This study was designed in 2 phases. First, the original Goodman scale was translated into Spanish and cross-culturally adapted. Following the implementation of the Spanish version, the psychometric quality of the data was tested. This study was approved by the ethics review board.
The Goodman satisfaction scale consists of 2 items: the first assesses satisfaction through 4 questions, each rated on a 5-point Likert scale. The satisfaction summary score corresponds to the non-weighted average of the 4 questions, which correspond to 100, 75, 50, 25, and 0 according to the nominal response (for example, “very satisfied” corresponds to score 100 and “very dissatisfied” to 0). The second item aimed to evaluate the quality of life using a single question. This scale is valid and reliable, with high internal consistency and feasibility, and can be used postoperatively to assess the impact of THA .
The translation and cross-cultural adaptations were performed according to the recommended methodology through the following step s: first, a forward translation to Spanish was performed by 2 translators whose mother tongue was Spanish and fluent in English. A back-translation to English was carried out by 2 translators whose mother tongue was English and fluent in Spanish. A consensus meeting including 3 experts in THA, translators, and medical students compared the original English version and the back-translated version for consistency. In the same session, the clinical-linguistic issues in the Spanish-translated version were addressed. Then, the final version was tested for the level of understanding on 30 randomly selected patients who underwent THA.
We designed a cross-sectional study for data collection, and 2 institutions were enrolled: a university and a public hospital. Both centers had access to the same type and brands of prostheses to perform surgery, and surgeons had similar levels of training; 2 of the surgeons work in both centers, and the orthopaedic departments of both centers conducted joint academic activities regularly and shared a training program for fellow hip surgeons.
Patients were included if they were above 18 years of age and underwent hip replacement due to primary osteoarthritis secondary to dysplasia between 1 January 2018 and 31 December 2019. In all cases, the posterior hip approach and a primary non-constrained prosthesis were used (Corail® uncemented hip stem, Pinnacle® uncemented cup: DePuy Synthes, Warsaw, IN). All hip fractures, hip revisions, infections, and bilateral cases were excluded, as were patients with language or mental impairment.
A total of 520 patients were eligible for assessment. The medical records were screened to collect sociodemographic and clinical data, including sex, age, date of surgery, surgery protocol, phone, and e-mail.
A total of 300 patients met the selection criteria, and attempts to contact them were initiated in June 2020; therefore, all patients had at least 1 year of follow-up after THA. Of them, 210 patients were successfully contacted by phone or mail, provided digital written or verbal informed consent to be enrolled in the study, and responded to the Goodman scale and the Oxford hip scale (OHS). The OHS is a globally accepted scale which was validated in Spanish , consisting of 12 questions to evaluate patients’ functionality, and ranges from 12 to 60. The lower the score, the better the outcome. The OHS was used to assess the validity of the adapted Goodman scale . The scale was sent again 14 days after the first response was received. A total of 153 patients returned the second round of answers for analysis (Fig. 1).
Cronbach's alpha was estimated for reliability (internal consistency) analysis. A coefficient greater than 0.75, was considered acceptable . The alpha coefficient was assumed to be normally distributed, and t test was used to compare the Cronbach's alpha between this study and that performed by Goodman et al. . In addition, factor analysis was performed, and the factors were maintained if the eigenvalue was above 1.
The test-retest was assessed by comparing the first response with the answers obtained 14 days later. The intraclass correlation coefficient (ICC), Lin's concordance correlation coefficient (CCC), and the Bradley-Blackwood F test were used. An ICC and CCC over 0.75, were considered acceptable; meanwhile, a probability over 0.15, was deemed acceptable to validate the null hypothesis of concordance in the Bradley-Blackwood F test .
Finally, Spearman correlation (rho) test was conducted using the OHS score to validate the Spanish-adapted Goodman scale. An absolute rho above 0.6, was interpreted as good correlation .