Considerations.

Patients sometimes ask, “Why can’t you just use an arthroscope to clean the arthritis out of my shoulder?” We know, however, that because glenohumeral arthritis is a condition in which articular cartilage is lost, the arthritis cannot be “cleaned out.” In most cases simply removing the osteophytes will not improve shoulder comfort and function unless the osteophytes are clearly restricting the range of motion and the joint surfaces are functional. Aspects of glenohumeral arthritis that could potentially be addressed arthroscopically include loose body removal ( Fig. 60.155 ), the release of capsular contracture, and resection of synovitis in cases of inflammatory arthropathy refractory to medical management. Beneficial results have been reported from arthroscopic debridement for glenohumeral arthritis without or with microfracture and without or with glenoid recontouring. However, rigorous evaluation of the outcome is complicated by the inconsistent inclusion of procedures, such as surgery on the subacromial space, acromioclavicular joint, or biceps tendon. It can be concluded from the published results for arthroscopic treatment that this can be successful in early instances of the disease before substantial destruction of the joint has occurred or for osteochondral lesions that are localized. ^{, ,} Because such mildly involved shoulders may also improve with nonoperative management, it is important to determine the value of arthroscopic management using carefully controlled studies. The outcome of arthroscopic debridement is worse for shoulders with involvement of the joint surfaces of both the glenoid and the humerus, that is, true glenohumeral arthritis. ^, A recent systematic review found that there was insufficient evidence to support the routine use of arthroscopic debridement for glenohumeral arthritis. Another concluded that isolated arthroscopic debridement and capsular release did not provide sufficient benefit to justify its use in most patients. Microfracture appears to be of little benefit except for small localized defects in either the humeral or the glenoid joint surface. ^, It is important to note that arthroscopic surgery is still surgery, carrying costs and risks. A carefully controlled trial found that arthroscopic surgery for arthritis of the knee was no more effective than sham surgery (which, by the way, resulted in significant clinical improvement, illustrating the need for surgical controls).

Loose body delivered by palpation from the subscapularis recess.

Open

Debridement and capsular release.

In a small number of cases of early arthritis—especially where there is substantial limitation of motion with relatively preserved joint surfaces—a debridement and capsular release may be considered for patients who wish to avoid a prosthetic arthroplasty, although it should be recognized that subsequent surgery may well be needed. This procedure is performed through the same skin incision as would be used for a joint replacement ( Fig. 60.156 ). The shoulder is approached through a subscapularis tenotomy ( Fig. 60.157 ), and adhesions in the humeroscapular motion interface are released ( Fig. 60.158 ). The subscapularis is released from the glenoid along with the attached subjacent anterior capsule ( Figs. 60.159–60.162 ) to allow a good range of passive motion ( Fig. 60.163 ). If there is a tendency for posterior instability, the capsular release is limited to the anterior aspect of the glenoid ( Fig. 60.164 ). Loose bodies, osteophytes, and interfering soft tissue are removed. The joint is thoroughly irrigated and gently manipulated to achieve the maximum possible range of passive motion, and the subscapularis is securely repaired ( Fig. 60.165 ). After surgery, a range of assisted motion exercises are immediately implemented. As with arthroscopic debridement, data on the effectiveness of this procedure are limited. I use it sparingly in cases of relatively early arthritis, especially in capsulorrhaphy arthropathy, where the anterior soft tissues have previously been tightened in the treatment of anterior instability (see Fig. 60.89 ). ^,

Incision.

The skin incision for the extended deltopectoral approach (dashed line) uses the mid-clavicle, the tip of the coracoid process, and the deltoid tuberosity of the midhumerus as landmarks. It is important that the incision avoid the axillary crease; otherwise, painful scarring might result.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:515.)

Subscapularis tenotomy approach. The subscapularis tendon is divided medial to its insertion on the lesser tuberosity.

Nerve-to-nerve release. All scar tissue in the humeroscapular motion interface (arrows) is released medially from the axillary nerve as it crosses the subscapularis, then under the coracoid, under the coracoacromial ligament, under the acromion, and finally under the deltoid to the axillary nerve posteriorly as it exits the quadrilateral space.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:517.)

Releasing the coracohumeral ligament. The coracohumeral ligament is released from the base of the coracoid process, allowing unrestricted gliding of the supraspinatus as well as the subscapularis.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:519.)

Releasing the subscapularis. (A) The subscapularis is often tethered to the coracoid and glenoid via the capsule, limiting its excursion (arrow) . (B) The subscapularis is released circumferentially (red arrow) , freeing it from the coracoid, the anterior glenohumeral capsule, the axillary nerve, and the coracoid muscles, allowing increased excursion (black arrow) .

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:519.)

A 360-degree capsular release. (A) The glenoid here is concentrically worn and the shoulder is tight. (B) An extralabral release is therefore performed 360 degrees around the perimeter of the glenoid (red dashed line) .

Posterior capsular release. If the posterior capsule is tight, it can be released under direct vision by rotating the inferior aspect of the retractor away from the glenoid and gently internally rotating the humerus.

The 40-50-60 rule for appropriate soft tissue tensioning is as follows: at least 40 degrees external rotation with a reapproximated subscapularis tendon (left) , 50% posterior subluxation on the posterior drawer test (middle) , and 60 degrees of internal rotation of the 90-degree abducted arm (right) .

