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THE USE OF THE MOTION ANALYSIS SYSTEM FOR EVALUATION OF LOSS OF MOVEMENT IN THE FINGER
THE USE OF THE MOTION ANALYSIS SYSTEM FOR EVALUATION OF LOSS OF MOVEMENT IN THE FINGER H-Y. CHIU, S-C. LIN, F. C. SU, S-T. WANG and H-Y. HSU From the Section of Plastic Surgery, Department of Surgery, the Institute of Biomedical Engineering and the Department of Public Health, National Cheng-Kung University, Tainan, Taiwan, Republic of China
We have used the motion analysis system to measure loss of ®nger movement after injury. The motion analysis system can provide information about the dynamic angular changes of each ®nger joint and the ®ngertip motion area for the injured ®nger. The latter can be used to calculate the percentage of ®ngertip motion area preserved. A sti ®nger may show limited ®ngertip motion area with the ®nger joints tending to ¯ex and extend together. Journal of Hand Surgery (British and European Volume, 2000) 25B: 2: 195±199
Several methods have been suggested for evaluating loss of ®nger motion. The simplest is a linear measurement from the ®ngertip to the distal palmar crease (Boyes, 1955). The total active motion and total passive motion ranges (TAM, TPM) have been used to assess digital performance, especially after ¯exor tendon repair (Strickland, 1985). Direct measurement of the active range of motion (AROM) of each ®nger joint with a goniometer can express the mobility of each ®nger joint but the actual function of a ®nger cannot be fully represented by these angular measurements. The percentage loss of motion in a ®nger can be calculated through a complex combination of the measured ®nger joint motion using ®nger motion impairment tables described by Swanson et al. (1987). Computer-aided motion analysis instrumentation has been designed to provide objective measurements of the motion of body segments. A video-based motion analysis system has been used to evaluate the upperextremity performance in athletes and musicians (An and Bejjani, 1990; Harding et al., 1993) and the initiation and sequence of digital joint motion (Somia et al., 1998). The motion analysis system has been used to evaluate ®ngertip motion in patients with hand injuries (Chiu and Su, 1996). The curve derived from the motion analysis system and the area calculated from it can be compared in serial examinations. This method has been further modi®ed to record simultaneously the dynamic angular changes in each ®nger joint during the ®ngertip motion area study in normal individuals (Chiu et al., 1998b). The present study was conducted to assess the usefulness of the motion analysis system for evaluation of loss of ®nger motion by measuring the range of motion of each ®nger joint and the ®ngertip motion area. The percentage of ®nger motion impairment after injury was computed from the ®nger function impairment tables of Swanson et al. (1987) or as a percentage of normal ®ngertip motion area (Chiu and Su, 1996; Chiu et al., 1998a). The correlation between the percentages of impairment assessed by the two methods was examined.
PATIENTS AND METHODS Thirty-three ®ngers from 12 patients (three women and nine men) with various injuries were included in this study. Their ages ranged from 19 to 64 years, with a mean of 40.5 years. Seven of the 33 digits had been replanted after total amputation, two had soft tissue avulsion injuries, 11 had ¯exor tendon repairs and 13 underwent reduction and ®xation of fractures (three digits in this group also had a tendon repair during the operation). The movements in these injured ®ngers, after a period of 3 to 6 months of rehabilitation, were measured by goniometer and also by the motion analysis system. The AROM of each joint of the injured ®nger was measured by goniometer ®rst. The injured ®nger was then evaluated using the Expert Vision motion analysis system (Motion Analysis Corporation, Santa Rosa, CA, USA) with eight external retrore¯ective markers placed on the dorsal surface of the examined hand. The patient was asked to adopt ®ve postures during the video evaluations. The placing of the markers, the recording of ®nger motion and the data processing have been described previously (Chiu and Su, 1996; Chiu et al., 1998b). The calculated joint angles during each motion cycle were plotted in sequence as shown in Figures 1 to 3. The maximum and minimum recorded angles were used to calculate the AROM of each joint in the examined ®nger. The percentage of the ®nger motion impairment was calculated from the AROM of each ®nger joint measured by goniometer and the ®nger motor impairment tables of Swanson et al. (1987), or from the ®ngertip motion area measured by the motion analysis system which was expressed as a percentage of the estimated normal ®ngertip motion area, calculated from the ®nger length (Chiu et al., 1998a). Statistical analysis We used the method of Bland and Altman (1986) to assess the agreement between the measurements in the three ®nger joints using the goniometer and the motion 195
196
THE JOURNAL OF HAND SURGERY VOL. 25B No. 2 APRIL 2000
Fig 2 The motion analysis results in case 2. Fig 1 The motion analysis results in case 1.
analysis system. Each patient had two angular measurements, one using a goniometer and the other from the motion analysis system. Limits of agreement [Mean (2SD)] based on the dierences between the paired data were calculated. At least 97.5% of the data points will fall within these limits (Mendenhall et al., 1981). This allowed us to assess the degree of agreement. The Wilcoxon signed rank test was used to compare the paired data for assessing relative bias. The correlation between the percentages of ®nger motion impairment determined by goniometry and the motion analysis system was computed using the Pearson product moment. The associated 95% con®dence intervals were calculated using the Fisher-Z transformation.
