Overtightening of the ankle syndesmosis: is it really possible?

Lagged Syndesmotic Fixation: Our Clinical Experience

Ankle fractures are very common, and although algorithms are in place for osseous management, consensus has not been reached regarding treatment of associated ligamentous injuries. Although tibiofibular syndesmotic stabilization can be done using different forms of fixation, the biomedical literature has long emphasized the risk of long-term restriction of ankle mobility with the use of lagged transfixation. However, when reduction cannot be maintained with positional fixation, we found that lagging the syndesmotic screw helped to maintain the reduction without causing functional restriction. In this report, we describe our experience with patients who had undergone lagged tibiofibular transfixation and were available for short- to intermediate-term follow-up to assess ankle function. A total of 31 patients (32.63% of 95 consecutive patients) were available at a mean of 34.87 (range 18 to 52) months to complete the American Orthopedic Foot and Ankle Society ankle-hindfoot questionnaire. The mean score was 88.38 (range 42 to 100) points at a mean follow-up interval of 34.87 (range 18 to 52) months. Of 31 patients, 19 had an AOFAS score of 90 points, 9 an AOFAS score of 80 to 89 points, 2 an AOFAS score of 60 to 69 points, and 1 an AOFAS score of <60 points. Because all syndesmotic screws were placed using the lag technique, unrestricted motion compared with the uninjured limb was used as the endpoint. All subjects had unrestricted motion compared with the uninjured limb, refuting the assertion that lagged syndesmotic screw fixation confers more restriction in ankle kinematics than positional syndesmotic fixation.

A computed tomography evaluation of two hundred normal ankles, to ascertain what anatomical landmarks to use when compressing or placing an ankle syndesmosis screw

Classical AO teaching recommends that a syndesmosis screw should be inserted at 25-30 degrees to the coronal plane of the ankle. Accurately judging the 25/30 degree angle can be difficult, resulting in poor operative reduction of syndesmosis injuries. The CT scans of 200 normal ankles were retrospectively examined. The centroid of the fibula and tibia in the axial plane 15mm proximal to the talar dome was calculated. A force vector between the centroid of the fibula and the tibia in the axial plane should not displace the fibula relative to the tibia when surfaces are parallel. Therefore, a line connecting the two centroids was postulated to be the ideal syndesmosis line. This line was shown to pass through the fibula within 2.5mm of the lateral cortical apex of the fibula and the anterior half of the medial malleolus in 100% of the ankles studied. The results support the concept that in the operatively reduced syndesmosis, the anterior half of the medial malleolus can be used as a reliable guide for aiming the syndesmosis drill hole, provided that the fibular entry point is at/or adjacent to the lateral fibular apex. The screw should also remain parallel to the tibial plafond in the coronal plane.

Optimal management of ankle syndesmosis injuries

Syndesmosis injuries occur when there is a disruption of the distal attachment of the tibia and fibula. These injuries occur commonly (up to 18% of ankle sprains), and the incidence increases in the setting of athletic activity. Recognition of these injuries is key to preventing long-term morbidity. Diagnosis and treatment of these injuries requires a thorough understanding of the normal anatomy and the role it plays in the stability of the ankle. A complete history and physical examination is of paramount importance. Patients usually experience an external rotation mechanism of injury. Key physical exam features include detailed documentation about areas of focal tenderness (syndesmosis and deltoid) and provocative maneuvers such as the external rotation stress test. Imaging workup in all cases should consist of radiographs with the physiologic stress of weight bearing. If these images are inconclusive, then further imaging with external rotation stress testing or magnetic resonance imaging are warranted. Nonoperative treatment is appropriate for stable injuries. Unstable injuries should be treated operatively. This consists of stabilizing the syndesmosis with either trans-syndesmotic screw or tightrope fixation. In the setting of a concomitant Weber B or C fracture, the fibula is anatomically reduced and stabilized with a standard plate and screw construct. Proximal fibular fractures, as seen in the Maisonneuve fracture pattern, are not repaired operatively. Recent interest is moving toward repair of the deltoid ligament, which may provide increased stability, especially in rehabilitation protocols that involve early weight bearing. Rehabilitation is focused on allowing patients to return to their pre-injury activities as quickly and safely as possible. Protocols initially focus on controlling swelling and recovery from surgery. The protocols then progress to restoration of motion, early protected weight bearing, restoration of strength, and eventually a functional progression back to desired activities.

Novel flexible suture fixation for the distal tibiofibular syndesmotic joint injury: a cadaveric biomechanical model

Syndesmotic injuries of the ankle commonly occur by an external rotation force applied to the ankle joint. Ten fresh-frozen lower extremities from cadavers were used. A specially designed apparatus was used to stabilize the specimen and rotate the ankle joint from internally rotated 25° to externally rotated 35° at a rate of 6°/s for 10 cycles. Two stages were tested (stage I, specimens intact; and stage II, simulated pronation external rotation type injury with fixation). Group 1 was fixed with a novel suture construct across the syndesmotic joint, and group 2 was fixed with a single metallic screw. The torque, rotational angle, and 3-dimensional syndesmotic diastasis readings were recorded. Three-dimensional tibiofibular diastasis was identified. The fibula of the intact specimens displaced an average of 8.6 ± 1.7, 2.4 ± 1.0, and 1.4 ± 1.0 mm in the anterior, lateral, and superior direction, respectively, when the foot was externally rotated 35°. The sectioning of the syndesmostic ligaments and deltoid ligament resulted in a significant decrease in syndesmotic diastasis and foot torsional force (p < .05). The ligament-sectioned specimen lost 57% (externally rotated) and 17% (internally rotated) torsional strength compared with the intact specimen. Groups 1 and 2 provided similar biomechanical stability in this cadaveric model of a syndesmosis deficiency.

Injuries to the ankle syndesmosis

➤ Despite being common, syndesmotic injuries are challenging to diagnose and treat.➤ Anatomic reduction of the ankle syndesmosis is critical for good clinical outcomes.➤ Intraoperative three-dimensional radiography and direct syndesmotic visualization can improve rates of anatomic reduction.➤ The so-called gold-standard syndesmotic screw fixation is being brought increasingly into question as new fixation techniques emerge.➤ Syndesmotic screw removal remains controversial, but may allow spontaneous correction of malreductions.

Analysis of the stress and displacement distribution of inferior tibiofibular syndesmosis injuries repaired with screw fixation: a finite element study

BACKGROUND

Studies of syndesmosis injuries have concentrated on cadaver models. However, they are unable to obtain exact data regarding the stress and displacement distribution of various tissues, and it is difficult to compare models. We investigated the biomechanical effects of inferior tibiofibular syndesmosis injuries (ITSIs) and screw fixation on the ankle using the finite element (FE) method.

