A biomechanical comparison of fixed angle locking compression plate osteosynthesis and cement augmented screw osteosynthesis in the management of intra articular calcaneal fractures

The cadaveric research model for calcaneus fractures: A scoping review of biomechanical, anatomical, radiographic and fracture fixation studies

BACKGROUND

Calcaneal fractures remain a big challenge in orthopaedic surgery and lead to long lasting disabilities. Cadaveric research plays an important role in determining optimal fracture treatment. This scoping review aims to provide insight into cadaveric research that has been conducted on calcaneal fractures, including biomechanics, fixation, approaches and radiographic studies.

METHODOLOGY

A search strategy was created and implemented as per PRISMA guidance. 3 databases, Medline, Embase and Scopus, were used when conducting this review.

RESULTS

484 individual studies were retrieved across the 3 databases, of which 186 duplicates were excluded. Study abstracts were individually reviewed, of which 208 studies were excluded in accordance with study criteria. 90 papers were sought for retrieval, of which 83 full text papers were successfully retrieved. Of the full papers retrieved, 22 did not meet our inclusion criteria, and 19 papers related only to talus fractures. In the end, 43 cadaveric studies pertaining to this scoping review were included and reviewed.

DISCUSSION

Studies were grouped into biomechanical, anatomical, fixation and radiographic studies for review.

CONCLUSION

Evaluation of current cadaveric studies pertaining to calcaneal fractures has allowed greater insight into the myriad challenges in the management of these injuries. Effects of intra-articular fractures on calcaneal biomechanics assist in establishing surgical goals. Whilst fixation studies showing good stability of nail fixations could encourage further development in minimally invasive techniques. Avoiding pitfalls seen in the extensile lateral approach. Recommendations of areas for further research include use of external fixators, fixation in non-Sanders Type 2 fractures, and comparison of intraoperative CT/3D fluoroscopy with o conventional fluoroscopy.

Biomechanical role of bone grafting for calcaneal fracture fixation in the presence of bone defect: A finite element analysis

BACKGROUND

The purpose of this study was to compare the biomechanical stress and stability of calcaneal fixations with and without bone defect, before and after bone grafting, through a computational approach.

METHODS

A finite element model of foot-ankle complex was reconstructed, impoverished with a Sanders III calcaneal fracture without bone defect and with moderate and severe bone defects. Plate fixations with and without bone grafting were introduced with walking stance simulated. The stress and fragment displacement of the calcaneus were evaluated.

FINDINGS

Moderate and severe defect increased the calcaneus stress by 16.11% and 32.51%, respectively and subsequently decreased by 10.76% and 20.78% after bone grafting. The total displacement was increased by 3.99% and 24.26%, respectively by moderate and severe defect, while that of posterior joint facet displacement was 86.66% and 104.44%. The former was decreased by 25.73% and 35.96% after grafting, while that of the latter was reduced by 88.09% and 84.78% for moderate and severe defect, respectively.

INTERPRETATION

Our finite element prediction supported that bone grafting for fixation could enhance the stability and reduce the risk of secondary stress fracture in cases of bone defect in calcaneal fracture.

Comparison between screw fixation and plate fixation via sinus tarsi approach for displaced intra-articular calcaneal fractures: a systematic review and meta-analysis

BACKGROUND

Optimal surgical fixation for displaced intra-articular calcaneal fractures (DIACF) remains a subject of debate, particularly regarding the superiority between screw fixation and plate fixation via the sinus tarsi approach (STA). This review aims to determine the preferred treatment for DIACF and compare the outcomes of minimally invasive surgery options.

METHODS

Our study involved thorough searches across multiple electronic databases, including PubMed, Cochrane, Embase, and Web of Science, to identify all relevant publications on distal intra-articular fractures of the calcaneus (DIACFs) that were fixed using cannulated screws or plates via STA. Through a comprehensive meta-analysis, we evaluated several outcomes, including post-operative function, radiological measurements, and complications.