(A) The preoperative axillary view shows posterior subluxation of the humeral head and posterior glenoid wear. (B) The extralabral release (red dashed line) then includes only the anterior capsule. (C) If the posterior instability is substantial, the release (red dashed line) stops at the inferior glenohumeral ligament.

Anatomic repair of the subscapularis tendon should allow at least 40 degrees of external rotation.

Synovectomy.

The management of rheumatoid arthritis has been substantially improved through the use of disease-modifying agents (e.g., Plaquenil, cyclosporine, methotrexate, Cytoxan, Imuran, and Azulfidine) and biologics (e.g., Enbrel, Humira, Orencia, Remicade, and Rituxan). Before the availability of these medications, synovectomy and other nonprosthetic options were commonly used to remove inflammatory tissue from the glenohumeral joint. *

* References , , , , , .

Currently, synovectomy is used primarily to manage refractory synovitis and bursitis in the absence of major joint surface damage ( Fig. 60.166 ). ^,

The shoulder of a young man with rheumatoid arthritis and primary rheumatoid involvement of the subacromial-subdeltoid bursa. The rotator cuff was intact, and the glenohumeral joint had minimal involvement with rheumatoid synovitis. The patient had a full, minimally painful range of motion in the shoulder, with excellent shoulder strength. The hypertrophic bursitis did not respond to medical management, and the bursa was surgically excised.

Resection.

Before prostheses were available, resection of the humeral head was used to manage arthritis and severe fractures. ^, In general, comfort and function after resection arthroplasty are poor and so its current use is primarily for refractory infection or for failed arthroplasty without other means of reconstruction ( Figs. 60.167–60.169 ).

A shoulder with resection of the total shoulder humeral and glenoid components because of refractory infection. (A) Anteroposterior view. (B) Axillary view.

Resection for a failed arthroplasty.

A proximal humeral prosthetic replacement had previously been placed in an elderly woman with multiple-joint osteoarthritis. (A) Her total knee arthroplasty became infected, and the infection spread to the proximal humeral prosthetic replacement. The shoulder region was brawny and erythematous, with a draining sinus on the anterolateral aspect of the arm. The region was debrided and the prosthesis and cement removed. (B) Radiographic appearance of the joint after delayed primary closure. At follow-up, the patient had only mild pain, and the shoulder was stable because of fibrosis. She had active abduction of 65 degrees and external rotation of 10 degrees.

Considerations.

Glenohumeral arthrodesis is usually reserved for attempts at salvaging septic arthritis or complex deficiencies of the joint surface associated with permanent loss of the cuff and deltoid. ^{, ,} The best candidates for this procedure are shoulders that meet the following criteria: (1) permanent and severe weakness because of loss of cuff and deltoid function; (2) good scapular motors (e.g., trapezius, levator scapulae, pectoralis, serratus anterior, and rhomboids); and (3) sufficient residual glenoid and humeral bone stock to enable the fusion. Patients considering this procedure should have a strong motivation to succeed, minimal complaints of pain, and a good understanding of the following: (1) the potential complications of a shoulder fusion (including fracture of the humerus below the fusion); (2) the resultant limitation of internal and external rotation; and (3) the possible need for a second procedure to add bone graft to augment the fixation if the fusion does not “take” on the first attempt.

In the past, surgeons recommended fusing the shoulder in positions of abduction and flexion with the aim of optimizing function. ^{, ,} However, such positions can be associated with substantial discomfort, largely related to the need to “wing” the scapula when the humerus is adducted to the resting position. To establish the limitations of function after shoulder fusion, we studied 12 shoulders that had undergone glenohumeral arthrodesis at least 2 years before the time of study. ^, The mean humerothoracic elevation in the plus 90-degree (anterior sagittal) plane was 47 degrees, the mean elevation in the minus 90-degree (posterior sagittal) plane was 22 degrees, the mean humerothoracic external rotation was 9 degrees, and the mean internal rotation was 46 degrees. These ranges of motion were similar to the scapulothoracic motion measured in normal subjects. Only one patient could reach his hair without bending the neck forward, five could reach their perineum, six could reach their back pocket, seven could reach the opposite axilla, and ten could reach their side pocket. We conducted a second study of normal in vivo shoulder kinematics to predict the functions that would be allowed by various positions of glenohumeral arthrodesis. This indicated that activities of daily living could best be performed if the joint was fused in 15 degrees of flexion, 15 degrees of abduction, and 45 degrees of internal rotation. This low angle of elevation and relatively high degree of internal rotation facilitated sitting comfortably on a chair; lying flat in bed; and reaching the face, the opposite axilla, and the perineum. Thus my preferred position is the “15, 15, 45” combination described above, a position that minimizes protrusion of the shoulder blade posteriorly into the chair or bed when the arm is at the side. This position has the additional advantages of being easy to determine at surgery and needing only a sling for postoperative immobilization rather than a cast or brace. It is most important to avoid fusing the shoulder in neutral or external rotation because this position precludes reaching the mouth or perineum.

Many techniques have been described for shoulder arthrodesis. *

* References , , , , , , , .

