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The biomechanical effects of a deepened articular cavity during dynamic motion of the wrist joint
Clinical Biomechanics 27 (2012) 557–561
Contents lists available at SciVerse ScienceDirect
Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech
The biomechanical effects of a deepened articular cavity during dynamic motion of the wrist joint Stefanie Erhart, Werner Schmoelz ⁎, Rohit Arora, Martin Lutz Medical University of Innsbruck, Department for Trauma Surgery, Innsbruck, Austria
a r t i c l e
i n f o
Article history: Received 26 August 2011 Accepted 10 January 2012 Keywords: Distal radius fracture Malunion Motion simulator Intraarticular pressure
a b s t r a c t Background: A deepened articular cavity of the distal radius due to a metaphyseal comminution zone is associated with early osteoarthritis and reduced joint motion. As this deformity has not been investigated biomechanically, the purpose of this study was to evaluate the effects of a deepened articular cavity on contact biomechanics and motion range in a dynamic biomechanical setting. Methods: Six fresh frozen cadaver forearms were tested in a force controlled test bench during dynamic flexion and extension and intact mean contact pressure and contact area as well as range of motion were evaluated. Malunion was then simulated and intraarticular as well as motion data were obtained. Intact and malunion data were compared for the scaphoid and lunate facet and the total radial joint surface. Findings: Due to malunion simulation, cavity depth increased significantly. Motion decreased significantly to 54–69% when compared to the intact state. Malunion simulation led to a significant decrease of contact area in maximum extension for all locations (by ~ 50%). In maximum flexion and neutral position, contact area decrease was significant for the scaphoid fossa (by 51–54%) and the total radial joint surface (by 47–50%). Contact pressure showed a significant increase in maximum extension in the scaphoid fossa (by 129%). Interpretation: Already a small cavity increase led to significant alterations in contact biomechanics of the radiocarpal joint and to a significant range of motion decrease. This could be the biomechanical cause for degenerative changes after the investigated type of malunion. We think that restoration of the normal distal radius shape can minimize osteoarthritis risk post trauma and improve radiocarpal motion. © 2012 Elsevier Ltd. All rights reserved.
1. Introduction After distal radius fractures, the most common complication is fracture malunion (Bushnell and Bynum, 2007). This bears the risk of subsequent osteoarthritis (Chen and Jupiter, 2007; Goldfarb et al., 2006; Knirk and Jupiter, 1986; Weiss and Rodner, 2007). From a biomechanical point of view the reason for osteoarthritis onset is thought to be altered kinematics of the wrist joint with a change in pressure magnitude and an alteration of pressure distribution (Anderson et al., 1996, 2005; Baratz et al., 1996; Pogue et al., 1990; Wagner et al., 1996). Recently, a special type of postraumatic alteration of the articular surface characterized by an increased cavity of the lunate fossa without a gap or step off of the articular surface has been recognized. It is likely to be the consequence of AO C3 type fractures with a considerable impression as well as volar and dorsal ulnar fragmentation and insufficient reduction (Jupiter and Lipton, 1993; Lutz et al., 2005; Medoff, 2005). Clinically, the presence of this increased articular cavity was described to significantly
⁎ Corresponding author at: Anichstraße 35, 6020 Innsbruck, Austria. E-mail address: [email protected] (W. Schmoelz). 0268-0033/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.clinbiomech.2012.01.003
correlate with the presence of arthritis and also to reduce carpal range of motion (RoM) (Lutz et al., 2005). To our knowledge the described form of malunion with a central cavitation of the radial joint surface was not yet investigated biomechanically. With a test-setup, which allows for dynamic flexion and extension of the wrist joint, the effect of this malunion on wrist joint biomechanics was investigated. The aim of the presented study was to compare scaphoid and lunate pressure characteristics as well as wrist joint motion with and without simulated malunion. This biomechanical investigation is intended to give more insight on the impact of an increased joint surface cavity. 2. Methods For biomechanical investigations of a deepened radial joint surface cavity, six fresh frozen human upper extremities were obtained from the local department of Anatomy. The specimens were CT-scanned (computed tomography, LightSpeed VCT, GE Healthcare, Milwaukee, USA) to exclude relevant pathologies and to measure the articular cavity depth, as described by Lutz et al. (2005). Prior to testing, the specimens were thawed overnight at 6 °C. Muscles relevant for testing (extensor carpi radialis longus and brevis-ECRL and ECRB, extensor carpi ulnaris-ECU, flexor carpi radialis-FCR, flexor carpi ulnaris-
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FCU and abductor pollicis longus-APL) were prepared and dissected at the musculotendinous junction. All other soft tissues were removed up to the carpal area and care was taken to preserve the interosseous membrane, stabilizing capsules and ligaments. The humerus was dissected 14 cm proximal to the olecranon and embedded in polymethyl-methacrylate (PMMA, Technovit 3040, Heraus Kulzer, Werheim, Germany) to allow mounting on the testing apparatus. Another mounting device was fixed to the ulna. The specimen was placed on the test-bench in 90° of elbow flexion and in neutral position of the wrist and hand (Fig. 1). An axial 6 N counterweight was fixed to the third proximal phalanx to balance the wrist. The test-bench allows for dynamic flexion and extension of the wrist joint with active agonistic and antagonistic muscle forces with a total aspired RoM of approximately 60° in the saggital plane. This motion range is in accordance with the publication by Werner et al. (1996). Force is exerted by pneumatic muscles (Shadow Robot Company Ltd., London, UK, operating pressure of control unit: 3.5 bar) and the motion is achieved in a force controlled protocol via a custom written LabView program (Erhart et al., 2011). Forces were applied to the six main wrist movers in their physiological direction. Motion in the saggital plane resulted by varying the force of the pneumatic muscles so that flexion and extension could be achieved by differently actuating agonistic and antagonistic muscles. Applied forces were chosen from values reported in the literature (Brand, 1985; Brand et al., 1981; Werner et al., 1996). The velocity to reach a certain force was controlled by pressure pulse duration. Motion in flexion and extension is recorded by an ultrasound based 3D motion analysis system (Zebris, Winbiomechanics, Isny, Germany). Motion markers were attached to the third metacarpal and to the mounting jig connected to the distal radius. For biomechanical testing, each specimen was tested in four different states.
sutures. Intraarticular measurements were recorded statically in neutral position and throughout consecutive motion cycles. • MAS) To simulate a malunited distal radius fracture with an increased articular cavity depth, a 4-part osteotomy according to Melone (1993) was performed with an oscillating saw 2 cm below the radial surface, along the interfossal ridge and in the middle of the ulnar fragment (Martineau et al., 2008) The deepened cavity was simulated with a polyethylene wedge placed inbetween the dorsal and the palmar ulnar fragment (Fig. 2). The osteotomy fragments were then fixed with a palmar osteosynthesis plate. Alignment of all fragments without gap or step off at the radial joint surface was ensured. The intraarticular sensor was again prepared as recommended by the manufacturer, inserted in the radiocarpal joint, fixed with threads and the capsule readjusted with sutures. Intraarticular measurements of the simulated malunion were recorded statically and throughout the consecutive motion cycles. • MAL) The specimen with the simulated malunion was retested without the intraarticular pressure sensor and with the capsule readjusted by sutures to investigate the range of motion.
