Dynamic vs static external fixation of distal radial fractures: A randomized study

Development of a testing device for external wrist bridging dynamic fixators used for distal radius fractures

BACKGROUND

Stabilization of extra-articular distal radius fractures by wrist joint bridging (WB) dynamic fixation allows for early motion of the wrist, but relies on exact positioning of the device. In fact, physiological movement appeared to be compromised with even distinctly aberrant positioning of such device. To investigate this issue in more detail, we developed an in-vitro testing apparatus suitable for assessing the forces required for flexion and extension of the wrist.

METHODS

The experimental set-up enables the transmission of the translational movement of the traverse of a universal testing machine into the main physiological movement (flexion and extension) of the wrist. An external WB dynamic fixator was assembled to an artificial saw bone wrist model prior and after performing a wedge-shaped osteotomy on the distal radius about 1.5 cm proximal to the joint line, i.e. generation of a fracture model. The functionality of the fixator was evaluated under either condition and the effect of misalignment of the external WB dynamic fixator was quantified by purposeful violation of the manufacture's instructions. Results were statistically analyzed using the generalized linear mixed model.

FINDINGS

Significantly higher loading was noted as the degree of misalignment increased. The normalized force was significantly higher at a misalignment of 20° compared to 10° (10°: 4.13; 20°: 6.93, P < 0.001).

INTERPRETATION

The proposed set-up turned out to allow highly reproducible and sensitive recording of the reaction forces during flexion and extension of the wrist and thus is feasible for the evaluation and comparison of different external WB devices.

The combined effects of dynamization time and degree on bone healing

Dynamization, increasing the interfragmentary movement (IFM) by reducing the fixation stiffness from a rigid to a more flexible condition, is widely used clinically to promote fracture healing. However, it remains unknown how dynamization degree (relative change in fixation stiffness/IFM from a rigid to a flexible fixation) affects bone healing at various stages. To address this issue, we used a fuzzy logic-based mechano-regulated tissue differentiation algorithm on published experimental data from a sheep osteotomy healing model. We applied a varied degree of dynamization, from 0 (fully rigid fixation) to 0.9 (90% reduction in stiffness relative to the rigid fixation) after 1, 2, 3, and 4 weeks of osteotomy (R1wF, R2wF, R3wF, and R4wF) and computationally evaluated bone regeneration and biomechanical integrity over the healing process of 8 weeks. Compared with the constant rigid fixation, early dynamization (R1wF and R2wF) led to delays in bone bridging and biomechanical recovery of the osteotomized bone. However, the effect of early dynamization on healing was dependent of the degree of dynamization. Specifically, a higher dynamization degree (e.g., 0.9 for R1wF) led to a prolonged delay in bone bridging and largely unrecovered bending stiffness (48% relative to the intact bone), whereas a moderate degree of dynamization (e.g., 0.5 or 0.7) significantly enhanced bone formation and biomechanical properties of the osteotomized bone. These results suggest that dynamization degree and timing interactively affect the healing process. A combination of early dynamization with a moderate degree could enhance the ultimate biomechanical recovery of the fractured bone.

What Is the Relative Effectiveness of the Various Surgical Treatment Options for Distal Radius Fractures? A Systematic Review and Network Meta-analysis of Randomized Controlled Trials

BACKGROUND

Many acceptable treatment options exist for distal radius fractures (DRFs); however, a simultaneous comparison of all methods is difficult using conventional study designs.

QUESTIONS/PURPOSES

We performed a network meta-analysis of randomized controlled trials (RCTs) on DRF treatment to answer the following questions: Compared with nonoperative treatment, (1) which intervention is associated with the best 1-year functional outcome? (2) Which intervention is associated with the lowest risk of overall complications? (3) Which intervention is associated with the lowest risk of complications requiring operation?

METHODS

Ten databases were searched from inception to July 25, 2019. Search and analysis reporting adhered to Preferred Reporting Items for Systematic Reviews and Meta-analyses guidelines. Included studies were English-language RCTs that assessed at least one surgical treatment arm for adult patients with displaced DRFs, with less than 20% loss to follow-up. We excluded RCTs reporting on patients with open fractures, extensive bone loss, or ipsilateral upper extremity polytrauma. Seventy RCTs (n = 4789 patients) were included. Treatments compared were the volar locking plate, bridging external fixation, nonbridging external fixation, dynamic external fixation, percutaneous pinning, intramedullary fixation, dorsal plating, fragment-specific plating, and nonoperative treatment. Subgroup analyses were conducted for intraarticular fractures, extraarticular fractures, and patients with an average age greater than 60 years. Mean (range) patient age was 59 years (56 to 63) and was similar across all treatment groups except for dynamic external fixation (44 years) and fragment-specific plating (47 years). Distribution of intraarticular and extraarticular fractures was approximately equal among the treatment groups other than that for intramedullary fixation (73% extraarticular), fragment-specific plating (66% intraarticular) [13, 70], and dorsal plating (100% intraarticular). Outcomes were the DASH score at 1 year, total complications, and reoperation. The minimum clinically important different (MCID) for the DASH score was set at 10 points. The analysis was performed using Bayesian methodology with random-effects models. Rank orders were generated using surface under the cumulative ranking curve values. Evidence quality was assessed using Grades of Recommendation, Assessment, Development and Evaluation (GRADE) methodology. Most studies had a low risk of bias due to randomization and low rates of incomplete follow-up, unclear risk of bias due to selective reporting, and high risk of bias due to lack of patient and assessor blinding. Studies assessing bridging external fixation and/or nonoperative treatment arms had a higher overall risk of bias while studies with volar plating and/or percutaneous pinning treatment arms had a lower risk of bias.

