoured DCPs fitted well in all cases, with fracture consolidation and minimal three cortical sides connecting the fracture fragment. No hardware prominence and skin complications occurred, and clinical evaluation showed no existing difference compared with the contralateral sides. The average Constant-Murley and American Shoulder and Elbow Surgeons Shoulder Scores were 96.33 ± 3.66 and 93.26 ± 5.15, respectively. Two patients requested their implant removal, and scar qualities were satisfactory.

CONCLUSIONS

Our study demonstrated that the use of a patient-specific precontoured DCP, in combination with 3D printing technology, provides accurate preoperative planning, effective fracture reduction, and improved postoperative outcomes in displaced midshaft clavicle fractures. The MIPO with a patient-specific precontoured DCP through separated vertical incisions along the Langer's lines appears to be a promising option, regarding appearance, avoiding associated complications, and obviating the need for reoperation. These results suggest that this technique has merit and can be a viable option for the treatment of midshaft clavicle fractures.

Minimally invasive plate osteosynthesis for displaced midshaft clavicle fractures: An indirect reduction using joystick technique

BACKGROUND

A minimally invasive plate osteosynthesis (MIPO) technique has become increasingly popular in long bone fracture fixation as it could eliminate postoperative complications. However, the most challenging aspect of employing the MIPO for midshaft clavicle fractures among general orthopedic surgeons is the technically demanding that indirect reduction is typically a closed maneuver.

METHODS

We present a consecutive series of patients with displaced midshaft clavicle fractures undergoing clavicular fixation using the MIPO technique between January 2017 and October 2019. The joystick technique was used to obtain anatomical reduction. Clinical outcomes were assessed using the Constant-Murley and the American shoulder and elbow surgeons shoulder scores.

RESULTS

Thirty patients with a mean age of 42.44 years were included. The functional shoulder scores showed no disabilities compared with those of a healthy population. No major complications requiring re-operation were noted, and all fractures were completely healed with an average time of 12.53 weeks.

CONCLUSION

This study demonstrated that facilitating the MIPO for midshaft clavicle fractures using simple operative devices and techniques was possible. The joystick technique with the use of an external fixator for temporary stabilization is a safe and effective method that can be added to achieve anatomical alignment with the fracture site unexposed. This technique could be performed either in a fresh fracture or a delayed case with failed conservative treatment.

Spinolaminar locking plates improve fixation strength compared to pedicle screws: a biomechanical analysis

INTRODUCTION

Pedicle screw loosening is a significant complication of posterior spinal fixation, particularly among osteoporotic patients and in deformity constructs. In orthopedic trauma surgery, locking plates and screws have revolutionized the fixation of osteoporotic fractures. We have combined the traumatology principle of fixed-angle locking plate fixation with the spine principles of segmental instrumentation.

METHODS

A novel spinolaminar locking plate was designed based on morphometric studies of human thoracolumbar vertebrae. The plates were fixed to cadaveric human lumbar spines and connected to form 1-level L1-L2 or L4-L5 constructs and compared to similar pedicle screw constructs. Pure moment testing was performed to assess range of motion before and after 30,000 cycles of cyclic fatigue. Post-fatigue fixture pullout strength was assessed by applying a continuous axial tensile force oriented to the principal axis of the pedicle until pullout was observed.

RESULTS

Spinolaminar plate fixation resulted in superior pullout strength compared to pedicle screws (1,065 ± 400N vs. 714 ± 284N, p = 0.028). Spinolaminar plates performed equivalently to pedicle screws in range of motion reduction during flexion/extension and axial rotation. Pedicle screws outperformed the spinolaminar plates in lateral bending. Finally, no spinolaminar constructs failed during cyclic fatigue testing, whereas one pedicle screw construct did.

CONCLUSIONS

The spinolaminar locking plate maintained adequate fixation post-fatigue, particularly in flexion/extension and axial rotation compared to pedicle screws. Moreover, spinolaminar plates were superior to pedicle screw fixation with respect to cyclic fatiguing and pullout strength. The spinolaminar plates offer a viable option for posterior lumbar instrumentation in the adult spine.

[Related factors of revision of distal femoral fractures treated with lateral locking plate]

OBJECTIVE

To analyze the factors related to the need for revision surgery due to nonunion or internal fixation failure after the treatment of distal femoral fracture with lateral locking plate (LLP).

METHODS

Retrospective analysis was made of the clinical data of 130 cases with distal femoral fracture treated in our hospital from March 2005 to March 2019. SPSS 17.0 software (univariate analysis and Logistic regression analysis) was used to analyze the general condition [gender, age, body mass index (BMI), comorbidities, smoking history], injury related factors (energy of injury, open or closed injury, AO/OTA classification of fracture, fracture area distribution), operation related factors (operation time, reduction quality, postoperative infection) and construct characteristics of internal fixation.

RESULTS

Twelve of 130 patients who were included in the study underwent revisional surgery, with a revision rate 9.2%. Univariate analysis showed that there were significant differences in age, BMI, AO/OTA classification, fracture area distribution, operation time, reduction quality, length of plate/fracture area, length of plate/fracture area above condylar between the two groups (P < 0.05). Logistic regression analysis showed that AO/OTA classification (A3), supracondylar involved fracture, operation time, reduction quality and the length of the plate/fracture area above the condylar were the possible related factors (P < 0.05). Destruction of the medial support ability of the femur in comminuted type A3 fracture, supra-condylar cortex area fracture involvement, increase of the bending stress of the LLP due to poor fracture reduction quality, damage of the blood supply of fracture end due to long-time operation, and stress concentration caused by insufficient length of plate might be risk factors of revisional operation after the treatment of distal femoral fracture with LLP. For the patients who needed revision after LLP treatment, additional use of medial minimally invasive plate fixation and autologous bone transplantation, change to intramedullary nail fixation were commonly used clinical treatment strategies.

CONCLUSION

AO/OTA classification (A3), supracondylar involved fracture, long operation time, poor reduction quality and the length of the plate/fracture area above the condylar were the possible predictive factors of the revision in distal femoral fractures treated with lateral locking plate. The appropriate application of the locking plate and operation strategy are the key to reduce the revision rate in distal femoral fractures.

Practical approach to the native distal femur fractures in the elderly: A rapid review over the recent trends

Significant work has been done in recent years on treatment strategies for distal femur fractures. Inclusive reviews on periprosthetic fractures of distal femur have been carried out recently, but there is a lack of such reviews on the subject of native distal femur fractures in the recent literature. In this narrative review, we are set out to address the latest updates on geriatric non-periprosthetic distal femur fractures, and perform a rapid review over different treatment options, arriving at a summarized proposed treatment algorithm.

