Osteoarthritis of the trapeziometacarpal joint: The pathophysiology of articular cartilage degeneration. II. Articular wear patterns in the osteoarthritic joint An anatomic and radiographic study of the osteoarthritic trapeziometacarpaljoint was conducted on 27 surgical specimens harvested during basal joint arthroplasty. Surface wear patterns were analyzed by hyaline cartilage staining, and relative involvement of trapezium and metacarpal was calculated as the trapezium/metacarpal eburnation ratio. Eburnation occurred only on facing trapeziometacarpal surfaces in contact areas of the palmar compartment. Metacarpal degeneration began at the palmar joint margin adjacent to the beak ligament and extended dorsally, while trapezial degeneration originated on the central palmar slope and spread centrifugally with more advanced disease. Eburnation consistently involved a greater surface area on the trapezium than on the metacarpal in a ratio of nearly 3: 1. A decreasing trapezium/metacarpal eburnation ratio correlated closely with worsening radiographic stage. These observations suggest translation of metacarpal on trapezium in the production of arthritic surface lesions and support a hypothesis of pathologic joint instability as the cause of trapeziometacarpal osteoarthritis. (J HAND SURG 1991;16A:975-82.)
Vincent D. Pelligrini, Jr., MD, Rochester, N.Y.
Osteoarthritis of the trapeziometacarpal joint of the thumb is a disabling condition that can severely impair hand function; as such, it represents the most frequently operated focus in the osteoarthritic upper extremity. Of those seeking surgical treatment, postmenopausal women outnumber men by nearly 15 to l.
From the Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, Rochester, N.Y. Presented in part at the forty-third annual meeting of the American Society for Surgery of the Hand, Baltimore, Md., September 1988. This work was supported in part by funding from the American Society for Surgery of the Hand; Biomedical Research Support Grant RR5353 (Stanford University), National Institutes of Health; and Biomedical Research Support Grant R27213 (University of Rochester), National Institutes of Health. Received for publication Feb. 21, 1990; accepted in revised form Jan. 23, 1991. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Vincent D. Pellegrini. Jr., MD, Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Box 665, Rochester, NY 14642. 3/1128885
As with osteoarthritis in other joints, the cause of this condition remains unclear, but excessive ligamentous laxity and alterations in hormonal homeostasis are most frequently discussed as potential causative factors. 1.2 Empirical evidence suggests that stabilization of symptomatic hypermobile "prearthritic" joints by palmar ligamentous reconstruction retards the progression of degenerative osteoarthritis at the base of the thumb. 1. 2 Numerous other procedures have been described for prosthetic replacement of the trapeziometacarpal joint with advanced disease, the most functionally successful of which all include reconstruction of the stabilizing palmar ligamentous structures."? Beyond the frequent need for surgical reconstruction to alleviate pain and restore function, the trapeziometacarpal joint is endowed with a compact anatomy amenable to en bloc excision. In contrast with other joints currently reconstructed with prosthetic devices, reaming and resultant destruction of the diseased surfaces are not unavoidable in thumb basal joint surgery. While fragmentation and morsellization admittedly facilitate surgical debridement of the joint, the articular surfaces may alternatively be preserved intact for later study by en bloc removal of the trapezium and metaTHE JOURNAL OF HAND SURGERY
975
The Journal of
976
Pellegrini
HAND SURGERY
Table 1. Articular surface eburnation ratios and radiographic stage of osteoarthritis Specimen No.
I 2 3 4
5 6 7 8 9 10
II 12 13 14 15 16 17
18 19 20 21 22 23 24 25 26 27
Trapezium lI'ear eburnation ('70)
Metacarpal wear eburnation ('70)
Trap/Me eburnation
X-ray stage
54 62
42 28 46 56 47 30 14
1.29 2.21 1.39 1.38 1.21 1.60 2.36 3.36 2.00 2.67 1.24 .81 1.52 1.80 1.66 1.80 .84 1.88 1.70
IV
64 77
57 48 33 37 6 16 88 58 57 53 69 88 41 65 58 78 41 62 67 55 85 49 61
carpal base during reconstructive procedures. These epidemiologic and anatomic facts combine to make the trapeziometacarpal joint uniquely suited for study of the pathophysiology of osteoarthritis. In consideration of the previously described articular degeneration in the aging joint, the pathologic change of the symptomatic trapeziometacarpal j?int is herein investigated.
