Ideal scaphoid angle for intercarpal arthrodesis

Ideal scaphoid angle for intercarpal arthrodesis This experimental study was conducted to determine the best scaphoid position, measured as the radioscaphoid (RS) angle for optimum wrist motion after scapho-trapezio-trapezoid (STT) and scaphocapitate (SC) fusion and to assess the implications of radial styloidectomy on motion after STT fusion. STT and SC fusions were simulated in six fresh cadaver hands with the scaphoid in horizontal, neutral, and vertical positions with respect to the long axis of the radius seen on lateral x-rays. RS angle and wrist motion were measured on x-ray films before and after each simulated arthrodesis. Radial deviation and wrist extension increased as the RS angle increased (i.e., increased as the scaphoid became more nearly vertical). Ulnar deviation and flexion decreased as the scaphoid became more nearly horizontal. We found no statistically significant differences in RS angle between SST and SC fusions with respect to ulnar deviation, flexion, or extension. However, radial deviation was more sensitive to RS angle after STT fusion than after SC fusion, but the differences were not statistically significant. The ideal radioscaphoid angle (range) for maximal wrist motion when STT fusion is performed is 41 to 60 degrees; when SC fusion is performed, it is 30 to 57 degrees. Motion is not improved by radial styloidectomy after simulated STT fusion. (J HAND SURC 1992;17A:370-5.)

Yoshitaka Toshiya

Minamikawa, Yamaguchi,

Osaka, Japan, Clayton A. Peimer, MD, Buffafo, N.Y., Osaka, Japan, John Medige, PhD, and Frances S. Sherwin,

MD, MD,

MA,

Buffalo, N.Y.

L

imited intercarpal arthrodesis, a procedure dating back to the early part of this century, is used for a variety of clinical disorders. Watson and the scaphoid-trapezio-trapezoid others’.* popularized (SIT) fusion to treat wrist instabilities and carpal collapse deformities; we have used scaphocapitate (SC) fusion for similar disorders.3 The increasing use of limited intercarpal fusions has led to renewed interest in clinical’.* and experimental studies9-” of the contribution of these arthrodeses to wrist motion and kinematics. It has been suggested, but not demonstrated, that functional outcome of the STT fusion depends on the scaphoid angle (radioscaphoid

From the Division of Hand Surgery, Department of Orthopaedic Surgery, University of Buffalo School of Medicine and Biomedical Sciences, State University of New York at Buffalo, and the Department of Orthopaedic Surgery, Kansai Medical University, Osaka, Japan. Received for publication 18, 1991.

Dec. 5, 1990; accepted in revised form July

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: Clayton A. Peimer, MD, Hand Center of Western New York, Millard Fillmore Hospital, 3 Gates Circle, Buffalo, NY 14209. 3/l/32570

370

THEJOURNAL OF HAND SURGERY

[RS] angle).4,8 Although radial styloidectomy was recently recommended for augmentation of wrist motion and reduction of local symptoms after SIT fusion,’ no data have been published on the relationship of the RS angle and wrist motion. The purpose of this experimental study is to determine the best scaphoid position (measured as RS angle) for optimal wrist motion after SIT and SC fusions and to assess the implications of radial styloidectomy on motion after STT fusion. Materials

and methods

Six frozen flesh cadaver arms were thawed, amputated at midhumerus, and mounted rigidly on a testing device with two Steinmann pins. The five wrist tendons were then statically loaded with 0.35 kg to simulate dynamic muscular wrist forces. An additional 0.20 kg load was applied perpendicular to an intramedullary Steinmann pin in the third metacarpal to move the wrist passively.’ Lateral x-ray films were taken of each specimen, in neutral to measure resting RS angle and at maximum wrist flexion and extension to measure the range of wrist and scaphoid motions. Radial and ulnar deviation were measured on posteroanterior x-ray films. Wrist motion and RS angle before intercarpal fixation provided baseline values for each specimen. The STT and SC fusions were simulated by percutaneously transfixing the appropriate joints with two to three threaded

Vol. 17A, No. 2 March 1992

ldrul

Table I. RS angles before and after fusions RS angle (degrees)

