One of the greatest risks following an anterior shoulder dislocation is damage to the neurovascular structures which surround the glenohumeral joint. Due to their anatomical location, certain nerves are at a higher risk of injury than others following a dislocation. Additionally the position and displacement of the arm during the injury is another factor to consider. For example, "a fall with the arm in full abduction and internal rotation causes major tension on all nerves and cords." The Visser et al article also mentioned that concurrent fractures and the presence of a hematoma increasead the risk of nerve damage. Nerves that are at the greatest risk of injury include the axillary, suprascapular, and musculocataneous nerves. Throughout the literature, authors have found that the axillary nerve is most frequently and severely damaged (Visser).
The axillary nerve originates from the upper trunk, posterior cord of the brachial plexus carrying nerve fibers from C5-C6. It courses around the surgical neck of the humerus before entering the quadrilateral space (see middle picture below to review the space boundaries). The nerve gives off muscular branches to the deltoid, teres minor, and long head of the triceps brachii. Due to the close association to the surgical neck, the axillary nerve is often compromised during an anterior-inferior shoulder dislocation. A study by Visser et al found that 42% of their 77 patients had axillary nerve insult following a low-velocity trauma anterior shoulder dislocation.
Due to the high incidence of nerve related injuries, a complete neurovascular examination is warranted following a shoulder dislocation. This examination should include MMT of the shoulder and arm musculature, palpating for the brachial pulse, and examining sensation of the arm. When assessing for axillary nerve damage in particular, a clinician should look for muscle atrophy of the teres minor and deltoid muscles. One should suspect weak flexion, abduction, and external rotation of the shoulder. Observation and palpation would reveal a flat shoulder deformity due to deltoid atrophy. Additionally, they will have a lose of sensation over the upper lateral arm around the deltoid region due to denervation of the superior lateral cutaneous nerve of the arm (see right picture above).
Visser, C. P. J., L. N. J. E. M. Coene, R. Brand, and D. L. J. Tavy. "The Incidence of Nerve Injury in Anterior Dislocation of the Shoulder and Its Influence on Functional Recovery." The Journal of Bone and Joint Surgery 81.4 (1999): 679-85. Web.
In recent years, Physical Therapy research has emerged that compares surgical interventions to placebo surgeries. For certain conditions, there is now fairly substantial evidence that surgical intervention is not always necessary despite what is considered standard societal practice. The most recent example of this is a December 2013 article written by Sihvonen et al, that investigated arthroscopic surgical menisectomy compared with placebo surgery for individuals with degenerative meniscal tears. The results were pretty interesting! In a recent post by Leonard van Gelder at Dynamic Principles, he discusses the reasons behind why this appears to continually be happening & gives several good examples of when conservative management is either more successful or equally successful as surgery.
Questions you need to ask yourself:
-If patients have similar results in surgery vs. placebo surgery, what is at fault in the patient? The mechanical system cannot solely be the answer. The answer lies in the patient's belief system regarding tissue healing and surgery.
-How should this change the type of education you give a patient regarding certain conditions?
-How do you manage a patient that strongly believes surgery is the answer (after a disc herniation for example) despite knowing that surgery is not always the best course of action.
(As Leonard discusses in his post, we are well aware that certain conditions require surgical intervention. By no means are we saying surgery is a bad thing. We are simply bringing light to certain conditions that respond positively from conservative management.)
Dosage is one of the most important factors to consider when prescribing an exercise. This decision is often made based off level of acuity, tissue type, anatomical location, patient age, and more. In school, one learns the general principles of exercise prescription, but what is often neglected is WHY you prescribe in certain ranges. "Mechanotherapy: how physical therapists' prescription of exercise promotes tissue repair" is a 2009 article published in the Journal of Sports Medicine that elaborates on this topic.
Physiologically, what stimulates tissue repair of articular cartilage, muscles and tendons is a term called Mechanotransduction. In this article Mechanotransduction is defined as "the process by which the body converts mechanical loading into cellular responses." This can be thought of in clinical terms as what is occurring at the histological level to allow one to prescribe a certain exercise dosage without increasing the risk of injury.
Mechanotransduction can be broken down into 3 phases:
1) Mechanocoupling: This is the physical load cells undergo while in repair. The physical load is transferred into chemical signals which stimulate cellular changes.
2) Cell-Cell Communication: When one cell is stimulated, other cells in the area (whether directly stimulated by the initial mechanical stimulus or not) will undergo a cellular response.
3) Effector Response: When a cell is mechanically stimulated through compression, distraction, etc., several processes will occur intrinsically to allow change to occur.
Now knowing each of the 3 stages, you must think about them in relation to the Type of Tissue involved to understand how that tissue heals.
When a tendon is trying to heal, there is up-regulation of insulin-like growth factor, other growth factors, and cytokines which allows for cellular proliferation and tissue remodeling. Because healing is occur at the cellular level, too much stress OR too little stress on the tendon tissue could cause an alteration in the up-regulation, not allowing the tendon to rehabilitate optimally. The research up-to-date shows that tendons responds positively to "controlled loading." Research focusing on the type and intensity of controlled loading (eccentrics, assisted, resisted) is still ongoing.
The authors Khan and Scott state that "muscle offers one of the best opportunities to exploit and study the effects of mechanotherapy" because of how muscle tissue responds to loading. We know there is an overload of mechanogrowth factor (MGF) released when load is induced on the muscle force. This in turn causes muscle cell hypertrophy due to a cell-to-cell communication with nearby satellite cells. At this point, the research shows that early loading after a brief immobilization period is essential for minimizing atrophy and restoring normal cellular structure of the muscles.
