2.3 Shoulder - Instability

Search Terms

(recurrent OR traumatic) AND (instability OR dislocation) AND (shoulder OR glenohumeral) AND (stabilization OR treatment OR management OR rehabilitation OR repair) AND (outcomes OR "patient outcomes" OR expectations OR satisfaction)

2.3.1 Definition and epidemiology

Shoulder (glenohumeral) instability is defined as a loss of function or pain experience associated with excessive translation of the humeral head in the glenoid fossa. In the context of this registry, shoulder instability includes the following:

• Traumatic capsulo-ligamentous injury
• Dislocation with associated glenoid fracture
• Atraumatic/voluntary dislocation and
• Recurrent dislocation

Dislocation or instability of the glenohumeral joint is the most common form of shoulder instability, with an incidence rate of approximately 17 per 10,000 per year (Donohue et al. 2016). Shoulder instability is predominantly seen in young males involved with sports or a physical activity, with twice as many males affected than females (Davis and Abboud 2015). The pathophysiology and aetiology of shoulder instability evolves from often traumatic dislocation in adolescence and young adulthood, to chronic and recurrent instability with advancing age due to muscle insufficiency or secondary to rotator cuff injury or degeneration (Kuhn 2010; Shea 2013).

Despite the widespread nature of glenohumeral joint instability, the definition of this condition is not clear and there is no consensus on how this disorder should be classified. Kuhn (2010) proposed a FEDS system of instability classification, to characterise shoulder instability by:

• Frequency – Solitary (1 episode), Occasional (2-5 episodes), Frequent (>5 episodes)
• Etiology – Traumatic, or Atraumatic
• Direction (primary) – Anterior, Inferior, Posterior
• Severity – Subluxation, or Dislocation

2.3.2 Treatment overview

Conservative/nonoperative management: Conservative management is utilised in cases of traumatic dislocation or instability that has not led to significant trauma to the soft tissue restraints or bony structures of the glenohumeral joint. Conservative or nonoperative management normally comprises a structured rehabilitation program focused on achieving pain-free range of motion and multi-plane strength of the musculature.

Surgical intervention: The primary objective of surgical intervention in shoulder instability is the restoration of the functional anatomy of the affected structures. This can be a complex undertaking, considering the variation of involved structures affected by traumatic dislocation or subluxation, and can complicate efforts to standardise and log treatment approaches. A myriad of associated pathologies may be observed in the dislocated shoulder, ranging from soft-tissue disruptions such as ligaments (HAGL), involvement of the labrum (SLAP tears, circumferential labral tears, anterior labral periosteal sleeve avulsions), as well as the rotator cuff tendon insertions (Forsythe et al. 2015). One of the key complicating factors is that of traumatic bone loss from the glenoid or humeral head (or both) associated with impact and/or forceful translation of the humeral head (Forsythe et al. 2015). Bone loss is a common complication of dislocation and increasing evidence suggests it should be treated as an adjunct to soft-tissue repairs to prevent recurrence (Patel et al. 2014).

Chondral and osteochondral (Hill-Sachs): Hill–Sachs lesions are compression fractures of the humeral head associated with glenohumeral dislocation. A lesion greater than 20% of the humeral head circumference may be more likely to engage the glenoid rim (Rashid et al. 2016). Multiple techniques have been developed to address humeral head bone loss, including rotational osteotomy, allograft in-fill, humeral head hemiarthroplasty or soft tissue interposition. The latter technique makes use of the tendon of infraspinatus and the posterior capsule to fill the Hill–Sachs lesion to prevent its engagement with the glenoid rim, known as ‘‘Remplissage’’ (French, meaning 'to fill in') (Rashid et al. 2016).

Labrum (with bone defect): The primary approach is an anatomical repair with the labrum restored to its anatomical position and fixed in place with sutures or anchors. However, in the case of bony defects or failure of previous stabilisation efforts or irreparable soft tissue damage, non-anatomical Bristow-Latarjet procedures may be employed as previously described (Cowling et al. 2016). In brief, the coracoid process is used as a bone graft or anchor point for reattachment of the labrum. Importantly, there are variations the original technique that may have implications for patient outcomes, including the osteotomy site, the subscapularis approach, the fixation site of the coracoid and the fixation method (Cowling et al. 2016).