Baseline After STT

fusion After SC fusion

scaphoid

intercurpul

uthrodesis

371

STT - Radial Deviation . lOO”/O 1

/

Mean

Rail@

R=

48 2 6 40 + 12 34 2 10

40 - 56 15 - 58 20 - 50

PC

inch Kirschner wires. The procedures were performed in the following order: each fusion was simulated with the scaphoid at neutral (resting) RS angle, then in a relatively vertical or flexed position, and finally in a relatively horizontal or extended position with respect to the long axis of the radius. Wrist motion and RS angle were measured on x-ray films after each fusion. Also, wrist motion was measured on x-ray films after radial styloidectomy with the scaphoid horizontal, a position that could potentially impinge on the radius, thus limiting mobility or producing symptoms.

angle for

0.035

Results The mean baseline RS angle was 48 k 6 degrees; the mean angle after STT fusion was 40 ? 12 degrees; and after SC fusion it was 34 k 10 degrees (Table I). The mean flexion of the wrists before arthrodesis was 72 i: 17 degrees, the mean extension was 63 k 9 degrees, the mean radial deviation was 24 f. 9 degrees, and the mean ulnar deviation was 39 k 10 degrees. Wrist motions after simulated arthrodesis were expressed as percent of the baseline (100%) value (Table II). Because RS angles after each type of simulated arthrodesis differed, the relationship between RS angle and wrist motions were studied by linear regression analysis. Both RS angle and wrist motion were expressed as a percentage of baseline value. Radial deviation decreased after SIT fusion when the scaphoid was more horizontal ( Fig. 1). Ulnar deviation decreased after STT fusion as the RS angle increased (vertical scaphoid). As the scaphoid became more vertical, wrist flexion was restricted but wrist extension increased (Fig. 2). Linear regression analyses revealed no statistically significant differences between STT and SC fusions in ulnar deviation, flexion, or extension by RS angle (Figs. 2 and 3). However. the regression slope for RD was considerablly greater after STT fusion than after SC fusion (p < 0. l), meaning that, although radial deviation after simulated STT fusion was more affected by scaphoid position, the difference was not statistically

0

I

I

50 R - S Angle

100

130%

Fig. 1. Relation of differing RS angles and radial deviation of the wrist after simulated STT fusion. As the scaphoid was more nearly horizontal (extended or overcorrected) position. radial deviation decreased. (Motion and angles are percentage of baseline.)

significant. Radial styloidectomy performed after simulated STT fusion with the scaphoid horizontal did not improve radial deviation or any other wrist motion.

Peterson and Lipscomb’-’ described STT fusion in I967. In 1980 Watson and Hempton’ reported on I3 patients treated with STT fusion for a variety of intercarpal instabilities. The series of Kleinman et al.’ (12 cases) added cineradiographic analysis. Other report? added nearly 50 other STT fusions that were done for a wide range of intercarpal problems. Although no degenerative changes were found 4 years after surgery,’ Rogers and Watson7 reported that 30% of their patients had symptomatic “radial styloid (radioscaphoid) impingement” within 19 months of Sm fusion. Accordingly, they routinely use simultaneous radial styloidectomy combined with some undercorrection of the preoperative deformity (i.e., fusing the scaphoid in a more vertical position, with an RS angle of approximately 50 degrees). Interestingly, KleinmanX avoided arthritis in 25 SIT fusions by reducing the scaphoid to a more nearly horizontal position with an RS angle of approximately 45 degrees. The aggregate clinical reports have RS angles in the range of 44 to 61 degrees. ‘.‘.’

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The Journal of HAND SURGERY

et al.

