The earliest known report of shoulder arthroplasty dates back to 1893, when a French surgeon, Péan, substituted a platinum and rubber implant for a glenohumeral joint destroyed by tuberculosis (Fig. 12-1). In the early 1950s, Neer introduced a humeral head prosthesis that he planned to use for complex shoulder fractures. In 1951, he reported his initial results of replacement of the humeral head with an unconstrained cobalt-chromium alloy (Vitallium) prosthesis. In 1974, the Neer II humeral prosthesis, which was modified to conform to a glenoid component, was introduced. Total shoulder arthroplasty using a constrained articulated unit in patients with loss of the rotator cuff but with a functional deltoid muscle was popular in the early 1970s but had limited success and has been abandoned.

FIGURE 12-1 Family tree of shoulder arthroplasty prostheses.

(Adapted from Gross RM: The history of total shoulder arthroplasty. In Crosby LA, editor: Total shoulder arthroplasty, Rosemont, IL, 2000, American Academy of Orthopaedic Surgeons.)

Glenoid components were initially designed for cementless fixation using screws and porous coating on metal backing with a polyethylene shell. But long-term studies have shown an unacceptably high complication rate, and as such these implants have been largely abandoned. In the 1990s, more emphasis was placed on restoring normal kinematics with anatomical location and orientation of the glenoid joint surface, advanced soft tissue balancing techniques, and physiological stabilization of the joint. More recently, research has focused on methods to reduce glenoid wear and loosening, which remains a common mode of late-term failure.

Anatomy and Biomechanics

The anatomy of the shoulder joint permits more mobility than any other joint in the body. Although it often is described as a ball-and-socket joint, the large humeral head articulates against and not within the small glenoid cavity. The glenohumeral joint depends on the static and dynamic stabilizers for movement and stability, especially the rotator cuff, which not only stabilizes the glenohumeral joint while allowing great freedom of motion but also fixes the fulcrum of the upper extremity against which the deltoid can contract and elevate the humerus. The rotator cuff must act simultaneously and synergistically, however, with the deltoid muscle for normal function.

Restoration of glenohumeral anatomy is essential for a good functional outcome. Anatomical studies have defined the humeral geometry further and suggested applications to shoulder arthroplasty prosthesis design and surgical techniques (Fig. 12-2 and Table 12-1). The articular surface of the humeral head is essentially spherical, with an arc of approximately 160 degrees covered by articular cartilage. The radius of curvature is approximately 25 mm and is slightly larger in men than in women. The glenoid articular surface radius of curvature is 2 to 3 mm larger than that of the humeral head. The average neck-shaft angle is 45 degrees (±5 degrees), with a range of 30 to 50 degrees. Murthi et al. found that arthritic shoulders have a flatter neck-shaft angle close to 50 degrees. CT studies found that the normal position of the glenoid surface in relation to the axis of the scapular body ranged from 2 degrees of anteversion to 7 degrees of retroversion.

FIGURE 12-2 Normal glenohumeral relationships. Humeral offset is depicted by distance F to H, thickness of humeral head from B to C, and center of humeral head at C. Note superior position of humeral head proximal to greater tuberosity (D to E).

TABLE 12-1 Anatomical Characteristics of the Shoulder Important for Prosthesis Design

Glenoid diameter
Superior anteroposterior	18-30 mm
Inferior anteroposterior	21-35 mm
Superoinferior (height)	30-48 mm
Inclination
Glenoid	Average 4.2 degrees (−7 to 20 degrees)
Humeral head	30-55 degrees
Version
Glenoid	1.5 degrees retroversion (10.5 to 9.5 degrees anteversion)
Humeral head	0-55 degrees retroversion (dependent on measurement method; highly variable among individuals)
Surface area
Glenoid	4-6 mm
Humeral head	11-19 mm
Cartilage thickness
Glenoid	2.16 mm
Humeral head	1.44 mm
Radius of curvature
Glenoid	22-28 mm
Humeral head	23-28 mm (smaller in women than men)
Humeral offset
Medial (coronal)	4-14 mm
Posterior (transverse)	−2 to 10 mm
Head-shaft angle	30-55 degrees

