- Email: [email protected]
Dealing with Posterior Glenoid Wear: A Slippery Slope
Dealing with Posterior Glenoid Wear: A Slippery Slope Ronald V. Gregush, MD, and Leesa M. Galatz, MD Posterior glenoid bone deficiency is frequently encountered among patients undergoing total shoulder arthroplasty. In the majority of cases, posterior wear is managed by maximizing exposure to the glenoid. Other methods such as eccentric reaming or removal of anterior bone with a burr, can change the version enough to allow glenoid component implantation. Occasionally, bone grafting procedures are necessary. Excessive posterior wear can lead to severe retroversion of the implanted glenoid component and possibly subsequent postoperative instability and early loosening. Anteversion of the humeral component to compensate for excessive posterior wear is controversial, but may have some applicability in certain cases. Semin Arthro 16:301-305 © 2005 Elsevier Inc. All rights reserved. KEYWORDS shoulder, arthroplasty, glenoid, bone wear
G
lenoid bone deficiency is a relatively common finding in patients undergoing total shoulder arthroplasty. It is one of the major factors limiting the use of a glenoid component. Management presents a technical challenge to the treating surgeon, as insertion of a glenoid is often difficult for many without bone deficiency. Preferential posterior wear of the glenoid is the rule rather than the exception in osteoarthritis, and is frequently encountered in this patient population.1,2 Posterior glenoid wear is commonly associated with a tight anterior capsule, a redundant posterior capsule, and posterior subluxation of the humeral head in severe cases. Posterior glenoid bone deficiency and these associated soft tissue imbalance problems must be addressed before implantation of the glenoid component during total shoulder arthroplasty to be successful and insure its longevity. Excessive retroversion of the glenoid component has been associated with postoperative posterior shoulder instability2-4 and glenoid loosening.5 Normal glenoid version has been reported to be between 3 degrees of retroversion and 2 degrees of anteversion.6-8 The limits of what is considered acceptable glenoid retroversion in total shoulder arthroplasty have not been well-established. Options for addressing posterior glenoid wear vary in tech-
Department of Orthopaedic Surgery, Washington University School of Medicine, at Barnes-Jewish Hospital, St. Louis, MO. Address reprint requests to Leesa M. Galatz, MD, Washington University School of Medicine, Department of Orthopaedic Surgery, 660 South Euclid, Campus Box 8233, St. Louis, MO 63110. E-mail: [email protected]
1045-4527/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2005.10.023
nical difficulty and depend on the extent of bone loss. A thorough preoperative evaluation including adequate radiographic studies is critical for preoperative planning. In the majority of patients, eccentric reaming and maximizing glenoid exposure are enough to allow safe glenoid implantation. In more severe cases, bone graft may be required.
Classification Walch and co-workers developed a classification system for glenoid wear patterns based on the morphology of the glenoid in a population of patients with primary glenohumeral osteoarthritis.9 The morphology of the glenoid was evaluated using preoperative computed tomography (CT) scans. Three general patterns of glenoid morphology were elucidated. A type A glenoid wear pattern is characterized by a centered humeral head with minor (type A1) or major (type A2) symmetric, central erosion of the glenoid. The majority of patients (59%) fell into this category. Type B glenoid wear is characterized by a posteriorly subluxated humeral head with asymmetric wear of the posterior aspect of the glenoid. Type B1 glenoid wear has narrowing of the posterior joint space, subchondral sclerosis, and osteophyte formation. Type B2 glenoid wear shows more advanced posterior wear resulting in a biconcave shape of the glenoid. Thirty-two percent of patients were noted to have a type B glenoid. Type C glenoid wear is characterized by a glenoid retroversion of more than 25 degrees, regardless of the amount of erosion. A type C glenoid is felt to be dysplastic in origin and the humeral head is usually well centered or only slightly subluxated posteri301
R.V. Gregush and L.M. Galatz
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ation of the humeral head before shoulder arthroplasty.10 A number of other authors have recommended CT scans to evaluate glenoid morphology and glenoid erosion.6,7,9,11,12 A recent study evaluating the use of CT scans versus plain radiographs for the assessment of glenoid version showed a difference of 6.5 degrees between the glenoid version measured on CT scan versus that measured on conventional radiographs. The glenoid retroversion was overestimated on plain radiographs 86% of the time.12 MRI may be a helpful adjunct in certain patient populations. MRI provides excellent visualization of the soft tissues surrounding the shoulder, such as the rotator cuff, as well as good visualization of the glenoid. The authors recommend routine use of CT or MRI as a preoperative test in addition to X-rays for preoperative planning purposes. These investigations also help assess the status of the rotator cuff, which may be useful information, as well.