Rotator cuff repair: Performed arthroscopically with an aim of restoring the functional relationship within the cuff (suturing defects) and between the cuff and the humeral head (Deprés-Tremblay et al. 2016). Variations in the number and pattern of sutures/anchors are thought to have a relationship with patient outcomes (Deprés-Tremblay et al. 2016).

Capsule/ligament/Tendon repair (biceps, SLAP, HAGL): Surgical treatment of superior labrum anterior-posterior lesions (SLAP) can involve either arthroscopic proximal biceps reattachment (SLAP repair), although less favourable outcomes have been noted in overhead athletes, older patients (>35yrs) and those with concomitant pathology (Werner et al. 2016). Alternatively, a biceps tenodesis may be performed, falling into three broad categories (Werner et al. 2016): High (at the entrance to or within the bicipital groove), low or suprapectoral (just above the pectoralis major tendon at the inferior extent of the bicipital groove), or soft tissue tenodesis, which is carried out most commonly high with suturing of the tendon remnant to the rotator interval tissue or incorporating it to the anterior extent of a concomitant rotator cuff repair. Surgical treatment of humeral avulsion of glenohumeral ligaments (HAGL) is typically by arthroscopic repair (Longo et al. 2016).

Post-surgical rehabilitation: Routinely prescribed for patients undergoing surgical procedures for shoulder instability. The current rehabilitation protocol is immobilisation of the operated shoulder with a sling for 6 weeks followed by return to shoulder motion and activity as tolerated.

2.3.3 Treatment Outcomes Summary

Treatment outcome is most commonly reported through measures of recurrent instability and patient satisfaction. While a number of factors contribute to outcomes following diagnosis of shoulder instability (Figure 2.3.a), treatment factors have a large influence on final patient outcome.

Conservative/nonoperative management: Those with atraumatic posterior shoulder instability without previous surgery tend to respond better to conservative management (McIntyre et al. 2016). However, younger patients are at substantially higher risk of recurrent instability if undergoing initial nonoperative management (Forsythe et al. 2015).

Stabilisation: The current literature shows that arthroscopic procedures are an effective and reliable treatment for unidirectional posterior glenohumeral instability with respect to outcome scores, patient satisfaction, and return to play (DeLong et al. 2015). Arciero and colleagues (1994) and Wheeler and colleagues (1989) reported a 12% to 14% rate of recurrent instability in those treated with arthroscopic repair for acute first-time anterior shoulder dislocators, compared to a 80% to 92% rate of recurrent instability in those treated nonoperatively, at 15 to 32 months of follow-up.

Bankart repair: Bankart repair of instability, using either open or arthroscopic technique, has a good success rate with reported instability recurrence of 4% to 17% (Randelli et al. 2012). Young (<40yrs) males that play at a competitive level of sport are at higher risk of recurrence of instability following Bankart repair (Randelli et al. 2012).

Latarjet Technique: The Latarjet technique is considered the “gold standard” for treatment of anterior shoulder instability in the presence of glenoid bone loss and engaging Hill-Sachs lesions due to a low rate of recurrent instability; however, stiffness with loss of external rotation and reduced ability to return to play are two potential side effects (Fedorka and Mulcahey 2015). Open Bristow-Latarjet procedures are associated with good clinical outcomes and a low rate of complications and recurrence (5.9%) (Longo et al. 2014).

Labral repair: A systematic review has found complication rates ranging from 10% to 16% following labral repair, with higher complication rates with increasing mean age (Erickson et al. 2015). Furthermore, use of labral repair with rotator cuff repair has not been observed to improve results when compared to rotator cuff repair alone (Forsythe et al. 2010).

Rotator cuff repair: In cases where shoulder instability has disrupted the rotator cuff, addressing the rotator cuff injury may restore stability and improve outcomes in line with outcomes for rotator cuff pathology (Gombera et al. 2014).

Rotator interval closure: (for gross multidirectional instability) (Coughlin et al 2018).

