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Bioabsorbable Versus Metallic Screw Fixation for Tibiofibular Syndesmotic Ruptures: A Meta-Analysis
The Journal of Foot & Ankle Surgery 54 (2015) 657–662
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Bioabsorbable Versus Metallic Screw Fixation for Tibiofibular Syndesmotic Ruptures: A Meta-Analysis Dorien M. van der Eng, MD 1, Niels W.L. Schep, MD, PhD, MSc 2, Tim Schepers, MD, PhD 2 1 2
Physician, Department of Surgery, Academic Medical Centre, Amsterdam, The Netherlands Trauma Surgeon, Trauma Unit, Department of Surgery, Academic Medical Centre, Amsterdam, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 1
Ankle fractures with syndesmotic rupture require operative treatment. In most cases, this consists of fixation of the tibiofibular joint with 1 or more screws. Bioabsorbable screws are used for the same purpose but have the advantage that screw removal is unnecessary. The aim of the present study was to compare the results of bioabsorbable and metallic syndesmotic screws. A systematic search was performed in the Ovid MEDLINE electronic database and Google Scholar. Three randomized controlled trials and one comparison study, with 260 patients, were included. The experimental group consisted of patients with syndesmotic injuries treated with bioabsorbable screws versus the control group (patients treated with metallic screws). The primary outcomes were complications and wound infections. No statistically significant difference was demonstrable in the overall number of complications between the 2 groups. In the group of patients with a bioabsorbable screw, 32 of 137 (23.4%) experienced a complication versus 7 of 123 patients (5.7%) with a metallic screw. Data on wound-related complications showed no statistically significant difference, 19.7% versus 5.7%. The average maximum range of motion in both groups was comparable. Bioabsorbable syndesmotic screws and metallic syndesmotic screws were comparable with respect to the incidence of complications and range of motion. However, the absolute number of complications was greater with bioabsorbable screws. Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: ankle fracture bioabsorbable screw syndesmosis syndesmotic rupture
The tibiofibular syndesmosis stabilizes the dynamic articulation between the tibia and fibula and consists of the anterior tibiofibular, posterior tibiofibular, inferior transverse ligaments, and interosseous membrane (1,2). Syndesmotic injuries disrupt the normal congruency of the ankle joint. This can lead to ankle instability, alterations in weight transmission between tibia and fibula and subsequent arthritis (3). The operative treatment of syndesmotic injuries typically consists of internal fixation with positioning screws (4,5). These screws stabilize the tibiofibular joint to establish ligament healing. They also prohibit normal tibiofibular movement; thus, some have advocated screw removal to restore normal ankle function. Understandably, the removal of the screws involves a second operation with its possible complications. To avoid the removal of hardware, bioabsorbable screws have been introduced. Bioabsorbable screws emerged in the 1980s. At first, they were made of polyglycolide acid (PGA), followed by polylactide acid Financial Disclosure: None reported. Conflict of Interest: None reported. Address correspondence to: Dorien M. van der Eng, MD, Department of Surgery, Academic Medical Centre, Meibergdreef 9, PO Box 22660, Amsterdam 1105 AZ, The Netherlands. E-mail address: [email protected] (D.M. van der Eng).
(PLA) and polylevolactic acid (PLLA). In addition to the advantage that removal is unnecessary, the slow screw resorption facilitates a gradual load on the syndesmosis (4,6,7). Moreover, these bioabsorbable screws do not interfere with radiographic imaging (8). The disadvantages include the higher purchase costs and, according to some investigators, a possible tendency toward a greater complication rate (9). The aim of the present meta-analysis was to compare the results of bioabsorbable and metallic syndesmotic screws. Our primary outcomes were the overall complication rate and the incidence of wound infections. Materials and Methods The present study was reported according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines (10). Eligibility Criteria and Search Methods The inclusion criteria were randomized controlled trials and comparative studies of adult patients with syndesmotic injuries, published in English from January 1994 to June 2014. The experimental group consisted of operative syndesmotic repair with 1 bioabsorbable screws. The control group consisted of operative syndesmotic repair with 1 metallic screws. The Ovid MEDLINE electronic database and Google Scholar were used for the published data search. A systematic search was performed with the following terms: syndesmo* (all fields) and absorbable (all fields).
1067-2516/$ - see front matter Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2015.03.014
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Outcomes Our primary outcome measurements were the overall complication rate and the incidence of wound infections. The secondary outcomes were range of motion (ROM) and functional outcome. Study Selection Two authors (D.M.E., T.S.) assessed abstracts of studies during the initial search. Full-text copies of the potentially relevant studies were assessed by the same physicians. The reference lists of these studies were also checked for relevant publications. Quality Assessment For the evaluation of the methodologic quality of the included studies, the guidelines of the Cochrane Bone, Joint and Muscle Trauma group were used. Several items, such as randomization, keeping patients and care providers unaware of the treatment choice, follow-up period, and description of outcome, were checked and points given. The quality assessment of the included studies was performed in duplicate by 2 authors (D.M.E., T.S.). Data Extraction Two authors (D.M.E., T.S.) extracted the data from all included studies. The data were extracted using a standardized data collection form that was developed according to the Cochrane guidelines. The items collected included the publication details, study type, number of patients, fracture type, outcome measures, and data on complications. Statistical Analysis The Cochrane Review Manager software, version 5.3 (RevMan, Cochrane Collaboration, London, UK) was used for data analysis. The risk ratios and 95% confidence intervals were calculated. A treatment effect was defined as significant if p .05. The random effects model was used. Heterogeneity was explored using the chi-square test, with significance set at p < .100. For quantification, I2 was used, with values <30% indicating low heterogeneity.
syndesmotic rupture. A comparison was made between 18 patients treated with a quadricortical 4.5-mm PLLA screw (Bionx Implants) and 20 patients treated with a tricortical 3.2-mm metallic screw (Synthes Holding AG). Postoperatively, all patients had a cast for 6 weeks, including 4 weeks non-weightbearing. All metallic screws were removed; however, no information was provided about the timing of implant removal. The main outcomes were the syndesmotic width measured on radiographs and computed tomography scans, ROM, and functionality using the Olerud and Molander questionnaire (12). The mean follow-up was 16 and 27 months for the PLLA and metallic screw groups, respectively. Note that the type of metal was not specified in this study. The study by Sun et al (13) included 168 patients with bi- and trimalleolar fractures or isolated fibula fractures with a talar shift. They were randomly allocated using sealed envelopes to either a 4.5-mm PLLA screw (Takiron, Tokyo, Japan) or 4.5-mm titanium alloy screw (Synthes, West Chester, PA), both tricortical. Fibular fixation plates were used in both groups if required by the fracture type. Both groups had the same regimen of partial weightbearing with a plaster splint or brace postoperatively. At 8 weeks after the initial surgery, the metallic screws were removed. The primary outcomes were active ROM, pain on compression, and Baird scores (14), and the assessors were unaware of the treatment option. The mean follow-up period was almost 56 months. In the study by Thordarson et al (15), 24 patients with a pronationlateral rotation fracture were included. Randomization between a
Funding Sources No sources of funding were used for this project.
