Any abnormality that disrupts the intricate relationship within the subacromial space may lead to impingement. Both intrinsic (intratendinous) and extrinsic (extratendinous) factors have been implicated as etiologies of the impingement process. The role of muscle weakness within the rotator cuff has been described as leading to tension overload, humeral head elevation, and changes in the supraspinatus tendon, which is used most often in high-demand, repetitive overhead activities.8,9 Authors^10–12 also have described inflammation and thickening of the bursal contents and their relationship to the impingement syndrome. Jobe¹³ and Jobe, Kvitne, and Giangarra¹¹ studied the role of microtrauma and overuse in intrinsic tendonitis and glenohumeral instability and their implications for overhead-throwing athletes. Intrinsic degenerative tenopathy also has been discussed as an intrinsic cause of subacromial impingement symptoms.¹⁴

Extrinsic or extratendinous etiologic factors form the second broad category of causes of impingement syndrome. Rare secondary extrinsic factors (e.g., neurologic pathology secondary to cervical radiculopathy, supraspinatus nerve entrapment) are not discussed here, but the primary extrinsic factors and their anatomic relationships are of primary surgical concern. The unique anatomy of the shoulder joint sandwiches the soft tissue structures of the subacromial space (i.e., rotator cuff tendons, coracoacromial ligament, long head of biceps, bursa) between the overlying anterior acromion, AC joint, and coracoid process and the underlying greater tuberosity of the humeral head and the superior glenoid rim. Toivonen, Tuite, and Orwin¹⁵ have supported Bigliani, Morrison, and April’s description¹⁶ of three primary acromial types and their correlation to impingement and full-thickness rotator cuff tears. AC degenerative joint disease also can be an extrinsic primary cause of impingement disease.^1,2 Many authors support Neer’s original position on the contribution of AC degenerative joint disease to the impingement process.^17,18 The os acromiale, the unfused distal acromial epiphysis, also has been discussed as a separate entity and a potential etiologic factor related to impingement.¹⁹ Glenohumeral instability is a secondary extrinsic cause or contribution to impingement. Its relationship to the impingement syndrome is poorly understood, but it helps explain the failure of acromioplasty in the subset of young, competitive, overhead-throwing athletes with a clinical impingement syndrome.^11,20,21

History and physical examinations are crucial in diagnosing subacromial impingement syndrome. Findings may be subtle, and symptoms may overlap in the various differential diagnoses; therefore, appreciating the impingement syndrome symptom complex may be difficult. The classic history has an insidious onset and a chronic component that develops over months, usually in a patient over 40 years old. The patient frequently describes repetitive activity during recreation, recreational sports, competitive athletics, and work. Pain is the most common symptom, especially pain with specific high-demand or repetitive away-from-the-chest and overhead shoulder activities. Night pain is seen later in impingement syndrome, after heightening of the inflammatory response. Weakness and stiffness may occur secondary to pain inhibition. If true weakness persists after the pain is eliminated, then the differential diagnoses of rotator cuff tearing or neurologic cervical entrapment type of pathologies must be addressed. If stiffness persists, then frozen shoulder–related conditions (e.g., adhesive capsulitis, inflammatory arthritis, degenerative joint disease) must be ruled out.22 Younger athletic and throwing patients need continual assessment for glenohumeral instability.

The physical examination of a patient with impingement syndrome focuses on the shoulder and neck regions. Physical examination of the neck helps rule out cervical radiculopathy, degenerative joint disease, and other disorders of the neck contributing to referred pain complexes in the shoulder area. The shoulder evaluation includes a general inspection for muscle asymmetry or atrophy, with emphasis on the supraspinatus region. Range of motion (ROM) and muscle strength testing and generalized glenohumeral stability testing are emphasized during the evaluation. The Neer impingement sign² and Hawkins-Kennedy sign²³ are gold standard tests to help diagnose impingement. The impingement test, which includes subacromial injection of a Xylocaine type of compound and repeated impingement sign maneuvers, is most helpful in ascertaining the presence of an impingement syndrome. The AC joint also is addressed during the shoulder evaluation. The clinician should note AC joint pain with direct palpation and pain on horizontal adduction of the shoulder. Selective AC joint injection also may be helpful. Long head biceps tendon pathology, including ruptures, is rare but may occur in this subset of patients. Physical examination will define the tendon’s contribution to the symptom complex. Instability testing, especially in the younger athletic patient, also should be performed. The clinician should assess for classic apprehension signs and perform the Jobe relocation test, recording any positive findings.