RESULT

A total of 728 patients from 7 studies met the inclusion criteria. Among them, 435 patients underwent screw fixation via STA, and 373 patients underwent plate fixation via STA. The study found no statistically significant differences between the screw fixation and the plate fixation via sinus tarsi approach (STA) in terms of AOFAS scores, Bohler's angle, Gissane's angle, sural nerve injury, secondary subtalar arthrodesis and reoperation. Compared with screw fixation, plate fixation via STA can reduce reduction loss of Bohler's angle (WMD = - 1.64, 95% CI = [- 2.96, - 0.31], P = 0.06, I2 = 59%), lower the incidence of fixation failure (OR = 0.32, 95% CI = [0.13, 0.81], P = 0.78, I2 = 0%), and decrease intra-articular step-off (WMD = - 0.52, 95% CI = [- 0.87, - 0.17], P = 0.66, I2 = 0%).

CONCLUSIONS

Plate fixation demonstrates superior capability in restoring calcaneal width, maintaining Bohler's angle, and minimizing intra-articular step-off, thereby maintaining better reduction of the subtalar articular surface. In addition, plate fixation exhibits the modest complication rate and a low incidence of fixation failure. Therefore, we recommend the use of plate fixation through the STA, especially for complex and comminuted intra-articular calcaneal fractures.

Percutaneous balloon calcaneoplasty versus open reduction and internal fixation (ORIF) for intraarticular SANDERS 2B calcaneal fracture: Comparison of primary stability using a finite element method

INTRODUCTION

Fractures of the calcaneus are common, with 65% being intra-articular, which can lead to a major impairment of the patient's quality of life. Open reduction and internal fixation with locking plates can be considered as gold-standard technique but has a high rate of post-operative complications. Minimally invasive calcaneoplasty combined with minimally invasive screw osteosynthesis is largely drawn from the management of depressed lumbar or tibial plateau fractures. The hypothesis of this study is that calcaneoplasty associated with minimally invasive percutaneous screw osteosynthesis presents biomechanical characteristics comparable with conventional osteosynthesis.

MATERIALS AND METHODS

Eight hind feet were collected. A SANDERS 2B fracture was reproduced on each specimen, while four calcanei were reduced by a balloon calcaneoplasty method and fixed with a lateral screw, four others were manually reduced and fixed with conventional osteosynthesis. Each calcaneus was then segmented for 3D finite element modeling. A vertical load was applied to the joint surface in order to measure the displacement fields and the stress distribution according to the type of osteosynthesis.

RESULTS

Analyses of the intra-articular displacement fields showed lower overall displacements in calcaneal joints treated with calcaneoplasty and lateral screw fixation. Better stress distribution was found in the calcaneoplasty group with lower equivalent joint stresses. These results could be explained by the role of the PMMA cement as a strut, enabling better load transfer.

CONCLUSION

Balloon Calcaneoplasty combined with lateral screw osteosynthesis has biomechanical characteristics at least comparable to locking plate fixation in the treatment of SANDERS 2B calcaneal joint fractures in terms of displacement fields and stress distribution under the premise of anatomical reduction.

Comminuted intraarticular calcaneal fractures: Multiplanar VA locked plating and interlocked nailing incorporate longitudinal strut and provide superior stability - a biomechanical cadaveric study

Treatment of comminuted intraarticular calcaneal fractures remains controversial and challenging. The aim of this study was to investigate the biomechanical performance of three different methods for fixation of such fractures. Comminuted calcaneal fractures, including Sanders III AB fracture of the posterior facet and Kinner II B fracture of the calcaneocuboid joint (CCJ) articular calcaneal surface, were created in 18 human cadaveric lower legs by osteotomizing. The ankle joint, medial soft tissues and midtarsal bones along with their ligaments were preserved. The specimens were randomized to three groups for fixation with either (1) 2.7 mm variable-angle locking lateral calcaneal plate (Group 1), (2) 2.7 mm variable-angle locking anterolateral calcaneal plate in combination with one 4.5 mm and one 6.5 mm cannulated screws (Group 2), or (3) interlocking calcaneal nail with 3.5 mm screws in combination with three separate 4.0 mm cannulated screws (Group 3). All specimens were biomechanically tested to failure under axial loading in midstance foot position. Each test commenced with a quasi-static compression ramp from 50 to 200 N, followed by progressively increasing cyclic loading at 2 Hz. Starting from 200 N, the peak load of each cycle increased at a rate of 0.2 N/cycle. Interfragmentary movements were captured by motion tracking. In addition, mediolateral X-rays were taken every 250 cycles with a triggered C-arm. Böhler angle after 5000 cycles (1200 N peak load) increased significantly more in Group 1 compared to both other groups (P ≤ 0.020). Varus deformation of 10° between the calcaneal tuberosity and the lateral calcaneal fragments was reached at significantly lower number of cycles in Group 1 compared the other groups (P ≤ 0.017). Both cycles to 10° plantar gapping between the anterior process and the calcaneal tuberosity fragments, and 2 mm displacement at the CCJ articular calcaneal surface revealed no significant differences among the groups (P ≥ 0.773). From a biomechanical perspective, treatment of comminuted intraarticular calcaneal fractures using anterolateral variable-angle locking plate with additional longitudinal screws or interlocked nail in combination with separate transversal screws provides superior stability as opposed to lateral variable-angle locked plating only.

