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Humeral Head Height: Getting it Right
Humeral Head Height: Getting it Right Adam C. Schaaf, MD, and Robert H. Bell, MD Total shoulder arthroplasties continue to be implanted at an increasing rate. Both patient function and implant longevity are maximized by the reproduction of the patient’s natural anatomy. One of the more troublesome areas of total shoulder arthroplasty is that of appropriate humeral head positioning. While much attention has been devoted to proper version, equally important is proper head height. We review key concepts and intraoperative evaluation of proper humeral head height. With attention to these principles, excellent clinical results may be obtained. Semin Arthro 19:74-77 © 2008 Elsevier Inc. All rights reserved. KEYWORDS humeral height, shoulder arthroplasty, component positioning
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he number of shoulder arthroplasties performed annually continues to increase with the aging of the population. Recent studies have suggested that the vast majority of these surgeries will be performed by surgeons who perform two or fewer a year.1 To maximize longevity of the implants, pain control, and functional outcomes of the patient, reproduction of the patient’s natural anatomy is critical. In a review of unsatisfactory shoulder arthroplasties by Franka and coworkers,2 component malpositioning and glenohumeral malalignment were found to be the largest technical causes of failure. While shoulder arthroplasty systems have become increasingly modular with various offsets and head sizes, a clear understanding of anatomic variables is crucial to making use of these newer options. With attention to humeral retroversion and inclination, head height, and glenoid positioning, excellent functional results approaching that of hip and knee arthroplasty can be attained.3
Preoperative Assessment Preoperative assessment of the shoulder arthroplasty patient is critical. External rotation must be carefully assessed for contracture of the subscapularis. Careful radiographic assessment of humeral osteophyte formation will assist in planning the level of the humeral osteotomy. All patients are evaluated using a standard shoulder trauma series consisting of a true anteroposterior view of the shoulder, scapular Y, and axillary view. Specific attention is directed to the presence and size of Department of Orthopaedic Surgery, Summa Health System, Akron, OH, USA. Address reprints requests to Adam Schaaf, MD, Department of Orthopaedic Surgery, Summa Health System, 444 North Main Street, Akron, OH 44312. E-mail: [email protected]
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1045-4527/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2007.12.033
humeral osteophytes. While these are most often seen along the inferior aspect of the head, along the metaphyseal flare, osteophytes are often present at the anterior and posterior margins of the articular surface and only seen on an axillary view. Computed tomography scans can help to further define the status of head deformation and the status of head deformation and the amount of glenoid bone loss.
Intraoperative Considerations The patient is prepped and draped with a towel placed between the shoulder blades and in the standard beach-chair position. The head is carefully secured in a neutral position. Through a standard deltopectoral approach, the cephalic vein is identified and carried laterally. The clavipectoral fascia is released bluntly and a self-retaining retractor is placed above the conjoined tendon. The superior third of the pectoralis is released as well as the coracoacromial ligament. The biceps tendon and subscapularis is then identified and the subscapularis and capsule is incised 1.5 cm medial to the biceps tendon. With gentle external rotation applied to the humerus, dissection is carried down the subscapularis and humeral shaft. A key elevator is then used to free the posterior capsule. Care is taken that the osteotomy is not made until 90° of external rotation of the native shoulder can be attained. After adequate and appropriate exposure of the proximal humerus, determination of the true anatomic neck is imperative. Removal of the secondary osteophyte shelf and use of a cutting guide will incorporate an appropriate amount of neck valgus and help to determine the appropriate resection level (Fig 1). To assure proper height for the head resection, the surgeon must visualize the insertion of the rotator cuff and capsule
Humeral head height
75
Figure 3 Complications of too flat or steep humeral osteotomy.
varus and the tuberosity will become overly prominent. Conversely, too flat a cut and the prosthesis will seat overly proud (Fig 3). The goal of a properly placed humeral osteotomy and appropriate humeral sizing is the recreation of the patient’s natural anatomy and soft tissue tension (Fig 4).
Figure 1 Anteroposterior radiograph illustrating proper osteotomy orientation.
Humeral Preparation
superiorly and posteriorly. These attachments will provide further clues as to the anatomic neck location and site for osteotomy. Head resections that are too high will result in a prominent modular replacement head and cuff irritation or too low a prominence of the greater tuberosity and impingement (Fig 2). Careful attention to varus valgus alignment is just as important. Too steep an osteotomy will drop the prosthesis into
With the appropriate humeral cut having been established, and the glenoid cemented into place, modular heads incorporating varying diameters, head heights, and offsets can be utilized to recreate normal rotator cuff tension. Reaming is performed until appropriate cortical contact is obtained. The next step is trialing of various size modular heads. This system employs modular heads that come in varying diameters and head heights. Equally important is the ability to offset the heads to accommodate shaft to head irregularities. These heads incorporate both 4 and 8 mm offsets, allowing one to address nearly any pathology. Once a trial head has been
Figure 2 Complications of too proximal or distal humeral osteotomy.
