EFFECT OF SCAPHOID AND TRIQUETRUM EXCISION ON LIMITED ARTHRODESIS OF WRIST: A LABORATORY STUDY Aman Sood, Neil Ashwood, Gregory I Bain, Quinton Fogg Modbury Public Hospital, Adelaide, South Australia, Australia Adelaide University, Adelaide, South Australia, Australia. Correspondence: Mr Gregory I. Bain, 196 Melbourne Street, North Adelaide SA 5006, Australia Phone: +61 8 8361 8399, Fax: +61 8 8239 2237 Email: greg@gregbain.com.au Four-corner fusion (lunate, capitate, hamate & triquetral fusion) with scaphoid excision is the procedure of choice for symptomatic 1 scapholunate advanced collapse (SLAC wrist) . This procedure maintains carpal height, preserves intact radiolunate articulation, yields better grip strength and provides more reliable pain relief when 2,3,4,5 compared to alternative motion preserving procedures . The main disadvantage of this procedure has been relatively limited residual wrist motion, in particular when compared to Proximal Row 2,3 Carpectomy . Serial resection of scaphoid and triquetrum were planned as a laboratory study to assess the effect of their excision on wrist motion following four-corner fusion. Introduction Material and Methods 12 cadaveric limbs were severed at the level of upper forearm. A threaded Steinmann pin was passed through distal radius and ulna in neutral position. Skeletal markers were placed dorsally along the line of radius & 3rd metacarpal for measurements of radial & ulnar deviation. . Markers were also placed along the ulnar border of the forearm & 5th metacarpal for measurement of flexion & extension. Co-axial alignment of the markers with the wrist in neutral position was checked with electrogoniometer and confirmed to be accurate. Refer to Fig 1 Refer to Fig 2. Figure 1. Figure 2. The forearm was clamped to the dissecting table. For measurements, electrogoniometer was aligned with the proximal markers and centred at the level of proximal capitate. Meyerdierk's method of wrist motion 6 measurement, with a few modifications, was used . Measurements were taken by letting the wrist hang freely (anteriorly, posteriorly, radially and ulnarward) off the end of the table under the influence of gravity and 1.5 kg of skeletal traction. The measurements were recorded initially, after dorsal capsular release, following four-corner fusion and then sequentially after scaphoid and triquetral excision. Refer to Figure 3. & 4. Figure 3. Figure 4. Dorsal longitudinal approach through the 3rd extensor compartment. Dissection extended subperiosteally radially and ulnarward With the wrist in neutral position, four-corner fusion simulated using 3M staples Next, lunoscaphoid ligament severed and the scaphoid removed Finally, luno-triquetrum arthrodesis reversed and the triquetrum excised Operative Technique After every step capsular closure was performed, prior to performing wrist motion measurements in each plane. Results Graph 1. Wrist Motion Measured Data expressed as Degrees Standard Deviation (SD) Statistical significance: Two-tailed student's t-test with 5% confidence interval (p<0.05) Table 1. % Change in Wrist Motion Relative to Preceding Procedure Procedure Capsulotomy 4-corner fusion Scaphoid excision Triquetrum excision F-E arc % R-U arc % 8.3 6.2 16.9 13.0 29.3 12.5 5.3 9.6 +_ +_ +_ +_ +_ +_ +_ +_ _ _ Data expressed as Percentage Standard Deviation (SD) (-) Denotes reduction in motion SAGITTAL MOTION CORONAL MOTION Four-corner fusion with scaphoid excision relies on including unaffected bones (triqetrum and hamate) in the arthrodesis. It has been argued that this decreases the nonunion rate by maximizing the surface area for bone graft consolidation with no additional morbidity. However there is no evidence to support this in the literature. In our cadaveric study, excision of triquetrum following four-corner fusion significantly improved wrist motion in both planes. The functional range of the wrist motion to accomplish most ADL's has o o been reported from 35 of flexion-extension arc & 25 of radial-ulnar 7 0 o 8 arc to 80 of flexion-extension arc & 40 of radial-ulnar arc . To optimise patient quality of life, limited wrist arthrodesis should provide maximum residual wrist motion without compromising surgical results. Three bone fusion with scaphoid and triquetral excision may provide an alternative surgical option for treatment of SLAC wrist with better residual wrist motion. Discussion Conclusion In the cadaveric wrists, triquetral excision following limited mid carpal arthrodesis resulted in increased residual wrist motion in both coronal and saggital planes. Acknowledgments University of Adelaide for providing the cadaveric specimens, R J Heptinstall & Mark Stevens for help in preperation of the poster. References: 1. Watson HK, Ballett FL. The SLAC Wrist : Scapholunate advanced collapse of pattern of degenerative arthritis. J Hand Surg 1984;9A:358-365 2. Tomaino MM, Miller RJ, Cole I, Burton RI. Scapholunate advanced collapse wrist: proximal row carpectomy or limited wrist arthrodesis with scaphoid excision? J Hand Surg 1994;19A:358-365 3. Wyrick JD, Stern J, Kiefhaber TR: Motion preserving procedures in the treatment of scapholunate advanced collapse wrist: proximal row carpectomy versus four-corner arthrodesis. J Hand Surg 1995;20A:965-970 4. Cohen MS, Kozin SH: Degenerative arthritis of the wrist: Proximal row carpectomy versus scaphoid excision and four-corner arthrodesis. J Hand Surg 2001;26A:94-104 5. Krakauer JD, Bishop AT, Cooney W: Surgical treatment of scapholunate advanced collapse. J Hand Surg 1994;19A:751-759 6. Meyerdierks EM, Mosher JF, Werner FW: Limited wrist arthrodesis: A Laboratory study. J Hand Surg 1987:12A:526-529 7. Palmer AK, Werner FW, Murphy D, Glisson R: Functional wrist motion: a biomechanical study. J Hand Surg 1985;10A:39-46 8. Ryu J, Cooney WP, Askew LJ, An K-N, Chao EYS. Functional ranges of motion of the wrist joint. J Hand Surg 1991; 16A:409-419 Summary Effect of triquetrum excision o in F-E arc by 5% (mean 6 ) Increase in flexion by 8% Increase in extension by 3% (p>0.05) o in R-U arc by 13% (mean 7 ) Increase in UD by 22% Increase in RD by 4% (p>0.05) (All results statistically significant unless indicated otherwise) Refer to Figure 5 - 8 Figure 5. Figure 6. Figure 7. Figure 8. +_ 4 3 4 3 3 4 10 3 +_ This poster can be viewed and downloaded from www.gregbain.com.au