Instability of the Shoulder after Arthroplasty*

Transcription

1 Copyright 1993 by The Journal ofbone and Joint Surgery, Incorporated Instability of the Shoulder after Arthroplasty* BY BRUCE H. MOECKEL. M.D.t. DAVID w. ALTCHEK. M.D3. RUSSELL F. WARREN. M.D4, THOMAS L. wick1ewicz. M.D 4. AND DAVID M. DINES. M.D4. NEW YORK. N.Y. Investigation performed at The Shoulder Service, The Hospitalfor Special Surgery, New York City ABSTRACT: A replacement arthroplasty was performed in 236 shoulders at The Hospital for Special Surgery from 1984 through Ten patients (eight women and two men) from that group were identified as having instability of the shoulder at the time of follow-up, and the results for these patients were reviewed retrospectively. The ages of the patients ranged from fifty-six to seventy-nine years. The instability was anterior in seven of the patients and posterior in three. The anterior instability was caused by a rupture of the repaired subscapularis tendon. The operative treatment of the anterior instability consisted of mobilization and repair of the tendon, but three of the seven patients continued to have instability. A static stabilizer, consisting of an allograft of Achilles tendon, was inserted in these three patients, and the result was a success. The etiology of the posterior instability (three patients) was multifactorial. Treatment consisted of correction of any soft-tissue imbalance and revision of the prosthetic components as necessary. All ten patients were followed clinically and radiographically for at least two years. All of the patients had some loss of motion of the shoulder as compared with the motion before the dislocation. There were no neurovascular complications, problems related to the allografts, or any other complications. We concluded that proper balancing of the soft tissues and positioning of the prosthetic components are essential to a successful arthroplasty of the shoulder. The postoperative rehabilitation should include a physical therapy program in which the range of motion of the arm that was achieved in the operating room is not exceeded. Early recognition and treatment of tendon disruption is important when acute injuries are be- *One or more of the authors has received or will receive benefits for personal or professional use from a commercial party related directly or indirectly to the subject of this article. In addition, benefits have been or will be directed to a research fund, foundation, educational institution. or other non-profit organization with which one or more of the authors is associated. No funds were received in support of this study. tmiddlesex Orthopedics, 520 Saybrook Road, Suite N 203, Middletown, Connecticut The Hospital for Special Surgery. 535 East 70th Street, New York.N.Y. 1(5)21. ing treated. Instability after an arthroplasty was treated successfully with reconstruction of the soft-tissue envelope or revision of the prosthetic components, or both, and sometimes with the use of an allograft to replace deficient soft tissues. Total replacement of the shoulder has proved to be a successful procedure with durable results 37. Relief of pain is predictable, having been reported in 90 to 95 per cent of patients4. The range of active motion of the shoulder usually is about two-thirds of normal after the rehabilitation program has been completed. A rarely addressed, but important, complication of total replacement is instability of the shoulder, the prevalence of which has ranged from 0 to 18.2 per cent in patients in whom an unconstrained implant was used4. Neer et al.7 reported four dislocations and four subluxations after 194 total shoulder replacements. In six of their patients, the instability resolved with nonoperative treatment. Only two of the patients had a revision procedure. Anterior instability has most often been attributed to disruption of the repaired subscapularis and capsule. Cofield and Edgerton4 said that this lesion was difficult to treat, but they did not provide details concerning their methods of management or salvage. Posterior instability is less common and has usually been attributed to excessive retroversion of either the humeral or the glenoid component. The recommended treatment includes a decrease in the amount of humeral retroversion, and augmentation of the posterior part of the glenoid with bone grafts to decrease its retroversion. Because the literature contains so little information on instability as a complication of total shoulder replacement, we undertook the present study. We identified ten patients who needed operative management because instability of the shoulder had developed after a replacement with an unconstrained total shoulder prosthesis. We describe the findings and the results of treatment in these patients. Materials and Methods We reviewed the records of all 236 patients who had had a total shoulder replacement at The Hospital for Special Surgery from 1984 through Anterior or posterior instability of the shoulder had developed in 492 THE JOURNAL OF BONE AND JOINT SURGERY