Biomechanical analysis of stability of joint depression calcaneal fractures: Fixation with locking compression plate alone compared with addition of supplemental oblique screw

Purpose

The standard treatment of calcaneus fractures is a lateral plate and screw construct. Patients at our institution have been treated with a lateral locking plate combined with one retrograde screw inserted in the oblique plane to allow immediate weight bearing. The purpose of this study was to determine whether addition of a oblique screw to a lateral plate construct increases stability.

Methods

A Sanders 2B fracture (AO/OTA 83-C2) was created in 8 pairs (16 total specimens) of cadaveric feet. All were repaired using a lateral locking plate/screws construct. One specimen in each pair was chosen randomly to receive an additional oblique screw. The specimens were tested with cyclic load of up to 800 N. Movement at the fracture sites and subsidence of the talus were tracked with a three-dimensional video analysis system.

Results

Talar subsidence was not significantly affected by the presence of the additional oblique screw (p = 0.22). The sustentaculum fragment in the case of the screw repair moved 0.39 mm while the same fragment without the additional screw repair displaced 0.12 mm (p < 0.01). Two repairs with and one repair without the additional screw failed during longer-term cyclic loading.

Conclusion

The two repair types were not statistically different in regards to talar subsidence. While statistical significance resulted in the comparison of sustentaculum fragment movement, the amount of movement did not reach a level of clinical relevance. This study demonstrated immediate stability and durability of the additional screw construct with high volume weight bearing loads.

Percutaneous Cannulated Screw Fixation vs. Plating With Minimally Invasive Longitudinal Approach After Closed Reduction for Intra-Articular Tongue-Type Calcaneal Fractures: A Retrospective Cohort Study

Objective

Displaced intra-articular tongue-type fractures are often treated with surgical interventions, and there is a lack of consensus regarding the surgical approach. This retrospective cohort study aimed to compare percutaneous cannulated screw (PCS) fixation and plating with a minimally invasive longitudinal approach (MILA) after closed reduction for the treatment of tongue-type calcaneal fractures.

Materials and Methods

A total of 77 patients with intra-articular tongue-type calcaneal fractures between September 2015 and July 2019 were included in this study. They were randomly allocated into two groups: PCS fixation (n = 32) and MILA (n = 45). The outcome measures included demographic variables, operation time (OT), preoperative time (POT), hospital stay time (HST), blood loss, visual analog scale (VAS) scores, American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot scores, postoperative complications, and imaging parameters. The patients were clinically examined at 1, 3, 6, and 12 months, with a final follow-up period of 27 months.

Results

No significant differences were observed during the follow-up in calcaneal length, height, Gissane's and Böhler's angles, VAS scores, AOFAS hindfoot scores, or complication rates between the two groups. However, the postoperative VAS scores in the PCS group were significantly lower than those in the MILA group (p < 0.05). Furthermore, the OT, POT, and HST in the PCS group were significantly shorter than those in the MILA group (p < 0.05). Blood loss was lower in the PCS group than those in the other group (p = 0.044). However, postoperative calcaneal widening was significantly smaller in the MILA group than that in the PCS group (p < 0.001).