Treatment Options
Figure 1 A true anteroposterior (A) and axillary (B) view of a shoulder demonstrate typical biconcave glenoid with posterior wear in a 49-year-old male.
orly. Only 9% of their patient population were classified as having a type C glenoid.9
Preoperative Planning The diagnosis of shoulder arthritis is commonly made based on plain radiographs alone. Radiographs show a narrowed or absent joint space, osteophyte formation (especially along the inferior anatomic neck of the humerus), and often preferential posterior wear of the glenoid (Fig. 1A, B). Glenoid version is difficult to assess using x-rays alone, even with a good axillary view (Fig. 2A–C). The version of the glenoid changes from the superior to the inferior aspect, and this is difficult to assess radiographically. An magnetic resonance imaging (MRI) or a CT scan allows a more three-dimensional assessment of the version with multiple cuts. Glenoid bone stock and size of the vault are also revealed. Neer initially recommended an axillary radiograph to assess the morphology of the glenoid and the posterior sublux-
The approach to management of posterior glenoid wear depends on the degree of wear and the morphology of the remaining glenoid. Ultimately, excessive wear can potentially lead to poor insertion of the glenoid component or posterior instability of the joint. Options include asymmetric reaming of the high anterior side of the glenoid and glenoid bone grafting. Some recommend compensatory anteversion of the humeral component to prevent posterior instability, but this is controversial. Each of these options will be discussed individually in detail. Excessive posterior cement build up is not recommended for filling of the posterior glenoid defect. Cement augmentation of the glenoid has been associated with high rates of glenoid component loosening and failure.13 This loosening can result in fracture of the peg or keel of the glenoid component.
Glenoid Exposure Optimal exposure of the glenoid before instrumentation makes glenoid implantation much easier and, in the majority of cases, this is adequate for managing mild to moderate posterior wear (Fig. 3A, B). Posterior wear and its associated subluxation results in contracture of the anterior soft tissues. The tight anterior structures limit external rotation and hinder exposure and should be released as a routine part of the procedure. The subscapularis is released either by a tenotomy or lesser tuberosity osteotomy. The rotator interval should be completely released along the superior edge of the glenoid, all the way to the glenoid rim. The coracohumeral ligament is often hypertrophied and is released in this step. The attachment of the anterior capsule to the anterior glenoid rim is released. The middle glenohumeral ligament is incise. Some recommend excising the anterior capsule at this point by separating it from the subscapularis. We prefer to completely release the capsule and leave it along the deep surface of the subscapularis, as the subscapularis is often attenuated and thinned after excision. The inferior glenohumeral ligament complex
Posterior glenoid wear
303
Figure 2 The extent of posterior wear can not always be determined on plain radiographs, especially on an anteroposterior view (A). It can also be difficult with just an axillary view (B). Often a CT scan helps determine the extent of wear, and is recommended as a preoperative assessment before shoulder arthroplasty (C).
is then released. We use a wet sponge or narrow, deep right angle retractor to protect the axillary nerve, which is routinely palpated to confirm its location in proximity to the capsule being released. The inferior capsule is also released from the inferior neck of the humerus as the head is dislo-
cated from the joint. These releases allow the head to sublux posteriorly with retraction, maximizing visualization of the glenoid for operative instrumentation. The humeral osteotomy can be enlarged slightly to increase exposure. A few mm of extra bone can be removed
Figure 3 An intraoperative view of the patient with moderate, typical posterior wear from Figure 2. Circumferential releases and excision of the inferior capsule allow adequate exposure of the retroverted glenoid (A). This glenoid was eccentrically reamed and the component placed in slight retroversion (B). (Color version of figure is available online.)