A New System for Periprosthetic Fracture Stabilization-A Biomechanical Comparison

In recent years, an increase in periprosthetic femur fractures has become apparent due to the increased number of hip replacements. In the case of Vancouver type B1 fractures, locking plate systems offer safe procedures. This study compared the distal lateral femur plate (LOQTEQ^®, aap Implantate AG) with a standard L.I.S.S. LCP^® (DePuy Synthes) regarding their biomechanical properties in fixation of periprosthetic femur fractures after hip arthroplasty. We hypothesized that the new LOQTEQ system has superior stability and durability in comparison. Eighteen artificial left femurs were randomized in two groups (Group A: LOQTEQ^®; Group B: L.I.S.S. LCP^®) and tested until failure. Failure was defined as 10° varus deformity and catastrophic implant failure (loosening, breakage, progressive bending). Axial stiffness, loads of failure, cycles of failure, modes of failure were recorded. The axial stiffness in Group A with 73.4 N/mm (SD +/− 3.0) was significantly higher (p = 0.001) than in Group B (40.7 N/mm (SD +/− 2.8)). Group A resists more cycles than Group B until 10° varus deformity. Catastrophic failure mode was plate breakage in Group A and bending in Group B. In conclusion, LOQTEQ^® provides higher primary stability and tends to have higher durability.

The effect of pearl spacing on single-cycle load-to-failure and cyclic loading parameters of 2.0 mm pearl locking plates

AIMS

To compare the mechanical performance and mode of failure in four-point bending of two different 2.0 mm "string of pearls" locking plates that differ in dimensions.

METHODS

Ten *2.0 mm, 82 mm long, 10-hole (Plate A) and ten 2.0 mm, 69 mm long, 12-hole (Plate B) Cortical Pearl Systems were secured to plate extenders and centred beneath an Instron tensile tester in four-point bending. In all constructs, a simulated fracture gap was maintained at 33 mm. Due to differences in plate dimensions, 33 mm corresponded to four pearls (Plate A) and six pearls (Plate B). Following an initial preload of 10 N, ramped single-cycle load-to-failure at 0.1 mm/second was performed in five Plate A and five Plate B constructs. Load and displacement were recorded. Constant frequency sinusoidal cyclic loading (33 N) at 20 mm/minute was performed on five Plate A and five Plate B constructs following 10 N of preload. Maximum moment and cycle count were recorded. Testing and data analysis were completed in accordance with the American Society for Testing and Materials F382-14 guidelines. Differences in performance and mode of failure were compared.

RESULTS

: Plate A constructs produced higher mean values for bending stiffness (19.8 (SD 2.0) N/mm vs. 10.1 (SD 0.6) N/mm; p < 0.001), bending structural stiffness (0.77 (SD 0.08) Nm² vs. 0.39 (SD 0.02) Nm²; p < 0.001), yield point (64.1 (SD 4.2) N vs. 54.6 (SD 3.9) N; p = 0.01), proof load (65.4 (SD 3.2) N vs. 55.6 (SD 4.0) N; p = 0.005), and bending strength (1.3 (SD 0.1) Nm vs. 1.1 (SD 0.08) Nm; p = 0.005) when compared to Plate B constructs in single cycle load-to-failure. Plate A constructs had a greater (p = 0.001) mean cycle count to failure (26,178 (SD 4,061) cycles) when compared with Plate B constructs (15,550 (SD 1,291) cycles). All plates failed by non-catastrophic plastic deformation.

CONCLUSIONS

Plate A, which is wider, thicker and has a greater spacing between pearls, was mechanically superior to Plate B in four-point bending under single-cycle load-to-failure and sinusoidal cyclic loading.

CLINICAL RELEVANCE

Although mechanical differences were identified in four-point bending, in vivo biomechanical performance remains undetermined. By selecting Plate B, the clinician may gain bone purchase through a greater number of pearls and thus screws per unit length, however, the inferior mechanical characteristics, as evaluated in four-point bending, should also be considered. Further research into the mechanical and biomechanical performance of these plating systems is warranted.

Temporal Changes in Reverse Torque of Locking-Head Screws Used in the Locking Plate in Segmental Tibial Defect in Goat Model

The objective of this study was to evaluate changes in peak reverse torque (PRT) of the locking head screws that occur over time. A locking plate construct, consisting of an 8-hole locking plate and 8 locking screws, was used to stabilize a tibia segmental bone defect in a goat model. PRT was measured after periods of 3, 6, 9, and 12 months of ambulation. PRT for each screw was determined during plate removal. Statistical analysis revealed that after 6 months of loading, locking screws placed in position no. 4 had significantly less PRT as compared with screws placed in position no. 5 (p < 0.05). There were no statistically significant differences in PRT between groups as a factor of time (p > 0.05). Intracortical fractures occurred during the placement of 151 out of 664 screws (22.7%) and were significantly more common in the screw positions closest to the osteotomy (positions 4 and 5, p < 0.05). Periosteal and endosteal bone reactions and locking screw backout occurred significantly more often in the proximal bone segments (p < 0.05). Screw backout significantly, negatively influenced the PRT of the screws placed in positions no. 3, 4, and 5 (p < 0.05). The locking plate-screw constructs provided stable fixation of 2.5-cm segmental tibia defects in a goat animal model for up to 12 months.

Effect of cyclic loading on the stability of screws placed in the locking plates used to bridge segmental bone defects

The objective of this study was to evaluate the ex vivo effect of cyclic loading on the stability of screws placed in locking plates used to bridge segmental bone defects. The primary interface stability was assessed using peak reverse torque. Eighteen, 8-hole stainless-steel 4.5 mm locking plates and 4.0-mm self-tapping locking-head screws were used to stabilize 40-mm segmental defects in goat tibiae. Treatment groups included control constructs without cyclic loading (n = 6) and constructs tested to 5000 (n = 6) and 10,000 cycles (n = 6) of 600 N compressive axial loading. The insertion of all screws was standardized to 400 N-cm insertion torque. Peak reverse torque was measured immediately after screw placement (control), or after the completion of the respective loading cycles. The difference between treatment groups was compared using univariate analysis of variance. The analysis revealed a significant difference in peak reverse torque of the screws among the treatment groups (p = .000). The mean reverse torque values equaled 343.5 ± 18.3 N-cm for non-cycled controls, 303.3 ± 25.9 and 296.0 ± 42.9 N-cm after 5000 and 10,000 cycles, respectively. Among all treatment groups, screws placed in the distal bone segment tended to have lesser peak reverse torque reduction than those placed in the proximal segment and the difference was proportional to the number of cycles (p = .562; p = .255; p = .013 in control, and after 5000 and 10,000 cycles, respectively). Cyclic loading may have a negative effect on the primary stability of screws placed in locking plate constructs used to bridge segmental bone defects and could contribute to the risk of screw loosening.