Results Data Search The search resulted in 18 potentially eligible studies. Finally, 4 studies were included for additional analysis (Fig. 1, Table 1). A total of 260 patients were eligible for evaluation, with 137 (52.7%) treated with bioabsorbable screws and 123 (47.3%) treated with metallic screws. The 4 studies included 3 randomized controlled trials and 1 retrospective case series. Description of Included Studies Tables 1 and 2 list a more comprehensive description of the patient characteristics and the pre- and postoperative treatment protocols described in the reports included in our systematic review. The study by Kaukonen et al (11) randomized 38 patients with all types of ankle fractures using sealed envelopes. They compared 4.5 mm PLLA syndesmotic screws (Bionx Implants, Tampere, Finland) and 4.5-mm metallic screws (AO; Synthes Holding AG [formerly Synthes-Stratec], Solothurn, Switzerland), both quadricortical. All patients received similar postoperative rehabilitation protocols. All metallic screws were removed with the patient under local anesthesia at 8 weeks postoperatively or later. The outcome assessors were unaware of the treatment group. The primary outcome was the ROM; the secondary outcomes were ankle stability and joint space measurements. Ankle stability was tested manually and using radiographic follow-up studies. The mean follow-up was 35 months. Note that the type of metal was not specified in this study. Sinisaari et al (7) retrospectively compared 2 groups of consecutive patients with ankle fractures and perioperatively confirmed
Fig. 1. Flow diagram of included studies in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement.
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Table 1 Patient characteristics, study type, and outcome measures of included studies Studies
Total Patients (n)
Patients Initially Included (n) Bioabsorbable Screw
Lost to Follow-Up (%)
Patients Who Completed Follow-Up (n) Metallic Screw
Bioabsorbable Screw
Metallic Screw
Mean Age (yr)
Bioabsorbable Screw
Metallic Screw
Study Type
Primary Outcome Measures
ROM, return to previous activity, ankle stability, joint spaces ROM, OMAS, syndesmotic width
Kaukonen et al (11), 2005
40
20
20
20
18
5
43.1
45.6
Prospective RCT, single center
Sinisaari et al (7), 2002
43
20
23
18
12
30
49.4
46.6
184
92
92
86
82
39.7
37.1
32
17
15
13
11
25
34.7
24.2
Retrospective comparison, single center Prospective RCT, single center Prospective RCT, single center
299
149
150
137
123
d
d
d
Sun et al (13), 2014 Thordarson et al (15), 2001 Total
8.7
d
ROM, Baird score, pain on compression ROM, subjective complaints, fracture healing d
Abbreviations: OMAS, Olerud and Molander ankle score; RCT, randomized controlled trials; ROM, range of motion.
4.5-mm PLA screw (Bionx Implants) or a stainless steel screw was performed by sealed envelopes. Every patient underwent standard plate fixation of the fibula fracture. All the patients were kept non-weightbearing until 6 weeks postoperatively. After an average of 13.4 weeks, the stainless steel screws were removed. The main outcomes were ROM, subjective complaints, and fracture healing. The average follow-up period was 11 months.
Methodologic Quality The individual scores for each study are listed in Table 3, according to the methodologic quality evaluation guidelines of the Cochrane Bone, Joint and Muscle Trauma group. Low scores indicate poor methodologic quality.
Outcome Parameters Complications Data on the complications were reported in all 4 studies. Complications included wound infections, foreign body reactions (mild € stman and Pihlaand medium, according to the classification of Bo €ki [6]), deep infections, heterotopic ossification, arthritis foljama lowed by arthrodesis, and palpable remnants of the bioabsorbable screw, which had to be removed. No breakage or hardware failure was reported. In all 4 studies, the metallic screws were removed. None of the studies provided specific information concerning complications after the second operation. Our meta-analysis demonstrated no statistically significant difference in the overall incidence of complications. The incidence was 32 of 137 (23.4%) in the PLA/PLLA screw group versus 7 of 123 patients
Table 2 Description of the peri- and postoperative protocols and follow-up Studies
Fracture Type
Operative Protocol
Postoperative Protocol
Radiographic Imaging Studies
Follow-Up (mo)
Kaukonen et al (11), 2005; prospective RCT
Uni-, bi-, trimalleolar fracture with syndesmotic rupture
4.5-mm PLLA screw versus 4.5-mm metallic screw, 4 cortices
Radiographs: AP, lateral, 20 internal rotation; first day, 2 and 6 wk postoperatively, and at end of follow-up period
Mean 35; range, 17 to 51
Sinisaari et al (7), 2002; retrospective comparison
All ankle fractures with syndesmotic rupture
Radiographs: AP, lateral, 15 internal rotation; CT scan; radiographic follow-up imaging NR
Mean PLLA, 16; mean metallic screws, 27; range, NR
Sun et al (13), 2014; prospective RCT
Bi- and trimalleolar fracture plus unstable syndesmotic injury or isolated fibula fracture plus talar shift 1 to 2 mm
4.5-mm PLLA screw, 4 cortices versus 3.2-mm metallic screws, 3 cortices; plate fixation if required by fracture type 4.5-mm PLLA screw versus 4.5-mm titanium alloy, 3 cortices; plate fixation, if required by fracture type
Radiographs: AP, lateral, mortise view of both ankles; unknown when radiographic follow-up studies were conducted
Mean, 55.8; range, 48 to 66
Thordarson et al (15), 2001; prospective RCT
Pronation-lateral rotation fracture, 4 cm proximal to ankle joint or lower plus talar shift 1 cm
Cast for 6 wk; partial weightbearing for 4 wk, next 2 wk gradually increased to full weightbearing; standard metallic screw removal: 8 wk under local anesthesia Short plaster cast for 6 wk, first 4 wk without weightbearing; metallic screws were removed but when or how NR Splint or brace (not specified), 4 wk partial weightbearing; full weightbearing from 8 wk; CPM 30 min, twice daily, initiated on second day, for 3 days; metallic screw removal: 8 wk; plate removal on request, >1 yr Short leg cast, nonweightbearing for 6 wk, walking cast 2 wk; metallic screw removal: average 13.4 wk
Radiographs: AP, lateral, mortise view; unknown when radiographic follow-up studies were conducted
Mean, 11; range, NR
4.5-mm PLA screw versus 4.5-mm stainless steel screw, 4 cortices; plate fixation in all patients
Abbreviations: AP, anteroposterior; CPM, continuous passive motion; NR, not reported; PLA, polylactide acid; PLLA, polylevolactic acid; RCT, randomized controlled trial; ROM, range of motion.
