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Patient reported outcome measures in military patients with shoulder instability
  1. Simon Middleton,
  2. P Guyver,
  3. M Boyd and
  4. M Brinsden
  1. Department of T+O, Derriford Hospital, Plymouth, UK
  1. Correspondence to Surg Lt Cdr Simon Middleton, Department of T+O, Level 11, Derriford Hospital, Plymouth PL6 8DH, UK; simonwfmiddleton{at}hotmail.com

Abstract

Objectives The Oxford Shoulder Instability Score (OSIS) is a measure of functional impairment of the upper limb, but it is unclear how it translates into military patients where lower scores, implying higher function, may still be insufficient to meet the increased demands of military service and necessitating surgery. This study aimed to compare OSIS in military and civilian patients undergoing shoulder stabilisation surgery.

Methods We undertook a prospective, blinded cohort-controlled study with a null hypothesis that there was no difference in the Oxford Instability Scores between military and civilian patient groups. 40 patients were required in each group. A prospective clinical data base (iParrot, ByResults, Oxford, UK) was interrogated for consecutive patients undergoing shoulder stabilisation surgery at a single centre. The senior author—blinded to the outcome score—matched patients according to age, gender and diagnosis. Statistical analysis showed the data to be normally distributed and a paired samples t test was used to compare the two groups.

Results 110 patients were required to provide a matched cohort of 40 in each group (70 male, 10 female subjects). Age distribution was 16–19 years (n=6); 20–24 years (n=28); 25–29 (n=16); 30–34 (n=12); 35–49 (n=12); and 40–44 (n=6). 72 patients (90%) had polar group 1 instability and eight patients (10%) had polar group 2 instability. The mean OSIS in the civilian group was 17.25 and in the military group 18.25. There was no statistical difference between the two groups (p=0.395).

Conclusions This study supports the use of the OSIS to assess military patients with shoulder instability and monitor the progress of their condition.

  • EDUCATION & TRAINING (see Medical Education & Training)
  • ETHICS (see Medical Ethics)
  • HEALTH ECONOMICS

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Introduction

Although shoulder instability can be the result of pre-existing structural abnormalities of the shoulder joint, it is usually a traumatic event that leads to the shoulder subluxing or dislocating. The age distribution of shoulder dislocation is bi-modal with a peak in the early 20s–30s and then a further peak in the older population over 60 years of age.1 This bimodal age distribution is also related to gender and location of injury with the younger group being predominantly male with the injury occurring away from the home—generally, the sports field—and the older peak comprising mostly female subjects who fall in the home.1 The elderly are injured in low energy falls and chronic instability is less of a problem when compared with the younger population injured in high energy sporting activities.2 The military has a high proportion of young men who are both active and have high functional demands. Patient reported scoring systems have been developed to measure the functional impairment in relation to day-to-day activities using the upper limb. The Oxford Shoulder Instability Score (OSIS) (Figure 1) is one such disease specific system. The routine requirements of the military are perceived to be higher than that of a similarly injured civilian population. It is unknown whether the OSIS is a useful tool in the assessment, stratification and surveillance of military patients with shoulder instability. Due to the higher functional requirements of the upper limb, military personnel may have higher preoperative scores than civilian patients. That is to say, their function is high when benchmarked against civilian counterparts, but still insufficient to fulfil their military role, thereby mandating surgical reconstruction.

Figure 1

The Oxford Shoulder Instability Score (OSIS). Reproduced with the kind permission of Isis Outcomes, Isis Innovation. Any use of the OSIS must be with a licence from Isis Innovation (http://www.isis-innovation.com/outcomes/orthopaedic/osis.html).

The aim of this study was to compare the preoperative OSIS in military and civilian patients undergoing shoulder stabilisation surgery.

Key message

The OSIS is a suitable tool to use in the management decision process of military patients with shoulder instability.

