A total of two studies were excluded beforehand as being solely technical descriptive manuscripts [
8,
57]. One study was excluded being a radiological awareness review [
41]. The number of studies available is shown per section: biomechanical and functional outcome.
Biomechanical
A total of six biomechanical studies were identified using a suture-button device [
17,
29,
49,
52,
55,
58]. The study by Miller et al. [
36] was not included, as a suture (no. 5 braided polyester) without buttons looped through drill holes at two levels in the tibia and fibula for the fixation of a syndesmotic disruption was used.
An overview of the six included biomechanical studies using a suture-button device and key findings is shown in Table
1. Below is a summary of the different studies and testing protocols.
Table 1
Biomechanical studies of suture-button repair of distal tibiofibular syndesmotic injuries
| 10 FFCA with No5 braided polyester suture and polyethylene buttons | 10 FFCA with single 3.5 mm tri-cortical screw | Pull-out strength SB lower, but more consistent. Less dependent on bone quality. Failure always through button |
Thornes et al. (2003) [ 58] | 8 ECA with No5 braided polyester suture and metallic endobuttons | 8 ECA with single 4.5 mm four-cortical screw | No significant difference between SB and screw fixation. SB more consistent performance |
Forsythe et al. (2008) [ 17] | 10 FFCA with TightRope | 10 FFCA with single 4.5 mm four-cortical screw | Significantly greater diastasis in the suture-button group at all external rotation loads. No hardware failures. Screw failed at lower load compared to the suture-button |
| 10 FFCA with two TightRopes | 10 FFCA with single 3.5 mm four-cortical screw | No significant difference in translation and rotation between SB and screw. Screw had significantly greater failure torque versus SB. Two SB behave similarly to the syndesmotic screw in the syndesmotic rupture injury model |
Klitzman et al. (2010) [ 29] | 8 FFCA with TightRope | Same 8 FFCA with single 3.5 mm screw | Syndesmotic gap after testing not significantly different between intact and the SB group, screw group had significantly smaller gap |
Teramoto et al. (2011) [ 55] | 6 FFCA sequentially tested intact, syndesmotic injury, single TightRope, double TightRope, anatomical TightRope, and 3.5-mm screw model | Screw most rigid fixation, anatomical SB adequate fixation, single and double SB insufficient stabilization in multidirectional testing |
In the study by Seitz et al. [
49], 20 cadaver legs (level of amputation unknown) were used. The talus was disarticulated from the ankle joint, and all surrounding soft tissues were removed. All syndesmotic ligaments were divided and a pull-out (pull-apart) test to failure was performed comparing a self-constructed suture-button device made of a double No5 braided polyester suture and polyethylene buttons.
Thornes et al. [
58] used 16 embalmed cadaver legs (level of amputation unknown) of which the medial deltoid and syndesmotic ligaments were sectioned. The testing included 12.5 Nm rotation stress comparing the suture-button device using metallic buttons and a 4.5-mm screw. The principal author is designer of the currently used suture-button device and patented the device [
58].
Forsythe et al. [
17] used ten cadavers amputated above the knee, which were tested using 12.5-Nm external rotation after sectioning of the deltoid ligament, distal 15 cm of the interosseous membrane, and anterior tibiofibular ligament. The posterior tibiofibular ligament and the fibula were left intact (Boden model). The TightRope system and a 4.5-mm screw were compared. Worth mentioning is that this study was funded by the manufacturer of the suture-button device.
Soin et al. [
52] used 20 cadaver legs disarticulated at knee level, and divided the anterior tibiofibular, posterior tibiofibular, deltoid, and interosseous ligaments using minimal soft tissue dissection. The testing protocol used cyclic axial compression with 750 N, 7.5-Nm external rotation, and a combination of both, while comparing a 3.5-mm screw and two TightRopes.
Klitzman et al. [
29] used eight cadaver legs amputated below the knee, and with minimal soft tissue dissection the anterior, posterior, transverse, interosseous tibiofibular, and deltoid ligaments were sectioned. With an axial load of 50 N and 5 Nm torque, the TightRope system and a 3.5-mm screw were compared to investigate the syndesmotic diastasis after cycling at submaximal loads, laxity due to cycling, and fibular movement in the sagittal plane.
Teramoto et al. [
55] used six above-knee amputated cadaver legs. The similar syndesmotic disruption model was used as Forsythe, with the anterior tibiofibular ligament, the distal 15 cm of the interosseous membrane, and the deltoid ligament divided. Using 5-Nm external rotation (in dorsiflexion and inversion) an intact syndesmosis, a syndesmotic injury model, single TightRope fixation, double TightRope, anatomical TightRope placement, and 3.5-screw model were sequentially tested.
Functional outcome
Two studies were not included in the functional outcome analysis. The study by Seitz et al. [
49] was one, because it used a device, which was not pre-assembled, with polyethylene buttons which appeared to be the weakest link in testing. Newer devices used metallic endobuttons. In the clinical part of the study by Seitz et al., 11 of the 12 Weber-C injuries regained pre-injury levels at an average follow-up of 3.2 years, there were no device failures, and all were routinely removed after eight to 12 months [
49]. The other excluded study was by Nelson [
40]; who used three strands of no. 2 nonabsorbable sutures looped around a fibular and tibial screw.
