Abstract
Background
Ankle fractures are common injuries treated by trauma surgeons. Failure of fixation necessitating subsequent revisions remains a significant concern, carrying increased morbidity and healthcare cost. Mechanical failures are poorly categorised in the literature. This study aims to classify patterns of mechanical failure following primary ankle internal fixation.
Methods
A retrospective observational study was conducted at a single major trauma centre, reviewing electronic patient records (EPR) and radiographs of 897 patients who underwent internal fixation for unstable ankle fractures over five years (June 2014 to August 2018). Data on patient demographics, injury characteristics, surgical techniques, and complications were collected. Mechanical failures were categorised into three subtypes based on the direction of talar displacement and syndesmotic involvement: Type 1 (lateral talar instability with intact syndesmosis), Type 2 (lateral talar instability with disrupted syndesmosis), and Type 3 (posterior talar instability). The inter-rater reliability of this classification system was evaluated using intraclass correlation coefficient (ICC) analysis.
Results
The revision rate after primary ankle internal fixation was 6.6 % (59/897), with mechanical failures accounting for 69 % (41/59) and infective failures for 31 % (18/59). Patients in whom the primary ankle fixation failed were significantly older than the group in whom the primary ankle fixation did not fail (mean age 60 vs. 52 years, p = 0.0018). The mean ICC values for the classification system was 0.84, indicating good inter-rater reliability.
Conclusions
The revision rate for unstable ankle fractures treated with primary internal fixation was 6.6 %, with the majority of revisions attributed to mechanical failures. Lateral talar instability, particularly when associated with syndesmotic disruption, was the most common cause of mechanical failure. Our grading system demonstrated high inter-rater reliability and provides a tool for categorising these failures.
1
Introduction
Ankle fractures are among the most common injuries treated by trauma surgeons, with an estimated 369 ankle fractures sustained daily in the US with an incidence of 4.22/10,000 person-years.
The revision rate after primary ankle internal fixations reported in the literature is variable and between 1.6 % and 14 %. , But there is a paucity of studies investigating the causes and related patterns of failure after primary ankle fixation. Loss of fixation may occur due to either infective or non-infective (mechanical) causes. Infective failures typically involve deep infections that compromise the stability of the fixation, while mechanical failures can result from issues such as implant malposition, inadequate initial fixation, or patient-specific factors such as bone quality and load-bearing characteristics. There is a gap in the literature regarding systematic grading criteria to categorise mechanical failures due to the wide variety of presentations of failure and relatively small overall numbers. Furthermore, failure of primary ankle internal fixation is associated with significant morbidity and cost of treatment including permanent disability for the patient, requirement for multiple revision surgeries, amputation and not uncommonly, mortality. ,
The primary objective of this study was to categorise patterns and causes of mechanical failure following primary ankle internal fixation. Such categorisation may then support timely decision-making for the orthopaedic surgeon involved with the assessment and management of these patients.
2
Material and methods
Permission for the study was obtained from the local Caldicott Guardian and the Musculoskeletal Audit Department. The electronic patient records (EPR) and radiographs of patients with an acute isolated unstable ankle fracture who underwent fixation at one major trauma centre were retrospectively reviewed (n = 897). Data were collected over a five-year period between June 2014 to August 2018. Patient demographics including age, sex, date of injury, laterality, injury details (open/closed), revision details (including intention to revise), and complications were recorded.
Following database construction, specific exclusions were applied as detailed in the flowchart ( Fig. 1 ). We identified all patients requiring re-operation including those patients in whom failure of the primary ankle internal fixation was confirmed radiologically but who did not have re-operation (intention to revise, n = 1 due to patient choice, n = 1 due to frailty, n = 1 due to mortality). The following cases were not considered as reoperations due to failure of ankle internal fixation: symptomatic removal of metalwork (without construct failure, n = 28), screw breakage without loss of fixation (n = 20), and screw loosening with no talar shift (n = 5). We categorised all remaining cases requiring reoperation as either a mechanical failure or an infective failure. Revisions for deep infections without mechanical failures were excluded from further analysis (n = 18). The sub-group of patients with mechanical failure represented the study sample (n = 41) for this work. Follow-up duration was defined as time from initial date of surgery to final review in orthopaedic clinic.
Flowchart of study population.
For the sub-group of patients with mechanical failure, fracture patterns were further classified using AO/OTA, Lauge-Hansen, and Weber classifications (Table 1). The senior author studied sequential radiographs of all patients in the study sample to assess identifiable patterns of failure visible from initial post-operative radiographs alone (without the use of routine CT) as this was not normal practice during the study period. The cause of failure (implant related or technical error) was defined as below:
-
(a)
Construct failure (implant-related) was considered to have occurred when the reduction and fixation of the ankle mortise was satisfactory on intraoperative or immediate postoperative X-rays, but the talus displaced thereafter.