Technique.

The patient is placed in the beach chair position with the scapula in the prepared field and the arm draped free. The operative approach is through an anterior deltopectoral incision, with superior extension of the incision if plate fixation is used. I have used a low anterior axillary incision when cosmesis is a concern and intra-articular fusion is planned.

Any residual articular cartilage on the humerus or glenoid is curetted down to raw subchondral bone, as removing the subchondral bone weakens the construct and makes solid glenohumeral compression more difficult to achieve ( Figs. 60.170 and 60.171 ). The supraspinatus tendon is resected from between the humeral head and the acromion, and the undersurface of the acromion is stripped down to raw bone ( Fig. 60.172 ). The soft tissues are lifted from the anterior glenoid neck so that the subscapularis fossa can be palpated ( Fig. 60.173 ).

Humeral head curettage. The articular cartilage is removed from the head of the humerus without sacrificing subchondral bone. Access to the joint surface is achieved by external rotation.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:236.)

Glenoid curettage. The articular cartilage of the glenoid is removed with a curette without compromising the subchondral bone.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:237.)

Acromion curettage. The periosteum of the acromial undersurface is curetted without compromising the cortical bone.

Identifying the subscapularis fossa. The anterior aspect of the glenoid neck is palpated. This area will be the target for the compression screws.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:239.)

The humeral head is centered in the glenoid with the arm in 15 degrees of abduction, 15 degrees of flexion, and 45 degrees of internal rotation ( Fig. 60.174 ). It is temporarily fixed with three long 3.2-mm drill bits; these should exit the neck of the scapula anteriorly approximately 2 cm medial to the glenoid lip, where their tips can be palpated and controlled ( Figs. 60.175 and 60.176 ). When used in this manner, the known length of the drill bits can serve as depth gauges to determine the length of screws needed. The position of the arm is checked by making sure that the hand can reach the mouth, the anterior perineum, and the contralateral axilla. The 3.2-mm drill bits are sequentially replaced by fully threaded 6.5-mm cancellous screws with washers ( Figs. 60.177 and 60.178 ). Because the humeral head is softer than the glenoid, compression can usually be achieved without formally lagging the screw or needing to use a smooth shank.

For many patients, the most comfortable position of fusion is that of 0 degrees of flexion, 0 degrees of abduction, and 60 degrees of internal rotation. This position allows the scapula to sit in its normal position on the chest wall while the arm is at the side.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:239.)

While the humeral head is held reduced in the glenoid fossa in its proper position, a drill bit is passed through a stab incision then through the deltoid, the proximal humerus, and the glenoid, before exiting anteriorly from the neck.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:240.)

Subsequent drill placement. Two additional drill bits are placed parallel to the first, equally spaced across the glenohumeral joint. The position and orientation of the humerus in relation to the glenoid is checked again.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:241.)

Screw placement. The drill bits are sequentially replaced with 6.0-mm fully threaded cancellous screws with washers.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:242.)

Screw length. Each screw should just penetrate the subscapularis fossa at the base of the glenoid neck.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:243.)

An iliac crest bone autograft is fashioned to fit between the humeral head and the acromion; it rests in the position normally occupied by the supraspinatus tendon ( Figs. 60.179–60.181 ). Interposition of the iliac crest graft maximizes humeroscapular contact by preserving the normal concave-convex glenohumeral relationships while allowing stabilizing contact between the head, the graft, and the acromion. If the humeral head is moved upward to make contact with the acromion without a graft, the glenohumeral contact area for fusion gets reduced. The graft is held in position by another screw placed from the acromion through the graft and out through the anteromedial aspect of the humeral neck ( Figs. 60.182 and 60.183 ). Additional bone graft is added around the fusion area to optimize healing.

Acromiohumeral (AH) distance. After the supraspinatus tendon has been resected, the distance between the humeral head and the acromion is measured.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:243.)

Graft harvest. A segment of graft measuring 20 × 20 × 8 mm is harvested from the iliac crest.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:244.)

Graft placement. The graft is placed between the humeral head and the acromion in the area normally occupied by the supraspinatus tendon. This graft increases the quality of the fixation while helping maintain the position of the humeral head in the glenoid concavity.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:245.)

Graft fixation. A fourth screw is passed through the acromion, the graft, and out the firm bone at the humeral neck.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:247.)

Cancellous grafting. Cancellous bone graft is added across the area of glenohumeral arthrodesis.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:247.)

Depending on the circumstances, a neutralization plate (usually an 8- to 12-hole dynamic compression plate or pelvic reconstruction plate) may be used ( Fig. 60.184 ). If so, several points need to be emphasized. The plate needs a bend of about 90 degrees at the acromion and often an internal rotation twist of about 45 degrees to fit on the anterior of the humerus. The strongest fixation for the plate on the scapula is obtained by a screw down the base of the spine of the scapula just medial to the spinoglenoid notch. The arm is protected in a sling until the fusion is clinically and radiographically healed. When the fusion is solid, function and comfort can be enhanced by strengthening the periscapular musculature.

Glenohumeral and acromiohumeral arthrodesis performed using a contoured iliac crest bone graft inserted between the acromion and the humeral head. The arthrodesis is stabilized securely with the following components: three washered, fully threaded cancellous humeroglenoid screws; one fully threaded cancellous screw through the acromion, graft, and humeral head; and a contoured reconstruction plate.