The superior margin of the humeral head articular surface normally is superior to the top of the greater tuberosity by 8 to 10 mm (see Fig. 12-2). Restoring the center of rotation for the humeral head in relation to the axis of the humeral diaphysis may play a role in prolonging glenoid fixation and decreasing polyethylene wear. The distance from the lateral base of the coracoid process to the lateral margin of the greater tuberosity is called the lateral humeral offset. Maintaining this distance is important because a significant decrease reduces the lever arms for the deltoid and supraspinatus muscles, which weakens abduction and impairs function. A significant increase causes excessive tension on the soft tissues (“overstuffing” of the joint), which also results in loss of motion. A biomechanical cadaver study determined that humeral articular malposition of more than 4 mm led to increased subacromial contact and that offset of 8 mm in any direction significantly decreased passive range of motion. The authors suggested that anatomical reconstruction of the humeral head/humeral shaft offset should be within 4 mm of normal to minimize subacromial contact and maximize glenohumeral motion.

Based on the clinical success of the Neer II implant, numerous modular designs were developed to improve implant fixation and durability. Detailed studies of shoulder anatomy in the 1990s found not only that normal shoulder anatomy aligned differently than the commonly used prostheses, but also that normal anatomy varied greatly among individuals. Modularity allows a better fit for individual patients because various stem and head sizes can be “mixed and matched” to an individual’s anatomy. Biomechanical studies also showed that shoulder biomechanics are adversely affected by the use of a prosthetic head that is too thick, too thin, or shifted too far from its original position along the plane of the anatomical humeral neck. As a general guideline, the prosthetic head should be within 4 mm of the original humeral head thickness.

Other characteristics of shoulder anatomy that are important in prosthesis design are retroversion, head-shaft angle, offset, radius of curvature, and humeral head height. Proximal humeral retroversion is highly variable, ranging from 0 to 55 degrees, depending on the method used for measurement. The proximal and the distal axes used to define retroversion have various definitions. For the proximal reference axis, the plane of the articular surface, a line connecting the center of rotation and the central point of the articular surface, and a line from the greater tuberosity to the central point of the articular surface have been used. For the distal reference axis, the trochlear axis, a line between epicondyles, and the forearm itself have been used. The inclination of the proximal humeral articular surface relative to the humeral shaft is the head-shaft angle; it ranges from 30 to 55 degrees, depending on the method of measurement. The humeral offset defines the position of the proximal humeral articular surface relative to the humeral shaft; it is measured as the distance from the center of rotation of the proximal humeral articular surface to the central axis of the humeral canal. The medial offset (coronal plane) ranges from 4 to 14 mm, and the anteroposterior offset (transverse plane) ranges from −2 to 10 mm. Reported values for the radius of curvature of the proximal humeral articular surface range from 20 to 30 mm; smaller radii typically are reported in women, and some authors have reported that the radius of curvature is larger in the coronal plane than in the sagittal plane.

Replacement of the anatomical humeral head size and position aims to restore normal shoulder biomechanics. Increasing the humeral head thickness by 5 mm has been shown to reduce the range of motion at the glenohumeral joint by 20 to 30 degrees, whereas decreasing the thickness by 5 mm can diminish motion by a similar amount by reducing the surface arc available for differential motion between the humeral head and the glenoid.

Prosthesis Design

Most current systems are modular with varying humeral head diameters and neck lengths to allow more accurate coverage of the cut surface of the humeral neck and improve the ability to establish correct position of the joint line. Some designs allow independent sizing of head thickness and head diameter to make soft tissue balancing easier. Most stems are made of cobalt-chrome alloy, have proximal porous ingrowth coating, and have proximal fins for rotational stability.

In an effort to match the proximal humeral anatomy as closely as possible, several implant systems offer concentric and offset humeral heads. In an anatomical dissection study, Boileau and Walch found that the center of the humeral head was 2.6 mm posterior and 6.9 mm medial to the center of the humeral shaft, and Robertson et al., using CT, noted similar measurements of 2.2 mm and 7.4 mm.

