A biomechanical study of headless compression screws versus a locking plate in radial head fracture fixation

The effect of Ding's screws and tension band wiring for treatment of olecranon fractures: a biomechanical study

Although tension band wiring (TBW) is popular and recommended by the AO group, the high rate of complications such as skin irritation and migration of the K-wires cannot be ignored. Ding's screw tension band wiring (DSTBW) is a new TBW technique that has shown positive results in the treatment of other fracture types. The objective of this study was to evaluate the stability of DSTBW in the treatment of olecranon fractures by biomechanical testing. We conducted a Synbone biomechanical model by using three fixation methods: DSTBW, intramedullary screw and tension band wiring (IM-TBW), and K-wire TBW, were simulated to fix the olecranon fractures. We compared the mechanical stability of DSTBW, IM-TBW, and TBW in the Mayo Type IIA olecranon fracture Synbone model using a single cycle loading to failure protocol or pullout force. During biomechanical testing, the average fracture gap measurements were recorded at varying flexion angles in three different groups: TBW, IM-TBW, and DSTBW. The TBW group exhibited measurements of 0.982 mm, 0.380 mm, 0.613 mm, and 1.285 mm at flexion angles of 0°, 30°, 60°, and 90° respectively. The IM-TBW group displayed average fracture gap measurements of 0.953 mm, 0.366 mm, 0.588 mm, and 1.240 mm at each of the corresponding flexion angles. The DSTBW group showed average fracture gap measurements of 0.933 mm, 0.358 mm, 0.543 mm, and 1.106 mm at the same flexion angles. No specimen failed in each group during the cyclic loading phase. Compared with the IM-TBW and TBW groups, the DSTBW group showed significant differences in 60° and 90° flexion angles. The mean maximum failure load was 1229.1 ± 110.0 N in the DSTBW group, 990.3 ± 40.7 N in the IM-TBW group, and 833.1 ± 68.7 N in the TBW group. There was significant difference between each groups (p < 0.001).The average maximum pullout strength for TBW was measured at 57.6 ± 5.1 N, 480.3 ± 39.5 N for IM-TBW, and 1324.0 ± 43.8 N for DSTBW. The difference between maximum pullout strength of both methods was significant to p < 0.0001. DSTBW fixation provides more stability than IM-TBW and TBW fixation models for olecranon fractures.

Biomechanical comparison of three fixation strategies for radial head fractures: a biomechanical study

Second-generation headless compression screws (HCSs) are commonly used for the fixation of small bones and articular fractures. However, there is a lack of biomechanical data regarding the application of such screws to radial head fractures. This study evaluated the mechanical properties of the fixation of radial head fractures using a single oblique HCS compared with those obtained using a standard locking radial head plate (LRHP) construct and a double cortical screw (DCS) construct. Radial synbone models were used for biomechanical tests of HCS, LRHP, and DCS constructs. All specimens were first cyclically loaded and then loaded to failure. The stiffness for the LRHP group was significantly higher than that for the other two groups, and that for the HCS group was significantly higher than that for the DCS group. The LRHP group had the greatest strength, followed by the HCS group and then the DCS group. The HCS construct demonstrated greater fixation strength than that of the commonly used cortical screws, although the plate group was the most stable. The present study revealed the feasibility of using a single oblique HCS, which has the advantages of being buried, requiring limited wound exposure, and having relatively easy operation, for treating simple radial head fractures.

Biomechanical comparison of headless compression screws versus independent locking screw for intra-articular fractures

PURPOSE

Headless compression screws (HCS) have a variable thread pitch and headless design enabling them to embed below the articular surface and generate compression force for fracture healing without restricting movement. Locking screws have greater variety of dimensions and a threaded pitch mirroring the design of the HCS. The objective of this study is to determine whether locking screws can generate compression force and compare the compressive forces generated by HCS versus locking screws.

METHOD

A comparison between 3.5-mm HCS versus 3.5-mm locking screws and 2.8-mm HCS versus 2.7-mm locking screws was performed using a synthetic foam bone model (Synbone) and FlexiForce sensors to record the compression forces (N). The mean peak compression force was calculated from a sample of 3 screws for each screw type. Statistical analysis was performed using the one-way ANOVA test and statistical significance was determined to be p =  < 0.05.