304 (2-3 mm) in the correct plane. One risk is injury to the rotator cuff, and this cut should not be made at the expense of the rotator cuff!
Eccentric Reaming In cases of mild to moderate posterior glenoid wear (⬍2530%), the high anterior side of the glenoid can be eccentrically reamed. Preferentially removing more anterior glenoid bone can be used to restore normal glenoid version.13,14 Asymmetric reaming will, however, necessarily medialize the glenoid component to some degree and care must be taken not to remove too much bone as this may result in excessive medialization of the component or inadequate bone stock for implantation of the glenoid component. Alternatively, the surgeon can use a burr to remove some anterior glenoid bone. Regardless of the method used, subchondral bone is exposed. The long term effect of losing hard subchondral bone on the longevity of the glenoid component is unknown. In cases of severe posterior glenoid bone deficiency, other techniques, such as bone grafting, must be utilized.
Compensatory Anteversion of the Humeral Component Adjusting the version of the humeral component to compensate for posterior glenoid bone loss resulting in potential instability has been described by a number of authors.3,4,10,15 The humeral component is placed in slightly less retroversion than usual to compensate for the increased retroversion of the glenoid component. The idea is to increase surface contact area between the humeral head and glenoid before dislocation occurs. Its efficacy is controversial. A recent study by Spencer and coworkers suggests that the biomechanical effect of decreased retroversion may be minimal.16 In a cadaveric study, a glenoid component was placed in 15 degrees of retroversion. Humeral components were inserted in two different versions: anatomic version and 15 degrees of anteversion relative to anatomic version. They tested the peak load and energy required to translate the humeral head posteriorly one-half the width of the glenoid in three different rotational positions of the humerus. They found no significant differences between the constructs using two different versions. These results suggest that anteverting the humeral component may not improve stability when implanting a retroverted glenoid. In the clinical scenario however, the posterior capsule is patulous and loose compared to the normal cadavers used in the study. This may make a difference clinically in the efficacy of this technique. More study is needed to answer this question.
Glenoid Bone-Grafting In rare cases of severe posterior glenoid bone deficiency, bone-grafting can be considered. Bone-grafting of the glenoid for posterior glenoid wear is a technically demanding procedure. It has been advocated by a number of authors to ad-
R.V. Gregush and L.M. Galatz dress severe cases of posterior glenoid bone erosion or dysplasia.10, 17-19 The long-term results of this procedure have been variable. No absolute indications for posterior glenoid bone graft have been established. Many authors have offered some guidelines. Friedman and co-workers recommended performing glenoid augmentation when there is ⬎15 degrees of glenoid retroversion based on computerized tomography scan.6 Sperling and Cofield recommend bone graft when there is greater than 5 mm of bone loss in shoulders with postcapsulorraphy arthritis.20 Hill and Norris used posterior bone graft when reaming would leave less than 1 cm of glenoid remaining.17 Others use graft when alignment can not be restored to within 15 degrees of normal with less than 1 cm of reaming.10,19 Neer initially reported very positive results on 19 patients who underwent glenoid bone grafting with internal fixation at the time of total shoulder arthroplasty. At an average follow-up of 4.4 years, 16 patients achieved an excellent result, one patient had