Radiological features are found to be importanat aspect in the decision of viscosupplementation in patients with hip osteoarthritis.

Osteoarthritis (OA) is a common articular disease that is highly prevalent in aging population and expected to grow from 11% in 2006 to 25% by 2030. The most frequent cause of lower limb OA is Hip OA (HOA) that significantly affects multiple aspects of quality of life. It is also thought to be linked to increased risk of all-cause and cardiovascular mortality among older white women. The only solution for alleviation of HOA associated pain is the total hip replacement. However, total hip replacement may lead to increase in HOA related expenses during the last decade. Patients with mild or moderate HOA or those who cannot tolerate the surgery can be treated with analgesics, non-steroidal anti-inflammatory drugs (NSAIDs), symptomatic slow acting drugs for OA (SYSADOAs), physiotherapy, rehabilitation, intra-articular (IA) steroid injections and viscosupplementation (VS). Viscosupplementation consists of IA injection(s) of a solution of hyaluronic acid (HA) and effectively reduces pain and enhances joint function by re-establishing the physiological and rheological homeostasis of OA joints. Also, VS has been established as an effective treatment for OA, but there are some conflicts in the existing data about the use of VS in the management of symptomatic HOA. The previous studies contradict the use of VS in patients with severe HOA awaiting hip replacement. In one of the retrospective study, only 1 out of 4 patients waiting for surgery was benefited with VS. The patients who did not consider surgery for short term had a high success rate (66.6%). These outcomes exhibit similarity with patients fulfilling the Minimal Clinically Important Improvement (MCII) in an uncontrolled trial. There is still a need of further research that focuses on predictive factors of response and their relationship with OA phenotype.

Rationale behind the research:

There is a lack of sufficient and clear evidences recommending the use of VS in the management of symptomatic HOA. Therefore, this study was conducted to determine the clinical efficacy of VS in the treatment of mild to moderate HOA.

Objective:

To determine the clinical, radio logical and technical factors that may exert a positive or negative influence on the response to VS in patients suffering from HOA.

Study outcome measures:

• The baseline characteristics included demographic and anthropometric data [age, gender, height, weight and body mass index (BMI)] and medical history (disease duration, analgesics and NSAIDs consumption, previous IA injections of HA or corticosteroids)

The other study outcomes included evaluation of:

• Western Ontario and McMaster Universities Osteoarthritis Index (WOMAC) and patient global assessment (PGA), on a 11 point (0–10) Likert scale
• Radiographs scoring and morphology performed by a single experienced observer (TC)
• Adverse events (AEs) using the Medical Dictionary for Regulatory Activities (MedDRA)

Time period: Baseline and 3 months

Study outcomes:

• A proportion of 47.8% of patients responded  to VS.
• The analysis of clinical outcomes depicts that only PGA in clinical outcomes was statistically and negatively related to response at baseline (p=0.047)
• There was a negative correlation found between response to VS and joint space narrowing (JSN) score (JSN < 2 vs. JSN ≥ 2, p = 0.01) and  they were related to the patterns of femoral head migration (p=0.008) in terms of radiographical features
• Multivariate analysis showed that only JSN grade (p=0.03) remained significantly related to a poor response
  

The results of this study identified predictive factors associated with response of a single IA injection in patients with HOA and emphasized the role of OA severity as a predictor of efficacy. The KL, JSN and osteophyte grades were studied, and it was determined that the severity of JSN is the best predictor of response to treatment. Previous studies have explained the anti-inflammatory and pro-anabolic effects of exogenous HA on different joint tissues such as synovium and cartilage that are helpful in improving symptom following VS. However, it is important to calculate the inflammatory and pro-catabolic profile of cartilage and synovium in case of severe OA lesions. Therefore, it was assumed that HA properties will not be enough to counteract the deleterious profile of OA tissues. A reduction in rheological properties of synovial fluid were observed due to the decrease in molecular weight and concentration of HA in OA joints, which can be partly restored by exogenous HA. But, it is assumed that VS is less efficient when deep alterations occur in rheologic properties as in severe OA.

Patients with high WOMAC pain score and PGA score at baseline exhibits a poorer result than those with medium pain level. Also, patients with low level of pain at baseline attains less successful results than those with moderate pain. The other parameters obtained were the role of patterns of femoral head migration. Patients with superomedial and axial JSN showed better improvement as compared to superolateral or posterior JSN. This observation was not clarified by the results due to a small number of patients. The study also suggested that patients with coxa profunda and FAI achieved better results than patients with hip dysplasia. Also, it was confirmed that hip and knee OA are two very different entities in terms of patient profile and treatment efficacy. There was no association found between treatment response and patient’s satisfaction.