• INT) The intact specimen was investigated, to adjust muscle forces permitting smooth motion of four consecutive cycles. After adjustments, the muscle forces remained at the specified values for all experiments. The intact range of motion was recorded. • INS) For intraarticular measurements, a piezo-resistive ink based sensor (wrist 4201, Tekscan Inc. South Boston, MA, USA) was prepared as suggested by the manufacturer with conditioning, equilibration and a power law two point calibration. The pressure sensor was inserted via a dorsal capsulotomy according to Berger et al. (1995), fixed with threads and the capsule readjusted by
Testing in every state was conducted through four consecutive cycles of flexion/extension motion for four trials each. For the states with inserted pressure sensor, also four trials in static position of the wrist, with the tendons pretensioned, were recorded in an alternating fashion (static–dynamic). After biomechanical testing a second CT-scan was performed to measure cavity depth changes at the radial joint surface due to malunion simulation. Tendon force, range of motion, intraarticular contact area and mean contact pressure were analyzed from the third loading cycle to prevent analysis of visco-elastic changes in the first cycles and to ensure that a completely finished cycle could be analyzed. Range of motion is reported from maximum flexion to maximum extension. Intraarticular measurements for mean contact pressure and contact area were subdivided into scaphoid and lunate fossa. Changes are reported in percent of the intact specimen. Statistical analysis was performed with the SPSS software package (version 17, SPSS Inc., IBM, Chicago, IL, USA). Data from the intact specimen and the simulated malunion were compared by means of a Wilcoxon-Signed Rank test. Tendon force data was compared by an ANOVA. Statistical significance was set at a P-value below 0.05. P-values between 0.05 and 0.1 were considered as a statistical trend.
Fig. 1. Biomechanical test-setup during dynamic motion, (a) pneumatic actuators and pretensioning unit, (b1) motion analysis system and (b2) motion markers.
Fig. 2. Multiplanar reconstruction of the malunion simulation, (1) shows the direction of the osteotomy along the interfossal ridge, (2) the osteotomy 2 cm below the radial joint surface, (3) the osteotomy to separate a palmar and a dorsal lunate fragment, (a) marks the polyethylene wedge to create a deepened joint surface.
S. Erhart et al. / Clinical Biomechanics 27 (2012) 557–561
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3. Results 3.1. Muscle force Peak tendon forces for the actuated muscles were 50.3–52.9 N for the ECRL, 55.5–56.6 N for the ECRB, 56.4–59.8 N for the ECU, 35.4– 37.7 N for the FCR and 52.3–54.3 N for the FCU. The forces remained similar throughout all tested specimen states with no statistically significant difference for each single muscle as well as for total muscle forces (ANOVA, P > =0.05). 3.2. Cavity depth Due to malunion simulation, the cavity depth increased from 3.7 (SD 0.3) to 4.6 mm (SD 0.2) on average. This increase was statistically significant (Wilcoxon rank test, P = 0.027). 3.3. RoM Range of motion for the intact specimen without sensor (INT) was 63.4° (14.6) and decreased to 45.9° (SD 23.7) due to sensor insertion (INS, Wilcoxon rank test, P = 0.028) and to 34.3° (SD 25.5) and 31.8 (SD 15.9) due to malunion simulation without (MAL) and with sensor (MAS). Comparing the range of motion between the specimens with inserted sensor (INS to MAS), we found a decrease to 69% due to malunion simulation. The decrease in RoM due to the simulated malunion was statistically significant without and with inserted intraarticular pressure sensor (Wilcoxon rank test, P = 0.046 and P = 0.046, respectively, Fig. 3). 3.4. Intraarticular measurements When compared to the intact state, contact area in neutral position decreased after malunion by 51, 40 and 47% for the scaphoid and lunate fossa and in total, respectively. This decrease was statistically significant for the scaphoid fossa and the total radius surface (Wilcoxon rank test, P = 0.046 and 0.046 respectively, Fig. 4a). In maximum extension, malunion simulation lead to a statistically significant decrease in contact area in the scaphoid and lunate fossa and for the total radial surface of 54, 42 and 50%, respectively (Wilcoxon rank test, P = 0.028, P = 0.046, P = 0.028, Fig. 4b). During maximum flexion, the contact area decreased by 35, 54 and 42% in the scaphoid and lunate fossa and in total, due to malunion simulation. This decrease was statistically significant for the scaphoid fossa and the total radial joint surface (Wilcoxon rank test, P = 0.028 and 0.046, respectively). The difference for lunate fossa contact area showed a statistical trend (P = 0.072, Fig. 4c). When compared to the intact state, mean contact pressure in neutral position increased due to malunion simulation by 129% and 113% in the
Fig. 3. Mean RoM for the intact specimens and the specimens with simulated malunion, solid columns represent the values for specimens without sensor, shaded columns the values with inserted intraarticular sensor, significant differences are marked with a *.
