Outcome of total hip arthroplasty,but not of total knee arthroplasty,is related to the preoperative radiographic severity of osteoarthritis: A prospective cohort study of 573 patients

ResultsAdjusted for sex, age, preoperative scores, BMI, and Charnley score, radiographic severity of OA in THA was associated with improvement in HOOS “Activities of daily living”, “Pain”, and “Symptoms”, and SF36 physical component summary (“PCS”) scale. In TKA, we found no such associations.InterpretationThe decrease in pain and improvement in function in THA patients, but not in TKA patients, was positively associated with the preoperative radiographic severity of OA.DiscussionThis prospective study in patients undergoing THA and TKA showed that changes in scores over time were greater in patients with more severe radiographic OA. The difference was statistically significant for a number of clinical outcomes in THA patients, but not in TKA patients.Overall, our results are in line with the literature, with the majority of studies concluding that more severe radiographic OA preoperatively is associated with better outcomes in THA or TKA (Dowsey et al. 2012, Valdes et al. 2012, Keurentjes et al. 2013). Concerning THA specifically, similar to the present study, Valdes et al. (2012) reported greater improvements in pain 3 years after surgery in patients with severe radiographic OA preoperatively. Greater improvements in the SF subscale and summary scale scores were seen in patients with higher KL scores in a study by Keurentjes et al. (2013), but the differences were not statisticaly significant.Regarding TKA, our study did not show any statistically significant differences between the outcomes in patients with different grades of radiographic severity, although—as in the study by Cushnaghan et al. (2009)—greater improvements were generally seen in patients with higher KL grades. In contrast, Valdes et al. (2012) and Keurentjes et al. (2013) found statistically significantly better outcomes in TKA patients with severe radiographic OA, and similar results were seen in some of the analyses in the study by Dowsey et al. (2012). Comparisons with the literature are, however, hampered by the large diversity in study designs and analyses.It is difficult to draw conclusions about the clinical relevance of the results of our study and of previous ones. Firstly, there are several factors associated with worse outcomes after THA/TKA, such as older age, female sex, obesity, worse general health, involvement of other joints, and a lower level of education (Dieppe et al. 2009, Gossec et al. 2011). Only from large, prospective studies using a standardized set of preoperative characteristics and outcome assessments done at fixed time points can true prediction models including all potentially relevant determinants be derived, which afterwards need to be validated in multiple settings and countries. However, we can interpret the absolute change scores as observed in the different groups according to radiographic severity. A recent systematic review by Keurentjes et al. (2012) found that overall minimally clinically important differences (MICDs) in HRQoL in THA/TKA have limited precision and are not validated using external criteria. The study which is most comparable to our study is that from Clement et al. (2014). In that study, the MCID in OKS for the difference between preoperatively and 1 year postoperatively was 15.5 (95% CI: 14.7–16.4). In our study, generally patients in both the mild and severe OA groups achieved this improvement, indicating that the clinical relevance of a statistically significant difference may be limited.A main strength of our study was the inclusion of a wide range of validated PROMs, covering all items of disease-specific outcome measures in functioning, pain, and health-related quality of life. Using all these outcome measures, both measures of pain and daily activities, we observed differences between groups according to radiographic severity. Another strength was that all radiographs were read by a single observer with extensive experience, who was blinded regarding patient data. In addition, this was a prospective study with a relatively large cohort with only 20% loss to follow-up in the THA group and only 23% loss to follow-up in the TKA group.Our study also had a number of limitations. It only included KL grading applied to the anteroposterior and posteranterior radiographs from the preoperative hip and knee.In the study by Dowsey et al. (2012), not only KL grading but also the severity of joint space narrowing (JSN; 0–3) and osteophyte formation (0–3) using the Osteoarthritis Research Society International (OARSI) atlas, and the degree of bone attrition, were taken into account. In that study, radiographs showing advanced OA (KL 3–4) were further subdivided by including data from the individual score of JSN and bone attrition.In addition, the patients included in the present study were a selection of all patients who underwent THA or TKA and it was carried out in 1 center in 1 country. However, the preoperative characteristics of the patients and their change scores over time are well in line with those observed in other large cohorts (Nilsdotter et al. 2003, Dieppe et al. 2009, Beswick et al. 2012).In conclusion, this study shows that in patients who underwent THA, but not TKA, more severe radiographic OA preoperatively was associated with a better outcome regarding pain and function.

Supplementary data

Tables 1 and 2 are available on the Acta Orthopaedica website, www.actaorthopaedica.org, identification number 8277.CT, MF, and TPMVV: conception and design, analysis and interpretation of the data, drafting of the article, provision of study materials or patients, statistical expertise, and collection and assembly of data. MJH, RLT, HMK, CSL, and SHM: provision of study materials or patients, administrative, technical, or logistic support, and collection and assembly of data. HMK and RGHHN: critical revision of the article, statistical expertise.This study was supported by the Dutch Arthritis Association (grant number LLP13).No competing interests declared.