Trans-syndesmotic fixation in supination external rotation type 4 injuries: Are intraoperative tests reliable?

ABSTRACT

BACKGROUND:

Ankle fractures occur due to a rotational mechanism. According to the Lauge-Hansen classification, supination-external rotation (SER) injuries are the most common type. Following osseous fixation, the evaluation and treatment of syndesmotic injuries in these injuries are controversial. This study aimed to evaluate the clinical, functional, and radiological results of trans-syndesmotic fixation using intraoperative tests in SER type 4 ankle injuries.

METHODS:

Ankle syndesmosis was intraoperatively evaluated using cotton/hook and manual external rotation stress tests in 64 patients with SER type 4 fracture dislocation injuries. These patients were divided into two groups: those treated with and without trans-syndesmotic fixation in addition to open reduction and internal fixation of the fractures. Ankle range of motion (ROM), American Orthopedic Foot and Ankle Society (AOFAS) Ankle-Hindfoot Score, and Olerud-Molander Ankle Score (OMAS), tibiofibular overlap, tibiofibular clear space, and joint arthritis based on the Kellgren-Lawrence (K-L) scale were evaluated.

RESULTS:

Median values of OMAS (Z=-3.92, p<0.001), AOFAS (Z=-4.31, p<0.001), and ROM (Z=-2.95, p=0.003) were higher in Group 1. There were no differences between the groups regarding tibiofibular overlap median values (Z=-0.59, p=0.0554), tibiofibular clear space (Z=-1.13, p=0.258), and Kellgren-Lawrence arthritis scale. Lack of posterior malleolus fixation was found to increase the risk of arthritis by 18.197 times, despite having trans-syndesmotic fixation, which was statistically significant (Confidence Interval, CI: 2.482-133.417, p=0.004) (Table 4).

CONCLUSION:

Median values of OMAS, AOFAS, and ROM in patients without trans-syndesmotic fixation were lower. These results indicate that intraoperative tests may not provide entirely accurate results in SER type 4 injuries. Failure to detect a syndesmotic injury timely can result in instability. Therefore, we think that routine trans-syndesmotic fixation, as well as posterior malleolus fixation in SER type 4 ankle injuries, may improve outcomes.

INTRODUCTION

The diagnosis and treatment of syndesmotic injuries following the initial fixation of the fibula in supination-external rotation type 4 ankle injuries is still controversial. Supination-external rotation (SER) injuries are the most common type of ankle injury.[1-3] SER type 4 ankle injuries can be accompanied by fractures of the lateral, medial, and posterior malleoli, as well as tibiotalar dislocation and syndesmotic injury. Failing to diagnose a syndesmotic injury leads to long-term ankle instability and joint arthritis. In these injuries, pre-operative direct radiographs including anteroposterior (AP), lateral, and mortise views are followed by computed tomography (CT) if necessary.[4-7] Intraoperative tests are also commonly used in the assessment of ankle syndesmotic injuries. Cotton/hook and manual external rotation tests are performed after the fixation of the fibula. However, intraoperative tests are subjective.[8-12] In this study, the clinical, functional, and radiological results of operatively treated SER type 4 fracture dislocations were evaluated. It was hypothesized that intraoperative diagnostic tests in SER type 4 fracture dislocations are not reliable and that routine trans-syndesmotic fixation would provide better clinical, functional, and radiological outcomes.

MATERIALS AND METHODS

Permission from the local clinical research ethics committee was obtained (ethics committee number 2020.08.174 and topic number KAEK/2020.08.174). Patient-related information from the hospital database was collected anonymously. This study was conducted in accordance with the Helsinki Declaration.