Anatomical positioning of the humeral head prosthesis is best done with an eccentric locking position of the Morse taper, which allows adjustments to the variable medial offset and any posterior offset. Curiously, postoperative kinematics after total shoulder arthroplasty do not mimic those of the native shoulder. Massimini et al. found that the posterosuperior quadrant of the glenoid is the primary contact location and that the replaced shoulder is not subject to traditional kinematic conceptions. Nevertheless, positioning the head too far superiorly puts additional tension on the overlying supraspinatus tendon and can cause impingement between the head and the acromion. Positioning the head too far inferiorly may cause abutment of the greater tuberosity on the acromion or internal impingement on the rim of the glenoid. Positioning the head too far anterior or posterior can result in abutment of the uncovered humeral neck on the corresponding glenoid rim and excessive tension on the overlying subscapularis and posterior rotator cuff tendons. Most current systems offer humeral heads that are offset by 3 or 4 mm; some allow several discrete positions, and some allow free rotation around the taper.

Most stems can be inserted with a press-fit or cemented technique. In a cadaver study, micromotion was found to be significantly less with proximal cement than with press-fit; no difference was found between proximal cementation and full cementation, and full cementation did not increase rotational stability over proximal cementation. Sanchez-Sotelo et al. reported that of 72 uncemented Neer II prostheses, 40 (55.6%) were at risk for loosening at an average 4-year follow-up, and only 1 (2%) of 43 cemented prostheses was at risk at more than 6 years’ follow-up. Clinically significant loosening of the humeral component is uncommon regardless of fixation methods.

Cemented all-polyethylene components remain the most frequently used glenoid components, but most now have an increased radius of curvature compared with the humeral head (2 to 6 mm larger) to allow translation during movement and to decrease edge loading. Several studies have shown that translation accompanies glenohumeral rotation after total shoulder arthroplasty. Such translation in a perfectly congruent joint may have a potential for localized wear and loosening (rocking-horse effect); however, increased loosening and polyethylene have not been reported to occur when the radii of curvature of the glenoid component and the humeral head are matched within 2 mm. In a multicenter study of 319 total shoulder arthroplasties using the same type of prosthesis, Walch et al. noted fewer radiolucencies with mismatches between the glenoid and humeral head diameters of more than 5.5 mm (6 to 10 mm). They cautioned that the upper limit of mismatch has not been conclusively determined, and thus greater prosthetic mismatches could lead to increased joint translation, accelerated polyethylene wear, and fracture. Current opinion seems to suggest that a glenoid with a radius curvature of 2 to 4 mm larger than the humeral head allows normal translation during rotation without rim loading or risk of loosening (Fig. 12-3).

FIGURE 12-3 A, When radii of curvature of glenoid component and humeral head conform, translation results in glenoid component rim loading. B, Slight increase in diameter of curvature of glenoid component over that of humeral head allows some translation before rim loading occurs.

A larger glenoid component results in increased force per unit area, however, which would seem to increase the risk of accelerated polyethylene wear, but this risk has not been substantiated clinically. However, larger components have been linked with improved stability. In a biomechanical study, Tammachote et al. demonstrated improved stability with increasing sizes of glenoid components. Specifically, transverse plane stability improved 17% between the small and medium components and then improved 10% between the medium and large components.

Currently, all-polyethylene glenoid components are most commonly used and generally are cemented into place. A biomechanical study found that cemented all-polyethylene designs had an overall stress pattern closer to that of an intact glenoid than did uncemented metal-backed components. In a report of 408 shoulder arthroplasties using a standard glenoid component and followed for more than 2 years, Neer reported that only 3 (0.07%) required reoperation because of glenoid loosening. More recently, Hopkins et al. found that bone quality was important in achieving solid glenoid component fixation. They also stressed the importance of proper implant positioning.

Polyethylene glenoid components generally have a single central or offset keel or multiple pegs for fixation into the glenoid vault. Biomechanical studies have not clearly shown a superiority for either, but the preponderance of evidence suggests an advantage to pegged designs. Lacroix, Murphy, and Prendergast, using a three-dimensional model and finite element analysis, found that bone stresses were not much affected by prosthesis design except at the tip of the central peg or keel. They did conclude, however, that pegged prostheses were better for normal bone, whereas keeled components were better for bone in rheumatoid patients. Murphy et al. suggested that an offset keel (UCLA design), anterior to the central plane of the component, decreases tensile and compressive stresses on the cement mantle and can help compensate for the effects of a deficient rotator cuff.