Fig. 4. Comparison of contact area for the intact specimen and the specimen with a deepened joint surface cavity (malunion), data are displayed in mm² as mean and SD for neutral position (a), maximum extension (b) and maximum flexion (c) significant differences are marked with a * (P b 0.05), statistical trends with a + (P > 0.05, b0.1).
scaphoid and lunate fossa, respectively. Total radiocarpal joint mean contact pressure increased by 129%. The pressure increase for the scaphoid fossa and the total radial joint surface was statistically significant (P = 0.040) and showed a statistical trend for the total radiocarpal joint (Wilcoxon rank test, P = 0.027 each, Fig. 5a). During maximum extension, mean contact pressure increased by 118%, 221% and 122% for the scaphoid fossa, the lunate fossa and total radial joint surface, respectively. There was a statistical significant difference for the scaphoid fossa and a statistical trend towards an increased pressure on the total radial joint surface (Wilcoxon rank test, P = 0.028 and 0.093, respectively, Fig. 5b). During maximum flexion, there was an increase in mean contact pressure by a factor of 1.6 for the scaphoid fossa. For the lunate fossa there was a fourfold increase and mean contact pressure doubled for the total radius surface. There was a statistically significant difference for the total radius surface and a statistical trend for the lunate fossa (Wilcoxon rank test, P = 0.046 and 0.068, Fig. 5c). Throughout all states of testing, peak pressure for the lunate and scaphoid fossa constantly remained at the flexor side of the wrist joint. 4. Discussion Posttraumatic articular incongruity following distal radius fractures is known to cause degenerative arthritis and clinical symptoms.
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Fig. 5. Comparison of contact pressures for the intact specimen and the specimen with a deepened joint surface cavity (malunion), data are displayed in MPa as mean and SD for neutral position (a), maximum extension (b) and maximum flexion (c) significant differences are marked with a * (P b 0.05), statistical trends with a + (P > 0.05, b0.1).
Up to now, intraarticular step-off and gap formation were identified as main factors in the development of joint deterioration. However, recently alterations of the articular joint surface shape have been proven to be a proarthrotic factor as well (Lutz et al., 2005). To provide further insight on biomechanics of this alteration, we investigated this form of malunion with a standardized biomechanical test setup with active muscle forces. In contrast to previous biomechanical studies, an altered shape of the articular surface in the saggital plane was the prime focus of this study. Therefore, the anatomical modifications were less pronounced than in comparable biomechanical studies (Anderson et al., 2005; Baratz et al., 1996; Wagner et al., 1996) to avoid an additional articular step-off. However, the alterations were in the range of values reported for posttraumatic malunion with a deepened articular joint surface (Lutz et al., 2005). With a further increase of the cavity, maintenance of a joint surface without gap or step-off would not have been possible. However, the simulated malunion lead to a significant alteration of joint contact area and showed a considerable influence on articular pressure distribution and contact area. This form of malunion was not yet investigated on its biomechanical effects. Therefore, direct comparison with the current literature is difficult. Regarding related forms of malunion, like a lunate die-punch fragment, reported data can be confirmed with the results from the presented study showing an increased pressure on the articular surface. An increase in scaphoid loading
after a simulated lunate die-punch fragment was reported by Anderson et al. (2005). Baratz et al. also reported a significantly increased mean contact stress after the simulation of a displaced fracture of the lunate fossa (Baratz et al., 1996). The increased pressure in the scaphoid fossa was also confirmed by Wagner et al. after a lunate fossa depression of more than 3 mm (Wagner et al., 1996). The location of peak pressure on the flexor side, as found in the presented study, is comparable to the location described by Short et al. (1997) using the same type of digital sensors. In a figure displayed by Pogue et al., also both, the lunate and scaphoid projected palmarly (Pogue et al., 1990). In contrary, a clinical study using CT osteoabsorptiometry reported that the scaphoid projected dorsally or centrally, with the lunate remaining palmarly (Giunta et al., 2004). This location was also confirmed in a biomechanical study by Tang et al. with the scaphoid projecting dorsally and the lunate palmarly (Tang et al., 2009). The pressure distribution described in our study might partly be due to the dorsal capsulotomy and partly to sensor insertion. The sensor used in this particular study was inserted as described by Short et al. (1997). In a finite element analysis Carrigan et al. showed that the removal of scaphoid constraint nodes led to a palmar shift of the radioscaphoid contact region (Carrigan et al., 2003). However, this approach was chosen for the current study due to sensor geometry. An insertion of a different kind of sensor through the anatomic snuff box as proposed in one publication was not feasible due to the used sensor design (Short et al., 2002). The current study investigated intraarticular biomechanics during force controlled Flexion and Extension only. Additional data concerning other motions like ulnar- and radial deviation as well as dartthrow motion would hence be required to gain more information on the biomechanical effects of intraarticular pathologies. In a functional radiographic study impairment of saggital wrist motion could be correlated with the articular cavity depth. Interpretation of these results by the authors suggests an altered rotation-gliding mechanism of the proximal carpal row (Lutz et al., 2005). The simulated form of malunion can be accompanied by a reduced dorsopalmar tilt. In a literature review by Bushnell et al., alterations in this tilt were described to have a motion restricting effect (Fernandez, 1982; Hirahara et al., 2003; Prommersberger et al., 2004). However, our results can only reflect the state of the skeletal distal radius and cannot consider degenerative changes of the cartilage, the influence on concomitant ligament injuries or healing potentials. A clinical study investigated different extents of joint surface stepoff and found that already a 1 mm step-off causes pain and a decrease in RoM and grip strength (Fernandez and Geissler, 1991). The deepened cavity in the presented study resulted in significant alterations. This led us to the assumption that the effect on wrist joint cartilage is deleterious and therefore the risk to develop posttraumatic arthritis is increased. Already in 1994 Trumble et al. reported that an exact anatomical reconstruction of a congruent and anatomically shaped distal radial surface significantly improves functional outcome (Trumble et al., 1994). However, this might not be easy to accomplish in the presented form of malunion, also with modern open techniques (Lutz et al., 2005). Therefore, further development of surgical techniques and implants is necessary and direct visualisation of the fracture site by arthroscopy encouraged. This was shown to be beneficial in the treatment of intraarticular malunion (del Pinal et al., 2010). 5. Conclusion A deepened cavity of the distal radial surface leads to considerable alterations in radiocarpal joint biomechanics. This might be the source for long term degenerative changes of the wrist joint. Therefore, restoration of the normal shape of the distal radius is likely to improve radio-carpal motion and to minimize the risk for posttraumatic arthritis.
