Reverse Shoulder Prosthesis for Acute and Chronic Fractures

CHAPTER PREVIEW

CHAPTER SYNOPSIS:

Primary humeral head replacement for the treatment of proximal humerus fractures, when indicated, reliably provides good results in terms of pain relief. However, the results for function, range of motion, and muscle power are discouraging. The ability to restore the anatomy and hence balance the force couples around the shoulder must be possible in order to consider anatomic reconstruction in the setting of acute and chronic fractures. The reverse shoulder prosthesis has been used increasingly for the treatment of glenohumeral arthritis associated with rotator cuff deficiency with promising results. The reverse shoulder prosthesis is an available alternative for the management of acute proximal humerus fractures, fracture sequelae, and failed hemiarthroplasty for fracture when the circumstances for anatomic reconstruction are unfavorable.

IMPORTANT POINTS:

1

The feasibility of anatomic reconstruction must be taken into consideration when selecting a reliable treatment for proximal humerus.
2

When anatomic reconstruction is not possible, the reverse shoulder prosthesis represents a reliable alternative for the management of these complex injuries in the acute and chronic setting.
3

Acute fracture indications for reverse shoulder arthroplasty include the following:
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  Comminuted four-part proximal humerus fracture in an elderly patient with irreconstructible tuberosities
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  Inadequate social structure to undergo extensive rehabilitation of hemiarthroplasty
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  History of previous failed rotator cuff surgery or severe supraspinatus atrophy on computed tomography (CT) scan
4

Chronic fracture indications for reverse shoulder arthroplasty include the following:
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  Treatment of fracture sequelae (nonunion/malunion)
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  Posttraumatic glenohumeral arthritis in the rotator cuff deficient shoulder.
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  Failed hemiarthroplasty for the treatment of proximal humerus fracture
5

Contraindications include the following:
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  Dysfunctional deltoid muscle
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  Active Infection
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  Delicate medical condition
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  Impaired cognitive function

CLINICAL/SURGICAL PEARLS:

1

A careful history is essential in identifying prefracture rotator cuff deficiency.
2

Careful neurologic examination must not be overlooked.
3

Plain radiographs and CT scan are helpful tools for the evaluation of proximal humeral and tuberosity bone stock. CT scan can be used additionally to assess rotator cuff muscle status.
4

Every attempt to restore the internal rotation/external rotation (IR/ER) force couple should be made in the setting of acute fracture management using the reverse shoulder prosthesis.
5

In the management of fracture sequelae, an effort to bypass existing deformity must be made in order to avoid the need for proximal humeral or tuberosity osteotomy.
6

In the treatment of shoulder dysfunction after failed hemiarthroplasty for fracture, proximal humeral bone loss associated with prosthesis removal may be addressed with a proximal humeral allograft RSP composite.

CLINICAL/SURGICAL PITFALLS:

1

An inability to elicit a history of premorbid shoulder dysfunction may lead the surgeon to render ineffective treatment for acute proximal humeral fractures.
2

Careful preoperative planning must be carried out in order to address potential problems at the time of surgical reconstruction of proximal humerus fractures in the acute and chronic setting.

HISTORY

Proximal humerus fractures have represented a demanding clinical problem for both the patient and the orthopedic surgeon since the first documented description by Hippocrates in 460 bc . Initial treatments consisting of some form of immobilization followed by range of motion provided good results for nondisplaced fractures. This treatment, however, yielded poor results for displaced and high-energy fractures. Several contributions throughout history have awarded us a better understanding of the more complex fracture patterns. These fractures were first recognized to occur along the epiphyseal scar of the proximal humerus by Codman in 1934. Based on this anatomic description, the four-part classification was reported by Neer in 1970 and has since prevailed as the most widely used system for diagnosis and treatment of these fractures. As the deforming forces that lead to fracture displacement were recognized, surgical treatments were developed to impart a more suitable opportunity for improved outcomes. In 1955, Neer reported his results for acute humeral head replacement in the treatment of fracture dislocations. Since his contribution, a wide variety of improvements in implant design and surgical techniques used in arthroplasty have become available. Nevertheless, the treatment of these acute fractures in the elderly continues to evoke frustration for the patient and the orthopedic surgeon. Also, options routinely available for the treatment of the sequelae that stem from these injuries are often ineffective in providing reasonable results.