a satisfactory result, and two patients achieved the limited goals that were desired preoperatively. No patient had an unsatisfactory result. Radiographically, 13 patients had no visible lucent line around the glenoid and six patients had a lucent line that measured ⬍1 mm in width. No patients had clinical evidence of loosening and no patients required reoperation. All bone grafts appeared to heal.10 Subsequent studies on the long-term results of glenoid bone-grafting have reported more mixed results. Steinmann and Cofield reported results of 28 patients with glenoid bone grafting for segmental glenoid wear. At an average follow-up of 5.3 years, 13 shoulders were rated as excellent, 10 were rated as satisfactory, and five were rated as unsatisfactory. Two patients had symptomatic glenoid loosening, two patients required reoperation for instability, and one patient had persistent pain. All bone grafts were healed at final follow-up. On radiographic assessment, 13 glenoid components had no surrounding radiolucency, 11 had incomplete lucencies (three of which were ⬎1.5 mm in width), and four had complete lucencies (three of which were ⬎1.5 mm in width). Of the patients with incomplete or complete lucency surrounding the glenoid component, only two were symptomatic.19 Hill and Norris evaluated 17 patients that underwent bone grafting of the glenoid for glenoid bone deficiency. All shoulders had some form of instability preoperatively. Bone from either the resected humeral head or from the iliac crest was used as autologous graft. At the time of final follow-up, five patients had undergone revision surgery; four required revision within 2 years of the index procedure. Average follow-up on the 13 patients who did not require revision surgery within 2 years of the procedure was 70 months. Three shoulders had an excellent result, six shoulders were satisfactory, and eight shoulders were unsatisfactory. In three patients, the bone graft failed, either by nonunion, dissolution, or shift. All failures were associated with symptomatic loosening of the glenoid component.17
Posterior glenoid wear
Summary Posterior glenoid bone deficiency is a frequently encountered problem in total shoulder arthroplasty. Asymmetric wear of the glenoid must be addressed to avoid implanting the glenoid in an excessively retroverted position. Treatment options include eccentric reaming of the glenoid to restore normal version, implanting the glenoid with mild retroversion and compensating with relative anteversion of the humeral component, or bone-grafting of the region of glenoid bone deficiency. Bone-grafting of the glenoid is a technically demanding procedure and is only necessary for the most severe cases of posterior glenoid bone deficiency.
References 1. Neer CS 2nd: Replacement arthroplasty for glenohumeral osteoarthritis. J Bone Joint Surg Am 56:1-13, 1974 2. Neer CS 2nd, Watson KC, Stanton FJ: Recent experience in total shoulder replacement. J Bone Joint Surg Am 64:319-337, 1982 3. Cofield RH, Edgerton BC: Total shoulder arthroplasty: Complications and revision surgery. Instr Course Lect 39:449-462, 1990 4. Moeckel BH, Altchek DW, Warren RF, et al: Instability of the shoulder after arthroplasty. J Bone Joint Surg Am 75:492-497, 1993 5. Hopkins AR, Hansen UN, Amis AA, et al: The effects of glenoid component alignment variations on cement mantle stresses in total shoulder arthroplasty. J Shoulder Elbow Surg 13:668-675, 2004 6. Friedman RJ, Hawthorne KB, Genez B: Glenoid augmentation for total shoulder arthroplasty. Orthop Trans 16:1992 7. Mullaji AB, Beddow FH, Lamb GH: CT measurement of glenoid erosion in arthritis. J Bone Joint Surg Br 76:384-388, 1994