Clinical Presentation and Radiographic Evaluation

The clinical appearance of advanced glenohumeral degeneration was initially described by Neer. Patients typically present with global pain about the shoulder with difficulty performing overhead activities and, often, activities of daily living. On physical examination, diminished active and passive range of motion may be observed and patients may have previously been diagnosed with adhesive capsulitis. In patients with intact rotator cuff tendons, strength is often preserved but may be diminished secondary to pain. Palpable crepitus can often be elicited with passive internal and external rotation of the glenohumeral joint. The acromioclavicular joint and biceps tendon should be carefully evaluated because symptomatic acromioclavicular degeneration and/or biceps tendinitis may also be present.

Standard radiographs include anteroposterior views with a 40-degree posterior oblique view in neutral position and internal and external rotation as well as an axillary lateral view. Radiographs of the opposite, uninvolved shoulder and humerus are helpful in unusual situations, such as when a custom implant is indicated for large humeral or glenoid deficiencies.

The radiographic appearance varies with the patient’s pathological process. Those with osteoarthritis reliably demonstrate subchondral sclerosis and a large osteophyte on the inferior aspect of the humeral head (Fig. 12-4). This so-called “goat’s beard” is pathognomonic of advanced glenohumeral degeneration. These osteophytes can enlarge the humeral head to twice its normal size, resulting in capsular distention. Posterior instability caused by this capsular distention and posterior glenoid erosion may require capsular reefing or bone grafting at the time of shoulder arthroplasty. This is most common in cases of capsulorrhaphy arthropathy. Joint space narrowing, which is so reliably seen in hip and knee osteoarthritis, is not commonly seen in the shoulder until very late in the disease process owing to the non–weight-bearing position of the shoulder under standard radiography. Axillary lateral radiographs typically demonstrate posterior subluxation of the humeral head on the glenoid, and a wear pattern in the posterior glenoid may be present (Fig. 12-5). This same pattern is most often seen in advanced cases of posttraumatic arthritis and osteonecrosis. Patients with capsulorrhaphy arthropathy have a similar radiographic appearance except that loose bodies and osteophytes tend to be more common and numerous (Fig. 12-6) than in standard osteoarthritis.

FIGURE 12-4 Radiograph showing subchondral sclerosis and large osteophyte on inferior aspect of humeral head (goat’s beard) are pathognomonic of advanced glenohumeral degeneration.

FIGURE 12-5 Axillary radiograph and CT scan showing severe degenerative arthritis.

FIGURE 12-6 Radiograph showing capsulorrhaphy arthropathy; note numerous loose bodies and osteophytes.

Malunions of proximal humeral fractures can make shoulder arthroplasty more difficult, occasionally requiring osteotomy. A varus malunion between the head and shaft can complicate positioning of components, but osteotomy usually is unnecessary as newer “mini” and “micro” stem designs allow accommodation of these deformities. With malunions of the greater or lesser tuberosity, an osteotomy may be needed to reposition the tuberosity if it is severely malpositioned.

Patients with inflammatory arthritis often do not have an inferior osteophyte on radiographs and, instead, demonstrate a more symmetrical pattern of joint space narrowing with periarticular osteopenia. The wear pattern is more commonly central in the glenoid, and posterior subluxation of the humeral head is less common. Cystic change is also common. Rotator cuff tears are more common in patients with rheumatoid arthritis than in patients with osteoarthritis: full-thickness rotator cuff tears have been identified in 25% to 50% of patients undergoing shoulder arthroplasty. Most of these tears are superior.

MRI may be a useful adjunct in this population. In patients with strength deficits that could be due to either arthritic pain or a torn rotator cuff, MRI can help determine the status of the tendons. Whereas rotator cuff tendinopathy is common in this setting, full-thickness tears are uncommon and are seen in only about 10% of patients. MRI also typically demonstrates advanced cartilage degeneration and may show numerous other findings, including thinning of the subscapularis and degenerative changes in the biceps tendon. Increased capsular volume posteriorly and capsular contraction anteriorly are usual changes as well. Finally, in patients with pre-collapse osteonecrosis, MRI is useful to visualize the area of dead bone and is often the best tool to make the diagnosis (Fig. 12-7).

FIGURE 12-7 MR image showing pre-collapse osteonecrosis.