Conclusions

After closed reduction for the treatment of tongue-type calcaneal fractures, PCS fixation was superior to MILA in terms of OT, POT, HST, blood loss, pain, and degree of comfort. Meanwhile, MILA has the advantage of restoring the calcaneal width. Under the same rehabilitation program, the two approaches showed similar abilities in maintaining the closed reduction.

Percutaneous fixation of intraarticular joint-depression calcaneal fractures with different screw configurations - a biomechanical human cadaveric analysis

PURPOSE

The aim of this study was to assess the biomechanical performance of different screw configurations for fixation of Sanders type II B joint-depression calcaneal fractures.

METHODS

Fifteen human cadaveric lower limbs were amputated and Sanders II B fractures were simulated. The specimens were randomized to three groups for fixation with different screw configurations. The calcanei in Group 1 were treated with two parallel longitudinal screws, entering superiorly the Achilles tendon insertion, and two screws fixing the intraarticular posterior facet fracture line. In Group 2 two screws entered the tuberosity inferiorly to the Achilles tendon insertion and two transverse screws fixed the posterior facet. In Group 3 two screws were inserted along the bone axis, one transverse screw fixed the posterior facet and one oblique screw was inserted from the posteroplantar part of the tuberosity supporting the posterolateral part of the posterior facet. All specimens were biomechanically tested to failure under progressively increasing cyclic loading.

RESULTS

Initial stiffness did not differ significantly between the groups, P = 0.152. Cycles to 2 mm plantar movement were significantly higher in both Group 1 (15,847 ± 5250) and Group 3 (13,323 ± 4363) compared with Group 2 (4875 ± 3480), P ≤ 0.048. No intraarticular displacement was observed in any group during testing.

CONCLUSIONS

From a biomechanical perspective, posterior facet support by means of buttress or superiorly inserted longitudinal screws results in less plantar movement between the calcaneal tuberosity and the anterior fragments. Inferiorly inserted longitudinal screws are associated with bigger interfragmentary movements.

Percutaneous subtalar joint screw fixation of comminuted calcaneal fractures: a salvage procedure

INTRODUCTION

Malunited comminuted calcaneal fractures result in poor function due subtalar joint arthritis and altered biomechanics. We aimed to assess whether percutaneous subtalar joint screws after fracture reduction provide good outcomes for these difficult injuries.

METHODS

We retrospectively analysed 15 comminuted calcaneal fractures (in 14 patients) treated with percutaneous subtalar screw fixation. All patients had a minimum of 12 months' follow-up. Six patients had open injuries. On the preoperative and the latest postoperative radiograph, Bohlers angle, Gissane angle, calcaneal inclination, width and length, absolute foot height, and posterior facet height were measured. Preoperative computed tomography scans were used to classify the fractures by Sanders classification. Clinical outcome scores were recorded postoperatively.

RESULTS

Mean age was 34.2 ± 14.2 years. Minimum follow-up was 12 months (mean 17.2 ± 4.4 months). Nine patients had a Sanders 4, 3 had a Sanders 3AB, 2 had a Sanders 3BC, and 1 had a Sanders 3AC fracture. Eighty percent of patients had their angle of Gissane, absolute foot height, calcaneal length and inclination restored by this technique. Bohlers angle was restored back into the normal range in 54% of patients. Mean postoperative AOFAS score was 74 ± 11. AOFAS scores positively correlated with postoperative Bohlers angle (Pearson's correlation coefficient 0.85; p = 0.004). One patient (7%) had a wound breakdown postoperatively and three patients (20%) had heel pain from the screws, which improved after removal.

CONCLUSION

Percutaneous subtalar screws offer a reliable option to restore calcaneal anatomy in comminuted calcaneal fractures, with low complication rates. Over 80% of patients had their angle of Gissane, calcaneal length and inclination restored, and over 50% of patients had all radiological parameters restored by this technique. It offers the benefits of percutaneous reduction and fixation and this procedure may be considered an effective first stage prior to definitive subtalar fusion. Further work is needed to review the longer-term outcomes and the conversion rate to arthrodesis.

LEVEL OF EVIDENCE

IV (case series), Therapeutic.

