The indications, techniques, and results of reverse shoulder arthroplasty, evolved exclusively from leading shoulder centers in Europe, are found in fewer than 20 published reports of a medialized center of rotation (COR) implant, with a mean of 38 patients per report (range: 5 to 191) and a mean follow-up of slightly more than 3 years. Three reports from the United States reveal the results of a lateralized COR implant.
Indications for this procedure include irreparable anatomic or functional destruction of the rotator cuff, unstable glenohumeral joint COR, a functioning deltoid, preserved glenoid morphology, patient age of 70 years or older, poor function, low activity level, pain, and no other options.
Contraindications include Infection, neuropathic arthropathy, permanent axillary nerve palsy, extreme osteoporosis, irrevocable glenoid deficiency, and profound humeral loss.
The superior approach is preferred for first-degree cases, those with concomitant “deltoidplasty,” and when complex posterior glenoid bone grafting is required.
The deltopectoral is preferred when there is stiffness or when humeral shaft access is necessary.
subscapularis – preserve/repair
Essential exposure is 5 cm or more onto anterior and inferior glenoid neck.
glenoid implant – maximum inferior register.
It is mandatory to ensure soft tissue tension.
Failure to adequately eliminate or minimize osseous and soft tissue impediments to motion can lead to instability.
Failure to account for and prevent infection
Failure to analyze, expose, prepare, and properly insert the implant can lead to glenoid loosening.
Failure to maximize glenoid-implant distance can result in notching.
Surgical technique for medialized center of rotation (DePuy Delta Xtend).
As the results of humeral head prosthetic reconstruction emerged in the late 1960s and early 1970s, the inferior functional impact of irreversible inadequacies of the rotator cuff, deltoid muscle, or the glenoid articular surface became apparent. To this end and with the advent of the successful use of acrylic cement for prosthetic hip reconstruction by Charnley, many different shoulder surgeons, including Charles Neer II, undertook bold attempts to achieve secure fixation of various prosthetic glenoid components to the scapula. The mechanical advantage they sought for these cuff-deficient and arthritic shoulders required that the glenoid component be intimately coupled to the prosthetic humeral component, hence a fixed fulcrum shoulder arthroplasty. As Neer predicted and without exception, these prosthetic designs failed miserably.
With these experiences well established, Grammont and Baulot approached this most difficult problem with different strategy. Their concept was to medialize and distalize the center of rotation not only to optimize the biomechanics of the shoulder and but also take advantage of the deltoid muscle, which would become the primary motor for upper limb elevation. To minimize the risk of prosthetic glenoid loosening, the glenoid component was designed without a neck, placing the center of rotation at or medial to the junction between the implant and the glenoid. Stability and motion were enhanced with a large hemispherical ball for the glenoid and an articulating humeral component with a matching radius of curvature. With their concepts realized in the implant design and its early application, the stage was set for the next era in shoulder reconstruction—reverse shoulder arthroplasty ( Fig. 18–1 ).
Generally speaking, reverse shoulder arthroplasty is indicated for conditions of the shoulder that have as their common pathoanatomic feature the irreparable anatomic or functional destruction of the rotator cuff. This phenomenon is present to the extent that it results in an unstable center of rotation for the glenohumeral joint. This feature is perhaps the strongest single indicator of the need for reverse shoulder arthroplasty. The conditions are typically accompanied by elements of pain. The extent of weakness, roughness, instability, stiffness, and pain varies with the underlying cause. Indications are satisfied fully if no other reasonable treatment option for the clinical condition is possible . Two additional requisites must exist: (1) a functioning deltoid muscle and (2) adequate glenoid bone. The criterion of age is an important factor when reverse shoulder arthroplasty is being considered. Widespread recommendations are that shoulder reconstruction with reverse shoulder arthroplasty should be limited to elderly patients, around 70 years and older, who have poor function, low activity, and severe pain in the presence of sufficient quantity and quality glenoid bone capable of providing unyielding fixation of the prosthetic glenoid component. This appeal is further supported by the separate reports of Guery et al. and Sirveaux et al., who brought attention to a high probability of failure after 6 and 7 years, respectively. It should be considered a salvage procedure, but clinical scenarios for which this recommendation must be altered are not infrequently encountered. Boileau et al. suggested that the procedure should not be offered to young patient with ambitions of having a normal shoulder.
The most common primary disorder of the shoulder for which reverse shoulder arthroplasty is indicated is rotator cuff tear arthropathy ( Fig. 18–2 A ). Varying degrees of collapse of the humeral head may accompany the disorder. Another primary condition is glenohumeral osteoarthritis in association with a “massive” irreparable tear of the rotator cuff. Finally, chronic rotator cuff tear with resultant “pseudoparalysis” or pseudoparesis of the shoulder in the absence of pain may be effectively treated with reverse shoulder arthroplasty.
