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Modular shoulder arthroplasty
ORIGINAL ARTICLES Modular Gary M Houston,
shoulder
arthroplasty
Gartsman, MD, Jeffrey A Russell, MS, ATC, and Ertc Gaenslen, Texas, and Mhvaukee, W/scans/n
MD,
One hundred consecutive Biomet modular shoulder arthroplasties were studied prospectively and were evaluated with a minimum 2-year follow-up [average 4 I months). Fifty-seven women and 43 men with an average age of 64 years were evaluated for pain, activities of daily living, range of motion, cost, and complications. Fourteen patients had undergone previous surgery to the shoulder. Seventy patients underwent total shoulder arthroplasty, and thirty underwent hemiarthroplasty. Pain and range of motion demonstrated statistically significant improvement. Eight activities of daily living were rated on a 0 to 3 scale, and a// were significant/y improved. Complications were noted in I8 patients and included urinary retention, pulmonary embolus, rotator cuff tear, titanium synovitis, subluxation, and dislocation. Twelve shoulders underwent secondary procedures for rotator cuff repair, open reduction, and component revision for instability. Lucent lines were present in 62.5% of glenoids, 92.3% of cemented stems, and 0% of cementless stems on postoperative radiographs. No patients underwent revision surgery for component loosening, and no cases of humeral head-stem dissociation were seen. Ninety-five shoulders were rated by the patients as improved, and five were made worse. (J SHOULDER ELBOW SURG 1997;6:333-9.)
as introduced by Neer14, I5 Shoulder arthroplasty is an effective method of improving pain, function, and movement in patients with glenohumeral arthritis.” 4, *, “, l6 Recently interest has developed in modular shoulder arthroplasty systems offering the ability to interchange different humeral head sizes on different sized humeral stems. This allows the surgeon greater flexibility in matching the implant to the patient’s anatomy and obtaining a better fit. Publications concerning modular systems have been limited to their use in trauma.5 To date one report has described the results of modular shoulder arthroplasty in patients with primarily atraumatic causes of glenohumeral degeneration.8 The purpose of this report is to present our experience with a single modular shoulder arthroplasty
system (Biomodular Warsaw, Ind.).
Total Shoulder
System,
Biomet,
METHODS Between May 1988 and September 1992, 108 consecutive shoulder arthroplasties were studied prospectively. Eight patients were excluded because of inadequate follow-up. Four of these patients could not be located at the time of review, two were deceased, and two who had returned for their l-year evaluation could not return for the 2-year review. This left a group of 100 shoulders with an average follow-up of 5 1 months (range 41 to 96 months), who form the basis of this report. All procedures were performed by one surgeon (G. M. G.). Range of motion, function, and pain were recorded with a standardized scoring system.18 There were 52 women (4 bilateral) and 44 men who had an average age of 64 years (range 27 to 87 years) at the time of their index surgery. Preoperative diagnoses are listed in Table I. Fourteen patients had undergone previous surgery to their shoulder. Three had operative fixation of
333
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Gartsman,
Russell,
Table
1 Preoperative
J. Shoulder Elbow July/August
48
14
arthritis
Acute trauma Avacular necrosis
12 9
Old trauma Cuff arthropathy Arthritis
Gaenslen
dlaqnosls
Osteoarthritis Rheumatoid
and
of recurrent
9 9 dislocation
1
fractures, three had previous hemiarthroplasty, and two each had acromioplasty, rotator cuff repair, and repair for shoulder dislocations, Preoperative radiographic analysis included an anterior-posterior view, an axillary lateral view, and a supraspinatus outlet view. Glenoid version and areas of posterior or anterior erosion were determined from the axillary radiograph. Retroversion or anteversion >5” was considered significant. Anterior-posterior and axillary lateral views were taken at the first postoperative visit, 6 months after surgery, and yearly thereafter. No fluoroscopic examinations of the shoulder4 were performed. Glenoid components were evaluated for potential radiographic evidence of loosening including the presence and progression of lucent lines around the keel, the presence of fracture lines within the cement mantle, and evidence of fracture or migration of the component. All glenoid components were cemented. Cemented humeral components were evaluated for potential radiographic evidence of component loosening including the presence and progression of lucent lines, the presence of fracture within the cement mantle, the development of osteolysis, and the presence of stem migration. In addition, radiographs were evaluated for the presence of stress shielding.6 Cementless stems were evaluated for potential radiographic evidence of loosening including the presence and progression of lucent lines, canal widening,7 the presence of osteolysis, and stem migration. In addition, cementless stems were also evaluated for potential signs of ingrowth including the absence of lucent lines, the presence of increased density or spot welds of endosteal new bone adjacent to the stem, the presence of pedestal formation beneath an otherwise stable stem, and evidence of stress shielding.7 The humeral stems were divided into seven zones analogous to the seven zones of the femoral stem as described by Gruen.9 The glenoid component was divided into eight radiographic zones based on a modification of the description of O’Driscoll.r7
Surg. I997
The surgical indications were pain and limitation of function interfering with activities of daily living associated with radiographic evidence of cartilage loss in the glenohumeral joint and unresponsive to conservative care, which consisted of activity modification and nonsteroidal antiinflammatory medications. Surgery was also indicated in patients with displaced three- and four-part fractures or fracture dislocations. Contraindications to surgery included recent infection of the glenohumeral joint, a neuropathic joint, or paralysis of the deltoid and rotator cuff. The surgical technique used has been previously described’, 4, 8, l6 and differs only in the variation required for the use of the modular humeral head. Once the humeral stem size was been selected, various sized humeral heads were then placed on the humeral shaft until the best combination of stability, mobility, and soft-tissue tension in the deltoid and rotator cuff was achieved. The appropriate humeral head was then impacted on to the shaft after checking that no soft-tissue ‘debris or fluid was present in the peg hole. The patient was started on passive range-ofmotion exercises on day 2, and therapy continued until the patient had 120” of elevation and 40” of external rotation. The patient was then discharged from the hospital. If no rotator cuff tear was performed, active assisted range of motion was started at 2 weeks. If a rotator cuff repair was performed, passive range of motion continued until 6 weeks, at which point active range of motion was started. Strengthening was started at 3 months. Patients were seen 2 weeks, 6 weeks, and 3, 6, 9, and 12 months after surgery. They were then seen at yearly intervals. At each yearly visit the patient completed a self-assessment questionnaire that included evaluation of activities of daily living and a pain scale. Range of motion was independently measure by a physical therapist. Radiographic assessment was made as described previously.
