Comprehensive biomechanical analysis of three clinically used fixation constructs for posterior malleolar fractures using cadaveric and finite element analysis

Biomechanical study of different fixation methods for posterior malleolus fracture

In this study, the biomechanical effect of six fixation methods for the treatment of posterior malleolus fracture (PMF) were analyzed by finite element method. Fixation models include five different cannulated screw fixation models (0°, 5°, 10°, 15°, 20°) and a posterior plate fixation model. The von Mises stress (VMS) and displacement were used as criteria to evaluate the biomechanical efficiency of the different fixation models. The results demonstrated that the VMS and displacement will increase as the load increases. The buttress plate has better fixed strength and biomechanics results than screws. When the screw fixation angle is 15°, the model has better fixed strength and biomechanical stability than other screws fixation models. Therefore, we recommend the screws fixation with angle of 15° for posterior malleolus fracture, which can be used to guide clinical operation.

Comparison between anterior-to-posterior screw fixation versus posterolateral approach plate fixation for posterior malleous fracture: A systematic review and meta-analysis

PURPOSE

There are two main surgical fixation methods for the posterior malleolar fractures (PMFs), the anterior-to-posterior (AP) screws or via the posterolateral (PL) approach utilizing a buttress plate. This review aims to compare the clinical outcome between the AP screw fixation and the PL plate fixation for treating PMFs.

METHODS

We searched all relevant publications about PMFs treated with AP screws or PL plates through electronic databases including the PubMed, the Cochrane Library, the Embase, the Wiley online library and the Web of Science. The meta-analysis was conducted to evaluated clinical outcomes including reduction quality, post-operative function and complications.

RESULTS

Six studies (one single randomized controlled trial and five retrospective cohort studies) were enrolled. 172 patients underwent AP screw fixation and 214 patients underwent PL plate fixation with a total of 386 patients (169 males and 217 females). The PL plating group yielded better AOFAS scores(MD = 6.97, 95 % CI=[4.68, 9.27], P＜0.00001, I2 =0 %) and was more likely to achieve excellent anatomical reduction(OR=5.49, 95 % CI=[1.06, 28.42], P = 0.04, I2 =80 %). No differences were found in the bad reduction quality, incidences of complications (arthritis, neuralgia, superficial wound healing problems and implant failure), the walking VAS scores and the dorsiflexion restriction degrees.

CONCLUSION

We suggest that the PL plate fixation method has the clinical benefit of achieving anatomical reduction and better AOFAS scores over the AP screw fixation for treating PMFs. No differences were found in the incidences of complications ( arthritis, neuralgia, superficial wound healing problems and implant failure), the walking VAS scores and the dorsiflexion restriction degrees. The posterior approach and the direct reduction are recommended for the treatment of the PMFs.

LEVEL OF CONFIDENCE

Ⅱb.

Insights into optimal surgical fixation for posterior malleolar fractures

Aims

The optimal management of posterior malleolar ankle fractures, a prevalent type of ankle trauma, is essential for improved prognosis. However, there remains a debate over the most effective surgical approach, particularly between screw and plate fixation methods. This study aims to investigate the differences in outcomes associated with these fixation techniques.

Methods

We conducted a comprehensive review of clinical trials comparing anteroposterior (A-P) screws, posteroanterior (P-A) screws, and plate fixation. Two investigators validated the data sourced from multiple databases (MEDLINE, EMBASE, and Web of Science). Following PRISMA guidelines, we carried out a network meta-analysis (NMA) using visual analogue scale and American Orthopaedic Foot and Ankle Score (AOFAS) as primary outcomes. Secondary outcomes included range of motion limitations, radiological outcomes, and complication rates.

Results

The NMA encompassed 13 studies, consisting of four randomized trials and eight retrospective ones. According to the surface under the cumulative ranking curve-based ranking, the A-P screw was ranked highest for improvements in AOFAS and exhibited lowest in infection and peroneal nerve injury incidence. The P-A screws, on the other hand, excelled in terms of VAS score improvements. Conversely, posterior buttress plate fixation showed the least incidence of osteoarthritis grade progression, postoperative articular step-off ≥ 2 mm, nonunions, and loss of ankle dorsiflexion ≥ 5°, though it underperformed in most other clinical outcomes.