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Acknowledgements The Medical University Innsbruck is acknowledged for funding of parts of the project with the MUI START grant. Christoph Kohstall is acknowledged for his help with programming and valuable comments on the test setup. References Anderson, D.D., Bell, A.L., Gaffney, M.B., Imbriglia, J.E., 1996. Contact stress distributions in malreduced intraarticular distal radius fractures. J. Orthop. Trauma 10, 331–337. Anderson, D.D., Deshpande, B.R., Daniel, T.E., Baratz, M.E., 2005. A three-dimensional finite element model of the radiocarpal joint: distal radius fracture step-off and stress transfer. Iowa Orthop. J. 25, 108–117. Baratz, M.E., Des Jardins, J., Anderson, D.D., Imbriglia, J.E., 1996. Displaced intra-articular fractures of the distal radius: the effect of fracture displacement on contact stresses in a cadaver model. J. Hand Surg. Am. 21, 183–188. Berger, R.A., Bishop, A.T., Bettinger, P.C., 1995. New dorsal capsulotomy for the surgical exposure of the wrist. Ann. Plast. Surg. 35, 54–59. Brand, P.W., 1985. Clinical Mechanics of the Hand, St. Louis, C. V. Mosby. Brand, P.W., Beach, R.B., Thompson, D.E., 1981. Relative tension and potential excursion of muscles in the forearm and hand. J. Hand Surg. Am. 6, 209–219. Bushnell, B.D., Bynum, D.K., 2007. Malunion of the distal radius. J. Am. Acad. Orthop. Surg. 15, 27–40. Carrigan, S.D., Whiteside, R.A., Pichora, D.R., Small, C.F., 2003. Development of a threedimensional finite element model for carpal load transmission in a static neutral posture. Ann. Biomed. Eng. 31, 718–725. Chen, N.C., Jupiter, J.B., 2007. Management of distal radial fractures. J. Bone Joint Surg. Am. 89, 2051–2062. Del Pinal, F., Cagigal, L., Garcia-Bernal, F.J., Studer, A., Regalado, J., Thams, C., 2010. Arthroscopically guided osteotomy for management of intra-articular distal radius malunions. J. Hand Surg. Am. 35, 392–397. Erhart, S., Lutz, M., Arora, R., Schmoelz, W., 2011. Measurement of intraarticular wrist joint biomechanics with a force controlled system. Med. Eng, Phys. (Oct 27, Electronic publication ahead of print). Fernandez, D.L., 1982. Correction of post-traumatic wrist deformity in adults by osteotomy, bone-grafting, and internal fixation. J. Bone Joint Surg. Am. 64, 1164–1178. Fernandez, D.L., Geissler, W.B., 1991. Treatment of displaced articular fractures of the radius. J. Hand Surg. Am. 16, 375–384. Giunta, R.E., Biemer, E., Muller-Gerbl, M., 2004. Ulnar variance and subchondral bone mineralization patterns in the distal articular surface of the radius. J. Hand Surg. Am. 29, 835–840.
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Goldfarb, C.A., Rudzki, J.R., Catalano, L.W., Hughes, M., Borrelli Jr., J., 2006. Fifteen-year outcome of displaced intra-articular fractures of the distal radius. J. Hand Surg. Am. 31, 633–639. Hirahara, H., Neale, P.G., Lin, Y.T., Cooney, W.P., An, K.N., 2003. Kinematic and torquerelated effects of dorsally angulated distal radius fractures and the distal radial ulnar joint. J. Hand Surg. Am. 28, 614–621. Jupiter, J.B., Lipton, H., 1993. The operative treatment of intraarticular fractures of the distal radius. Clin. Orthop. Relat. Res. 48–61. Knirk, J.L., Jupiter, J.B., 1986. Intra-articular fractures of the distal end of the radius in young adults. J. Bone Joint Surg. Am. 68, 647–659. Lutz, M., Rudisch, A., Kralinger, F., Smekal, V., Goebel, G., Gabl, M., Pechlaner, S., 2005. Sagittal wrist motion of carpal bones following intraarticular fractures of the distal radius. J. Hand Surg. Br. 30, 282–287. Martineau, P.A., Waitayawinyu, T., Malone, K.J., Hanel, D.P., Trumble, T.E., 2008. Volar plating of AO C3 distal radius fractures: biomechanical evaluation of locking screw and locking smooth peg configurations. J. Hand Surg. Am. 33, 827–834. Medoff, R.J., 2005. Essential radiographic evaluation for distal radius fractures. Hand Clin. 21, 279–288. Melone Jr., C.P., 1993. Distal radius fractures: patterns of articular fragmentation. Orthop. Clin. North Am. 24, 239–253. Pogue, D.J., Viegas, S.F., Patterson, R.M., Peterson, P.D., Jenkins, D.K., Sweo, T.D., Hokanson, J.A., 1990. Effects of distal radius fracture malunion on wrist joint mechanics. J. Hand Surg. Am. 15, 721–727. Prommersberger, K.J., Froehner, S.C., Schmitt, R.R., Lanz, U.B., 2004. Rotational deformity in malunited fractures of the distal radius. J. Hand Surg. Am. 29, 110–115. Short, W.H., Werner, F.W., Fortino, M.D., Mann, K.A., 1997. Analysis of the kinematics of the scaphoid and lunate in the intact wrist joint. Hand Clin. 13, 93–108. Short, W.H., Werner, F.W., Green, J.K., Weiner, M.M., Masaoka, S., 2002. The effect of sectioning the dorsal radiocarpal ligament and insertion of a pressure sensor into the radiocarpal joint on scaphoid and lunate kinematics. J. Hand Surg. Am. 27, 68–76. Tang, P., Gauvin, J., Muriuki, M., Pfaeffle, J.H., Imbriglia, J.E., Goitz, R.J., 2009. Comparison of the “contact biomechanics” of the intact and proximal row carpectomy wrist. J. Hand Surg. Am. 34, 660–670. Trumble, T.E., Schmitt, S.R., Vedder, N.B., 1994. Factors affecting functional outcome of displaced intra-articular distal radius fractures. J. Hand Surg. Am. 19, 325–340. Wagner Jr., W.F., Tencer, A.F., Kiser, P., Trumble, T.E., 1996. Effects of intra-articular distal radius depression on wrist joint contact characteristics. J. Hand Surg. Am. 21, 554–560. Weiss, K.E., Rodner, C.M., 2007. Osteoarthritis of the wrist. J. Hand Surg. Am. 32, 725–746. Werner, F.W., Palmer, A.K., Somerset, J.H., Tong, J.J., Gillison, D.B., Fortino, M.D., Short, W.H., 1996. Wrist joint motion simulator. J. Orthop. Res. 14, 639–646.