Complications of shoulder arthrodesis include nonunion, infection, malposition, prominence of the internal fixation plates, and fracture. Nonunion can be treated by freshening the arthrodesis site, repeat fixation, and bone grafting. It can sometimes be difficult to be sure from radiographs whether or not the fusion is solid; in such cases a reexploration may be helpful in evaluating the completeness of the fusion and the security of the internal fixation. Infection is treated by incision, drainage, and antibiotics, attempting to maintain the hardware stabilizing the fusion. Malposition is most common in excessive flexion, abduction, or external rotation. It is often preferable to manage malposition by humeral osteotomy ( Fig. 60.185 ), rather than by taking down a solid fusion and attempting to reposition it. Care must be taken in removing prominent hardware unless the fusion is absolutely solid. Humeral shaft fracture is a particular risk because the fused shoulder lacks the normal shoulder’s ability to absorb load without damage.

Subtuberous humeral osteotomy performed for a shoulder that was fused in excessive abduction, excessive flexion, and malrotation. (A) Internal fixation. (B) After internal fixation has been removed.

Considerations.

Under optimal circumstances, glenohumeral arthroplasty can be a powerful approach for reconstructing an arthritic shoulder. In considering the advisability of a shoulder arthroplasty and the selection of a specific procedure, it is important to consider the four P’s.

• 1.
  

  Is the problem (diagnosis and associated aspects of the shoulder) one that can be well managed with arthroplasty? Are the essential bone, deltoid, cuff, nerve, and skin tissues in sufficiently good condition for a safe and effective arthroplasty? Is the severity of the problem typical of patients presenting for shoulder arthroplasty? ( Fig. 60.186 )

  
  

  
  

  
  

  

  
  

  
  

  Frequency distribution of the number of Simple Shoulder Test functions that a sample of patients was able to perform immediately prior to shoulder arthroplasty. We use this chart to help the patient consider the question, “When is my arthritic shoulder bad enough to justify a joint replacement?” As shown by this graph, the great majority of these patients were able to perform less than half of the 12 functions.

  
  
  
  
• 2.
  

  Is the patient informed and in sufficiently good physical, social, and emotional health to succeed with the procedure and its postsurgical rehabilitation? Comorbidities, level of education, type of insurance, age, sex, and the patient’s overall well-being have all been shown to influence the outcome of the arthroplasty. ^{, , ,}

  
  
• 3.
  

  Is the physician sufficiently experienced in shoulder reconstruction to optimize the chance of a good outcome? Many shoulder arthroplasties are performed by surgeons who perform only a small number of these cases each year, yet case volume has a strong influence on the outcome of the surgery. As we say, “The surgeon is the method,” and “Experience is the great teacher.”

  
  
• 4.
  

  Is the procedure appropriate for the problem, patient, and physician? Among the variations of shoulder arthroplasty available, which is the best fit for the shoulder, the patient, and the surgeon?

Types of arthroplasty.

There are four basic types of shoulder arthroplasty: the humeral hemiarthroplasty, the ream and run arthroplasty (humeral hemiarthroplasty with a nonprosthetic glenoid arthroplasty), the anatomic total shoulder arthroplasty (humeral hemiarthroplasty with a prosthetic glenoid arthroplasty), and the reverse total shoulder arthroplasty.

Prosthetic humeral hemiarthroplasty is considered under the following circumstances: (1) when the glenoid articular surface is intact (as in avascular necrosis before collapse of the humeral head and before secondary destruction of the glenoid surface); (2) when there is insufficient joint volume or glenoid bone stock to allow for secure placement of a glenoid component; (3) in cases of rotator CTA when the humeral head is stabilized by an intact coracoacromial arch (see Fig. 60.112 ) and active elevation exceeds 90 degrees *

* References , , , , , .

Humeral head prosthesis fixed with a stem inserted down into the humeral medullary canal.

Complete resurfacing head prosthesis mounted on the retained biologic humeral head.

Ream and run arthroplasty (humeral hemiarthroplasty with a nonprosthetic glenoid arthroplasty) is considered for the treatment of glenohumeral arthritis when the patient, after being informed, wishes to avoid the potential risks and activity restrictions associated with a prosthetic glenoid component. Initially there was interest in biologic resurfacing of the glenoid with capsule or cadaveric meniscus ( Fig. 60.189 ) as a way to avoid the risks of prosthetic glenoid component failure; however, recent experience with this approach has not been encouraging. The ream and run procedure is a glenohumeral arthroplasty in which a humeral hemiarthroplasty is combined with conservative reaming of the glenoid to a single concentric concavity without substantially modifying glenoid version and without the use of biologic interposition. ^{, ,} Because the ream and run procedure modifies both the humeral and glenoid articular surfaces, it is a glenohumeral arthroplasty; this should not be confused with a hemiarthroplasty in which only the humeral side of the joint is addressed. It is referred to as a radically conservative procedure because it involves the removal of less glenoid bone than would be required for the insertion of a glenoid component.

Biologic glenoid resurfacing with a knee meniscal allograft.