Influence of gap distance between bone and plate on structural stiffness and parallel interfragmental movement in far-cortical locking technique - a biomechanical study

Sufficient interfragmental movement is the key to successful fracture healing in the theory of secondary bone healing. The far-cortical locking technique enables both stiffness reduction and parallel motion for ideal callus formation and fracture healing, but the influence of plate-bone gap on the performance of far-cortical locking technique remains unclear. The current study conducted a series of finite element analyses with mechanical validation to clarify this issue. Plate-bone gaps were assigned by 1, 2, 3, and 4 mm in a simulated mid-shaft fracture model fixed with locking plate and six semi-rigid locking screws. Axial compressive load to 500 N was applied to the fixation structure to evaluate the structural stiffness, pattern of interfragmental movement (parallel motion), and stresses on the screws. Results revealed the increased plate-bone gaps reduced the structural in order (315.3, 288.8, 264.9, and 243.4 N/mm). Tilting angles for determining parallel interfragmental movement (1.58°-1.85°) and stresses on semi-rigid screws for evaluating implant safety were not severely altered. Greater stresses were found on the screws adjacent to the fracture site in all simulated models. The current study suggested that 1 mm gap between the locking plate and the bone shall be ideal in view of parallel motion achieved balanced callus formation in far-cortical locking technique. Issue of reducing structural stiffness with limited plate-bone gap distance should be further investigated.

Interfragmentary lag screw and locking plate combination in simple distal femoral fractures: A finite element analysis

OBJECTIVE

The aim of this study was to evaluate the strength of the locking plate and lag screw construct that is applied in two different working lengths on the simple distal femur fracture model with a finite element analysis (FEA) method.

METHODS

From the computerized tomography scan data of a 60-year-old healthy male, the AO/OTA 33A1-type fracture model was simulated; the fracture gap was stabilized with the models of locking plate construct with (groups C and D) or without an interfragmentary lag screw (groups A and B). Furthermore, 102-mm plate (groups A and C) and 82-mm plate working lengths (groups B and D) were tested using FEA. Two loading conditions (axial compression and torsion) were applied at the center of the femoral head. Construct stiffness, interfragmentary micromotion, and the peak von Mises stress (VMS) on the plate were assessed.

RESULTS

Group D provided the highest axial stiffness (1347 N/mm), and group A was the weakest (439 N/mm). With the lag screw, shear micromotion remained generally low compared with that without the screw for all axial and torsional load levels and for both plate working lengths, i.e., 0.23 mm with lag screw versus 0.43 mm without lag screw (102 mm working length, 700 N). The percentage decreases of shear micromotion under axial (350/700/1400 N) and torsional loads for the 102-mm working length were >22% and 73%, respectively; while those for the 82-mm working length were >28% and 33%, respectively. The reduction of axial micromotion was observed with the lag screw for all axial load levels as well as for both plate working lengths, i.e., 0.33 mm with lag screw versus 0.87 mm without lag screw (102-mm working length, 700 N). The percentage decreases of axial micromotion under axial loading (350/700/1400 N) for 102 mm and 82 mm working lengths were >42% and 50%, respectively. The peak VMS on the plate stayed generally low with lag screw compared with without lag screw throughout all tested load levels, as well as for both plate working lengths, i.e., 124.26 MPa versus 244.39 MPa (102 mm working length, 700 N). The percentage decreases of the peak VMS under axial (350/700/1400 N) and torsional loads for the 102-mm working length were >40% and 69%, respectively, while those for the 82-mm working length were >47% and 61%, respectively.

CONCLUSION

The current FEA concludes that in a simple distal femur fracture, adding a lag screw to a locking plate construct provides better torsional stability with a 102-mm plate working length and better axial stability with a 82-mm plate working length. Additionally, the strength of the materials is increased and implant failure can be minimized by using this technique.

Biomechanical assessment of screw safety between far cortical locking and locked plating constructs

With the emerging concerns for more flexible and less stiff bridge constructs in the interest of stimulating bone healing, the technique of far cortical locking has been designed to reduce the stiffness of locked plating (LP) constructs while retaining construct strength. This study utilized simulation with diaphyseal bridge plating biomechanical models to investigate whether far cortical locking causes larger screw fracture risk than LP during rehabilitation. The fracture risk of the screws in the far cortical locking constructs increases in the non-osteoporotic and osteoporotic diaphysis compared with the screws in the LP constructs.

Analysis of risk factors for revision in distal femoral fractures treated with lateral locking plate: a retrospective study in Chinese patients

BACKGROUND

To analyze the risk factors of revision operation after the treatment of distal femoral fracture with lateral locking plate (LLP).

METHODS

Retrospective analysis of the clinical data of 152 cases with distal femoral fracture treated in our hospital from March 2005 to March 2019. The SPSS 26.0 software (univariate analysis and logistic regression analysis) was used to analyze the general condition, fracture-related factors, operation-related factors, and construct characteristics of internal fixation.

RESULTS

Sixteen of 152 patients who were included in the study underwent revision surgery, with a revision rate 10.5%. Univariate analysis showed that there were significant differences in age, body mass index (BMI), fracture type, supracondylar involved or not, type of incision, quality of reduction, ratio of length of plate/fracture area (R1), the ratio of the length of the plate/fracture area above the condylar (R2), ratio of distance between proximal part of fracture and screw/working length of proximal plate (R3) between the two groups (P < 0.05). Logistic regression analysis showed that age [OR for age > 61.5 group is 4.900 (1.071-22.414)], fracture type [OR for A3 fracture is 8.572 (1.606-45.750), the OR for periprosthetic fracture after TKA is 9.073 (1.220-67.506)], poor reduction quality [OR is 7.663 (1.821-32.253)], and the ratio of the length of the plate/fracture area above the condylar were the possible risk factors (P < 0.05).

CONCLUSION

Age, fracture type (A3 and periprosthetic fracture after TKA), poor reduction quality, and the ratio of the length of the plate/fracture area above the condylar were the possible risk factors of the revision in distal femoral fractures treated with lateral locking plate. The appropriate application of the locking plate and operation strategy are the key to reduce the revision rate in distal femoral fractures.

Additional fixation of medial plate over the unstable lateral locked plating of distal femur fractures: A biomechanical study

INTRODUCTION

Lateral locked plating is a standard treatment option for distal femur fractures. However, the unstable conditions after lateral locked plating are increasing. The objective of this study was to investigate the biomechanical strength of additional medial plate fixation over the unstable lateral locked plating of distal femur fractures.

MATERIALS AND METHODS

A distal femur fracture model (AO/OTA 33-A3) was created with osteotomies in the composite femur. Three study groups consisting of 6 specimens each were created for single-side lateral locked plating with 6 distal locking screws (LP-6), single-side lateral locked plating with 4 distal locking screws (LP-4), and additional medial locked plating on LP-4 construct (DP-4). A compressive axial load (10 mm/min) was applied in the failure test. Mode of failure, load to failure, and ultimate displacement were documented.

RESULTS

All single-side lateral locked plating (LP-4 and LP-6) showed plate bending at the fracture gap, while none of the DP-4 showed plate bending at the fracture gap. Load to failure of DP-4 (mean 5522 N) was 17.1% greater than that of LP-6 (mean 4713.3 N, p < 0.05) and 29.2% greater than that of LP-4 (mean 4273.2 N, p < 0.05). Ultimate displacement of DP-4 (mean 5.6 mm) was significantly lower than that of LP-6 (mean 8.8 mm, p < 0.05) and LP-4 (mean 9.1 mm, p < 0.05).

CONCLUSIONS

Additional fixation of medial plate significantly increased the fracture stability in distal femur fractures fixed with the lateral locked plating. Especially in the clinical situations where sufficient stability cannot be provided at the distal segment, the medial plate may be considered as a useful biomechanical solution to obtain adequate stability for fracture healing.