RESULTS

Across all patients, there were no clinically important differences in terms of the DASH score at 1 year; although differences were found, all were less than the MCID of 10 points. Volar plating was ranked the highest for DASH score at 1 year (mean difference -7.34 [95% credible interval -11 to -3.7) while intramedullary fixation, with low-quality evidence, also showed improvement in DASH score (mean difference -7.75 [95% CI -14.6 to -0.56]). The subgroup analysis revealed that only locked volar plating was favored over nonoperative treatment for patients older than 60 years of age (mean difference -6.4 [95% CI -11 to -2.1]) and for those with intraarticular fractures (mean difference -8.4 [95% CI -15 to -2.0]). However, its clinical importance was uncertain as the MCID was not met. Among all patients, intramedullary fixation (odds ratio 0.09 [95% CI 0.02 to 0.84]) and locked volar plating (OR 0.14 [95% CI 0.05 to 0.39]) were associated with a lower complication risk compared with nonoperative treatment. For intraarticular fractures, volar plating was the only treatment associated with a lower risk of complications than nonoperative treatment (OR 0.021 [95% CI < 0.01 to 0.50]). For extraarticular fractures, only nonbridging external fixation was associated with a lower risk of complications than nonoperative treatment (OR 0.011 [95% CI < 0.01 to 0.65]), although the quality of evidence was low. Among all patients, the risk of complications requiring operation was lower with intramedullary fixation (OR 0.06 [95% CI < 0.01 to 0.85) than with nonoperative treatment, but no treatment was favored over nonoperative treatment when analyzed by subgroups.

CONCLUSION

We found no clinically important differences favoring any surgical treatment option with respect to 1-year functional outcome. However, relative to the other options, volar plating was associated with a lower complication risk, particularly in patients with intraarticular fractures, while nonbridging external fixation was associated with a lower complication risk in patients with extraarticular fractures. For patients older than 60 years of age, nonoperative treatment may still be the preferred option because there is no reliable evidence showing a consistent decrease in complications or complications requiring operation among the other treatment options. Particularly in this age group, the decision to expose patients to even a single surgery should be made with caution.

LEVEL OF EVIDENCE

Level I, therapeutic study.

Controversies in Fracture Healing: Early Versus Late Dynamization

Dynamization of fracture fixation constructs provides early rigidity for primary bone healing and late motion for secondary healing. A review of laboratory, animal, and clinical studies investigating the impact, and optimal timing, of dynamization is limited by lack of standardization across studies. However, in animal models, dynamization improves histologic and biomechanical properties compared with statically rigid or flexible controls. In animals, dynamization at 3 to 4 weeks showed improved histologic results. In clinical studies, it showed faster, stronger, and stiffer bone healing. Clinical success dynamizing external fixators and intramedullary nails suggests a role for late dynamization in other fixation types, such as bridge plating. [Orthopedics. 2020;43(3):e125-e133.].

Immediate weightbearing after Lapidus arthrodesis with external fixation

A common surgical treatment of severe hallux abductovalgus deformity with coincident first ray hypermobility is metatarsal-cuneiform fusion or Lapidus procedure. The aim of the present study was to illustrate a reliable and novel method of fixation for Lapidus fusion using an external fixation device through a retrospective cohort investigation of consecutive patients. Twenty Lapidus fusions were performed in 19 patients, including 17 females (89.47%) and 2 males (10.53%). The mean age at surgery was 41 (range 20 to 64) years. The patients were evaluated clinically and radiographically pre- and postoperatively. The mean duration in the fixator was 12 (range 3 to 34) weeks. The mean interval to radiographic union was 9.2 (range 4.7 to 30.7) weeks in 18 of 20 feet (90%) and 2 (10%) were designated as nonunion. The mean follow-up period was 37 (range 5.6 to 211.1) weeks. The most common complication was pin tract infection in 5 patients (6 feet) and was treated with oral antibiotics; only 1 foot required early hardware removal. According to the visual analog scale, the mean patient pain score decreased significantly from 8.2 ± 2.7 to 0.83 ± 0.98 postoperatively (p < .001). Our results highlight that immediate weightbearing after Lapidus fusion with external fixation is a viable treatment option for the correction of severe hallux abductovalgus with associated hypermobility.