Figure 4 Recreation of natural anatomy.
A.C. Schaaf and R.H. Bell
76
Figure 5 Assessment of internal rotation to abdomen.
chosen based on dimensions of the resected head, a trial reduction is performed.
Component Trialing It is imperative that the surgeon avoid overstuffing in shoulder arthroplasty or suboptimal results will be encountered. There are five tests that are used intraoperatively to assess proper component size and position. First, internal rotation to the abdomen without significant tension is assessed. Difficulty bringing the arm easily to the abdomen implies posterior capsular tightness and may require a smaller modular head height (Fig 5). Next, in 45° of external rotation, the anterior capsulotomy should be able to be readily reapproximated without excessive tension. If this is not possible, either additional releases of the subscapularis and capsule are needed or a downsizing of the modular head (Fig 6). Next, in 90° of external rotation component stability is assessed. The humeral head may sublux, but should not dislocate. If the humeral head does dislocate, both hu-
Figure 6 Assessment of capsular closure at 45°.
Figure 7 Demonstration of 90° of external rotation without dislocation.
meral version and modular head size need to be checked (Fig 7). Anterior posterior translation is then assessed. The humeral modular head should translate anteriorly, posteriorly, or inferiorly 30 to 40% in each direction. Inability to do so implies the potential for an overstuffed, overtensioned joint and should be avoided (Fig 8). Finally, humeral height is evaluated. Humeral height should be equal to or slightly greater than that of the greater tuberosity. As noted before, prominence of the prosthesis or the tuberosity can, in either case, lead to rotator cuff irritation and failure. A simple test for assuring proper modular head height is to abduct the arm 30 to 40°, at which point the apex of the head and the tuberosity should be equal (Fig 9).
Conclusion As our knowledge of component positioning, sizing, and materials has increased, so too has the survivorship of the total shoulder arthroplasty. Recent studies have reported survivorship of unconstrained shoulder arthroplasty of 85% at 15
Figure 8 Assessment of appropriate anterior–posterior translation.
Humeral head height
77 years.3 With continued attention to replicating normal anatomy and proper soft tissue tensioning, total shoulder arthroplasties will continue to provide patients with both excellent functional results and significant pain relief.
References
Figure 9 Humeral height at or slightly greater than greater tuberosity.
1. Hasan SS, Leith JM, Smith KL, et al: The distribution of shoulder replacement among surgeons and hospitals is significantly different than that of hip or knee replacement. J Shoulder Elbow Surg 12:164169, 2003 2. Franka AK, Lenters TR, Mounce D, et al: The complex characteristics of 282 unsatisfactory shoulder arthroplasties. J Shoulder Elbow Surg 16: 555-562, 2007 3. Torchia ME, Cofield RH, Settergren CR: Total shoulder arthroplasty with the Neer prosthesis: Long-term results. J Shoulder Elbow Surg 6:495505, 1997
T
he number of shoulder arthroplasties performed annually continues to increase with the aging of the population. Recent studies have suggested that the vast majority of these surgeries will be performed by surgeons who perform two or fewer a year.1 To maximize longevity of the implants, pain control, and functional outcomes of the patient, reproduction of the patient’s natural anatomy is critical. In a review of unsatisfactory shoulder arthroplasties by Franka and coworkers,2 component malpositioning and glenohumeral malalignment were found to be the largest technical causes of failure. While shoulder arthroplasty systems have become increasingly modular with various offsets and head sizes, a clear understanding of anatomic variables is crucial to making use of these newer options. With attention to humeral retroversion and inclination, head height, and glenoid positioning, excellent functional results approaching that of hip and knee arthroplasty can be attained.3
Preoperative Assessment Preoperative assessment of the shoulder arthroplasty patient is critical. External rotation must be carefully assessed for contracture of the subscapularis. Careful radiographic assessment of humeral osteophyte formation will assist in planning the level of the humeral osteotomy. All patients are evaluated using a standard shoulder trauma series consisting of a true anteroposterior view of the shoulder, scapular Y, and axillary view. Specific attention is directed to the presence and size of Department of Orthopaedic Surgery, Summa Health System, Akron, OH, USA. Address reprints requests to Adam Schaaf, MD, Department of Orthopaedic Surgery, Summa Health System, 444 North Main Street, Akron, OH 44312. E-mail: [email protected]
74
1045-4527/08/$-see front matter © 2008 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2007.12.033
humeral osteophytes. While these are most often seen along the inferior aspect of the head, along the metaphyseal flare, osteophytes are often present at the anterior and posterior margins of the articular surface and only seen on an axillary view. Computed tomography scans can help to further define the status of head deformation and the status of head deformation and the amount of glenoid bone loss.