12 1
Range of Motion Three of the four included studies reported the data concerning the active ROM (7,11,13). This was defined as the range defined by maximum dorsiflexion and the maximum plantar flexion. Sun et al (13) used a goniometer to measure the ROM. The 2 other research groups did not report how they executed this measurement. One study only described the difference in ROM between the operated and control ankles (7). All studies found that the ROM had decreased in the operated ankle compared with the unoperated ankle. The mean maximum dorsiflexion was 20.7 for the 119 patients treated with a PLA or PLLA screw. The mean maximum dorsiflexion for the 111 patients with a metallic screw was 18.2 . For maximum plantar flexion, the mean value was 40.8 and 37.7 for the PLA/PLLA and metallic groups, respectively. The mean difference between the operated and noninjured ankle for dorsiflexion was 5.1 for 124 patients treated with a PLA/PLLA screw and 6.7 for 112 patients with a metallic screw. For plantar flexion, the difference was 4.2 versus 9.0 for 106 patients with PLA/ PLLA screws and 100 patients with metallic screws, respectively.
2 0
2
2
1*
17 2 2 0
2
2
2
11 2 2 2 0
0
2
2 2 2 0
0
2
Adequate Length of Active Follow-Up Clear Outcome Measures
0 No standard deviation or 95% confidence interval reported.
1 1 2/Sealed envelope
0
0 2 1 2/Sealed envelope
2
0 2 1 0
0
0 2 2 1 2/Sealed envelope
Kaukonen et al (11), 2005 Sinisaari et al (7), 2002 Sun et al (13), 2014 Thordarson et al (15), 2001
*
Interventions Clearly Defined Clear Inclusion/ Exclusion Criteria Care Programs Identical Providers Blinded to Assignment Patients Blinded to Assignment Comparable Treatment Groups Outcome Assessors Blinded to Treatment Randomization/ Allocation Concealment
Intention to Treat
(5.7%) with a metallic screw. The risk ratio was 2.20 (95% confidence interval 0.39 to 12.46, p ¼ .37, I2 ¼ 63%; Fig. 2A) A subgroup analysis of PLLA versus metallic screws showed a significant difference. When the PLA group is excluded, the risk ratio increased to 5.35 in favor of the metallic screws (95% confidence interval 1.89 to 15.14, p ¼ .002, I2 ¼ 9%; Fig. 2B). An analysis of wound-related complications only showed no significant differences. The incidence was 27 of 137 patients (19.7%) compared with 7 of 123 patients with a PLA/PLLA screw and a metallic screw, respectively, with a risk ratio of 1.26 (95% confidence interval 0.14 to 11.41, p ¼ .84, I2 ¼ 71%). Exclusion of the PLA group did not alter the level of significance nor heterogeneity (risk ratio 2.00, p ¼ .64, I2 ¼ 69%).
Functional and Patient-Related Outcome Scores
Factors Affecting Quality/Studies
Table 3 Scores for methodologic quality for each included study according to evaluation guidelines of the Cochrane Bone, Joint, and Muscle Trauma Group
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Total (maximum 22 points)
660
Sinisaari et al (7) provided information about subjective outcomes with the Olerud and Molander questionnaire (12). In this scoring system, 0 points indicates “totally impaired function” and 100 points, “completely unimpaired function.” The PLLA group scored 82 points (good) versus 90 points (good) in the metallic group. The difference in the score of patients treated with PLLA screws compared with patients with metallic screws was not significant (p ¼ .93). Sun et al (13) used the Baird score (14) in which the objective and subjective outcomes together are evaluated. Patients in the PLLA screw group reported a score of 97 points (excellent), and the metallic screw group reported a score of 90 points (fair). This difference was not significant (p ¼ .095). The interquartile range in the PLLA screw group was 80.0 to 100 compared with 77.0 to 100.0 in the metallic screw group. In 1 study, the investigators reported that patients completed a questionnaire during the follow-up period. All patients stated they were satisfied with their surgery but no score or more comprehensive clarification was provided (15).
Fracture Healing No specific data were available regarding syndesmotic healing. All included studies reported that healing was uncomplicated, and no signs of syndesmotic instability were found.
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Fig. 2. (A) Table and forest plot illustrating the number of complications. (B) Table and forest plot illustrating the number of complications solely in the polylevolactic acid (PLLA) versus the metallic screw groups.