RESULTS Surgical findings. Sixteen (16%) patients had rotator cuff tears. The preoperative diagnosis and tear size are listed in Table II. Four were small (~1 cm), 2 were medium (~3 cm), and 10 were massive irreparable tears (>5 cm). The six small and medium tears were repaired after the prosthesis was inserted. The 10 irreparable tears were
/. Shoulder Elbow Volume 6, Number
Table
Gartsman,
Surg. 4
II Rotator cuff tears
Table
Russell,
Ill Acttvltles
Osteoarthritis Rheumatoid AVN
1 arthritis
Cuff arthopathy Acute trauma Arthritis of recurrent
AVN.
c3cm
>5cm
1
2 1
dislocation
Dress
1.18
0.52 0.89
2.50 2 28
behind
back
7
Reach high shelf Lift 10 pounds above shoulder Work
Avascular
of datlv hvlna
Sleep Reach Toilet Comb
1
335
Postoperative
2 2 1
Gaenslen
Preoperative
Size Diagnosis
and
1 42 hair
0 80 0 37 0.20 0 80
1.55
2 64 2 27 1 60 1 40
2 28
necr0.w
treated with rotator cuff debridement and hemiarthroplasty. Five patients had significant alteration of glenoid version such that changes in humeral version were required to improve intraoperative stability. Four patients with osteoarthritis had posterior glenoid erosion and required leveling of the glenoid with a reamer. The resulting level glenoids were still retroverted an average of 7” (range 5” to 10’). The four patients with retroverted glenoids were treated by alterations in the humeral osteotomy. The humeral component was placed in less retroversion so that the combined humeral-glenoid retroversion was 40”. All were believed to be stable at the time of subscapularis closure. One patient with arthritis caused by recurrent dislocation had anterior glenoid erosion measuring 10”. This patient was also treated with a modified humeral osteotomy, which placed the humeral component in more retroversion. This procedure allowed intraoperative component stability to be achieved. In no patient was a glenoid bone graft required. Hemiarthroplasty was performed in 30 shoulders, and 70 patients had humeral and glenoid components inserted. The indications for hemiarthroplasty were normal glenoid cartilage such as seen in avascular necrosis and acute trauma, insufficient bone stock (rheumatoid arthritis), or an irreparable rotator cuff tear. The humeral component was press-fitted in 69 cases and cemented in 31. The indications for cement were failure to achieve a firm press fit because of inadequate bone stock in the proximal humerus or in cases of acute trauma requiring the humeral prosthesis to be placed in a superior or “proud” position. Varying sizes of humeral stem and humeral head implants were used. Stem size 6 was used in all 1 1, size 7 in 16, size 9 in 32, size 1 1 in 38,
and size 13 in 3. Head size 40 x 15 was used in 20 shoulders, head size 40 x 20 in 18, size 44 x 17in22,44x22in30,and48x24in 10.A standard sized glenoid component was used in all cases. Pain. Pain was assessed by the patient on an analog pain scale that rated pain from 0 (no pain) to 10 (pain as bad as it can be]. Preoperative pain averaged 8.1, and postoperative pain averaged 2.9. These results were significant at p < 0.0001 with the sign test. Ninety-one of 100 shoulders showed improvement, 7 showed no change, and 2 showed worsening. Range of motion. Range of motion was measured in three planes: elevation, external rotation, and internal rotation behind the back. Elevation increased from an average preoperative measurement of 82” to an average of 129” after surgery. Average external rotation improved from 16” to 55”. Average internal rotations changed from the sacrum to T12. All increases were significant at p < 0.0001 with the paired t test. Elevation mean difference increased 47 2 4.5, T = 10.28. External rotation mean difference increased 39 + 2.8, T = 14.16. Internal rotation mean difference increased 6.5 vertebral levels -C 0.5 increments, T = 13.52. Function. Eight routine activities of daily living were self-assessed by the patient before surgery and at last follow-up and are listed in Table III. All activities of daily living demonstrated a statistically significant increase with p < 0.0001 with the exception of reaching behind the back (p < 0.001). Subjective response of the patient. Patients were asked on the questionnaire at last follow-up whether their shoulder was improved, the same, or worse after their surgery. Ninety-five (95%) believed their shoulder was improved, and
336
Gartsman,
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5 (5%) believed their shoulder was worse. Patients were also asked whether they would have the surgery again if they knew the end result. Ninety (90%) believed they would have the surgery again, and 10 (10%) believed they would not have the surgery performed. Radiographic evaluation. A maior limitation of the study was the number of radiographs available for review. Radiographs were included for analysis only if sequential films were of sufficient quality and allowed reproducible evaluation of the criteria described previously. Therefore only 24 glenoid components and 41 humeral stems were analyzed. In the immediate postoperative period eight glenoids demonstrated complete lucent lines, seven, incomplete lines, and nine, no lucent lines. At final follow-up complete lucent lines were noted in 20 prostheses, incomplete lines in 3, and 1 demonstrated no lucency. Progression of the lucent lines was noted in 18. There was no tendency for the lucent lines to develop in any particular zone around the glenoid, and no lucent lines were between the stem and the cement. Cement fracture was noted in five. There were no glenoid component fractures. Glenoid migration was noted in five shoulders. Two patients were revised for glenohumeral dislocation. Three patients with glenoid migration were doing satisfactorily. One patient was believed to have symptoms from glenoid loosening and underwent revision for glenoid loosening. The loose glenoid was documented with arthroscopy. The glenoid was removed at open operation. Thirteen shoulders with cemented stems were analyzed. Analysis demonstrated that in the immediate postoperative period 5 (38.5%) of 13 showed complete lucent lines, 7 (53.8%) of 13 showed incomplete lucent lines, and one showed no lucent lines. At final follow-up 6 (46.2%) of 13) cemented stems showed complete lucent lines, 7 (53.8%) of 13 s h owed incomplete lucent lines, and no stems were free of lucent lines. There was no tendency for lucent lines to develop in any particular zone around the stem. Cement fracture was noted in 2 of 13 shoulders. Stem migration occurred in one shoulder. Osteolysis was seen in 4 of 13 stems at an average of 23 months. The one radiographic parameter suggestive of stem stability, stress shielding, was present in 6 of 13 patients beginning an average of 25 months after surgery. Twenty-eight noncemented stems were analyzed in the immediate postoperative period, and none
J. Shoulder Elbow Surg. July/August 1997