2 1NSTABILITY OF THE SHOULDER AFTER ARTHROPLASTY 493 TABLE I DATA ON THE PATIENTS Case Time from Reason for Type of Replace- Dura- Result Type of Result of Sex, Total Shoulder Initial ment to tion of of First Second Second Age Replacement Prosthesis* Revisiont Follow-up Revision Revisions Revisiont (Yrs.) (Wks.) (Mos) Ant. instabil. 1 F. 59 Osteoarth. Biomod Sublux. Allograft Stabil. 2 F. 64 Osteoarth. Biomod Sublux. Allograft Stabil. 3 M. 79 Cuff-tear arthropathy Neer Stabil. 4 F, 76 Osteoarth. Biomod Stabil. 5 F. 71 Post-traumat. osteoarth. Bioniod Stahil. 6 F, 56 Systemic lupus eryth. Biomod. 6 36* Disloe. Allograft Stabil. 7 F, 67 Post-traumat. osteoarth. Custommade 1 51 Stabil. Post. instabil. 8 F, 64 Osteoarth. Biomod Sublux. Resect. arthroplasty 9 M, 60 Osteoarth. Biomod Stahil. 10 F, 72 Rheumat. arth. Neer II 6 24 Stabil. Considering revision *The Biomodular prosthesis is manufactured by Biomet (Warsaw, Indiana): the Neer-Il prosthesis. by Kirsehner Medical (Timonium. Maryland): and the custom-made prosthesis, by the Biomechanies Department at The Hospital for Special Surgery (New York. N.Y.). tthe time from the total shoulder replacement to the initial operative treatment of the instability. lrevision for recurrent instability after the initial treatment for the instability failed. Duration of follow-up after the second revision. ten of those patients, all of whom had been managed with insertion of an unconstrained prosthesis. (Patients who had an isolated superior subluxation due to deficiency of the rotator cuff were excluded from the study.) The study group included eight women and two men, and the ages ranged from fifty-six to seventy-nine years at the time of the treatment for the instability (Table I). Seven patients (Cases I through 7) had anterior instability and three (Cases 8, 9, and 10), posterior instability (Table I). The diagnoses that had led to the initial total shoulder replacement included osteoarthrosis, post-traumatic osteoarthrosis, systemic lupus erythematosus, rheumatoid arthritis, and cuff tear arthropathy. Of the seven patients who had anterior instability, one (Case 1 ) had had a bilateral total shoulder replacement, but instability had developed only unilaterally. Two patients (Cases 3 and 7) had a massive (more than fivecentimeter-long) tear of the rotator cuff; one of the tears (Case 7), which involved the subscapularis tendon, was reparable. All ten of the initial total shoulder replacements had been performed through an extended deltopectoral approach, as described by Neer 7. The humeral component had been cemented in all but one shoulder (Case 9). The glenoid component had been cemented in all but one shoulder (Case 6), in which a porous-coated glenoid component had been used. All patients used a standard shoulder-immobilizer for three to six weeks after the replacement. Postoperative rehabilitation began on the first postoperative day with pendulum exercises and progressed to passive forward flexion and rotation within the ranges of motion that had been defined at the operation. These exercises and motions gradually progressed under the guidance of the surgeon and physical therapist. Gentle activeassisted exercises were begun four to six weeks postoperatively. Resistive exercises were begun at two months, and exercises with light hand-held weights were added at three months. One patient (Case 7) who had anterior instability had not participated in this program of rehabilitation because the dislocation was detected in the immediate postoperative period. The remaining patients had continued with this protocol until the instability was detected. There were three modes of presentation of the antenor instability. In one patient (Case 7). a frank dislocation was revealed radiographically in the recovery room after the operation. Operative exploration was done within one week in this patient. Four patients (Cases 3 through 6) sustained a dislocation three to seven weeks postoperatively, usually during physical therapy. A maneuver of passive external rotation, with the arm at the side or abducted 90 degrees, had caused the dislocation, which was manifested by immediate pain and loss of motion. Physical examination then revealed a decreased range of motion and a deformity consistent with a dislocation of the shoulder, and radiographs revealed the anterior dislocation. The treatment was closed reduction, immobilization, and prompt operative exploration to reconstruct the presumed rupture of the repaired subscapularis tendon. In the remaining two patients (Cases 1 and 2), a painful anterior subluxation first became apparent ten and twenty weeks postoperatively. The symptoms included a sensation of instability with pain at the extremes of motion. Increased anterior translation of the humeral component on the glenoid component of the prosthesis was detected during the examination, and VOL. 75-A, NO. 4. APRIL 1993