Materials and methods .. Articular surfaces from 27 patients were removed intact at the time of surgical arthroplasty for treatment of end-stage trapeziometacarpal osteoarthritis. Indication for operation was pain that interfered with daily function and that was refractory to splinting, thenar strengthening exercises, and nonsteroidal antiinflammatory medication. The trapezium was removed en bloc to include its four articular facets, and an osteotomy and resection of the metacarpal base was performed to include the entire articular surface with the trapezium. During the process of removal, all capsuloligamentous structures were sharply detached from the bony specimens. The dorsal margin of each surface was marked
II 3 6 71 72
37 29 42 49 48 35 34 75 26 38 54 17 77
25 59
1.04
1.58 1.63 1.24 3.25 1.11 1.94 1.05
III III
IV IV III III III III III
IV IV IV IV IV III
IV III
IV IV IV III
IV III
IV IV IV
with a rongeur, and specimens were stored in liquid nitrogen until the time of study. The integrity of the articular surface was analyzed by direct gross inspection and by staining with a methylene blue-based dye (Diff-Quik, American Scientific Products, McGaw Park, III.) with affinity for hyaline cartilage. In this way the surface material was characterized as being normal, affected by chondromalacia with pitting and softened texture, or eburnated with complete absence of stainable hyaline cartilage. All specimens were photographed before and after staining, and surface wear patterns were digitized from the photographic records. Respective areas of eburnation and residual articular cartilage were computed as a percentage of the tolal available joint surface area to account for variability in size and shape of each trapezium and metacarpal bone. The percentage of surface wear on trapezium and metacarpal was compared for each joint, and the ratio of trapezium to metacarpal eburnation was computed (Table I). This trapezium/metacarpal eburnation (TME) ratio, in turn, allowed comparison among all
Vol. 16A, No.6 November 1991
Osteoarthritis of trapezlom etacarpal joint , 1/
,
/
E
J
r
E
/
DP
I
~
/
C V'
./
~
Fig. 1. Trapeziornetacarpal specimens remo ved at time of basal joint arthroplasty; en bloc trapezium (TR) and articular surface from metacarpal (MC) base. A, Articulated specimen; right thumb as
viewed from ulnar aspect and index metacarpal facet (single arrow) demonstrating dorsal metacarpal overhang in noncontact zone (double arro lVs). B, and C, Facing articular surfaces, me tacarpal left and trapezium right, demonstrating palmar eburnation (E. double arroll's) and preser vation of dorsal cartilage (cho ndromalacia, C. single arrolVs) . The metacarpal specimen has dorsal cartilage with pitted appearance (single arrows} and glossy palmar eburnation (double arroU's) in well-demarcated zones (brok en lines) . The trapezium is marked by glossy eburnation of nearly the ent ire surface (double arro\\'s) and a thin dorsal rim of pitted articular cartilage (single arro\ I's).
977
978
The Journal of HAND SURGERY
Pellegrini
A
et llcarpal
ElIr1y Oi sease --------T rapezi um
•
t acarpa1 ear 14:: i rapl C
B
--
Eburnat i on C a r t i 1 a~
. onar t i c l ar
Fig. 2. Idiopathic basal joint arthritis with early eburnation. Surfaces portrayed as right thumb with metacarpal on left, trapezium on right, and adjacent areas representing the palmar compartment. A, Stained surgical specimen; pale-staining areas of palmar eburnation (single arroll's) adjacent to palmar beak ligament attachment. B, Digitized wear areas with trapezium/metacarpal ratio of relative wear; black indicates regions of retained articular cartilage. C, Preoperative stress radiographs of the same patient, stage III.
joint specimens for the purpose of defining a spectrum of disease severity. Furthermore, radiographic disease stage, as initially defined by Eaton and Littler,' was correlated with the TME ratio to assess the efficacy of radiographic staging as an indicator of pathologic change in the joint. Preoperative stress radiographs demonstrated stage III disease in 40% and stage IV disease in 60% of the surgically treated thumbs that provided specimens for study.