showed any lucent lines. At final follow-up none demonstrated a complete lucent line, 3 (10.7%) of 28 showed an incomplete lucent line, and 25 (89.3%) of 28 continued to show no lucent line formation. One stem showed 2 mm of distal migration in the first 6 months but was stable thereafter. Osteolysis was not demonstrated around any stem. Radiographic evidence of increased density or “spot welding” was present in 17 (60.7%) of 28 stems and was present beginning at an average of 18 months after surgery. Sclerosis was most common at the medial and lateral distal aspect of the stem just proximal to the tip. Radiographic evidence of stress shielding was present in 17 (60.7%) of 28 stems beginning at an average of 32 months after surgery. Evidence of stress shielding was most notable in the proximal lateral portions of the humerus. Pedestal formation developed at the tip in 13 (46.2%) of 28 stems that were by other parameters also radiographically stable. This finding was first seen at an average of 25 months after surgery. Complications. Complications occurred in 18 (18%) of the shoulder arthroplasties and are listed in Table IV. No intraoperative complications occurred. One patient had urinary retention after surgery and required transurethral prostatic resection. One patient had a pulmonary embolus 2 days after discharge and required hospitalization and anticoagulation. Two patients had traumatic episodes. One patient had a rotator cuff tear after falling from a ladder and required a rotator cuff repair. One patient was involved in an automobile accident and sustained bilateral fractured femurs and tibias. She dislocated her glenoid component and required glenoid component removal. One patient had persistent wound drainage. He was returned to the operating room on the fourth postoperative day, and the wound was irrigated. The patient did well and required no further surgery. One musculocutaneous nerve palsy resolved completely by the sixth postoperative week. One patient had titanium synovitis; she required humeral head and glenoid revision. The well-fixed humeral stem was left in place. Glenohumeral instability was the source of the greatest number of complications. Recurrent anterior dislocation developed in three patients, all of whom had rheumatoid arthritis. All were pleased with their shoulder function and level of pain and did not desire revision. Superior-anterior dislocation was seen in two patients with cuff arthropathy
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Russell, and Gaenslen
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Table IV Compllcatlons Type
Number
Complication
Diagnosis
Surgery required
Systemic
1 1
Urinary retention Pulmonary embolus
OA post-traumatic
Wound Trauma
1 1 1
Drainage Rotator cuff
post-traumatic AVN
Yes
RA OA
Yes No Yes
Nerve
1
Prosthetic InstabIlity
1
Nerve 3
5
3
tear
Glenoid dislocation Musculucutaneous
No No Yes
palsy
Titanlum Superior
synovitis medial
instabillty
OA OA
Superior
medial
Instability
Cuff
arthropathy
Superior Posterior
medlal instability subluxation
Cuff OA
arthropathy
Posterior Posterior
dislocation dislocation
OA OA
Posterior Posterior
dislocation dislocation
Anterior Anterior
dislocation dislocation
OA OA RA
Anterlor
dislocation
and one patient with osteoarthritis. One patient with rotator cuff arthropathy had good relief of pain and adequate below-shoulder level function and did not desire further surgery. The other two had symptoms and underwent revision as described in the following text. Five patients with osteoarthritis had posterior instability. Posterior subluxation was noted in one patient. Elevation was limited to 9O”, but the patient had painless below-shoulder activity and did not desire further surgery. Four patients had posterior dislocation of the humeral head. One patient had elevation to 80” but was satisfied with his shoulder. Three others were not satisfied and underwent revision as described in the following text. At the time of their index surgery all five patients had posterior glenoid erosion and posterior humeral head subluxation noted on the axillary radiograph. Decreased external rotation was documented at the examination with the patient under anesthesia (average 14”). The glenoid was reamed so that a level surface resulted. As noted previously, some glenoid retroversion remained, averaging 7” (range 5” to 10’). Soft-tissue balancing was accomplished by placing the humeral component in 5” to 10” less retroversion; the appropriate humeral head size was selected for the best combination of mobility and stability, and enough subscapularis mobility was gained to achieve 45” external rotation. All patients were believed to be stable at the conclu-
RA RA
sion of their postoperative
Yes Yes No No No Yes Yes Yes No No No
index surgery, and in no case was bracing or casting used. Failures and Revision Surgery. Ten (10%) shoulders underwent revision surgery of their shoulder. The two patients with injuries had sustained sufficient trauma so that it was reasonable to assume the injury was the cause of the shoulder problem. The patient with the traumatic rotator cuff tear and rotator cuff repair never regained satisfactory, above-shoulder level use of the arm, although pain has been controlled and she is able to use the arm for below-shoulder level activities without difficulty. The patient with the dislocated glenoid component was converted to a hemiarthroplasty with good shoulder function. The patient with wound drainage did not have an infection in the shoulder, and 6 years after surgery she has evidence of radiographic lucency. Early Biomet humeral head prostheses were titanium, and one patient as described previously had titanium synovitis and required revision. At surgery a proliferative blackened synovium was noted. One patient developed shoulder pain six years after operation. Arthroscopy demonstrated a loose glenoid that was removed, and the patient was given a hemiarthroplasty. Glenohumeral instability accounted for the other five revision procedures. Two patients, one with osteoarthritis and one with rotator cuff arthropathy, had anterosuperior dislocation of the prosthesis
338
Gartsman,
Russell, and Gaenslen
and required revision. Both patients had undergone a coracoacromial ligament resection and hemiarthroplasty at the time of their index surgery. One patient with rotator cuff arthropathy was revised to a larger humeral head size, and the prosthesis was placed in an additional 20” of retroversion. He continued to dislocate anterosuperiorly and was unsatisfied with his end result. One patient with osteoarthritis and a normal rotator cuff was revised in a similar fashion with a similar end result. Three patients with posterior instability (one subluxation, two dislocations) required revision surgery. One patient with a total shoulder replacement had the humeral head converted to a smaller size and did well with no recurrence of instability and good shoulder function. Another patient with a total shoulder arthroplasty had the humeral stem changed and reinserted in 15” more anteversion with a smaller sized humeral head. He continued to have recurrent posterior dislocation and had a poor result. He declined further surgery. One patient with a total shoulder replacement had removal of the glenoid and a larger size humeral head inserted. He did well with no recurrence of instability and good shoulder function.