3 494 B. H. MOECKEL ET AL. axillary or scapular Y radiographs revealed the anterior subluxation. These patients then had a three-month trial of physical therapy, with the concentration on strengthening of the rotator cuff, but that was unsuccessful and operative treatment followed. Exploration through the previous deltopectoral incision in the seven patients who had anterior instability revealed a disruption of the subscapularis tendon in the area of the previous repair. The operative reconstruction consisted of mobilization and repair of the subscapularis tendon, with use of non-absorbable sutures that were reinforced as necessary with Mersilene tape. This procedure was performed as long as 168 days after the initial total shoulder replacement (Table I). In one patient (Case 5), the glenoid component was revised because it was loose. In another (Case 2), the glenoid component was removed because of loosening and poor remaining bone stock but the humeral stem was left in place, so the total shoulder replacement was converted to a hemiarthroplasty. None of the humeral stems were disturbed. In the five shoulders in which a modular humeral prosthesis had been used, the humeral head was removed to gain access to the glenoid and the head was replaced with a smaller component in four of those patients. Of the three patients (Cases 8, 9, and 10) who had posterior instability, two had a painful subluxation and one (Case 10) had a dislocation. One patient (Case 9) had had several anterior-stabilization procedures on the shoulder before the total replacement. One patient (Case 10), who had rheumatoid arthritis, had had a bilateral total shoulder replacement but a dislocation only on the left side. None of the three patients had a tear of the rotator cuff. At the time of the revision, the posterior aspect of the glenoid was noted to be eroded in the patient who had had previous procedures for anterior stabilization. This had not been appreciated during the initial total shoulder replacement, and the glenoid component had been placed in a retroverted position. The posterior subluxation (which was painful) was discovered on an axillary radiograph three weeks postoperatively, and the glenoid component was revised and augmented with posterior bone-grafting five weeks later. In another patient (Case 8), who was paraplegic, the repair was done through a posterior approach, and a soft-tissue imbalance, which had led to the symptomatic posterior subluxation, was revealed. Since the pathological findings included laxity of the posterior part of the capsule, this part of the capsule was plicated in an attempt to balance the soft tissues. The third patient (Case 10), who had a locked posterior dislocation (not reducible by closed means), was managed with an open reduction followed by immobilization of the shoulder in a spica. The dislocation was attributed to malposition of the component - the humeral component was retroverted 70 degrees. The modular character of the prosthesis allowed modification of the head component and thus permitted access to the glenoid during the revision procedures. In the three patients who had posterior instability, the reconstruction was performed six, eight, and fifty weeks after the initial arthroplasty. A standard shoulder-immobilizer was used by all patients. The rehabilitation protocol was individualized to avoid stress on the soft-tissue reconstructions. The preoperative, postoperative, and follow-up radiographs were reviewed for all patients. Data concerning pain, strength, and active range of motion were recorded at the follow-up examinations. Stability was determined on the basis of the patient s history, physical examination, and serial radiographs, which included axillary radiographs. The minimum duration of follow-up was two years and the maximum was five years. Results Primary reconstruction of the subscapularis corrected the anterior instability in four of the seven shoulders. Three of these four repairs (all except Case 3) were augmented with Mersilene tape. The radiographs revealed a good position of the prosthesis, with no evidence of subluxation. The average external rotation was 15 degrees (range, -10 to 25 degrees) and the average forward flexion was 98 degrees (range, 76 to 128 degrees). There was no evidence of loosening of the glenoid or humeral component in the four patients. The anterior instability recurred in three shoulders (Cases 1, 2, and 6). Mersilene tapes had been used in two of these reconstructions (Cases 1 and 6). Because of the recurrent instability, a secondary operative reconstruction was done in all three shoulders and, during these procedures, it was found that the subscapularis tendon and the capsule could not be reconstructed because of scarring and shortening. A static stabilizer, consisting of a bone-achilles tendon allograft, was inserted in these shoulders, to reinforce the subscapularis tendon. The osseous portion of the allograft was secured to the neck of the glenoid process with a lag screw and a washer, and the