Articular cartilage is comprised of a large population of mechanosensitive cells. It is hypothesized that by repetitively stimulating the articular cartilage with a low load/high repetition exercise dosage, better outcomes will result. One study assessing full thickness cartilage defects following periosteal transplantation demonstrated that individuals who used continuous passive motion (low load/high repetitions) had greater outcomes than those who did not receive this intervention. As with all things, research is ongoing.
When assessing bone healing, osteocytes are the primary mechanosensors. A recent study looking at individuals following a distal radius fracture had stronger bone growth if they received intermittent compression as an adjunct to the standard of care (compression & gripping exercises). The pneumatic compression allowed for extra stimulation of the bone cells and an increased healing rate.
We know parts of this article are dense, but understanding what is occurring at the cellular level can greatly change your viewpoint of how various tissues heal. Through each of these tissues we can see that Mechanotherapy plays a unique role in healing of different tissues types. The healing of osteocytes differs from that of chondrocytes which differs from myocytes. It is fundamental to understand these differences in order give appropriate doses during exercise - just as it is important to know the tissue type you should be treating following your examination.
As a general rule of thumb: Articular Cartilage: Low Load, High Repetition; ~15% 1 RM; Thousands of repetitions.
Tendon: Controlled Loading; consider eccentric exercises, but do not overload the tissue. Muscle: allow for a brief period of immobilization to restore homeostasis following injury. Bone: Based on location of the fracture, consider adding compression to your treatment to improve rate of bone growth and decrease healing time.
Khan and Scott. (2009) "Mechanotherapy: how physical therapists' prescription of exercise promotes tissue repair."
British Journal of Sports Medicine. 2009; 43: 247-251. Web. 5 Dec. 2013.
Subacromial Impingement Syndrome (SAIS) is reported to be the most frequent cause of shoulder pain in an OP physical therapy clinic. Despite the high prevalence, physical therapists still struggle to appropriately diagnose the syndrome. The gold standard for diagnosing SAIS in arthroscopic surgery. Since we do not have access to this tool everyday, we must reply on our patient examination skills. A study by Michener et al, Reliability and Diagnostic Accuracy of 5 Physical Examination Tests and Combination of Tests for Subacromial Impingement, assessed 5 special tests commonly used to help rule-in SAIS. The 5 tests were Neers, Hawkins-Kennedy, Painful Arc, Empty Can (Jobe), and External Rotation Resistance Test. Specifically this article wanted to assess the interrator reliability of the tests, diagnostic accuracy of each test, and finally if clustering the tests would confirm or rule-out SAIS.
The results of the study were surprising. Moderate to Substantial strength of agreement between raters was found for the empty can test, the painful arc sign, and external rotation resistance test. Surprisingly Hawkins Kennedy had the lowest kappa value at .39. We found this surprising because Hawkins-Kennedy is graded as painful or not painful. There seems to be little room for subjectivity, yet it received the lowest reliability among raters of all the tests. The difference likely lies in how the test is performed and thus perceived. It is easy to forget to not horizontally adduct the shoulder sufficiently or to ignore the patient's compensation of elevating the tested shoulder during IR as a means of avoiding/minimizing the pain provocation. Something we must always be wary of in studies of manual techniques is accepting the fact that all examiners perform/analyze movements the same.
When looking at the diagnostic accuracy of each test individually, the External rotation resistance test had the highest positive likelihood ratio (LR) of 4.39, empty can had the second highest with 3.9, and the painful arc sign came in third at positive LR 2.25. Finally, the article found that when clustering the tests a "combination of any 3 positive tests out of the 5 have the best ability to confirm SAIS, with small to moderate shifts in the pretest to posttest probability."
While this article provides interesting and useful clinical information, the results are different from other studies in the literature. A separate article on SAIS by Park et al found that the clustering Hawkins-Kennedy, Infraspinatus Muscle Test, and the Painful Arc Sign yielded a high +LR (10.56) for ruling-in SAIS. So what cluster should you use? Personally, we would use both. The etiology of SAIS is multifactorial. Several structures have the potential to be pain generators and the presentation of SAIS will vary based on posture, scapulohumeral rhythm, accessory joint mechanics, and more. The Michener article was quick to point out the importance of a thorough subjective history to help aide in the diagnostic process.
Reference: Michener LA, Walsworth MK, Doukas WC, Murphy KP. Reliability and diagnostic accuracy of 5 physical examination
After doing some reading about regional interdependence for the SFMA inservice, we thought it would be interesting to look at some research regarding thoracic spine manipulation for shoulder pathologies, especially with the evidence for thoracic manipulations for neck pain. Regional interdependence is the idea that impairments in a separate anatomical area can contribute to the patient's primary complaint. Due to the seemingly unconventional connection between the thoracic spine and shoulder, it may appear unusual to treat shoulder pathologies with t-spine manipulations, but let's remember that limited thoracic mobility can affect the shoulder position and potentially lead to pain. There have been several studies looking at this relationship, and others. Overall, there is a decent amount of evidence displaying short-term pain relief following thoracic manipulation for shoulder pathologies, such as shoulder impingement syndrome or rotator cuff tendinopathy, even though the mechanism is poorly understood. This could potentially hasten the rehabilitation process, by allowing more aggressive therapy.
Therapeutic Ultrasound: Why it works?
Following a stress fracture, there is increased osteoclastic resorption, which leads to periosteal damage. The increased resorption allows for increased heat absorption during ultrasound; therefore stimulating pain receptors at the site of injury. Additionally, mechanical waves from the ultrasound can become trapped between any break in the bone, which can stimulate periosteal nocioceptors.
The Tuning Fork: Why it works?
Following a stress fracture, the bone periosteum is damaged. Under normal conditions, the intact periosteum has the ability to disperse vibratory forces across the bone. The damaged periosteum of a stress fracture, absorbs increased vibratory forces and stimulates pain receptors.