Biceps tenodesis: In a systematic review, 98% of patients treated with open or arthroscopic tenodesis had good or excellent outcomes (ASES mean score: 88.15-89.9; Constant mean score: 86.7-87.8) (Abraham et al. 2016). Positive outcomes have also been observed in those with SLAP tears (Griffin et al. 2017), and there is evidence that biceps tenodesis has better outcomes than labral repair in this population (Erickson et al. 2015).

2.3.4 Summary and gap

• An integrated definition of success following treatment of glenohumeral instability in its various presentations (anterior, posterior, multi-directional) has yet to be expressed.
• There is no national registry of shoulder instability or surgical treatments available for analysis.
• There is a lack of consistency in the literature in describing treatment, diagnosis and outcomes.
• Opportunity to refine surgical approaches, matched to patient presentation, through examination of variations to contemporary techniques.

2.3.5 Cohort aims and hypotheses

In patients presenting with glenohumeral instability in any direction electing to undergo stabilisation surgery, what are the patient (demographic, anatomical), pathology and management factors associated with treatment success/failure within 2 years of follow-up?

2.3.6 Cohort inclusion/exclusion criteria

Inclusion Criteria

• Diagnosed with any of the following:
  • a recent dislocation
  • clinically defined glenohumeral instability
• Traumatic capsulo-ligamentous injury
• Dislocation with associated glenoid fracture
• Atraumatic/voluntary dislocators
• Undergoing treatment by primary investigator/orthopaedic consultant surgeon.
• Consenting to being part of the Clinical Research Registry

Exclusion Criteria

• Patients with associated RC tear (RC cohort unless special case)
• Patient-reported outcomes: Clinically diagnosed mental/neurological illness (indicated on GP referral, or identified through secondary referral to psychiatric/neurological specialist) that precludes retrieval of patient feedback via interview, paper or electronic questionnaire (e.g., schizophrenia, dementia, Alzheimer's Disease, personality disorder).
• Revocation of consent for research use of personal data.

2.3.8 Cohort outcome measures

2.3.9 Cohort secondary outcome measures

Failure or Revision: When a procedure is deemed to have failed as per the definitions stated, the procedure record will be classed as “failed” using the surgery status field in Socrates and a new procedure record will be raised for the patient.

Shoulder range of motion: Active range of motion of the shoulder (glenohumeral + scapulothoracic) will be assessed as described by Sabari et al. (1998) with the patient supine (sitting, standing) with the scapula unrestrained. Testing position will be standardised (recorded at least) as per the recommendations of (Sabari et al. 1998). The patient will be asked to actively move their arm in abduction, forward flexion (abduction + flexion), as well as internal and external rotation with the humerus abducted to 90deg, without assistance from the examiner.

Clinical instability tests:

• Anterior instability will be determined with a supine apprehension test (Gerber et al 1984), graded as positive or negative; an anterior draw test (Gerber et al 1984), also with the patient supine and graded in a similar fashion to the Lachman test for the knee (0, 1, 2, 3, 4, 5); or a relocation test as illustrated by (Lo et al 2004) graded as positive or negative
• Posterior instability will be determined by a positive O’Brien test (Owen et al. 2015), based on two criteria; first, pain is elicited in a forward flexed internally rotated position, and second, this is relieved in the externally rotated position; or the posterior draw test (Gerber et al 1984), with the patient supine and graded as stable or unstable.

Complications and re-operations

Complications and re-operations are to be logged in the research database. A list of available complications can be found below.

Complication recording: Complications are recorded in the research database within the History, Surgeon Exam, F/Up and Complications window, in the Complications & Outcomes tab in Socrates.

Re-operation recording: If complications were severe enough to warrant re-operation, this must also be recorded in Socrates, with the date. An 'additional procedure' must be added here too with fields completed.

Complications specific to instability surgery include:

Infection: Surgical site infection will be determined using the diagnostic criteria proposed by Frangiamore et al (2015).

Nerve injury: The axillary nerve and musculocutaneous nerve are particularly at risk during arthroscopic stabilization (Dwyer et al. 2015; Matsuki and Sugaya 2015) and may be defined as a complication in patients if symptoms have not resolved after 6weeks from surgery.

