Arthroplasty in the Neurologically Impaired Shoulder
Alexander R. Graf, MD
Steven I. Grindel, MD
INTRODUCTION
A painless functional shoulder is contingent upon not only the integrity of the articular cartilage but also the strength of the rotator cuff and surrounding musculature that animate the shoulder girdle. Both central and peripheral nervous system disorders can compromise shoulder stability and function through secondary problems such as overload, weakness, spasticity, contracture, and aberrant movement patterns. These problems present unique challenges to shoulder arthroplasty and require a thorough understanding of how glenohumeral anatomy, kinematics, muscle tone, and postoperative demands differ from that of the “normal” shoulder to optimize outcomes (TABLE 47.1). In addition, recognition of the unique psychosocial demands of this population cannot be overstated. While previous studies have shown increased complications following shoulder arthroplasty in patients with neurologically impaired shoulders, the tremendous improvements on quality of life that can result make treating this vulnerable patient population especially worthwhile.
Patient Evaluation
Understanding the patient’s current level of functioning, independence, pain level, and their goals of surgery are all important elements in caring for this complex patient population. It is our experience that these patients often delay surgical intervention until the shoulder pathology is advanced. One reason is fear of further loss of independence during the recovery process from postoperative immobilization. Another is the likelihood of need for postoperative transfer to a skilled nursing facility which is a daunting place, especially for the younger patient.
The examination of the neurologically impaired shoulder should be concentrated on taking an inventory of what the patient has, what they need, and what they can spare. A multidisciplinary approach including surgeon, physical and occupational therapist, social worker, and physiatrist is ideal. Emphasis that arthroplasty can give back something but not always everything helps to set realistic expectations at first meeting and in our experience has been the best strategy.
THE WEIGHT-BEARING SHOULDER
Wheelchair-dependent patients pose several challenges to shoulder arthroplasty. Although they have relatively normal glenohumeral anatomy, the increased functional demand required of the shoulder to propel a wheelchair and for transfers leads to a high incidence of shoulder pathology over time. However, as medical care continues to improve the survival of patients who sustain cerebrovascular accidents (CVAs) or traumatic spinal cord injuries resulting in paraplegia, the prevalence of wheelchair-dependent patients will continue to increase.
Biomechanically, the push phase of wheelchair propulsion in which the arm is extended and internally rotated has been shown to increase vertical force across the shoulder over threefold and posterior force twofold1,2 (FIGURE 47.1). This increased stress over time explains the greater incidence of rotator cuff lesions in wheelchair users as compared with ambulatory individuals (63% vs 15%).3 Shoulder dysfunction in wheelchair users increases in direct correlation with age and duration of wheelchair use and not only limits independence but also can lead to depression over time.4
Previous studies have shown rotator cuff repair to be successful in wheelchair users in the short term but retears are common over time (as high as 40% in some series).5,6,7,8,9 This pattern is echoed in the results of total shoulder arthroplasty (TSA) where rotator cuff failure is a near inevitability over time if the individual continues to bear weight through the shoulder.10,11 This has led some to prefer primary reverse shoulder arthroplasty (RSA) in wheelchair-dependent patients. In the largest series to date, 83% of wheelchair ambulators were satisfied with their RSA; however, early complications (instability, glenoid baseplate loosening), late complications (periprosthetic fracture), and a notching rate of 42% make it far from ideal.12
Special Considerations
Preoperatively, patients are evaluated by a multidisciplinary team. Important elements of the patient’s history include nature and laterality of pain, hand dominance, duration of wheelchair dependence, and previous treatment. Observation of wheelchair propulsion and patient
transfers can provide information on opportunities for postural or wheelchair ergonomic changes that can help alleviate symptoms, especially if noticed early on. Nonsurgical treatment of shoulder pain in wheelchair-dependent patients has previously been well described (TABLE 47.2).8 However, often we have found this patient population to delay care due to fear of losing further independence which can lead to a problem that ultimately is harder to solve. Integrity of the rotator cuff, patient age, and level of demand help guide the shared patient-surgeon decision.
transfers can provide information on opportunities for postural or wheelchair ergonomic changes that can help alleviate symptoms, especially if noticed early on. Nonsurgical treatment of shoulder pain in wheelchair-dependent patients has previously been well described (TABLE 47.2).8 However, often we have found this patient population to delay care due to fear of losing further independence which can lead to a problem that ultimately is harder to solve. Integrity of the rotator cuff, patient age, and level of demand help guide the shared patient-surgeon decision.
TABLE 47.1 Arthroplasty Challenges in the Neurologically Impaired Shoulder | ||||||||||
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 FIGURE 47.1 The propulsion phase of wheelchair ambulation demonstrated above in paraplegic patient secondary to traumatic spinal cord injury is associated with increased stress on the posterosuperior rotator cuff. (Photo courtesy of Brooke Slavens, PhD and Alyssa Schnorenberg, MS, The Mobility Lab at the University of Wisconsin-Milwaukee.) |
Recommendations
In the setting of glenohumeral arthritis with intact rotator cuff, TSA is an option for wheelchair ambulators but is not ideal if the patient is young and plans to continue to use a manual wheelchair. For higher demand patients with an intact rotator cuff, hemiarthroplasty (HA) with or without glenoid resurfacing via ream and run (Chapter 19) improves pain and function and leaves a good salvage option with preserved glenoid bone stock should the patient require revision to RSA (FIGURE 47.2). Important technical considerations include adequate soft tissue release, maintenance of the labrum, avoiding overreaming of the glenoid to preserve subchondral bone, and not overstuffing the joint which can accelerate rotator cuff wear following anatomic TSA.