Table II. Percent of wrist motion after fusions Radial

deviation

Ulnar deviation

Flexion

(%)

f%J

C%)

loo (39” 2 IO”)

100 (72” 2 17”) 82 + 16 78 ” 18

loo (63” * 9”) 71 + 16 16 -t 16

f%I

100 (24“ i

Baseline After SIT fusion After SC fusion

10”)

79 * 26 71 ? 22

59 r 28 62 2 18

Extension

Table III. Percent of wrist motion after fusions by investigator Radial Investigator

and fusion

Douglas et al. (1987)9 After SIT After SC Meyerdierks et al. (1987)” After STT After SC Gellman et al. (1988)” After STT After SCS Garcia-Elias et al. (1989)” After SIT After SC

i

deviarion

Ulnar deviation

(%J

(%J

Flexion

I

(%I

Extension

I

73* 79s

83t

69’ 81*

77t 81t

(%J

821

69

67

86

88

67 75

89 73

81 92

88 78

*Radial and ulnar deviation combined. tFlexion and extension combined. *Data not available.

Although Sutr~‘~ and Helfet15 were the first to use scaphocapitate fusions to treat scaphoid nonunions, the detailed results in a large series were published only recently.3 Both that study and several studies on simulated intercarpal arthrodeses and wrist motion3.9-‘2reported no significant difference in overall motion between SIT and SC fusions (Table III). No reports suggest that decreased wrist motion from intercarpal fusions causes functional problems. 16,17 Our findings of decreased RD as the scaphoid becomes horizontal supports the belie8*” that the “scaphoid should be fused in neutral to underreduction” (i.e., a relatively more vertical position) to avoid this problem. The finding that a vertical scaphoid reduced wrist flexion and increased wrist extension was contrary to the experience of Watson” and Green” that fusing the scaphoid in a relatively more horizontal (overreduced) position “leads to a loss of radial deviation and severe limitation of flexion.” To understand this discrepancy, we analyzed carpal kinematics by means of x-ray films. We know that when the wrist is deviated ulnarly, the scaphoid becomes more nearly horizontal SIT fusion performed with the scaphoid horizontal restricted radial deviation; compared with baseline, ulnar translocation of the proximal row was unchanged by SIT fusion (Fig. 4). Normal scaphoid flexion includes rotation of the

trapezoid and trapezium around the dorsum of the scaphoid neck, which is blocked by SIT fusion and thus restricts radial deviation.g-‘2 Theoretically radial styloidectomy would not therefore increase radial deviation unless there were actual preexisting impingement by the radius. In fact, radial styloidectomy performed after SIT fusion in our six specimens did not result in any appreciable change in wrist motion (Fig. 4, C). The relationships of the scaphoid to the distal carpal row in normal wrist flexion and extension are illustrated in Fig. 5, A. When the wrist flexes, the scaphoid also flexes (becomes vertical), and when the wrist extends, the scaphoid extends (becomes horizontal). Therefore the angle between the scaphoid and the distal carpal row normally becomes smaller when the wrist flexes since the distal row actually further flexes on the already vertical scaphoid. “.” On the other hand, when the wrist extends maximally, the angle between the scaphoid and the distal row widens as the distal row extends more than the now horizontal scaphoid. When SIT or SC fusions are performed with the scaphoid horizontal, the relationship between the scaphoid and the distal row is fixed at the same position as when the wrist is maximally flexed. Therefore, aggregate wrist extension is restricted relatively more than flexion, as extension of

Vol. 17A, No. 2 March 1992

ideal scaphoid angle for intercarpal urthrodesis

RD 100~ EX

UD FL

z -2 50-

0

j,

100

%

130

R - S Angle Fig. 2. Relation of RS angle and wrist motion after STT fusion. As RS angle decreased, radial deviation and wrist extension decreased. As RS angle increased (vertical or flexed scaphoid), ulnar deviation and flexion decreased.

%

EX RD

loo-

UD

s50-g

0

FL

, 50

R-S

I

100

1 %

130

Angle

Fig. 3. Relation of RS angle and wrist motion after SC fusion. When the linear regression graphs were compared, the regression slope for RD was considered greater with SIT fusion than with SC fusion.

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Fig. 4. Posteroanterior x-ray views. A, Radial deviation before simulated STT fusion. B, Radial deviation after STT fusion with scaphoid horizontal (so that radial deviation is restricted); ulnar translation of the proximal row is the same before and after fusion. C, Radial deviation after fusion plus radial styloidectomy shows no improvement in motion.