-
(b)
Technical failure (surgeon-related) was considered to have occurred when the reduction and/or fixation of the ankle mortise was suboptimal with a recognisable technical error on either intraoperative or immediate postoperative X-rays, resulting in subsequent displacement of the talus.
The imaging was also independently assessed by four other experienced orthopaedic surgeons (one consultant, three senior specialist residents) to test inter-observer reliability.
3
Statistical analysis
Statistical analysis was conducted to evaluate the significance of the differences observed in revision rates and the factors contributing to failure in ankle fracture fixation. Statistical analysis was performed using SPSS version 29 (SPSS Inc, an IBM company, Chicago, IL). Fisher’s exact test was used to analyse the categorical data. Unpaired t-tests were used to compare continuous variables between the groups. The p-values obtained from these statistical tests were used to determine the significance of the results. A p-value < 0.05 was considered statistically significant.
To evaluate the reliability of the classification system, an intraclass correlation coefficient (ICC) analysis was performed. The ICC was calculated using a two-way mixed-effects model. The analysis was conducted to determine the consistency and agreement among the raters. Specifically, we focused on the average measures results for their higher reliability and robustness compared to single measures. Each ICC value was reported with a 95 % confidence interval. The ICC values were interpreted according to well established guidelines: values below 0.50 indicate poor reliability, values between 0.50–0.75 indicate moderate reliability, values between 0.75–0.90 indicate good reliability, and values greater than 0.90 indicate excellent reliability
4
Results
4.1
Patient demographics
The mean age of the patients included in this series of mechanical failures was 60 years (range 21–93) and 76 % (31/41) were female. Failure of fixation after primary ankle internal fixation occurred in a group of patients significantly older compared to the group of patients in whom primary ankle internal fixations was successful (mean age 60 yrs [range 13–93] vs 52 yrs [range 13–98], p = 0.0018). There were no observed difference in sex and laterality between the two groups ( Table 1a ).
Table 1a
Demographics of patients after successful primary ankle fixation compared with those patients in whom the primary ankle fixation failed.
| Primary ankle fixation | Revised | P value | |
|---|---|---|---|
| Total (n) | 897 | 59 | n/a |
| Age (years, range) | 52.0 (13−98) | 60.4 (13−93) | 0.0018 |
| Sex (Female) | 584 (65.1 %) | 44 (74.6 %) | 0.5327 |
| Laterality (Right) | 509 (56.7 %) | 39 (66.1 %) | 0.5151 |
The demographics and fracture patterns for patients in whom the primary ankle fixation failed due to mechanical reasons are presented in Table 1b . The majority of patients (53.7 %, 22/41) were AO/OTA 44B3 type fractures. 70.7 % (29/41) of failures has a posterior malleolus fracture. 70.7 % (29/41) of fractures were supination external rotation (SER) type injuries as classified by the Lauge-Hansen. Among the 29 SER-type failures, 20 involved medial malleolus fractures and 9 had deep deltoid injuries. Of the remaining patients, 19.5 % (8/41) patients were pronation-external rotation (PER) injuries and 9.8 % (4/41) were pronation-abduction (PAB) type injuries. Of note, no patients with an initial supination-adduction type injury required revision surgery for failure in our study sample. Classification as per the Weber classification revealed 75.6 % (31/41) of failed ankle fractures were Type-B and 24.4 % (10/41) were Type-C fractures. Of the 10 Weber C fractures that failed, 7 (70 %) had associated posterior malleolar fractures.
Table 1b
Fracture patterns for the study sample of patients with mechanical failure after primary ankle fixation (n = 41).
| Failure subtypes | |||||
|---|---|---|---|---|---|
| Type 1 | Type 2 | Type 3 | Total | Percentage/% | |
| Total | 9 | 27 | 5 | 41 | |
| Percentage/% | 22 % | 66 % | 12 % | 100 % | |
| Fracture classifications | |||||
| AO/OTA: | |||||
|
44 A
44B1 44B2 44B3 44C1 44C2 44C3 |
0
0 4 4 0 1 0 |
0
0 5 14 2 5 1 |
0
0 0 4 0 1 0 |
0
0 9 22 2 7 1 |
0
0 22 % 54 % 5 % 17 % 2 % |
| Lauge-Hansen: | |||||
|
Pronation-Abduction (PAB)
Pronation-External Rotation (PER) Supination-External Rotation (SER) Supination-Adduction (SAD) |
0
1 8 0 |
4
6 17 0 |
0
1 4 0 |
4
8 29 0 |
10 %
20 % 70 % 0 |
| Weber: | |||||
|
Weber A
Weber B Weber C |
0
8 1 |
0
19 8 |
0
4 1 |
0
31 10 |
0
76 % 24 % |
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