Results Initial intraoperative observations correlated poorly with study of the articular surface after freezing or stain-
ing. Synovial fluid coating the joint surface gave a smooth, shiny appearance to the eburnated region and served only to camouflage the dulled appearance of chondromalacia in the dorsal compartment (Fig. 1). However, subsequent staining of the surfaces highlighted the areas containing hyaline cartilage and facilitated recognition of the eburnated areas that were devoid of any stainable material. A predictable pattern of localized eburnation appeared on the facing surfaces of both trapezium and metacarpal bones. Metacarpal surface degeneration originated at the peripheral margin adjacent to the palmar beak ligament attachment in the palmar joint com-
Vol. 16A. No.6 November 1991
Ost eoarthritis of trapeziometacarpal joint, Jl
.He Di sease
, t aca r;la1- -
--
-
979
Tr apez . U'li
•
!"
t aca rpal
ea r
461
Tr ap/~C ~d
B
i rapez1um Mea r 10 . 39
64%
---.: Eb rnatio
_
Cart il age 0'1 rt1c l a r
Fig. 3. Idiopathic basal joint arthritis with advanced eburnation . Surfaces portrayed as right thumb with metacarpal on left, trapezium on right, and adjacent areas representing the palmar compartment. A, Stained surgical specimen; extensive pale areas of eburnation (single arrows) involve nearly entire trapezium. B, Digitized wear areas with trapezium/metacarpal ratio of relative wear; black indicates regions of retained articular cartilage. C, Preoperative stress radiograph of the same patient, stage IV.
partment (Fig. 2). More extensive disease was characterized by dorsal enlargement of the involved area toward the center of the metacarpal joint surface (Figs. 3 and 4) . Eburnation of the facing trapezial surface was more centrally located on the palmarly inclined slope of the trapezial saddle but remained concentrated within the palmar joint compartment (Fig. 2). More extensive involvement of the trapezium was characterized by concentric enlargement of this palmar compartment focus of eburnation (Figs. 3 and 4) . Stainable articular cartilage was always absent from the palmar compartment metacarpal surface and was most consi stently noted in joints with advanced disease on the dorsal compartment
surface of the metacarpal. Indeed , in those joints with the most severe disease, staining consi stently showed that the dorsal compartment contained the only remaining articular cartilage in the joint. Both the absolute and fractional areas of each surface eburnated and worn to subchondral bone were consistently greater on the trapezium than on the metacarpal. In less extensively involved joints, a small region of eburnation along the palmar margin of the metacarpal beak, always adjacent to the beak ligament attachment, was matched with an area of eburnation as much as three times greater on the trapezial surface (Fig. 2). In joints with more advanced disease (Fig. 3), a relatively
The Journal of
980
Pellegrini
HAND SURGERY
Fig. 4. Idiopathic basal joint arthritis with end-stage eburnation. Surfaces portrayed as right thumb with metacarpal on left, trapezium on right, and adjacent areas representing the palmar compartment. A, Stained surgical specimen; extensive pale areas of eburnation (single arrows) involve entire trapezium and spare only the dorsal noncontact zone of the metacarpal. Note prominent trapezial osteophyte (double arrows) along palmar margin of eburnated surface. B, Preoperative stress radiograph of the same patient, stage IV.
greater percentage of the metacarpal surface was eburnated and the ratio of trapezial to metacarpal wear approached unity (Fig. 5). Injoints with end-stage disease and functional ankylosis, prominent osteophytes obscured articular margins and nearly the entire surfaces of both trapezium and metacarpal were eburnated (Fig. 4). Remaining articular cartilage in the dorsal com-
partment of the joint was characterized by gross changes of pitting and softening with a dulled appearance to the joint surface (Fig. I, B and C). Radiographic stage was closely correlated with the TME ratio. The mean ratio of 2.20 (standard error of the mean, 0.20) for 11 thumbs with radiographic stage III disease compared favorably with a mean ratio of
Vol. 16A. No.6 November 1991
Osteoarthritis of trapeziom etacarpal joint, /I
981
RELATIVE TRAPEZIUM AND METACARPAL JO I NT SURF ACE WEAR
100
80
...., u
):
60
~
u
I:
40
20 [J
0 0
20
40
60
80
100
TRAP W; Wear Fig. 5. Relative trapezial and metacarpal joint surface wear. Increasing disease severity results in nearly total and symmetrical eburnation of both trapezial and metacarpal surfaces. with wear ratios approaching unity.