Contents lists available at SciVerse ScienceDirect
Clinical Biomechanics journal homepage: www.elsevier.com/locate/clinbiomech
The biomechanical effects of a deepened articular cavity during dynamic motion of the wrist joint Stefanie Erhart, Werner Schmoelz ⁎, Rohit Arora, Martin Lutz Medical University of Innsbruck, Department for Trauma Surgery, Innsbruck, Austria
a r t i c l e
i n f o
Article history: Received 26 August 2011 Accepted 10 January 2012 Keywords: Distal radius fracture Malunion Motion simulator Intraarticular pressure
a b s t r a c t Background: A deepened articular cavity of the distal radius due to a metaphyseal comminution zone is associated with early osteoarthritis and reduced joint motion. As this deformity has not been investigated biomechanically, the purpose of this study was to evaluate the effects of a deepened articular cavity on contact biomechanics and motion range in a dynamic biomechanical setting. Methods: Six fresh frozen cadaver forearms were tested in a force controlled test bench during dynamic flexion and extension and intact mean contact pressure and contact area as well as range of motion were evaluated. Malunion was then simulated and intraarticular as well as motion data were obtained. Intact and malunion data were compared for the scaphoid and lunate facet and the total radial joint surface. Findings: Due to malunion simulation, cavity depth increased significantly. Motion decreased significantly to 54–69% when compared to the intact state. Malunion simulation led to a significant decrease of contact area in maximum extension for all locations (by ~ 50%). In maximum flexion and neutral position, contact area decrease was significant for the scaphoid fossa (by 51–54%) and the total radial joint surface (by 47–50%). Contact pressure showed a significant increase in maximum extension in the scaphoid fossa (by 129%). Interpretation: Already a small cavity increase led to significant alterations in contact biomechanics of the radiocarpal joint and to a significant range of motion decrease. This could be the biomechanical cause for degenerative changes after the investigated type of malunion. We think that restoration of the normal distal radius shape can minimize osteoarthritis risk post trauma and improve radiocarpal motion. © 2012 Elsevier Ltd. All rights reserved.
1. Introduction After distal radius fractures, the most common complication is fracture malunion (Bushnell and Bynum, 2007). This bears the risk of subsequent osteoarthritis (Chen and Jupiter, 2007; Goldfarb et al., 2006; Knirk and Jupiter, 1986; Weiss and Rodner, 2007). From a biomechanical point of view the reason for osteoarthritis onset is thought to be altered kinematics of the wrist joint with a change in pressure magnitude and an alteration of pressure distribution (Anderson et al., 1996, 2005; Baratz et al., 1996; Pogue et al., 1990; Wagner et al., 1996). Recently, a special type of postraumatic alteration of the articular surface characterized by an increased cavity of the lunate fossa without a gap or step off of the articular surface has been recognized. It is likely to be the consequence of AO C3 type fractures with a considerable impression as well as volar and dorsal ulnar fragmentation and insufficient reduction (Jupiter and Lipton, 1993; Lutz et al., 2005; Medoff, 2005). Clinically, the presence of this increased articular cavity was described to significantly
⁎ Corresponding author at: Anichstraße 35, 6020 Innsbruck, Austria. E-mail address: [email protected] (W. Schmoelz). 0268-0033/$ – see front matter © 2012 Elsevier Ltd. All rights reserved. doi:10.1016/j.clinbiomech.2012.01.003
correlate with the presence of arthritis and also to reduce carpal range of motion (RoM) (Lutz et al., 2005). To our knowledge the described form of malunion with a central cavitation of the radial joint surface was not yet investigated biomechanically. With a test-setup, which allows for dynamic flexion and extension of the wrist joint, the effect of this malunion on wrist joint biomechanics was investigated. The aim of the presented study was to compare scaphoid and lunate pressure characteristics as well as wrist joint motion with and without simulated malunion. This biomechanical investigation is intended to give more insight on the impact of an increased joint surface cavity. 2. Methods For biomechanical investigations of a deepened radial joint surface cavity, six fresh frozen human upper extremities were obtained from the local department of Anatomy. The specimens were CT-scanned (computed tomography, LightSpeed VCT, GE Healthcare, Milwaukee, USA) to exclude relevant pathologies and to measure the articular cavity depth, as described by Lutz et al. (2005). Prior to testing, the specimens were thawed overnight at 6 °C. Muscles relevant for testing (extensor carpi radialis longus and brevis-ECRL and ECRB, extensor carpi ulnaris-ECU, flexor carpi radialis-FCR, flexor carpi ulnaris-
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FCU and abductor pollicis longus-APL) were prepared and dissected at the musculotendinous junction. All other soft tissues were removed up to the carpal area and care was taken to preserve the interosseous membrane, stabilizing capsules and ligaments. The humerus was dissected 14 cm proximal to the olecranon and embedded in polymethyl-methacrylate (PMMA, Technovit 3040, Heraus Kulzer, Werheim, Germany) to allow mounting on the testing apparatus. Another mounting device was fixed to the ulna. The specimen was placed on the test-bench in 90° of elbow flexion and in neutral position of the wrist and hand (Fig. 1). An axial 6 N counterweight was fixed to the third proximal phalanx to balance the wrist. The test-bench allows for dynamic flexion and extension of the wrist joint with active agonistic and antagonistic muscle forces with a total aspired RoM of approximately 60° in the saggital plane. This motion range is in accordance with the publication by Werner et al. (1996). Force is exerted by pneumatic muscles (Shadow Robot Company Ltd., London, UK, operating pressure of control unit: 3.5 bar) and the motion is achieved in a force controlled protocol via a custom written LabView program (Erhart et al., 2011). Forces were applied to the six main wrist movers in their physiological direction. Motion in the saggital plane resulted by varying the force of the pneumatic muscles so that flexion and extension could be achieved by differently actuating agonistic and antagonistic muscles. Applied forces were chosen from values reported in the literature (Brand, 1985; Brand et al., 1981; Werner et al., 1996). The velocity to reach a certain force was controlled by pressure pulse duration. Motion in flexion and extension is recorded by an ultrasound based 3D motion analysis system (Zebris, Winbiomechanics, Isny, Germany). Motion markers were attached to the third metacarpal and to the mounting jig connected to the distal radius. For biomechanical testing, each specimen was tested in four different states.