METHODOLOGY/PRINCIPAL FINDINGS

A three-dimensional model of a healthy ankle complex was developed using computed tomography (CT) images. We established models of an ITSI and of screw fixation at the plane 2.5 cm above and parallel to the tibiotalar joint surface of the injured syndesmosis. Simulated loads were applied under three conditions: neutral position with single-foot standing and internal and external rotation of the ankle. ITSI reduced contact forces between the talus and fibula, helped periarticular ankle ligaments withstand more load-resisting movement, and increased the magnitude of displacement at the lower extreme of the tibia and fibula. ITSI fixation with a syndesmotic screw reduced contact forces in all joints, decreased the magnitude of displacement at the lower extreme of the tibia and fibula, and increased crural interosseous membrane stress.

CONCLUSIONS/SIGNIFICANCE

Severe syndesmosis injuries cause stress and displacement distribution of the ankle to change multidirectional ankle instability and should be treated by internal fixation. Though the transverse syndesmotic screw effectively stabilizes syndesmotic diastasis, it also changes stress distribution around the ankle and decreases the joint's range of motion (ROM). Therefore, fixation should not be performed for a long period of time because it is not physiologically suitable for the ankle joint.

Syndesmosis injuries

Traumatic injuries to the distal tibiofibular syndesmosis commonly result from high-energy ankle injuries. They can occur as isolated ligamentous injuries and can be associated with ankle fractures. Syndesmotic injuries can create a diagnostic and therapeutic challenge for musculoskeletal physicians. Recent literature has added considerably to the body of knowledge pertaining to injury mechanics and treatment outcomes, but there remain a number of controversies regarding diagnostic tests, implants, techniques, and postoperative protocols. Use of the novel suture button device has increased in recent years and shows some promise in clinical and cadaveric studies. This article contains a review of syndesmosis injuries, including anatomy and biomechanics, diagnosis, classification, and treatment options.

Syndesmosis injuries of the ankle

Ankle syndesmosis injuries are relatively frequent in sports, especially skiing, ice hockey, and soccer, accounting for 1 %-18 % of all ankle sprains. The evolution is unpredictable: When missed, repeated episodes of ankle instability may predispose to early degenerative changes, and frank osteoarthritis may ensue. Diagnosis is clinical and radiological, but arthroscopy may provide a definitive response, allowing one to address secondary injuries to bone and cartilage. Obvious diastasis needs to be reduced and fixed operatively, whereas less severe injuries are controversial. Nonoperative treatment may be beneficial, but it entails long rehabilitation. In professional athletes, more aggressive surgical treatment is warranted.

Does the Arthrex TightRope® provide maintenance of the distal tibiofibular syndesmosis? A 2-year follow-up of 64 TightRopes® in 37 patients

Syndesmotic diastasis can occur as an isolated injury or with concomitant fractures. A review of 37 patients with 64 TightRopes® for syndesmotic repair was performed, with a mean follow-up of 23.6 ± 4.3 months, from 2007 to 2011. The patients' mean age was 40.67 (range 14 to 87) years. The mean initial measurements were as follows: tibiofibular clear space (TFCS) = 4.1 ± 1.1 mm, tibiofibular overlap (TFO) = 7.2 ± 2.7 mm, and medial clear space (MCS) = 2.9 ± 0.5 mm. The mean final measurements were as follows: TFCS = 4.2 ± 1.3 mm, TFO = 7.4 2.8 mm, and MCS = 3.0 0.5 mm. The calculated measurable difference from the initial to final TFCS, TFO, and MCS was significantly less than the maximum threshold for allowable widening of the syndesmosis: TFCS, p < .001; TFO, p < .002; and MCS, p < .001. Complications occurred in 10 patients; 7 (19%) experienced knot irritation and 3 (8%) developed an infection. The mean interval to weightbearing was 33.2 ± 12.7 days. The mean postoperative American Orthopaedic Foot and Ankle Society score was 97 (range 90 to 100). Of 64 suture endobuttons, 4 (6.25%) required removal. The fracture types were as follows: 3 (8%) isolated syndesmotic injuries, 9 (24%) trimalleolar fractures, 10 (27%) bimalleolar fractures, 7 (18%) Weber B fractures, 3 (8%) Weber C fractures, 1 (3%) Salter Harris type 3 fracture, and 4 (11%) Maisonneuve fractures. TightRope® fixation was advantageous because it rarely required removal, allowed for physiologic motion of the syndesmosis, and resulted in an early return to weightbearing. In addition, we have concluded that the TightRope® provides long-term stability of the ankle mortise, which was confirmed by the radiographic criteria and excellent American Orthopaedic Foot and Ankle Society scores.

Syndesmosis and deltoid ligament injuries in the athlete

PURPOSE

Injury to the syndesmosis and deltoid ligament is less common than lateral ligament trauma but can lead to significant time away from sport and prolonged rehabilitation. This literature review will discuss both syndesmotic and deltoid ligament injuries without fracture in the professional athlete.

METHODS

A narrative review was performed using PUBMED, OVID, MEDLINE and EMBASE using the key words syndesmosis, injury, deltoid, ankle ligaments, and athlete. Articles related to the topic were included and reviewed.

RESULTS

The incidence of syndesmotic injury ranges from 1 to 18 % of ankle sprains. This may be underreported and is an often missed injury as clinical examination is generally not specific. Both MRI and ultrasonography have high sensitivities and specificities in diagnosing injury. Arthroscopy may confirm the diagnosis, and associated intra-articular pathology can be treated at the same time as surgical stabilization. Significant deltoid ligament injury in isolation is rare, there is usually associated trauma. Major disruption of both deep and superficial parts can lead to ankle dysfunction. Repair of the ligament following ankle fracture is not necessary, but there is little literature to guide the management of deltoid ruptures in isolation or in association with syndesmotic and lateral ligament injuries in the professional athlete.

CONCLUSION

Management of syndesmotic injury is determined by the grade and associated injury around the ankle. Grade I injuries are treated non-surgically in a boot with a period of non-weight bearing. Treatment of Grade II and III injuries is controversial with little literature to guide management. Athletes may return to training and play sooner if the syndesmosis is surgically stabilized. For deltoid ligament injury, grade I and II sprains should be treated non-operatively. Unstable grade III injuries with associated injury to the lateral ligaments or the syndesmosis may benefit from operative repair.

Management of syndesmosis injuries in the elite athlete

This article reviews the basics and evidence base thus far on syndesmosis injuries, focusing on its management in the elite sporting population. A syndesmosis injury or "high ankle sprain" is a significant injury, especially in the elite athlete. Among all ankle sprains, the syndesmotic injury is most predictive of persistent symptoms in the athletic population. Late diagnosis of unstable syndesmosis injuries leads to a poor outcome and delayed return to sports. A high index of suspicion and an understanding of the mechanism of injury is required to ensure an early diagnosis. Incomplete/inaccurate reduction leads to a poor outcome.

