Abstract
The aim of orthognathic surgery is to produce a more aesthetic facial skeletal appearance, and improve jaw function. This prospective study, aimed to evaluate the impact of orthognathic surgery on quality of life for patients with dentofacial deformity, and whether it was clinically meaningful. 62 consecutive patients were recruited (27 male, 35 female) aged 18–38 years. Baseline data were collected using a validated health status measure (Orthognathic Quality of Life Questionnaire (OQLQ)) and a visual analogue scale (VAS). Postoperative questionnaires (OQLQ, VAS) and a Global Transition Scale (GTS) were completed at 6 months after completion of treatment and compared with pre-treatment scores. Following surgery, there was a significant ( p < 0.05, paired t test) improvement in OQLQ scores for each domain. The proportion of patients reporting a moderate or large improvement was: facial appearance (93%), chewing function (64%), comfort (60%) and speech (32%). Clinical relevance of change scores was reported in terms of effect sizes, and the largest effect was on facial aesthetics. The clinical impact was moderate on social aspects of deformity and oral function and a small effect on awareness of facial deformity. This research reaffirms that orthognathic surgery has positive effects on quality of life.
The evaluation of quality of life using health status measures is increasing in the assessment of healthcare outcomes . It has been recognized that objective measures alone do not fully capture the impact of a condition on daily living, and subjective assessment of the impact of disease or condition is also required.
Orthognathic surgery is carried out to correct dentofacial deformity. This involves pre-surgical orthodontics with fixed appliances for alignment and levelling of the dental arches. Surgery is then carried out to reposition the jaws, resulting in a more harmonious facial skeleton. Many studies show that patients benefit psychologically and have improved facial and dental aesthetics and improved function after treatment .
The assessment of quality of life impact after orthognathic surgery is difficult to measure objectively as the patient’s life is neither extended nor is a disease cured in the conventional understanding of healthcare . Health related quality of life (HRQoL) is multifactorial, and any model constructed to quantify this should include, physical, social and psychological domains, as suggested by C amilleri -B rennan & S teele . Generic health, generic oral health and condition-specific measures have been used to assess the impact of orthognathic surgery. The generic health questionnaire may be used to compare the outcomes with those of other conditions, but the lack of condition specificity can mean that generic instruments are not able to address issues relevant to people with facial deformity. For instance, L ee et al. found the 36 item Short Form Health Survey (SF-36) to be insensitive and unable to detect differences in quality of life between those with and without dentofacial deformities.
The development of a condition-specific measure was undertaken to generate a specific measure that could focus on a particular condition and population and be potentially more responsive to small, but clinically important, changes in health . C unningham et al. noted that patients with severe dentofacial deformity had not been studied in this way and previous reports relied on generic questionnaires that were less likely to detect specific changes in a specific population. The Orthognathic Quality of Life Questionnaire (OQLQ) was developed using several sources for item derivation, including a literature review, and unstructured interviews with clinicians and patients .
The items were divided into four domains: social aspects of deformity, facial aesthetics, oral function and awareness of facial deformity. C unningham et al. have tested the validity of OQLQ by using the SF-36 questionnaire and a visual analogue scale (VAS) for comparison. A number of recent reports have used the OQLQ to evaluate the impact of orthognathic surgery on quality of life. In a case–control study of 154 Chinese patients, L ee et al. showed that facial deformity affects many aspects of patients’ lives and the OQLQ was able to detect this. In a follow up publication, 36 of these patients received orthognathic surgery and reported significant improvement in quality of life . In a study of German patients using the OQLQ, B ock et al. confirmed the findings of L ee et al. that facial deformity had significant negative impacts on quality of life. Each of these reports suggests that the OQLQ has good measurement properties and is suitable as an outcome measure for facial deformity and its management using orthognathic surgery.
Measurement of change is central to evaluating the impact of treatment in healthcare, and is usually reported in terms of statistical significance. In some cases, pre-/post-treatment change scores may be statistically significant but not necessarily clinically significant or meaningful to the patients who experience that change. Interpretability of a health status measure has been defined as ‘the degree to which one can assign qualitative meaning – that is, clinical or commonly understood connotations – to quantitative scores . A commonly used approach to determine the clinical meaning of scores is to calculate the effect sizes. An effect size is a distribution based measure of change, and C ohen has suggested benchmarks to indicate the size of change that has occurred following a clinical intervention. He has suggested that an effect size of 0.2 is equivalent to a small change, 0.3–0.7 as a moderate and >0.8 as a large pre-/post-treatment change.
None of the previous studies have used self reported global transition scores to give an indication of the clinical relevance of orthognathic surgery, nor have they attempted to quantify the clinical relevance of change. The aim of this study was to evaluate the impact of orthognathic surgery on the quality of life of patients with facial deformity, and, to determine if the OQLQ is able to detect clinically important change in patients undergoing surgery to correct dentofacial deformity.