Finite Element- and Design of Experiment-Derived Optimization of Screw Configurations and a Locking Plate for Internal Fixation System

Objectives

The optimization for the screw configurations and bone plate parameters was studied to improve the biomechanical performances such as reliable internal fixation and beneficial callus growth for the clinical treatment of femoral shaft fracture.

Methods

The finite element analysis (FEA) of internal fixation system under different screw configurations based on the orthogonal design was performed and so was for the different structural parameters of the locking plate based on the combination of uniform and orthogonal design. Moreover, orthogonal experiment weight matrixes for four evaluation indexes with FEA were analyzed.

Results

The analytical results showed the optimal scheme of screw configuration was that screws are omitted in the thread holes near the fracture site, and single cortical screws are used in the following holes to the distal end, while the double cortical screws are fixed in thread holes that are distal to the fracture; in the other words, the length of the screws showed an increasing trend from the fracture site to the distal end in the optimized configuration. The plate structure was optimized when thread holes gap reached 13 mm, with a width of 11 mm and 4.6 mm and 5 mm for thickness and diameter of the screw, respectively. The biomechanical performance of the internal fixation construct was further improved by about 10% based on the optimal strain range and lower stress in the internal fixation system.

Conclusions

The proposed orthogonal design and uniform design can be used in a more efficient way for the optimization of internal fixation system, which can reduce the simulation runs to about 10% compared with comprehensive test, and the methodology can be also used for other types of fractures to achieve better internal fixation stability and optimal healing efficiency, which may provide a method for an orthopedist in choosing the screw configurations and parameters for internal fixation system in a more efficient way.

Inferomedial cortical bone contact and fixation with calcar screws on the dynamic and static mechanical stability of proximal humerus fractures

BACKGROUND

This study aimed to explore the effect of retaining inferomedial cortical bone contact and fixation with calcar screws on the dynamic and static mechanical stability of proximal humerus fractures treated with a locking plate.

METHODS

Twelve Synbone prosthetic humeri (SYNBONE-AG, Switzerland) were used for a wedge osteotomy model at the proximal humerus, in four groups. In the cortex contact + screw fixation group and cortex contact group, the inferomedial cortical bone contact was retained. In the screw fixation group and control group, the inferomedial cortical bone contact was not retained. Calcar screw fixation was implemented only in the screw fixation groups. The dynamic and static mechanical stability of the models were tested with dynamic fatigue mechanics testing, quasi-static axial compression, three-point bending, and torsion testing.

RESULTS

The cortex contact + screw fixation group showed the longest fatigue life and the best stability. There was 35% difference in fatigue life between the cortex contact + screw fixation group and the cortex contact group, 43%between the cortex contact + screw fixation group and screw fixation group, and 63% between the cortex contact + screw fixation group and screw fixation group (P < 0.01). The cortex contact + screw fixation group showed the best axial compressive stiffness, bending stiffness, and torsion stiffness; these were successively decreased in the other three groups (P < 0.01).

CONCLUSION

Retaining inferomedial cortical bone contact and fixation with two calcar screws maintained fracture stability with the highest strength and minimum deformation. Of the two methods, restoration of the inferomedial cortical bone support showed better dynamic and static biomechanical properties than placement of calcar screws alone.

Is augmented LISS plating biomechanically advantageous over conventional LISS plating in unstable osteoporotic distal femoral fractures?

Treatment of complex osteoporotic distal femur fractures with the Less Invasive Stabilization System (LISS) has been associated with high complication rates. The aim of this study was to investigate the biomechanical competence of two different techniques of augmented versus conventional LISS plating. Unstable distal femoral fracture AO/OTA 33-A3 was created via osteotomies in artificial femora simulating osteoporotic bone. Three study groups, consisting of 10 specimens each, were created for fixation with either LISS plate, LISS plate with additional polylactide intramedullary graft, or LISS plate plus medial locking plate (double plating). All specimens were non-destructively tested under axial (20-150 N) and torsional (0-4 Nm) quasi-static loading. Each bone-implant construct was tested with two different working length (WL) configurations (long and short) of the LISS plate. Relative movements between the most medial superior and inferior osteotomy aspects were investigated via three-dimensional motion tracking analysis. Double plating revealed significantly smaller longitudinal and shear displacement than the other two techniques (p ≤ 0.001). In addition, LISS plus graft fixation was with significantly less longitudinal displacement in comparison to conventional LISS plating (p < 0.001). Long WL resulted in significantly higher longitudinal and shear displacement compared to short WL for LISS and LISS plus graft (p ≤ 0.032), but not for double plating (p > 0.999). In conclusion, intramedullary grafting resulted in significantly increased fracture stability under axial loading in comparison to conventional LISS plating. Although it was not efficient enough to provide comparable stability to double plating, intramedullary grafting may be considered as a useful biological alternative to the latter in a surgeon's armamentarium. © 2018 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:2604-2611, 2018.

Management of pediatric open tibia fractures with supracutaneous locked plates

We evaluated the novel application of supracutaneous locked plates in pediatric open tibia fractures. Pediatric open tibia fractures stabilized with a locked supracutaneous plate from January 2011 to December 2014 were reviewed. Twenty-eight children, mean age 8.9 years, with 29 open tibia fractures were included. Nine of these children who had metaphyseal or metadiaphyseal fractures did not require joint spanning. The mean follow-up duration was 13.5 months. The mean time to uneventful union was 11.46 weeks, with no unacceptable malunion. Supracutaneous locked plates showed early union and no refractures. They could favorably replace tubular external fixators in stabilizing pediatric open tibia fractures.

Pullout strength of 2.0 mm cancellous and cortical screws in synthetic bone

OBJECTIVE

To determine whether 2.0 mm cancellous screws are superior to 2.0 mm cortical screws when inserted into cancellous and bicortical bone.

STUDY DESIGN

Biomechanical study.

METHODS

The 2.0 mm cancellous screws and 2.0 mm cortical screws were inserted according to the recommended guidelines in synthetic cancellous and bicortical blocks. Fifteen screw-block constructs per group were tested to failure in axial pullout. Axial pullout strength and yield strength were calculated. Data were analyzed using a one-way ANOVA.

RESULTS

The 2.0 mm cortical screws achieved lower axial pullout strength than 2.0 mm cancellous screws in cancellous blocks. The 2.0 mm cortical screws achieved greater pullout strength than 2.0 mm cancellous screws in bicortical blocks.

CONCLUSION

The 2.0 mm cancellous screws may offer a biomechanical advantage in bone with thin cortices (<1 mm thick), whereas 2.0 mm cortical screws may be preferred in cortical bone with cortices measuring at least 1 mm in thickness.