Complications of distal tibiofibular syndesmotic screw stabilization: analysis of 236 patients

The objective of the present study was to evaluate our complications of screw stabilization and to formulate recommendations for clinical practice. Using a prospectively collected fracture database, the data from 236 consecutive adult patients were analyzed who had undergone syndesmotic screw stabilization from January 1979 to December 2000 at our level I academic trauma center. We observed 16 complications in 15 patients. The average patient age was 37.5 years. Of the 15 patients, 1 had a Weber B fracture and 14 had a Weber C ankle fracture. These complications included tibiofibular synostosis in 11 patients, screw breakage in 4 patients, and late diastasis in 1 patient. All breakages occurred in Weber C fractures. In particular, the 3.5-mm screws, penetrating both tibial cortices, tended to break. Synostosis was observed in 3% of the Weber B fractures and 5% of the Weber C fractures. Weightbearing in a plaster cast during syndesmotic screw stabilization is a safe postoperative treatment. We suggest that the use of 3.5-mm screws and screws penetrating 2 tibial cortices have a greater risk of breakage. Because of the low complication rate and more difficult treatment of late syndesmotic diastasis, a syndesmotic screw should be placed when in doubt of the indication.

Stability-based classification for ankle fracture management and the syndesmosis injury in ankle fractures due to a supination external rotation mechanism of injury

The aim of this thesis was to confirm the utility of stability-based ankle fracture classification in choosing between non-operative and operative treatment of ankle fractures, to determine how many ankle fractures are amenable to non-operative treatment, to assess the roles of the exploration and anatomical repair of the AITFL in the outcome of patients with SER ankle fractures, to establish the sensitivities, specificities and interobserver reliabilities of the hook and intraoperative stress tests for diagnosing syndesmosis instability in SER ankle fractures, and to determine whether transfixation of unstable syndesmosis is necessary in SER ankle fractures. The utility of stability based fracture classification to choose between non-operative and operative treatment was assessed in a retrospective study (1) of 253 ankle fractures in skeletally mature patients, 160 of whom were included in the study to obtain an epidemiological profile in a population of 130,000. Outcome was assessed after a minimum follow-up of two years. The role of AITFL repairs was assessed in a retrospective study (2) of 288 patients with Lauge-Hansen SE4 ankle fractures; the AITFL was explored and repaired in one group (n=165), and a similar operative method was used but the AITFL was not explored in another group (n=123). Outcome was measured with a minimum follow-up of two years. Interobserver reliability of clinical syndesomosis tests (study 3) and the role of syndesmosis transfixation (study 4) were assessed in a prospective study of 140 patients with Lauge-Hansen SE4 ankle fractures. The stability of the distal tibiofibular joint was evaluated by the hook and ER stress tests. Clinical tests were carried out by the main surgeon and assistant, separately, after which a 7.5-Nm standardized ER stress test for both ankles was performed; if it was positive, the patient was randomized to either syndesmosis transfixation (13 patients) or no fixation (11 patients) treatment groups. The sensitivity and specificity of both clinical tests were calculated using the standard 7.5-Nm external rotation stress test as reference. Outcome was assessed after a minimum of one year of follow-up. Olerud-Molander (OM) scoring system, RAND 36-Item Health Survey, and VAS to measure pain and function were used as outcome measures in all studies. In study 1, 85 (53%) fractures were treated operatively using the stability based fracture classification. Non-operatively treated patients reported less pain and better OM (good or excellent 89% vs. 71%) and VAS functional scores compared to operatively treated patients although they experienced more displacement of the distal fibula (0 mm 30% vs. 69%; 0-2 mm 65% vs. 25%) after treatment. No non-operatively treated patients required operative fracture fixation during follow-up. In study 2, AITFL exploration and suture lead to equal functional outcome (OM mean, 77 vs. 73) to no exploration or fixation. In study 3, the hook test had a sensitivity of 0.25 and a specificity of 0.98. The external rotation stress test had a sensitivity of 0.58 and a specificity of 0.9. Both tests had excellent interobserver reliability; the agreement was 99% for the hook test and 98% for the stress test. There was no statistically significant difference in functional scores (OM mean, 79.6 vs. 83.6) or pain between syndesmosis transfixation and no fixation groups (Study 4). Our results suggest that a simple stability-based fracture classification is useful in choosing between non-operative and operative treatment of ankle fractures; approximately half of the ankle fractures can be treated non-operatively with success. Our observations also suggest that relevant syndesmosis injuries are rare in ankle fractures due to an SER mechanism of injury. According to our research, syndesmotic repair or fixation in SER ankle fracture has no influence on functional outcome or pain after minimum one year compared with no fixation.

Flexible stabilization of the distal tibiofibular syndesmosis: clinical and biomechanical considerations: a review of the literature

Syndesmotic rupture is present in 10 % of ankle fractures and must be recognized and treated to prevent late complications. The method of fixation is classically rigid fixation with one or two screws. Knowledge of the biomechanics of the syndesmosis has led to the development of new dynamic implants to restore physiologic motion during walking. One of these implants is the suture-button system. The purpose of this paper is to review the orthopaedic trauma literature, both biomechanical and clinical, to present the current state of knowledge on the suture-button fixation and to put emphasis on the advantages and disadvantages of this technique. Two investigators searched the databases of Pubmed/Medline, Cochrane Clinical Trial Register and Embase independently. The search interval was from January 1980 to March 2011. The search keys comprised terms to identify articles on biomechanical and clinical issues of flexible fixation of syndesmotic ruptures. Ninety-nine publications met the search criteria. After filtering using the exclusion criteria, 11 articles (five biomechanical and six clinical) were available for review. The biomechanical studies involved 90 cadaveric ankles. The suture-button demonstrated good resistance to axial and rotational loads (equivalent to screws) and resistance to failure. Physiologic motion of the syndesmosis was restored in all directions. The clinical studies (149 ankles) demonstrated good functional results using the AOFAS score, indicating faster rehabilitation with flexible fixation than with screws. There were few complications. Preliminary results from the current literature support the use of suture-button fixation for syndesmotic ruptures. This method seems secure and safe. As there is no strong evidence for its use, prospective randomized controlled trials to compare the suture-button to the screw fixation for ankle syndesmotic ruptures are required.

Compression screw fixation of the syndesmosis

BACKGROUND

Screw fixation of syndesmotic injuries facilitates ligament healing and restoration of ankle stability, but little information regarding screw performance is available. This study quantified the reduction obtained with three common 2-screw configurations using different methods of reduction and novel methods of subsequently provoking and measuring diastasis.

METHODS

Seven fresh-frozen lower extremities were subjected to 100 N medial and lateral tibia loads with the talus restrained. Tibia displacement, indicative of ankle clear space, was recorded. The syndesmosis and distal interosseous ligament were disrupted and measurements repeated. A pressure sensor was inserted into the syndesmosis and three 2-screw fixation methods were evaluated in each specimen: 3.5-mm screws engaging both fibula cortices and the lateral tibial cortex, inserted while using a clamp to achieve syndesmosis reduction; 3.5-mm lag screws engaging both tibia cortices; and 4.5-mm lag screws engaging both tibia cortices. One thousand 100 N medial and lateral loads were applied and clear space and syndesmosis compression were quantified every 100 cycles.

RESULTS

Normal ankle clear space averaged 1.98 mm and increased to 3.02 mm after syndesmosis disruption. Fixation decreased the clear space to 1.36 mm, 1.22 mm, and 1.19 mm for the 3.5-mm tricortical, 3.5-mm lag, and 4.5-mm lag screws, respectively, remaining steady throughout cyclic loading. Syndesmosis compression dropped markedly from 61N to 23 N on clamp release after tricortical screw insertion. The 3.5-mm and 4.5-mm lag screws exerted 112 N and 131 N, respectively, after insertion, and maintained compression several-fold greater than the tricortical screws during cyclic loading. No difference was demonstrable between the two lag screw sizes.