In this retrospective study, operatively treated patients admitted to our orthopedic surgery and traumatology department (level 3 trauma center) with SER type 4 fracture dislocations were evaluated. A total of 1,637 patients admitted to our orthopedic surgery and traumatology department between January 2016 and January 2022 with ankle fractures were screened for this study. The radiological tests of these patients were assessed and classified according to the Lauge-Hansen classification. Out of these, 296 patients were identified to have sustained SER type 4 injuries. Among these patients, only 83 had accompanying dislocations. Only patients older than 18 years of age without concomitant injuries were included in the study. Patients who were operated on within one week after sustaining the injury and with at least one year of follow-up time were included in the study. Patients with open fractures, polytrauma, additional injuries on the ipsilateral extremity, external fixator application, application of supra-syndesmotic fixation, compartment syndrome, additional intervention due to soft tissue complications, isolated deltoid ligament injuries, and those who did not come for follow-up were excluded from the study. Finally, 64 operatively treated patients who sustained SER type 4 ankle fracture dislocations and fulfilled the eligibility criteria were included in the study. The included patients were divided into two groups. Group 1 consisted of 37 patients who received trans-syndesmotic fixation (Fig. 1), and Group 2 consisted of 27 patients who did not receive trans-syndesmotic fixation (Fig. 2).

Figure 1.

Supination-external rotation (SER) type 4 injury treated with trans-syndesmotic fixation. Views include pre-operative, early post-operative, and late post-operative.

Figure 2.

SER type 4 injury treated without trans-syndesmotic fixation. Views include pre-operative, early post-operative, and late post-operative.

Data Collection and Evaluation Criteria

Patients’ demographic, functional, and radiological data were evaluated. Demographic evaluation included age, gender, body mass index (BMI), and time to surgery. Clinical evaluation consisted of ankle range of motion (ROM), American Orthopaedic Foot and Ankle Society (AOFAS) scoring scale, and the Olerud-Molander Ankle Score (OMAS). Radiological evaluation involved tibiofibular overlap, tibiofibular clear space, and degree of ankle arthritis based on the Kellgren-Lawrence scale.[13] The medial clear space was considered irrelevant and was not assessed.

Surgical Procedure

Surgeries were performed under general anesthesia or spinal block according to the standard protocol. Antibiotic prophylaxis (cefazolin sodium) was administered routinely during the first 24 hours after the surgery. The surgical technique was decided by the attending surgeon. Some surgeons did not prefer trans-syndesmotic fixation if intraoperative tests were negative, while some preferred trans-syndesmotic fixation routinely despite a negative test. Surgical steps began with open reduction and internal fixation where a screw or a buttress plate was applied to posterior malleolus fractures if the fragment size was more than 10% of the articular surface or if there was more than 2 mm articular step-off. Then, osseous fixation of the fibula was performed with an anatomical plate. Finally, the medial malleolus was fixed using a screw or tension-band wiring technique, followed by intraoperative stress tests to evaluate syndesmotic stability and to determine the need for temporary syndesmotic fixation. These intraoperative stress tests included a manual external rotation stress test and a cotton/hook test. The former is done by abducting and externally rotating the dorsiflexed foot. The latter is done by placing a hook around the fibula and pulling it while applying countertraction on the tibia. Fixation was performed if one of these two intraoperative tests was positive. A positive test was defined if tibiofibular diastasis occurred. Fixation of the posterior malleolus did not preclude intraoperative tests. A 3.5 millimeter screw (partially or fully threaded, cannulated screw) was applied proximally and parallel to the joint line in a posterolateral to anteromedial direction, penetrating three cortices. A short leg splint was applied initially. Early active ROM exercises were started after the removal of the splint, and weight-bearing was avoided for six weeks. Trans-syndesmotic screws were not extracted earlier than eight weeks.

Statistical Analysis

Demographic and clinical traits of the cases included in the study were examined with statistical analyses (quantity, percentage, average, standard deviation, etc.). The Mann-Whitney U test was used to compare age, BMI, time to surgery, follow-up period, fractured posterior malleolus fragment size, functionality calculations, tibiofibular overlap, and tibiofibular clear space between the two groups. Chi-square analysis was applied to compare gender, injury side, the existence of posterior fixation, and the Kellgren-Lawrence scale between the two groups. The level of significance was set to p<0.05 for all analyses. IBM SPSS 22.0 (IBM, Chicago, IL, USA) was utilized for statistical evaluations.