1.34 (standard error of the mean, 0.08) for 16 thumbs with radiographic stage IV disease (Fi g. 6); the difference was statistically significant at p < 0.00 I. Total or near complete loss of joint space, marginal ridging or osteophyte formation, and subchondral sclerosis characterized stage IV radiographs and predicted the most ext ensive disease, with TME ratios approaching unity. Discussion Surgical specimens removed at the time of basal joint arthroplasty in patients with stage III or stage IV radiographic disease exhibited a pattern of wear similar to that found in postmortem material. Eburnation suggesting severe articular disea se was present in all patients and occurred only in the palmar compartment. Only chondromalacia was observed in the.dorsal compartment; indeed , in those specimens with the most severe disease, the dorsal compartment contained the only remaining articular cartilage in the joint. This relatively uninvolved dorsal portion of the joint surface appeared to be a zone of frequent noncontact, as evidenced by examination of both stress radiographs and articulated surgical specimens (Fig. 1, A). Eburnation was consistently found over a greater articular surface area on the trapezium than on the metacarpal, in a ratio
as great as 3 : I in early disease and approaching unity in end-stage disease. This key observation implies translation of metacarpal on trapezium in order that a smaller area of wear (metacarpal) might imprint a larger area of wear on the facing surface (trapezium). Metacarpal wear was initially localized to the palmar perimeter adjacent to the beak ligament attachment and spread dorsoradially with increasing severity of disease. Trapezial wear began more centrally on the palmar slope and spread centrifugally with more advanced disease. Ultimately, as the disease becomes more severe, the TME ratio approaches unity and both joint surfaces are involved in a total pattern of eburnation characterized by prominent marginal osteophytes. The end-stage specimen offers little insight into etiology compared to the joint less overcome by eburnation , which again suggests a scenario of cartil age degeneration in joint contact areas caused by translation of metacarpal on trapezium. This configuration of palm ar compartment surface wear corresponds to the known contact areas in the trapeziometacarpaljoint produced by flexion-adduction of the thumb ray while the joint is functionally loaded during lateral pinch." Such a contact pattern would be expected to enlarge in the presence of an incompetent pal-
982
The Journal of HAND SURGERY
Pellegrini
CORRELATION OF RADIOGRAPHIC STAGE AND PATHOLOGIC WEAR 3.0
5! ~ -e
2.5
-e
2.0
IX IX ~
p < .001 ·2.20
>
u I:
"A-
Vincent D. Pelligrini, Jr., MD, Rochester, N.Y.
Osteoarthritis of the trapeziometacarpal joint of the thumb is a disabling condition that can severely impair hand function; as such, it represents the most frequently operated focus in the osteoarthritic upper extremity. Of those seeking surgical treatment, postmenopausal women outnumber men by nearly 15 to l.
From the Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, Rochester, N.Y. Presented in part at the forty-third annual meeting of the American Society for Surgery of the Hand, Baltimore, Md., September 1988. This work was supported in part by funding from the American Society for Surgery of the Hand; Biomedical Research Support Grant RR5353 (Stanford University), National Institutes of Health; and Biomedical Research Support Grant R27213 (University of Rochester), National Institutes of Health. Received for publication Feb. 21, 1990; accepted in revised form Jan. 23, 1991. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Vincent D. Pellegrini. Jr., MD, Department of Orthopaedics, University of Rochester School of Medicine and Dentistry, 601 Elmwood Ave., Box 665, Rochester, NY 14642. 3/1128885
As with osteoarthritis in other joints, the cause of this condition remains unclear, but excessive ligamentous laxity and alterations in hormonal homeostasis are most frequently discussed as potential causative factors. 1.2 Empirical evidence suggests that stabilization of symptomatic hypermobile "prearthritic" joints by palmar ligamentous reconstruction retards the progression of degenerative osteoarthritis at the base of the thumb. 1. 2 Numerous other procedures have been described for prosthetic replacement of the trapeziometacarpal joint with advanced disease, the most functionally successful of which all include reconstruction of the stabilizing palmar ligamentous structures."? Beyond the frequent need for surgical reconstruction to alleviate pain and restore function, the trapeziometacarpal joint is endowed with a compact anatomy amenable to en bloc excision. In contrast with other joints currently reconstructed with prosthetic devices, reaming and resultant destruction of the diseased surfaces are not unavoidable in thumb basal joint surgery. While fragmentation and morsellization admittedly facilitate surgical debridement of the joint, the articular surfaces may alternatively be preserved intact for later study by en bloc removal of the trapezium and metaTHE JOURNAL OF HAND SURGERY
975
The Journal of
976
Pellegrini
HAND SURGERY
Table 1. Articular surface eburnation ratios and radiographic stage of osteoarthritis Specimen No.