RESULTS

The 3.5-mm Synthes and Smith and Nephew locking screws generated similar peak compression forces to the 3.5-mm Acutrak 2 headless compression screws with no statistically significant difference between them. The smaller 2.7-mm Synthes and Smith and Nephew locking screws initially generated similar compressive forces up to 1.5 and 2 revolutions, respectively, but their peak compression force was less compared to the 2.8-mm Micro Acutrak 2 HCS.

CONCLUSION

Locking screws are able to generate compressive forces and may be a viable alternative to headless compressive screws supporting their use for intra-articular fractures.

Biomechanical comparison of different internal fixation devices for transversely unstable Mason type II radial head fractures

Background: The integrity of the radial head is critical to maintaining elbow joint stability. For radial head fractures requiring surgical treatment, headless compression cannulated screw fixation is a less invasive scheme that has fewer complications. The aim of this study was to compare the mechanical stability of different fixation devices, including headless compression cannulated screws and mini-T-plates, for the fixation of transversely unstable radial head fractures. Methods: Forty identical synthetic radius bones were used to construct transverse unstable radial head fracture models. Parallel, cross, and tripod headless compression cannulated screw fixation and mini-T plate fixation were applied. The structural stiffness of each group was compared by static shear loading. Afterward, cyclic loading was performed in each of the three directions of the radial head, and the shear stability of each group was compared by calculating the maximum radial head displacement at the end of the cycle. Findings: The mini-T plate group had the lowest structural stiffness (51.8 ± 7.7 N/mm) and the highest relative displacement of the radial head after cyclic loading (p < 0.05). The tripod headless compression cannulated screw group had the highest structural stiffness among all screw groups (p < 0.05). However, there was no significant difference in the relative displacement of the radial head between the screw groups after cyclic loading in different directions (p > 0.05). Interpretation: In conclusion, the biomechanical stability of the mini-T plate for fixation of transverse unstable radial head fractures is lower than that of headless compression cannulated screws. Tripod fixation provides more stable fixation than parallel and cross fixation with headless compression cannulated screws for the treatment of transversely unstable radial head fractures.

Mechanical Properties of Synthetic Bones Made by Synbone: A Review

Biomechanical engineers and physicists commonly employ biological bone for biomechanics studies, since they are good representations of living bone. Yet, there are challenges to using biological bone, such as cost, degradation, disease, ethics, shipping, sourcing, storage, variability, etc. Therefore, the Synbone® company has developed a series of synthetic bones that have been used by biomechanical investigators to offset some drawbacks of biological bone. There have been a number of published biomechanical reports using these bone surrogates for dental, injury, orthopedic, and other applications. But, there is no prior review paper that has summarized the mechanical properties of these synthetic bones in order to understand their general performance or how well they represent biological bone. Thus, the goal of this article was to survey the English-language literature on the mechanical properties of these synthetic bones. Studies were included if they quantitatively (a) characterized previously unknown values for synthetic bone, (b) validated synthetic versus biological bone, and/or (c) optimized synthetic bone performance by varying geometric or material parameters. This review of data, pros, cons, and future work will hopefully assist biomechanical engineers and physicists that use these synthetic bones as they develop experimental testing regimes and computational models.

Clinical efficacy of internal fixation with locking compression plates in the treatment of patients with extremity fractures and the effect on the recovery of limb function

The purpose of this study was to evaluate the clinical efficacy of internal fixation with locking compression plates (LCP) in the treatment of patients with extremity fractures and the effect on the recovery of limb function. A total of 488 patients with extremity fractures admitted to our hospital from June 2019 to December 2022 were retrospectively analyzed and divided into open reduction and internal fixation (ORIF) group (n = 236) and internal fixation with LCP group (n = 252) according to the surgical procedure. Outcome indicators included intraoperative bleeding, operative time, length of hospital stay, pain duration, quality of life, healing time of the fracture, postoperative complications, and restoration of limb function as per the X-ray examination results and Johner-Wruhs criteria. Self-rating Depression Scale and Self-rating Anxiety Scale were used to evaluate the changes of patients' negative emotions before and after treatment. LCP group was associated with significantly less intraoperative bleeding and shorter operative time, length of hospital stays, and pain duration compared with ORIF group (P < .05). Compared with ORIF group, LCP group provided more rapid fracture healing in tibial fractures, ulnar fractures, radial fractures, and external ankle fractures (P < .05). Compared with the ORIF group, patients in the LCP group showed better quality of life in terms of physical, psychological and social functions after surgery (P < .05). The incidence of postoperative complications in the LCP group was significantly lower than that in the ORIF group (19.92% vs 7.14%, P < .001). The Self-rating Depression Scale and Self-rating Anxiety Scale scores of the LCP group were lower than those of the ORIF group (P < .05). The recovery of limb function was significantly better in the LCP group than in the ORIF group (97.22% vs 85.17%, P < .001). The overall satisfaction rate of treatment in the LCP group was higher than that in the ORIF group (92.06% vs 81.90%, P < .001). Internal fixation with LCP in patients with extremity fractures can effectively promote the recovery of limb function, reduce the incidence of complications and improve the quality of life of patients.