RESULTS

Group 1 had a median age of 38, whereas Group 2 had a median age of 42. In Group 1, 48.6% were male, and in Group 2, 51.9% were male patients. There was no statistically significant difference between the groups regarding the median values of age (Z=-1.19, p=0.234), BMI (Z=-1.35, p=0.178), time to surgery (Z=-0.27, p=0.786), follow-up period (Z=-1.03, p=0.304), and fractured posterior malleolus fragment size (Z=-0.27, p=0.789). No statistically significant difference was found between the groups regarding gender (X²=0.06, p=0.800), injured side (X²=0.58, p=0.448), and presence of posterior fixation (X²=1.54, p=0.214) (Table 1).

Table 1.

Comparison of demographic and clinical traits of patients evaluated in the study

	Trans-Syndesmotic Fixation Applied		Trans-Syndesmotic Fixation Not Applied		Analysis	p
	Median/n	25-75%	Median/n	25-75%
Age	38.00	29.00-48.00	42.00	35.00-55.00	Z=-1.19	0.234
Gender
Male	18	48.6	14	51.9	X2=0.06	0.800
Female	19	51.4	13	48.1
Body Mass Index (BMI) Z=-1.35	28.08	26.84-29.97	28.98		27.78-30.83	0.178
Time to Surgery (days)	2.00	1.00-4.00	2.00	1.00-4.00	Z=-0.27	0.786
Follow-up Period (months)	38.0	29.0-47.0	44.0	30.0-54.0	Z=-1.03	0.304
Fractured Posterior Malleolus Z=-0.27	10.00	0.00-15.00	5.00		0.00-15.00	0.789
Fragment Size
Injured Side
Right Left	17 20	45.9 54.1	15 12	55.6	X2=0.58	0.448
Left	20	54.1	12	44.4
Presence of Posterior Fixation
Yes	33	89.2	21	77.8	X2=1.54	0.214
No	4	10.8	6	22.2

Z: Mann-Whitney U test; X²: Chi-Square Test.

There was no statistically significant difference regarding the median values of post-operative tibiofibular overlap (Z=-0.59, p=0.0554) and post-operative tibiofibular clear space (Z=-1.13, p=0.258) between the two groups. There was no statistically significant difference regarding the Kellgren-Lawrence scale between the two groups (Table 2).

Table 2.

Comparison of radiological calculations between the two groups

	Trans-Syndesmotic Fixation Applied		Trans-Syndesmotic Fixation Not Applied		Analysis	p
	Median/n	25-75%	Median/n	25-75%
Age	38.00	29.00-48.00	42.00	35.00-55.00	Z=-1.19	0.234
Gender
Male	18	48.6	14	51.9	X2=0.06	0.800
Female	19	51.4	13	48.1
Body Mass Index (BMI)	28.08	26.84-29.97	28.98	27.78-30.83	Z=-1.35	0.178
Time to Surgery (days)	2.00	1.00-4.00	2.00	1.00-4.00	Z=-0.27	0.786
Follow-up Period (months)	38.0	29.0-47.0	44.0	30.0-54.0	Z=-1.03	0.304
Fractured Posterior Malleolus	10.00	0.00-15.00	5.00	0.00-15.00	Z=-0.27	0.789
Fragment Size
Injured Side
Right	17	45.9	15	55.6	X2=0.58	0.448
Left	20	54.1	12	44.4
Presence of Posterior Fixation
Yes	33	89.2	21	77.8	X2=1.54	0.214
No	4	10.8	6	22.2

Z: Mann-Whitney U test; X²: Chi-Square Test.

Group 1 demonstrated significantly higher results compared to Group 2 regarding median values of the OMAS (Z=-3.92, p<0.001), AOFAS (Z=-4.31, p<0.001) scoring scale, and ROM (Z=-2.95, p=0.003) (Table 3).

Table 3.

Comparison of functional evaluations between the two groups

	Trans-Syndesmotic Fixation Applied		Trans-Syndesmotic Fixation Not Applied		Analysis	p
	Med.	25-75%	Med.	25-75%
OMAS	80.00	75.00-85.00	75.00	60.00-75.00	Z=-3.92	<0.001
AOFAS	76.00	69.00-79.00	68.00	53.00-72.00	Z=-4.31	<0.001
ROM	60.00	50.00-65.00	55.00	20.00-60.00	Z=-2.95	0.003

Med.: Median; Z: Mann-Whitney U test; OMAS: Olerud-Molander Ankle Score; AOFAS: American Orthopaedic Foot and Ankle Society; ROM: Range of Motion.