Four abstracts following a scientific meeting, published in well renowned journals, were identified and were found adequately usable [
18,
34,
44,
60].
A total of eight full-text studies were identified, of which one used the same data considering the patients with a TightRope but added a control group (with a syndesmotic screw) in the second publication [
9‐
11,
14,
39,
42,
59,
64]. Only the latter was used in the current analysis.
The cardinal study characteristics and key results of the seven full-text and four abstracts are shown in Table
2. Below is a summarized description per included full-text article.
Table 2
Study characteristics and key results
Thornes et al. (2005) [ 59] | 16 | 16 | 3 | 12 | AOFAS (100) | 93 vs 83 | 0 vs 12 | None | None |
SB earlier return to work |
McMurray et al. (2007) [ 34] a
| 16 | None | 4 | 5 | AOFAS | 87 | 2 | 1 | None |
Cottom et al. (2008–2009) [ 11] | 25 | 25 | 3 | 10 | modAOFAS (63) | 51 vs 54 | 0 vs 17 | N.A. | None |
SF12 | 102 vs 102 |
Coetzee and Ebeling (2009) [ 9] | 12 | 12 | 1 | 28 | AOFAS (100) | 94 vs 88 | 1 vs 1 | N.A. | None |
| 38 | None | 4 | 14–42 | N.A. | N.A. | 3 | 2 | None |
Rajkumar et al. (2009) [ 44] a
| 12 | 12 | 3 | 14 | OMAS (100) | 86 | N.A. | N.A. | N.A. |
SB earlier mobilization and return to work |
Treon et al. (2009) [ 60] a
| 18 | None | 4 | 4–41 | N.A. | N.A. | 4 | 6 | 2 |
Willmoth et al. (2009) [ 64] | 6 | None | 4 | 5 | N.A. | N.A. | 2 | None | None |
DeGroot et al. (2011) [ 14] | 24 | None | 4 | 20 | AOFAS (100) | 94 | 6 | None | None |
| 16 | None | 4 | 26 | AOFAS (100) | 86.9 | 1 | 2 | None |
| 49 | None | 4 | 24 | AOFAS (100) | 85.6 | 3b
| 2 | None |
FADI (100) | 81.2 |
Thornes et al. performed a non-randomized prospective trial in which patients treated by the leading author received a suture-button device and in his absence patients were treated with a syndesmotic screw by others from the same institution [
59]. The fractures were classified as Weber-C in all cases, and all patient characteristics were comparable in both groups. The conflict of interest statement reported funding from a patent concerning the suture-button device.
Cottom et al. published their series treated with a TightRope in 2008. In 2009 apparently the outcome of these same patients was compared to a series of patients treated with a syndesmotic screw [
10,
11]. The study type is not stated in both articles, but is most likely a retrospective comparative because of the difference in follow-up. There were eight Weber-B, five Weber-C, four Maisonneuve, and eight pure ligamentary injuries in the TightRope group. A modified AOFAS-score was used without the physical exam components, and a maximum of 63 points.
Willmott et al. showed, in a series of six patients (four Weber-C, one Maisonneuve, one ligamentary diastasis), a previously unreported high incidence of implant removal [
64]. A total of two TightRopes needed removal due to wound irritation (granuloma formation).
Coetzee et al. published an interim analysis of their randomized trial in which 12 patients in both study arms were included [
9]. It is unclear which fracture types were included in both groups. A non-significant improvement in range of motion, mainly plantar-flexion, was reported (
p = 0,054). The study is possibly still ongoing and hopefully the Olerud Molander Ankle Score will be included at the final follow-up to make a better comparison with the available literature.
DeGroot et al. reported on 24 patients in a retrospective fashion [
14]. Fractures were classified according to the Lauge-Hansen classification. In most patients two Tight-Ropes were placed. This study was the first to report osteolysis and subsidence of the suture button through the cortex of the fibula or tibia and slight enlargement of the tibial tunnel, which appeared to more likely occur with longer follow-up.
Qamar et al. reported the results of 16 patients with predominantly Weber-C injuries [
42]. The single indication where the implant was removed was probably due to the sutures being cut off too short. Even though the authors do not report on the subsidence of the suture button through the cortex, their radiographic images show this effect at follow-up after 24 months.
The study by Naqvi et al. is the largest series thus far [
39]. A total of six Weber-B, 29 Weber-C, 11 Maisonneuve, and three ligamentary injuries were included. At a certain point in time the authors modified their technique to bury the knot at the lateral side. Using this modification no implant removed has been needed since.