Previous surgical treatment has been rendered but has not achieved a successful outcome. The most common failure for which reverse shoulder arthroplasty is considered is that of rotator cuff repair. The failure of prosthetic shoulder implants, most often hemiarthroplasty, is an excellent indication for reverse shoulder arthroplasty ( Fig. 18–2 B ). Failures of proximal humerus fracture repair often benefit from reverse shoulder arthroplasty. Failures of shoulder resection or glenohumeral arthrodesis are sometimes salvageable with reverse shoulder arthroplasty.
Certain nonunions or malunions of the proximal humerus, especially those in which anatomic prosthetic reconstruction is particularly unsuitable, are best treated with reverse shoulder arthroplasty ( Fig. 18–2 C ). The same can be said for chronic glenohumeral dislocations. Reverse shoulder arthroplasty is a reasonable consideration for the treatment of extremely comminuted, unstable three- and four-part proximal humerus fractures and fracture dislocations in older patients with osteoporotic bone.
Tumors of the proximal humerus are rare indications for reverse shoulder arthroplasty. Reverse shoulder arthroplasty is discouraged in inflammatory arthropathy by some authors due to glenoid osteoporosis. However, in its absence, reverse shoulder arthroplasty may serve these patients very favorably.
Presurgical Considerations And Preoperative Planning
The functional status of the deltoid muscle must be verified. Manual muscle testing for effective contractility and strength (three out of five) is usually sufficient. On rare occasions it may be necessary to assess the innervation status of the deltoid muscle with electromyography.
The patient should receive general medical clearance to be anesthetized and to undergo the operation. When reverse shoulder arthroplasty is contemplated, suspicion for and identification of active or indolent infection is mandatory. The patient’s history may identify risk factors: diminished nutritional status, inflammatory or connective tissue diseases, medications (immunosuppressives, steroids), diabetes, chronic cutaneous diseases, poor dentition, frequent bouts of bronchitis or urinary tract infections. Prior shoulder procedures and their complications may provide useful clues: drainage, would healing, protracted fever, persistent pain that is different that the pain experienced prior to the operation. The physical examination may reveal low-grade fever, shoulder warmth, shoulder erythema, or rash. Plain radiographs may demonstrate soft tissue swelling, radiolucencies consistent with osteolysis, or loosening of existing implants. Magnetic resonance imaging (MRI), nuclear medicine, or computed tomography (CT) can detect abnormalities that suggest the diagnosis of infection. Serum studies are essential and include a complete blood cell count with differential, C-reactive protein, erythrocyte sedimentation rate, and blood cultures. Synovial fluid analysis and biopsies of the tissue in the surgical field may prove helpful.
Plain radiographs are a requisite for preoperative planning. An anteroposterior (AP) glenohumeral joint view orthogonal to the plane of the scapula (Grashey’s view) and an axillary lateral view are essential. Sometimes the entire humerus must be imaged to appreciate the full length of previous implants, cement mantles, or bone deformity. A weighted abduction Grashey’s view complements the series and may provide the only clue as to superior glenohumeral instability resulting from rotator cuff deficiency ( Fig. 18–3 ) . Two-dimensional implant templates aid in the determination of the position and orientation of the components and any adjunctive fixation screws. Their application will be more accurate when using fluoroscopically positioned anteroposterior views of the scapula such that the saggital plane and the plane tangent to the face of the glenoid coincide. Humeral component templates aid in the determination of implant size and stem diameter and length. They may facilitate recognition of deformity that may inhibit humeral canal access or implant accommodation.
CT scanning is used in most cases to define the morphology of the proximal humerus and the glenoid, especially when the glenoid is poorly visualized on the axillary lateral view ( Fig. 18–4 ). Planning for glenoid preparation begins with either superb plain films or a high-quality CT scan. MRI is more discriminatory for the soft tissue around the shoulder, especially the rotator cuff. Both imaging tools delineate the atrophy phenomenon of fatty replacement of muscle.
Surgical Approach Options
The description of the surgical technique is applicable to many of the indications listed earlier. For the surgical technique for specific implant systems not described here, the reader is referred to their respective industry representatives. Although the Delta Xtend reverse shoulder arthroplasty system is detailed here, the fundamentals of the surgical technique are applicable to most systems ( Fig. 18–5 ).