In the anatomic total shoulder arthroplasty , a humeral hemiarthroplasty is combined with a prosthetic glenoid component. The total shoulder arthroplasty is the most commonly used approach to glenohumeral arthritis when the rotator cuff is intact and when sufficient glenoid bone is available for fixation of the glenoid prosthesis. ^{, ,}

In the reverse total shoulder arthroplasty , the positions of the ball and socket are reversed from the anatomic arrangement. This type of prosthesis is used when the arthritic shoulder demonstrates instability that cannot be managed with an anatomic prosthesis or when there is insufficiency of the rotator cuff. Reverse total shoulder arthroplasty is traditionally used to manage CTA and anterosuperior escape (see Figs. 60.111–60.113 and 60.117 ). Expanding indications for reverse arthroplasty include shoulders with an irreparable rotator cuff and pseudoparalysis, meaning that the shoulder cannot be actively elevated to 90 degrees despite a good range of passive motion and intact deltoid function. Reverse arthroplasty is also used to manage comminuted proximal humeral fractures in the osteopenic bone of older individuals and failed anatomic arthroplasty with instability or pseudoparalysis ( Fig. 60.190 ). ^{, ,}

Failed anatomic prosthesis for a fracture with pseudoparalysis. (A) Anteroposterior view showing superior placement of the humeral prosthesis, superior subluxation of the humeral head, and an absent greater tuberosity. (B) Because of the high position of the stem, the humeral prosthesis had to be removed at the time of conversion to a reverse total shoulder arthroplasty.

Mechanics of anatomic arthroplasty.

Four basic mechanical characteristics are essential to shoulder function: mobility, stability, strength, and smoothness. Commonly, each of these characteristics is compromised in an arthritic shoulder, and each can potentially be improved by shoulder arthroplasty. The approach to glenohumeral arthritis is guided by an understanding of these elements necessary for optimal shoulder mechanics. Although recreation of appropriate bone alignment may help with soft tissue balance and restoration of appropriate shoulder mechanics, restoration of glenohumeral mobility and stability is the priority rather than trying to recreate “normal anatomy.” Templating systems or patient-specific instrumentation systems based on a preconceived “normal” shoulder are not able to fully address the issues associated with shoulder arthritis. In performing glenohumeral reconstruction it is often necessary to modify the humeral head size, thickness, and eccentricity to achieve the desired joint mechanics while preserving glenoid and humeral bone stock. An understanding of glenohumeral mechanics and how to use soft tissue balancing techniques to restore glenohumeral mechanics during shoulder arthroplasty are essential to successful outcome. ^{, , ,}

Mobility.

The requisites for a normal range of glenohumeral motion include normal capsular laxity, appropriately sized and shaped concentric articular surfaces, and the absence of osteophytes or other unwanted sources of contact between the proximal humerus and the lateral scapula.

Capsular laxity.

In normal shoulders ample capsular laxity allows the full range of rotation at the glenohumeral joint. The glenohumeral capsule normally remains lax through most of the functional range of motion. ^, As the joint approaches the limit of its range, the tension in the capsule and its ligaments increases sharply, checking the range of motion ( Fig. 60.191 ). However, in most conditions that require shoulder arthroplasty, the capsule and ligaments are contracted; this prematurely limits the range of motion and increases the joint pressure at the limits of motion ( Fig. 60.192 ). The term “stuffing” has been used to refer to additional tightening of the capsule that results from the insertion of prosthetic components that take up more space than that afforded by the available joint volume ( Fig. 60.193 ). Unless capsular releases ( Figs. 60.194 and 60.195 ) sufficient to accommodate this additional volume have been performed, the joint becomes “overstuffed,” limiting joint motion ( Fig. 60.196 ), with greater torque (muscle force) required to move the arm ( Fig. 60.197 ). Cadaver studies have indicated that less than 10 mm of overstuffing can reduce normal capsular laxity by as much as 50% ( Fig. 60.198 ). Overstuffing also causes obligate translation of the humeral head on the glenoid, resulting in eccentric glenoid loading ( Table 60.4 ); for example, the compressive load increases and forced posterior translation occurs when external rotation is attempted against a tight anterior capsule, accounting for the pathology commonly seen in capsulorrhaphy arthropathy (see Fig. 60.90 ; Figs. 60.199 and 60.200 ).

Range of humeroscapular elevation with no capsular tension. This global diagram represents data from a cadaver experiment in which the humerus was elevated in a variety of scapular planes and free axial rotation was allowed. Elevation was performed until the torque reached 500, 1000, and 1500 N/mm. The positions associated with these torques are indicated by the isobars (gray, red, and blue dashed lines) . The area within the 500 N/mm isobar indicates the range of positions in which there was effectively no tension in the capsuloligamentous structures. For further details, see .

(A) Normal capsular laxity allows an unrestricted range of motion. (B) In degenerative joint disease the capsule may be contracted and has to course over osteophytes. (C) As the joint approaches the premature limit of its range, the tension in the capsule and ligaments increases sharply, increasing the joint pressure (red arrows) .

Shoulder arthroplasty can tighten the capsule. (A) A degenerated and collapsed humeral head. (B) The head has been replaced by a relatively larger prosthesis with a glenoid component added to the surface of the glenoid bone. The prosthetic components take up a greater volume than the degenerated surfaces they replace and consequently stuff the joint.