DISCUSSION The success of nonmodular shoulder arthroplasty has been noted by Neer,16 Cofield,4 and Barrett.’ FenlinE has reported his results with a modular shoulder system. This report serves to document similar improvements in range of motion, function, and pain after modular shoulder arthroplasty. Patient satisfaction is high. No complications (humeral head-stem dissociation) occurred that can be related to the modular system. The theoretic advantages of a modular shoulder arthroplasty system include increased number of humeral head-stem combinations to better adjust soft-tissue tension,‘O the ability to more easily insert a glenoid component following hemiarthroand the ability to replace a humeral head plasty, ’ 9 at a later date to address problems of instability or humeral head wear. In this series 50% of all patients had humeral head sizes other than the standard 15 and 22 mm head sizes that existed in the Neer nonmodular system. Therefore at the time of surgery it was our opinion that half of the patients were better served by a modular system that allowed the surgeon increased flexibility in matching component size to the bone and softtissue anatomy. What we cannot demonstrate is
J. Shoulder Elbow Surg. July/August I997
that the increased number of choices resulted in an improved result. It is intuitively obvious that glenoid revision or conversion of a hemiarthroplasty to a total shoulder arthroplasty is easier with a modular than a nonmodular system. A modular head can be removed, the glenoid adequately exposed and prepared, and a glenoid inserted without the difficulty of humeral stem removal. However, in this series no glenoids were replaced for symptomatic loosening, and no hemiarthroplasties developed symptoms such that conversion to a total shoulder arthroplasty was advised. Two patients required humeral stem version changes, and modularity did appear beneficial because it allowed access to the stem-bone interface and attachment of a stemextracting device. With regard to the management of instability in two additional patients, modularity was beneficial. One patient was successfully treated with humeral head exchange and a smaller head size, and one patient had the humeral head and glenoid removed and a large-sized head implant inserted. Neither of these patients required stem revision, significantly decreasing the complexity of the procedure. Whether the benefits that were apparent in these four shoulders justify the use of a modular system in the other 96 is not answerable in this study and will depend on further reports that evaluate patient outcome and cost comparing modular and nonmodular systems. There are of course theoretic and actual disadvantages to modularity in shoulder arthroplasty. Although no cases of humeral head dissociation occurred, Blevins3 reported that 13 clinical dissociations of the Morse taper design used in this series have occurred. They suggested that allowing fluid or blood into the “reverse” Morse taper and the resulting weakening of pull-off strength may be a causative factor. However, Loch12 has presented data to suggest that the axial taper junction is not weakened if wet. Some degree of separation must exist between the humeral stem and head in a modular system. In theory this may result in a decreased head size and arc available for motion and stability.13 Cost is another factor that must be considered. The current list price for Biomet’s Biomodular prostheses (humeral stem, humeral head, and glenoid) is $1966, whereas the DuPuy Global price is $3665. This is compared with the nonmodular systems such as the Neer at $1092 and the Global at $1385. The design features of the humeral prosthesis
/ Shoulder Elbow Volume 6, Number
Gartsman,
Surg. 4
used in this series allow for cementless insertion of a humeral stem with an ingrowth surface in the proximal portion of the stem. However, ingrowth surfaces have unproved value in the humerus. Aseptic loosening appears to be infrequent, and strategies to avoid loosening seem to be less important than in the glenoid or in other joints. Humeral stem revision is more commonly performed for glenohumeral instability, component malposition, or infection. The excellent fixation provided by the cementless stem may make stem removal difficult, increasing the risk of humeral fracture or perforation. The orthopedic literature contains numerous articles dealing with the potential problems of implant design and fixation. Barrett’ reported a 14% incidence of glenoid loosening 14 to 44 months after surgery. All seven patients were noted to have a massive tear of the rotator cuff at the time of the index operation. Our 1% incidence of symptomatic glenoid loosening may represent better implant design but more likely simply reflects the orthopedic community’s increased understanding of shoulder kinematics. In this series massive rotator cuff tears were a contraindication to glenoid placement, and those patients with massive rotator cuff tears were treated with hemiarthroplasty without insertion of a glenoid component. Although humeral stem loosening remains a concern, in this series only one patient had radiographic evidence of humeral stem movement (2 mm), and no patient underwent revision surgery for humeral stem loosening. We found that lucent lines are extremely common around the cemented humeral and glenoid components after shoulder arthroplasty. The presence of lucent lines, however, is not necessarily a poor prognostic sign and is usually associated with stable fixation. We also found that cementless humeral stems show intermediate term radiographic stability with minimal development of Iucent lines, moderate development of sclerosis adjacent to the stem, and moderate evidence of stress shielding. Radiographic evidence of bony attachment to the prosthesis was most common at the endosteal bone surfaces adjacent to the distal stem rather than from the cancellous bone adjacent to the proximal porous coating of the humeral stem. The complication most frequently affecting patient outcome was glenohumeral instability after arthroplasty. Glenohumeral instability surgery has been documented as a cause of shoulder arthritis requiring arthroplasty2 but not as a result of shoul-
Russell, and Gaenslen
339
der arthroplasty. This complication occurred despite careful attention to soft-tissue balance, implant selection, and postoperative rehabilitation and serves to emphasize the complexity of shoulder arthroplasty.
REFERENCES 1
Barrett CVP, Fror~i IlnJl,Jack~ns SE, Wvss CR, Ma&n sho~~lder orthroplasb J Bone Jnlnt Sury Arl 1387 72
FA Total 63 865
2
3
4
C<,fleld RH Totol st~oultler arthrc+std j,< J Brine Jc’ln+ Sur’3 4m 1384 66
with the i‘leer 8QQQ@6
5
Dines acute
6
Erlgh CA Bobvn JD Glownon AH P~JI~ws-cnated hip replocement thr foctnrs gsxernlng bone Ingr’I*th stress sh& ~ng qnd cllnlcol results J Bone Jn~nt Surg Am 1987 69 4.5 55
7
Engh CA fiflassln P, Suthers kE Roentgenogrophlc. obsessmerit %,f the b~olog~z fl*oilon ot porous-surfrlcc compownts Cl11 (LIlthop 1990 257 107~28
8
F&n JM, P~~msey Ml, Allordycx rJ, Brlormon BG ~fl~~dulor total \ha~Jldrr replacement desl’zn ro!~~xol~ ~ndxat~o~s and r&ts Clan @rlhop 1994.07 3?~46
9
GrlJrn TA, Mcr\jlecp c*mented stem~b?pe ~nal\ws of Iwwnlng
DM. l,Vonen PF iL’~odulo~ shoulder froctl.tres Clan Orthop 1994,307
prosthe-
hem~nlthruplos~ i 8 26
fe?r
Gn”, P.mstutz HC p”lodes of tallure fsm,:~rol components A rad;ogrophlc Cllr Orthnp 19i9,14 1 17-29
of
10
Holrymar DT. Sidles Jb,, Harris Sl LIppItt 5B. motseri FA The eifect #If ~rt~color corlformlp/ and the we of the humerol head #:ornpnwnt f3n IOYI~~ nnd motion oft?, glenohumwal nrthropla+J J Bone Joint SIJI!J Arr~ 190.577 555 63
11
Hov~I~ns RJ. Bell PH J~>Ilay B Tot01 shoulder Qithi>p 1’389 242 188-93
12
loch DA, Glwsx PF b yle JE Bwhtc,l D strength ot dry rind \wt taper head connectIons shoulder prwthzx Trans OPS 1’994, 19 826
13
bhotsen FA. llpplti SB Sidles JA How/man DT Mechanlrs of glenohunwol orthraplosty In Proctlcal evaluotlirn and mom ogement rit the shoulder Ph~ludelptl~a C’VB Sounders, 1094 201
14
rJPerSS Jrirrt
arthroplasb
krt~culur lqlocement fc?r ihe hurnelal Surg Am 1955 37 2 15-28
AvIal pull-off w o Inodular
hend
15
New CS RepIncement J Bone J>lnt SUIT Arrl
16
t\leer CS, bl/atson KC Stanton FJ Recent experience sholJder replacemwt J Bone jolnt SIJI~ Arr~ 1982.64 37
17
18
19
Clan
arthroplosty for glenohumProl 1974.56 1~1 3
J Bone arthritis In total 3 19-
shoulder
arthroplasty
Gartsman, MD, Jeffrey A Russell, MS, ATC, and Ertc Gaenslen, Texas, and Mhvaukee, W/scans/n
MD,
One hundred consecutive Biomet modular shoulder arthroplasties were studied prospectively and were evaluated with a minimum 2-year follow-up [average 4 I months). Fifty-seven women and 43 men with an average age of 64 years were evaluated for pain, activities of daily living, range of motion, cost, and complications. Fourteen patients had undergone previous surgery to the shoulder. Seventy patients underwent total shoulder arthroplasty, and thirty underwent hemiarthroplasty. Pain and range of motion demonstrated statistically significant improvement. Eight activities of daily living were rated on a 0 to 3 scale, and a// were significant/y improved. Complications were noted in I8 patients and included urinary retention, pulmonary embolus, rotator cuff tear, titanium synovitis, subluxation, and dislocation. Twelve shoulders underwent secondary procedures for rotator cuff repair, open reduction, and component revision for instability. Lucent lines were present in 62.5% of glenoids, 92.3% of cemented stems, and 0% of cementless stems on postoperative radiographs. No patients underwent revision surgery for component loosening, and no cases of humeral head-stem dissociation were seen. Ninety-five shoulders were rated by the patients as improved, and five were made worse. (J SHOULDER ELBOW SURG 1997;6:333-9.)