Furthermore, patients with mild, moderate, and severe arthritis were grouped together to categorize and compare 46 patients with arthritis and 18 patients without any signs of arthritis. According to multivariate logistic regression analysis, parameters such as age (p=0.492), gender (p=0.492), BMI (p=0.319), injured side (p=0.080), presence of a posterior malleolus fracture (p=0.216), and presence of trans-syndesmotic fixation (p=0.131) were found to have no statistically significant effect on increasing the risk of arthritis. However, the lack of posterior malleolus fixation was found to increase the risk of arthritis by 18.197 times despite having a trans-syndesmotic fixation, which was statistically significant (confidence interval (CI): 2.482-133.417, p=0.004) (Table 4).

Table 4.

Variables associated with increased risk of arthritis

	B	SE	Wald	df	p	Odds Ratio	95% CI
							LL	UL
Age	-0.019	0.027	0.473	1	0.492	0.981	0.930	1.035
Gender (Male)	-0.286	0.751	0.145	1	0.703	0.751	0.172	3.274
Body Mass Index (BMI)	0.143	0.143	0.994	1	0.319	1.154	0.871	1.528
Injured Side (Right)	-1.238	0.708	3.059	1	0.080	0.290	0.072	1.161
Presence of Posterior	0.987	0.797	1.533	1	0.216	2.684	0.562	12.809
Malleolus Fracture (None)
Presence of Posterior	2.901	1.016	8.147	1	0.004	18.197	2.482	133.417
Malleolus Fixation (None)
Group (Trans-Syndesmotic-1.151		0.762	2.280	1	0.131	0.316	0.071	1.409
Fixation Applied)

n=64; X2=17.43; p=0.015; Nagelkerke R2=0.34. Result of multivariate logistic regression analysis. CI: Confidence Interval; LL: Lower Limit; UL: Upper Limit; SE: Standard Error.

DISCUSSION

The outcomes of this study are as follows: First, the overall values of the OMAS, AOFAS scoring scale, and ROM were better in Group 1. Second, post-operative tibiofibular clear space and tibiofibular overlap values were similar between the two groups. Third, the level of arthritis according to the Kellgren-Lawrence scale was found to be similar between the two groups. Fourth, the risk of arthritis increased approximately 18 times in patients who did not receive a posterior malleolus fixation due to small size, despite having a trans-syndesmotic fixation performed.

Evaluation of clinical and radiological results of SER type 4 fracture dislocations of the ankle with a mean follow-up time of 4.7 years was performed. SER injuries of the ankle are associated with syndesmotic instability. Evaluation of ankle functions with the AOFAS and OMAS scoring systems, which were used in this study, has been found to be effective.[14,15] In accordance with the current literature, this study demonstrated that trans-syndesmotic fixation is associated with higher OMAS, AOFAS, and ROM values.

In their prospective study with 38 patients suffering from SER injuries, Jenkinson et al.[8] concluded that preoperative radiographic examinations and biomechanical criteria are insufficient to detect syndesmotic injury, and suggested the use of intraoperative tests. However, a cadaver bone model study by Hallbauer et al.[11] emphasizes the high variability of widely used intraoperative tests. They reported that the cotton test, frequently used during operations to identify syndesmotic injury in ankle fractures, is not reliable for intraoperative diagnosis. Additionally, Pakarinen et al.[12] demonstrated that the sensitivity of intraoperative tests is inadequate in detecting syndesmotic joint stability. They further claimed that trans-syndesmotic fixation has no functional effect and concluded that syndesmosis injury is rather rare in SER injuries of the ankle. In their prospective study including 24 patients, Lehtola et al.[16] reported that trans-syndesmotic fixation made no functional difference in SER type 4 injuries of the ankle. Choi et al.[17] investigated the effect of deltoid ligament repair in SER type 4 injuries but also did not find a significant difference between the repaired group and the non-repaired group. In contrast, Gill et al.[10] suggested the application of trans-syndesmotic fixation in SER type 4 injuries due to the insufficiency of intraoperative tests in detecting syndesmosis injury. Thus, we assumed that the poor radiological and functional outcomes associated with Group 2 in our study are correlated to the low sensitivity of pre-operative and intraoperative tests.