Outcome comparison with the ‘gold standard’
The main difficulty in comparing the functional outcome between the syndesmotic screw and the TightRope system is that most studies using the positioning screw use the Olerud Molander Ankle Score (OMAS) (11 out of 27) and less frequently the American Orthopaedic Foot Ankle Society (AOFAS) Score (six out of 27), whereas the most frequently used functional score in the TightRope studies is the AOFAS (seven out of 11) (Tables
2 and
3).
Table 3
Outcome comparison
Kennedy et al. (2000) [ 28] | 26 | 35 | 26 | Baird-Jackson (100) | 62.8 |
Thordarson et al. (2001) [ 56] | 32 (17 abs) | 11 | 15 | N.A. | N.A. |
| 17 | 12 | 17 | N.A. | 94% GE |
| 23 (abs) | 34 | 0 | OMAS (100) | 94 |
Sinisaari et al. (2002) [ 51] | 30 (18 abs) | 20 | 12 | OMAS (100) | 85.2 |
Hoiness and Stromsoe (2004) [ 23] | 64 | 12 | 32 | OMAS (100) | 88.9 |
Sproule et al. (2004) [ 53] | 14 | 25 | 13 | GFA (100) | 95.6 |
Shoe comfort (100) | 81.7 |
Kaukonen et al. (2005) [ 27] | 38 (20 abs) | 35 | 18 | N.A. | N.A. |
Kukreti et al. (2005) [ 30] | 36 | 35 | 33 | N.A. | 86%satisfied |
Thornes et al. (2005) [ 59] | 16 | 12 | 12 | AOFAS (100) | 83 |
Weening and Bhandari (2005) [ 62] | 51 | 18 | 30 | OMAS (100) | 74.1 |
SMFA (0) | 11.4 |
| 30 | 15 | 23 | Baird-Jackson (100) | 87.5 |
| 120 | 5 | 7 | N.A. | N.A. |
| 17 | 12 | 6 | OMAS (100) | 87.3 |
| 70 (abs) | 33 | 2 | AOFAS (100) | 90 (82.8% GE) |
Coetzee and Ebeling (2009) [ 9] | 12 | 28 | 1 | AOFAS (100) | 88 |
Cottom et al. (2009) [ 11] | 25 | 10 | 17 | modAOFAS(63) | 54 |
De Vil et al. (2009) [ 13] | 28 (bolt) | 66 | 5 | AOFAS (100) | 86 |
| 52 | 30 | 27 | N.A. | N.A. |
Rajkumar et al. (2009) [ 44] | 12 | 14 | N.A. | OMAS (100) | 86 |
| 21 | 12 | 15 | OMAS (100) | 81.1 |
| 79 | 12 | 11 | AOFAS (100) | 83.5 |
SMFA (0) | 14.5 |
Manjoo et al. (2010) [ 32] | 76 | 23 | 12 | LEM (100) | 81.4 |
OMAS (100) | 60.0 |
Miller et al. (2010) [ 35] | 25 | 3 | 25 | OMAS (100) | 75.0 |
Mohammed et al. (2010) [ 37] | 12 | 13 | 12 | OMAS (100) | 75 |
Wikerøy et al. (2010) [ 63] | 48 | 101 | 33 | OMAS (100) | 82.5 |
AOFAS (OTA) (100) | 86.5 |
| 52 | 19 | 47 | Bray (100) | 82.7%satisfied |
Three studies compared the results of TightRope with syndesmotic screw fixation [
9,
11,
59]. In the TightRope group two of these studies showed a higher AOFAS score (ten and six points increase, respectively), whereas one showed a three-point lower outcome on a modified score. A total of seven studies used a (non-modified) AOFAS score in the suture-button treatment group [
9,
14,
34,
39,
42,
59]. The weighted average outcome of 133 patients in these six studies was 89.1 points, with an average study follow-up of 19 months. When comparing this outcome to literature on screw (metallic and absorbable) and bolt fixation, including only studies using the AOFAS score, six studies were identified with 253 patients and a weighted average score of 86.3 points, with an average study follow-up of 42 months [
1,
9,
13,
16,
59,
63] (Table
3). Two studies reported a significant earlier return to work in the TightRope group [
44,
59].
Need for implant removal
Prominent suture-buttons or wound complications with a need for implant removal was reported in ten studies out of the 11 included on the treatment of syndesmotic disruption with a suture-button (Table
2). These studies treated 220 patients treated with a TightRope, of which 22 (10%) were removed at an average follow-up of 16 months, with a range of implant removal between zero and 25%. Twenty-four studies were identified within the last decade using metallic screws or bolts, which reported on the need for implant removal with an average follow-up of 24 months [
5,
9,
11,
13,
16,
19,
20,
23,
25,
27,
28,
30,
32,
35,
37,
38,
45,
46,
51,
53,
56,
59,
62,
63]. In these studies a total of 866 patients were treated with a syndesmotic screw or bolt and in 449 cases the implant was removed (51.9%), usually prior to weight-bearing. The rate of implant removal ranged from 5.8 to 100%, depending on hospital protocol. In 12 studies syndesmotic screws were removed on a regular basis, e.g. in more than three-quarters of patients.