as introduced by Neer14, I5 Shoulder arthroplasty is an effective method of improving pain, function, and movement in patients with glenohumeral arthritis.” 4, *, “, l6 Recently interest has developed in modular shoulder arthroplasty systems offering the ability to interchange different humeral head sizes on different sized humeral stems. This allows the surgeon greater flexibility in matching the implant to the patient’s anatomy and obtaining a better fit. Publications concerning modular systems have been limited to their use in trauma.5 To date one report has described the results of modular shoulder arthroplasty in patients with primarily atraumatic causes of glenohumeral degeneration.8 The purpose of this report is to present our experience with a single modular shoulder arthroplasty
system (Biomodular Warsaw, Ind.).
Total Shoulder
System,
Biomet,
METHODS Between May 1988 and September 1992, 108 consecutive shoulder arthroplasties were studied prospectively. Eight patients were excluded because of inadequate follow-up. Four of these patients could not be located at the time of review, two were deceased, and two who had returned for their l-year evaluation could not return for the 2-year review. This left a group of 100 shoulders with an average follow-up of 5 1 months (range 41 to 96 months), who form the basis of this report. All procedures were performed by one surgeon (G. M. G.). Range of motion, function, and pain were recorded with a standardized scoring system.18 There were 52 women (4 bilateral) and 44 men who had an average age of 64 years (range 27 to 87 years) at the time of their index surgery. Preoperative diagnoses are listed in Table I. Fourteen patients had undergone previous surgery to their shoulder. Three had operative fixation of
333
334
Gartsman,
Russell,
Table
1 Preoperative
J. Shoulder Elbow July/August
48
14
arthritis
Acute trauma Avacular necrosis
12 9
Old trauma Cuff arthropathy Arthritis
Gaenslen
dlaqnosls
Osteoarthritis Rheumatoid
and
of recurrent
9 9 dislocation
1
fractures, three had previous hemiarthroplasty, and two each had acromioplasty, rotator cuff repair, and repair for shoulder dislocations, Preoperative radiographic analysis included an anterior-posterior view, an axillary lateral view, and a supraspinatus outlet view. Glenoid version and areas of posterior or anterior erosion were determined from the axillary radiograph. Retroversion or anteversion >5” was considered significant. Anterior-posterior and axillary lateral views were taken at the first postoperative visit, 6 months after surgery, and yearly thereafter. No fluoroscopic examinations of the shoulder4 were performed. Glenoid components were evaluated for potential radiographic evidence of loosening including the presence and progression of lucent lines around the keel, the presence of fracture lines within the cement mantle, and evidence of fracture or migration of the component. All glenoid components were cemented. Cemented humeral components were evaluated for potential radiographic evidence of component loosening including the presence and progression of lucent lines, the presence of fracture within the cement mantle, the development of osteolysis, and the presence of stem migration. In addition, radiographs were evaluated for the presence of stress shielding.6 Cementless stems were evaluated for potential radiographic evidence of loosening including the presence and progression of lucent lines, canal widening,7 the presence of osteolysis, and stem migration. In addition, cementless stems were also evaluated for potential signs of ingrowth including the absence of lucent lines, the presence of increased density or spot welds of endosteal new bone adjacent to the stem, the presence of pedestal formation beneath an otherwise stable stem, and evidence of stress shielding.7 The humeral stems were divided into seven zones analogous to the seven zones of the femoral stem as described by Gruen.9 The glenoid component was divided into eight radiographic zones based on a modification of the description of O’Driscoll.r7
Surg. I997
The surgical indications were pain and limitation of function interfering with activities of daily living associated with radiographic evidence of cartilage loss in the glenohumeral joint and unresponsive to conservative care, which consisted of activity modification and nonsteroidal antiinflammatory medications. Surgery was also indicated in patients with displaced three- and four-part fractures or fracture dislocations. Contraindications to surgery included recent infection of the glenohumeral joint, a neuropathic joint, or paralysis of the deltoid and rotator cuff. The surgical technique used has been previously described’, 4, 8, l6 and differs only in the variation required for the use of the modular humeral head. Once the humeral stem size was been selected, various sized humeral heads were then placed on the humeral shaft until the best combination of stability, mobility, and soft-tissue tension in the deltoid and rotator cuff was achieved. The appropriate humeral head was then impacted on to the shaft after checking that no soft-tissue ‘debris or fluid was present in the peg hole. The patient was started on passive range-ofmotion exercises on day 2, and therapy continued until the patient had 120” of elevation and 40” of external rotation. The patient was then discharged from the hospital. If no rotator cuff tear was performed, active assisted range of motion was started at 2 weeks. If a rotator cuff repair was performed, passive range of motion continued until 6 weeks, at which point active range of motion was started. Strengthening was started at 3 months. Patients were seen 2 weeks, 6 weeks, and 3, 6, 9, and 12 months after surgery. They were then seen at yearly intervals. At each yearly visit the patient completed a self-assessment questionnaire that included evaluation of activities of daily living and a pain scale. Range of motion was independently measure by a physical therapist. Radiographic assessment was made as described previously.