INTRODUCTION

The reverse shoulder prosthesis has been used increasingly for the treatment of glenohumeral arthritis associated with rotator cuff deficiency with promising results. As our current understanding of this prosthesis has developed, so have the indications for its use in the treatment of complex shoulder problems. Proximal humerus fractures are common injuries occurring in all age-groups. Their diagnosis and treatment and the sequelae that stem from these injuries represent a problem for the patient, with limited available treatment alternatives for the orthopedic surgeon. The treatment of these injuries in the elderly population remains a surgical challenge.

Current treatment algorithms consider the classification proposed by Neer as well as other patient-related factors to tailor treatment strategies that may maximize functional outcome as well as patient satisfaction. Given the delicate blood supply to the articular segment of the humeral head and its associated disruption in three- and four-part fractures, prosthetic replacement of the proximal humerus is currently indicated for the treatment of these injuries. Primary humeral head replacement for the treatment of proximal humerus fractures, when indicated, reliably provides good results in terms of pain relief. However, the results for function, range of motion, and muscle power are discouraging. These results should be analyzed, taking into consideration associated patient factors, such as age and the presence of neurologic deficits at the time of injury, that have been found to be predictive of short- and long-term functional outcomes. The role of hemiarthroplasty in the treatment of these fractures, however, has provided disappointing results influenced by a variety of technical and intrinsic patient factors. One study reports a significant association of outcome to the quality of anatomic reconstruction of the tuberosities, the accuracy of prosthesis height and version, and the ability to reliably restore lateral humeral offset. The ability to restore the anatomy and hence balance the force couples around the shoulder must be possible in order to consider anatomic reconstruction in the setting of acute trauma. This requires anatomic tuberosity reconstruction as well as functional rotator cuff muscle tendon units and adequate proximal humerus bone stock. Factors that can complicate the decision-making process are the presence of preexisting degenerative joint disease, preexisting rotator cuff tendon and muscle disease, and extensive fracture comminution with compromised tuberosity bone. Under these circumstances, options become limited. The use of hemiarthroplasty for the treatment of proximal humerus fractures under these dismal conditions is unsuitable given the high probability of poor outcomes. Careful preoperative planning should be done in the context of these prognostic factors.

Evaluation should begin with a complete patient history, including surgical history, as well as a thorough physical examination. Factors in the history that are pertinent include patient age, a history of previous shoulder pathology, and a detailed surgical history. One should also enquire about patients’ medical comorbidities, as well as the quality of their social support structure. Meticulous care is necessary in this evaluation in order to identify details pertinent to surgical decision making. This will aid in determining the need for additional studies and will help us along the treatment algorithm. In the acute setting, however, a high index of clinical suspicion should be employed given the unreliable nature of the physical examination due to associated pain. Plain radiographs (anteroposterior [AP] in the plane of the scapula and axillary view) of the shoulder should be routine in the evaluation of these patients. Computed tomography (CT) scan should also be included in the routine evaluation, both in the acute and the chronic setting for various reasons. Information about the available glenoid bone stock and version as well as characterization of fracture fragments can be of assistance. Rotator cuff muscle status can also be inferred from the CT scan, as described by Goutallier et al. and Fuchs et al. ( Fig. 19-1 ). This can help the surgeon assess the possibility of preexisting chronic rotator cuff disease and use this information to predict the functionality of the muscle tendon units. A high percentage of atrophy in the supraspinatus fossa would not favor the anatomic reconstruction alternative but rather reconstruction using reverse shoulder arthroplasty.

The decision-making process should proceed in a logical fashion after considering fracture characteristics and patient-specific factors. After narrowing the surgical options, room should be left for intraoperative tailoring of final treatment because some factors are best assessed during the surgical procedure. In the evaluation of an acute proximal humerus fracture in a medically fit patient, displacement defines the need for surgical management. Once surgery is considered, the treatment alternatives will be based generally on patient age. Every attempt at anatomic reconstruction should be made for the physiologically young patient. In the elderly or when the viability of the articular segment is compromised, arthroplasty should be considered. The specific type of arthroplasty should depend largely on the possibility of balancing the force couples of the shoulder. If preoperative evaluation identifies adequate rotator cuff muscle tendon units as well as adequate tuberosity bone stock, an attempt at articular reconstruction using hemiarthroplasty should be considered. If preoperative evaluation reveals preexisting degeneration of the glenoid, the glenoid may be resurfaced. If patient history reveals a preexisting cuff tear arthropathy ( Fig. 19-2 ) or failed previous rotator cuff surgery, reverse shoulder arthroplasty should be available at the time of surgery. If imaging studies suggest irreconstructible tuberosities or incompetent rotator cuff muscle tendon units in an elderly patient (physiologic age older than 70), reverse shoulder arthroplasty should also be considered. As previously mentioned, there should be a role for intraoperative variation because the information gathered from the imaging studies may vary from what is encountered during the procedure.