I 2 3 4
5 6 7 8 9 10
II 12 13 14 15 16 17
18 19 20 21 22 23 24 25 26 27
Trapezium lI'ear eburnation ('70)
Metacarpal wear eburnation ('70)
Trap/Me eburnation
X-ray stage
54 62
42 28 46 56 47 30 14
1.29 2.21 1.39 1.38 1.21 1.60 2.36 3.36 2.00 2.67 1.24 .81 1.52 1.80 1.66 1.80 .84 1.88 1.70
IV
64 77
57 48 33 37 6 16 88 58 57 53 69 88 41 65 58 78 41 62 67 55 85 49 61
carpal base during reconstructive procedures. These epidemiologic and anatomic facts combine to make the trapeziometacarpal joint uniquely suited for study of the pathophysiology of osteoarthritis. In consideration of the previously described articular degeneration in the aging joint, the pathologic change of the symptomatic trapeziometacarpal j?int is herein investigated.
Materials and methods .. Articular surfaces from 27 patients were removed intact at the time of surgical arthroplasty for treatment of end-stage trapeziometacarpal osteoarthritis. Indication for operation was pain that interfered with daily function and that was refractory to splinting, thenar strengthening exercises, and nonsteroidal antiinflammatory medication. The trapezium was removed en bloc to include its four articular facets, and an osteotomy and resection of the metacarpal base was performed to include the entire articular surface with the trapezium. During the process of removal, all capsuloligamentous structures were sharply detached from the bony specimens. The dorsal margin of each surface was marked
II 3 6 71 72
37 29 42 49 48 35 34 75 26 38 54 17 77
25 59
1.04
1.58 1.63 1.24 3.25 1.11 1.94 1.05
III III
IV IV III III III III III
IV IV IV IV IV III
IV III
IV IV IV III
IV III
IV IV IV
with a rongeur, and specimens were stored in liquid nitrogen until the time of study. The integrity of the articular surface was analyzed by direct gross inspection and by staining with a methylene blue-based dye (Diff-Quik, American Scientific Products, McGaw Park, III.) with affinity for hyaline cartilage. In this way the surface material was characterized as being normal, affected by chondromalacia with pitting and softened texture, or eburnated with complete absence of stainable hyaline cartilage. All specimens were photographed before and after staining, and surface wear patterns were digitized from the photographic records. Respective areas of eburnation and residual articular cartilage were computed as a percentage of the tolal available joint surface area to account for variability in size and shape of each trapezium and metacarpal bone. The percentage of surface wear on trapezium and metacarpal was compared for each joint, and the ratio of trapezium to metacarpal eburnation was computed (Table I). This trapezium/metacarpal eburnation (TME) ratio, in turn, allowed comparison among all
Vol. 16A, No.6 November 1991
Osteoarthritis of trapezlom etacarpal joint , 1/
,
/
E
J
r
E
/
DP
I
~
/
C V'
./
~
Fig. 1. Trapeziornetacarpal specimens remo ved at time of basal joint arthroplasty; en bloc trapezium (TR) and articular surface from metacarpal (MC) base. A, Articulated specimen; right thumb as
viewed from ulnar aspect and index metacarpal facet (single arrow) demonstrating dorsal metacarpal overhang in noncontact zone (double arro lVs). B, and C, Facing articular surfaces, me tacarpal left and trapezium right, demonstrating palmar eburnation (E. double arroll's) and preser vation of dorsal cartilage (cho ndromalacia, C. single arrolVs) . The metacarpal specimen has dorsal cartilage with pitted appearance (single arrows} and glossy palmar eburnation (double arroU's) in well-demarcated zones (brok en lines) . The trapezium is marked by glossy eburnation of nearly the ent ire surface (double arro\\'s) and a thin dorsal rim of pitted articular cartilage (single arro\ I's).