Posterior Inferior Comminution Significantly Influences Torque to Failure in Vertically Oriented Femoral Neck Fractures: A Biomechanical Study

OBJECTIVES

To evaluate axial fracture obliquity and posterior inferior comminution in vertically oriented femoral neck fractures (FNFs) in the physiologically young patient. A biomechanical investigation was designed to evaluate the impact of these fracture elements on torque to failure using cannulated screw (CS) and sliding hip screw fixation.

METHODS

Four Pauwels III FNF models were established in synthetic femurs: (1) vertically oriented in the coronal plane (COR), (2) coronal plane with axial obliquity (AX), (3) coronal plane with posterior inferior comminution (CCOM), and (4) coronal plane with axial obliquity and posterior inferior comminution (ACOM). In each group (n = 10), specimens were fixed using either 3 CSs or a sliding hip screw with supplemental antirotation screw (SHS). Quasistatic cyclic ramp-loading to failure was performed using a custom testing jig combining axial preloading and torsional ramp-loading. The primary outcome was torque to failure, defined as angular displacement ≥5 degrees.

RESULTS

In the CS group, torque to failure was 40.2 ± 2.6 Nm, 35.0 ± 1.4 Nm, 29.8 ± 1.5 Nm, and 31.8 ± 2.2 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In the SHS group, torque to failure was 28.6 ± 1.3 Nm, 24.2 ± 1.4 Nm, 21.4 ± 1.2 Nm, and 21.0 ± 0.9 Nm for the COR, AX, CCOM, and ACOM fracture groups, respectively (P < 0.05). In both constructs, groups with posterior inferior comminution demonstrated significantly lower torque to failure compared to the COR group (P < 0.05). The CS construct demonstrated higher torque to failure in all groups when compared to the SHS construct (P < 0.01).

CONCLUSIONS

Posterior inferior comminution significantly affects torque to failure in vertically oriented FNFs. Three peripherally placed CSs may resist combined axial and torsional loading better than a sliding hip screw construct.

Cement-augmented screw fixation for calcaneal fracture treatment: a biomechanical study comparing two injectable bone substitutes

Background

The role of cement-augmented screw fixation for calcaneal fracture treatment remains unclear. Therefore, this study was performed to biomechanically analyze screw osteosynthesis by reinforcement with either a calcium phosphate (CP)-based or polymethylmethacrylate (PMMA)-based injectable bone cement.

Methods

A calcaneal fracture (Sanders type IIA) including a central cancellous bone defect was generated in 27 synthetic bones, and the specimens were assigned to 3 groups. The first group was fixed with four screws (3.5 mm and 6.5 mm), the second group with screws and CP-based cement (Graftys® QuickSet; Graftys, Aix-en-Provence, France), and the third group with screws and PMMA-based cement (Traumacem™ V+; DePuy Synthes, Warsaw, IN, USA). Biomechanical testing was conducted to analyze peak-to-peak displacement, total displacement, and stiffness in following a standardized protocol.

Results

The peak-to-peak displacement under a 200-N load was not significantly different among the groups; however, peak-to-peak displacement under a 600- and 1000-N load as well as total displacement exhibited better stability in PMMA-augmented screw osteosynthesis compared to screw fixation without augmentation. The stiffness of the construct was increased by both CP- and PMMA-based cements.

Conclusion

Addition of an injectable bone cement to screw osteosynthesis is able to increase fixation strength in a biomechanical calcaneal fracture model with synthetic bones. In such cases, PMMA-based cements are more effective than CP-based cements because of their inherently higher compressive strength. However, whether this high strength is required in the clinical setting for early weight-bearing remains controversial, and the non-degradable properties of PMMA might cause difficulties during subsequent interventions in younger patients.

Comparing less invasive plate fixation versus screw fixation of displaced intra-articular calcaneus fracture via sinus tarsi approach

PURPOSE

The purpose of this study was to compare the post-operative radiographic and clinical outcomes of less invasive plate fixation versus screw fixation of displaced intra-articular calcaneus fractures (DIACFs) via sinus tarsi approach.