The use of arthroplasty for reconstruction of chronic proximal humerus fractures and their sequela should follow a similar algorithm, considering some additional factors. Treatment history should be obtained in detail, with particular attention to surgical history. Sequelae from the treatment of these fractures may include malunion, nonunion, and failure of previous hemiarthroplasty. The final decision in treatment will be determined by the ability to balance the soft tissues and the ability to obtain exposure. Intraoperatively, if exposure is not possible by conventional methods and dysfunctional and immobile cuff tissue encountered, the alternative of releasing the supraspinatus to gain better exposure may be selected if the alternative of reverse shoulder arthroplasty is an option. This scenario of trying to reconstruct proximal humeral fractures after attempted repair either with open reduction and internal fixation or the use of hemiarthroplasty adds the complexity of scar formation from attempted surgical trauma as well as having to remove the previous implant.

Treatment of fractures of the proximal humerus by conservative or surgical means may give rise to unsatisfactory anatomic outcomes resulting in either malunion or nonunion. These can occur surrounding the tuberosities, articular segment, or surgical neck to varying degrees. These late posttraumatic findings are associated with significant pain and poor function with resulting disability. These injuries, malunions and nonunions, can be further subcategorized as intra-articular or extra-articular, and this in turn will greatly determine what treatment alternative is most adequate. Extra-articular nonunions found at the surgical neck may be managed with internal fixation (ORIF) and bone grafting. If the nonunion has an intra-articular component, some form of arthroplasty may better serve to restore function. In the setting of tuberosity nonunion, mobility of the associated rotator cuff muscle tendon unit and the degree of atrophy seen on CT or magnetic resonance imaging (MRI) can aid in the decision-making process. In the setting of intra-articular malunion with resulting posttraumatic glenohumeral arthritis, some form of arthroplasty is recommended in order to reestablish smooth articulating surfaces. If adequate balancing of the soft tissues can be obtained in the setting of a competent rotator cuff, total shoulder arthroplasty is the preferred alternative. Exposure for the planned reconstruction may be complicated by scarred and immobile tuberosities or by the malunited bone deformity itself. In the setting of scarred tuberosities associated with dysfunctional rotator cuff muscle tendon units, or if adequate balancing the soft tissues cannot be obtained and instability is anticipated, reverse shoulder arthroplasty can be considered as an alternative. In the presence of extra-articular deformity, often it is of benefit to accept some degree of deformity. An attempt to bypass this deformity on the humeral side should be made in order to avoid the need for osteotomy, which has been previously associated with poor outcomes. If the humeral-sided deformity cannot accommodate the available stem, osteotomy or excision of the proximal deformity followed by proximal humeral reconstruction using a proximal humeral allograft are both available options. Reconstruction with the allograft can serve to restore proximal humeral bone stock and provides an allograft subscapularis insertion for later augmentation of the native tendon.

INDICATIONS/CONTRAINDICATIONS

The use of the reverse shoulder prosthesis is becoming more popular for the management of varying shoulder pathologies. The indication to select the use of this prosthesis in the setting of acute trauma is not well established. Evidence supporting its use in acute trauma is scarce at this point. Possible applications, however, can be extrapolated from the outcomes that have been reported in the literature for other entities. The use of reverse shoulder arthroplasty for the management of fracture sequelae may provide a versatile alternative for this complex predicament. Its use in the revision setting for failed hemiarthroplasty performed for fracture has shown promising early results. In this setting, it offers a salvage-type solution for this very complex and often debilitating problem. In the case of severe proximal humeral bone deficiency, augmentation with proximal humeral allograft may improve patient satisfaction.

Acute fracture indications for reverse shoulder arthroplasty include the following:

•

Comminuted four-part proximal humerus fracture in an elderly patient with irreconstructible tuberosities
•

Inadequate social structure to undergo extensive rehabilitation of hemiarthroplasty
•

History of previous failed rotator cuff surgery or severe supraspinatus atrophy on CT scan

Chronic fracture indications for reverse shoulder arthroplasty include the following: