TREATMENT OF ROTATOR CUFF TENDINOPATHY AS A CONTRACTILE DYSFUNCTION. A CLINICAL COMMENTARY

Abstract

Background and purpose

Rotator cuff (RC) tendinopathy is a common disorder affecting many individuals, both in athletic and sedentary settings. Etiology of RC pathology or the most effective conservative treatment are not totally understood. The Mechanical Diagnosis and Treatment (MDT®) method is a widely known rehabilitative technique that allows therapists to diagnose and treat spinal, and peripheral mechanical disorders. Therefore, the purpose of this clinical commentary is to briefly describe RC tendinopathy, and its management using the MDT® method.

Description of topic

RC tendinopathies are often named with several different terms, showing the difficulty related unambiguous terminology and the diagnostic process. Pathologies at the glenohumeral joint are mostly labeled according to anatomy or the impaired tissues rather than in a functional way. MDT® examination allows mechanical disorders of the shoulder to be classified into categories that show good outcomes when treated accordingly.

Relation to clinical practice

The MDT® method may offer a practical, inexpensive, and effective solution to management of RC tendinopathies that present with a mechanical component.

Level of evidence

5

BACKGROUND AND PURPOSE

Rotator cuff (RC) tendinopathy is a very common problem of the shoulder complex,^1-3 being the third most common musculoskeletal complaint,⁴ with poor long-term outcomes.⁵ Traditionally, the term tendinopathy indicates an unspecific tendon condition characterized by pain and impaired function as a result of improper tendon healing processes.^6,7 The etiology of RC tendinopathy is not fully understood,⁸ and often there are imaging signs of tendinopathy in the absence of pain and/or functional deficits,⁹ making it difficult to precisely diagnose in a patho anatomical manner.¹ General orthopaedic tests and imaging sometimes have poor reliability,^10-18 complicating the process of diagnosis, and treatment. A clinical interpretation system for RC tendinopathies based on a non-anatomical classification as described by McKenzie and May¹⁹ may help clinicians better discriminate those patients who may benefit from mechanically-based treatments. Therefore, the purpose of this clinical commentary is to briefly describe RC tendinopathy, and its management using the MDT® method.

BASIS OF ROTATOR CUFF TENDINOPATHY

RC tendinopathy etiology is still under debate,⁸ however, currently it is thought to develop when excessive loads exceed the healing capacity of tendon cells,^20,21 with the tendon failing to repair properly.^7,8 Intrinsic factors such as: age,^22,23 vascularization,^24-28 genetic components,^29,30 and extrinsic factors such as: anatomical/biomechanical problems,^31-33 capsule tightness,^34-36 muscle strength deficits,^37,38 abnormal scapular kinematics,^39-41 and posture^42,43 have been theorized as contributors to development of RC tendinopathy. With the development of RC tendinopathy, there are biochemical changes that occur in both the tendon cell population and the extracellular matrix.^21,26,^44-47 The typical changes include: an increased number of more elongated tenocytes,^21,26 thinning of collagen fibers, hyaline degeneration, chondroid metaplasia, fatty infiltrations, and an increased ratio of type III/type I collagen.⁴⁴ It appears that inflammatory cells are minimally present or may be absent in chronic tendon conditions.^48-54

DIFFICULTIES WITH DIAGNOSIS OF RC TENDINOPATHY

Specific patho anatomical diagnoses are often utilized when dealing with people with RC tendinopathy.^1,55 However, since not all shoulder conditions can be classified with a patho anatomical diagnosis¹ and as a great variety of structures may concomitantly be involved,^56-58 the reliability of making such specific structural/anatomical diagnosis regarding the glenohumeral joint is poor.^55,59 Clinical and special tests generally employed to establish diagnoses have limited validity^10-15,^60-62 and there are a growing number of researchers who suggest that imaging findings should be cautiously taken into account in the process of diagnosis making.^16-18,⁶³ Moreover, there is no documented correlation between anatomical diagnostic labels and improved clinical outcomes.⁶⁴

Some authors have gone beyond attempts at a patho-anatomic diagnosis and suggested a mechanical classification where interventions can be properly tailored¹¹,^64-67 as already successfully demonstrated in other peripheral joints.^9,68,69

MECHANICAL DIAGNOSIS AND TREATMENT APPROACH

The Mechanical Diagnosis and Treatment (MDT®) method (also known as the McKenzie® method) proposes a mechanical classification system based on patient history, symptoms monitoring, and response to repeated movements/maintained postures.¹⁹ Based on the MDT® assessment, individuals with disorders involving the extremities are classified into mechanical syndromes named: 1. Derangement 2. Dysfunction 3. Postural 4. Other.¹⁹

Derangement syndrome is theoretically caused by displacement of tissues that disrupt the normal resting position and the physiological biomechanics of a joint.¹⁹ This presents with a constant or intermittent pain and with mechanical signs that rapidly change during examination.^19,70 A directional preference is identified when movement in a specific direction (may be more than one) improves patient symptoms and mechanical signs.^71,72

Dysfunction syndrome presents with intermittent signs and symptoms attributable to loading and/or stretching of impaired tissues, for example: scarring, adherence, or faulty tissue repairs.^67,72 Symptoms abate as loading is removed and structural changes are observed in the long period. In the extremities, dysfunction syndrome can be further divided into articular, and contractile dysfunction syndromes.¹⁹

Articular dysfunction syndrome is determined by restricted active (AROM) and passive range of motion (PROM), with symptoms emerging at end range of motion (E-ROM), but not with resisted movements. Pain is therefore produced at E-ROM and abolished as soon as the joint is brought back to resting position.¹⁹ Pathology is classified as contractile dysfunction syndrome when pain is elicited during the arc of motion, with a substantially preserved ROM. Symptoms tend to arise with mid-range resisted movements and muscle elongation. In the short term, responses to movement repetitions are neither better nor worse.¹⁹

Postural syndrome occurs when there are signs due to loading of healthy soft tissue that quickly subside as soon as loading is removed. Pain is therefore intermittent, produced only by prolonged end-ranges postures that eases when the end-range position is avoided. The physical examination is normal and pathology is absent in postural syndrome. ^67,72

In case when the MDT® evaluation does not help fit the clinical presentation within any of the aforementioned classification categories, the case falls into the “other” category. This includes, for example: acute trauma, post-surgery, inflammatory pathologies, and other conditions.^19,67,72

According to a given MDT® classification, a specific exercise strategy is indicated.

RC TENDINOPATHY IN THE MDT® ASSESSMENT AS A CONTRACTILE DYSFUNCTION

Since the key concept in contractile dysfunction is the impaired muscle-tendon healing or repair, testing procedures should focus on stressing those tissues through mechanical loading, for example in the form of isometric, concentric/eccentric contractions, and/or stretching. Patients with RC contractile dysfunction syndrome are mainly either young athletes or workers in their fifties or older, who frequently perform repetitive shoulder movements. A specific event is not generally recognized as a reason of pain⁵ although the contractile dysfunction may be caused by a previous trauma, an inflammatory process, or a degenerative process.¹⁹

On physical examination A ROM and P ROM are typically preserved while pain is intermittent and absent at rest. A ROM, resisted movements and muscle-tendon stretching produce pain that easily subsides when shoulder rests. Repeated movements do not improve pain and ROM in the short term as the remodeling process in the contractile dysfunction requires time to complete.^73-75

During examination it is key to identify the target zone (if any) that basically corresponds to the most painful point through the arc of motion and at what point during that movement the pain is the highest. Commonly, the most affected movements result to be shoulder abduction/scapular plane abduction specifically between 60 ° and 120 °.⁷⁶ However, internal and external rotation or a combination of shoulder movements may also be affected.⁶⁷

MDT® as an Intervention for RC Tendinopathy.

Since controlled loading facilitates remodeling of dysfunctional tissues,^77-82 progressively loaded exercise programs for shoulder contractile dysfunction are advocated.^19,83 Programs should be selected for the symptomatic movement(s), with the aim of provoking pain that abates upon cessation of exercise. Conventionally, programs include loads that are applied progressively from a static to a dynamic manner through isometric, concentric, and eccentric training.^83,84

A typical MDT® exercise program for shoulder contractile dysfunction starts with 10 to 15 resisted isometric contractions every two hours in the target zone or at several angles of the movement if the pain is felt throughout the entire arc of motion as it is beneficial only at the angle where performed.⁸⁵ (Figure 1) If the target zone is too painful, contractions can initially be applied near the target zone.

Figure 1.

Isometric contraction in the target zone.

Sessions are then progressed to concentric training in the target zone (if any) as pain during isometric exercise improves. Otherwise, if there is not a target zone, concentric training is performed through the entire arc of motion, with light weight or an elastic resistance in the later stages. Concentric training is accomplished by abducting the involved arm (with resistance) starting from the side (Figure 2A) up to the final position (Figure 2B) where an operator removes the resistance for a new contraction. Alternatively, the subject can take off the weight with the free hand. According to symptomatic response, parameters such as: number of contractions, number of sets, angles speeds, and loads may be adjusted.⁸⁶

Figure 2.

Concentric contraction with weight. A) Initial position, B) Final position

Eccentric training is eventually employed when concentric contractions with resistance no longer provoke symptoms. The intent is to help healing, fiber remodeling, and to limit recurrance.^53,86,87 Therapeutic exercise may be applied limited to the target zone or over the entire arc of motion with a light weight in the later stages. Eccentric training is accomplished by slowing down adduction of the involved arm with resistance (in this case, elastic resistance is depicted) from an initial abducted position (Figure 3A) to the side of the subject (Figure 3B). Then an operator removes the resistance for a new contraction or the subject can take off the weight/band with the free hand. Alternatively, eccentric training may be carried out with a pulley system as performed by Jonsson et al⁸⁸ in a previous study.

Figure 3.

Eccentric contraction with elastic resistance. A) Initial position, B) Final position

DISCUSSION

RC pathology may generate from a series of problems, for example: acute/chronic inflammation, fibrosis, degenerative changes, impingement syndrome, partial or full-thickness RC tears.⁵⁶,^89-91 This makes it difficult for clinicians to differentiate between the involved structures,^56,58,92 with some researchers questioning the validity of patho anatomical classifications.^55,59 Some authors have instead demonstrated better outcomes when classifications are not made upon anatomy, but on mechanical presentation.^9,71,^93-95

The MDT® assessment and classification system has been successfully utilized with good reliability in the spine,^9,71,94,^96-107 and over a series of peripheral joints and structures,^108-113 with promising results when applied at the glenohumeral joint.^70,83,^114-118 In a survey conducted by May and Rosendale⁶⁷ among therapists with a MDT® diploma (the highest level of training), 100% of the cases were classified according to the MDT® method, with about two thirds of the cases falling into one of the three major subgroups (derangement, dysfunction and contractile syndromes). MDT® assessment may help differentiate the origin of pain, for example: spinal or peripheral,¹⁹ and may help alert clinicians to non-mechanical conditions as in cases of malignancy.¹¹⁹

Therapeutic exercise and its progression is key in the MDT® method. Mechanical loading is in fact essential for tendon homeostasis,^74,120,121 preventing negative effects of immobilization,^122,123 and helping collagen turnover of the tendon.⁵³ Treatments generally follow a progression from isometric training to eccentric training in the later stages. Since concentric training offers less tension than eccentric training, it is more suitable in the initial stages,⁸⁶ while eccentric training is generally prescribed in the later stages as it is thought to be more demanding.¹²⁴ Eccentric training has become more and more popular over the last years on tendinopathies due to research with good clinical outcomes,⁸⁸,^125-127 including research on shoulder disorders.^{79,88,128,129} Eccentric training is proposed to drive the tendon biological response by remodeling internal architecture¹²¹ through the process of mechanotransduction.⁷⁸

Although the MDT® method has an impact on signs and symptoms, it is also important to remember that RC pathology is probably due to several factors.^33,52 Therefore, combinations with other rehabilitative interventions may be beneficial when dealing with people with RC tendinopathies. As inflammation does not seem to have a primary role in tendinoapathies,^44,45,^48-54,¹³⁰ the use of anti-inflammatory drugs is discouraged as they may have negative effects on tendon healing.^131-133 Alteration of shoulder muscle ratios, shoulder dyskinesis, and posterior capsule tightness have been recognized as modifiable contributors to the development of RC tendinoapthies,^34-36,^134-140 may be addressed with specific muscle strengthening, and capsule stretching.^141-147 Therapeutic modalities may be included as they may help the healing process,⁵³ however, the evidence on modality use with shoulder tendinopathies is limited and often contradictory.^148-152

The MDT® method may not always be well accepted by patients in cases of shoulder contractile dysfunction. Pain that occurs during performance of therapeutic exercise when treating contractile dysfunctions may alert and prevent patients from continuing the exercise. However, pain that easily subsides may facilitate remodeling of RC dysfunctional tissues.^9,72,88,128 Moreover, MDT® principles of progressions appear to be safe also in cases of diagnosed partial RC tears as already documented in two previous studies.^83,115

Contractile dysfunction syndrome requires time and rigorous adherence to the exercise program in order to improve symptoms. Adherence to self-management exercises may be improved with supervised exercise therapy¹⁵³ and when care providers’ style, and content of exercise programs are positively experienced.¹⁵⁴ Finally, although contractile dysfunction shows typical features and it is relatively simple to recognize, its management according to MDT® method should be mastered by clinicians with at least a minimal knowledge of the method (The Mckenzie Institute®).

CONCLUSIONS

Due to the high prevalence of RC tendinopathy among the general and the sportive populations, the MDT® method may offer an inexpensive, and an effective solution to consider when treating musculoskeletal issue. However, more research is warranted especially on shoulder disorders.