Conclusion

The NMA suggests that open plating is more likely to provide better radiological outcomes, while screw fixation may have a greater potential for superior functional and pain results. Nevertheless, clinicians should still consider the fragment size and fracture pattern, weighing the advantages of rigid biomechanical fixation against the possibility of soft-tissue damage, to optimize treatment results.

Operative treatment results of posterior malleolar fractures in trimalleolar fractures with screw fixation and plate fixation: short-term results

BACKGROUND

Ankle fractures are among the most common lower limb fractures. There is no agreement about the best treatment for these fractures. This study compared the short-term results of screw and plate fixation methods.

METHODS

In this prospective study, 32 patients that underwent screw fixation for posterior malleolar fracture and 32 patients that underwent plate fixation for posterior malleolar fracture were assessed 1, 3, and 6 months after surgery.

RESULTS

The mean age in group 1 (screw fixation) and group 2 (plate fixation) was 32.56, and 37.82 ± 9.99, respectively. The frequency of gender in group 1 (screw fixation) and group 2 (plate fixation) for females and males was 20%, 80%, 4%, and 18%, respectively. The mean range of motion (ROM) in month 1 in group 1 was 89.4, in group 2 was 90.22, in month 3 in group 1 was 100.6, in group 2 was 100.36, in month 6 in group 1 was 115.4, and in group 2 was 110.68. The mean visual analog scale (VAS) in month 1 in group 1 was 6.88, in group 2 was 6.09, in month 3 in group 1 was 4.14, in group 2 was 3.63, in month 6 in group 1 was 2.56, and in group 2 was 2.54. In group 1, we had 1 case of nerve injury, 1 case of deep infection, and 3 cases of superficial infection, and in group 2, we had 2 cases of nerve injury, 2 cases of deep infection, and no case of superficial infection. The mean foot and ankle outcome score (FAOS) in group 1 was 75.44, and in group 2 was 74.36.

CONCLUSION

In our study, we were unable to indicate a superior treatment method. More comprehensive studies with larger populations are suggested.

Standardized analysis of syndesmosis stability in ankle trauma with an innovative syndesmosis-test-tool: a biomechanical study

When treating ankle fractures, the question of syndesmosis complex involvement often arises. So far, there is no standardized method to reliably detect syndesmosis injuries in the surgical treatment of ankle fractures. For this reason, an intraoperative syndesmosis-test-tool (STT) was developed and compared to the recommended and established hook-test (HT). Tests were performed on cadaveric lower legs (n = 20) and the diastasis was visualized by 3D camera. Tests were performed at 50, 80, and 100 N in native conditions and four instability levels. Instability was induced from anterior to posterior and the reverse on the opposite side. The impact on diastasis regarding the direction, the force level, the instability level, and the device used was checked using a general linear model for repeated measurement. The direction of the induced instability showed no influence on the diastasis during the stability tests. The diastasis measured with the STT increased from 0.5 to 3.0 mm depending on the instability, while the range was lower with the HT (1.1 to 2.3 mm). The results showed that the differentiation between the instability levels was statistically significantly better for the developed STT. The last level of maximum instability was significantly better differentiable with the STT compared to the HT. An average visualizable diastasis of more than 2 mm could only be achieved at maximum instability. In conclusion, the newly developed STT was superior to the commonly used HT to detect instability.

Syndesmosis dislocation and ankle ligament stress in the posterior malleolus fracture fixated - "in vitro analysis"

PURPOSE

The objectives of this study were to compare syndesmosis dislocation and ankle ligament stress after the fixation of the posterior malleolus fracture (PMF) with four different techniques by Finite Element Analysis (FEM).

METHODS

Four internal fixation techniques used for fixation of PMF were assessed by FEM: posterior one-third tubular 3.5 mm buttress plate (PP) with one screw (PP 1 screw), PP with two screws (PP 2 screws), two cannulated 3.5 mm lag screws in the anteroposterior (AP) direction (AP lag screws), and two posteroanterior (PA) cannulated 3.5 mm lag screws (PA lag screws). PMF with 30% fragment size was simulated through computational processing reconstructed from computed tomography (CT). The simulated loads of 700 N and 1200 N were applied to the proximal tibial end. The FEM evaluated the syndesmosis dislocation (mm) and stress values of the posterior tibiofibular ligament (PTFL) (in Kpa) and deltoid ligament (in Kpa) in the four mentioned subgroups.