Discussion We found no significant differences in the incidence of complications between the patients treated with a PLA/PLLA screw and the patients treated with a metallic screw. However, in the bioabsorbable group, almost 1 in 4 patients experienced a complication compared with 1 in 16 patients in the metallic group. It is very well possible that this difference was not statistically significant owing to underpowering of the included studies. When only PLLA screws and metallic screws were compared, the difference becomes significant, with a low heterogeneity score. The explanation for this might have been the small number of patients, differences in the inclusion criteria with regard to fracture type, and the standard use of plate fixation in the study by Thordarson et al (15) (Table 2). Most complications were wound-related problems. In the group of patients with metallic screws, only wound-related complications developed. One out of 5 patients treated with a bioabsorbable screw deals with wound-related problems or foreign body reactions. The statistical heterogeneity was 71% for our results regarding woundrelated complications. One reason for this heterogeneity could have been the low number of included studies and the differences in the number of included patients. The study with the greatest number of events also had the largest number of patients. However, it was surprising that the only major complication, arthrodesis after purulent arthritis, occurred in the group with metallic screws. The complication percentage in the bioabsorbable group mainly resulted from the inclusion of the study by Sun et al (13), with a weight of 45% and an incidence of complications of 34% in the PLLA group. The complications in the other 3 included studies was 0% to 10%. Two noncomparative studies and one review described the satisfying results of bioabsorbable screws in terms of functional scores, complications, stability, and complications (4,9,16). Wang et al (9) found a 5.2% complication rate in 77 patients with bioabsorbable screws compared with 4.3% in 70 patients with metallic screws. The other studies reported no complications at all (4,16). In the past, rapidly degrading PGA screws were associated with delayed inflammatory reactions, foreign body reaction, formation of a
sinus, tract, or fistula, and osteolysis. The incidence of complications ranged from 5% to 10%. (17). It has been theorized that these reactions resulted from the rate of hydrolysis; a PGA screw is hydrolyzed in approximately 4 weeks after implantation (4,11,15). None of the studies included in our meta-analysis used this type of screw. In contrast to the PGA screws, the PLA and PLLA screws lose their mechanical resistance over a period of 3 months to 1 year, in vivo (18). In vitro tests have shown that PLLA degrades slower than PLA and becomes more brittle and fragment more extensively after prolonged degradation (19). Sun et al (13) reported 26 foreign body reactions in the patients included in their study. The other 3 studies did not report these €stman and Pihlajama €ki (6) pubcomplications (7,11,15). In 2000, Bo lished data concerning 2528 patients who were treated using bioabsorbable pins, rods, and screws. Of the patients with a PGA screw, 5.3% had a soft tissue reaction compared with 0.2% with a PLA screw. The average maximum ROM of both dorsiflexion and plantar flexion in the present meta-analysis was comparable to that of other studies. All included studies reported that the ROM had decreased in the operated ankle compared with the other ankle. The average difference in dorsi- and plantar flexion compared with the uninjured ankle was also comparable to that reported in previous studies (16,20). In addition, the rigid fixation of the syndesmosis caused by syndesmotic screws decreases normal tibiofibular movements and mortise widening (21,22). We were unable to obtain the original data sets, because these were no longer available from the research groups. Therefore, it was not possible to execute pooling to assess whether a significant difference was demonstrable regarding the ROM. Controversy exists concerning screw removal of metallic syndesmotic screws. Because the screw alters the normal tibiofibular movements, some believe it is better to remove it. Also, when patients start to bear weight, screw breakage is a possibility (8,22). In all the included studies, the metallic screws were removed. To remove the screw, patients must undergo a second operation, with the associated risks of complications, such as wound infections and recurrent diastasis or even stress fractures (22).
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Tucker et al (2) found a better functional outcome in 20 patients in whom the metallic syndesmotic screws were not removed compared with 43 patients with screw removal. In the group with the screw retained, 95% described their ankle function as good or better compared with 81.4% of those who had undergone screw removed. However, the difference in the mean Olerud and Molander ankle score was not statistically significant. A recent review found several contradicting results comparing intact and removed screws with respect to the functional outcomes. Some researchers found a better outcome when the screw was removed. In contrast, others described a better or similar function with the screw in situ, broken, loosened, or intact (22). The review by Schepers (23) found comparable results for retained or removed screws from 6 studies. One study included in the review by Schepers had better outcome results for broken screws (21). Evidence with regard to wound infection after syndesmotic screw removal is very scarce. In a retrospective study, the percentage varied from 6.6% to 10.3% (24). However, the subject of hardware removal was beyond the scope of the present meta-analysis. Nevertheless, it is an import factor to consider when criticizing different treatment options. Despite the prevalence of routine removal of the syndesmotic screws, no evidence was found to support this practice (1,2,9,22). Relatively recently, new suture button implants were developed and seemed to gain popularity. The use of these devices was not evaluated in our meta-analysis; however, this is an interesting topic for future research (25). Study Limitations The number of randomized controlled trials within the present meta-analysis was small, because in general the availability of randomized studies about this subject is scarce. We, however, believe that there is little evidence to support publication bias. A thorough search was performed identifying all available studies. It is unknown whether unpublished studies were performed. Apparently the use of bioabsorbable screws has been limited throughout the years. Moreover, 3 of 4 included studies had relatively small sample sizes. Our analysis showed the differences between the 2 groups. However, these differences were not significant, although the incidence of complications seems to be less in patients treated with metallic screws. The small sample sizes can cause underpowering of the findings presented in our meta-analysis. Moreover, 1 study had only a mean follow-up period of 11 months; thus, it might be possible that after this period more adverse events had occurred. In 1 of the studies, no complications were reported after a mean follow-up period of 16 months for patients with PLLA screws and 27 months for patients with metallic screws. All patients in that study were included. However, no events were reported; thus, that particular study was not included in the calculations of the complication rates. The quality of the included studies was generally acceptable. The groups of patients included in both arms of the studies were comparable. Most studies stated clear inclusion and exclusion criteria, and their operative and postoperative protocols were similar for patients of the PLA/PLLA and metallic screw groups (Tables 2 and 3). The purchase costs of the bioabsorbable screws were higher than the purchase costs of the metallic screws. However, none of the included studies provided a cost analysis. One must remember to consider that removal of metallic screws requires a second operation, causing the need for absence from work and potential costly complications (26). In conclusion, we have demonstrated that bioabsorbable syndesmotic screws and metallic syndesmotic screws are comparable with the respect to the complication rate and ROM. However, the absolute number of complications was greater with the use of bioabsorbable screws. The comparison solely between PLLA and metallic