Fig. 5. A, The angle between scaphoid and distal row becomes larger when the wrist extends maximally and smaller as the wrist flexes. B, With the scaphoid fixed more horizontally, the angle between the scaphoid and the distal row is small, and extension is restricted by the fusion. C, If SIT or SC fusion is done with a vertical scaphoid, the angle between the scaphoid and the distal row is wide (the same as when the wrist is normally extended); flexion is restricted more than extension as further flexion of the distal row is blocked.

the distal row is blocked by the fusion (Fig. 5, B). If STT or SC fusion is performed with a vertical scaphoid, the angle between the scaphoid and the distal row is wide, the same as when the wrist is extended maximally. Therefore flexion is restricted more than exten-

sion as further flexion of the distal row is blocked by fusion (Fig. 5, C). We believe these findings may help explain why wrist motion is somewhat more sensitive to SIT fusion than to SC fusion (where residual STT movement is possible).‘.”

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Ideal scaphoid angle for intercarpal urthrodesis

375

UD FL

300 ,

I

A0

I

)

so 13.

100

I

I

I %

130

S Angle

0

50 R

S Angle

too

.

,% 130

Fig. 6. A, RS angle range needed to permit 60% or more wrist motion in four directions with STT fusion. B, For SC fusion, the ideal RS range is somewhat larger.

Wrist motion after limited intercarpal fusion may increase during the first postoperative year,‘,4 but the improvement may not be equal in all planes as ligament laxities vary. Since we know that 60% or more motion in each direction permits sufficient function,‘6.‘7 the RS angle needed to permit this range in all four planes is 41 to 60 degrees for STT fusion and 30 to 57 degrees for SC fusion (Fig. 6). SC fusion therefore allows somewhat more scaphoid overcorrection (more extension) with less compromise of wrist motion. This article represents a laboratory experiment to determine the relationship between fusion position and potential wrist motion. Other factors that affect motion in the postoperative or injured wrist and the difficulty in controlling and assessing the radioscaphoid angle intraoperatively suggest that care must be used in extrapolating experimental results into the clinical setting.

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7. Rogers WD, Watson HK. Radial styloid impingement after triscaphe arthrodesis. J HAND SURG 1989:14A:297301. 8. Kleinman WB. Long-term study of chronic scapholunate instability treated by scapho-trapezia-trapezoid arthrodesis. J Hand Surg 1989;14A:429-45. 9. Douglas DP. Peimer CA. Koniuch MP. Motion of the wrist after simulated limited intercarpal arthrodesis: an experimental study. J Bone Joint Surg 1987:69A: 1413-8. IO. Meyerdierks EM. Mosher JF. Werner FW. Limited wrist a laboratory study. J HAND SURG arthrodesis: 1987;12A:526-9. Gellman H. Kauffman D, Lenihan M. Botte MJ. Sarmiento A. An in vitro analysis of wrist motion: the effect of limited intercarpal arthrodesis and the contributions of the radiocarpal and midcarpal joints. J HAND SURG 1988; 13A:378-83. Garcia-Elias M. Cooney WP. An KN, Linschied RL. Chao EYS. Wrist kinematics after limited intercarpal arthrodesis. J HAND SURG 1989;14A:791-9. 13. Peterson HA, Lipscomb PR. Intercarpal arthrodesis. Arch Surg 1967:95:127-34. 14. Sutro CV. Treatment of nonunion of the carpal navicular bone. Surgery 1946;20:536-40. 15. Helfet AJ. A new operation for ununited fracture of the scaphoid. J Bone Joint Surg 1952;34B:329. 16. Brumfield R, Nickel V, Nickel E. Joint motion in wrist Aexion and extension. South Med J 1966;59:909-10. 17. Palmar AK, Werner FW, Murphy D. Glisson R. Functional wrist motion: a biomechanical study. J HAND SURG 1985;10A:39-46. 18. Green DP. Carpal dislocations and instabilities. In: Green DP. ed. Operative hand surgery. New York: Churchill Livingstone, 1988:925. 19. Watson HK. Limited intercarpal arthrodesis. In: Green DP. ed. Operative hand surgery. New York: Churchill Livingstone. 1988: 151,