RESULTS Surgical findings. Sixteen (16%) patients had rotator cuff tears. The preoperative diagnosis and tear size are listed in Table II. Four were small (~1 cm), 2 were medium (~3 cm), and 10 were massive irreparable tears (>5 cm). The six small and medium tears were repaired after the prosthesis was inserted. The 10 irreparable tears were
/. Shoulder Elbow Volume 6, Number
Table
Gartsman,
Surg. 4
II Rotator cuff tears
Table
Russell,
Ill Acttvltles
Osteoarthritis Rheumatoid AVN
1 arthritis
Cuff arthopathy Acute trauma Arthritis of recurrent
AVN.
c3cm
>5cm
1
2 1
dislocation
Dress
1.18
0.52 0.89
2.50 2 28
behind
back
7
Reach high shelf Lift 10 pounds above shoulder Work
Avascular
of datlv hvlna
Sleep Reach Toilet Comb
1
335
Postoperative
2 2 1
Gaenslen
Preoperative
Size Diagnosis
and
1 42 hair
0 80 0 37 0.20 0 80
1.55
2 64 2 27 1 60 1 40
2 28
necr0.w
treated with rotator cuff debridement and hemiarthroplasty. Five patients had significant alteration of glenoid version such that changes in humeral version were required to improve intraoperative stability. Four patients with osteoarthritis had posterior glenoid erosion and required leveling of the glenoid with a reamer. The resulting level glenoids were still retroverted an average of 7” (range 5” to 10’). The four patients with retroverted glenoids were treated by alterations in the humeral osteotomy. The humeral component was placed in less retroversion so that the combined humeral-glenoid retroversion was 40”. All were believed to be stable at the time of subscapularis closure. One patient with arthritis caused by recurrent dislocation had anterior glenoid erosion measuring 10”. This patient was also treated with a modified humeral osteotomy, which placed the humeral component in more retroversion. This procedure allowed intraoperative component stability to be achieved. In no patient was a glenoid bone graft required. Hemiarthroplasty was performed in 30 shoulders, and 70 patients had humeral and glenoid components inserted. The indications for hemiarthroplasty were normal glenoid cartilage such as seen in avascular necrosis and acute trauma, insufficient bone stock (rheumatoid arthritis), or an irreparable rotator cuff tear. The humeral component was press-fitted in 69 cases and cemented in 31. The indications for cement were failure to achieve a firm press fit because of inadequate bone stock in the proximal humerus or in cases of acute trauma requiring the humeral prosthesis to be placed in a superior or “proud” position. Varying sizes of humeral stem and humeral head implants were used. Stem size 6 was used in all 1 1, size 7 in 16, size 9 in 32, size 1 1 in 38,
and size 13 in 3. Head size 40 x 15 was used in 20 shoulders, head size 40 x 20 in 18, size 44 x 17in22,44x22in30,and48x24in 10.A standard sized glenoid component was used in all cases. Pain. Pain was assessed by the patient on an analog pain scale that rated pain from 0 (no pain) to 10 (pain as bad as it can be]. Preoperative pain averaged 8.1, and postoperative pain averaged 2.9. These results were significant at p < 0.0001 with the sign test. Ninety-one of 100 shoulders showed improvement, 7 showed no change, and 2 showed worsening. Range of motion. Range of motion was measured in three planes: elevation, external rotation, and internal rotation behind the back. Elevation increased from an average preoperative measurement of 82” to an average of 129” after surgery. Average external rotation improved from 16” to 55”. Average internal rotations changed from the sacrum to T12. All increases were significant at p < 0.0001 with the paired t test. Elevation mean difference increased 47 2 4.5, T = 10.28. External rotation mean difference increased 39 + 2.8, T = 14.16. Internal rotation mean difference increased 6.5 vertebral levels -C 0.5 increments, T = 13.52. Function. Eight routine activities of daily living were self-assessed by the patient before surgery and at last follow-up and are listed in Table III. All activities of daily living demonstrated a statistically significant increase with p < 0.0001 with the exception of reaching behind the back (p < 0.001). Subjective response of the patient. Patients were asked on the questionnaire at last follow-up whether their shoulder was improved, the same, or worse after their surgery. Ninety-five (95%) believed their shoulder was improved, and
336
Gartsman,
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5 (5%) believed their shoulder was worse. Patients were also asked whether they would have the surgery again if they knew the end result. Ninety (90%) believed they would have the surgery again, and 10 (10%) believed they would not have the surgery performed. Radiographic evaluation. A maior limitation of the study was the number of radiographs available for review. Radiographs were included for analysis only if sequential films were of sufficient quality and allowed reproducible evaluation of the criteria described previously. Therefore only 24 glenoid components and 41 humeral stems were analyzed. In the immediate postoperative period eight glenoids demonstrated complete lucent lines, seven, incomplete lines, and nine, no lucent lines. At final follow-up complete lucent lines were noted in 20 prostheses, incomplete lines in 3, and 1 demonstrated no lucency. Progression of the lucent lines was noted in 18. There was no tendency for the lucent lines to develop in any particular zone around the glenoid, and no lucent lines were between the stem and the cement. Cement fracture was noted in five. There were no glenoid component fractures. Glenoid migration was noted in five shoulders. Two patients were revised for glenohumeral dislocation. Three patients with glenoid migration were doing satisfactorily. One patient was believed to have symptoms from glenoid loosening and underwent revision for glenoid loosening. The loose glenoid was documented with arthroscopy. The glenoid was removed at open operation. Thirteen shoulders with cemented stems were analyzed. Analysis demonstrated that in the immediate postoperative period 5 (38.5%) of 13 showed complete lucent lines, 7 (53.8%) of 13 showed incomplete lucent lines, and one showed no lucent lines. At final follow-up 6 (46.2%) of 13) cemented stems showed complete lucent lines, 7 (53.8%) of 13 s h owed incomplete lucent lines, and no stems were free of lucent lines. There was no tendency for lucent lines to develop in any particular zone around the stem. Cement fracture was noted in 2 of 13 shoulders. Stem migration occurred in one shoulder. Osteolysis was seen in 4 of 13 stems at an average of 23 months. The one radiographic parameter suggestive of stem stability, stress shielding, was present in 6 of 13 patients beginning an average of 25 months after surgery. Twenty-eight noncemented stems were analyzed in the immediate postoperative period, and none
J. Shoulder Elbow Surg. July/August 1997