screws showed a significant difference regarding complications in favor of the metallic screws. During the past years, the treatment of syndesmotic injuries has changed frequently. With new evidence showing that routine removal of the metallic screws is not beneficial, bioabsorbable screws seem to have no advantages. References 1. Schepers T, van der Linden H, van Lieshout EM, Niesten DD, van der Elst M. Technical aspects of the syndesmotic screw and their effect on functional outcome following acute distal tibiofibular syndesmosis injury. Injury 45:775–779, 2014. 2. Tucker A, Street J, Kealey D, McDonald S, Stevenson M. Functional outcomes following syndesmotic fixation: a comparison of screws retained in situ versus routine removaldis it really necessary? Injury 44:1880–1884, 2013. 3. van den Bekerom MP, Hogervorst M, Bolhuis HW, van Dijk CN. Operative aspects of the syndesmotic screw: review of current concepts. Injury 39:491–498, 2008. 4. Ahmad J, Raikin SM, Pour AE, Haytmanek C. 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Bioabsorbable Versus Metallic Screw Fixation for Tibiofibular Syndesmotic Ruptures: A Meta-Analysis Dorien M. van der Eng, MD 1, Niels W.L. Schep, MD, PhD, MSc 2, Tim Schepers, MD, PhD 2 1 2
Physician, Department of Surgery, Academic Medical Centre, Amsterdam, The Netherlands Trauma Surgeon, Trauma Unit, Department of Surgery, Academic Medical Centre, Amsterdam, The Netherlands
a r t i c l e i n f o
a b s t r a c t
Level of Clinical Evidence: 1
Ankle fractures with syndesmotic rupture require operative treatment. In most cases, this consists of fixation of the tibiofibular joint with 1 or more screws. Bioabsorbable screws are used for the same purpose but have the advantage that screw removal is unnecessary. The aim of the present study was to compare the results of bioabsorbable and metallic syndesmotic screws. A systematic search was performed in the Ovid MEDLINE electronic database and Google Scholar. Three randomized controlled trials and one comparison study, with 260 patients, were included. The experimental group consisted of patients with syndesmotic injuries treated with bioabsorbable screws versus the control group (patients treated with metallic screws). The primary outcomes were complications and wound infections. No statistically significant difference was demonstrable in the overall number of complications between the 2 groups. In the group of patients with a bioabsorbable screw, 32 of 137 (23.4%) experienced a complication versus 7 of 123 patients (5.7%) with a metallic screw. Data on wound-related complications showed no statistically significant difference, 19.7% versus 5.7%. The average maximum range of motion in both groups was comparable. Bioabsorbable syndesmotic screws and metallic syndesmotic screws were comparable with respect to the incidence of complications and range of motion. However, the absolute number of complications was greater with bioabsorbable screws. Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved.
Keywords: ankle fracture bioabsorbable screw syndesmosis syndesmotic rupture
The tibiofibular syndesmosis stabilizes the dynamic articulation between the tibia and fibula and consists of the anterior tibiofibular, posterior tibiofibular, inferior transverse ligaments, and interosseous membrane (1,2). Syndesmotic injuries disrupt the normal congruency of the ankle joint. This can lead to ankle instability, alterations in weight transmission between tibia and fibula and subsequent arthritis (3). The operative treatment of syndesmotic injuries typically consists of internal fixation with positioning screws (4,5). These screws stabilize the tibiofibular joint to establish ligament healing. They also prohibit normal tibiofibular movement; thus, some have advocated screw removal to restore normal ankle function. Understandably, the removal of the screws involves a second operation with its possible complications. To avoid the removal of hardware, bioabsorbable screws have been introduced. Bioabsorbable screws emerged in the 1980s. At first, they were made of polyglycolide acid (PGA), followed by polylactide acid Financial Disclosure: None reported. Conflict of Interest: None reported. Address correspondence to: Dorien M. van der Eng, MD, Department of Surgery, Academic Medical Centre, Meibergdreef 9, PO Box 22660, Amsterdam 1105 AZ, The Netherlands. E-mail address: [email protected] (D.M. van der Eng).
(PLA) and polylevolactic acid (PLLA). In addition to the advantage that removal is unnecessary, the slow screw resorption facilitates a gradual load on the syndesmosis (4,6,7). Moreover, these bioabsorbable screws do not interfere with radiographic imaging (8). The disadvantages include the higher purchase costs and, according to some investigators, a possible tendency toward a greater complication rate (9). The aim of the present meta-analysis was to compare the results of bioabsorbable and metallic syndesmotic screws. Our primary outcomes were the overall complication rate and the incidence of wound infections. Materials and Methods The present study was reported according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses guidelines (10). Eligibility Criteria and Search Methods The inclusion criteria were randomized controlled trials and comparative studies of adult patients with syndesmotic injuries, published in English from January 1994 to June 2014. The experimental group consisted of operative syndesmotic repair with 1 bioabsorbable screws. The control group consisted of operative syndesmotic repair with 1 metallic screws. The Ovid MEDLINE electronic database and Google Scholar were used for the published data search. A systematic search was performed with the following terms: syndesmo* (all fields) and absorbable (all fields).
1067-2516/$ - see front matter Ó 2015 by the American College of Foot and Ankle Surgeons. All rights reserved. http://dx.doi.org/10.1053/j.jfas.2015.03.014
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Outcomes Our primary outcome measurements were the overall complication rate and the incidence of wound infections. The secondary outcomes were range of motion (ROM) and functional outcome. Study Selection Two authors (D.M.E., T.S.) assessed abstracts of studies during the initial search. Full-text copies of the potentially relevant studies were assessed by the same physicians. The reference lists of these studies were also checked for relevant publications. Quality Assessment For the evaluation of the methodologic quality of the included studies, the guidelines of the Cochrane Bone, Joint and Muscle Trauma group were used. Several items, such as randomization, keeping patients and care providers unaware of the treatment choice, follow-up period, and description of outcome, were checked and points given. The quality assessment of the included studies was performed in duplicate by 2 authors (D.M.E., T.S.). Data Extraction Two authors (D.M.E., T.S.) extracted the data from all included studies. The data were extracted using a standardized data collection form that was developed according to the Cochrane guidelines. The items collected included the publication details, study type, number of patients, fracture type, outcome measures, and data on complications. Statistical Analysis The Cochrane Review Manager software, version 5.3 (RevMan, Cochrane Collaboration, London, UK) was used for data analysis. The risk ratios and 95% confidence intervals were calculated. A treatment effect was defined as significant if p .05. The random effects model was used. Heterogeneity was explored using the chi-square test, with significance set at p < .100. For quantification, I2 was used, with values <30% indicating low heterogeneity.