The use of intramedullary devices for adult radial head and neck fractures. A systematic review

The management of isolated radial neck and head fractures is controversial. Plate fixation and tripod fixation are two commonly employed techniques but risk damage to soft tissues and implant-related complications. Intramedullary fixation is commonly used in pediatric cases and reduces the potential drawbacks of open fixation. This systematic review aimed to analyze outcomes of intramedullary fixation in adults in terms of function, union, and complication rates. A systematic review of the literature was conducted following the PRISMA guidelines using Medline and EMBASE's online databases. The review was registered on the PROSPERO database. Studies were appraised using the Methodological Index for non-randomized studies (MINORS) tool. Seven studies were deemed eligible for inclusion (n=55). Mean ages of patients ranged from 31.3 to 44.2 years, and mean follow-up ranged from 9 to 86 months. The Mayo Elbow Performance score (MEPs) was reported in five case series (mean scores 81.8 -97.9) and the prevalence of excellent results ranged from 71% and 83%. Although 100% of fractures united, the pooled complication rate was 24% (range 0-50%). The most common complications were elbow stiffness (7%), superficial radial nerve neuropraxia (7%), malunion (5%), and AVN (1.8%). No study reported any patients requiring revision surgery. Intramedullary fixation for radial head and neck fractures appears to provide a reliable alternative treatment option in terms of union, range of motion, and functional outcomes. Further robust trials direct comparing against open fixation techniques are required.

Is implant choice associated with fixation strength for displaced radial neck fracture: a network meta-analysis of biomechanical studies

The multitude of fixation options for radial neck fractures, such as pins, screws, biodegradable pins and screws, locking plates, and blade plates, has led to a lack of consensus on the optimal implant choice and associated biomechanical properties. This study aims to evaluate the biomechanical strength of various fixation constructs in axial, sagittal, and torsional loading directions. We included biomechanical studies comparing different interventions, such as cross/parallel screws, nonlocking plates with or without augmented screws, fixed angle devices (T or anatomic locking plates or blade plates), and cross pins. A systematic search of MEDLINE (Ovid), Embase, Scopus, and CINAHL EBSCO databases was conducted on September 26th, 2022. Data extraction was carried out by one author and verified by another. A network meta-analysis (NMA) was conducted in accordance with the Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Primary outcomes encompassed axial, bending, and torsional stiffness, while the secondary outcome was bending load to failure. Effect sizes were calculated for continuous outcomes, and relative treatment ranking was measured using the surface under the cumulative ranking curve (SUCRA). Our analysis encompassed eight studies, incorporating 172 specimens. The findings indicated that fixed angle constructs, specifically the anatomic locking plate, demonstrated superior axial stiffness (mean difference [MD]: 23.59 N/mm; 95% CI 8.12-39.06) in comparison to the cross screw. Additionally, the blade plate construct excelled in bending stiffness (MD: 32.37 N/mm; 95% CI - 47.37 to 112.11) relative to the cross screw construct, while the cross-screw construct proved to be the most robust in terms of bending load failure. The parallel screw construct performed optimally in torsional stiffness (MD: 139.39 Nm/degree; 95% CI 0.79-277.98) when compared to the cross screw construct. Lastly, the nonlocking plate, locking T plate, and cross-pin constructs were found to be inferior in most respects to alternative interventions. The NMA indicated that fixed angle devices (blade plate and anatomic locking plate) and screw fixations may exhibit enhanced biomechanical strength in axial and bending directions, whereas cross screws demonstrated reduced torsional stability in comparison to parallel screws. It is imperative for clinicians to consider the application of these findings in constraining forces across various directions during early range of motion exercises, taking into account the distinct biomechanical properties of the respective implants.