The anterosuperior approach for total shoulder arthroplasty was described by Mackenzie in 1993. A more recent and detailed description specifically for reverse shoulder arthroplasty was provided by Seebauer. The indications for an anterosuperior (or superior) approach include primary rotator cuff tear arthropathy and failed rotator cuff repairs, especially those cases in which some form of deltoid “plasty” is anticipated. It is best suited for cases of primary rotator cuff tear arthropathy, patients of small or medium skeletal stature, or mobile shoulders or when the use of smaller implants is anticipated. It is the approach of choice when rotator cuff repair or reverse shoulder arthroplasty is undecided.
Contraindications for a superior approach are revision operations (other than failed cuff tears) and global shoulder stiffness as observed in cases of trauma sequelae and prosthesis failures.
The advantages of a superior approach are (1) cosmesis; (2) preservation of stabilizing soft tissues, especially all or part of the subscapularis; and (3) posterior glenoid visualization and access.
There are several disadvantages to the superior approach. It is an approach that it is mostly unfamiliar to surgeons in the United States for shoulder arthroplasty. It is difficult to completely expose the humeral head, and there is limited access to the humeral shaft should it become necessary. Soft tissue releases can be more difficult to perform, especially the inferior capsule. Sufficient exposure of the inferior glenoid and lateral scapular pillar is difficult and often limited. This may result in tendencies to malposition the metaglen with an inferior tilt. With the superior approach, there is greater risk to the axillary nerve and deltoid origin integrity and of deltoid “myotrauma.” Protection of the deltoid postoperatively is required to avoid dehiscence from the acromion process.
A transacromial pathway is an option when the superior approach is selected. This appears to have been the approach Grammont and Baulot selected. Although it may widen the field of exposure, complications related to fixation and successful healing pose significant drawbacks to the approach, especially in the presence of rheumatoid arthritis, osteoporosis, or previous operations.
The indications for the deltopectoral approach are primary rotator cuff tear arthropathy, trauma and its sequela, failed arthroplasty, and proximal humeral tumors. It is best suited for cases of significant stiffness, in patients with large skeletal stature, when the use of larger implants is anticipated, and when there is planned removal of existing fracture hardware or prosthetic implants. There are probably no contraindications to the deltopectoral approach.
The advantages of the deltopectoral approach include its familiarity as a utility anterior approach to the shoulder. The deltoid is not detached from its origin on the acromion or clavicle. The approach is potentially extensible to allow access, if necessary, to the entire humeral shaft. Superior visualization of and access to the inferior glenoid and lateral scapular pillar are notable features of the deltopectoral approach. The approach facilitates all soft tissue releases and enables, when necessary, adjunctive tendon transfers (latissimus dorsi, teres major).
One disadvantage of the deltopectoral approach is that it is usually necessary to release the subscapularis, often completely. In the same vein, it is often impossible to repair the subscapularis after the prosthetic reconstruction has been completed. The posterior glenoid may be difficult to access. Myotrauma to the deltoid is possible during the preparation of the glenoid.
Indications for the previous surgical approach are failed rotator cuff repair, failed arthroplasty, and failed trauma. It is best suited for conditions specifically mentioned for the superior and deltopectoral approaches. The contraindication for the previous approach is when it fails to accommodate the surgical pathology.
The advantages of the previous approach are cosmesis (one less wound), potentially less trauma, and potential opportunities to correct adverse sequelae (iatrogenic or otherwise). Disadvantages of the previous approach are the potential for insufficient exposure and the fact that the surgical intervals and planes are obliterated by scar tissue.
Hybrid (“Extensile Superior”) Approach
The hybrid “extensile superior” approach mandates the skin incision via Langer’s lines only; laterally oriented incisions cannot be reasonably extended. The indications for this approach are primary rotator cuff tear arthropathy, failed rotator cuff repair, and anticipation of deltoid “plasty.” The extension of this approach supplements the existing superior approach, functioning as “emergency access” via the deltopectoral interval.
This hybrid approach is best suited for primary rotator cuff tear arthropathy, patients of small or medium skeletal stature, mobile shoulders, and those cases in which the use of smaller implants is anticipated. The contraindications for this hybrid approach are revision cases (other than failed rotator cuff repairs) and stiff shoulders such as those resulting from failed shoulder prostheses and trauma.
One big advantage of this hybrid approach is enhanced access to the inferior glenohumeral joint and the upper 25% of the humeral shaft. Another is that is adds a component of familiarity to the surgical approach for U.S. surgeons.