syndesmotic rupture. A comparison was made between 18 patients treated with a quadricortical 4.5-mm PLLA screw (Bionx Implants) and 20 patients treated with a tricortical 3.2-mm metallic screw (Synthes Holding AG). Postoperatively, all patients had a cast for 6 weeks, including 4 weeks non-weightbearing. All metallic screws were removed; however, no information was provided about the timing of implant removal. The main outcomes were the syndesmotic width measured on radiographs and computed tomography scans, ROM, and functionality using the Olerud and Molander questionnaire (12). The mean follow-up was 16 and 27 months for the PLLA and metallic screw groups, respectively. Note that the type of metal was not specified in this study. The study by Sun et al (13) included 168 patients with bi- and trimalleolar fractures or isolated fibula fractures with a talar shift. They were randomly allocated using sealed envelopes to either a 4.5-mm PLLA screw (Takiron, Tokyo, Japan) or 4.5-mm titanium alloy screw (Synthes, West Chester, PA), both tricortical. Fibular fixation plates were used in both groups if required by the fracture type. Both groups had the same regimen of partial weightbearing with a plaster splint or brace postoperatively. At 8 weeks after the initial surgery, the metallic screws were removed. The primary outcomes were active ROM, pain on compression, and Baird scores (14), and the assessors were unaware of the treatment option. The mean follow-up period was almost 56 months. In the study by Thordarson et al (15), 24 patients with a pronationlateral rotation fracture were included. Randomization between a
Funding Sources No sources of funding were used for this project.
Results Data Search The search resulted in 18 potentially eligible studies. Finally, 4 studies were included for additional analysis (Fig. 1, Table 1). A total of 260 patients were eligible for evaluation, with 137 (52.7%) treated with bioabsorbable screws and 123 (47.3%) treated with metallic screws. The 4 studies included 3 randomized controlled trials and 1 retrospective case series. Description of Included Studies Tables 1 and 2 list a more comprehensive description of the patient characteristics and the pre- and postoperative treatment protocols described in the reports included in our systematic review. The study by Kaukonen et al (11) randomized 38 patients with all types of ankle fractures using sealed envelopes. They compared 4.5 mm PLLA syndesmotic screws (Bionx Implants, Tampere, Finland) and 4.5-mm metallic screws (AO; Synthes Holding AG [formerly Synthes-Stratec], Solothurn, Switzerland), both quadricortical. All patients received similar postoperative rehabilitation protocols. All metallic screws were removed with the patient under local anesthesia at 8 weeks postoperatively or later. The outcome assessors were unaware of the treatment group. The primary outcome was the ROM; the secondary outcomes were ankle stability and joint space measurements. Ankle stability was tested manually and using radiographic follow-up studies. The mean follow-up was 35 months. Note that the type of metal was not specified in this study. Sinisaari et al (7) retrospectively compared 2 groups of consecutive patients with ankle fractures and perioperatively confirmed
Fig. 1. Flow diagram of included studies in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses statement.
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Table 1 Patient characteristics, study type, and outcome measures of included studies Studies
Total Patients (n)
Patients Initially Included (n) Bioabsorbable Screw
Lost to Follow-Up (%)
Patients Who Completed Follow-Up (n) Metallic Screw
Bioabsorbable Screw
Metallic Screw
Mean Age (yr)
Bioabsorbable Screw
Metallic Screw
Study Type
Primary Outcome Measures
ROM, return to previous activity, ankle stability, joint spaces ROM, OMAS, syndesmotic width
Kaukonen et al (11), 2005
40
20
20
20
18
5
43.1
45.6
Prospective RCT, single center
Sinisaari et al (7), 2002
43
20
23
18
12
30
49.4
46.6
184
92
92
86
82
39.7
37.1
32
17
15
13
11
25
34.7
24.2
Retrospective comparison, single center Prospective RCT, single center Prospective RCT, single center
299
149
150
137
123
d
d
d
Sun et al (13), 2014 Thordarson et al (15), 2001 Total
8.7
d
ROM, Baird score, pain on compression ROM, subjective complaints, fracture healing d
Abbreviations: OMAS, Olerud and Molander ankle score; RCT, randomized controlled trials; ROM, range of motion.
4.5-mm PLA screw (Bionx Implants) or a stainless steel screw was performed by sealed envelopes. Every patient underwent standard plate fixation of the fibula fracture. All the patients were kept non-weightbearing until 6 weeks postoperatively. After an average of 13.4 weeks, the stainless steel screws were removed. The main outcomes were ROM, subjective complaints, and fracture healing. The average follow-up period was 11 months.
Methodologic Quality The individual scores for each study are listed in Table 3, according to the methodologic quality evaluation guidelines of the Cochrane Bone, Joint and Muscle Trauma group. Low scores indicate poor methodologic quality.