Locking Cap Designs Improve Fatigue Properties of Polyaxial Screws in Upper Extremity Applications

OBJECTIVES

This study sought to examine fatigue characteristics of 2 polyaxial locking screw designs: locking cap (LC) and cross-threaded (CT). The goal was to compare LC and CT implants at 0, 10, and 15 degrees of angulation to determine the effect of locking mechanism on screw-plate interface failure. The hypothesis was that LC implants would have superior fatigue properties in comparison to CT designs and that increased angulation of the screw would have a negative impact on the fatigue life of CT implants, but would not have any effect on LC implants.

METHODS

A total of 72 screws were tested in 4 upper extremity implants. Implants were subjected to cyclic shear loads and subsequent ramp to failure. Performance characteristics were statistically compared using nonparametric statistical methods.

RESULTS

Fatigue testing demonstrated that LC designs were consistently able to sustain a significantly higher number of cyclic loads than CT designs. There were no significant differences in the number of cycles sustained by LC designs because of changes in screw angle, but CT implants exhibited decreases in screw stability with increasing angulation.

CONCLUSIONS

Likely because of the spherical screw head geometry, LC fatigue characteristics are not influenced by the orientation of the screw relative to the plate. Application of an LC in the operating room requires additional time, but provides significantly more robust fixation of the screw, especially at oblique angles to the plate and provides a more predictable and consistent biomechanical result.

Management of diaphyseal tibial fractures by plate fixation with absolute or relative stability: a retrospective study of 45 patients

Background

Fixation of diaphyseal tibial fractures by plates is not considered the best option due to complications that may eventually arise; however, if principles of stability and proper surgical techniques are used, it is possible to obtain fracture consolidation without major risks.

Methods

We conducted a cross-sectional observational descriptive study by retrospectively analyzing medical records of patients with diaphyseal tibial fractures that were treated with plates from the period between June 2011 and June 2014 at San José and Susana López Hospitals in the city of Popayan, Colombia. 3 treatment groups were created and analyzed according to the type of fracture (Association Osteosynthesis/Osteosynthesis Trauma Association AO/OTA): group I: simple fractures 42A/B, absolute stability; group II: simple fractures 42A/B, Minimally Invasive Plate Osteosynthesis (MIPO) technique, relative stability; group III: multifragmentary fractures 42C, MIPO technique, relative stability. A descriptive analysis of patients, fracture consolidation time, and complications in each group were performed.

Results

45 patients with tibial fractures treated with osteosynthesis plates were analyzed. Group I: 14 patients, 42A (n=13) and 42B (n=1), had an average consolidation time of 16.38 (SD=1.98) and 14 weeks, respectively. In group II: 19 patients, out of which 18 achieved fracture consolidation (42A n=15 and 42B n=3) with an average time of 17.4 (SD=3.33) and 17.3 weeks (SD=6.11), respectively. Finally, in group III: 12 patients all with 42C fractures with a consolidation time of 16.86 (SD=2.93) weeks. The average fracture consolidation time for all 44 patients was 16.86 weeks (SD 2.93).

Conclusions

Osteosynthesis plates are an alternative to intramedullary nailing for diaphyseal tibial fractures and their outcomes can be favorable as long as the management of soft tissues and the proper principle of stability are taken into account.

Level of evidence

IV.

Notch sensitivity jeopardizes titanium locking plate fatigue strength

INTRODUCTION

Notch sensitivity may compromise titanium-alloy plate fatigue strength. However, no studies providing head-to-head comparisons of stainless-steel or titanium-alloy locking plates exist.

MATERIALS AND METHODS

Custom-designed identically structured locking plates were made from stainless steel (F138 and F1314) or titanium alloy. Three screw-hole designs were compared: threaded screw-holes with angle edges (type I); threaded screw-holes with chamfered edges (type II); and non-threaded screw-holes with chamfered edges (type III). The plates' bending stiffness, bending strength, and fatigue life, were investigated. The stress concentration at the screw threads was assessed using finite element analyses (FEA).

RESULTS

The titanium plates had higher bending strength than the F1314 and F138 plates (2.95:1.56:1) in static loading tests. For all metals, the type-III plate fatigue life was highest, followed by type-II and type-I. The type-III titanium plates had longer fatigue lives than their F138 counterparts, but the type-I and type-II titanium plates had significantly shorter fatigue lives. All F1314 plate types had longer fatigue lives than the type-III titanium plates. The FEA showed minimal stress difference (0.4%) between types II and III, but the stress for types II and III was lower (11.9% and 12.4%) than that for type I.

CONCLUSIONS

The screw threads did not cause stress concentration in the locking plates in FEA, but may have jeopardized the fatigue strength, especially in the notch-sensitive titanium plates. Improvement to the locking plate design is necessary.

Dual plating for fixation of humeral shaft fractures: A mechanical comparison of various combinations of plate lengths

Objective

The role of plate configuration was found inconclusive on the biomechanical effects of the plate size and hole number for dual plate constructions in humeral shaft fractures. The purpose of this study was to test the biomechanical stability of various dual plate constructions.

Methods

Twenty-four left humeri (4th Generation Composite Humerus, Sawbones, Malmö, Sweden) with comminuted midshaft humeral fracture were used. Four groups of plate constructs were tested: laterally fixed 8-hole locking plate and screws were combined with anteriorly locking plates containing 0, 4, 6, or 8 holes in groups I, II, III, and IV, respectively. The alterations in axial, bending, and torsional angles were recorded.

Results

There were no fixation failures during axial, bending, or torsional stiffness testing within the elastic behavior limits. Axial stiffness was highest in Group IV. Torsional stiffness, posterior-to-anterior bending stiffness, lateral-to-medial bending stiffness, and medial-to-lateral bending stiffness were lowest in Group I.

Conclusion

The similar stiffness values for the 8-to-4 hole and 8-to-6 hole plate constructions indicate that the 8-to-4 hole construction is an option in young adults, while the stiffest 8-to-8 hole combination may be an option for osteoporotic patients.

Drilling the near cortex with elongated figure-of-8 holes to reduce the stiffness of a locking compression plate construct

PURPOSE

To compare the stiffness of locking compression plate (LCP) constructs with or without drilling the near cortex with elongated figure-of-8 holes.

METHODS

24 synthetic bones were sawn to create a 10-mm gap and were fixed with a 9-hole 4.5-mm narrow LCP. In 12 bones, the near cortex of the adjacent holes to the LCP holes was drilled to create elongated figure-of-8 holes before screw insertion. The stiffness of LCP constructs under axial loading or 4-point bending was assessed by (1) dynamic quasi-physiological testing for fatigue strength, (2) quasi-static testing for stiffness, and (3) testing for absolute strength to failure.

RESULTS

None of the 24 constructs had subcatastrophic or catastrophic failure after 10 000 cycles of fatigue loading (p=1.000). The axial stiffness reduced by 16% from 613±62 to 517±44 N/mm (p=0.012) in the case group, whereas the bending stiffness was 16±1 Nm2 in both groups (p=1.000). The maximum axial load to catastrophic failure was 1596±84 N for the control group and 1627±48 N for the case group (p=0.486), whereas the maximum bending moment to catastrophic failure was 79±12 and 80±10 Nm, respectively (p=0.919).

CONCLUSION

Drilling the near cortex with elongated figure-of-8 holes reduces the axial stiffness of the LCP construct, without compromising its bending stiffness or strength.