Release of the anterior capsule from the glenoid while the axillary nerve is protected. (A) Anteroposterior view showing incision of the inferior capsule while the axillary nerve (yellow) is retracted. (B) Lateral view showing release of the capsule from the anterior and inferior glenoid.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:520.)

Posterior capsule release. If the posterior capsule is tight, it can be released under direct vision. The surgeon places the capsule under tension by rotating the inferior aspect of the retractor away from the glenoid (arrow) and gently internally rotating the humerus.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: WB Saunders; 2004:555.)

Effect of joint stuffing on the range of motion. This graph compares four humeroscapular ranges of motion that could be achieved with an applied torque of 1500 N/mm for an anatomic joint (0 mm of joint stuffing), an anatomic humeral arthroplasty with a 4-mm-thick glenoid component (4 mm of overstuffing), and an arthroplasty with a 4-mm-thick glenoid and a 5-mm oversized humeral neck (a total of 9 mm of overstuffing). Note the sequential loss of range of motion as the degree of stuffing increases.

(From Matsen FA III, Lippitt SB, Sidles JA, et al. Practical Evaluation and Management of the Shoulder. Philadelphia: WB Saunders; 1994.)

The average torque necessary to achieve 60 degrees of elevation in the +90-degree scapular plane for an anatomic shoulder (0 mm of stuffing), an anatomic shoulder arthroplasty with 4 mm of glenoid stuffing, and an arthroplasty with 4 mm of glenoid and 5 mm of humeral overstuffing (a total of 9 mm of overstuffing). The required torque is almost three times higher for the joint overstuffed with 9 mm of component than for the anatomic joint.

(From Matsen FA III, Lippitt SB, Sidles JA, et al. Practical Evaluation and Management of the Shoulder. Philadelphia: WB Saunders; 1994.)

The effect of overstuffing on capsular laxity in eight cadaver shoulders (mean age, 73 ± 8.5 years). The intact shoulders (0 mm of stuffing) demonstrated 15 mm of translational laxity on the anterior drawer, posterior drawer, and sulcus tests. Overstuffing by 9 mm reduced this normal joint laxity by approximately 50% in all directions.

(From Matsen FA III, Lippitt SB, Sidles JA, et al. Practical Evaluation and Management of the Shoulder. Philadelphia: WB Saunders; 1994.)

Ligament shortening (red dotted lines) can cause increased joint pressure (short arrows) . If the capsule and ligaments on one side of the joint are shortened, applying torque against them (red arrow) can increase the compressive force (c) applied to the joint surface. This increased joint pressure can damage the joint surface. d , Displacing force; t , total force.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:40.)

If the humerus is rotated beyond the point at which the ligaments become tight, the displacing force (P) can push the humeral head out of the glenoid center, a phenomenon known as “obligate translation.”

(Modified from Matsen FA III, Lippitt SB, Sidles JA, et al. Practical Evaluation and Management of the Shoulder. Philadelphia: WB Saunders; 1994.)

In total shoulder arthroplasty, the contribution of the components to joint stuffing can be estimated by adding the thickness of the glenoid component to the net added thickness of the humeral component (i.e., the difference between the amount of intra-articular humerus resected and the amount of humerus added) (see Fig. 60.193 ; Figs. 60.201–60.203 ). The amount of stuffing from the humeral component is also influenced by the position in which it is placed: a humeral stem inserted in varus will increase the stuffing of the joint when the arm is at the side ( Fig. 60.204 ). A component inserted in an excessively high position tightens the capsule in adduction ( Fig. 60.205 ) and in abduction ( Fig. 60.206 ). The incremental thickness of the glenoid is determined by the thickness of the component, as well as by the amount of reaming, the presence or absence of cement between the component and the bone, and the effect of bone grafts ( Fig. 60.207 ). The thickness of currently available glenoid components varies from 3 mm to more than 15 mm.

Consequences of the amount of joint stuffing. (A) When the head component is too small, the cuff is slack at rest. (B) With a properly sized head component, there is appropriate tensioning of the rotator cuff. (C) Overstuffing the joint with a head component that is too large places excessive tension on the rotator cuff.

Neck length. (A) Normal relationships. (B) A prosthesis with a collar and gap increases the total neck length.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:458.)

Overstuffing. Excessive height of the humeral articular surface, from either a thick glenoid (A) or a large head (B), overstuffs the joint and places the rotator cuff under greater tension when the arm is in adduction.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:702.)

Varus position of the humeral component can increase the distance between the greater tuberosity and the glenoid (W) , effectively overstuffing the joint.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:703.)

Head height and adduction. (A) The ideal position. (B) Positioning the humeral prosthesis in an excessively superior position causes excessive tension in the superior cuff when the arm is in adduction (dotted lines) .

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:454.)

Head height and abduction. (A) The ideal position. (B) Positioning the humeral prosthesis in an excessively superior position causes excessive tension in the inferior capsule when the arm is in abduction.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:455.)