showed any lucent lines. At final follow-up none demonstrated a complete lucent line, 3 (10.7%) of 28 showed an incomplete lucent line, and 25 (89.3%) of 28 continued to show no lucent line formation. One stem showed 2 mm of distal migration in the first 6 months but was stable thereafter. Osteolysis was not demonstrated around any stem. Radiographic evidence of increased density or “spot welding” was present in 17 (60.7%) of 28 stems and was present beginning at an average of 18 months after surgery. Sclerosis was most common at the medial and lateral distal aspect of the stem just proximal to the tip. Radiographic evidence of stress shielding was present in 17 (60.7%) of 28 stems beginning at an average of 32 months after surgery. Evidence of stress shielding was most notable in the proximal lateral portions of the humerus. Pedestal formation developed at the tip in 13 (46.2%) of 28 stems that were by other parameters also radiographically stable. This finding was first seen at an average of 25 months after surgery. Complications. Complications occurred in 18 (18%) of the shoulder arthroplasties and are listed in Table IV. No intraoperative complications occurred. One patient had urinary retention after surgery and required transurethral prostatic resection. One patient had a pulmonary embolus 2 days after discharge and required hospitalization and anticoagulation. Two patients had traumatic episodes. One patient had a rotator cuff tear after falling from a ladder and required a rotator cuff repair. One patient was involved in an automobile accident and sustained bilateral fractured femurs and tibias. She dislocated her glenoid component and required glenoid component removal. One patient had persistent wound drainage. He was returned to the operating room on the fourth postoperative day, and the wound was irrigated. The patient did well and required no further surgery. One musculocutaneous nerve palsy resolved completely by the sixth postoperative week. One patient had titanium synovitis; she required humeral head and glenoid revision. The well-fixed humeral stem was left in place. Glenohumeral instability was the source of the greatest number of complications. Recurrent anterior dislocation developed in three patients, all of whom had rheumatoid arthritis. All were pleased with their shoulder function and level of pain and did not desire revision. Superior-anterior dislocation was seen in two patients with cuff arthropathy
1. Shoulder Elbow Volume 6, Number
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Russell, and Gaenslen
337
Table IV Compllcatlons Type
Number
Complication
Diagnosis
Surgery required
Systemic
1 1
Urinary retention Pulmonary embolus
OA post-traumatic
Wound Trauma
1 1 1
Drainage Rotator cuff
post-traumatic AVN
Yes
RA OA
Yes No Yes
Nerve
1
Prosthetic InstabIlity
1
Nerve 3
5
3
tear
Glenoid dislocation Musculucutaneous
No No Yes
palsy
Titanlum Superior
synovitis medial
instabillty
OA OA
Superior
medial
Instability
Cuff
arthropathy
Superior Posterior
medlal instability subluxation
Cuff OA
arthropathy
Posterior Posterior
dislocation dislocation
OA OA
Posterior Posterior
dislocation dislocation
Anterior Anterior
dislocation dislocation
OA OA RA
Anterlor
dislocation
and one patient with osteoarthritis. One patient with rotator cuff arthropathy had good relief of pain and adequate below-shoulder level function and did not desire further surgery. The other two had symptoms and underwent revision as described in the following text. Five patients with osteoarthritis had posterior instability. Posterior subluxation was noted in one patient. Elevation was limited to 9O”, but the patient had painless below-shoulder activity and did not desire further surgery. Four patients had posterior dislocation of the humeral head. One patient had elevation to 80” but was satisfied with his shoulder. Three others were not satisfied and underwent revision as described in the following text. At the time of their index surgery all five patients had posterior glenoid erosion and posterior humeral head subluxation noted on the axillary radiograph. Decreased external rotation was documented at the examination with the patient under anesthesia (average 14”). The glenoid was reamed so that a level surface resulted. As noted previously, some glenoid retroversion remained, averaging 7” (range 5” to 10’). Soft-tissue balancing was accomplished by placing the humeral component in 5” to 10” less retroversion; the appropriate humeral head size was selected for the best combination of mobility and stability, and enough subscapularis mobility was gained to achieve 45” external rotation. All patients were believed to be stable at the conclu-
RA RA
sion of their postoperative
Yes Yes No No No Yes Yes Yes No No No
index surgery, and in no case was bracing or casting used. Failures and Revision Surgery. Ten (10%) shoulders underwent revision surgery of their shoulder. The two patients with injuries had sustained sufficient trauma so that it was reasonable to assume the injury was the cause of the shoulder problem. The patient with the traumatic rotator cuff tear and rotator cuff repair never regained satisfactory, above-shoulder level use of the arm, although pain has been controlled and she is able to use the arm for below-shoulder level activities without difficulty. The patient with the dislocated glenoid component was converted to a hemiarthroplasty with good shoulder function. The patient with wound drainage did not have an infection in the shoulder, and 6 years after surgery she has evidence of radiographic lucency. Early Biomet humeral head prostheses were titanium, and one patient as described previously had titanium synovitis and required revision. At surgery a proliferative blackened synovium was noted. One patient developed shoulder pain six years after operation. Arthroscopy demonstrated a loose glenoid that was removed, and the patient was given a hemiarthroplasty. Glenohumeral instability accounted for the other five revision procedures. Two patients, one with osteoarthritis and one with rotator cuff arthropathy, had anterosuperior dislocation of the prosthesis
338
Gartsman,
Russell, and Gaenslen
and required revision. Both patients had undergone a coracoacromial ligament resection and hemiarthroplasty at the time of their index surgery. One patient with rotator cuff arthropathy was revised to a larger humeral head size, and the prosthesis was placed in an additional 20” of retroversion. He continued to dislocate anterosuperiorly and was unsatisfied with his end result. One patient with osteoarthritis and a normal rotator cuff was revised in a similar fashion with a similar end result. Three patients with posterior instability (one subluxation, two dislocations) required revision surgery. One patient with a total shoulder replacement had the humeral head converted to a smaller size and did well with no recurrence of instability and good shoulder function. Another patient with a total shoulder arthroplasty had the humeral stem changed and reinserted in 15” more anteversion with a smaller sized humeral head. He continued to have recurrent posterior dislocation and had a poor result. He declined further surgery. One patient with a total shoulder replacement had removal of the glenoid and a larger size humeral head inserted. He did well with no recurrence of instability and good shoulder function.