Hybrid (“Blue Devil”) Approach
The hybrid “blue devil” approach utilizes the deltopectoral approach together with a transdeltoid (percutaneous) portal for access to the glenoid and was first described by Basamania. The indications for the approach are primary rotator cuff tear arthropathy, trauma and its sequelae, failed arthroplasty, and tumors. It is best suited for patients with significant stiffness, those of large skeletal stature, when the use of large implants is anticipated, and in the presence of existing fracture fixation hardware or prosthetic implants. There appear to be no contraindications to this surgical approach. The advantages of the approach include the potential reduction of “myo-trauma” to the anterior deltoid (split vs. crush) and “direct on” access to the glenoid. A theoretical disadvantage of the approach is the additional risk to the axillary nerve.
The patient is in a low-angled beach-chair position with the head secured to a headrest specifically designed for shoulder surgery. The skin incision follows the line from the midpoint of the clavicle to the midpoint of the arm (deltoid tuberosity). Subcutaneous flaps are elevated to delineate the fatty stripe that defines the deltopectoral interval. Dissection medial to the cephalic vein while electrocoagulating small crossing vessels permits vein retraction laterally with the deltoid muscle. The clavipectoral fascia is incised from the inferior border of the coracoacromial ligament distally to the superior border of the tendon of the sternal head of the pectoralis major. Sharp and blunt dissection of the humeroscapular motion interface (subacromial, subdeltoid, and subcoracoid) often requires the excision of hypertrophic bursae. The axillary nerve is palpated at the anteroinferior border of the subscapularis muscle and protected at all times. The anterior humeral circumflex vessels (“three sisters”) at the inferior border of the subscapularis are electrocoagulated near the approach the humerus.
The integrity of the biceps long head tendon is determined. If the tendon is intact, its sheath is opened and the tendon is tenodesed to the pectoralis major tendon with three nonabsorbable sutures. The proximal biceps tendon and hypertrophic sheath are excised.
A tag suture is placed in the tendon of the subscapularis 2 to 3 cm medial to its point of insertion on the lesser tuberosity. Electrocautery is used to release the tendon, along with the underlying capsule, from the lesser tuberosity and the proximal humerus. The remaining inferior and posteroinferior capsule is detached from the humerus.
Preliminary Humeral Preparation
The humeral head is dislocated, and the humeral canal is entered with an awl ( Fig. 18–6 ). Sequentially larger blunt-tipped reamers are passed by hand into the intramedullary canal of the humerus to a predetermined depth until contact is made with the endosteal cortex. The reamer is exchanged for an intramedullary alignment rod of the same diameter. The level of humeral head resection may vary from case to case, but it is preferable not to violate the integrity of the lesser tuberosity ( Fig. 18–7 ). There is no consensus as to the extent of version of the humeral osteotomy with recommendations from slight anteversion to anatomic retroversion. Limitations to humeral rotation with the arm in neutral are perhaps influenced by the version selected for the osteotomy; that is, if more internal rotation is desired, the plane of resection is oriented in neutral to slight anteversion. If more external rotation is desired, the plane of resection is oriented in retroversion. Bufquin et al. stated that retroversion was not found to be necessary for stability and preferred neutral to increase internal rotation. To maximize the exposure of the glenoid, the humerus must be retracted to the fullest extent possible. It is important to reduce the bulk of the proximal humerus by removing all peripheral osteophytes. Further relief of the bulk of the proximal humerus can be obtained by excision of the perimeter of the portion of the head that remains after resection. A metal plate applied flush to the resected surface of the proximal humerus affords protection from the deforming pressure of glenoid-exposing retractors.
While developing glenoid exposure, it is critical to note the presence of the axillary nerve and protect it at all times. Anticipating that the subscapularis musculotendinous unit is both functional and reattachable, maneuvers are undertaken to ensure its mobility. Both sharp and blunt methods are used to mobilize the subscapularis. The rotator interval, if present to any degree, is released to the base of the coracoid process. The upper portion of the subscapularis is released from the base of the coracoid process with electrocautery. Caution is exercised to prevent neural injury as the dissection proceeds medial to the base of the coracoid process, where the subscapularis is often tethered by scar or fascial bands. The anterior aspect of the subscapularis is freed from the overlying coracoid muscles. The dissection proceeds inferiorly with vigilance for the axillary nerve as the lower border of the subscapularis is mobilized The release is completed by separating the posterior border of the subscapularis tendon and distal muscle belly from the anterior and anteroinferior glenoid rim, glenoid neck, and the lateral-most part of the scapular body. Any remaining portions of the labrum, capsule, synovium, and biceps long head origin are excised.
