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Unstable ankle fractures: Better clinical results with metal versus biodegradable implants
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May 2013
Unstable ankle fractures: Better clinical results with metal versus biodegradable implants
Study Type:Therapy
OE Level Evidence:2
Journal Level of Evidence:N/A
Outcomes of operative treatment of unstable ankle fractures: a comparison of metallic and biodegradable implants
J Bone Joint Surg Am. 2012 Nov 21;94(22):e1661-7. doi: 10.2106/JBJS.K.01221Did you know you're eligible to earn 0.5 CME credits for reading this report? Click Here
Synopsis
109 patients with unstable ankle fractures, requiring surgical intervention, were included in this study to compare clinical outcomes of metal and biodegradable implant fixations. Patients who underwent fixation using a metal implant had a shorter mean operative time, required less time to bone union, and had superior American Orthopaedic Foot and Ankle Society ankle-hindfoot scale scores at 12 months. Patients in the metal implant group also had fewer non-unions when compared to the biodegradable implants; however, this difference was not significant.
Publication Funding Details
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Funding:
Non-funded
Conflicts:
None disclosed
Was the allocation sequence adequately generated?
Was allocation adequately concealed?
Blinding Treatment Providers: Was knowledge of the allocated interventions adequately prevented?
Blinding Outcome Assessors: Was knowledge of the allocated interventions adequately prevented?
Blinding Patients: Was knowledge of the allocated interventions adequately prevented?
Was loss to follow-up (missing outcome data) infrequent?
Are reports of the study free of suggestion of selective outcome reporting?
Were outcomes objective, patient-important and assessed in a manner to limit bias (ie. duplicate assessors, Independent assessors)?
Was the sample size sufficiently large to assure a balance of prognosis and sufficiently large number of outcome events?
Was investigator expertise/experience with both treatment and control techniques likely the same (ie.were criteria for surgeon participation/expertise provided)?
Yes = 1
Uncertain = 0.5
Not Relevant = 0
No = 0
The Reporting Criteria Assessment evaluates the transparency with which authors report the methodological and trial characteristics of the trial within the publication. The assessment is divided into five categories which are presented below.
2/4
Randomization
2/4
Outcome Measurements
4/4
Inclusion / Exclusion
4/4
Therapy Description
4/4
Statistics
Detsky AS, Naylor CD, O'Rourke K, McGeer AJ, L'Abbé KA. J Clin Epidemiol. 1992;45:255-65
The Fragility Index is a tool that aids in the interpretation of significant findings, providing a measure of strength for a result. The Fragility Index represents the number of consecutive events that need to be added to a dichotomous outcome to make the finding no longer significant. A small number represents a weaker finding and a large number represents a stronger finding.
Why was this study needed now?
Due to the complexity of displaced ankle fractures surgical reduction and fixation are required to ensure the best functional recovery. Metallic implants are often used to provide adequate stability; however, metallic implants have a number of theoretical and practical disadvantages, including stress shielding and the need for possible secondary operations to remove the implant. The use of biodegradable implants, as an alternative for internal fixator for ankle fractures, was introduced in the 1980's, and the advent of new technologies have led to the development of numerous biodegradable materials - each with different characteristics. Comparisons between biodegradable implants made of polylevolactic acid and metallic implants for fixations of displaced ankle fractures have yet to be conducted using a randomized trial.
What was the principal research question?
Does the use of biodegradable implants, made of polylevolactic acid, provide similar clinical and functional outcomes compared to the use of metallic implants for the fixation of unstable ankle fractures, assessed over a 12 month period?
Study Characteristics
-
Population:
109 patients with ankle fractures requiring surgical intervention (102 available for final follow-up). Fractures included were bimalleolar and trimalleolar fractures, lateral malleolar fractures with displacement greater than 2 mm, or an isolated medial malleolar fractures with displacement of grater than 2 mm)
Intervention:
Group 1: Patients underwent fixation using a metallic one-third tubular plate and screws (Solco Biomedical, Pyeongtaek, Gyeonggi, South Korea) (n=56)
Comparison:
Group 2: Patients underwent fixation using a biodegradable FredomPlate and screws (Inion Oy, Tampere, Finland) (n=53)
Outcomes:
Outcomes included operative time, clinical and radiographic results using the Klossner classification system, the American Orthopaedic Foot and Ankle Society ankle-hindfoot scale (AOFAS), the Short Musculoskeletal Function Assessment scoring system dysfunction index and bother index (SMFA).
Methods:
RCT
Time:
Assessments were made at three, six and twelve months.
What were the important findings?
- The mean operative time in group 1 (Metal) was 30.2 +/- 4.5 minutes compared to the mean operative time of 56.6 +/- 10.7 minutes (p<0.001) in group 2 (Bio)
- There were no differences in the reduction of medial malleolus, lateral malleolus, posterior malleolus, and syndesmosis. 6 of 12 patients in group 2 (Bio) with medial malleolar fractures had a fracture gap postoperatively or during follow-up.
- Mean time to bone union was significantly shorter in group 1 (Metal) compared to group 2 (Bio) (p=0.002): 15.8 weeks and 17.6 weeks, respectively.
- Mean AOFAS scores were greater in group 1 (Metal): 87.5+/-3.8 compared to group 2 (Bio): 84.3+/-6.6 (p=0.004)
- There were no differences SMFA dysfunction and bother indexes between the two groups (p=0.06 and 0.052, respectively); although, there was a trend present towards better scores in group 1 (Metal).
- A subgroup of patients with lateral malleolar fractures did not demonstrate differences in clinical outcomes between groups.
- There were two non-unions in group 2 (Bio) and none in group 1 (Metal) (p=0.228)
- 18 of 53 patients in group 1(Metal) had hardware removal surgery.
What should I remember most?
Fixation of unstable ankle fractures with metal implants required significantly less operative time, resulted in shorter time to radiographic union, and superior AOFAS scores;however, it is unclear if this difference in AOFAS scores was clinically relevant. The use of a metallic implant also resulted in fewer non-unions, but this difference was not significant.
How will this affect the care of my patients?
Metal implants provide superior outcomes for unstable ankle fractures compared to biodegradable implants made of polylevolactic acid. The use of a metal implant reduces operative time, time to union, and improves some functional measures; however, further clinical trials are necessary to support the findings of this study. Additionally, comparisons between metal implants and other biodegradable materials need to be conducted.
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Orthopaedic Surgeon - Canada
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