305 8. Randelli M, Gambrioli OL: Glenohumeral osteometry by computed tomography in normal and unstable shoulders. Clin Orthop Relat Res 208:151-156, 1986 9. Walch G, et al: Morphologic study of the glenoid in primary glenohumeral osteoarthritis. J Arthroplasty 14:756-760, 1999 10. Neer CS 2nd, Morrison DS: Glenoid bone-grafting in total shoulder arthroplasty. J Bone Joint Surg Am 70:1154-1162, 1988 11. Green A, Norris TR: Imaging techniques for glenohumeral arthritis and glenohumeral arthroplasty. Clin Orthop Relat Res 307:7-17, 1994 12. Nyfeller RW, Jost B, Pfirrmann CW, et al. Measurement of glenoid version: Conventional radiographs versus computed tomography scans. J Shoulder Elbow Surg 12:493-496, 2003 13. Rodowsky MW, Weinstein DM, Pollock RG, et al: On the rarity of glenoid component failure. J Shoulder Elbow Surg 4:S13–S14, 1995 14. Kelly JD Jr, Norris TR: Decision making in glenohumeral arthroplasty. J Arthroplasty 18:75-82, 2003 15. Wirth MA, Rockwood CA Jr: Complications of shoulder arthroplasty. Clin Orthop Relat Res 307:47-69, 1994 16. Spencer EE Jr, Valdevit A, Kambic H, et al: The effect of humeral component anteversion on shoulder stability with glenoid component retroversion. J Bone Joint Surg Am 87:808-814, 2005 17. Hill JM, Norris TR: Long-term results of total shoulder arthroplasty following bone-grafting of the glenoid. J Bone Joint Surg Am 83-A:877883, 2001 18. Sperling JW, Cofield RH, Steinmann SP: Shoulder arthroplasty for osteoarthritis secondary to glenoid dysplasia. J Bone Joint Surg Am 84A:541-546, 2002 19. Steinmann SP, Cofield RH: Bone grafting for glenoid deficiency in total shoulder replacement. J Shoulder Elbow Surg 9:361-367, 2000 20. Sperling J, Cofield RH: Postcapsulorrhaphy arthroplasty in Williams GR Jr, Yamaguchi K, Ramsey ML, Galatz LM (eds): Shoulder and Elbow Arthroplasty. Philadelphia, PA, Lippincott Williams & Wilkins, 2004, pp 131-144
G
lenoid bone deficiency is a relatively common finding in patients undergoing total shoulder arthroplasty. It is one of the major factors limiting the use of a glenoid component. Management presents a technical challenge to the treating surgeon, as insertion of a glenoid is often difficult for many without bone deficiency. Preferential posterior wear of the glenoid is the rule rather than the exception in osteoarthritis, and is frequently encountered in this patient population.1,2 Posterior glenoid wear is commonly associated with a tight anterior capsule, a redundant posterior capsule, and posterior subluxation of the humeral head in severe cases. Posterior glenoid bone deficiency and these associated soft tissue imbalance problems must be addressed before implantation of the glenoid component during total shoulder arthroplasty to be successful and insure its longevity. Excessive retroversion of the glenoid component has been associated with postoperative posterior shoulder instability2-4 and glenoid loosening.5 Normal glenoid version has been reported to be between 3 degrees of retroversion and 2 degrees of anteversion.6-8 The limits of what is considered acceptable glenoid retroversion in total shoulder arthroplasty have not been well-established. Options for addressing posterior glenoid wear vary in tech-
Department of Orthopaedic Surgery, Washington University School of Medicine, at Barnes-Jewish Hospital, St. Louis, MO. Address reprint requests to Leesa M. Galatz, MD, Washington University School of Medicine, Department of Orthopaedic Surgery, 660 South Euclid, Campus Box 8233, St. Louis, MO 63110. E-mail: [email protected]
1045-4527/05/$-see front matter © 2005 Elsevier Inc. All rights reserved. doi:10.1053/j.sart.2005.10.023
nical difficulty and depend on the extent of bone loss. A thorough preoperative evaluation including adequate radiographic studies is critical for preoperative planning. In the majority of patients, eccentric reaming and maximizing glenoid exposure are enough to allow safe glenoid implantation. In more severe cases, bone graft may be required.