CT is a valuable asset in the evaluation and preoperative planning for patients with advanced glenohumeral degeneration. The scans give an excellent picture of the patient’s glenoid bone stock and the pattern of glenoid wear, which is essential for determining if standard glenoid components can be used or if a bone graft will be needed. Loose bodies may be seen in the axillary or subscapularis recess or attached to the synovium. In the case of malunions or nonunions, three-dimensional reconstruction helps to precisely show the bony deformities and defects before surgery. CT arthrography often is useful to evaluate both the bony architecture of the shoulder and the rotator cuff in patients with contraindications to MRI.

Preoperative Planning

Once the patient is determined to have advanced glenohumeral degeneration and has consented to a shoulder arthroplasty, preoperative planning includes careful evaluation of the radiographs as well as the CT scans, if obtained. As noted earlier, CT gives a clear view of the glenoid bone stock and wear pattern. Viewing these changes preoperatively allows the surgeon to prepare for the possibility that glenoid bone grafting or glenoid recontouring procedures may be necessary to re-center the subluxed humeral head. Templating systems often are available on digitized x-ray systems that allow the surgeon to plan for the size and position of the humeral and glenoid components.

To optimize accuracy of component implantation, some authors have advocated using surgical navigation equipment. In a randomized cadaver trial comparing traditional component implantation to a computer-assisted technique, the glenoid components placed with computer assistance were placed with significantly more accuracy based on postoperative CT scans. The most common error with the traditional implantation technique was overly retroverting the glenoid component. Similar results were found in a prospective, randomized clinical study of 20 shoulders. Despite significantly longer operative times, the navigation technique resulted in more accurate component placement in the axial plane.

In patients who have had previous shoulder surgery, infection can be evaluated by laboratory tests including erythrocyte sedimentation rate, C-reactive protein, complete blood cell count, and interleukin-6 levels. Aspiration and culture of glenohumeral joint fluid, holding the culture for at least 8 days to isolate Propionibacterium acnes, is essential if infection is suspected. Electromyography and nerve conduction studies should be obtained preoperatively in patients with suspected deficits. Finally, preoperative medical clearance often is warranted in this typically elderly population.

Hemiarthroplasty

• Perform subdeltoid, subcoracoid, and subacromial releases to release the proximal humerus. In the subcoracoid space, locate the axillary nerve by passing the volar surface of the index finger down along the anterior surface of the subscapularis muscle (Fig. 12-9C). If scarring and adhesions make identification of the nerve difficult, pass an elevator along the anterior surface of the subscapular muscle to create an interval between the muscle and the nerve. Always identify the axillary nerve and carefully retract and hold it out of the way, especially during the crucial steps of releasing and resecting the anteroinferior capsule.

• Incise the subscapularis 1 cm medial to the lesser tuberosity. Place two retention sutures in the subscapularis to be used as traction sutures when freeing the rest of the tendon from the underlying capsule and scar tissue. At closure, use the sutures to repair the tendon.

• Some authors prefer either a lesser tuberosity osteotomy or a release of the subscapularis directly off of bone. If external rotation is markedly limited, the subscapularis also can be reattached to the proximal humerus more medially to allow increased external rotation. Alternatively, the tendon can be lengthened with a coronal Z-plasty technique (Fig. 12-9D and Table 12-2).

• Incise the rotator interval, directing the cut medially toward the glenoid. Typically, a large amount of synovial fluid escapes as the joint is entered.

• Release the anteroinferior capsule from the humerus, and externally rotate the arm to bring the inferior aspect of the shoulder capsule into view. If osteophytes are present inferiorly on the humeral head, remove them to expose the capsule more fully. Take care to stay directly on bone so as not to injure the axillary nerve during the capsular release. The importance of the inferior capsule release cannot be overstated and must be thoroughly carried out to at least the 6 o’clock position to dislocate the humeral head and gain access to the glenoid.

• Once the capsule is adequately released, place a large Darrach retractor in the joint and gently externally rotate, adduct, and extend the arm to deliver the humeral head up and out of the glenoid fossa (Fig. 12-9E). If the humeral head cannot be delivered in this fashion, the inferior capsule must be released further.

• Prepare the humeral canal, using the humeral axis to reference the osteotomy. Initially, open the canal with a high speed burr at the base of the rotator cuff footprint and ream it to a size where appropriate “chatter” is felt in the shaft. Do not use motorized equipment for reaming, and be careful not to overream the canal, which could create a stress riser or cause a fracture.

