Introduction
The ankle is one of the most common fracture sites in older (> 50 years) people, and more occur with age [
1]. Laterally displaced and rotated ankle fractures usually require surgical stabilization [
2‐
4]. A 1-mm displaced talus is associated with more than 40% of tibiotalar contact area decreases and changes [
5]. The lateral malleolus is important for ankle mortise stability, especially in AO (Arbeitsgemeinschaft für Osteosynthesefragen )/OTA (Orthopaedic Trauma Association )-44B transsyndesmotic fibula fractures accompanied by mortise changes and talus tilt [
6‐
8].
The Muller technique, using an interfragmentary screw and a non-locking one-third tubular neutralization plate, is recommended for treating AO/OTA 44-B fractures [
9]. However, this technique may also lead to fixation failure, further fracture displacement, and poor clinical outcomes in older patients [
10]. Open reduction and internal fixation of ankle fractures in older patients may lead to increases in complications [
11‐
13]. Locking plates in distal fibula fractures show superior biomechanical fixation stability in osteoporotic bone [
14] and in comminuted artificial bone models [
15]. However, clinical outcomes using locking plates for treatment of older patients are still unclear.
Several radiological parameters, including fibular length and talar tilt angle (TTA), have been reported to be related to clinical outcomes in patients with ankle fractures [
16‐
18]. However, perfect radiographs do not guarantee excellent clinical outcomes, where older patients frequently have poorer results [
16]. The association of clinical features with pain and functional outcomes in older patients with AO/OTA 44B fractures, the most common type of ankle fracture [
19], is still unclear. Therefore, we compared radiological and functional outcomes in older patients with AO/OTA 44B fractures after lateral fixation with either periarticular locking plates (PLPs) or one-third non-locking tubular plates (TPs). We hypothesized that in older patients: (1) PLPs will provide better radiological and functional outcomes than would be the case for TPs and (2) the severity of osteoarthritic (OA) ankle, TTA ≥ 2°, and distal screw loosening will be associated with pain and functional outcomes.
Discussion
This is the first study to compare the surgical results of AO/OTA 44B fractures treated with lateral PLPs and TPs in patients > 50 years old. There were no significant between-group differences in preoperative demographic data, complication rates, immediately postoperative distal fibula lengths, ankle OA grades, TTAs ≥2°, or reduction accuracy. All fractures achieved union. The TP group had significantly shorter operation times. The PLP group had significantly less fibula shortening, lower rates of distal screw loosening, fibula shortening > 2 mm, ankle OA grade progression, TTAs ≥ 2°, and better FAOSs and VAS scores than was the case for the TP group after 1 year of follow-up. In analyzing the association of clinical features with FAOSs and VAS scores, FAOSs were negatively associated with renal disease, OA grade, distal screw loosening, and TTAs ≥ 2°. The VAS score was significantly positively associated with OA grade, distal screw loosening, and TTAs ≥2°.
Surgical treatment for ankle fracture usually leads to high rates of complication in older people with osteoporosis, inadequate hardware purchase, and poor surrounding soft tissue [
2,
10,
13]. Therefore, PLPs have recently become popular for treating osteoporotic lateral malleolar fractures [
7,
22]. In OTA 44-B ankle fractures, PLPs are biomechanically superior to conventional non-locking tubular plates in osteoporotic cadaver modes [
14,
28], where fixation strength of a PLP is independent of bone mineral density [
14,
28]. However, for OTA 44-B and 44-C lateral malleolar fractures, the biomechanical superiority of locked lateral plates cannot be demonstrated when compared with conventional lateral plates in a meta-analysis of biomechanical studies using osteoporotic cadaver models [
29]. Up to date, there are several studies evaluating the clinical outcomes in lateral malleolar fractures treated with and without locking plates [
3,
4,
13,
22,
23,
26,
30‐
32] (Supplemental Table
3). However, the reported results vary under the different inclusion criteria for fracture type and implant type. For pure OTA 44-B lateral malleolar fractures, there are two studies in a general patient population [
23,
30]. Tsukada et al. [
23] reported no significant differences in the 36-Item Short Form Survey (SF-36) score, fibula union rate, and wound complication rate between a locking reconstruction plate group and a non-locking periarticular plate group. Moss et al. [
30] reported no difference in the rate of failure and loss of reduction between a PLP group and a non-locking TP group. However, the PLP group had a higher deep infection rate and implant removal rate. For a senior patient population, there are two studies enrolling OTA 44-C type fractures with or without 44-A type fractures in addition to 44-B fractures. Herrera-Perez et al. [
22] showed similar average time to union and AOFAS scores in osteoporotic patients aged over 64 using either locking or non-locking TPs. However, time to weight bearing was significantly lower in the locking TP group. Lynde et al. [
13] reported that the locking plate group had higher wound dehiscence rates in patients over 60. In our study, we included older patients over 50 years of age and found that the PLP group had significantly less fibula shortening, lower rates of distal screw loosening, fibula shortening > 2 mm, ankle OA grade progression, implant removal, TTAs ≥ 2°, and better FAOSs and VAS scores than did the TP group after 1 year of follow-up. Further studies are necessary to compare the clinical outcomes using locking plates and non-locking plates for AO/OTA 44-B type fracture fixation in older patients.