Reducing Fracture Risk Adjacent to a Plate With an Angulated Locked End Screw

OBJECTIVES

Locking screws often are used in the treatment of osteoporotic fractures. Studies show that locking screws can increase bone stresses at the plate end, which increases the possibility of peri-implant fracture. This study evaluates whether the technique used to insert the end screw is related to the fracture tolerance adjacent to the plate.

METHODS

Twelve groups of plate constructs were evaluated using a fibular diaphyseal surrogate with mechanical properties similar to osteoporotic bone. All inboard screws were nonlocked with only the end screw fixation differing among groups. The end screws were inserted either perpendicularly to the plate or at an angle of 30 degrees for 6- and 12-hole plates. For both orientations, the end screws were inserted nonlocked, locked, or by a locked overdrilling technique, resulting in 6 groups per plate length. The perpendicular nonlocked screws represented a control group. The constructs were tested to failure in 4-point bending to determine peak load, failure energy, and stiffness.

RESULTS

All constructs failed by peri-implant fracture along a plane through the 2 cortical holes of the end screw. Compared with the control group, an angulated locked screw at the plate end significantly increased the peak bending moment and energy required to produce a fracture for both plate lengths (6-hole, P = 0.008, P < 0.001; 12-hole, P = 0.006, P < 0.001).

CONCLUSIONS

The use of an angulated locked end screw may enhance the resistance of osteoporotic bone to peri-implant fractures caused by bending forces.

Interfragmentary lag screw fixation in locking plate constructs increases stiffness in simple fracture patterns

BACKGROUND

The aim of the current biomechanical cadaver study was to quantify the influence of an additional lag screw on construct stiffness in simple fracture models at the distal femur stabilised with a locking plate.

METHODS

For biomechanical testing paired fresh frozen human femora of 5 donors (mean age: 71 (SD 9) years) were chosen. Different locking plate configurations either with or without interfragmentary lag screw were tested under torsional load (2/4Nm/deg) or axial compression forces (500/1000N).

FINDINGS

Data show that plate constructs with interfragmentary lag screw reveal similar axial and torsional stiffness values compared to intact bone as opposed to bridging plate constructs that showed significantly lower stiffness for both loading conditions.

INTERPRETATION

The current biomechanical testing unveils that the insertion of a lag screw combined with a locking plate dominates over a bridging plate construct at the distal femur in terms of axial and torsional stiffness.

Semi-rigid screws provide an auxiliary option to plate working length to control interfragmentary movement in locking plate fixation at the distal femur

BACKGROUND

Extent and orientation of interfragmentary movement (IFM) are crucially affecting course and quality of fracture healing. The effect of different configurations for implant fixation on successful fracture healing remain unclear. We hypothesize that screw type and configuration of locking plate fixation profoundly influences stiffness and IFM for a given load in a distal femur fracture model.

METHODS

Simple analytical models are presented to elucidate the influence of fixation configuration on construct stiffness. Models were refined with a consistent single-patient-data-set to create finite-element femur models. Locking plate fixation of a distal femoral 10mm-osteotomy (comminution model) was fitted with rigid locking screws (rLS) or semi-rigid locking screws (sLS). Systematic variations of screw placements in the proximal fragment were tested. IFM was quantitatively assessed and compared for different screw placements and screw types.

RESULTS

Different screw allocations significantly affect IFM in a locking plate construct. LS placement of the first screw proximal to the fracture (plate working length, PWL) has a significant effect on axial IFM (p < 0.001). Replacing rLS with sLS caused an increase (p < 0.001) of IFM under the plate (cis-cortex) between +8.4% and +28.1% for the tested configurations but remained constant medially (<1.1%, trans-cortex). Resultant shear movements markedly increased at fracture level (p < 0.001) to the extent that plate working length increased. The ratio of shear/axial IFM was found to enhance for longer PWL. sLS versus rLS lead to significantly smaller ratios of shear/axial IFM at the cis-cortex for PWL of ≥ 62 mm (p ≤ 0.003).

CONCLUSION

Mechanical frame conditions can be significantly influenced by type and placement of the screws in locking plate osteosynthesis of the distal femur. By varying plate working length stiffness and IFM are modulated. Moderate axial and concomitantly low shear IFM could not be achieved through changes in screw placement alone. In the present transverse osteotomy model, ratio of shear/axial IFM with simultaneous moderate axial IFM is optimized by the use of appropriate plate working length of about 42-62 mm. Fixation with sLS demonstrated significantly more axial IFM underneath the plate and may further contribute to compensation of asymmetric straining.

Polyaxial Screws in Locked Plating of Tibial Pilon Fractures

This study examined the axial and torsional stiffness of polyaxial locked plating techniques compared with fixed-angle locked plating techniques in a distal tibia pilon fracture model. The effect of using a polyaxial screw to cross the fracture site was examined to determine its ability to control relative fracture site motion. A laboratory experiment was performed to investigate the biomechanical stiffness of distal tibia fracture models repaired with 3.5-mm anterior polyaxial distal tibial plates and locking screws. Sawbones Fourth Generation Composite Tibia models (Pacific Research Laboratories, Inc, Vashon, Washington) were used to model an Orthopaedic Trauma Association 43-A1.3 distal tibia pilon fracture. The polyaxial plates were inserted with 2 central locking screws at a position perpendicular to the cortical surface of the tibia and tested for load as a function of axial displacement and torque as a function of angular displacement. The 2 screws were withdrawn and inserted at an angle 15° from perpendicular, allowing them to span the fracture and insert into the opposing fracture surface. Each tibia was tested again for axial and torsional stiffness. In medial and posterior loading, no statistically significant difference was found between tibiae plated with the polyaxial plate and the central screws placed in the neutral position compared with the central screws placed at a 15° position. In torsional loading, a statistically significant difference was noted, showing greater stiffness in tibiae plated with the polyaxial plate and the central screws placed at a 15° position compared with tibiae plated with the central screws placed at a 0° (or perpendicular) position. This study showed that variable angle constructs show similar stiffness properties between perpendicular and 15° angle insertions in axial loading. The 15° angle construct shows greater stiffness in torsional loading.

Use of screw locking elements improves radiological and biomechanical results of femoral osteotomies

BACKGROUND

Dynamic compression plate (DCP) constructs provide inadequate fixation in cases of poor bone quality and early weight-bearing. Screw locking elements (SLE) are flat locking nuts placed at the end of the screw to prevent screw stripping from the bone, improving fixation stability. The purpose of this work was to compare biomechanical and radiological evaluations of femoral ovine osteotomies fixed using DCP constructs with and without SLE.

METHOD

A dyaphyseal femoral osteotomy was performed in sixteen adult sheep and fixed with a DCP and cortical screws. Half of the animals were operated on with a SLE on each side of the osteotomy and the rest without the addition of SLE. Four animals of each group were euthanized after 8 weeks, and the remaining after 16 weeks. Both femora of each animal were radiographed and mechanically tested in torsion.