Methods

We undertook a prospective, blinded cohort-controlled study. The null hypothesis was that there was no difference in the OSIS between the military and civilian patient groups. A power calculation showed that 40 patients were required in each group to give 95% power with 5% significance to detect a difference in score of seven points.3 A prospective clinical data base (iParrot, ByResults, Oxford, UK) was interrogated for consecutive patients undergoing shoulder stabilisation surgery at a single centre. The senior author, blinded to the outcome score, matched patients according to age, gender and diagnosis. Statistical analysis showed the data to be normally distributed and a paired samples t test was used to compare the two groups.

Results

A total of 110 patients were required to provide a matched cohort of 40 in each group (70 male and 10 female subjects). The patents were distributed by age between 16 and 44 (Figure 2). In all, 36 patients (90%) had polar group 1 instability and four patients (10%) had polar group 2 instability. The mean OSIS in the civilian group was 17.25 (95% CI 15.37 to 19.13) compared with 18.25 (95% CI 16.64 to 20.11) in the military group (p=0.395).

Figure 2

Age distribution of matched patient groups.

Discussion

Patient reported outcome measures (PROMs) were introduced for routine use within the NHS in 2009 and have been used primarily to report and monitor the patient's own opinion as to the success of treatment. The main focus has been on hip and knee arthroplasty as well as surgery for varicose veins and hernia repair.4 PROMs are a way of gaining the patients’ own interpretation of their quality of life related to their general health or to a more specific disease. In our case, we are using a disease specific PROM as a means of assessing patient's ability to function while coping with the problems of instability of the shoulder. By measuring PROMs on more than one occasion it is possible to evaluate disease progression or regression and evaluate the effectiveness of treatment including surgery. We are using the score as a pretreatment starting point to conduct post-treatment surveillance, thereby quantifying the ‘value’ and efficacy of treatment from the patient's perspective.

Shoulder scoring systems have been developed over time to aid with the identification and stratification of individuals with shoulder problems. A specific shoulder instability scoring system was developed by the Oxford team following on from the original Oxford Shoulder Score (OSS). They identified a complete subset of people with instability and developed the OSIS from the original OSS.5 The OSIS is a short and validated PROM. It is condition specific and has clinical relevance accurately reflecting changes in the clinical progress of a patient. It comprises 12 questions with five options on a Likert scale. The revised system awards a minimum score of zero and maximum score of four for each question. Patients with the poorest function will score zero, while those with minimal disturbance will score higher up to a maximum of 48. The OSIS came directly from the development of the OSS on recognition of a very distinct population of patients with the specific problem of instability. The score was found to be valid, reliable and sensitive to change in a group of 92 patients.5 We wanted to know whether the OSIS was a tool that could be employed in the assessment, stratification and surveillance of military patients despite their apparent higher demand.

The shoulder instability classification in our study was developed at the Royal National Orthopaedic Hospital, Stanmore,6 and is based on three main groups: traumatic structural, atraumatic structural and habitual non-structural (muscle patterning).

By far the most common diagnosis in our population was that of traumatic structural abnormalities. This reflects the most common type of instability. The vast majority of patients in the military group were young and as already discussed are likely to have trauma as the primary cause of their instability.

It has been demonstrated that military populations are at higher risk of suffering dislocations and as a result of that there will be a higher prevalence of shoulder instability than would be found in a similar civilian population. In US Military personnel an incidence of 1.69 per 1000 person-years has been demonstrated compared with the general US population incidence of 0.08 per 1000 person-years.7 This means that there is the possibility of shoulder instability having a significant impact on the military with individuals not fit to perform their primary role. Thus, those in the military who have shoulder instability and cannot perform their primary role are more likely to be offered a surgical solution.

Conclusions

Our study demonstrated that there was no statistical difference between the scores of the military and civilian patients who required surgery for their shoulder instability. Therefore, we can conclude that it is reasonable to use the OSIS in the assessment of military patients with shoulder instability.

References

Footnotes

  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.