Overtightening of the ankle syndesmosis: is it really possible?

Revision of malunited ankle fractures

Malunion of an ankle fracture can lead to considerable pain and loss of function. Restoration of the normal anatomical alignments can restore function and minimize the onset of degeneration that will lead to severe arthrosis requiring an arthrodesis. This article outlines common causes of ankle malunion and treatment options.

An augmented fixation method for distal fibular fractures in elderly patients: a biomechanical evaluation

This biomechanical investigation compared two fixation techniques for distal fibular fractures. Elderly cadaver lower extremities with simulated fibula fractures underwent fixation either with a plate and intramedullary Kirschner wires (K-wires) with or without the addition of three screws inserted through the four cortices of the fibula and the tibia. The specimens were axially loaded to body weight on a materials testing machine, and the supinated foot was externally rotated to failure. Displacement at the fracture site was monitored with an extensometer. Comparing the augmented technique with the technique without additional screws, mean stiffness was 460 +/- 100 and 320 +/- 200 N-mm/deg, strength at failure was 31 +/- 10 and 19 +/- 7 N-m, strength at 30 degrees external rotation was 15 +/- 5 and 10 +/- 6 N-m, and axial deformation was 0.04 +/- 0.06 mm and 0.10 +/- 0.04 mm, respectively. All differences were statistically significant.

Ankle fractures resulting from rotational injuries

Ankle fractures are among the most common skeletal injuries; selection of an optimal management method depends on ankle stability. Stable fractures (eg, isolated lateral malleolar) generally are managed nonsurgically; unstable fractures (eg, bimalleolar, bimalleolar equivalent) usually are managed with open reduction and internal fixation. Stress radiographs may aid in the management of incomplete deltoid injury in which there is medial swelling and tenderness without radiographic talar shift. A posterior malleolar fracture should be reduced and stabilized if it comprises >30% of the articular surface and remains displaced after fibular stabilization. Ankle fractures with syndesmotic injury have additional tibiofibular instability that can be controlled by screw fixation. However, the choice between metal and bioabsorbable screws, screw size, number of cortices fixed, and indications for screw removal remain controversial. Conditions such as diabetes or advanced age are no longer contraindications to usual management recommendations.

Suture-endobutton fixation of ankle tibio-fibular diastasis: a cadaver study

Suture-Endobutton fixation is proposed as a minimally invasive, flexible fixation of ankle tibio-fibular diastasis, which would not require routine removal. This study tested the Suture-Endobutton construct in a cadaver syndesmosis injury model and compared this against A.O. syndesmosis screw fixation. Sixteen embalmed cadaver legs were used. Phase one consisted of placing the leg in a jig, generating an external rotation torque and measuring diastasis with increasing intraosseous membrane division. Phase two then compared the Suture-Endobutton construct vs. single four-cortex 4.5 mm A.O. screw fixation. Diastasis increased significantly with increasing intraosseous membrane division (p<0.001). No significant differences were seen in the mean rate of failure between the Suture-Endobutton and A.O. screw fixation. However, the Suture-Endobutton did give a significantly more consistent performance; the distribution of standard deviations for A.O. screw fixation was 0.64 mm higher than that for the Endobutton (95% C.I. 0.46 to 0.84). These results show that Suture-Endobutton fixation at least equals the performance of screw fixation and encourages clinical trials in ankle injuries with a syndesmosis diastasis.

Syndesmosis injuries: acute, chronic, new techniques for failed management

A syndesmotic injury occurs through tearing, rupture, or bony avulsion of the syndesmotic ligament complex. The syndesmotic ligament complex consists of the anterior tibiofibular, the posterior tibiofibular, the transverse tibiofibular and the interosseous ligaments. Without these ligamentous restraints the distal tibiofibular joint (DTFJ) widens and can result in an asymmetric ankle mortise. Many cadaveric studies have been performed to evaluate the force required and amount of DTFJ displacement with progressive sectioning of the syndesmotic ligaments.

Treatment of syndesmotic disruptions of the ankle with bioabsorbable screw fixation

BACKGROUND

Bioabsorbable implants have restricted indications because of their unique biochemical properties and their inferior biomechanical properties compared with those of conventional metallic implants. The purpose of this prospective study was to assess the efficacy of screws made of polylevolactic acid (PLLA) in the treatment of syndesmotic disruptions associated with ankle fractures and fracture-dislocations.

METHODS

Thirty-three consecutive patients with a syndesmotic disruption were managed with standard metallic plate-and-screw fixation of the malleolar fracture and with 4.5-mm polylevolactic acid screws, with purchase in four cortices, for fixation of the syndesmosis. Intraoperative radiographs confirmed reduction of the syndesmosis, and all of the patients were managed with a non-weight-bearing plaster splint or brace for six weeks. Clinical and radiographic assessment and functional evaluation with use of the Olerud-Molander scoring system were performed at the time of follow-up.

RESULTS

Ten patients were lost to follow-up prior to the twenty-four-month evaluation, leaving twenty-three patients with an average duration of follow-up of thirty-four months (range, twenty-four to forty-three months). All of the malleolar fractures healed in an anatomical position at an average of three months, and no postoperative displacement of the syndesmosis or widening of the medial clear space was detectable on radiographs. No episodes of osteolysis or late inflammation secondary to the hydrolyzed polylactide occurred. Nineteen patients (83%) had an excellent result, and four patients (17%) had a good result. All twenty-three patients returned to their preinjury level of work and activities of daily living. No patient had malunion, nonunion, loss of reduction, or complications attributable to the biomechanical or biochemical properties of the implants.

CONCLUSIONS

Polylevolactic acid screws are effective in stabilizing disruption of the syndesmosis during healing of unstable ankle fractures. In this small series, the bioabsorbable screw was well tolerated, and there was no need for a second operation to remove it.