sutures. Intraarticular measurements were recorded statically in neutral position and throughout consecutive motion cycles. • MAS) To simulate a malunited distal radius fracture with an increased articular cavity depth, a 4-part osteotomy according to Melone (1993) was performed with an oscillating saw 2 cm below the radial surface, along the interfossal ridge and in the middle of the ulnar fragment (Martineau et al., 2008) The deepened cavity was simulated with a polyethylene wedge placed inbetween the dorsal and the palmar ulnar fragment (Fig. 2). The osteotomy fragments were then fixed with a palmar osteosynthesis plate. Alignment of all fragments without gap or step off at the radial joint surface was ensured. The intraarticular sensor was again prepared as recommended by the manufacturer, inserted in the radiocarpal joint, fixed with threads and the capsule readjusted with sutures. Intraarticular measurements of the simulated malunion were recorded statically and throughout the consecutive motion cycles. • MAL) The specimen with the simulated malunion was retested without the intraarticular pressure sensor and with the capsule readjusted by sutures to investigate the range of motion.
• INT) The intact specimen was investigated, to adjust muscle forces permitting smooth motion of four consecutive cycles. After adjustments, the muscle forces remained at the specified values for all experiments. The intact range of motion was recorded. • INS) For intraarticular measurements, a piezo-resistive ink based sensor (wrist 4201, Tekscan Inc. South Boston, MA, USA) was prepared as suggested by the manufacturer with conditioning, equilibration and a power law two point calibration. The pressure sensor was inserted via a dorsal capsulotomy according to Berger et al. (1995), fixed with threads and the capsule readjusted by
Testing in every state was conducted through four consecutive cycles of flexion/extension motion for four trials each. For the states with inserted pressure sensor, also four trials in static position of the wrist, with the tendons pretensioned, were recorded in an alternating fashion (static–dynamic). After biomechanical testing a second CT-scan was performed to measure cavity depth changes at the radial joint surface due to malunion simulation. Tendon force, range of motion, intraarticular contact area and mean contact pressure were analyzed from the third loading cycle to prevent analysis of visco-elastic changes in the first cycles and to ensure that a completely finished cycle could be analyzed. Range of motion is reported from maximum flexion to maximum extension. Intraarticular measurements for mean contact pressure and contact area were subdivided into scaphoid and lunate fossa. Changes are reported in percent of the intact specimen. Statistical analysis was performed with the SPSS software package (version 17, SPSS Inc., IBM, Chicago, IL, USA). Data from the intact specimen and the simulated malunion were compared by means of a Wilcoxon-Signed Rank test. Tendon force data was compared by an ANOVA. Statistical significance was set at a P-value below 0.05. P-values between 0.05 and 0.1 were considered as a statistical trend.
Fig. 1. Biomechanical test-setup during dynamic motion, (a) pneumatic actuators and pretensioning unit, (b1) motion analysis system and (b2) motion markers.
Fig. 2. Multiplanar reconstruction of the malunion simulation, (1) shows the direction of the osteotomy along the interfossal ridge, (2) the osteotomy 2 cm below the radial joint surface, (3) the osteotomy to separate a palmar and a dorsal lunate fragment, (a) marks the polyethylene wedge to create a deepened joint surface.
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3. Results 3.1. Muscle force Peak tendon forces for the actuated muscles were 50.3–52.9 N for the ECRL, 55.5–56.6 N for the ECRB, 56.4–59.8 N for the ECU, 35.4– 37.7 N for the FCR and 52.3–54.3 N for the FCU. The forces remained similar throughout all tested specimen states with no statistically significant difference for each single muscle as well as for total muscle forces (ANOVA, P > =0.05). 3.2. Cavity depth Due to malunion simulation, the cavity depth increased from 3.7 (SD 0.3) to 4.6 mm (SD 0.2) on average. This increase was statistically significant (Wilcoxon rank test, P = 0.027). 3.3. RoM Range of motion for the intact specimen without sensor (INT) was 63.4° (14.6) and decreased to 45.9° (SD 23.7) due to sensor insertion (INS, Wilcoxon rank test, P = 0.028) and to 34.3° (SD 25.5) and 31.8 (SD 15.9) due to malunion simulation without (MAL) and with sensor (MAS). Comparing the range of motion between the specimens with inserted sensor (INS to MAS), we found a decrease to 69% due to malunion simulation. The decrease in RoM due to the simulated malunion was statistically significant without and with inserted intraarticular pressure sensor (Wilcoxon rank test, P = 0.046 and P = 0.046, respectively, Fig. 3). 3.4. Intraarticular measurements When compared to the intact state, contact area in neutral position decreased after malunion by 51, 40 and 47% for the scaphoid and lunate fossa and in total, respectively. This decrease was statistically significant for the scaphoid fossa and the total radius surface (Wilcoxon rank test, P = 0.046 and 0.046 respectively, Fig. 4a). In maximum extension, malunion simulation lead to a statistically significant decrease in contact area in the scaphoid and lunate fossa and for the total radial surface of 54, 42 and 50%, respectively (Wilcoxon rank test, P = 0.028, P = 0.046, P = 0.028, Fig. 4b). During maximum flexion, the contact area decreased by 35, 54 and 42% in the scaphoid and lunate fossa and in total, due to malunion simulation. This decrease was statistically significant for the scaphoid fossa and the total radial joint surface (Wilcoxon rank test, P = 0.028 and 0.046, respectively). The difference for lunate fossa contact area showed a statistical trend (P = 0.072, Fig. 4c). When compared to the intact state, mean contact pressure in neutral position increased due to malunion simulation by 129% and 113% in the
Fig. 3. Mean RoM for the intact specimens and the specimens with simulated malunion, solid columns represent the values for specimens without sensor, shaded columns the values with inserted intraarticular sensor, significant differences are marked with a *.