Classification Walch and co-workers developed a classification system for glenoid wear patterns based on the morphology of the glenoid in a population of patients with primary glenohumeral osteoarthritis.9 The morphology of the glenoid was evaluated using preoperative computed tomography (CT) scans. Three general patterns of glenoid morphology were elucidated. A type A glenoid wear pattern is characterized by a centered humeral head with minor (type A1) or major (type A2) symmetric, central erosion of the glenoid. The majority of patients (59%) fell into this category. Type B glenoid wear is characterized by a posteriorly subluxated humeral head with asymmetric wear of the posterior aspect of the glenoid. Type B1 glenoid wear has narrowing of the posterior joint space, subchondral sclerosis, and osteophyte formation. Type B2 glenoid wear shows more advanced posterior wear resulting in a biconcave shape of the glenoid. Thirty-two percent of patients were noted to have a type B glenoid. Type C glenoid wear is characterized by a glenoid retroversion of more than 25 degrees, regardless of the amount of erosion. A type C glenoid is felt to be dysplastic in origin and the humeral head is usually well centered or only slightly subluxated posteri301
R.V. Gregush and L.M. Galatz
302
ation of the humeral head before shoulder arthroplasty.10 A number of other authors have recommended CT scans to evaluate glenoid morphology and glenoid erosion.6,7,9,11,12 A recent study evaluating the use of CT scans versus plain radiographs for the assessment of glenoid version showed a difference of 6.5 degrees between the glenoid version measured on CT scan versus that measured on conventional radiographs. The glenoid retroversion was overestimated on plain radiographs 86% of the time.12 MRI may be a helpful adjunct in certain patient populations. MRI provides excellent visualization of the soft tissues surrounding the shoulder, such as the rotator cuff, as well as good visualization of the glenoid. The authors recommend routine use of CT or MRI as a preoperative test in addition to X-rays for preoperative planning purposes. These investigations also help assess the status of the rotator cuff, which may be useful information, as well.
Treatment Options
Figure 1 A true anteroposterior (A) and axillary (B) view of a shoulder demonstrate typical biconcave glenoid with posterior wear in a 49-year-old male.
orly. Only 9% of their patient population were classified as having a type C glenoid.9
Preoperative Planning The diagnosis of shoulder arthritis is commonly made based on plain radiographs alone. Radiographs show a narrowed or absent joint space, osteophyte formation (especially along the inferior anatomic neck of the humerus), and often preferential posterior wear of the glenoid (Fig. 1A, B). Glenoid version is difficult to assess using x-rays alone, even with a good axillary view (Fig. 2A–C). The version of the glenoid changes from the superior to the inferior aspect, and this is difficult to assess radiographically. An magnetic resonance imaging (MRI) or a CT scan allows a more three-dimensional assessment of the version with multiple cuts. Glenoid bone stock and size of the vault are also revealed. Neer initially recommended an axillary radiograph to assess the morphology of the glenoid and the posterior sublux-
The approach to management of posterior glenoid wear depends on the degree of wear and the morphology of the remaining glenoid. Ultimately, excessive wear can potentially lead to poor insertion of the glenoid component or posterior instability of the joint. Options include asymmetric reaming of the high anterior side of the glenoid and glenoid bone grafting. Some recommend compensatory anteversion of the humeral component to prevent posterior instability, but this is controversial. Each of these options will be discussed individually in detail. Excessive posterior cement build up is not recommended for filling of the posterior glenoid defect. Cement augmentation of the glenoid has been associated with high rates of glenoid component loosening and failure.13 This loosening can result in fracture of the peg or keel of the glenoid component.
Glenoid Exposure Optimal exposure of the glenoid before instrumentation makes glenoid implantation much easier and, in the majority of cases, this is adequate for managing mild to moderate posterior wear (Fig. 3A, B). Posterior wear and its associated subluxation results in contracture of the anterior soft tissues. The tight anterior structures limit external rotation and hinder exposure and should be released as a routine part of the procedure. The subscapularis is released either by a tenotomy or lesser tuberosity osteotomy. The rotator interval should be completely released along the superior edge of the glenoid, all the way to the glenoid rim. The coracohumeral ligament is often hypertrophied and is released in this step. The attachment of the anterior capsule to the anterior glenoid rim is released. The middle glenohumeral ligament is incise. Some recommend excising the anterior capsule at this point by separating it from the subscapularis. We prefer to completely release the capsule and leave it along the deep surface of the subscapularis, as the subscapularis is often attenuated and thinned after excision. The inferior glenohumeral ligament complex
Posterior glenoid wear
303
Figure 2 The extent of posterior wear can not always be determined on plain radiographs, especially on an anteroposterior view (A). It can also be difficult with just an axillary view (B). Often a CT scan helps determine the extent of wear, and is recommended as a preoperative assessment before shoulder arthroplasty (C).