CONCLUSION

While all screw configurations successfully reduced ankle clear space, syndesmosis reduction was more effectively maintained by lag screws than by tricortical screws inserted with clamp reduction. The transient nature of compression achieved by the reduction clamp suggests that use of lag screws for this application may more reliably maintain syndesmosis reduction in vivo.

CLINICAL RELEVANCE

Optimizing reduction of syndesmosis injuries is critical for favorable outcomes. This study offers concrete information on screw performance in this application.

An anatomical way of treating ankle syndesmotic injuries

Treatment of tibiofibular syndesmotic ankle injury remains controversial in regard to the best method, although surgeons agree that the goal of treatment is reduction and operative stabilization. Ideally, the implant should stabilize the syndesmosis and allow physiologic micromotion and early mobilization, and conventional screws are limited in this regard. We reviewed use of the Ankle TightRope(®) fixation device for repair of syndesmotic injuries. From April to September 2006, 16 patients with evidence of syndesmotic injury were treated by means of ankle fracture open reduction with internal fixation, combined with use of the Ankle TightRope(®) device for repair of the syndesmosis. The mean age of the 16 patients was 36.6 ± 16.71 (range 15 to 69) years; they were followed up for at least 2 years. Mean follow-up duration was 26 ± 3.94 (range 24 to 38) months. The mean American Orthopaedic Foot and Ankle Society score at 2-year follow-up was 86.88 ± 11.49 (range 48 to 100). The mean time to full weight-bearing was 4.5 ± 0.87 weeks. Two (12.5%) patients had postoperative superficial wound infections, each of which was treated with oral antibiotics. One (6.25%) patient had the TightRope(®) removed because of irritation from the knot. There was no failure of syndesmotic fixation, despite early weight-bearing in the postoperative phase. The results of this case series indicate that tibiofibular syndesmosis repair with the Ankle TightRope(®) yields satisfactory results.

Limitations of standard fluoroscopy in detecting rotational malreduction of the syndesmosis in an ankle fracture model

BACKGROUND

When treating ankle fractures with associated syndesmosis injury, failure to anatomically reduce the syndesmosis may lead to poor outcome. While shortening and posterior subluxation of the distal fibula are readily detected by intraoperative fluoroscopy, it is unclear how well malrotation can be assessed. The ability of fluoroscopy to detect rotational malreduction of the fibula was the subject of this study.

MATERIALS AND METHODS

Distal fibula fractures with complete syndesmotic injury were produced in ten cadaveric ankles. Two Kirschner wires were used to fix the fibula in neutral (0 degrees), 10 to 30 degrees of external rotation (ER), and 10 degrees to 30 degrees of internal rotation (IR). Using C-arm fluoroscopy tibio-fibular clear space and tibio-fibular overlap in the AP and mortise views, and posterior fibular subluxation in the lateral view were measured to assess reduction of the syndesmosis.

RESULTS

The radiographic indices were able to detect as little as 10 degrees of IR but were within their normal range in up to 30 degrees of ER. When assessing for a 2mm difference compared to the intact ankle, sensitivity of all indices were low after more than 15 degrees ER, but high and clinically useful after more than 15 degrees of IR.

CONCLUSION

Radiographic indices for syndesmosis disruption could not detect ER malreduction of the syndesmosis of up to 30 degrees.

CLINICAL RELEVANCE

In the setting of ankle fractures with syndesmosis disruption, fixing the fibula in as much as 30 degrees of external rotation may go undetected using intraoperative fluoroscopy alone.

The fate of syndesmotic screws

BACKGROUND

A standard protocol for the management of syndesmosis injuries has yet to be established. Debate persists regarding number of screws, screw diameter, number of cortices purchased, and the need for and timing of screw removal. The purpose of this study was to identify factors related to screw fixation that may lead to the ultimate failure of syndesmosis fixation defined as a loss of reduction of the syndesmosis, screw breakage, screw loosening, or widening of the medial clear space.

MATERIALS AND METHODS

A retrospective assessment of 137 consecutive patients who underwent open reduction and internal fixation of the distal tibiofibular joint at a single institution from 2004 to 2008 was performed. Clinical and radiographic data were recorded regarding problems with questionable clinical significance (number of syndesmotic screws, number of cortices, screw diameter, screw location, hardware failure) and loss of syndesmosis reduction. A series of Fisher's exact tests were used to evaluate outcomes. A p value of 0.05 defined as significant.

RESULTS

The 3.5-mm diameter screws were statistically more likely to break than 4- or 4.5-mm screws, but there was no difference in frequency of loss of reduction of the syndesmosis as a function of screw diameter; however, a power study revealed an n value of 1656 would be required to show a significant difference.

CONCLUSION

Screw diameter may have an effect on screw breakage but clinical significance of hardware failure itself is unknown including whether or not it results in a loss of reduction or failure of syndesmotic fixation.

To retain or remove the syndesmotic screw: a review of literature

INTRODUCTION

Syndesmotic positioning screws are frequently placed in unstable ankle fractures. Many facets of adequate placement techniques have been the subject of various studies. Whether or not the syndesmosis screw should be removed prior to weight-bearing is still debated. In this study, the recent literature is reviewed concerning the need for removal of the syndesmotic screw.

MATERIALS AND METHODS

A comprehensive literature search was conducted in the electronic databases of the Cochrane Library, Pubmed Medline and EMbase from January 2000 to October 2010.

RESULTS

A total of seven studies were identified in the literature. Most studies found no difference in outcome between retained or removed screws. Patients with screws that were broken, or showed loosening, had similar or improved outcome compared to patients with removed screws. Removal of the syndesmotic screws, when deemed necessary, is usually not performed before 8-12 weeks.

CONCLUSION

There is paucity in randomized controlled trials on the absolute need for removal of the syndesmotic screw. However, current literature suggests that it might be reserved for intact screws that cause hardware irritation or reduced range of motion after 4-6 months.

Plantar flexion influences radiographic measurements of the ankle mortise

BACKGROUND

The treatment of ankle fractures often depends on the integrity of the deltoid ligament. Diagnosis of a deltoid ligament tear depends on the measurement of the medial clear space. We sought to evaluate the impact of ankle plantar flexion on the medial clear space.

METHODS

Mortise radiographs were made for twenty-five healthy volunteers, with the ankle in four positions of plantar flexion (0 degrees, 15 degrees, 30 degrees, and 45 degrees). Four observers measured the medial clear space and the superior clear space on each radiograph. The mean medial clear space at 0 degrees was defined as the control, and the deviation of the medial clear space from the control value was calculated at 15 degrees, 30 degrees, and 45 degrees of plantar flexion. The ratio of the medial clear space to the superior clear space was determined on all radiographs, and ratios that were false-positive for a deltoid ligament injury were identified.