Material and methods
The study protocol was reviewed and approved by the Clinical Research Ethics committee of the Cork Teaching Hospitals. Patients attending for consultation in orthognathic surgery between June 2006 and July 2008 in Cork and Limerick maxillofacial surgery units were asked to participate. In this prospective study, 62 consecutive patients (27 male, 35 female) with congenital deformities in the maxilla, mandible or both, agreed to participate in the study. All of the patients had congenital disharmony, and none of them had symptoms associated with syndromes. The age range was 18–38 years (mean 21.6 years). Patients were recruited having commenced orthodontic treatment, and whilst awaiting surgical treatment. Data were collected at two stages: during the orthodontic phase of treatment, prior to surgical intervention; and 6 months after surgical treatment. The measures used to assess quality of life were the OQLQ, a VAS and, a Global Transition Scale (GTS). Patients completed the OQLQ and VAS prior to treatment, and the post-treatment questionnaire 6 months post-surgery. The GTS was included in the post-treatment questionnaire, and used to determine the concurrent validity of the pre- and post-treatment change score for the OQLQ.
The OQLQ contains 22 statements relating to 4 domains: appearance; function; social aspects of deformity; and awareness of deformity. Respondents are asked to indicate their level of agreement with statements such as ‘I don’t like eating in public places’. These responses are rated on a Likert scale scoring system, with response possibilities ranging from 1 (it bothers you a little) to 4 (it bothers you significantly). Summary scores for each domain were calculated by summing response codes within domains pre- and postoperatively and then compared to detect change. Higher scores indicate higher levels of concern in relation to each domain, lower scores indicate less concern and better quality of life.
A VAS was also incorporated into the pre- and post-treatment questionnaires. Patients were asked to indicate their level of satisfaction with treatment on a 100 mm scale ranging from 0 to 100, 0 being poor satisfaction level and 100 being the best possible outcome. The preoperative VAS was rated on satisfaction with treatment up to the point of surgery. The postoperative VAS was rated on satisfaction with post-surgery period and outcomes of treatment.
In addition, a GTS was incorporated in the post-treatment questionnaire to provide an anchor based measure of change against which the condition-specific scale can be measured. In this questionnaire, patients rated the impact of surgery on appearance, chewing, oral comfort and speech. As recommended by J uniper et al. , these transition variables were scored on 15-point scale ( Table 1 ).
| Code | Response |
|---|---|
| 1 | A very great deal worse |
| 2 | A great deal worse |
| 3 | A good deal worse |
| 4 | Moderately worse |
| 5 | Somewhat worse |
| 6 | A little worse |
| 7 | Almost the same, hardly any worse at all |
| 8 | No change |
| 9 | Almost the same, hardly any better at all |
| 10 | A little better |
| 11 | Somewhat better |
| 12 | Moderately better |
| 13 | A good deal better |
| 14 | A great deal better |
| 15 | A very great deal better |
In addition to descriptive statistics, pre-treatment domain scores were compared with post-treatment scores using paired t tests (SAS ® Version 9.1) at a 5% level of significance. Effect sizes for each domain were calculated by subtracting the mean post-treatment score from the mean pre-treatment score and dividing by the standard deviation of the pre-treatment score. Using the Global Transition Scale, the proportion of patients who reported ‘no change’, ‘minor improvement’, ‘moderate improvement’, ‘large improvement’ and ‘deterioration’ were calculated. Also, following J uniper et al. , the magnitude of change in the four domains assessed was defined as follows: 7, 8 or 9 was considered as no change; 10 or 11 was considered as a small change that defines the minimally important difference; 12 or 13 was considered moderately changed; 14 or 15 was considered a large change; and 1, 2, 3, 4, 5 or 6 was considered a deterioration.
Results
There were 62 participants in the study of whom 52 completed postoperative questionnaires. 10 subjects (5 male, 5 female) were lost to follow-up, but there were no characteristic differences between these patients and those who completed the follow-up questionnaires. For the remaining 52 patients, the most common skeletal classification was class 3 ( n = 32). This was corrected by mandibular setback or bimaxillary surgery. 16 patients had surgery to correct class 2 malocclusion, 4 patients had surgery to correct class 1 malocclusion. All of the patients in the study, except one (female, age 36 years), had pre-surgical orthodontic treatment to optimize treatment outcome. Mean length of time for pre-surgical orthodontics was 24 months.
The mean pre-/post-treatment difference was found to be statistically significant for all domains of the OQLQ at the 5% level of significance ( Table 2 ). In terms of clinical significance, the effects sizes were: appearance 0.9; function 0.4; social aspects of deformity 0.4, and awareness of deformity 0.2. This indicates that the impact on appearance was large, with moderate impacts on social aspects of deformity and function. The impact on awareness of deformity was clinically important, but the effect was small. The preoperative VAS scores are high, which may be attributed to the fact that patients are satisfied with orthodontic treatment and surgical consultations. The mean difference in VAS is statistically significant as shown in Table 2 .
| Domain, N = 52 | Mean pre (S.D.) | Mean post (S.D.) | Mean difference | P -value |
|---|---|---|---|---|
| Aesthetics | 12.21 (5.87) | 7.00 (5.64) | 5.21 (6.19) | 0.0001 * |
| Awareness | 6.90 (4.80) | 5.73 (4.19) | 1.17 (3.93) | 0.0363 * |
| Social | 10.42 (8.33) | 7.19 (8.32) | 3.23 (8.18) | 0.0063 * |
| Function | 7.46 (5.99) | 5.69 (5.77) | 1.77 (6.00) | 0.0384 * |
| VAS ( N = 41) | 79.22 (18.42) | 87.56 (15.50) | −8.34 (20.94) | 0.0 * |
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