METHODS

A total of 165 consecutive DIACFs that underwent open reduction internal fixation via sinus tarsi approach from 2013 to 2018 were reviewed at least a two year follow-up. The methods of fixation were divided into two groups: less invasive plate fixation versus screw fixation of calcaneus fracture (59 vs 106, respectively). The radiographic outcomes including pre- and post-operative Bohler's and Gissane's angles were evaluated. The post-operative function was evaluated using the American Orthopaedic Foot and Ankle Society (AOFAS) hindfoot score, the Olerud and Molander Scale and the Visual Analogue Scale (VAS). The complications, the rates of implant removal and cost were also compared.

RESULTS

The average follow-up was 44.2 months in the plate groups and 47.9 months in the screw groups (P > 0.05). There was no significant difference in the Bohler's angle and Gissane's angle between the plate group and screw group during the pre-operation and the last follow-up. There was no significant difference in the final AOFAS score, Olerud and Molander score and VAS score between the two groups (P > 0.05). The total incidence of complications was 6.7% in the plate group and 6.6% in the screw group (P > 0.05). The rates of implant removal and total cost during the hospitalization in the plate group were significantly higher compared with screws group (P < 0.05).

CONCLUSION

The less invasive plate fixation versus screw fixation of DIACFs via sinus tarsi approach contributed comparable quality of reduction, complications and post-operative functional outcomes. The less invasive plate technique was significantly higher in terms of implant costs and the rate of implant removal.

Biomechanical results of percutaneous calcaneal osteotomy using two different osteotomy designs

BACKGROUND

Percutaneous osteotomy of calcaneus has been proposed to reduce the complication rate and became more and more popular. The bone cut can be performed as a straight or chevron-like (V) osteotomy using a Shannon burr. Comparative studies of straight or V-osteotomy as like as one or two screws in percutaneous calcaneal osteotomies are missing in the literature. We hypothesize that the V-osteotomy will result in a higher stiffness in biomechanical testing as the straight osteotomy using single screw for fixation.

METHODS

The straight osteotomy (9 fresh-frozen specimens) and V-osteotomy (9 fresh-frozen specimens) was performed and the calcaneal tuberosity was moved 10mm medially and slightly rotated. One 6,5mm cancellous compression screw was used for osteosynthesis. Specimens were preconditioned with 100N over 100 cycles. The force was increased after every 100N by 100N from 200 to 500N. This was followed by cyclic loading with 600N for 500 cycles.

RESULTS

Despite the higher mean values of the group with V-osteotomy, no significant difference was registered between the two groups regarding the stiffness at all force levels. A higher failure rate was observed in the group with straight osteotomy.

CONCLUSION

The moderate correlation of bone density and stiffness in the V-group, and significantly lower failure rate with no secondary dislocation in fluoroscopy indicates the superiority of the V-osteotomy in the present study. Whether the demonstrated advantages can be reflected in clinical practice should be investigated in further studies.

LEVEL OF CLINICAL EVIDENCE

5.

Sinus Tarsi Approach with Screws-Only Fixation for Displaced Intra-Articular Calcaneal Fractures

Treatment of displaced intra-articular calcaneal fractures has changed numerous times in the last decades. Currently, less invasive surgery has reemerged and is increasingly used. The sinus tarsi approach is most commonly used. It combines the open approach to the subtalar joint with percutaneous reduction of the overall shape of the calcaneus. The results in the literature show overall similar functional outcome compared with the extended lateral approach, however with a significant reduction in wound complications. This article deals with the sinus tarsi approach in which the reduction is fixated using screws only. Indications, surgical technique, and possible pitfalls are discussed.

Screw tip augmentation leads to improved primary stability in the minimally invasive treatment of displaced intra-articular fractures of the calcaneus: a biomechanical study

PURPOSE

To investigate if the stability of minimally invasive screw osteosynthesis of displaced intra-articular calcaneal fractures (DIACF) can be effectively increased by an innovative approach to screw tip augmentation.

METHODS

In eight-paired human cadaver hindfoot specimens, DIACF of Sanders type IIB were treated with either standard screw osteosynthesis or with bone cement augmentation of the screw tips in the main fragments. The instrumented specimens were subjected to a cyclic loading protocol (9000 cycles, with stepwise increasing loads, 100-1000 N). The interfragment motions were quantified as tuber fragment tilt (TFT) and posterior facet inclination angle (PFIA) using a 3-D motion analysis system. Böhler's angle (BA) was evaluated from X-rays. A load-to-failure test was performed after the cyclic loading protocol.