tendon was secured similarly to the lesser tuberosity (Fig. 1). To ensure that correct tension of the graft was achieved, the repair was performed with the arm in 60 degrees of abduction and 30 degrees of external rotation. Additional operative procedures were carried out in two patients at the time of the secondary allograft reconstruction. In one (Case 1), in addition to the allograft, a custom-made modular humeral head was inserted in increased retroversion. This was attached to the humeral stem, which was well fixed. In the other patient (Case 6), a loose porous-coated glenoid component was removed at the time of the secondary reconstruction, and a new component was inserted with cement. The anterior restraints were reconstructed successfully with the allograft in all three shoulders. Postoper- THE JOURNAL OF BONE AND JOINT SURGERY

4 INSTABILITY OF THE SHOULDER AFTER ARTHROPLASTY 495 FIG. 1 A secondary reconstruction was done in three patients in whom the anterior instability had recurred. This drawing illustrates how the bone-achilles tendon allograft was secured to the glenoid neck and humeral head. ative radiographs revealed that the subluxation or dislocation had been reduced. There was no evidence of recurrent instability. The range of motion averaged 85 degrees of forward elevation (range, 78 to 93 degrees) and 5 degrees of external rotation (range, -15 to 20 degrees). At the time of follow-up, there was no evidence of loosening of the glenoid or humeral component. Stability was achieved with the primary revision in two patients (Cases 9 and 10) who had had posterior instability. External rotation in these two patients was 39 and 43 degrees and forward elevation was 108 and 132 degrees. There was no evidence of loosening of the glenoid or humeral component. In the third patient (Case 8), who, as mentioned, was paraplegic, the revision was performed through a posterior approach, but the instability recurred after the patient resumed using the arm to operate a wheelchair four months postoperatively. Six months later, all of the components were removed, and the patient was considering a revision procedure at the time of writing. There were no complications with respect to either the wound or the neurovascular structures. Discussion Instability is a known but uncommon complication after total arthroplasty of any large joint, whether it be the hip, knee, or elbow. It is no surprise, then, that instability sometimes occurs after total shoulder replacement, especially because the osseous constraints are minimum as compared with those in the other large joints. Instead, it is a surprise that the complication is rare. There has been limited discussion in the literature concerning the etiology and management of instability after total shoulder replacement, despite the fact that various authors have noted the complication. Neer reported that, in a series of eight patients who had been managed with total shoulder replacement for osteoarthrosis, recurrent dislocation occurred in two patients and transient subluxation occurred in two. In a larger series of 194 patients, Neer et al.7 reported a dislocation in four shoulders and a subluxation in four. Three of the dislocations were treated successfully with closed reduction and immobilization, but persistent subluxation developed in the fourth patient who had had a dislocation. Two of the subluxations, which were anterior and associated with increased anteversion of the humeral head, were treated with revision of the prosthesis. The other two subluxations, which were inferior, were treated with immobilization in a spica, but the results were poor. Barrett et al. reported only one posterior subluxation, which resolved with vigorous physical therapy, in a series of fifty shoulder arthroplasties. Amstutz et al. found one subluxation and one dislocation in a study of fifty-six shoulders. All three were treated successfully by substitution of a hooded glenoid component for the unhooded one. Instability after shoulder arthroplasty can be classifled according to the direction of pathological translation of the humeral head on the glenoid; the translation can be superior, anterior, posterior, or inferior. Superior subluxation is the most common, and it is related to failure or dysfunction of the rotator cuff. Inferior subluxation is most often attributed to inadequate restoration of proper humeral length during the replacement. This technical error is most common when hemiarthroplasty is performed after a fracture of the proximal portion of the humerus. These two types of instability were not considered in the present report. Anterior and posterior instability after shoulder arthroplasty, the subject of the present study, is generally caused by imbalance of the soft tissues or by malposition of one or both of the prosthetic components. Because of the lack of constraint in the models of prostheses commonly used in total shoulder replacement, stability is highly dependent on the soft-tissue envelope. If