Glenoid thickness contributes to the relative stuffing of the joint. This is particularly an issue with some metal-backed components, where a minimum thickness of 3 to 4 mm of polyethylene is superimposed on a metal base. As a result, some components are up to 1.25 cm thick. Insertion of such a component can be predicted to reduce the range of rotation in each direction by about 28 degrees (12.5 mm of increased thickness is half a radian for an average humeral head of radius 25 mm; in degrees, half a radian is 0.5 × 360/2π, or 28 degrees). Thus the restoration of motion to an arthritic shoulder can require a combination of soft tissue releases and avoiding the insertion of a thick glenoid component.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:504.)

Overstuffing can be avoided by ensuring adequate capsular laxity at the time of surgery using the “40, 50, 60” rule of thumb to guide the selection of the prosthetic sizes: the arm should allow 40 degrees of external rotation at the side after the anterior structures have been approximated ( Fig. 60.208 ), the humeral head should translate approximately 50% of the width of the glenoid in the posterior drawer test ( Fig. 60.209 ), and the abducted arm should allow 60 degrees of internal rotation ( Fig. 60.210 ).

The 40-50-60 rule for adequate capsular laxity to guide the selection of a prosthetic replacement. The arm should allow 40 degrees of external rotation at the side after the anterior structures have been approximated.

The 40-50-60 rule for adequate capsular laxity to guide the selection of a prosthetic replacement. The humeral head component should translate approximately 50% of the glenoid width on the posterior drawer test.

The 40-50-60 rule: internal rotation. There should be 60 degrees of internal rotation of the arm abducted to 90 degrees.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:480.)

If the humeral head translates posteriorly by more than 50%, three strategies may be considered individually or in combination: (1) selecting a humeral head component of greater diameter or thickness ( Fig. 60.211 ); (2) using an anteriorly eccentric head component ( Fig. 60.212 ); or (3) performing a rotator interval plication ( Fig. 60.213 ).

(A) The humeral head translates further than 50% posteriorly. (B) A larger width head component may improve the balance of the reconstruction.

(A) The humeral head translates further than 50% posteriorly. (B) An eccentric head component oriented anteriorly may improve the balance of the reconstruction.

Rotator interval closure, anterior view. The rotator interval is closed using four braided No. 2 nonabsorbable sutures inserted with the knots buried.

Humeral articular surface.

A substantial, properly located humeral articular surface area allows a large unimpeded range of motion ( Fig. 60.214 ). Humeral articular surfaces that are nonspherical ( Figs. 60.215 and 60.216 ) or that comprise a reduced portion of the sphere ( Figs. 60.217–60.220 ) reduce the amount of range of motion that can take place with full surface contact at the glenohumeral joint ( Fig. 60.221 ). ^{, , ,}

Normal spherical cap. Restoration of the entire area of the spherical cap maximizes the range of motion with full surface contact between the humeral head and glenoid.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:430.)

Nonspherical humeral head prosthesis.

“Rocking horse” glenoid loosening with a nonspherical humeral head.

Spherical cap reduced by collar and gap between the head and collar of the prosthesis. A prosthesis with a collar and a gap sacrifices the height of the spherical cap and the range of motion with full surface contact.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:432.)

Spherical cap reduced by chamfering. A chamfered humeral head prosthesis has a reduced height of the spherical cap and reduced range of motion with full surface contact.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:431.)

A humeral component with an articular surface that encompasses only a small portion of the potential spherical articular surface can predispose the prosthesis to unwanted translation as well as unwanted contact between the prosthetic collar and the glenoid.

A large collar and a small articular surface provide minimal humeral articular surface area. In addition, this prosthesis was placed too high.

Motion-limiting abutment between the glenoid component and soft tissue or bone when the arm is externally rotated (arrow) .

(Modified from Ballmer FT, Lippitt SB, Romeo AA, et al. Total shoulder arthroplasty: some considerations related to glenoid surface contact. J Shoulder Elbow Surg. 1994;3:299–306.)

Glenoid articular surface.

The glenoid surface encompasses a relatively small portion of the articulating sphere when compared with the articular surface of the humerus. If the prosthetic joint surface area of the glenoid is large compared with that of the humerus, abutment of the prosthesis against the humeral neck or tuberosities can restrict joint motion ( Fig. 60.222 ).

If the prosthetic glenoid joint surface area is large compared with that of the humerus, abutment of the prosthesis against the humeral neck or tuberosities can restrict joint motion.

Concentricity of the coracoacromial and glenohumeral spheres.

Two spheres are involved in glenohumeral motion: one represented by the articular surfaces of the humeral head and the glenoid, and the other by the proximal humeral convexity and the coracoacromial arch ( Figs. 60.223 and 60.224 ). The difference in the radius of these two spheres is made up by the height of the tuberosities and the thickness of the rotator cuff. For optimal shoulder kinematics, the centers of these spheres need to match.

Concentric spheres. The center of the coracoacromial concavity is the center of the sphere that best fits the concave undersurface of the coracoacromial arch. r is the radius of the humeral articular surface and the glenoid articular surface with which it articulates; R is the radius of the proximal humeral convexity (the outer surface of the cuff and tuberosity) and the undersurface of the coracoacromial arch with which it articulates.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:413.)