is then released. We use a wet sponge or narrow, deep right angle retractor to protect the axillary nerve, which is routinely palpated to confirm its location in proximity to the capsule being released. The inferior capsule is also released from the inferior neck of the humerus as the head is dislo-
cated from the joint. These releases allow the head to sublux posteriorly with retraction, maximizing visualization of the glenoid for operative instrumentation. The humeral osteotomy can be enlarged slightly to increase exposure. A few mm of extra bone can be removed
Figure 3 An intraoperative view of the patient with moderate, typical posterior wear from Figure 2. Circumferential releases and excision of the inferior capsule allow adequate exposure of the retroverted glenoid (A). This glenoid was eccentrically reamed and the component placed in slight retroversion (B). (Color version of figure is available online.)
304 (2-3 mm) in the correct plane. One risk is injury to the rotator cuff, and this cut should not be made at the expense of the rotator cuff!
Eccentric Reaming In cases of mild to moderate posterior glenoid wear (⬍2530%), the high anterior side of the glenoid can be eccentrically reamed. Preferentially removing more anterior glenoid bone can be used to restore normal glenoid version.13,14 Asymmetric reaming will, however, necessarily medialize the glenoid component to some degree and care must be taken not to remove too much bone as this may result in excessive medialization of the component or inadequate bone stock for implantation of the glenoid component. Alternatively, the surgeon can use a burr to remove some anterior glenoid bone. Regardless of the method used, subchondral bone is exposed. The long term effect of losing hard subchondral bone on the longevity of the glenoid component is unknown. In cases of severe posterior glenoid bone deficiency, other techniques, such as bone grafting, must be utilized.
Compensatory Anteversion of the Humeral Component Adjusting the version of the humeral component to compensate for posterior glenoid bone loss resulting in potential instability has been described by a number of authors.3,4,10,15 The humeral component is placed in slightly less retroversion than usual to compensate for the increased retroversion of the glenoid component. The idea is to increase surface contact area between the humeral head and glenoid before dislocation occurs. Its efficacy is controversial. A recent study by Spencer and coworkers suggests that the biomechanical effect of decreased retroversion may be minimal.16 In a cadaveric study, a glenoid component was placed in 15 degrees of retroversion. Humeral components were inserted in two different versions: anatomic version and 15 degrees of anteversion relative to anatomic version. They tested the peak load and energy required to translate the humeral head posteriorly one-half the width of the glenoid in three different rotational positions of the humerus. They found no significant differences between the constructs using two different versions. These results suggest that anteverting the humeral component may not improve stability when implanting a retroverted glenoid. In the clinical scenario however, the posterior capsule is patulous and loose compared to the normal cadavers used in the study. This may make a difference clinically in the efficacy of this technique. More study is needed to answer this question.