those tissues are too loose, instability may occur, but if they are sutured too tightly during the reconstruction, they can rupture at the site of the repair when the patient attempts to obtain more motion than the repair allows, or they can force the humeral head to subluxate in the direction opposite to the site of the repair. Overtightening of the soft tissues might have contributed to the instability in some of the patients treated early in this series, and this possibility highlights the importance of assessment of the range of motion permitted by the repair in the operating room. The motion allowed during early postoperative rehabilitation must be limited to this range of motion, to allow for the soft tissues to heal well. VOL. 75-A, NO. 4. APRIL 1993

5 496 B. H. MOECKEL ET AL. FIG. 2 Posterior glenoid erosion resulting in a retroverted glenoid component. FIG. 3 Posterior bone-grafting of the glenoid was done to restore the correct anatomical relationship. The glenoid face should be perpendicular to the spine of the scapula. Essential to the preoperative planning is a review of the axillary radiograph to determine whether there has been erosion of the bone of the glenoid. If so, there may be increased retroversion of its articular surface. During a total shoulder replacement, as well as during a revision for instability, the position of the humeral head on the glenoid must be assessed. Galinat and Howell have pointed out that the posterior border of the scapula provides a useful landmark for assessment of the orientation of the articular surface of the glenoid. The border should be nearly perpendicular to the glenoid face, and the humeral head should be centered on the glenoid. If the orientation of the glenoid and humeral components is correct, then the soft tissues can be balanced properly. If good-quality axillary radiographs cannot be made, computed tomography scans may provide the information needed for preoperative planning. In all seven of our patients who had anterior instability, the primary etiology of the instability was a disruption of the repaired subscapularis tendon. For some of these patients, the amount of external rotation permifled during the early regimen of postoperative rehabilitation after the initial total shoulder replacement may have exceeded that allowed by the repair. To avoid this complication, we now attempt to achieve 30 to 40 degrees of external rotation at the time of the subscapularis repair. However, the ultimate range of motion must be assessed in the operating room, and this range becomes the guideline for the limit to be used during the rehabilitation. The operative treatment of postoperative anterior instability secondary to subscapularis rupture should indude mobilization and repair of the tendon. If a modular prosthesis is in place, a change in the size of the humeral head component can adjust the soft-tissue balance. Custom-made humeral heads are available so that the surgeon can modify the degree of humeral version without replacing the stem of the prosthesis. Cofield and Edgerton4. in a recent review of the topic of complications after total shoulder replacement, drew attention to the importance of the repair of the subscapularis and discussed the difficulty that is encountered when the subscapularis tendon is ruptured. Our results confirm their observations: our initial reconstructions were unsuccessful in three of our seven patients who had antenor instability. It might be possible to prevent anterior subluxation by proper positioning of the components during the total shoulder replacement and release of any anterior and posterior contractures. This allows a proper degree of translation of the humeral component of the prosthesis on the glenoid. The humeral head should translate about 50 per cent of the width of the glenoid in both the anterior and the posterior planes and about one-third of the face of the glenoid in the inferior plane. The contracted capsule can be released to achieve the proper balancing of the soft tissues within the joint, and the subscapularis tendon can be lengthened to improve the range of external rotation. Additionally. the coracohumeral ligament can be incised and adhesions external to the rotator cuff can be released. If the subscapularis repair is tenuous, it can be reinforced with Mersilene tape. If the insertion of the tendon on the lesser tuberosity is insufficient, the sutures or the Mersilene tape are placed through the bone before the prosthesis is inserted. When a patient has recurrent instability and the subscapularis cannot be repaired, we use a technique that includes insertion of an allograft of the Achilles tendon and the calcaneus to replace the incompetent subscapularis and anterior aspect of the capsule. It has proved successful in the patients in whom it has been used. The etiology of posterior instability is multifactorial. As an example, one of our patients had osteoarthrosis and associated erosion of the posterior aspect of the glenoid. Only in retrospect did we recognize that the THE JOURNAL OF BONE AND JOINT SURGERY