RESULTS

Radiologically femoral malalignment or screw loosening was observed in six out of the eight animals operated on without SLE. In contrast, all animals subjected to the operation with SLE showed complete radiological consolidation of the osteotomy. Seven of these eight animals showed normal femoral alignment and no osteosynthesis failure. Stiffness of the bones fixed with SLE was among 145% and 177% the value of their contralateral non-operated femurs (all animals of this group showed greater stiffness on the operated bone than its contralateral non-operated femur). However, stiffness of the bones operated on without SLE was among 58% and 87% the value of the stiffness of their contralateral non-operated bone (all animals of this group showed greater stiffness on the non-operated bone than the osteotomized ones).

CONCLUSIONS

Use of SLE avoided loosening of the system and stimulated stronger osteotomy consolidation. Clinical application of this improved system may thus be a feasible and cost-effective alternative to other more rigid and expensive bone fixation techniques.

Biomechanical comparison of bicortical locking versus unicortical far-cortex-abutting locking screw-plate fixation for comminuted radial shaft fractures

PURPOSE

To provide comparative biomechanical evaluation of bicortical locking versus unicortical-abutting locking screw-plate fixation in a comminuted radius fracture model.

METHODS

A validated synthetic substitute of the adult human radius with a 1.5-cm-long segmental mid-diaphyseal defect was used in the study to simulate a comminuted fracture. Stabilization was achieved with an 8-hole locking plate and either bicortical screws or unicortical-abutting screws. The specimens were tested using nondestructive cyclical loading in 4-point bending, axial compression, and torsion to determine stiffness and displacement and subsequently in 4-point bending to assess load to failure.

RESULTS

There were no statistically significant differences between bicortical versus unicortical-abutting locking screw fixation in nondestructive 4-point bending, axial compression, and torsion. Both locking screw constructs also demonstrated comparable 4-point bending loads to failure.

CONCLUSION

The biomechanical equivalence between bicortical locking versus unicortical-abutting locking screw-plate fixation suggests that adequate locking plate fixation can be achieved without perforation of the far cortex. The abutment of the screw tip within the far cortex enhances the unicortical screw positional stability and thereby effectively opposes the displacement of the screw when subjected to bending or axial or rotational loads.

CLINICAL RELEVANCE

Unicortical-abutting screws potentially offer several clinical advantages. They eliminate the need for drilling through the far cortex and thereby a risk of adjacent neurovascular injury or soft tissue structure compromise. They eliminate the issues associated with symptomatic screw prominence. They can decrease risk of refracture after screw-plate removal. In case of revision plating, they permit conversion to bicortical locking screws through the same near-cortex screw holes, which eliminates the need for a longer or repositioned plate.

Minimally invasive plate osteosynthesis with a locking compression plate is superior to open reduction and internal fixation in the management of the proximal humerus fractures

BACKGROUND

The use of minimally invasive plate osteosynthesis (MIPO) via anterolateral deltoid splitting has good outcomes in the management of proximal humerus fractures. While using this approach has several advantages, including minimal soft tissue disruption, preservation of natural biology and minimal blood loss, there is an increased risk for axillary nerve damage. This study compared the advantages and clinical and radiological outcomes of MIPO or open reduction and internal fixation (ORIF) in patients with proximal humerus fractures.

METHODS

A matched-pair analysis was performed, and patient groups were matched according to age (±3 years), sex and fracture type. Forty-three pairs of patients (average age: MIPO, 63 and ORIF, 61) with a minimum follow-up of 12 months were enrolled in the study group. The patients were investigated radiographically and clinically using the Constant score.

RESULTS

The MIPO technique required less surgery time and caused less blood loss compared to ORIF (p < 0.01). In addition, MIPO required a smaller incision, resulted in less scarring, and was cosmetically more appealing and acceptable to female patients than ORIF. Following MIPO, patients had better functional results at 3 and 6 months, with better outcomes, less pain, higher satisfaction in activities of daily living, and a higher range of motion when compared to ORIF (p < 0.05). Fracture configuration, according to the AO/ASIF(Association for the Study of Internal Fixation) fracture classification, did not significantly influence the functional results. The complication rate was comparable between both groups.

CONCLUSION

The use of MIPO with a locking compression plate in the management of proximal humerus fractures is a safe and superior option compared to ORIF.

Dual plating of humeral shaft fractures: orthogonal plates biomechanically outperform side-by-side plates

BACKGROUND

Single large-fragment plate constructs currently are the norm for internal fixation of middiaphyseal humerus fractures. In cases where humeral size is limited, however, dual small-fragment locking plate constructs may serve as an alternative. The mechanical effects of different possible plate configurations around the humeral diaphysis may be important, but to our knowledge, have yet to be investigated.

QUESTIONS/PURPOSES

We used finite element analysis to compare the simulated mechanical performance of five different dual small-fragment locking plate construct configurations for humeral middiaphyseal fracture fixation in terms of (1) stiffness, (2) stress shielding of bone, (3) hardware stresses, and (4) interfragmentary strain.

METHODS

Middiaphyseal humeral fracture fixation was simulated using the finite element method. Three 90° and two side-by-side seven-hole and nine-hole small-fragment dual locking plate configurations were tested in compression, torsion, and combined loading. The configurations chosen are based on implantation using either a posterior or anterolateral approach.

RESULTS

All three of the 90° configurations were more effective in restoring the intact compressive and torsional stiffness as compared with the side-by-side configurations, resulted in less stress shielding and stressed hardware, and showed interfragmentary strains between 5% to 10% in torsion and combined loading.

CONCLUSIONS

The nine-hole plate anterior and seven-hole plate lateral (90° apart) configuration provided the best fixation. Our findings show the mechanical importance of plate placement with relation to loading in dual-plate fracture-fixation constructs.

CLINICAL RELEVANCE

The results presented provide novel biomechanical information for the orthopaedic surgeon considering different treatment options for middiaphyseal humeral fractures.

[Mono- versus polyaxial locking plates]

Conventional plate osteosynthesis is undergoing a period of transition. The concept of locking plate osteosynthesis is of special importance. Monoaxial locking plate osteosynthesis has shown promising results (rapid bone healing via callus, minimal soft tissue irritation, advantageous in osteoporosis). Some implants allow for polyaxial locking. The first results of comparative studies concerning biomechanics and clinical outcome of mono- versus polyaxial locking plates are presented.

A novel technique for pediatric femoral locked submuscular plate removal: the 'push-pull' technique

Submuscular and minimally invasive plate insertion is gaining popularity reducing the need for large open approaches and resulting in a smaller operative ‘footprint.’ With pediatric fractures and titanium implants, fibrous and osseous ingrowth to the implant and osseous implant integration may interfere with implant removal. Therefore, the small minimally invasive implant insertion procedure may require a large maximally invasive exposure for implant removal after fracture healing. To reduce soft tissue damage, bleeding, scarring, and pain associated with implant removal, a minimally invasive procedure utilizing the pre-existing incisions while controlling the implant is efficient and beneficial. The surgical technique is described, and a case series of 21 treated pediatric femoral fractures illustrates the successful performance of the procedure and its limitations.