Fig. 4. Comparison of contact area for the intact specimen and the specimen with a deepened joint surface cavity (malunion), data are displayed in mm² as mean and SD for neutral position (a), maximum extension (b) and maximum flexion (c) significant differences are marked with a * (P b 0.05), statistical trends with a + (P > 0.05, b0.1).
scaphoid and lunate fossa, respectively. Total radiocarpal joint mean contact pressure increased by 129%. The pressure increase for the scaphoid fossa and the total radial joint surface was statistically significant (P = 0.040) and showed a statistical trend for the total radiocarpal joint (Wilcoxon rank test, P = 0.027 each, Fig. 5a). During maximum extension, mean contact pressure increased by 118%, 221% and 122% for the scaphoid fossa, the lunate fossa and total radial joint surface, respectively. There was a statistical significant difference for the scaphoid fossa and a statistical trend towards an increased pressure on the total radial joint surface (Wilcoxon rank test, P = 0.028 and 0.093, respectively, Fig. 5b). During maximum flexion, there was an increase in mean contact pressure by a factor of 1.6 for the scaphoid fossa. For the lunate fossa there was a fourfold increase and mean contact pressure doubled for the total radius surface. There was a statistically significant difference for the total radius surface and a statistical trend for the lunate fossa (Wilcoxon rank test, P = 0.046 and 0.068, Fig. 5c). Throughout all states of testing, peak pressure for the lunate and scaphoid fossa constantly remained at the flexor side of the wrist joint. 4. Discussion Posttraumatic articular incongruity following distal radius fractures is known to cause degenerative arthritis and clinical symptoms.
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Fig. 5. Comparison of contact pressures for the intact specimen and the specimen with a deepened joint surface cavity (malunion), data are displayed in MPa as mean and SD for neutral position (a), maximum extension (b) and maximum flexion (c) significant differences are marked with a * (P b 0.05), statistical trends with a + (P > 0.05, b0.1).
Up to now, intraarticular step-off and gap formation were identified as main factors in the development of joint deterioration. However, recently alterations of the articular joint surface shape have been proven to be a proarthrotic factor as well (Lutz et al., 2005). To provide further insight on biomechanics of this alteration, we investigated this form of malunion with a standardized biomechanical test setup with active muscle forces. In contrast to previous biomechanical studies, an altered shape of the articular surface in the saggital plane was the prime focus of this study. Therefore, the anatomical modifications were less pronounced than in comparable biomechanical studies (Anderson et al., 2005; Baratz et al., 1996; Wagner et al., 1996) to avoid an additional articular step-off. However, the alterations were in the range of values reported for posttraumatic malunion with a deepened articular joint surface (Lutz et al., 2005). With a further increase of the cavity, maintenance of a joint surface without gap or step-off would not have been possible. However, the simulated malunion lead to a significant alteration of joint contact area and showed a considerable influence on articular pressure distribution and contact area. This form of malunion was not yet investigated on its biomechanical effects. Therefore, direct comparison with the current literature is difficult. Regarding related forms of malunion, like a lunate die-punch fragment, reported data can be confirmed with the results from the presented study showing an increased pressure on the articular surface. An increase in scaphoid loading
after a simulated lunate die-punch fragment was reported by Anderson et al. (2005). Baratz et al. also reported a significantly increased mean contact stress after the simulation of a displaced fracture of the lunate fossa (Baratz et al., 1996). The increased pressure in the scaphoid fossa was also confirmed by Wagner et al. after a lunate fossa depression of more than 3 mm (Wagner et al., 1996). The location of peak pressure on the flexor side, as found in the presented study, is comparable to the location described by Short et al. (1997) using the same type of digital sensors. In a figure displayed by Pogue et al., also both, the lunate and scaphoid projected palmarly (Pogue et al., 1990). In contrary, a clinical study using CT osteoabsorptiometry reported that the scaphoid projected dorsally or centrally, with the lunate remaining palmarly (Giunta et al., 2004). This location was also confirmed in a biomechanical study by Tang et al. with the scaphoid projecting dorsally and the lunate palmarly (Tang et al., 2009). The pressure distribution described in our study might partly be due to the dorsal capsulotomy and partly to sensor insertion. The sensor used in this particular study was inserted as described by Short et al. (1997). In a finite element analysis Carrigan et al. showed that the removal of scaphoid constraint nodes led to a palmar shift of the radioscaphoid contact region (Carrigan et al., 2003). However, this approach was chosen for the current study due to sensor geometry. An insertion of a different kind of sensor through the anatomic snuff box as proposed in one publication was not feasible due to the used sensor design (Short et al., 2002). The current study investigated intraarticular biomechanics during force controlled Flexion and Extension only. Additional data concerning other motions like ulnar- and radial deviation as well as dartthrow motion would hence be required to gain more information on the biomechanical effects of intraarticular pathologies. In a functional radiographic study impairment of saggital wrist motion could be correlated with the articular cavity depth. Interpretation of these results by the authors suggests an altered rotation-gliding mechanism of the proximal carpal row (Lutz et al., 2005). The simulated form of malunion can be accompanied by a reduced dorsopalmar tilt. In a literature review by Bushnell et al., alterations in this tilt were described to have a motion restricting effect (Fernandez, 1982; Hirahara et al., 2003; Prommersberger et al., 2004). However, our results can only reflect the state of the skeletal distal radius and cannot consider degenerative changes of the cartilage, the influence on concomitant ligament injuries or healing potentials. A clinical study investigated different extents of joint surface stepoff and found that already a 1 mm step-off causes pain and a decrease in RoM and grip strength (Fernandez and Geissler, 1991). The deepened cavity in the presented study resulted in significant alterations. This led us to the assumption that the effect on wrist joint cartilage is deleterious and therefore the risk to develop posttraumatic arthritis is increased. Already in 1994 Trumble et al. reported that an exact anatomical reconstruction of a congruent and anatomically shaped distal radial surface significantly improves functional outcome (Trumble et al., 1994). However, this might not be easy to accomplish in the presented form of malunion, also with modern open techniques (Lutz et al., 2005). Therefore, further development of surgical techniques and implants is necessary and direct visualisation of the fracture site by arthroscopy encouraged. This was shown to be beneficial in the treatment of intraarticular malunion (del Pinal et al., 2010). 5. Conclusion A deepened cavity of the distal radial surface leads to considerable alterations in radiocarpal joint biomechanics. This might be the source for long term degenerative changes of the wrist joint. Therefore, restoration of the normal shape of the distal radius is likely to improve radio-carpal motion and to minimize the risk for posttraumatic arthritis.