RESULTS

We found that with a load of 700 N, syndesmosis dislocation varied from 6.5 to 7.9 mm, being the lowest and greatest for PA lag screw and PP 1 screw, respectively. In all groups was observed a greater dislocation in the syndesmosis at 1200 N of load. We observed that the stress values on the PTFL were lower for AP lag screws and PP 2 screws with 700 N and 1200 N, respectively. For both loads, PP 1 screw presented the greatest stress. Regarding the stress in the deltoid ligament, the AP lag screws presented the lowest stress for 700 N and PP 1 screw for 1200 N. For all fixation techniques, the syndesmosis displacement and ligament stresses were higher when 1200 N were imposed.

CONCLUSION

This study demonstrated that PMF fixed with lag screws presents greater stability in the distal tibiofibular syndesmosis and higher joint loadings promoted greater displacement and ligaments stress, regardless of the fixation technique. Besides, lower stress in the syndesmosis is accompanied by a greater load on the deltoid ligament.

Locking versus nonlocking plates for the treatment of posterior malleolar ankle fractures: A retrospective cohort study and cost analysis

BACKGROUND

We hypothesized that, as posterior malleolar ankle fractures usually present one or two main fragments, the buttress plating principle can be successfully achieved either with conventional nonlocking or anatomic locking posterior tibia plates, and no clinical differences should be found. The aim of this study was to evaluate the outcomes of posterior malleolar ankle (PM) fractures treated with conventional nonlocking (CNP) or anatomic locking plates (ALP), and also to compare both constructs in terms of crude costs.

METHODS

A retrospective cohort study was designed. CNP was used in 22 patients and ALP was used in 11 patients. American Orthopedic Foot and Ankle Society (AOFAS) score was registered at four weeks, 3-6 months, 12 and 24 months to assess all patients' functional status. The primary outcome was ankle and hindfoot AOFAS score at 12 months follow-up visit. All complications, radiographic evaluation and implant construct costs were also registered and compared. The average follow-up was 25.4 (range, 12-42) months.

RESULTS

No significant difference was observed between both cohorts, in terms of AOFAS score and complication rate (P > .05). We found that ALP construct is 17 times more expensive than CNP construct in our institution (P < .001).

CONCLUSION

Anatomic locking posterior tibial plates may be an interesting device when poor bone quality is present or when a true multifragmentary pilon fracture is faced. Anatomic locking posterior tibia plate should not become a regular implant for any PM fracture since equivalent clinical and radiological results were obtained in our study using CNP with a significant reduced cost.

Anterior Displacement of a Posterior Malleolar Fragment Through the Syndesmosis: A Case Report

Ankles are the most common site of injury in lower limb fractures. Despite this, the classification of the Maisonneuve fracture is still highly controversial, perhaps due to its low incidence. Typically described as a proximal fibular fracture with associated injury to the syndesmosis and medial structures secondary to an external rotation mechanism, the injury often necessitates surgical intervention to restore joint stability for good functional outcomes. A 32-year-old lady sustained a pronation external rotation injury resulting in a proximal fibula fracture with disruption of the distal tibiofibular syndesmosis as well as an associated posterior malleolar fracture with displacement of the fragment anteriorly through the syndesmosis to the ventral aspect of the ankle joint. The patient underwent surgical fixation of the posterior malleolar fracture as well as repair of the syndesmosis with a screw. This report aims to highlight the details of a Maisonneuve fracture with the rarer associated posterior malleolar fracture, and its anterior displacement through the syndesmosis, as well as provide a narrative review of the current literature.