An alternative patellar fracture fixation: a biomechanical study

OBJECTIVES

The purpose of this study is to compare open reduction and internal fixation of the patella with a locking plate and tension-band construct (PF) versus cannulated screws and tension-band fixation (SF). The hypothesis is that both constructs will have similar failure loads with simulated extension loading.

METHODS

Transverse patellar fractures were created in 10 cadaveric pairs of legs and were fixed with either PF or SF. Dual-energy X-ray Absorptiometry (DXA) scans of all calcanei measured bone mineral density (BMD). Using an MTS 810 servohydraulic testing machine, each leg cycled to full extension 10 times before loading to failure. A differential variable reluctance transducer measured the distraction of the patella. Data were analyzed using paired t test analysis and bivariate analysis for Pearson correlation coefficients.

RESULTS

There was no difference in the BMD between the PF and the SF groups (P = 0.367). No measurable differences occurred during the 10 cycles, and load at clinical failure was not significantly different between the 2 fixation groups (P = 0.38). Stiffness during the final loading cycle was significantly higher for the SF group (P = 0.008). Ultimate strength of fixation was significantly higher in PF group (P = 0.048). BMD was not correlated to the ultimate strength of SF (P = 0.112), but was correlated for PF (P = 0.025).

CONCLUSIONS

Based on our results, PF provides comparable strength to SF, and it seems to be a safe and effective alternative to the current gold standard.

Patterns of CT use and surgical intervention in upper limb periarticular fractures at a level-1 trauma centre

OBJECTIVES

The universal availability of CT scanners has led to lower thresholds for imaging despite significant financial costs and radiation exposure. We hypothesised that this recent trend has increased the use of CT for upper limb periarticular fractures and led to more frequent operative management.

METHOD

A 5-year retrospective study (01/07/2005-30/06/2010) was performed on all adult patients with upper extremity periarticular fractures (OTA: 11, 13, 21 and 23) admitted to a level-1 trauma centre. Patients were identified from the institution's prospectively maintained OTA classification database.

RESULTS

A total of 1734 upper extremity periarticular fractures were identified in 1651 patients. 65% (1132/1734) were operated on. 32% (557/1734) had CT imaging and 78% (431/557) of these had operative management. CT use for all fractures and ages showed no change (0.56%/year, p = 0.210, r(2) = 0.457). Operative intervention increased at a rate of 2.17%/year (p = 0.004, r(2) = 0.959). Within each fracture type, CT rates showed no change. Operative management of proximal humerus and distal radius fractures became more frequent (6.30%/year, p = 0.002, r(2) = 0.969 and 0.96%/year, p = 0.046, r(2) = 0.784 respectively). Fractures around the elbow showed no change. In patients younger than 55 years, only proximal humerus fractures had more frequent imaging (3.17%/year, p = 0.023, r(2) = 0.866). In patients over 55 the frequency of CT scanning did not increase, but they were more frequently operated on (4.09%/year, p = 0.012, r(2) = 0.907). In older patients the rate of surgical intervention increased in all but the distal humerus region, Proximal humerus (6.19%/year, p = 0.015, r(2) = 0.894), proximal forearm (4.57%/year, p = 0.007, r(2) = 0.931) and distal radius (2.70%/year, p = 0.002, r(2) = 0.871).

CONCLUSION

During the examined 5-year period no increases of in CT imaging frequency were observed. The significantly increased number of operations among older patients is unlikely to be driven by imaging frequency.

Does medial support decrease major complications of unstable proximal humerus fractures treated with locking plate?

BACKGROUND

The purpose of this study was to evaluate the role of medial support and clinical factors responsible on outcomes and major complications associated with treatment of unstable proximal humerus fractures using a locking plate and suture augmentation.

METHODS

Sixty-three cases in 62 patients (42 female, 20 male) were evaluated between September 2004 and October 2008. Cases were divided into either a medial support group (36 cases) or non-medial support group (27 cases). Clinical and radiographic evaluations included Neer's evaluation criteria, the neck-shaft angle using the Paavolainen method, and complications. We analyzed the correlation between bone- and fracture- related complications and three independent clinical variables, such as the presence of medial support, fracture type, and osteoporosis by way of multivariate logistic regression.

RESULTS

There were statistically significant differences in the overall incidence of complications based on the presence of medial support (p = 0.014) and preoperative fracture type (p = 0.018), but no differences based on the presence of osteoporosis (p = 0.157). According to multivariate logistic regression analysis, the restoration of medial support was the most reliable factor to prevent bone- and fracture- related complications. In addition, when we compared the incidence of bone- and fracture-related complications in the presence or absence of medial support among 30 patients with osteoporosis, the group with restoration of medial support had only one complication of humeral head osteonecrosis despite the presence of osteoporosis (5.9% vs. 46.2%, p = 0.025). According to Neer's criteria, excellent or satisfactory clinical results accounted for seventy-three percent of the total cases (46 of 63 cases). Seventy-eight percent (49 of 55 cases) showed good radiographic results by the Paavolainen method. There were 14 complications in 13 of 63 cases (20.6%).

CONCLUSIONS

In the treatment of unstable proximal humerus fractures with locking plate technology and suture augmentation, we suggest that obtaining medial support is an important factor in preventing major bone- and fracture-related postoperative complications such as reduction loss or nonunion.

Locked versus nonlocked plate fixation for first metatarsophalangeal arthrodesis: a biomechanical investigation

BACKGROUND

First metatarsophalangeal (MTP) arthrodesis using dorsal plate fixation is a common procedure for painful conditions of the great toe. Locked plates have become increasingly common for arthrodesis procedures in the foot, including the hallux MTP joint. The biomechanical advantages and disadvantages of these plates are currently unknown. The purpose of this study was to compare locked and nonlocked plates used for first MTP fusion for strength and stiffness.

MATERIALS AND METHODS

The first ray of nine matched pairs of fresh-frozen cadaveric feet underwent dissection, preparation with cup-and-cone reamers, and fixation of the MTP joint with a compression screw and either a nonlocked or locked stainless steel dorsal plate. Each specimen was loaded in a cantilever fashion to 90 N at a rate of 3 Hz for a total of 250,000 cycles. The amount of plantar MTP gap was recorded using a calibrated extensometer. Load-to-failure testing was performed for all specimens that endured the entire cyclical loading. Stiffness was calculated from the final load-to-failure test.

RESULTS

The locked plate group demonstrated significantly less plantar gapping during fatigue endurance testing from cycle 10,000 through 250,000 (p < .05). Mean stiffness was significantly greater in the locked plate group compared with the nonlocked plate group (p = .02). There was no significant difference in load to failure between the two groups (p = .27).

CONCLUSION

Compared with nonlocked plates, locked hallux MTP arthrodesis plates exhibited significantly less plantar gapping after 10,000 cycles of fatigue endurance testing and significantly greater stiffness in load-to-failure testing.

CLINICAL RELEVANCE

As the use of locked plate technology is becoming increasingly common for applications in the foot, a thorough understanding of the biomechanical characteristics of these implants may help optimize their indications and clinical use.