It is essential to release the entire capsule from the perimeter of the glenoid to permit displacement of the reconstructed center of rotation inferiorly. The anterior capsule is excised routinely and the inferior and posterior capsule selectively depending upon the extent of contractures and adequacy of exposure. To maximize the exposure and access to the glenoid neck and the lateral scapular pillar, the origin of the triceps long head is incised from the infraglenoid tubercle. Sufficient exposure will permit the surgeon’s index finger free passage from the base of the coracoid process circumferentially to a point well beyond the most inferior aspect of the glenoid. Identification of the following osseous scapular points of orientation is mandatory: base of the coracoid process, glenoid centering point, inferior part of the glenoid neck and infraglenoid tubercle, lateral border of the scapula. Retractors are placed around the glenoid face in a manner that enables a clear view of its entirety ( Fig. 18–8 ).
All remaining articular cartilage is removed (large straight curette) from the glenoid face. Not only does this enable accurate correlation with the radiographs, but also the products of bone reaming will not be contaminated with cartilaginous debris, leaving it suitable for graft material.
On the condition that the morphology of the glenoid hasn’t been altered by the disease, a guide pin is oriented perpendicular to the plane of the glenoid face either freehand or with the assistance of an alignment tool. Preoperative templating aids in the determination of the entry point of entry into the glenoid. To optimize prosthetic biomechanics and minimize the opportunity for inferior scapular erosion (notching), the metaglen is positioned as inferior as possible. The point of entry is usually the centerpoint of the circle that subtends the perimeter of the lower glenoid. This point is inferior to the equator and on or just posterior to the longitudinal axis. The guide pin is securely anchored in the scapula by driving it through the far cortex. The accuracy of guide pin placement is verified when it is palpated at the junction of the glenoid neck and body near the glenoid centering point ( Fig. 18–9 ).
The cannulated metaglen reamer is passed over the guide pin, and glenoid reaming proceeds with a power tool until the perimeter of the reamer makes contact with the bone. The metaglen reamer should be used very carefully to avoid an inadvertent fracture of the glenoid, especially if the glenoid is excessively sclerotic or excessively weak. It is preferable to maintain as much subchondral bone as possible. The accuracy of reaming determines the surface area contact between the bone and the implant. Ideally the metaglen is totally supported by native bone. There are times when excessive wear or deformity precludes full support without what might be considered excessive reaming, a situation best avoided. At the completion of primary reaming, the guide pin remains in the glenoid and a second cannulated reamer is slid over it into position on the glenoid. This hand-powered reamer eliminates the bone peripheral to the first reamer, a maneuver that accommodates the space-occupying glenosphere for proper engagement of the Morse taper between the glenosphere and the metaglen. The accuracy of reaming may be verified by using a cannulated translucent surface trial that ascertains contact with the bone surface. Further reaming is performed as necessary while respecting the preservation of bone quantity. With glenoid surface preparation optimized, a cannulated pilot drill with a built-in stop is passed over the guide pin to create the space for the central post of the metaglen, followed by removal of the guide pin.
Bone graft “mush” applied to the surface either of the glenoid or the back of the metaglen immediately prior to implantation serves to fill any remaining voids and maximizes the bony contact and support of the metaglen. The rotational orientation that enables the inferior and superior screws to be contained within the lateral pillar of the scapula and the base of the coracoid process, respectively, is identified. This usually requires slight clockwise rotation or counterclockwise rotation from the anatomic long axis of the glenoid face for the right and left shoulder, respectively. The metaglen stem is slightly oversized, enabling potential press fit. It is gently impacted with slight mallet blows in proper orientation for screw placement. After accurate metaglen seating is confirmed, the insertion handle is removed. Two options for screw fixation are available: locked and unlocked. It is customary to use locking screws in the superior and inferior holes of the metaglen and nonlocking screws in the anterior and posterior holes, although locking screws can be used in all holes if they are 24 mm or greater. All screws have the option of insertion along a variable axis, made possible by the shape and orientation of the screw holes and a special drill guide. The recommended sequence for screw insertion is inferior, superior, anterior, and posterior. It is helpful to palpate the lateral scapular pillar while using a combination of drill and push to create the inferior screw hole. This technique enables corrective measures to be employed before the drill bit inadvertently passes outside the bone. Intraosseous containment may be confirmed by sounding to the depth of the drilled hole with a blunt K-wire. If penetration is anticipated or identified, the drill is redirected or predrilled. The inferior screw is typically 36 or 42 mm in length while the superior one is 30 to 36 mm. The anterior and posterior screws are either 18 or 24 mm. Secure all screws to the metaglen to maximize compression to the glenoid. The superior and inferior screws lock to the metaglen by means of their smaller, center-oriented setscrew, which, upon tightening, expands the fluted head of the primary screw, satisfactorily establishing the lock ( Fig. 18–10 ).