RESULTS

Fourteen male and eleven female volunteers were evaluated. The average increase in the medial clear space when ankle plantar flexion was increased from 0 degrees to 45 degrees was 0.38 mm (95% confidence interval, 0.18 to 0.58 mm). This increase was significant (p = 0.005). The average increase in the medial clear space was 0.04 mm when ankle plantar flexion was increased from 0 degrees to 15 degrees and 0.22 mm when it was increased from 0 degrees to 30 degrees. Neither of these changes was significant (p = 0.99 and 0.20). The prevalence of false-positive findings of deltoid injury based on the ratio of the medial clear space to the superior clear space increased as ankle plantar flexion increased, but this increase did not reach significance in our study group (p = 0.18).

CONCLUSIONS

Plantar flexion of the ankle produces changes in radiographic measurements of the medial clear space. The potential for false-positive findings of deltoid disruption increases with increasing ankle plantar flexion.

Posterior malleolar stabilization of syndesmotic injuries is equivalent to screw fixation

BACKGROUND

Fixation of unstable ankle fractures, including fixation of posterior malleolus fracture fragments with the attached, intact posteroinferior tibiofibular ligament (PITFL), reportedly provides more stable fixation than transsyndesmotic screws.

QUESTIONS/PURPOSES

To confirm this observation we compared the Foot and Ankle Outcome Score (FAOS) and radiographic maintenance of fixation for fractures treated through direct posterior malleolar fixation versus syndesmotic screw fixation.

METHODS

We prospectively followed 31 one patients with unstable ankle fractures treated with (1) open posterior malleolus fixation whenever the posterior malleolus was fractured, regardless of fragment size (PM group; n = 9); (2) locked syndesmotic screws in the absence of a posterior malleolar fracture (S group; n = 14); or (3) combined fixation in fracture-dislocations and more severe soft tissue injury (C group; n = 8). All patients had preoperative MRI confirming syndesmotic injury and an intact PITFL; postoperative and followup radiographs were evaluated for syndesmotic congruence. The minimum followup was 12 months (mean, 15 months; range, 12-31 months).

RESULTS

Postoperative and followup FAOS scores were similar in the three groups. The tibiofibular clear space was greater in the S versus the PM group, but we found no other differences in the postoperative versus followup measurements between the PM, S, and C groups.

CONCLUSIONS

Syndesmotic fixation through the posterior malleolus and PITFL is maintained at followup, and these patients have functional outcomes at least equivalent to outcomes for patients having syndesmotic screw fixation.

LEVEL OF EVIDENCE

Level II, therapeutic study. See Guidelines for Authors for a complete description of levels of evidence.

Suture-button versus screw fixation of the syndesmosis: a biomechanical analysis

BACKGROUND

The treatment of ankle fractures with syndesmotic injuries associated with disruption of the deltoid ligament complex is controversial. The purpose of this study was to compare both the biomechanical and physiologic properties of suture-button fixation to the intact syndesmosis and screw fixation.

MATERIALS AND METHODS

Eight fresh frozen human cadaveric ankles were used in three different groups. One group had an intact syndesmosis and deltoid ligamentous complex and two groups had fixation of the syndesmosis after its disruption along with disruption of the deltoid ligaments. One fixation group used a suture-button and the other used a 3.5-mm tricortical syndesmotic screw. The syndesmotic gap after cycling at submaximal loads, laxity due to cycling, and fibular movement allowed in the sagittal plane were all measured and analyzed for statistical significance.

RESULTS

The syndesmotic gap after cycling was not significantly different between the intact group (9.1 mm) and the suture-button group (8.8 mm) (p = 0.1509). The screw fixation group had a significantly smaller gap (7.9 mm) as compared to the other two groups (screw versus intact, p = 0.00004; screw versus suture-button, p = 0.0004). The intact group did not demonstrate a significant difference in laxity before (9.0 mm) and after (9.1 mm) cycling (p = 0.0670), whereas the suture-button group did have a significant difference (before, 8.01 mm; after, 8.28 mm) (p = 0.000251). The movement of the fibula in the sagittal plane was significantly greater in the suture-button group (3.17 mm) as compared to the intact group (2.77 mm) (p = 0.00554). Screw fixation allowed significantly less fibular movement in the sagittal plane (1.16 mm) as compared to the intact (p = 0.00014) and suture-button (p = 0.0000012) groups.

CONCLUSION

Suture-button fixation maintained reduction after cycling with submaximal loads that compared favorably to the intact syndesmosis. It also allowed more physiologic movement of the fibula in the sagittal plane when compared to tricortical screw fixation.

CLINICAL RELEVANCE

Syndesmotic injury fixation has traditionally used screws to provide a rigid construct in which healing can take place. We believe a less rigid fixation method, such as suture-button fixation, provides a more physiologic type of healing of the syndesmosis.

Delayed operative treatment of syndesmotic instability. Current concepts review

OBJECTIVE

To review the literature concerning articles evaluating the delayed operative treatment of isolated syndesmotic instability.

MATERIAL AND METHODS

The main databases Pubmed/Medline, Cochrane Database of Systematic Reviews, Cochrane Clinical Trial Register, Current Controlled Trials and Embase were searched from 1988 to September 2008 to identify studies relating to the late reconstruction of the distal tibiofibular syndesmosis after isolated syndesmotic injury. The level of evidence of the included articles was scored.

RESULTS

Fifteen articles were identified, involving 94 ankles with a delayed reconstruction for isolated syndesmotic instability.

CONCLUSION

In subacute (6 weeks to 6 months) total ruptures the focus is to restore the normal anatomy by repair of the ruptured ligament with placement of a syndesmotic screw. On base of the literature in combination with experience in clinical practice some guidelines are formulated. If inadequate remnants of the anterior inferior tibiofibular ligament (AITFL) are present, a tendon graft can be used. The insertion of the AITFL on the tibia can be medialised with a bone block and fixed with a screw. For the treatment of persistent widening and late instability these reconstruction techniques have to be used combined with debridement and placement of a syndesmotic screw to protect the reconstruction. Most adequate treatment for chronic syndesmotic instability (>6 months) is the creation of a synostosis to stabilise the distal tibiofibular joint. Late repairs give satisfactory but less favourable outcome as compared to properly treated acute injuries. It is not easy to regain complete stability by means of these secondary procedures.

Direct visualization for syndesmotic stabilization of ankle fractures

BACKGROUND

Ankle fractures with syndesmotic injury treated via standard trans-syndesmotic fixation have a high percentage of syndesmotic malreduction.(10) We established a protocol involving both direct syndesmosis visualization and meticulous tibial incisura reconstruction via the posterior malleolus fracture fragment, when present, via the attached, intact PITFL, then compared this with historic controls to assess improvement after this type of syndesmosis reconstruction.

MATERIALS AND METHODS

One hundred forty-nine consecutive direct visualization patients were treated prospectively with either open posterior malleolus reduction and fixation, regardless of fragment size ("PM'': 38 patients), or, with no posterior malleolar fracture, open fixation with locked syndesmotic screws ("S'': 97 patients); fracture-dislocations combined both fixation types ("C'': 16 patients). The syndesmosis was opened and debrided in all. All patients had preoperative MRI and postoperative CT. Distances between the fibula and anterior and posterior incisura facets were measured on axial CT. An incongruent joint was defined as an A-P difference greater than 2 mm. Our historic controls were 25 patients previously fixed via indirect, fluoroscopic reduction and syndesmotic screws.