Methods for Biomechanical Testing of Posterior Malleolar Fractures in Ankle Fractures: A Scoping Review

BACKGROUND

The treatment of posterior malleolar fractures (PMFs) is debated, including the need for surgery and method of fixation. Recent literature has suggested that fracture pattern, rather than fragment size, may be an important predictor for ankle biomechanics and functional outcome. Biomechanical studies have been conducted to provide evidence-based treatment on the effects of fracture and fixation on contact pressure and stability. The objective of this scoping review is to summarize the methodologies used in biomechanical studies on PMFs and assess whether they are sufficient to test the need for surgery and method of fixation.

METHODS

A scoping review of publications before January 2022 was performed. PubMed/Medline and Embase Ovid were searched for cadaver or finite element analysis (FEA) studies that created and tested the effects of PMFs in ankle fractures. Both cadaver and FEA studies were included. Data about fragment characteristics, mode of testing, and outcomes were charted by 2 persons from the study group. The data were synthesized when possible and compared.

RESULTS

We included 25 biomechanical studies, including 19 cadaver studies, 5 FEA studies, and 1 cadaver and FEA study. Aside from the fragment size, few other fragment characteristics were reported. Mode of testing varied with different loads and foot positions. Strong conclusions on the effects of fracture and fixation on contact pressure and stability could not be made.

CONCLUSION

Biomechanical studies on PMFs demonstrate wide variability in fragment characteristics and mode of testing, which makes it difficult to compare studies and draw conclusions on the need for surgery and method of fixation. Additionally, limited reporting of fragment measurements questions the applicability to clinical practice. The biomechanical literature on PMFs would benefit from the use of a standard classification and universal fragment measurements to match clinical injuries in future biomechanical studies. Based on this review, we recommend the Mason classification, which addresses the pathomechanism, and use of the following fragment measurements in all 3 anatomic planes when creating and describing PMFs: fragment length ratio, axial angle, sagittal angle or fragment height, and interfragmentary angle. The testing protocol needs to reflect the purpose of the study.

CLINICAL RELEVANCE

This scoping review demonstrates wide methodological diversity of biomechanical studies. Consistency in methodology should enable comparison of study results, leading to stronger evidence-based recommendations to guide surgeons in decision making and offer PMF patients the best treatment.

Disease-Specific Finite element Analysis of the Foot and Ankle

Finite-element analysis is a computational modeling technique that can be used to quantify parameters that are difficult or impossible to measure externally in a geometrically complex structure such as the foot and ankle. It has been used to improve our understanding of pathomechanics and to evaluate proposed treatments for several disorders, including progressive collapsing foot deformity, ankle arthritis, syndesmotic injury, ankle fracture, plantar fasciitis, diabetic foot ulceration, hallux valgus, and lesser toe deformities. Parameters calculated from finite-element models have been widely used to make predictions about their biomechanical correlates.

Plate versus screws fixation for the posterior malleolar fragment in trimalleolar ankle fractures

BACKGROUND

The fixation methods of posterior malleolar fracture (PMF) in trimalleolar ankle fractures is still controversial. We aim to compare clinical and radiological outcomes between plate fixation and screws fixation for PMF in trimalleolar ankle fractures.

METHODS

Literature search was performed through PubMed, EMBASE, Cochrane Library and CNKI database from databases inception to May 2022 to identify randomized controlled trial (RCT) and comparative clinical study in English or Chinese. A meta-analysis was performed using RevMan 5.1 software, and systematic review was performed when the data extracted from included studies could not be synthesized.

RESULTS

Two RCTs and six cohort studies were included. The meta-analysis results showed that articular step-off or gap in plate fixation was superior to antero-posterior screws fixation (RR = 0.28; 95%CI: 0.11, 0.76; P = 0.01). there were no significant differences in American Orthopaedic Foot & Ankle Society scores (MD = -0.19; 95%CI: -2.43, 2.05; P = 0.87), arthritis (RR = 1.67; 95%CI: 0.61, 4.55; P = 0.32), infection and total complication (RR = 1.42; 95%CI: 0.89, 2.25; P = 0.14).

CONCLUSION

Plate fixation might have better articular step-off or gap, compared with "A to P" screws fixation for the posterior malleolus in trimalleolar ankle fractures. Screw fixation could achieve shorter surgical time than plate fixation. However, no significant differences were found in AOFAS scores, arthritis, infection, sural nerve injury and total complication during the comparisons.

