History
An 18-year-old athletically active female university student presented to the Murdoch University Chiropractic Clinic complaining of bilateral upper trapezius pain. She commented that she thinks she is "double jointed" because her shoulder "pops in and out of joint". The patient stated that she had had this shoulder dysfunction as long as she could remember. It had never caused her pain or limited her activities of daily living (ADL's), including rowing and playing stringed instruments; however she would prefer to not have the dysfunction. She denied any shoulder trauma or knowledge of any personal or family history of connective tissue disorders. Relevant medical history included a 20°C scoliotic curve at 11-years-of-age which progressed to 30°C in six months; after being braced for 1.5 years the curve decreased to 24°C and stabilised.
Examination
The patient did not exhibit antalgia, and there was no obvious deformity of the left shoulder apparent upon static observation. Appearance and temperature of the skin about the neck, shoulders, and thoracic region were unremarkable, but generalised muscle tone and bulk at the left shoulder were subjectively decreased when compared to the right. Active range of motion (AROM) and passive range of motion (PROM) of both shoulders were full and pain-free in all directions. However, it was noted that the patient's left shoulder appeared to subluxate (or dislocate) and relocate from the glenoid fossa regularly between 75°C and 180°C of abduction. This dislocation/relocation pattern also appeared to occur to a lesser degree during flexion of the left shoulder. Manual muscle testing of the shoulder musculature revealed a mild weakness of the left supraspinatus (4/5). The neurological examination was unremarkable. Impingement tests were negative for pain, but excessive internal rotation of the left shoulder was demonstrated during Hawkins-Kennedy test [19] when compared to the right. Anterior instability tests were also pain-free, but positive for laxity on the left. A chiropractic examination did not reveal any suggestion of manipulable lesions in the shoulder complex.
Functional examination
Observation of scapulohumeral rhythm revealed early lateral rotation of the left scapula, possibly due to chronic aberrant motor patterns including an early facilitation of the trapezius musculature and delayed serratus anterior and lower trapezius muscles. As a result, the normally smooth arc of shoulder abduction between 75°C and 180°C was punctuated by sharp, clunking, jerking movements which appeared to be due to the humerus repeatedly slipping from the glenoid fossa (see Additional file 1). The patient was instructed to co-contract her shoulder during abduction. This involved training the patient to contract the pectoralis minor, serratus anterior, subscapularis, latissimus dorsi and lower trapezius muscles. This complicated manoeuvre was facilitated by the clinician lightly pinching the posterior axilla muscle groups (latissimus dorsi and lower trapezius) by placing her fingers in the axilla from behind and having her thumb on the posterior aspect of the lower trapezius muscle, and then asking the patient to "contract these muscles". While co-contracting this muscle group and instructing the patient to perform the abduction movement, it was noted that the aberrant glenohumeral rhythm did not occur until the end range of the movement. There were also fewer episodes of glenohumeral clunking, allowing the patient to achieve a smoother arc of movement (see Additional file 2. Note: the patient performs abduction on the right demonstrating a normal movement pattern. She then performs an abduction manoeuvre on the left; first without co-contraction, then a second time with co-contraction).
Additional File 2: Video 2. Gross range of motion into abduction; right shoulder normal, left shoulder first demonstrates the aberrant glenohumeral rhythm, the patient is instructed to co-contract the left shoulder complex resulting in an immediate near-normal abduction rhythm. (MOV 1 MB)
Radiological examination
Radiological investigation was ordered to rule out an anatomical aetiology (such as shoulder joint dysplasia) and confirm or deny an aberrant motor pattern as the sole cause of dysfunction. This consisted of plain film radiography and video fluoroscopy. A left shoulder series consisting of AP internal rotation, AP external rotation, and AP weighted (3 kg) neutral views (all taken in Grashey position [20]) revealed no bony dysplasia (Figures 1, 2, 3). Video fluoroscopy consisting of AP and axial projections confirmed the suspicion that the humerus subluxated inferiorly at the glenohumeral joint as it moved through the abduction arc. The axial projection showed a significant posterior component to this subluxation. A follow-up projection AP projection with co-contraction of the shoulder showed that these newly combined motor patterns kept the glenohumeral joint stable, making the arc of motion smoother, and reducing the dynamic subluxation. When viewing the following videos note the significant dysrhythmia for 4 repetitions followed by a smoother rhythm from the patient's conscious facilitation of co-contraction (see Additional file 3).
Additional File 3: Video 3. A fluoroscopy of the involved shoulder; the first four abduction movements demonstrate the aberrant pattern specifically the early lateral rotation of the scapula and multiple subluxation tendencies of the glenohumeral joint. The following four abduction repetitions demonstrate a much smoother rhythm while the patient was co-contracting the shoulder complex. (MOV 10 MB)
Clinical diagnosis
Chronic, severe, non-traumatic, multidirectional instability of the left glenohumeral joint secondary to ligamentous laxity. This was accompanied by glenohumeral kinesio-pathology and aberrant scapulohumeral rhythm due to suboptimal motor patterns.
We opine that this unusual presentation was associated with facilitation of the upper trapezius with suspected inhibition of the subscapularis, lower trapezius, latissimus dorsi, serratus anterior and possibly the remaining rotator cuff. Without further EMG studies, this is simply the author's clinical opinion.
Treatment Plan
Given the unusual presentation of this case, choice of therapy was problematic. The patient expressed a disinterest in surgery to correct the potential capsular laxity. Considering the lack of pain and the chronicity of the dysfunction, a conservative approach was recommended to the patient.
The goals of treatment were to decrease the dysfunction in her shoulder movement by improving the development of optimum motor patterns and improving muscular balance of the shoulder girdle.
Monfils, et al [21] state that "motor skill acquisition occurs through modification and organization of muscle synergies into effective movement sequences".
Because of the documented importance of muscle synergy and the progressions of motor control and stabilizer function [18] we decided to employ the General Functional Assessment Pyramid (Figure 4).
Re-assessment
The patient was seen fortnightly for several weeks and was reassessed at every visit. The patient's initial trapezius complaint resolved within the third treatment. The single most important outcome measure utilised was the degree of shoulder abduction (performed while co-contracting the shoulder) obtained before dysfunction (subluxation-relocation) resulted.
Degree of left shoulder abduction before subluxation-relocation results are detailed in Table 1.
At six weeks it was also observed that the patient could abduct her left shoulder to 105°C without conscious contraction of the glenohumeral and scapular stabilisers before dysfunction resulted. That was an improvement from the baseline of 75°C.