RESULTS

In the direct visualization group, 24 ankles (16%) had incongruity, compared with 13 controls (52%). The average difference between anterior and posterior colliculi measurements between PM and C was significant (p = 0.017).

CONCLUSION

Malreductions were significantly decreased in the direct visualization group. However, our reduction sometimes remains imprecise, even with direct visualization and attention to detail. Also, posterior malleolar reconstruction was more accurate than syndesmotic screw fixation in our study.

Injuries to the distal tibiofibular syndesmosis: an evidence-based approach to acute and chronic lesions

Injuries to the distal tibiofibular syndesmosis are frequent in collision sports. Most of these injuries are not associated with latent or frank diastasis between the distal tibia and fibula and are treated as high ankle sprains, with an extended protocol of physical therapy. Relevant instability of the syndesmosis results from rupture of two or more ligaments leading to a diastasis of more than 2 mm and requiring surgical fixation. Most of these syndesmosis ruptures are associated with bony avulsions or malleolar fractures. Treatment consists of anatomic reduction of the fibula and fixation with one or two tibiofibular syndesmosis screws. Proper reduction and positioning of the screws are more predictive of a good clinical result than the material, size, and number of cortices purchased. Chronic injuries without instability are treated by arthroscopic or open debridement and arthrolysis. Chronic syndesmotic instability can be treated with a three-strand peroneus longus ligamentoplasty in the absence of symptomatic arthritis or bony defects.

Injuries to the tibiofibular syndesmosis

The management of injury to the distal tibiofibular syndesmosis remains controversial in the treatment of ankle fractures. Operative fixation usually involves the insertion of a metallic diastasis screw. There are a variety of options for the position and characterisation of the screw, the type of cortical fixation, and whether the screw should be removed prior to weight-bearing. This paper reviews the relevant anatomy, the clinical and radiological diagnosis and the mechanism of trauma and alternative methods of treatment for injuries to the syndesmosis.

The influence of the number of cortices of screw purchase and ankle position in Weber C ankle fracture fixation

OBJECTIVES

Biomechanical and clinical studies have shown that syndesmosis screws may be indicated in repairing Weber C ankle fractures. This study sought to determine the effect of the number of cortices of screw purchase and ankle position on syndesmosis width and tibiotalar rotation in Weber C ankle fracture fixation.

METHODS

Nine pairs of human cadaver legs were mechanically tested to determine syndesmosis width and tibiotalar rotation. This was done for intact specimens and after a Weber C injury was created and repaired with 3 and 4 cortices of purchase. Tests were performed for no axial load and for axial loads of 700 N with and without external torques of 1 and 5 Nm on the ankle. Torque-to-failure tests were also done for 4 cortices of fixation.

RESULTS

In comparison to baseline, the syndesmosis width was significantly decreased when the syndesmosis screw was inserted in plantarflexion with either 0 or 1 Nm of torque. Syndesmosis width significantly increased when the screw was inserted in dorsiflexion for 5 Nm of torque. For tibiotalar rotation, no statistical differences were detected for either plantarflexion or dorsiflexion when compared to baseline, except with axial load. Syndesmosis width was not affected by the number of cortices purchased by the syndesmosis screw. Failure torque and failure angle were also measured.

CONCLUSIONS

Because no difference was seen between 3 or 4 cortices, it is the surgeon's choice in determining how many cortices of fixation are achieved.

Treatment of syndesmotic disruptions with the Arthrex Tightrope: a report of 25 cases

BACKGROUND

The complexity of syndesmotic injuries, often with both bone and soft tissue injury mandates an expeditious diagnosis and treatment to avoid unfavorable long term outcomes. Various methods of fixation of the syndesmosis have been reported. We present the largest series evaluating the Arthrex Tightrope for management of syndesmotic injuries.

MATERIALS AND METHODS

Twenty-five patients with disruption of the distal tibiofibular articulation underwent treatment with an Arthrex Tightrope. In 21 cases, a single tightrope was placed, and in four cases, two tightropes were utilized. Associated ankle fractures were treated using proper AO technique. Those patients with diabetes and/or neuroarthropathic changes foot or ankle were not included in this study. Postoperative evaluation parameters included radiographic measurements, a modified AOFAS scoring system and SF-12.

RESULTS

Average followup was 10.8 months. The mean time to full weightbearing was 5.5 (range, 2 to 8) weeks. Postoperative radiographic analysis of the mean distance from the tibial plafond to the placement of the tightrope(s), medial clear space, average postoperative tibiofibular overlap and the mean tibiofibular clear space demonstrated no evidence of re-displacement of the syndesmotic complex at an average of 10.8 (range, 6 to 12) months. The modified AOFAS hindfoot scoring scale and SF-12 both demonstrated significant improvements; preoperative values were assessed in the office with the first patient visit as they are incorporated into the patient intake form that each patient fills out at the initial visit.

CONCLUSION

Utilization of the tightrope in diastasis of the syndesmosis should be considered as a good option. The method of placement is quick, can be minimally invasive, and obviates the need for hardware removal. In this series, it maintained excellent reduction of the syndesmosis.

Operative aspects of the syndesmotic screw: review of current concepts

The distal tibiofibular syndesmosis is important for stability of the ankle mortise and thus for weight transmission and walking. Syndesmotic injuries are most commonly associated with fibular fractures, but they can also occur in isolation or with damage to the lateral ankle ligament after traumatic supination. The need for trans-syndesmotic fixation of the distal tibiofibular joint has been controversial. The goal of this review was to collect evidence on the technical aspects of performing an osteosynthesis using a syndesmotic screw and to formulate some recommendations for clinical practice.

Comparison of a novel FiberWire-button construct versus metallic screw fixation in a syndesmotic injury model

BACKGROUND

There is minimal experience with less rigid syndesmotic fixation devices which may approximate the normal distal tibio-fibular mechanics during healing. This study evaluates the ability of a FiberWire-button implant (Arthrex, Naples, FL) to maintain syndesmotic reduction as compared with a metallic screw.

METHODS

Ten matched fresh-frozen cadaveric ankle pairs with intact ligaments were tested (12.5 Nm external rotation force) to establish physiologic syndesmotic diastasis. The same force was applied to the ankles after sectioning of the syndesmotic and deltoid ligaments. Within the pairs, each limb was randomized to receive a FiberWire-button implant or a metallic screw (Synthes, Paoli, PA); the ankles were tested for syndesmotic diastasis with progressive external rotation force, from 2.5 Nm to 25 Nm (or failure).

RESULTS

There was no significant difference in diastasis amongst pairs with intact or sectioned syndesmosis (p=0.64 and p=0.80, respectively). There was a significantly greater diastasis in the FiberWire-button group at all external rotation loads (p<0.0001). Nine of the ten pairs failed (all through fracture of the distal fibula). There were no hardware failures. The metallic screw group failed at a lower load (mean 15 Nm) compared to the FiberWire-button group (mean 18 Nm, p=0.0004). The metallic screw group maintained syndesmotic reduction up to 5 Nm of force.