• We prefer to use a cutting guide that employs extramedullary referencing, using the axis of the forearm as the reference point. With the cutting guide pinned into position at 30 degrees of retroversion, recheck the cutting angle and confirm that the height is such that the saw will not violate the rotator cuff or biceps tendon.

• Complete the osteotomy with an oscillating saw. If any inferior humeral head osteophyte remains, remove it with a rongeur.

• After the head cut, broach the humeral canal to the same size as the reamed canal. It is imperative to confirm proper position of the broaches in 30 degrees of retroversion during this step to prevent component malposition.

• Inspect the glenoid to confirm there is enough glenoid cartilage to provide an adequate bearing surface for the metal humeral head. After this inspection, check the humeral trial stem to ensure it is seated securely within the humeral canal. If so, tap the component stem into position, taking care to keep the stem in 30 degrees of retroversion.

• If cementing is deemed necessary because of a previous surgical procedure, fracture, osteoporosis, rheumatoid arthritis, or degenerative cysts, place a cement restrictor or a cortical bone plug from the resected humeral head 2 cm inferior to the tip of the prosthesis.

• Place a trial humeral head and reduce the glenohumeral joint using internal rotation and gentle traction. With the arm in neutral rotation, check the height of the humeral head to confirm anatomic reconstruction. As a rule of thumb, the most superior aspect of the humeral head should be 1 cm superior to the greater tuberosity.

• Also check the version to confirm that the humeral head rests directly across from the glenoid. With a thumb on the lesser tuberosity, push the humeral head posteriorly and then release it: 30% to 50% posterior excursion with immediate “snap back” of the humeral head is optimal. Evaluate forward elevation and internal rotation.

• Some authors recommend concomitant biceps tenodesis. If this is desired, it should be done before impaction of the humeral head.

• Once the checks have been performed, thoroughly clean the Morse taper, impact the humeral head into position, and reduce the joint for the final time.

• Perform a tight closure of the rotator interval as well as the subscapularis with heavy No. 2 suture. If the tendon was divided or lengthened, repair and secure it with heavy nonabsorbable sutures to allow immediate passive movement beginning the day after surgery. Place a drain in the deltopectoral interval and close it with No. 0 sutures. Close the skin in standard fashion and place the arm in a soft sterile dressing and a sling while the patient is still upright and before being aroused from anesthesia.

FIGURE 12-9 Hemiarthroplasty technique (see text). A, Semi-Fowler position with arm extended off table. B, Incision. C, Axillary nerves are identified. D, Coronal Z-plasty is used if external rotation is −20 degrees. E, Darrach retractor is used to lift head of humerus out of glenoid fossa.

SEE TECHNIQUE 12-1.

TABLE 12-2 Guidelines for Release of Subscapularis Tendon

SUBSCAPULARIS TENDON RELEASE	PREOPERATIVE RANGE OF MOTION
Release 1.5 cm medial to insertion	Passive external rotation ≥20°
Release subperiosteally, reattach medially	Passive external rotation >−20° and <20°
Subscapularis Z-lengthening	Passive external rotation ≤−20°

Data from Schenk T, Iannotti JP: Prosthetic arthroplasty for glenohumeral arthritis with an intact or repairable rotator cuff: indications, techniques, and results. In Iannotti JP, Williams GR Jr, editors: Disorders of the shoulder: diagnosis and management, Philadelphia, 1999, Lippincott Williams & Wilkins.

Postoperative Care

Patients are instructed in a gentle home exercise program with passive forward elevation to 90 degrees and passive external rotation to neutral. Patients typically are discharged from the hospital 1 or 2 days after surgery and are encouraged to use a pillow behind the elbow while recumbent in the sling to support the extremity. Full-time sling immobilization continues for 6 weeks, followed by 6 weeks of sling use only in unprotected environments. Therapy progresses to full passive range of motion by 6 to 12 weeks and to isometric strengthening at 10 weeks.

Outcomes

Hemiarthroplasty has been reported to significantly relieve pain in 75% to 95% of patients with glenohumeral arthritis and severe rotator cuff deficiency, with more modest improvements in range of motion and strength. Results may be compromised by persistent pain, anterosuperior instability, and progressive bone loss.