977
978
The Journal of HAND SURGERY
Pellegrini
A
et llcarpal
ElIr1y Oi sease --------T rapezi um
•
t acarpa1 ear 14:: i rapl C
B
--
Eburnat i on C a r t i 1 a~
. onar t i c l ar
Fig. 2. Idiopathic basal joint arthritis with early eburnation. Surfaces portrayed as right thumb with metacarpal on left, trapezium on right, and adjacent areas representing the palmar compartment. A, Stained surgical specimen; pale-staining areas of palmar eburnation (single arroll's) adjacent to palmar beak ligament attachment. B, Digitized wear areas with trapezium/metacarpal ratio of relative wear; black indicates regions of retained articular cartilage. C, Preoperative stress radiographs of the same patient, stage III.
joint specimens for the purpose of defining a spectrum of disease severity. Furthermore, radiographic disease stage, as initially defined by Eaton and Littler,' was correlated with the TME ratio to assess the efficacy of radiographic staging as an indicator of pathologic change in the joint. Preoperative stress radiographs demonstrated stage III disease in 40% and stage IV disease in 60% of the surgically treated thumbs that provided specimens for study.
Results Initial intraoperative observations correlated poorly with study of the articular surface after freezing or stain-
ing. Synovial fluid coating the joint surface gave a smooth, shiny appearance to the eburnated region and served only to camouflage the dulled appearance of chondromalacia in the dorsal compartment (Fig. 1). However, subsequent staining of the surfaces highlighted the areas containing hyaline cartilage and facilitated recognition of the eburnated areas that were devoid of any stainable material. A predictable pattern of localized eburnation appeared on the facing surfaces of both trapezium and metacarpal bones. Metacarpal surface degeneration originated at the peripheral margin adjacent to the palmar beak ligament attachment in the palmar joint com-
Vol. 16A. No.6 November 1991
Ost eoarthritis of trapeziometacarpal joint, Jl
.He Di sease
, t aca r;la1- -
--
-
979
Tr apez . U'li
•
!"
t aca rpal
ea r
461
Tr ap/~C ~d
B
i rapez1um Mea r 10 . 39
64%
---.: Eb rnatio
_
Cart il age 0'1 rt1c l a r
Fig. 3. Idiopathic basal joint arthritis with advanced eburnation . Surfaces portrayed as right thumb with metacarpal on left, trapezium on right, and adjacent areas representing the palmar compartment. A, Stained surgical specimen; extensive pale areas of eburnation (single arrows) involve nearly entire trapezium. B, Digitized wear areas with trapezium/metacarpal ratio of relative wear; black indicates regions of retained articular cartilage. C, Preoperative stress radiograph of the same patient, stage IV.
partment (Fig. 2). More extensive disease was characterized by dorsal enlargement of the involved area toward the center of the metacarpal joint surface (Figs. 3 and 4) . Eburnation of the facing trapezial surface was more centrally located on the palmarly inclined slope of the trapezial saddle but remained concentrated within the palmar joint compartment (Fig. 2). More extensive involvement of the trapezium was characterized by concentric enlargement of this palmar compartment focus of eburnation (Figs. 3 and 4) . Stainable articular cartilage was always absent from the palmar compartment metacarpal surface and was most consi stently noted in joints with advanced disease on the dorsal compartment
surface of the metacarpal. Indeed , in those joints with the most severe disease, staining consi stently showed that the dorsal compartment contained the only remaining articular cartilage in the joint. Both the absolute and fractional areas of each surface eburnated and worn to subchondral bone were consistently greater on the trapezium than on the metacarpal. In less extensively involved joints, a small region of eburnation along the palmar margin of the metacarpal beak, always adjacent to the beak ligament attachment, was matched with an area of eburnation as much as three times greater on the trapezial surface (Fig. 2). In joints with more advanced disease (Fig. 3), a relatively
The Journal of
980
Pellegrini
HAND SURGERY
Fig. 4. Idiopathic basal joint arthritis with end-stage eburnation. Surfaces portrayed as right thumb with metacarpal on left, trapezium on right, and adjacent areas representing the palmar compartment. A, Stained surgical specimen; extensive pale areas of eburnation (single arrows) involve entire trapezium and spare only the dorsal noncontact zone of the metacarpal. Note prominent trapezial osteophyte (double arrows) along palmar margin of eburnated surface. B, Preoperative stress radiograph of the same patient, stage IV.