Regarding the radiological parameters (tibiofibular clear space and tibiofibular overlap), our results were in accordance with the current literature. In their prospective randomized trial with 140 SER type 4 ankle injury patients, Kortekangas et al.[18] reported no significant radiological difference between the patient group that received trans-syndesmotic fixation and the group that did not. In another cadaver study, Stoffel et al.[19] claimed that intraoperative parameters of medial clear space, tibiofibular clear space, and tibiofibular overlap were fairly sensitive, but the medial clear space could be affected by isolated injuries to the anterior inferior tibiofibular and deltoid ligaments. In the same manner, Jiang et al.[20] indicated that widening of the tibiofibular clear space is much more directive in assessing ankle syndesmosis. On the contrary, Beumer et al.[21] concluded that none of the parameters, including tibiofibular clear space, tibiofibular overlap, and medial clear space, is optimal in diagnosing a syndesmotic injury. Furthermore, Pakarinen et al.[12] demonstrated no significant difference in radiological parameters between patients who were and were not treated with trans-syndesmotic fixation. Moreover, in a cadaveric study, Fisher et al.[22] suggested the utilization of dynamic ultrasound to determine syndesmosis injuries. These results were thought to be related to the insufficient sensitivity of radiographic calculations. In our study, no significant correlation was identified between syndesmotic injury and post-operative radiological parameters. Therefore, it may be concluded that conventional radiographic diagnostic tools are not sensitive enough to reveal post-operative syndesmotic instability.

The relationship between degenerative osteoarthritis and SER type 4 ankle injuries is highly controversial. In this regard, Kortekangas et al.[23] also reported no significant difference between patients who received trans-syndesmotic fixation and those who did not. Furthermore, Blom et al.[24] claimed that accompanying posterior malleolus fracture significantly worsened functional outcomes, and they emphasized the importance of the fracture pattern rather than the fragment size. Also, in a study by Lübbeke et al.,[25] they evaluated follow-up data varying between 12 and 22 years and reported that associated dislocation is a significant factor that increases the risk of osteoarthritis. In the same manner, Dahmen et al.[26] mentioned that chondral injury occurring during the initial trauma may be a predisposing factor in subsequent osteoarthritis. In our study, although no significant difference was identified between Group 1 and Group 2 regarding the degree of ankle osteoarthritis, functional results were better in Group 1. In a magnetic resonance imaging study, Gardner et al.[27] identified that the posterior inferior tibiofibular ligament was intact in SER injuries with a posterior malleolar fragment. In a study including 31 patients, Miller et al.[28] concluded that posterior malleolus fixation was equivalent to syndesmotic fixation with an oppositional screw. However, according to our results from multivariate logistic regression analysis, we identified an increase in ankle arthritis risk by approximately 18 times in patients with posterior malleolus fragments who received trans-syndesmotic fixation but no posterior malleolus fixation. To our knowledge, our study is the first one to emphasize that fixation of small-sized posterior malleolus, regardless of a syndesmotic screw fixation, has a positive impact on ankle osteoarthritis.

Limitations: In this study comparing the patients who received trans-syndesmotic fixation and those who did not, researcher bias was not checked during the evaluation process, which could be a limitation. An independent observer to participate in the functional evaluation of patients who received trans-syndesmotic fixation might be beneficial to provide unbiased results. The quality of intraoperative tests can also indicate a limitation due to its performer-dependent nature. Moreover, lower functional scores related to the group without syndesmotic fixation might be influenced by other factors. For instance, the degree of initial chondral injury on subsequent joint arthritis could not be portrayed. Multi-center prospective studies with larger patient groups should be performed, and longer follow-up data must be obtained to achieve more conclusive results.

CONCLUSION

Median values of the OMAS, the AOFAS scoring scale, and ROM in patients without trans-syndesmotic fixation were lower. These results indicate that intraoperative tests may not provide completely correct results in SER type 4 injuries. Also, patients without posterior malleolus fixation demonstrated higher degrees of osteoarthritis. Therefore, we think that routine trans-syndesmotic fixation as well as posterior malleolus fixation in SER type 4 ankle injuries may improve outcomes.