Stabilization fixation failure/reaction: Sutures and anchors failing postoperatively and in a symptomatic patient will be logged as a complication. Patient immunoreaction to bioabsorbable materials (e.g synovitis diagnosed by imaging) will also be logged as a complication.

Deleterious bone/soft tissue remodelling: Diagnosed on imaging (MRI, CT, US) by the treating surgeon as inappropriate bone remodelling around the site of the repair or bone graft (too much or too little bone turnover).

2.3.10 Statistical analysis plan

Background

Here the pre-determined statistical analysis plan for the Shoulder Instability cohort is described, which was finalized prior to any data analysis and to which the investigators will adhere in future analyses. The statistical analysis plan was completed and approved by the registry steering committee on [insert date]. Prospective participant recruitment was commenced 22 March 2019 and following data integrity checks (as per Section 3 of this document), the cohort dataset (including retrospective data prior to launch) will be locked on an annual basis and the statistical analysis as specified below will be performed.

Analysis Objectives/Questions

The analysis plan is derived directly from the cohort questions linked below.

Design

The Shoulder Instability cohort analysis is a non-randomised observational study with census sampling (all patients presenting to the registry sites are included). Consecutive patients from the community seeking care for shoulder instability following primary care referral will be screened by the participating consultant / orthopaedic surgeon for eligibility into the analysis.

Patient inclusion/exclusion

Alterations from cohort criteria: No

Treatment allocation

Patients will be allocated to a treatment pathway (surgery, arthroplasty, non-surgical management, observation-only) as per the consultant surgeon’s clinical judgement and shared decision-making with the patient.

Sample Size

Sample size calculations were based upon a rule of thumb of 10 stabilisation failure events per variable entered into the model (Vittinghoff and McCulloch 2007), assuming a failure to cure rate of 15%. A sample size of 580 patients will have 80% power to detect a significant effect for 8 variables, allowing for up to 10% cohort protocol non-compliance and a two-sided alpha of 0.05. The failure rate is estimated from Virk et al (2016) which reported failure rates in both open and arthroscopic repair techniques in a prospective cohort study design.

Preliminaries

The flow of patients through entry into the cohort and analysis will be displayed in a flow diagram as per STROBE guidelines (Strengthening The Reporting of Observational Studies in Epidemiology) (Figure 2.3.b) (Vandenbroucke et al. 2007). The number of exclusions and loss to followup will be noted from screening, data collection and analysis phases.

Data collection and follow-up

As per registry methods. Approval is also sought to invite patients who have not previously consented to participate in research to return patient reported outcome measures for the purposes of this study.

Variations from Cohort core dataset: No

Data Integrity

Initial statistical analysis will include examining data consistency and examining outliers in more detail. Where outliers in patient reported outcomes, surgical or clinical information are identified, source material will be examined and transcription errors rectified. Where the source material contains an outlier value, a decision will be made regarding the validity of the value. This will be reported in the published results and the datum excluded from further analysis if required.

As per Section 3 - quality management

Handling missing data

Missing data will be identified during the initial data quality assessment. Missing data identified in the electronic registry database will be investigated in the original source material where available. In patients with missing data who are eligible for follow-up, attempts will be made to contact the patient (mail and phone) to complete patient-reported outcomes. When the number of patients required to achieve 80% follow up at a minimum of 1 year has been achieved, missing data rates will be reported.

Variables

As per cohort CDS

Outcomes for primary questions

Patients defined as clinically successful as defined by the treatment outcomes success criteria

Surgery/management

As per cohort core dataset

Demographics and baseline characteristics

As per cohort core dataset

Analyses

Principles (incl. blinding)

Randomisation not applied to the analyses. Analyses will be performed with de-identified data (single-sided blinding)

Primary Questions

Outlier analysis and normality will be assessed prior to a descriptive analysis of patient-reported outcomes using appropriate measures of central tendency (mean, median) and variability (95% confidence intervals). Patient-reported outcomes will be summarised using descriptive statistics as appropriate to data type (continuous, categorical). Binary logistic regression will be used to determine the association of demographic, anatomical, pathology and management factors to surgical success at up to 2 years follow up.