Outcome Parameters Complications Data on the complications were reported in all 4 studies. Complications included wound infections, foreign body reactions (mild € stman and Pihlaand medium, according to the classification of Bo €ki [6]), deep infections, heterotopic ossification, arthritis foljama lowed by arthrodesis, and palpable remnants of the bioabsorbable screw, which had to be removed. No breakage or hardware failure was reported. In all 4 studies, the metallic screws were removed. None of the studies provided specific information concerning complications after the second operation. Our meta-analysis demonstrated no statistically significant difference in the overall incidence of complications. The incidence was 32 of 137 (23.4%) in the PLA/PLLA screw group versus 7 of 123 patients
Table 2 Description of the peri- and postoperative protocols and follow-up Studies
Fracture Type
Operative Protocol
Postoperative Protocol
Radiographic Imaging Studies
Follow-Up (mo)
Kaukonen et al (11), 2005; prospective RCT
Uni-, bi-, trimalleolar fracture with syndesmotic rupture
4.5-mm PLLA screw versus 4.5-mm metallic screw, 4 cortices
Radiographs: AP, lateral, 20 internal rotation; first day, 2 and 6 wk postoperatively, and at end of follow-up period
Mean 35; range, 17 to 51
Sinisaari et al (7), 2002; retrospective comparison
All ankle fractures with syndesmotic rupture
Radiographs: AP, lateral, 15 internal rotation; CT scan; radiographic follow-up imaging NR
Mean PLLA, 16; mean metallic screws, 27; range, NR
Sun et al (13), 2014; prospective RCT
Bi- and trimalleolar fracture plus unstable syndesmotic injury or isolated fibula fracture plus talar shift 1 to 2 mm
4.5-mm PLLA screw, 4 cortices versus 3.2-mm metallic screws, 3 cortices; plate fixation if required by fracture type 4.5-mm PLLA screw versus 4.5-mm titanium alloy, 3 cortices; plate fixation, if required by fracture type
Radiographs: AP, lateral, mortise view of both ankles; unknown when radiographic follow-up studies were conducted
Mean, 55.8; range, 48 to 66
Thordarson et al (15), 2001; prospective RCT
Pronation-lateral rotation fracture, 4 cm proximal to ankle joint or lower plus talar shift 1 cm
Cast for 6 wk; partial weightbearing for 4 wk, next 2 wk gradually increased to full weightbearing; standard metallic screw removal: 8 wk under local anesthesia Short plaster cast for 6 wk, first 4 wk without weightbearing; metallic screws were removed but when or how NR Splint or brace (not specified), 4 wk partial weightbearing; full weightbearing from 8 wk; CPM 30 min, twice daily, initiated on second day, for 3 days; metallic screw removal: 8 wk; plate removal on request, >1 yr Short leg cast, nonweightbearing for 6 wk, walking cast 2 wk; metallic screw removal: average 13.4 wk
Radiographs: AP, lateral, mortise view; unknown when radiographic follow-up studies were conducted
Mean, 11; range, NR
4.5-mm PLA screw versus 4.5-mm stainless steel screw, 4 cortices; plate fixation in all patients
Abbreviations: AP, anteroposterior; CPM, continuous passive motion; NR, not reported; PLA, polylactide acid; PLLA, polylevolactic acid; RCT, randomized controlled trial; ROM, range of motion.
12 1
Range of Motion Three of the four included studies reported the data concerning the active ROM (7,11,13). This was defined as the range defined by maximum dorsiflexion and the maximum plantar flexion. Sun et al (13) used a goniometer to measure the ROM. The 2 other research groups did not report how they executed this measurement. One study only described the difference in ROM between the operated and control ankles (7). All studies found that the ROM had decreased in the operated ankle compared with the unoperated ankle. The mean maximum dorsiflexion was 20.7 for the 119 patients treated with a PLA or PLLA screw. The mean maximum dorsiflexion for the 111 patients with a metallic screw was 18.2 . For maximum plantar flexion, the mean value was 40.8 and 37.7 for the PLA/PLLA and metallic groups, respectively. The mean difference between the operated and noninjured ankle for dorsiflexion was 5.1 for 124 patients treated with a PLA/PLLA screw and 6.7 for 112 patients with a metallic screw. For plantar flexion, the difference was 4.2 versus 9.0 for 106 patients with PLA/ PLLA screws and 100 patients with metallic screws, respectively.
2 0
2
2
1*
17 2 2 0
2
2
2
11 2 2 2 0
0
2
2 2 2 0
0
2
Adequate Length of Active Follow-Up Clear Outcome Measures
0 No standard deviation or 95% confidence interval reported.
1 1 2/Sealed envelope
0
0 2 1 2/Sealed envelope
2
0 2 1 0
0
0 2 2 1 2/Sealed envelope
Kaukonen et al (11), 2005 Sinisaari et al (7), 2002 Sun et al (13), 2014 Thordarson et al (15), 2001
*
Interventions Clearly Defined Clear Inclusion/ Exclusion Criteria Care Programs Identical Providers Blinded to Assignment Patients Blinded to Assignment Comparable Treatment Groups Outcome Assessors Blinded to Treatment Randomization/ Allocation Concealment
Intention to Treat
(5.7%) with a metallic screw. The risk ratio was 2.20 (95% confidence interval 0.39 to 12.46, p ¼ .37, I2 ¼ 63%; Fig. 2A) A subgroup analysis of PLLA versus metallic screws showed a significant difference. When the PLA group is excluded, the risk ratio increased to 5.35 in favor of the metallic screws (95% confidence interval 1.89 to 15.14, p ¼ .002, I2 ¼ 9%; Fig. 2B). An analysis of wound-related complications only showed no significant differences. The incidence was 27 of 137 patients (19.7%) compared with 7 of 123 patients with a PLA/PLLA screw and a metallic screw, respectively, with a risk ratio of 1.26 (95% confidence interval 0.14 to 11.41, p ¼ .84, I2 ¼ 71%). Exclusion of the PLA group did not alter the level of significance nor heterogeneity (risk ratio 2.00, p ¼ .64, I2 ¼ 69%).
Functional and Patient-Related Outcome Scores
Factors Affecting Quality/Studies
Table 3 Scores for methodologic quality for each included study according to evaluation guidelines of the Cochrane Bone, Joint, and Muscle Trauma Group
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Total (maximum 22 points)
660
Sinisaari et al (7) provided information about subjective outcomes with the Olerud and Molander questionnaire (12). In this scoring system, 0 points indicates “totally impaired function” and 100 points, “completely unimpaired function.” The PLLA group scored 82 points (good) versus 90 points (good) in the metallic group. The difference in the score of patients treated with PLLA screws compared with patients with metallic screws was not significant (p ¼ .93). Sun et al (13) used the Baird score (14) in which the objective and subjective outcomes together are evaluated. Patients in the PLLA screw group reported a score of 97 points (excellent), and the metallic screw group reported a score of 90 points (fair). This difference was not significant (p ¼ .095). The interquartile range in the PLLA screw group was 80.0 to 100 compared with 77.0 to 100.0 in the metallic screw group. In 1 study, the investigators reported that patients completed a questionnaire during the follow-up period. All patients stated they were satisfied with their surgery but no score or more comprehensive clarification was provided (15).
Fracture Healing No specific data were available regarding syndesmotic healing. All included studies reported that healing was uncomplicated, and no signs of syndesmotic instability were found.
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Fig. 2. (A) Table and forest plot illustrating the number of complications. (B) Table and forest plot illustrating the number of complications solely in the polylevolactic acid (PLLA) versus the metallic screw groups.