DISCUSSION The success of nonmodular shoulder arthroplasty has been noted by Neer,16 Cofield,4 and Barrett.’ FenlinE has reported his results with a modular shoulder system. This report serves to document similar improvements in range of motion, function, and pain after modular shoulder arthroplasty. Patient satisfaction is high. No complications (humeral head-stem dissociation) occurred that can be related to the modular system. The theoretic advantages of a modular shoulder arthroplasty system include increased number of humeral head-stem combinations to better adjust soft-tissue tension,‘O the ability to more easily insert a glenoid component following hemiarthroand the ability to replace a humeral head plasty, ’ 9 at a later date to address problems of instability or humeral head wear. In this series 50% of all patients had humeral head sizes other than the standard 15 and 22 mm head sizes that existed in the Neer nonmodular system. Therefore at the time of surgery it was our opinion that half of the patients were better served by a modular system that allowed the surgeon increased flexibility in matching component size to the bone and softtissue anatomy. What we cannot demonstrate is
J. Shoulder Elbow Surg. July/August I997
that the increased number of choices resulted in an improved result. It is intuitively obvious that glenoid revision or conversion of a hemiarthroplasty to a total shoulder arthroplasty is easier with a modular than a nonmodular system. A modular head can be removed, the glenoid adequately exposed and prepared, and a glenoid inserted without the difficulty of humeral stem removal. However, in this series no glenoids were replaced for symptomatic loosening, and no hemiarthroplasties developed symptoms such that conversion to a total shoulder arthroplasty was advised. Two patients required humeral stem version changes, and modularity did appear beneficial because it allowed access to the stem-bone interface and attachment of a stemextracting device. With regard to the management of instability in two additional patients, modularity was beneficial. One patient was successfully treated with humeral head exchange and a smaller head size, and one patient had the humeral head and glenoid removed and a large-sized head implant inserted. Neither of these patients required stem revision, significantly decreasing the complexity of the procedure. Whether the benefits that were apparent in these four shoulders justify the use of a modular system in the other 96 is not answerable in this study and will depend on further reports that evaluate patient outcome and cost comparing modular and nonmodular systems. There are of course theoretic and actual disadvantages to modularity in shoulder arthroplasty. Although no cases of humeral head dissociation occurred, Blevins3 reported that 13 clinical dissociations of the Morse taper design used in this series have occurred. They suggested that allowing fluid or blood into the “reverse” Morse taper and the resulting weakening of pull-off strength may be a causative factor. However, Loch12 has presented data to suggest that the axial taper junction is not weakened if wet. Some degree of separation must exist between the humeral stem and head in a modular system. In theory this may result in a decreased head size and arc available for motion and stability.13 Cost is another factor that must be considered. The current list price for Biomet’s Biomodular prostheses (humeral stem, humeral head, and glenoid) is $1966, whereas the DuPuy Global price is $3665. This is compared with the nonmodular systems such as the Neer at $1092 and the Global at $1385. The design features of the humeral prosthesis
/ Shoulder Elbow Volume 6, Number
Gartsman,
Surg. 4
used in this series allow for cementless insertion of a humeral stem with an ingrowth surface in the proximal portion of the stem. However, ingrowth surfaces have unproved value in the humerus. Aseptic loosening appears to be infrequent, and strategies to avoid loosening seem to be less important than in the glenoid or in other joints. Humeral stem revision is more commonly performed for glenohumeral instability, component malposition, or infection. The excellent fixation provided by the cementless stem may make stem removal difficult, increasing the risk of humeral fracture or perforation. The orthopedic literature contains numerous articles dealing with the potential problems of implant design and fixation. Barrett’ reported a 14% incidence of glenoid loosening 14 to 44 months after surgery. All seven patients were noted to have a massive tear of the rotator cuff at the time of the index operation. Our 1% incidence of symptomatic glenoid loosening may represent better implant design but more likely simply reflects the orthopedic community’s increased understanding of shoulder kinematics. In this series massive rotator cuff tears were a contraindication to glenoid placement, and those patients with massive rotator cuff tears were treated with hemiarthroplasty without insertion of a glenoid component. Although humeral stem loosening remains a concern, in this series only one patient had radiographic evidence of humeral stem movement (2 mm), and no patient underwent revision surgery for humeral stem loosening. We found that lucent lines are extremely common around the cemented humeral and glenoid components after shoulder arthroplasty. The presence of lucent lines, however, is not necessarily a poor prognostic sign and is usually associated with stable fixation. We also found that cementless humeral stems show intermediate term radiographic stability with minimal development of Iucent lines, moderate development of sclerosis adjacent to the stem, and moderate evidence of stress shielding. Radiographic evidence of bony attachment to the prosthesis was most common at the endosteal bone surfaces adjacent to the distal stem rather than from the cancellous bone adjacent to the proximal porous coating of the humeral stem. The complication most frequently affecting patient outcome was glenohumeral instability after arthroplasty. Glenohumeral instability surgery has been documented as a cause of shoulder arthritis requiring arthroplasty2 but not as a result of shoul-
Russell, and Gaenslen
339
der arthroplasty. This complication occurred despite careful attention to soft-tissue balance, implant selection, and postoperative rehabilitation and serves to emphasize the complexity of shoulder arthroplasty.
REFERENCES 1
Barrett CVP, Fror~i IlnJl,Jack~ns SE, Wvss CR, Ma&n sho~~lder orthroplasb J Bone Jnlnt Sury Arl 1387 72
FA Total 63 865
2
3
4
C<,fleld RH Totol st~oultler arthrc+std j,< J Brine Jc’ln+ Sur’3 4m 1384 66
with the i‘leer 8QQQ@6
5
Dines acute
6
Erlgh CA Bobvn JD Glownon AH P~JI~ws-cnated hip replocement thr foctnrs gsxernlng bone Ingr’I*th stress sh& ~ng qnd cllnlcol results J Bone Jn~nt Surg Am 1987 69 4.5 55
7
Engh CA fiflassln P, Suthers kE Roentgenogrophlc. obsessmerit %,f the b~olog~z fl*oilon ot porous-surfrlcc compownts Cl11 (LIlthop 1990 257 107~28
8
F&n JM, P~~msey Ml, Allordycx rJ, Brlormon BG ~fl~~dulor total \ha~Jldrr replacement desl’zn ro!~~xol~ ~ndxat~o~s and r&ts Clan @rlhop 1994.07 3?~46
9
GrlJrn TA, Mcr\jlecp c*mented stem~b?pe ~nal\ws of Iwwnlng
DM. l,Vonen PF iL’~odulo~ shoulder froctl.tres Clan Orthop 1994,307
prosthe-
hem~nlthruplos~ i 8 26
fe?r
Gn”, P.mstutz HC p”lodes of tallure fsm,:~rol components A rad;ogrophlc Cllr Orthnp 19i9,14 1 17-29
of
10
Holrymar DT. Sidles Jb,, Harris Sl LIppItt 5B. motseri FA The eifect #If ~rt~color corlformlp/ and the we of the humerol head #:ornpnwnt f3n IOYI~~ nnd motion oft?, glenohumwal nrthropla+J J Bone Joint SIJI!J Arr~ 190.577 555 63
11
Hov~I~ns RJ. Bell PH J~>Ilay B Tot01 shoulder Qithi>p 1’389 242 188-93
12
loch DA, Glwsx PF b yle JE Bwhtc,l D strength ot dry rind \wt taper head connectIons shoulder prwthzx Trans OPS 1’994, 19 826
13
bhotsen FA. llpplti SB Sidles JA How/man DT Mechanlrs of glenohunwol orthraplosty In Proctlcal evaluotlirn and mom ogement rit the shoulder Ph~ludelptl~a C’VB Sounders, 1094 201
14
rJPerSS Jrirrt
arthroplasb
krt~culur lqlocement fc?r ihe hurnelal Surg Am 1955 37 2 15-28
AvIal pull-off w o Inodular
hend
15
New CS RepIncement J Bone J>lnt SUIT Arrl
16
t\leer CS, bl/atson KC Stanton FJ Recent experience sholJder replacemwt J Bone jolnt SIJI~ Arr~ 1982.64 37
17
18
19
Clan
arthroplosty for glenohumProl 1974.56 1~1 3
J Bone arthritis In total 3 19-