Intraoperative Considerations The patient is prepped and draped with a towel placed between the shoulder blades and in the standard beach-chair position. The head is carefully secured in a neutral position. Through a standard deltopectoral approach, the cephalic vein is identified and carried laterally. The clavipectoral fascia is released bluntly and a self-retaining retractor is placed above the conjoined tendon. The superior third of the pectoralis is released as well as the coracoacromial ligament. The biceps tendon and subscapularis is then identified and the subscapularis and capsule is incised 1.5 cm medial to the biceps tendon. With gentle external rotation applied to the humerus, dissection is carried down the subscapularis and humeral shaft. A key elevator is then used to free the posterior capsule. Care is taken that the osteotomy is not made until 90° of external rotation of the native shoulder can be attained. After adequate and appropriate exposure of the proximal humerus, determination of the true anatomic neck is imperative. Removal of the secondary osteophyte shelf and use of a cutting guide will incorporate an appropriate amount of neck valgus and help to determine the appropriate resection level (Fig 1). To assure proper height for the head resection, the surgeon must visualize the insertion of the rotator cuff and capsule
Humeral head height
75
Figure 3 Complications of too flat or steep humeral osteotomy.
varus and the tuberosity will become overly prominent. Conversely, too flat a cut and the prosthesis will seat overly proud (Fig 3). The goal of a properly placed humeral osteotomy and appropriate humeral sizing is the recreation of the patient’s natural anatomy and soft tissue tension (Fig 4).
Figure 1 Anteroposterior radiograph illustrating proper osteotomy orientation.
Humeral Preparation
superiorly and posteriorly. These attachments will provide further clues as to the anatomic neck location and site for osteotomy. Head resections that are too high will result in a prominent modular replacement head and cuff irritation or too low a prominence of the greater tuberosity and impingement (Fig 2). Careful attention to varus valgus alignment is just as important. Too steep an osteotomy will drop the prosthesis into
With the appropriate humeral cut having been established, and the glenoid cemented into place, modular heads incorporating varying diameters, head heights, and offsets can be utilized to recreate normal rotator cuff tension. Reaming is performed until appropriate cortical contact is obtained. The next step is trialing of various size modular heads. This system employs modular heads that come in varying diameters and head heights. Equally important is the ability to offset the heads to accommodate shaft to head irregularities. These heads incorporate both 4 and 8 mm offsets, allowing one to address nearly any pathology. Once a trial head has been
Figure 2 Complications of too proximal or distal humeral osteotomy.
Figure 4 Recreation of natural anatomy.
A.C. Schaaf and R.H. Bell
76
Figure 5 Assessment of internal rotation to abdomen.
chosen based on dimensions of the resected head, a trial reduction is performed.
Component Trialing It is imperative that the surgeon avoid overstuffing in shoulder arthroplasty or suboptimal results will be encountered. There are five tests that are used intraoperatively to assess proper component size and position. First, internal rotation to the abdomen without significant tension is assessed. Difficulty bringing the arm easily to the abdomen implies posterior capsular tightness and may require a smaller modular head height (Fig 5). Next, in 45° of external rotation, the anterior capsulotomy should be able to be readily reapproximated without excessive tension. If this is not possible, either additional releases of the subscapularis and capsule are needed or a downsizing of the modular head (Fig 6). Next, in 90° of external rotation component stability is assessed. The humeral head may sublux, but should not dislocate. If the humeral head does dislocate, both hu-
Figure 6 Assessment of capsular closure at 45°.
Figure 7 Demonstration of 90° of external rotation without dislocation.
meral version and modular head size need to be checked (Fig 7). Anterior posterior translation is then assessed. The humeral modular head should translate anteriorly, posteriorly, or inferiorly 30 to 40% in each direction. Inability to do so implies the potential for an overstuffed, overtensioned joint and should be avoided (Fig 8). Finally, humeral height is evaluated. Humeral height should be equal to or slightly greater than that of the greater tuberosity. As noted before, prominence of the prosthesis or the tuberosity can, in either case, lead to rotator cuff irritation and failure. A simple test for assuring proper modular head height is to abduct the arm 30 to 40°, at which point the apex of the head and the tuberosity should be equal (Fig 9).
Conclusion As our knowledge of component positioning, sizing, and materials has increased, so too has the survivorship of the total shoulder arthroplasty. Recent studies have reported survivorship of unconstrained shoulder arthroplasty of 85% at 15
Figure 8 Assessment of appropriate anterior–posterior translation.
Humeral head height
77 years.3 With continued attention to replicating normal anatomy and proper soft tissue tensioning, total shoulder arthroplasties will continue to provide patients with both excellent functional results and significant pain relief.
References
Figure 9 Humeral height at or slightly greater than greater tuberosity.
1. Hasan SS, Leith JM, Smith KL, et al: The distribution of shoulder replacement among surgeons and hospitals is significantly different than that of hip or knee replacement. J Shoulder Elbow Surg 12:164169, 2003 2. Franka AK, Lenters TR, Mounce D, et al: The complex characteristics of 282 unsatisfactory shoulder arthroplasties. J Shoulder Elbow Surg 16: 555-562, 2007 3. Torchia ME, Cofield RH, Settergren CR: Total shoulder arthroplasty with the Neer prosthesis: Long-term results. J Shoulder Elbow Surg 6:495505, 1997