Introduction
Osteochondral lesions of the talus (OLTs) are focal problems of the cartilage and its subchondral bone [
10,
25]. The first treatment in line for the specific injury is a non-operative protocol potentially consisting of different types of subtypes of non-operative treatment options [
12]. A surgical intervention can be needed in case of persistent and restrictive complaints after at least 6 months of non-operative treatment protocol.
To date, the most comprehensive study concerning non-operative treatment available is a systematic review from Zengerink et al. [
44]. Despite the clear oversight of outcomes, this study included articles published up to the year of 2006 and an update of outcomes will add value to daily practice. Furthermore, radiological outcomes were not assessed and further sub-specify the clinical efficacy of the different subtypes of non-operative treatment protocols beyond rest and casting.
Consequently, it is currently unclear how effective non-operative therapy is for osteochondral lesions of the talus (OLTs) and which sub-type of non-operative therapy is most effective. It is therefore the purpose of the this study to assess the overall clinical success rate and associated radiological progress of focal or generalized joint degenerative changes after non-operative management for OLTs and to analyze different subtypes of non-operative management if possible. Our secondary hypothesis is that non-operative management yields an overall successful clinical result in approximately half of the patients.
Discussion
The most important finding of the present study is that non-operative treatment for osteochondral lesions of the talus is clinically effective in 45% of the patients. No evidence was identified that one of the subtypes of non-operative management protocols were superior or inferior to one another from a clinical or radiological perspective.
It is to be stated that non-operative treatment is recommended as first treatment in line after the initial diagnosis of an OLT as a result of our findings [
12]. The used strategies in non-operative treatment were heterogeneous as they differed widely in the included articles. Four articles used a so called “benign neglect’’ or modification of the activities [
15,
35,
36,
40]. Seo et al. [
35] stated that good clinical results were obtained with a mean AOFAS of 93 points at a long-term follow-up. Another interesting finding from the study of Seo et al. [
35] was that the average VAS score of pain at baseline was 3.8, suggesting that patients did not have major complaints at the onset of treatment. Despite that a lower level of complaints might be an indication for the choice of non-operative treatment, other indications were not mentioned in any of the studies reporting on solely activity restrictions or a “benign neglect’’.
Weightbearing restrictive treatment modalities were also frequently reported non-operative treatment options as four studies were included in our systematic review on this particular treatment modality [
13,
17,
18,
27]. Periods of immobilization in the included studies ranged from 3 to 8 weeks. It was found that the success rates having been found in the studies on immobilization were around 50% [
17,
30]. There was no superiority observed concerning clinical outcomes with longer immobilization periods. Despite this promising result, no radiological results can demonstrate improvement of the lesion due to immobilization.
Two articles described the use of injectables by injecting hyaluronic acid or 99 m TC-methylene diphosphonate. Liu et al. [
23] noticed substantial clinical progression in terms of the AOFAS and VAS scores after injection of TC-methylene diphosphonate with herbal fumigation. However, this intervention is totally new and the literature on this topic is scarce which made it impossible to draw conclusions on the working mechanism and potential effect of this treatment strategy. Hyaluronic acid injections showed its potential in improving the clinical symptoms. This may be due to the chondroprotective and anti-inflammatory effect which limiting degenerative changes coming along with the osteochondral defect [
38]. Another injectable that was studied was Platelet Rich Plasma [
1,
28]. These injections showed considerable improvements when considering the pain scores as measured with the VAS scale. However, it should be mentioned that these studies were conducted in small populations including relatively low number of patients. Moreover, the reported results were assessed at short-term follow-up. As such, one could state that specific conclusions considering the efficacy of injection therapy cannot be made due to the low level of evidence originating from these studies.
One can state that the methodological quality of injection therapies for OLTs was considered low, and the potential and indications of injection therapies as part of non-operative treatment for OLTs need to be further investigated in future double-blind placebo-controlled prospectively randomized studies.