CONCLUSIONS

The FiberWire-button was unable to maintain syndesmotic reduction of the ankles at any of the forces applied. The ankles fixed with the FiberWire-button demonstrated significantly greater widening of the syndesmosis compared to the screw, at all loads.

CLINICAL RELEVANCE

The FiberWire-button implant may not maintain adequate ankle syndesmotic reduction in the immediate post-operative period relative to a metallic screw.

Syndesmotic ankle sprains in athletes

Ankle sprains are among the most common athletic injuries and represent a significant source of persistent pain and disability. Despite the high incidence of ankle sprains in athletes, syndesmosis injuries have historically been underdiagnosed, and assessment in terms of severity and optimal treatment has not been determined. More recently, a heightened awareness in sports medicine has resulted in more frequent diagnoses of syndesmosis injuries. However, there is a low level of evidence and a paucity of literature on this topic compared with lateral ankle sprains. As a result, no clear guidelines are available to help the clinician assess the severity of injury, choose an imaging modality to visualize the injury, make a decision in terms of operative versus nonoperative treatment, or decide when the athlete may return to play. Increased knowledge and understanding of these injuries by clinicians and researchers are essential to improve the prevention, diagnosis, and treatment of this significant condition. This review will discuss the anatomy, mechanism of injury, diagnosis, and treatment of syndesmosis sprains of the ankle while identifying controversies in management and topics for future research.

Diagnosis and management of the painful ankle/foot part 1: clinical anatomy and pathomechanics

Distinctive anatomical features can be witnessed in the ankle/foot complex, affording specific pathological conditions. Disorders of the ankle/foot complex are multifactoral and features in both the clinical anatomy and biomechanics contribute to the development of ankle/foot pain. The superior tibiofibular, distal tibiofibular, talocrural, subtalar, and midtarsal joint systems must all participate in function of the ankle/foot complex, as each biomechanically contributes to functional movements and clinical disorders witnessed in the lower extremity. A clinician's ability to effectively evaluate, diagnose, and treat the distal lower extremity is largely reliant upon a foundational understanding of the clinical anatomy and biomechanics of this complex complex. Thus, clinicians are encouraged to consider these distinctions when examining and diagnosing disorders of the ankle/foot.

Ankle syndesmotic injury

Ankle syndesmotic injury does not necessarily lead to ankle instability; however, the coexistence of deltoid ligament injury critically destabilizes the ankle joint. Syndesmotic injury may occur in isolation or may be associated with ankle fracture. In the absence of fracture, physical examination findings suggestive of injury include ankle tenderness over the anterior aspect of the syndesmosis and a positive squeeze or external rotation test. Radiographic findings usually include increased tibiofibular clear space decreased tibiofibular overlap, and increased medial clear space. However, syndesmotic injury may not be apparent radiographically; thus, routine stress testing is necessary for detecting syndesmotic instability. The goals of management are to restore and maintain the normal tibiofibular relationship to allow for healing of the ligamentous structures of the syndesmosis. Fixation of the syndesmosis is indicated when evidence of a diastasis is present. This may be detected preoperatively, in the absence of fracture, or intraoperatively, after rigid fixation of the medial malleolus and fibula fractures. Failure to diagnose and stabilize syndesmotic disruption adversely affects outcome.

Syndesmosis fixation: a comparison of three and four cortices of screw fixation without hardware removal

BACKGROUND

Great variability exists in methods of stabilization for syndesmotic disruptions of the ankle. We hypothesized that syndesmotic screw fixation with 3.5-mm fully threaded cortical screws through either three or four cortices would have similar strength and rate of mechanical failure and that retention of screws after fracture healing would not result in adverse clinical symptoms.

METHODS

In a prospective, surgeon-randomized study at a Level-one trauma center, 127 patients with syndesmotic disruptions were treated surgically. Seven patients were lost to followup, leaving 120 for review. Syndesmotic disruptions were stabilized with 3.5-mm fully threaded cortical screws placed through three or four cortices. Screws were removed only if symptomatic. Outcome criteria were screw failure, loss of reduction, and need for hardware removal.

RESULTS

Fifty-nine patients received fixation through three cortices and 61 patients received fixation through four cortices. Mean follow-up was 150 days. In the group with stabilization through three cortices, hardware failure occurred in five patients (8%) and three had a loss of reduction. In the group with stabilization through four cortices, hardware failure occurred in four patients (7%); all were asymptomatic and did not require screw removal. There was no loss of reduction in that group. Comparing the two groups using binary logistic analysis, there was no difference in loss of reduction (p = 0.871), screw breakage (p = 0.689), or need for hardware removal (p = 0.731).

CONCLUSION

The data suggest that either three or four cortices of fixation can be used when stabilizing syndesmotic injuries of the ankle. There was a trend towards higher loss of reduction in the group with tricortical fixation when weightbearing restrictions were not followed. Retention of the syndesmotic screws, even with mechanical failure, does not pose a clinical problem. Weightbearing can be allowed at 6 to 10 weeks without routine removal of screws.

The distal tibiofibular syndesmosis during passive foot flexion. RSA-based study on intact, ligament injured and screw fixed cadaver specimens

INTRODUCTION

The aim of the study was to investigate the kinematics of the distal tibiofibular syndesmosis in intact and ligament injured ankles and to assess how effective is the syndesmotic screw in restraining mortise width variations during passive foot flexion.

MATERIALS AND METHODS

The trials were carried out on seven fresh frozen cadaver specimens. The distal tibiofibular syndesmosis widening was investigated using Roentgen stereophotogrammetric analysis, in intact and ligament injured ankles and after the fixation of the syndesmotic screw. The AO-ASIF recommendations were followed for screw implant.

RESULTS

Injury to the syndesmotic and deltoid ligaments of the ankle did not result in a significant variation of the syndesmosis behavior during passive foot flexion. The 4.5-mm diameter cortical screw used in this study proved effective in restraining mortise width variation during foot flexion. The recorded mortise widening in the flexion arc extending from the neutral to the maximally dorsiflexed position was negligible in intact and ligament injured joints.

CONCLUSION

The result does not endorse the recommendation of placing the foot in full dorsal flexion during screw implantation. The choice of screw fixation as a treatment for ankle syndesmosis disruption should be carefully evaluated.

Ankle syndesmosis injuries

Physician awareness of ankle syndesmosis injuries is improving. The anatomy involved and the mechanism of injury are extremely relevant for the understanding and treatment of this type of injury. Examination under anesthesia may confirm the syndesmosis instability. Based on those findings, stabilization is the recommended approach.