Biomechanical Comparison of a Closed-Loop Double Endobutton to a Lag Screw in Fixation of Posterior Malleolar Fractures

Anteroposterior (AP) lag screw, posteroanterior (PA) lag screw, or posterior buttress plate are usually performed for posterior malleolar fixation, but the biomechanically strongest technique is unclear. The aim of our study was to biomechanically compare 3 different fixation methods for posterior malleolar fractures; AP lag screw, PA lag screw, and closed-loop double endobutton. Fracture models were created using a thin blade power saw after drawing the fracture line. The resultant fracture involved 30% of the joint on the distal tibial joint surface and extends with an angulation of approximately 50 degrees using 15 tibia composite bone samples. After anatomical reduction, fixation was achieved with 3.5 mm cortical screw in PA direction and in AP direction for group PA and AP, respectively. In Group DL, fixation was achieved with a closed-loop double endobutton (double lift loop, Orthomed, Turkey). The highest compression force to generate all displacement amounts was required for the double loop group (Group DL). The strongest fixation against compression was a double loop. The PA group was the second strongest fixation, and the AP group was the biomechanically weakest among these 3 fixation techniques. The closed-loop double endobutton technique was found biomechanically superior to anterior to posterior or posterior to anterior screw fixation techniques for posterior malleolar fracture.

Biomechanical comparison of four different posterior malleolus fixation techniques: A finite element analysis

PURPOSE

The objective of this study was to compare the biomechanical behavior of four fixation methods for posterior malleolar fracture (PMF) by finite element analysis (FEM).

METHODS

Four internal fixation techniques used for fixation of PMF were assessed by FEM - a computational study: posterior one-third tubular 3.5 mm buttress plate (PP) with one screw (PP 1 screw), PP with two screws (PP 2 screws), two cannulated 3.5 mm lag screws in the antero-posterior (AP) direction (AP lag screws), and two postero-anterior (PA) cannulated 3.5 mm lag screws (PA lag screws). PMF with 30% and 50% fragment sizes were simulated through computational processing reconstructed from computed tomography (CT). The simulated loads of 700 N and 1500 N were applied to the proximal tibial end. The FEM evaluated the total and localized displacements of the PMF. For the analysis of stresses, the variables maximum principal (traction) and minimum principal (compression) were used. For the metallic implants, the equivalent von Mises stress (VMS) was used.

RESULTS

PA lag screw showed the lowest values for total and localized displacement, minimum and maximum total stress, and VMS in both physiological conditions and sizes of posterior malleolus involvement. The localized displacement was statistically lower for lag screws compared to PP techniques at 700 N (p < 0.05) and 1200 N (p < 0.05). The maximum total stress was statistically lower for PA lag screws compared to PP 1 fixation with 700 N (p = 0.03) and 1200 N (p = 0.039).

CONCLUSION

PA lag screws yield better results in terms of total and localized displacement, minimum and maximum total stress, and VMS in both physiological conditions and sizes of posterior malleolus involvement. These results demonstrate that PA lag screws are biomechanically the most efficient technique for the fixation of PMF.

Isolated Posterior Malleolar Fracture: A Case Report of a Rare Presentation With Narrative Review of Literature

The isolated posterior malleolar fracture is a rare case. An innocuous injury may have associated ligamentous disruption. The fracture classification and treatment protocol are not well-defined. A missed injury results in poor functional outcomes.

A 28-year-old male sustained a twisting injury to his left ankle. The radiograph revealed an isolated posterior malleolar fracture. A computerized tomographic examination suggested talus lateralization and deltoid ligament injury. Surgical fixation with a syndesmotic screw was done. Post-operative delayed weight-bearing was allowed. At a one-year follow-up, there was painless weight-bearing and independent mobilization.

The posterior malleolus significantly contributes to ankle stability. The estimation of fragment size may be an erroneous guiding factor for surgical fixation. Recent literature suggests that syndesmotic stability, residual talus subluxation, joint congruence, and fibular notch involvement are more significant factors for risk assessment and to guide the management of posterior malleolar fracture.

The isolated posterior malleolar fracture presents rarely. They should be evaluated by tomographic evaluation and an unstable injury should be surgically managed.