In addition to different types of non-operative management, duration of the non-operative management is an important factor to analyze. Activity restrictions or cast immobilization were applied for a period ranging from 3 to 8 weeks. After a period of activity restriction, casting, physiotherapy or a combination of all, patients and clinicians must decide whether non-operative management meets their expectations of the treatment or if surgical treatment is indicated. The current literature suggests considering surgical management after trying non-operative management for at least 6 months. This is corresponding with literature included in this study [
12]. Additionally, the literature concerning osteochondral lesions of the knee suggests that lesions can heal within a time of six months which seems to confirm that 6 months is a proper duration [
2].
The conversion to surgery rate emphasizes that a certain part of the population has no indication for direct surgical treatment. However, based on the results on this review, it is difficult to define clear indications for non-operative management. Described indications varied widely in the included studies in terms of lesion characteristics and level of complains. It was therefore not possible to analyze if specific indications were superior to others. One of the indications that need to be discussed is the justification of a surgical treatment. In several studies it is stated that patients avoided surgery or that they stated that their symptoms simply did not justify their complaints [
17]. This reveals that the decision-making process for non-operative management is highly important in a patient group who can accept a lower functional status with minor complains [
12]. Based on the statement of Dobrowski et al. [
12] and the results of present review non-operative management is advocated for at least 6 months which can be extended based on a shared-decision-making process and regular clinical and radiological follow-ups.
Concerning the radiological outcomes which were analyzed in the present study, one can note that radiological healing was assessed in the studies of Perumal et al. [
29] and Wester et al. [
43] having shown a healing rate of 18% and 69%, respectively. This healing rate can be considered relatively high compared to other studies [
34,
36]. These healing rates can be explained by the fact that Perumal et al. [
29] and Wester et al. [
43] included patients from a pediatric population as it is known that patients with open growth plates have a higher healing potential [
6,
14]. However, it remains unclear to what extent precisely a casting and weight bearing restriction protocol may support this healing.
It should, however, also be noted that a selective group of 10% developed arthritic changes in a relatively short period. This must aware clinicians in the risk of possible deterioration when starting conservative management. It is therefore highly recommended to have an intensive follow-up including CT-scans and physical examinations after the start of conservative management to change the treatment path and avoid irreversible damage. To identify patients benefitting from non-operative management, prospective studies on different non-operative treatment modalities are needed. These studies need to include radiological follow-up too as it enables caretakers and patients to see which impact non-operative management has on the radiological characteristics of the lesion.
Despite the discrepancy between the healing rate and the pooled success rate of non-operative treatment, it must be emphasized that the majority of the lesions do not progress over time from a radiological perspective nor showed development of osteoarthritis. The latter is an important fact in the provision of information to patients to manage their expectations.
This review has a number of strengths. First, this review was pre-registered in the PROSPERO database [
9]. It must also be stated that the thorough reference selection and quality assessment of the included studies can be considered strengths of the study. Moreover, to the best of our knowledge, this is the first review summarizing different types of non-operative management including its clinical and radiological outcomes. As such, the clinical relevance of the present study entails that the summary of a comprehensive overview of the different types of non-operative treatment modalities including their clinical- and radiological outcomes will aid and improve the decision-making process.
Besides its strengths, there were a number of limitations concerning the present review. The included studies were mostly retrospective in nature and published before 1990 causing a high heterogeneity among the studies in terms of success definition, included population, follow-up moments and indications. Due to this heterogeneity, results need to be interpreted with caution as there is a high chance of indication bias. One of the heterogeneous factors was the difference in the use of clinical outcomes. Clinical success was defined as good or excellent outcomes, or an AOFAS score > 80. However, “good’’ or “excellent’’ outcomes leaves space for interpretation. The following criteria were used in the included studies to classify the outcome of the treatment: conversion to surgery, Higuera classification [
16], clinical symptoms such as pain and functional results such as activity restrictions. It can be logically argued that such a wide range of definitions may lead to bias of the results. Secondly, different patient selections took place for the indication of conservative management introducing a potential selection bias. Additionally, it was found that 2% of the lesions were of non-primary (i.e., secondary or tertiary) nature, and, as, such, it is not expected that this may influence the outcomes of the present study.
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