RESULTS

All but one specimen of the augmented group withstood more cycles than the respective specimens of the non-augmented group. Mean cycles to failure for the failure criterion of 5° TFT were 7299 ± 1876 vs. 3864 ± 1810, corresponding to loads of 811 N ± 195 vs. 481 N ± 180, (P = 0.043). There were no significant differences observed in the PFIAs. The failure criterion of 5° BA was reached after a mean of 7929 cycles ± 2004 in the augmented group and 4129 cycles ± 2178 in the non-augmented group, corresponding to loads of 893 N ± 200 vs. 513 N ± 218, (P = 0,090). The mean load-to-failure of the four specimens in the augmented group that completed the cyclic loading was 1969 N over a 1742-2483 N range.

CONCLUSION

Screw tip augmentation significantly improved the mechanical stability of the calcanei after osteosynthesis in terms of decreased tuber fragment tilts and less changes in Böhler's angle.

Fixation Methods for Calcaneus Fractures: A Systematic Review of Biomechanical Studies Using Cadaver Specimens

Calcaneal fractures are notoriously difficult to treat and wound complications occur often. However, owing to the rare nature of these fractures, clinical trials on this subject are lacking. Thus, biomechanical studies form a viable source of information on this subject. With our systematic review of biomechanical studies, we aimed to provide an overview of all the techniques available and guide clinicians in their choice of method of fracture fixation. A literature search was conducted using 3 online databases to find biomechanical studies investigating methods of fixation for calcaneal fractures. A total of 14 studies investigating 237 specimens were identified. Large diversity was found in the tested fixation methods and in the test setups used. None of the studies found a significant difference in favor of any of the fixation methods. All tested methods provided a biomechanically stable fixation. All the investigated methods of fixation for calcaneal fractures seem to be biomechanically sufficient. No clear benefit was found for locking plates in the fixation of calcaneal fractures; however, a subtle mechanical superiority might exist compared with nonlocking plates in the case of fractures in osteoporotic bone. Several of the techniques tested would be suitable for a minimal invasive approach. These should be investigated further in clinical trials.

Are Variable-Angle Locking Screws Stable Enough to Prevent Calcaneal Articular Surface Collapse? A Biomechanical Study

PURPOSE

To compare fixed- or variable-angle locking screws in calcaneal fracture plates using a sawbones biomechanical model.

METHODS

Intra-articular calcaneal fractures were created in synthetic bones. Reduction and stabilization was performed with 3 different plates. In group A, a fixed-angle locking plate was used with screws fastened perpendicularly to the plate (3.5 LCP, DePuySynthes). In groups B and C (2.7 VA-LCP, DePuySynthes and 3.5 Aptus, Medartis, respectively), fracture fixation was performed using variable-angle locking plates. Biomechanical testing was conducted. Displacement of the subtalar articular surface, stiffness, maximum displacement, change in the angle of Gissane, and mode of failure under cyclic loading at 200 N, 600 N, and 1000 N (500 cycles each) were determined.

RESULTS

No statistically significant difference of articular surface dislocation under cyclic loading was detected. The stiffness and maximum displacement did not reveal any disparity as well. The change in the angle of Gissane showed only minor displacement of the articular surface.

CONCLUSION

In our study, the resistance of variable-angle locking plates against articular surface displacement was similar to fixed-angle locking screws.

Biomechanical investigation of two plating systems for medial column fusion in foot

Background

Arthrodesis of the medial column (navicular, cuneiform I and metatarsal I) is performed for reasons such as Charcot arthropathy, arthritis, posttraumatic reconstruction or severe pes planus. However, the complication rate is still high and mainly resulting from inadequate fixation. Special plates, designed for medial column arthrodesis, seem to offer potential to reduce the complication rate. The aim of this study was to investigate biomechanically plantar and dorsomedial fusion of the medial column using two new plating systems.