If the patient is a fall risk and has good bone stock, a stemless humeral component makes for an easier revision in the setting of periprosthetic fracture. An electric wheelchair can also preserve the rotator cuff after shoulder arthroplasty and should be discussed with the patient at the outset to maximize outcome. Magnetic resonance
imaging (MRI) is essential preoperatively to determine the status of the rotator cuff. If there is any clinical or radiographic sign of rotator cuff pathology, RSA is the most reliable option for this population and is our preference for the majority of patients. During RSA, important technical considerations include lateralization to appropriately tension the deltoid, inferior glenosphere placement to avoid notching and impingement, and avoiding superior inclination of the glenosphere for stability.
imaging (MRI) is essential preoperatively to determine the status of the rotator cuff. If there is any clinical or radiographic sign of rotator cuff pathology, RSA is the most reliable option for this population and is our preference for the majority of patients. During RSA, important technical considerations include lateralization to appropriately tension the deltoid, inferior glenosphere placement to avoid notching and impingement, and avoiding superior inclination of the glenosphere for stability.
TABLE 47.2 Strategies for Nonoperative Shoulder Pain Treatment | |||||||||||||||
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 FIGURE 47.2 Rotator cuff failure after total shoulder arthroplasty (A) in wheelchair ambulator with cerebral palsy revised to reverse shoulder arthroplasty (B). |
THE SPASTIC SHOULDER
Spasticity results in increased muscle tone secondary to central neurologic dysfunction. Over time, this increased muscle tone can lead to painful contractures and eventual arthrosis. Although it is very uncommon for patients with spasticity to present for consideration of shoulder arthroplasty, patients with cerebral palsy (CP) as well as those who have survived a traumatic brain injury or CVA represent the majority of patients in this category. In individuals with CP, spasticity most often results in extension, adduction, and internal rotation contractures of the shoulder.13 In addition, altered muscular activity can predispose to recurrent joint subluxation, abnormal joint morphology, and premature arthritis. Previous studies have shown physical therapy, occupational therapy, bracing, botulinum toxin injections, soft tissue releases, and musculotendinous lengthening of spastic muscle units to be effective in correcting the internal rotation deformity prior to the onset of arthritis.14 In the setting of arthritis, both RSA and TSA have been performed with success, albeit in a few small case series with mixed functional results.13,14 Overall, RSA has been associated with better function and fewer complications than TSA, but long-term data are lacking.14
Special Considerations
Preoperative evaluation includes understanding the patient’s symptoms, individual functional goals, and the nature of their spasticity. As successful shoulder arthroplasty is as much a soft tissue operation as anything else, understanding how the aberrant muscle contractions can alter the normal force-couple relationships and soft tissue balance is critical in preventing postoperative glenohumeral instability and early component failure.15
In addition to physical examination, dynamic poly-EMG is recommended to understand which muscle units are spastic both at rest and under voluntary control. For contractures secondary to chronic spasticity and limited passive motion, capsular release as well as fractional lengthening of the contracted muscle units can be performed. For muscles that are spastic during active motion (dynamic spasticity), botulinum toxin can be used to block acetylcholine release and relax muscles in a dose-dependent manner for up to 6 months and can be repeated as necessary. Selective lidocaine blocks can also be used to simulate the effects of botulinum toxin prior to injection to target injections appropriately.
In the normal shoulder, the subscapularis and infraspinatus/teres minor serve as the anterior-posterior force couple. Superior escape is prevented during abduction by the supraspinatus, biceps tendon, and acromial arch. In CP, chronic shoulder extension, adduction, and internal rotation as well as elbow flexion lead to a tight anterior capsule and subscapularis and can lead to a relative lengthening of the posterior cuff elements. Intraoperatively, anterior capsule release with relative lengthening of the subscapularis muscle unit by lesser tubercle osteotomy with medialization as well as posterior capsulorrhaphy can help rebalance the shoulder
during anatomic TSA. The biceps tendon can be tenotomized or tenodesed. Elbow flexion contractures should also be treated to minimize maladaptive shoulder patterns that can lead to instability and early prosthetic failure. However, even despite adequate soft tissue balancing, anatomic TSA remains fraught with complications. Therefore, in the majority of patients, RSA is our first-line option for reconstruction, particularly in patients with long-standing contracture or poorly controlled spasticity, as it has proven itself to be more reliable. Technically, it is important during RSA to not increase offset too much, as this increased tension on an already spastic deltoid can limit function significantly.
during anatomic TSA. The biceps tendon can be tenotomized or tenodesed. Elbow flexion contractures should also be treated to minimize maladaptive shoulder patterns that can lead to instability and early prosthetic failure. However, even despite adequate soft tissue balancing, anatomic TSA remains fraught with complications. Therefore, in the majority of patients, RSA is our first-line option for reconstruction, particularly in patients with long-standing contracture or poorly controlled spasticity, as it has proven itself to be more reliable. Technically, it is important during RSA to not increase offset too much, as this increased tension on an already spastic deltoid can limit function significantly.
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