Standard radiographic evaluation is carried out with special attention to anteroposterior (AP), 30° caudal tilt AP, and outlet views of the shoulder.24,25 These plain studies are helpful in demonstrating acromial anatomy types, hypertrophic coracoacromial ligament spurring, AC joint osteoarthrosis, and calcific tendonitis. These views, in combination with an axillary view, can uncover os acromiale lesions. Magnetic resonance imaging (MRI) also is helpful in revealing relationships in impingement syndrome, especially if rotator cuff tear and other internal derangement pathologies (e.g., glenolabral or biceps tendon pathologies) are suspected.²⁶

Both open acromioplasty and the arthroscopic SAD procedure are discussed in the following sections. Open acromioplasty techniques have been well documented, their outcomes have been well researched, and their results have been rated as very good to excellent in numerous studies.1,27,29,30,35 Because of these factors and the high technical demands of arthroscopic decompression, surgeons should never completely abandon this proven technique for the surgical management of persistent shoulder impingement. Surgeons also may resort to these open techniques in the event of arthroscopic procedure failure or intraoperative difficulties. Depending on surgical experience and expertise, an open procedure may be used in deference to an arthroscopic SAD procedure.

Arthroscopic SAD for the surgical treatment of impingement syndrome has a number of advantages. First, the arthroscopic technique allows evaluation of the glenohumeral joint for associated labral, rotator cuff, and biceps pathology, as well as assessment of the AC joint and surgical treatment of any condition contributing to impingement. Second, this technique produces less postoperative morbidity and is relatively noninvasive, minimizing deltoid muscle fiber detachment. However, arthroscopic SAD is a technically demanding procedure with a learning curve that can be higher than for other orthopedic procedures.

Many different arthroscopic techniques have been described, but the authors of this chapter recommend the modified technique initially described by Caspari.³⁶ The patient is usually anesthetized with both a general and a scalene block regional anesthetic. In most community settings this combination has been highly successful in allowing patients to have this procedure done on an outpatient basis. A scalene regional block and home patient-controlled analgesia (PCA) provide acceptable pain control and ensure a comfortable postoperative course.

After the patient has reached the appropriate depth of anesthesia, the shoulder is evaluated in relationship to the contralateral side in both a supine and a semisitting beach chair position. Any concern regarding stability testing can be further assessed at this time, taking advantage of the complete anesthesia. Then, using the standard beach chair positioning, the surgeon begins the arthroscopic procedure. An inflow pressure pump (Davol) is used to maintain appropriate tissue space distention. Epinephrine is added to the irrigation solution to a concentration of 1 mg/L, thus enhancing hemostasis.

Specific portal placement is important to eliminate technical difficulties. Carefully addressing the palpable bony topography of the shoulder and marking the acromion, clavicle, AC joint, and coracoid process greatly facilitate portal placement (Fig. 3-1). First, the sulcus is palpated directly posterior to the AC joint. From this universal landmark, appropriate orientation can be obtained and consistent reproducible posterior, anterior, and lateral portal placement can be achieved.

Using the standard posterior portal, the surgeon inserts the arthroscope into the glenohumeral joint. In a routine and sequential fashion, the glenohumeral joint is evaluated with attention directed to the biceps tendon and the labral and rotator cuff anatomy. Any incidental pathology can be addressed arthroscopically at this point. Subacromial space arthroscopy can now be performed.

For subacromial procedures, a long diagnostic double-cannula arthroscope is recommended. The cannula with a blunt trocar is placed from the posterior portal superior to the cuff, and exits through the anterior portal.

Using this cannula as a switch stick equivalent, the surgeon places a cannula with a plastic diaphragm over the arthroscopic instrument and returns it to the subacromial space. Gently retracting the arthroscopic cannula and inserting the arthroscope allows the inflow and arthroscopic cannulas to be close together. Adequate distention and maintenance of inflow and outflow are crucial for visualization and indirect hemostasis. This technique has been successful in achieving these goals. At this point the lateral portal is fashioned, generally on the lateral aspect of the acromion just posterior and inferior to a line drawn by extending the topographic anatomy of the anterior AC complex (see Fig. 3-1). A spinal needle may assist in the accurate placement of this portal, which is crucial to instrument placement and subsequent visualization.

Starting from the posterior portal and using an aggressive synovial resector with the inflow in the anterior portal, the surgeon uses the lateral portal to perform a bursectomy and débride the soft tissue of the subacromial space. This is done in a sequential manner, working from the lateral bursal area to the anterior and medial AC regions. Spinal needles can be placed in the anterolateral and AC joint region to facilitate visualization and reveal spatial relationships. After the subacromial bursectomy and denudement of the undersurface of the acromion, the superior rotator cuff can be visualized along with the AC joint and anterior acromial anatomy is more easily defined. The surgeon must take care not to violate the coracoacromial ligament during this initial bursectomy procedure.

At this point the surgeon inserts the arthroscope in the lateral portal for visualization. Using the posterior portal and following the posterior slope of the normal acromion, the surgeon performs sequential acromioplasty with an acromionizer instrument. In the technique described by Caspari,³⁶ the shank of the acromionizer is directed flat against the posterior acromial slope and acromioplasty is completed from the posterior to the anterior aspect. This accomplishes two goals. First, it provides a reliable and reproducible template to convert any abnormal hooked, sloped, or curved acromion to the therapeutic goal of a flat, type I configuration. Second, it allows for the removal of the coracoacromial ligament from its bony attachment with minimal chance for coracoacromial artery bleeding, thereby maximizing arthroscopic visualization and minimizing technical difficulties. At this point any further modification or “fine tuning” may be done through both the lateral and the anterior portals. Any residual coracoacromial ligament is removed from its acromial insertion while its bursal extension is excised.

The AC joint also may be assessed at this stage, and minimal inferior osteophytes may be excised. Depending on the results of the preoperative evaluation, distal clavicle procedures can be performed at this point either through directed arthroscopic techniques or, as the authors of this chapter prefer, through a small incision located over the AC joint region. If AC joint symptoms are present with horizontal adduction and direct palpation, if radiographs confirm the pathology, or if both occur, then the surgeon should proceed with a distal clavicle excision. A T-type capsular incision is located over the AC joint region, with the anterior and posterior capsular leaves elevated subperiosteally from the distal clavicle. Using small Homan retractors, the surgeon can excise the distal clavicle (usually 1.5 to 2 cm) with an oscillating saw. The distal clavicle can then be easily palpated and rasped smooth. With a simple digital confirmation, the undersurface of the acromion also can be checked and any residual osteophytes rasped through this minimal-incision technique.

The soft tissue is then closed in anatomic fashion, with essentially no deltoid detachment. A routine subcuticular skin closure is used. The patient is placed in a postoperative pouch sling, and cryotherapy is frequently suggested. The patient is discharged to continue treatment as an outpatient; if insurance or health demands require it, overnight observation is used. Physical therapy may begin immediately on the first postoperative day and should follow the standard program discussed previously.³⁶

The surgical outcomes for arthroscopic SAD, partial acromioplasties, and distal clavicle excisions16,32,33 have been most favorable. Many studies have compared open and closed techniques and obtained similar overall findings.^19,35,37 SAD procedures have three general goals:

Every rehabilitation program begins with a thorough evaluation at the initial physical therapy visit. This evaluation provides pertinent information for formulating a treatment program. As the patient progresses through the program, assessment is ongoing. Activities that are too stressful for healing tissue at one point are reassessed when the tissue is ready for the stress. Measures to be included in the physical therapy evaluation are provided in Box 3-1.