Methods

Eight matched pairs of human cadaveric lower legs were randomized in two groups and medial column fusion was performed using either plantar or dorsomedial variable-angle locking compression plates. The specimens were biomechanically tested under cyclic progressively increasing axial loading with physiological profile of each cycle. In addition to the machine data, mediolateral x-rays were taken every 250 cycles and motion tracking was performed to determine movements at the arthrodesis site. Statistical analysis of the parameters of interest was performed at a level of significance p = 0.05.

Results

Displacement of the talo-navicular joint after 1000, 2000 and 4000 cycles was significantly lower for plantar plating (p≤0.039) while there was significantly less movement in the naviculo-cuneiform I joint for dorsal plating post these cycle numbers (p<0.001). Displacements in all three joints of the medial column, as well as angular and torsional deformations between the navicular and metatarsal I increased significantly for each plating technique between 1000, 2000 and 4000 cycles (p≤0.021). The two plating systems did not differ significantly with regard to stiffness and cycles to failure (p≥0.171).

Conclusion

From biomechanical point of view, although dorsomedial plating showed less movement than plantar plating in the current setup under dynamic loading, there was no significant difference between the two plating systems with regard to stiffness and cycles to failure. Both tested techniques for dorsomedial and plantar plating appear to be applicable for arthrodesis of the medial column of the foot and other considerations, such as access morbidity, associated deformities or surgeon's preference, may also guide the choice of plating pattern. Further clinical studies are necessary before definitive recommendations can be given.

History of internal fixation with plates (part 2): new developments after World War II; compressing plates and locked plates

The first techniques of operative fracture with plates were developed in the 19th century. In fact, at the beginning these methods consisted of an open reduction of the fracture usually followed by a very unstable fixation. As a consequence, the fracture had to be opened with a real risk of (sometimes lethal) infection, and due to unstable fixation, protection with a cast was often necessary. During the period between World Wars I and II, plates for fracture fixation developed with great variety. It became increasingly recognised that, because a fracture of a long bone normally heals with minimal resorption at the bone ends, this may result in slight shortening and collapse, so a very rigid plate might prevent such collapse. However, as a consequence, delayed healing was observed unless the patient was lucky enough to have the plate break. One way of dealing with this was to use a slotted plate in which the screws could move axially, but the really important advance was recognition of the role of compression. After the first description of compression by Danis with a "coapteur", Bagby and Müller with the AO improved the technique of compression. The classic dynamic compression plates from the 1970s were the key to a very rigid fixation, leading to primary bone healing. Nevertheless, the use of strong plates resulted in delayed union and the osteoporosis, cancellous bone, comminution, and/or pathological bone resulted in some failures due to insufficient stability. Finally, new devices represented by locking plates increased the stability, contributing to the principles of a more biological osteosynthesis while giving enough stability to allow immediate full weight bearing in some patients.

Post-traumatic subtalar osteoarthritis: which grading system should we use?

PURPOSE

To assess and compare post-traumatic osteoarthritis following intra-articular calcaneal fractures, one must have a reliable grading system that consistently grades the post-traumatic changes of the joint. A reliable grading system aids in the communication between treating physicians and improves the interpretation of research. To date, there is no consensus on what grading system to use in the evaluation of post-traumatic subtalar osteoarthritis. The objective of this study was to determine and compare the inter- and intra-rater reliability of two grading systems for post-traumatic subtalar osteoarthritis.

METHODS

Four observers evaluated 50 calcaneal fractures at least one year after trauma on conventional oblique lateral, internally and externally rotated views, and graded post-traumatic subtalar osteoarthritis using the Kellgren and Lawrence Grading Scale (KLGS) and the Paley Grading System (PGS). Inter- and intra-rater reliability were calculated and compared.

RESULTS

The inter-rater reliability showed an intra-class correlation (ICC) of 0.54 (95 % CI 0.40-0.67) for the KLGS and an ICC of 0.41 (95 % CI 0.26 - 0.57) for the PGS. This difference was not statistically significant. The intra-rater reliability showed a mean weighted kappa of 0.62 for both the KLGS and the PGS.

CONCLUSION

There is no statistically significant difference in reliability between the Kellgren and Lawrence Grading System (KLGS) and the Paley Grading System (PGS). The PGS allows for an easy two-step approach making it easy for everyday clinical purposes. For research purposes however, the more detailed and widely used KLGS seems preferable.