6 INSTABILITY OF THE SHOULDER AFTER ARTHROPLASTY 497 preoperative axillary radiograph had showed the erosion and that the erosion had caused retroversion of the glenoid component (Fig. 2). If this pathological finding is recognized, bone-grafting of the glenoid (Fig. 3) or anterior resection of the glenoid will correct minor abnormalities in version. This correction is combined with a decrease in the amount of humeral retroversion to decrease the posterior translation of the humeral head. More recently, the use of a custom-made glenoid prosthesis that is thick posteriorly has been used to correct the glenoid version. Anterior contractures of the soft tissues combined with posterior capsular laxity can also lead to posterior instability. An axillary radiograph is helpful in such a situation because it reveals the position of the humeral head relative to the glenoid face. This etiology was evident in two of our patients who had posterior instability. This combination of pathological findings should be treated with soft-tissue rebalancing in combination with a decrease in the amount of humeral or glenoid retroversion, or both. Still another cause of posterior instability may be excessive humeral retroversion, which may be encountered if the total shoulder replacement is being performed for a long-standing posterior dislocation. The degree of humeral retroversion then should be decreased from the usual 40 degrees to approximately 10 degrees, to decrease the tendency for posterior displacement. If the posterior instability is not prevented, the excessive retroversion of the humeral head should be decreased at the revision or, if a modular prosthesis was inserted, a custom-made modular humeral head with decreased retroversion can be used. The posterior instability in our paraplegic patient had an unusual cause: it was attributed to one unusual daily activity. While transferring herself from a wheelchair to a bed or to a chair, this patient applied a tremendous posterior stress on the capsule of each shoulder. Because the instability manifested itself so late after the total shoulder replacement, we think that the postoperative factors of overuse most likely played a role in the production of the instability. Proper treatment of instability should begin with a determination of the etiology, so that the best treatment can be selected from the available options. Use of a modular prosthesis during the replacement increases the number of options for subsequent revision, especially if the orientation of the component becomes an issue. Our results indicate that instability after total shoulder replacement is difficult to treat successfully. Thus, prevention of the complication by proper positioning of the component and balancing of the soft tissues during the total shoulder replacement is essential. The postoperative program of physical therapy should limit the range of motion of the shoulder to that deemed safe in the operating room. Early recognition of instability in the postoperative period is important, as a subscapularis rupture will become increasingly difficult to repair. An assessment of the etiology of the instability is critical, and we recommend early exploration if there is a strong suspicion of a subscapularis rupture. If it is thought that the loss of muscle tone and soft-tissue tension are playing a part in the instability, rehabilitation with protection from the extremes of motion is advised. The treatment of the dislocation or subluxation includes reconstruction of the soft-tissue envelope, revision of the prosthetic components, and possibly the use of allografts to correct deficiencies in the soft tissues, or a combination of those techniques. References 1. Amstutz, H. C.; Thomas, B. J.; Kabo, J. M.; Jinnah, R. H.; and Dorey, F. J.: The Dana total shoulder arthroplasty. J. Bone and Joint Surg., 70-A: 1174-l182.Sept Barrett, W. P.; Franklin, J. L.; Jackins, S. E.; Wyss, C. R.; and Matsen, F. A., III: Total shoulder arthroplasty. J. Bone and Joint Surg., 69-A: , July Cofield, R. H.: Total shoulder arthroplasty with the Neer prosthesis. J. Bone and Joint Surg., 66-A: , July Cofield, R. H., and Edgerton, B. C.: Total shoulder arthroplasty: complications and revision surgery. In Instructional Course Lectures, The American Academy of Orthopaedic Surgeons. Vol. 39, pp Park Ridge, Illinois, The American Academy of Orthopaedic Surgeons, Galinat, B. J., and Howell, S. M.: The glenohumeraljoint. Ortlzop. Trans., 12: 143, Neer, C. S., II: Replacement arthroplasty for glenohumeral osteoarthritis. J. Bone and Joint Surg., 56-A: 1-13, Jan Neer, C. S., II; Watson, K. C.; and Stanton, F. J.: Recent experience in total shoulder replacement. J. Bone and Joint Surg., 64-A: March O Brien, S. J.; Schwartz, R. E.; Warren, R. F.; and Torzilli, P. A.: Capsular restraints to anterior/posterior motion of the shoulder. Orthop. Trans., 12: 143, VOL. 75.A, NO. 4. APRIL 1993