When used for the treatment of osteonecrosis, hemiarthroplasty has been reported to provide consistently good pain relief in 90% to 100% of patients, with an almost normal range of motion (Table 12-3). Results are not quite as good in patients with rheumatoid arthritis, osteoarthritis, or posttraumatic glenohumeral arthrosis but are satisfactory in most patients, although range of motion is decreased.

TABLE 12-3 Reported Results of Shoulder Hemiarthroplasty for Rotator Cuff Tear Arthropathy

Modified Hemiarthroplasty—interposition Arthroplasty and Glenoidplasty (Ream and Run)

As it has become clear that glenoid arthritis continues to be a long-term concern for patients undergoing isolated shoulder hemiarthroplasty, some authors have explored various types of glenoid resurfacing procedures, particularly for younger, higher-demand patients. These interposition techniques aim to allow the metal humeral head to articulate with a cushioning surface rather than with the native glenoid in an effort to minimize arthritic progression and subsequent pain. Although most interposition procedures have demonstrated early success, there are few long-term reports; therefore, further follow-up studies are necessary to better determine their ultimate outcomes.

Fascial interposition hemiarthroplasty (biological resurfacing) has been recommended for use in young, active patients with osteoarthritis. The glenoid is resurfaced using the anterior capsule sewn over the glenoid face or a free fascia lata graft. After humeral osteotomy and removal of osteophytes, the glenoid surface is débrided, slightly increasing the anteversion in the process. If thick enough, the subscapularis-capsule complex is split in the coronal plane, and the posterior leaf is draped over the glenoid and secured to the posterior labrum with suture or suture anchors. If inadequate capsule is present, a segment of fascia is harvested from the thigh, doubled on itself, and anchored to the center of the glenoid with a suture and to the anteroposterior labrum with heavy suture, such as No. 1 cotton Dacron (Deknatel, Fall River, MA). Good long-term outcomes have been reported with this biological glenoid resurfacing technique. Outcomes at 2 to 15 years of follow-up were excellent or satisfactory in 86% of patients, with an average American Shoulder and Elbow Surgeons (ASES) score of 91. Glenoid erosion has been noted to progress but does stabilize about 5 years after the procedure. Other studies, however, have noted a high number of failures and poor outcomes using Achilles tendon allograft as a resurfacing material with hemiarthroplasty.

Recently, lateral meniscal allografts have been used as an interposition material. In this procedure, the anterior and posterior horns of the allograft are sewn to each other to form a circular surface for articulation with the humeral head. The allograft is then laid onto the glenoid and secured, typically with suture anchors (Fig. 12-10). Significant improvements in pain and function have been reported with this procedure. Although joint space narrowing did occur, glenoid erosion did not progress, suggesting that the lateral meniscus may offer some protection against glenoid wear.

FIGURE 12-10 Lateral meniscal allograft used as interposition material.

A third technique that has been advanced involves concentric reaming of the glenoid combined with shoulder hemiarthroplasty, the “ “ream and run” procedure. Range-of-motion and Simple Shoulder Test scores were reported to be significantly improved after this procedure, and no shoulder procedures were subsequently revised. Essentially equivalent Simple Shoulder Test scores were found between total shoulder arthroplasty and “ream and run” hemiarthroplasty at 3 years after surgery.

Resurfacing Hemiarthroplasty

With the success of humeral hemiarthroplasty, other techniques have been developed to allow less invasive replacement of the proximal humerus but also to preserve bone stock. These humeral resurfacing procedures do not use a stem for intramedullary fixation but instead form a cap over the humeral articular surface and are typically stabilized with a smaller post in the metaphysis (Fig. 12-11). Outcomes of humeral resurfacing have generally been successful, with patient satisfaction rates as high as 93% and overall results similar to that of stemmed prostheses. Several series have reported similar success in specific patient cohorts with rheumatoid arthritis, osteoarthritis, and cuff tear arthropathy. An average operative time of 40 minutes was reported for humeral resurfacing in a cohort of patients older than 80 years of age, with no perioperative deaths or other serious medical complications, and in a young group of patients (average age 42 years) there were significant improvements in pain and functional scores and all but one patient returned to full activity.