Syndesmosis fixation: analysis of shear stress via axial load on 3.5-mm and 4.5-mm quadricortical syndesmotic screws

The effect of shear stress on a fixated distal syndesmosis of the ankle was evaluated with a servohydraulic materials-testing machine. Eighteen syndesmoses were fixated in a quadricortical technique using 3.5-mm cortical and 4.5-mm cortical stainless steel screws. A shear stress was applied via an axial load in an attempt to simulate weightbearing. The 4.5-mm quadricortical screws produced a higher yield load and peak load (484.3 +/- 93.8 N and 597.7 +/- 81.4 N) when compared with the 3.5-mm quadricortical syndesmotic screws (412.8 +/- 55 N, P = .033 and 511.2 +/- 64.4 N). These findings suggest that a larger diameter screw provides greater resistance to an applied shear stress at the distal syndesmosis.

Distal tibiofibular syndesmosis fixation: a cadaveric, simulated fracture stabilization study comparing bioabsorbable and metallic single screw fixation

Metal screws that are used for ruptured tibiofibular syndesmosis repair are often removed within 3 months of placement, suggesting the utility of bioabsorbable screws. A biomechanical study was performed to compare fixation of a simulated syndesmosis separation with a 5-mm oriented copolymer bioabsorbable (82:18 poly-L-lactic acid/poly-glycolic acid) versus a stainless steel screw. Eight pairs of cadaveric lower-leg specimens were cleaned and a pronation external rotation-type injury was created in each. The syndesmosis was fixed with a single, tricortical bioabsorbable screw in 1 ankle and a metal screw in the contralateral ankle (matched pairs). Sequential testing of the specimens showed that torsional stiffness of the fixed, relative to intact, specimens was nearly equivalent (0.730 +/- 0.260 for copolymer, 0.770 +/- 0.300 for stainless steel; P = .401). Application of 1000 cycles of axial load (90 to 900 N) resulted in a significant decrease ( P < .0001) in axial stiffness for each fixation method, but the relative decrease was equivalent for both ( P = .211). Failure torque (17.8 +/- 8.3 N.m copolymer, 21.0 +/- 11.5 N.m stainless steel; P = .238) and angle of rotation at failure (47.9 +/- 13.6 degrees copolymer, 42.0 +/- 11.5 degrees stainless steel; P = .199) were also nearly equivalent. It appears that the 5.0-mm diameter copolymer screw is biomechanically equivalent to the 5.0-mm diameter stainless steel screw for repair of syndesmosis disruption.

Comparison of the syndesmotic staple to the transsyndesmotic screw: a biomechanical study

BACKGROUND

Controversy still exists about treatment of syndesmotic injuries. This study compared the fixation strengths and biomechanical characteristics of two types of ankle fracture syndesmotic fixation devices: the barbed, round staple and the 4.5-mm cortical screw.

METHODS

Cadaveric testing was done on 21 fresh-frozen knee disarticulation specimens in biaxial servohydraulic Instron testing equipment. Submaximal torsional loads were applied to specimens in intact and Weber C bimalleolar fracture states. The specimens were then fixed with one of two techniques and again subjected to submaximal torsion and torsion to failure. Biomechanical parameters measured included tibiofibular translation and rotation, maximal torque to failure, and degrees of rotation at failure.

RESULTS

Compared to the intact state before testing, the staple held the fibula in a more anatomic position than the screw for mediolateral and anterior displacements (p < 0.01). With submaximal torsional testing, the staple restored 85% of the tibiofibular external rotation and all of the posterior translation values as compared to the intact state. The screw resulted in 203% more tibiofibular medial translation and 115% more external rotation than the intact state. The degree of tibial rotation during submaximal torsional loading was restored to within 15% of intact values but was 21% less with the screw. There was no statistical difference between the screw and staple when tested in load to failure. Tibiotalar rotation at failure was statistically different with the staple construct, allowing more rotation as compared to the screw.

CONCLUSION

The staple restored a more physiologic position of the fibula compared to the syndesmotic screw. Both provided similar performance for the load to failure testing, while the screw reduced tibial rotation more after cyclic loading. There was more tibial rotation before failure for the staple, suggesting a more elastic construct. This study provides biomechanical data to support the clinical use of the syndesmotic staple.

Predictors of functional outcome following transsyndesmotic screw fixation of ankle fractures

OBJECTIVE

Given the continued debate regarding syndesmotic screw fixation, we reviewed our institution's series of ankle syndesmotic screw insertions: 1) to examine technical aspects of syndesmotic screw fixation; and 2) to identify predictors of function and quality of life utilizing validated instruments.

DESIGN

Retrospective observational study (level IV).

SETTING

Three university hospitals.

PATIENTS AND METHODS

All patients with ankle injuries who received syndesmotic screw fixation at 3 university-affiliated hospitals from 1998 to 2001. A combined hospital database for all 3 university affiliated hospitals was searched to identify all ankle fractures. Potentially eligible patients' charts were hand searched to determine the use of syndesmotic screw fixation. Radiographs from each patient were assessed for final eligibility for study inclusion. Baseline demographic information, fracture type (Lauge-Hansen, AO Weber), radiographic measurements of syndesmotic reduction, type of implants (number of screws, number of cortices, screw size), and screw removal at follow-up were determined. All radiographs were standardized for magnification. Patients also reported return to work, a visual analogue ankle pain score, and completed 2 functional outcomes instruments (Short Musculoskeletal Functional Assessment Index, Olerud and Molander Scale).

MAIN OUTCOMES

Return to work, a visual analogue ankle pain score, and 3 functional outcomes instruments (Short Musculoskeletal Functional Assessment Index, Olerud and Molander Scale).

RESULTS

Of 425 ankle fractures treated, 51 fractures had syndesmotic screw fixation. Patients were often males (67%), mean age 40.0 +/- 18.0 years, with sedentary occupations (88%), and twisting injuries (80%). Seventy percent of injuries were pronation external rotation injuries, and 30% were supination external rotation injuries. The ankle was dislocated in 45% of cases. The most common constructs for fixation included lateral plates with syndesmotic screws (45%). The majority of constructs included a single 3.5-mm cortical screw through 3 cortices of bone. Based upon postoperative x-rays, 16% of syndesmoses were not reduced. Additionally, 8 patients were deemed have inappropriate/lack of indications for syndesmotic screw insertion. At final follow-up (N = 39 patients, mean 18.1 months), patients achieved good function and quality of life (mean scores: Short Musculoskeletal Functional Assessment functional index = 11.4 +/- 10.6, Short Musculoskeletal Functional Assessment bother index = 13.5 +/- 13.1, Olerud and Molander = 74.1 +/- 23.4, visual analogue pain scale = 1.7 +/- 1.9). The only significant predictor of functional outcome was reduction of the syndesmosis (P = 0.04). This variable alone accounted for 18% of the variation in Short Musculoskeletal Functional Assessment Index physical function scores and 15% of the variance in the Olerud and Molander (running subscale) outcome measure.

CONCLUSIONS/SIGNIFICANCE

Our findings suggest: 1) technical aspects of syndesmotic screw fixation vary between surgeons; 2) 16% of syndesmotic screws may have been unnecessary; and 3) despite variability in technique and indications, anatomic reduction of syndesmosis was significantly associated with improved Short Musculoskeletal Functional Assessment Index functional outcome. Larger, prospective studies are needed to further explore our findings.