Outcomes of Radial Head Fractures Treated With the "Tripod Technique"

PURPOSE

For fractures requiring operative fixation, the "tripod technique" using headless compression screws has recently been described as a less invasive alternative to open reduction and internal fixation with plate and screws. The purpose of this study was to evaluate the clinical and radiographic outcomes of the tripod technique for the treatment of radial head and neck fractures.

METHODS

We performed a retrospective chart review of all radial head and neck fractures treated with the tripod technique at our institution over a 10-year period. Patients with less than 6 months of follow-up were excluded. Outcomes were evaluated at the latest follow-up using range of motion measurements and the Quick Disabilities of the Arm, Shoulder and Hand questionnaire.

RESULTS

We evaluated 13 patients with a mean age of 48 years and average follow-up of 72 months (range, 21-153 months). All the patients achieved union by 12 weeks after surgery. The average postoperative Quick Disabilities of the Arm, Shoulder and Hand score was 5.9 (range, 0-23). The mean flexion was 139°, and the mean extension was -8°. There were no major postoperative complications. Five patients had minor complications. No patients required a reoperation.

CONCLUSIONS

The tripod technique is a useful alternative to the traditional method of plate and screw fixation for unstable radial head and neck fractures.

TYPE OF STUDY/LEVEL OF EVIDENCE

Therapeutic IV.

Complications, Reoperations, and Long-Term Outcomes after Open Reduction Internal Fixation of Mason Classification Type II and Type III Radial Head Fractures

Introduction  The objectives of this study were to assess long-term outcomes, complications, and reoperations after open reduction internal fixation (ORIF) of radial head fractures. Materials and Methods  35 adult patients, who underwent ORIF of an isolated, displaced radial head fracture without elbow instability (Mason classification type II or III) at two tertiary care referral centers from 2000 to 2017, were identified. Patient satisfaction, pain, and QuickDASH scores were assessed by telephone follow-up at median 12.9 years. Results  The mean age of the 35 patients in our study was 39 years, and 54% were women. The median length of clinical follow-up was 175 days. Postoperative complications occurred in 54% of patients, and reoperations in 23% of patients. Multivariable logistic regression identified fixation with plate and screws versus screws alone as a risk factor for complications and reoperations. The long-term telephone follow-up response rate was 54%. At 13-year median follow-up, the average patient satisfaction was 9.6/10, the average patient-reported pain was 0.7/10, and the average QuickDASH score was 10.5. Conclusion  The long-term outcomes of ORIF of Mason classification type II and III radial head fractures are favorable; however, rates of complication and reoperation are notable and may be higher with plate-and-screw fixation.

Finite Element Analysis of Insertion Angle of Absorbable Screws for the Fixation of Radial Head Fractures

Objective

To investigate the biomechanical effects of different insertion angles of absorbable screws for the fixation of radial head fractures.

Methods

The finite element models used to simulate the fractures were created based on CT scans. Two absorbable screws were used to fix and maintain the stability of the fracture, and the angles between the screws were set to 0°, 15°, 30°, 45°, 60°, 75°, and 90°. A downward force of 100 N was applied at the stress point, which was coupled with the surface, and the distal radius was limited to six degrees of freedom. The direction and location of the applied force were the same in each model. The values of the von Mises stress and peak displacements were calculated.

Results

Under the applied load and different screw angles, the maximum von Mises stress in the screws was concentrated on the surface contacting the fracture surfaces. The maximum von Mises equivalent stress in the screw decreased when the angle increased from 0° (19.54 MPa) to 45° (13.11 MPa) and increased when the angle further increased to 90° (24.63 MPa). The peak displacement decreased as the angle increased from 0° (0.19 mm) to 45° (0.15 mm) and increased when the angle further increased to 90° (0.25 mm).

Conclusion

The computational stress distribution showed that fixation with absorbable screws is safe for patients. Moreover, the minimum von Mises stress and displacements were generated when the angle between the screws was 45°; hence, this setting should be recommended for Mason type II radial fractures.