Discussion We found no significant differences in the incidence of complications between the patients treated with a PLA/PLLA screw and the patients treated with a metallic screw. However, in the bioabsorbable group, almost 1 in 4 patients experienced a complication compared with 1 in 16 patients in the metallic group. It is very well possible that this difference was not statistically significant owing to underpowering of the included studies. When only PLLA screws and metallic screws were compared, the difference becomes significant, with a low heterogeneity score. The explanation for this might have been the small number of patients, differences in the inclusion criteria with regard to fracture type, and the standard use of plate fixation in the study by Thordarson et al (15) (Table 2). Most complications were wound-related problems. In the group of patients with metallic screws, only wound-related complications developed. One out of 5 patients treated with a bioabsorbable screw deals with wound-related problems or foreign body reactions. The statistical heterogeneity was 71% for our results regarding woundrelated complications. One reason for this heterogeneity could have been the low number of included studies and the differences in the number of included patients. The study with the greatest number of events also had the largest number of patients. However, it was surprising that the only major complication, arthrodesis after purulent arthritis, occurred in the group with metallic screws. The complication percentage in the bioabsorbable group mainly resulted from the inclusion of the study by Sun et al (13), with a weight of 45% and an incidence of complications of 34% in the PLLA group. The complications in the other 3 included studies was 0% to 10%. Two noncomparative studies and one review described the satisfying results of bioabsorbable screws in terms of functional scores, complications, stability, and complications (4,9,16). Wang et al (9) found a 5.2% complication rate in 77 patients with bioabsorbable screws compared with 4.3% in 70 patients with metallic screws. The other studies reported no complications at all (4,16). In the past, rapidly degrading PGA screws were associated with delayed inflammatory reactions, foreign body reaction, formation of a
sinus, tract, or fistula, and osteolysis. The incidence of complications ranged from 5% to 10%. (17). It has been theorized that these reactions resulted from the rate of hydrolysis; a PGA screw is hydrolyzed in approximately 4 weeks after implantation (4,11,15). None of the studies included in our meta-analysis used this type of screw. In contrast to the PGA screws, the PLA and PLLA screws lose their mechanical resistance over a period of 3 months to 1 year, in vivo (18). In vitro tests have shown that PLLA degrades slower than PLA and becomes more brittle and fragment more extensively after prolonged degradation (19). Sun et al (13) reported 26 foreign body reactions in the patients included in their study. The other 3 studies did not report these €stman and Pihlajama €ki (6) pubcomplications (7,11,15). In 2000, Bo lished data concerning 2528 patients who were treated using bioabsorbable pins, rods, and screws. Of the patients with a PGA screw, 5.3% had a soft tissue reaction compared with 0.2% with a PLA screw. The average maximum ROM of both dorsiflexion and plantar flexion in the present meta-analysis was comparable to that of other studies. All included studies reported that the ROM had decreased in the operated ankle compared with the other ankle. The average difference in dorsi- and plantar flexion compared with the uninjured ankle was also comparable to that reported in previous studies (16,20). In addition, the rigid fixation of the syndesmosis caused by syndesmotic screws decreases normal tibiofibular movements and mortise widening (21,22). We were unable to obtain the original data sets, because these were no longer available from the research groups. Therefore, it was not possible to execute pooling to assess whether a significant difference was demonstrable regarding the ROM. Controversy exists concerning screw removal of metallic syndesmotic screws. Because the screw alters the normal tibiofibular movements, some believe it is better to remove it. Also, when patients start to bear weight, screw breakage is a possibility (8,22). In all the included studies, the metallic screws were removed. To remove the screw, patients must undergo a second operation, with the associated risks of complications, such as wound infections and recurrent diastasis or even stress fractures (22).
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Tucker et al (2) found a better functional outcome in 20 patients in whom the metallic syndesmotic screws were not removed compared with 43 patients with screw removal. In the group with the screw retained, 95% described their ankle function as good or better compared with 81.4% of those who had undergone screw removed. However, the difference in the mean Olerud and Molander ankle score was not statistically significant. A recent review found several contradicting results comparing intact and removed screws with respect to the functional outcomes. Some researchers found a better outcome when the screw was removed. In contrast, others described a better or similar function with the screw in situ, broken, loosened, or intact (22). The review by Schepers (23) found comparable results for retained or removed screws from 6 studies. One study included in the review by Schepers had better outcome results for broken screws (21). Evidence with regard to wound infection after syndesmotic screw removal is very scarce. In a retrospective study, the percentage varied from 6.6% to 10.3% (24). However, the subject of hardware removal was beyond the scope of the present meta-analysis. Nevertheless, it is an import factor to consider when criticizing different treatment options. Despite the prevalence of routine removal of the syndesmotic screws, no evidence was found to support this practice (1,2,9,22). Relatively recently, new suture button implants were developed and seemed to gain popularity. The use of these devices was not evaluated in our meta-analysis; however, this is an interesting topic for future research (25). Study Limitations The number of randomized controlled trials within the present meta-analysis was small, because in general the availability of randomized studies about this subject is scarce. We, however, believe that there is little evidence to support publication bias. A thorough search was performed identifying all available studies. It is unknown whether unpublished studies were performed. Apparently the use of bioabsorbable screws has been limited throughout the years. Moreover, 3 of 4 included studies had relatively small sample sizes. Our analysis showed the differences between the 2 groups. However, these differences were not significant, although the incidence of complications seems to be less in patients treated with metallic screws. The small sample sizes can cause underpowering of the findings presented in our meta-analysis. Moreover, 1 study had only a mean follow-up period of 11 months; thus, it might be possible that after this period more adverse events had occurred. In 1 of the studies, no complications were reported after a mean follow-up period of 16 months for patients with PLLA screws and 27 months for patients with metallic screws. All patients in that study were included. However, no events were reported; thus, that particular study was not included in the calculations of the complication rates. The quality of the included studies was generally acceptable. The groups of patients included in both arms of the studies were comparable. Most studies stated clear inclusion and exclusion criteria, and their operative and postoperative protocols were similar for patients of the PLA/PLLA and metallic screw groups (Tables 2 and 3). The purchase costs of the bioabsorbable screws were higher than the purchase costs of the metallic screws. However, none of the included studies provided a cost analysis. One must remember to consider that removal of metallic screws requires a second operation, causing the need for absence from work and potential costly complications (26). In conclusion, we have demonstrated that bioabsorbable syndesmotic screws and metallic syndesmotic screws are comparable with the respect to the complication rate and ROM. However, the absolute number of complications was greater with the use of bioabsorbable screws. The comparison solely between PLLA and metallic
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