Introduction

The frozen shoulder condition is present in 2-5% of the general population. The condition is complex with several potential mechanisms at play. To this day, no interventions influence the natural history of the condition. The authors aim to investigate the potential role of the central nervous system by measuring the clinical impact.

Methods

A convenience sample of 10 subjects was recruited. Diagnostic criteria were as follows:

• limitation in passive external rotation of >50% compared to the unaffected side, or less than 30 degrees of rotation
• ROM loss of >25% in at least two movement planes
• pain and movement restriction for at least one month
• normal radiographs with the exception of osteopenia or calcification tendinosis

The exclusion criteria were:

• locked dislocations, arthritis, fractures, avascular necrosis
• not understanding the Spanish language
• previous upper quadrant surgery in the past year
• any skin or medical condition preventing them from receiving tactile stimuli on the shoulder
• neurological or motor disorders
• visual impairments
• diagnosed psychopathology

Outcome measures were performed at baseline and after a two-week washout period. Participants commenced the treatment program and outcomes were measured at the end of the treatment period at 3 months and 3 months out at follow-up.

The primary outcome measure was the SPADI questionnaire. Different secondary outcome measures were collected such as feasibility parameters, self-perceived shoulder pain, shoulder range of motion, tactile acuity, laterality judgment, fear avoidance, etc.

Patients were instructed on the program and explained that the homunculus can alter when people are in pain and increasing the ‘sharpness’ of the shoulder region within the homunculus could reduce pain and increase movement.

They were given 60-minute sessions, once a week, for 10 weeks.

What they were given:

• pain neuroscience education
• graded sensory discrimination training
• graded motor imagery training

Table summaries of the intervention can be found here and here.

A full explanation of the intervention can be found in the protocol here.

Results

Positive SPADI results were observed after treatment at follow-up (6 months since the start of the 10-week treatment). The SPADI scores at follow-up surpassed MDC and MCID values.

Talk Nerdy to Me

This is an interesting study with regard to treatment options within the frozen shoulder. Multiple modalities exist but none of them seem to have a profound impact on the course of the condition.

The central nervous system plays an important role in chronic conditions in the form of, but not limited to central sensitization. These central alterations might be present in sufferers of a frozen shoulder. Logically, one would investigate whether these commonly seen changes are present within this patient population. If so, hypotheses can be made regarding the treatment. However, the authors skipped a few steps here. Before we can check whether treatment X helps condition Y via altering variable Z, we need to know if variable Z is even present at all.

Imagine a doctor prescribing statins because he hypothesizes that your rotator cuff tendinopathy is metabolically driven by an abundance of LDL cholesterol in your blood, without even checking if you indeed have high cholesterol. This doesn’t make sense.

The authors try to check whether the intervention is feasible to study and while they are at it, measure a few clinical parameters such as the SPADI.

Data regarding the SPADI, or any other secondary outcome measure, is not going to be very helpful. Ten subjects are simply not enough, and to be fair, the authors mention this in their discussion. However, they cannot seem to resist the temptation of adding as many outcome measures as study subjects, which makes the collected data mathematically redundant due to a huge lack of statistical power.

Another thing worth mentioning, but possibly not critiquing, is the fact that this study is published in the “International Journal of environmental research and public health”, which is peculiar, to say the least.

The authors might be onto something regarding CNS-focused treatment but at this point in time, it is a bit far-fetched in my opinion.

Reference

Mena-del Horno, S., Dueñas, L., Lluch, E., Louw, A., Luque-Suarez, A., Mertens, M. G., … & Balasch-Bernat, M. (2022). A central nervous system focused treatment program for people with frozen shoulder: a feasibility study. International Journal of Environmental Research and Public Health, 19(5), 2628.