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Acknowledgements The Medical University Innsbruck is acknowledged for funding of parts of the project with the MUI START grant. Christoph Kohstall is acknowledged for his help with programming and valuable comments on the test setup. References Anderson, D.D., Bell, A.L., Gaffney, M.B., Imbriglia, J.E., 1996. Contact stress distributions in malreduced intraarticular distal radius fractures. J. Orthop. Trauma 10, 331–337. Anderson, D.D., Deshpande, B.R., Daniel, T.E., Baratz, M.E., 2005. A three-dimensional finite element model of the radiocarpal joint: distal radius fracture step-off and stress transfer. Iowa Orthop. J. 25, 108–117. Baratz, M.E., Des Jardins, J., Anderson, D.D., Imbriglia, J.E., 1996. Displaced intra-articular fractures of the distal radius: the effect of fracture displacement on contact stresses in a cadaver model. J. Hand Surg. Am. 21, 183–188. Berger, R.A., Bishop, A.T., Bettinger, P.C., 1995. New dorsal capsulotomy for the surgical exposure of the wrist. Ann. Plast. Surg. 35, 54–59. Brand, P.W., 1985. Clinical Mechanics of the Hand, St. Louis, C. V. Mosby. Brand, P.W., Beach, R.B., Thompson, D.E., 1981. Relative tension and potential excursion of muscles in the forearm and hand. J. Hand Surg. Am. 6, 209–219. Bushnell, B.D., Bynum, D.K., 2007. Malunion of the distal radius. J. Am. Acad. Orthop. Surg. 15, 27–40. Carrigan, S.D., Whiteside, R.A., Pichora, D.R., Small, C.F., 2003. Development of a threedimensional finite element model for carpal load transmission in a static neutral posture. Ann. Biomed. Eng. 31, 718–725. Chen, N.C., Jupiter, J.B., 2007. Management of distal radial fractures. J. Bone Joint Surg. Am. 89, 2051–2062. Del Pinal, F., Cagigal, L., Garcia-Bernal, F.J., Studer, A., Regalado, J., Thams, C., 2010. Arthroscopically guided osteotomy for management of intra-articular distal radius malunions. J. Hand Surg. Am. 35, 392–397. Erhart, S., Lutz, M., Arora, R., Schmoelz, W., 2011. Measurement of intraarticular wrist joint biomechanics with a force controlled system. Med. Eng, Phys. (Oct 27, Electronic publication ahead of print). Fernandez, D.L., 1982. Correction of post-traumatic wrist deformity in adults by osteotomy, bone-grafting, and internal fixation. J. Bone Joint Surg. Am. 64, 1164–1178. Fernandez, D.L., Geissler, W.B., 1991. Treatment of displaced articular fractures of the radius. J. Hand Surg. Am. 16, 375–384. Giunta, R.E., Biemer, E., Muller-Gerbl, M., 2004. Ulnar variance and subchondral bone mineralization patterns in the distal articular surface of the radius. J. Hand Surg. Am. 29, 835–840.
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Goldfarb, C.A., Rudzki, J.R., Catalano, L.W., Hughes, M., Borrelli Jr., J., 2006. Fifteen-year outcome of displaced intra-articular fractures of the distal radius. J. Hand Surg. Am. 31, 633–639. Hirahara, H., Neale, P.G., Lin, Y.T., Cooney, W.P., An, K.N., 2003. Kinematic and torquerelated effects of dorsally angulated distal radius fractures and the distal radial ulnar joint. J. Hand Surg. Am. 28, 614–621. Jupiter, J.B., Lipton, H., 1993. The operative treatment of intraarticular fractures of the distal radius. Clin. Orthop. Relat. Res. 48–61. Knirk, J.L., Jupiter, J.B., 1986. Intra-articular fractures of the distal end of the radius in young adults. J. Bone Joint Surg. Am. 68, 647–659. Lutz, M., Rudisch, A., Kralinger, F., Smekal, V., Goebel, G., Gabl, M., Pechlaner, S., 2005. Sagittal wrist motion of carpal bones following intraarticular fractures of the distal radius. J. Hand Surg. Br. 30, 282–287. Martineau, P.A., Waitayawinyu, T., Malone, K.J., Hanel, D.P., Trumble, T.E., 2008. Volar plating of AO C3 distal radius fractures: biomechanical evaluation of locking screw and locking smooth peg configurations. J. Hand Surg. Am. 33, 827–834. Medoff, R.J., 2005. Essential radiographic evaluation for distal radius fractures. Hand Clin. 21, 279–288. Melone Jr., C.P., 1993. Distal radius fractures: patterns of articular fragmentation. Orthop. Clin. North Am. 24, 239–253. Pogue, D.J., Viegas, S.F., Patterson, R.M., Peterson, P.D., Jenkins, D.K., Sweo, T.D., Hokanson, J.A., 1990. Effects of distal radius fracture malunion on wrist joint mechanics. J. Hand Surg. Am. 15, 721–727. Prommersberger, K.J., Froehner, S.C., Schmitt, R.R., Lanz, U.B., 2004. Rotational deformity in malunited fractures of the distal radius. J. Hand Surg. Am. 29, 110–115. Short, W.H., Werner, F.W., Fortino, M.D., Mann, K.A., 1997. Analysis of the kinematics of the scaphoid and lunate in the intact wrist joint. Hand Clin. 13, 93–108. Short, W.H., Werner, F.W., Green, J.K., Weiner, M.M., Masaoka, S., 2002. The effect of sectioning the dorsal radiocarpal ligament and insertion of a pressure sensor into the radiocarpal joint on scaphoid and lunate kinematics. J. Hand Surg. Am. 27, 68–76. Tang, P., Gauvin, J., Muriuki, M., Pfaeffle, J.H., Imbriglia, J.E., Goitz, R.J., 2009. Comparison of the “contact biomechanics” of the intact and proximal row carpectomy wrist. J. Hand Surg. Am. 34, 660–670. Trumble, T.E., Schmitt, S.R., Vedder, N.B., 1994. Factors affecting functional outcome of displaced intra-articular distal radius fractures. J. Hand Surg. Am. 19, 325–340. Wagner Jr., W.F., Tencer, A.F., Kiser, P., Trumble, T.E., 1996. Effects of intra-articular distal radius depression on wrist joint contact characteristics. J. Hand Surg. Am. 21, 554–560. Weiss, K.E., Rodner, C.M., 2007. Osteoarthritis of the wrist. J. Hand Surg. Am. 32, 725–746. Werner, F.W., Palmer, A.K., Somerset, J.H., Tong, J.J., Gillison, D.B., Fortino, M.D., Short, W.H., 1996. Wrist joint motion simulator. J. Orthop. Res. 14, 639–646.