Fibula length is important for ankle-joint stability, where a loss of lateral malleolar length or alignment may lead to significant biomechanical instability associated with a poor clinical outcome [
18,
33]. In our study, the non-locking plate was associated with more fibular shortening, more OA grade progression, and worse FAOS total scores and VAS scores. Other researchers have reported that a shortened fibula is associated with post-traumatic osteoarthritis after fractures, especially in those > 2 mm shorter than the contralateral ankle [
18], where there were significantly higher pain scores in post-traumatic OA patients with TTAs ≥ 2° than in those with TTAs < 2° [
17]. Our PLP group had less fibular shortening > 2 mm and fewer TTAs ≥ 2° after a 1-year follow-up. This group also had better FAOSs and VAS scores.
Although significant differences were found, treating with a PLP is more expensive. Under our government health insurance system, the cost of a PLP (1800–2000 USDs) is much higher than that of a TP (50–100 USDs). Further studies are necessary to evaluate the cost-effectiveness and clinical indications for PLPs.
Additionally, we found that renal disease, ankle OA grade, distal screw loosening, and TTAs ≥ 2° were negatively associated with FAOSs. Ankle OA grade, distal screw loosening, and TTAs ≥ 2° were positively associated with VAS scores, however. Fibular shortening, TTA, and syndesmotic widening suggest poor outcome, but they are not necessarily significant in all unstable ankle fractures with TTAs ≥ 2° [
16]. This may partly explain why our PLP group patients with preserved fibula length had better functional outcomes and pain scale scores and less OA grade progression. We and other researchers [
17] found a TTA ≥ 2° to be positively associated with more severe pain scores. In addition, a TTA > 2° is associated with more severe osteochondral lesions [
34]. However, fibular length, which has been associated with clinical outcomes [
18], was not significantly associated with VAS scores or FAOSs in our study. One possible reason is that the fibular length is correlated with TTA and OA grade. In our multiple regression model, the effect of fibular length was explained by the other two parameters.
Our multiple regression analyses showed renal disease to also be associated with higher pain scores. A possible explanation for this might be that patients with chronic kidney disease tend to have higher prevalence (≥ 70%) of acute and chronic pain [
35]. However, the factors that affect pain manifestation in chronic disease are unclear thus far.
Acknowledgements
We are grateful to Skeleton Materials and Bio-compatibility Core Lab, Research Center of Clinical Medicine, National Cheng Kung University Hospital, for assistance with this study. We thank the Taiwan Ministry of Science and Technology, National Cheng Kung University Hospital, and National Cheng Kung University for funding this work (grants: MOST106-2622-E-006-029-CC2, NCKUH-10702024; NCKUSCM10808; MOST 107-2314-B-006-065-MY3; NCKUH-10804001). We are grateful to our colleague, Dr. Chia-Lung Li, Dr. Po-Yen Ko, Dr. Ta-Wei Tai, Dr. Cheng-Li Lin, Dr. Chih-Wei Chang, Dr. Che-Chia Hsu, and Dr. Ming-Tung Huang from our orthopedic department for collecting clinical data, to Prof. Chung-Yi Li and Ms. Shang-Chi Lee for providing the statistical consulting services from the Biostatistics Consulting Center, National Cheng Kung University Hospital, as well as Ms. Yu-Ying Chen for her excellent assistance.
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