Glenoid Bone-Grafting In rare cases of severe posterior glenoid bone deficiency, bone-grafting can be considered. Bone-grafting of the glenoid for posterior glenoid wear is a technically demanding procedure. It has been advocated by a number of authors to ad-
R.V. Gregush and L.M. Galatz dress severe cases of posterior glenoid bone erosion or dysplasia.10, 17-19 The long-term results of this procedure have been variable. No absolute indications for posterior glenoid bone graft have been established. Many authors have offered some guidelines. Friedman and co-workers recommended performing glenoid augmentation when there is ⬎15 degrees of glenoid retroversion based on computerized tomography scan.6 Sperling and Cofield recommend bone graft when there is greater than 5 mm of bone loss in shoulders with postcapsulorraphy arthritis.20 Hill and Norris used posterior bone graft when reaming would leave less than 1 cm of glenoid remaining.17 Others use graft when alignment can not be restored to within 15 degrees of normal with less than 1 cm of reaming.10,19 Neer initially reported very positive results on 19 patients who underwent glenoid bone grafting with internal fixation at the time of total shoulder arthroplasty. At an average follow-up of 4.4 years, 16 patients achieved an excellent result, one patient had a satisfactory result, and two patients achieved the limited goals that were desired preoperatively. No patient had an unsatisfactory result. Radiographically, 13 patients had no visible lucent line around the glenoid and six patients had a lucent line that measured ⬍1 mm in width. No patients had clinical evidence of loosening and no patients required reoperation. All bone grafts appeared to heal.10 Subsequent studies on the long-term results of glenoid bone-grafting have reported more mixed results. Steinmann and Cofield reported results of 28 patients with glenoid bone grafting for segmental glenoid wear. At an average follow-up of 5.3 years, 13 shoulders were rated as excellent, 10 were rated as satisfactory, and five were rated as unsatisfactory. Two patients had symptomatic glenoid loosening, two patients required reoperation for instability, and one patient had persistent pain. All bone grafts were healed at final follow-up. On radiographic assessment, 13 glenoid components had no surrounding radiolucency, 11 had incomplete lucencies (three of which were ⬎1.5 mm in width), and four had complete lucencies (three of which were ⬎1.5 mm in width). Of the patients with incomplete or complete lucency surrounding the glenoid component, only two were symptomatic.19 Hill and Norris evaluated 17 patients that underwent bone grafting of the glenoid for glenoid bone deficiency. All shoulders had some form of instability preoperatively. Bone from either the resected humeral head or from the iliac crest was used as autologous graft. At the time of final follow-up, five patients had undergone revision surgery; four required revision within 2 years of the index procedure. Average follow-up on the 13 patients who did not require revision surgery within 2 years of the procedure was 70 months. Three shoulders had an excellent result, six shoulders were satisfactory, and eight shoulders were unsatisfactory. In three patients, the bone graft failed, either by nonunion, dissolution, or shift. All failures were associated with symptomatic loosening of the glenoid component.17
Posterior glenoid wear
Summary Posterior glenoid bone deficiency is a frequently encountered problem in total shoulder arthroplasty. Asymmetric wear of the glenoid must be addressed to avoid implanting the glenoid in an excessively retroverted position. Treatment options include eccentric reaming of the glenoid to restore normal version, implanting the glenoid with mild retroversion and compensating with relative anteversion of the humeral component, or bone-grafting of the region of glenoid bone deficiency. Bone-grafting of the glenoid is a technically demanding procedure and is only necessary for the most severe cases of posterior glenoid bone deficiency.
References 1. Neer CS 2nd: Replacement arthroplasty for glenohumeral osteoarthritis. J Bone Joint Surg Am 56:1-13, 1974 2. Neer CS 2nd, Watson KC, Stanton FJ: Recent experience in total shoulder replacement. J Bone Joint Surg Am 64:319-337, 1982 3. Cofield RH, Edgerton BC: Total shoulder arthroplasty: Complications and revision surgery. Instr Course Lect 39:449-462, 1990 4. Moeckel BH, Altchek DW, Warren RF, et al: Instability of the shoulder after arthroplasty. J Bone Joint Surg Am 75:492-497, 1993 5. Hopkins AR, Hansen UN, Amis AA, et al: The effects of glenoid component alignment variations on cement mantle stresses in total shoulder arthroplasty. J Shoulder Elbow Surg 13:668-675, 2004 6. Friedman RJ, Hawthorne KB, Genez B: Glenoid augmentation for total shoulder arthroplasty. Orthop Trans 16:1992 7. Mullaji AB, Beddow FH, Lamb GH: CT measurement of glenoid erosion in arthritis. J Bone Joint Surg Br 76:384-388, 1994
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