greater percentage of the metacarpal surface was eburnated and the ratio of trapezial to metacarpal wear approached unity (Fig. 5). Injoints with end-stage disease and functional ankylosis, prominent osteophytes obscured articular margins and nearly the entire surfaces of both trapezium and metacarpal were eburnated (Fig. 4). Remaining articular cartilage in the dorsal com-
partment of the joint was characterized by gross changes of pitting and softening with a dulled appearance to the joint surface (Fig. I, B and C). Radiographic stage was closely correlated with the TME ratio. The mean ratio of 2.20 (standard error of the mean, 0.20) for 11 thumbs with radiographic stage III disease compared favorably with a mean ratio of
Vol. 16A. No.6 November 1991
Osteoarthritis of trapeziom etacarpal joint, /I
981
RELATIVE TRAPEZIUM AND METACARPAL JO I NT SURF ACE WEAR
100
80
...., u
):
60
~
u
I:
40
20 [J
0 0
20
40
60
80
100
TRAP W; Wear Fig. 5. Relative trapezial and metacarpal joint surface wear. Increasing disease severity results in nearly total and symmetrical eburnation of both trapezial and metacarpal surfaces. with wear ratios approaching unity.
1.34 (standard error of the mean, 0.08) for 16 thumbs with radiographic stage IV disease (Fi g. 6); the difference was statistically significant at p < 0.00 I. Total or near complete loss of joint space, marginal ridging or osteophyte formation, and subchondral sclerosis characterized stage IV radiographs and predicted the most ext ensive disease, with TME ratios approaching unity. Discussion Surgical specimens removed at the time of basal joint arthroplasty in patients with stage III or stage IV radiographic disease exhibited a pattern of wear similar to that found in postmortem material. Eburnation suggesting severe articular disea se was present in all patients and occurred only in the palmar compartment. Only chondromalacia was observed in the.dorsal compartment; indeed , in those specimens with the most severe disease, the dorsal compartment contained the only remaining articular cartilage in the joint. This relatively uninvolved dorsal portion of the joint surface appeared to be a zone of frequent noncontact, as evidenced by examination of both stress radiographs and articulated surgical specimens (Fig. 1, A). Eburnation was consistently found over a greater articular surface area on the trapezium than on the metacarpal, in a ratio
as great as 3 : I in early disease and approaching unity in end-stage disease. This key observation implies translation of metacarpal on trapezium in order that a smaller area of wear (metacarpal) might imprint a larger area of wear on the facing surface (trapezium). Metacarpal wear was initially localized to the palmar perimeter adjacent to the beak ligament attachment and spread dorsoradially with increasing severity of disease. Trapezial wear began more centrally on the palmar slope and spread centrifugally with more advanced disease. Ultimately, as the disease becomes more severe, the TME ratio approaches unity and both joint surfaces are involved in a total pattern of eburnation characterized by prominent marginal osteophytes. The end-stage specimen offers little insight into etiology compared to the joint less overcome by eburnation , which again suggests a scenario of cartil age degeneration in joint contact areas caused by translation of metacarpal on trapezium. This configuration of palm ar compartment surface wear corresponds to the known contact areas in the trapeziometacarpaljoint produced by flexion-adduction of the thumb ray while the joint is functionally loaded during lateral pinch." Such a contact pattern would be expected to enlarge in the presence of an incompetent pal-
982
The Journal of HAND SURGERY
Pellegrini
CORRELATION OF RADIOGRAPHIC STAGE AND PATHOLOGIC WEAR 3.0
5! ~ -e
2.5
-e
2.0
IX IX ~
p < .001 ·2.20
>
u I:
"A-