Proximal humeral convexity. The center of the proximal humeral convexity is the center of the sphere that circumscribes the cuff tendons and the tuberosity. The radius of the proximal humeral convexity (R) differs from the radius of the humeral head (r) by the thickness of the rotator cuff.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:415.)

Absence of unwanted bone contact.

Osteophytes predispose to unwanted contact between the humerus and the glenoid and can impair motion ( Figs. 60.225–60.227 ). Any blocking osteophytes must be completely resected at the time of joint reconstruction ( Figs. 60.228 and 60.229 ). A malunited greater tuberosity can also limit rotation ( Fig. 60.230 ).

When the arm is adducted (black arrow) , humeral inferior osteophytes can abut the inferior glenoid (red arrow) , causing the glenohumeral joint to “open book” superiorly (red lines) .

Blocking osteophytes. Humeral osteophytes can abut against the glenoid lip (red arrow) , limiting the range of rotation.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:47.)

(A) Care should be taken to ensure that the posterior humeral head does not abut the posterior glenoid in external rotation (red arrow) . (B) This can cause the joint to “open book” anteriorly.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:585.)

Posterior “open book.” (A) If the posterior nonarticular humerus abuts against the posterior corner of the glenoid, the joint will “open book” on external rotation (B).

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:579.)

Inferior “open book.” (A) Bone extending beyond the curvature of the prosthetic humeral articular surface (arrow) . (B) This can abut the inferior glenoid when the arm is adducted (arrow) .

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:701.)

Malunion of the greater tuberosity. Malunion with posterior displacement of the greater tuberosity allows the tuberosity to abut the glenoid on external rotation.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:701.)

Normally, 4 to 5 cm of excursion takes place at the upper aspect of the interface between the coracoid muscles and the subscapularis ( Figs. 60.231 and 60.232 ). Bursal hypertrophy, adhesions, or spot welds between the proximal aspect of the humerus and the cuff on the one hand and the deltoid and coracoacromial arch on the other can limit motion, even when the intra-articular aspect of the arthroplasty is perfectly balanced ( Fig. 60.233 ). Lysis of humeroscapular spot welds is an important early step in arthroplasty of the shoulder.

Humeroscapular motion interface (dotted line) . The external surface of the rotator cuff articulates with the undersurface of the coracoacromial arch. This articulation is part of the humeroscapular motion interface. Smooth, unrestrained movement at this interface is required for normal shoulder function.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:412.)

Humeroscapular motion interface. The humeroscapular motion interface is the set of gliding surfaces (arrows) between the proximal humerus covered by the rotator cuff tendons and the overlying structures attached to the scapula, including the deltoid, acromion, coracoacromial ligament, coracoid, and the tendons of the coracoid muscles. Approximately 4 cm of motion takes place at this interface in normal shoulder movement.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:413.)

Spot welds. Adhesions from the external to the internal surface of the humeroscapular motion interface can restrict the range and smoothness of motion.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:45.)

Stability.

The primary mechanism for glenohumeral stability is “concavity compression,” described earlier (see Fig. 60.4 ). ^, Concavity compression is optimized by an ample humeral articular surface area, a stabilizing glenoid concavity, and muscular control of the net humeral joint reaction force such that it compresses the humeral articular surface into the glenoid concavity ( Fig. 60.234 ). This mechanism is commonly altered in osteoarthritis, with some degree of posterior humeral head subluxation present in most cases. ^,

Balanced net forces. The direction of the forces exerted by the scapulohumeral muscles (dashed arrows) is determined by their effective attachments to the scapula and humerus.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:488.)

Humeral articular surface area.

The function of the humeral articular surface is to apply the net humeral joint reaction force evenly across the glenoid throughout the normal range of glenohumeral motion. A prosthetic surface area that represents only a small part of the total sphere can predispose to instability in the same way that a Hill-Sachs defect does in traumatic instability by offering less contact area for joint surface contact (see Figs. 60.215 to 60.220 ; Fig. 60.235 ).

Surface contact. (A) Full surface contact provides broadly distributed load transfer and maximal joint stability. (B and C) Without full surface contact, the humeral component can be translated in the direction of the empty part of the glenoid.

(From Matsen FA III, Lippitt SB. Shoulder Surgery: Principles and Procedures. Philadelphia: Saunders; 2004:433.)

The orientation of the humeral articular surface can be described in terms of the humeral head centerline, a line that passes through the center of the humeral joint surface and the center of the anatomic neck ( Fig. 60.236 ). This line usually makes a valgus angle of about 130 degrees with the humeral shaft, and it generally makes a retroversion angle of about 30 degrees with the plane of the humerus ( Figs. 60.237 and 60.238 ). In contrast to the situation with the femoral component in hip arthroplasty where rotational alignment is critical ( Fig. 60.239 ), changing the version of the humeral component has relatively little effect on the effective position of the articulating surface of the humerus. This is because in most situations the center of rotation of the spherical humeral articular surface is close to the center of rotation of the stem of the prosthesis in the diaphysis ( Fig. 60.240 ). Thus alteration of humeral version is relatively ineffective in managing glenohumeral instability.

Humeral articular surface. The humeral articular surface can be considered as a spherical cap described by its radius of curvature (r) , base (b) , and height along the humeral articular centerline, and surface area.

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