RESULTS The AROM of each joint in the injured ®ngers measured by the motion analysis system and goniometry and the
dierences in these paired measurements are summarized in Table 1. The limits of agreement [Mean (2SD)] between these angular measurements were calculated as 18(30), 9(25), and 1(17) for metacarpophalangeal (MP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints respectively. Figure 4 displays the dierence in angular measurements between the two methods against their means. This allows us to investigate any possible relationship between the reproducibility and true value. Since the true value is unknown, the mean of the two measurements is the best estimate we have. The mean dierence for the DIP joint did not reach statistical signi®cance, but those for PIP and MP joints did (P50.05). The loss of ®nger motion calculated from the goniometer measurements and the tables of Swanson et al. (1987) correlated well with that calculated from the ®ngertip motion area (r70.87, P50.001). The associated 95% con®dence interval was 70.93 to 70.74. Figure 5 displays the percentage of the ®ngertip
MOTION ANALYSIS SYSTEM
197
Fig 3 The motion analysis results in case 3.
motion area against the percentage of impairment by goniometer. The results of motion analysis data for some representative cases with poor, fair and good functional recovery in the injured ®nger are shown in Figures 1 to 3.
Fig 4 The agreements of the joint angle measurement between the goniometer and motion analysis system. (a) MP joint, (b) PIP joint, (c) DIP joint.
Case 1 A 49-year-old man was referred with a sti left index ®nger which had been injured 6 months previously and Table 1ÐData of the AROM of joints of the injured ®nger measured by motion analysis system and goniometer. Mean (SD) Joint
Sample size
Motion analysis
Goniometer
Dierence
MPJ PIPJ DIPJ
33 33 33
78(30) 69(37) 40(19)
60(24) 60(31) 39(22)
18(15)* 9(12)* 1(9)
Wilcoxon signed rank test was used to assess the dierences of paired angular measurements (*P50.05).
treated by a Chinese bone setter. Physical examination revealed limited active range of motion in the injured ®nger. Hand radiographs showed a malunion of a fracture of the base of the proximal phalanx. After 3 months rehabilitation, the injured ®nger was assessed by goniometry and the motion analysis system. The AROM of the injured ®nger joints measured by goniometer were 0 to 608, 10 to 658 and 5 to 358 for the MP, PIP and DIP joints respectively. The results measured by motion analysis system are shown in Figure 1. The MP, PIP and DIP joints ¯exed and extended synchronously without separate motion. The
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THE JOURNAL OF HAND SURGERY VOL. 25B No. 2 APRIL 2000
done at another hospital. He was referred to our hand clinic 1 month later for further care. After 4 months rehabilitation, the AROM of the injured ®nger joints measured by goniometer were 0 to 908, 5 to 958 and 0 to 558 for the MP, PIP and DIP joints respectively. The results measured by the motion analysis system are shown in Figure 3. Good individual movements in the MP, PIP and DIP joints of the injured ®nger were noted. The calculated functional impairment was 15% by goniometry. The ®ngertip motion area was 81% of the normal ®ngertip motion area. DISCUSSION
Fig 5 The percentage of normal ®ngertip motion area plotted against the percentage of impairment calculated from goniometry in each injured ®nger.
functional impairment calculated from the goniometer measurements and the tables of Swanson et al. (1987) was 39%. The ®ngertip motion area was quite small, representing only 2% of the normal ®ngertip motion area. Case 2 A 54-year-old woman was referred 1 month after a crush injury which resulted in an intra-articular comminuted fracture of the head of the proximal phalanx of the right long ®nger. The injured ®nger had been splinted during this period. After 4 months rehabilitation, the injured ®nger was assessed by goniometry and the motion analysis system. The AROM of the injured ®nger joints measured by goniometer were 0 to 858, 15 to 858 and 0 to 408 for the MP, PIP and DIP joints respectively. The results measured by the motion analysis system are shown in Figure 2. Separate motion in the MP, PIP and DIP joints of the injured ®nger was noted but was poor. The calculated functional impairment was 33% by goniometry. The ®ngertip motion area was 25% of the normal ®ngertip motion area. Case 3 A 24-year-old man sustained a crush injury of the left distal forearm with distal radial and ulnar fractures and division of the ¯exor digitorum super®cialis. Open reduction with internal ®xation and tendon repairs were
The conventional goniometer is a simple and useful tool. It oers a convenient way of measuring the range of motion in the ®nger joints, but this measurement is a static one in which the AROM is measured in a position of ¯exion or extension of all the ®nger joints. The patient might in¯uence the measurements by forceful ¯exion or extension of the ®nger joint that is being measured. In contrast, the recording of the AROM of ®nger by the motion analysis system is accomplished by freely moving the ®nger along a ®xed motion cycle without contact between the ®nger and the device. The motion track pro®le is composed of various combinations of ¯exion and extension of the MP, PIP and DIP joints. Therefore, the motion analysis system can record and demonstrate the dynamic changes in the angles in all three ®nger joints continuously during motion of the ®nger. Analysis of the angular measurements evaluated by the goniometry and the motion analysis system showed poorer agreement for the MP and PIP joints. The Wilcoxon signed rank statistics also indicated signi®cantly larger biases between the goniometric measurements for these two joints. The more proximal the ®nger joint, the poorer was the agreement. The larger dierences in PIP and MP joint movements shown in Figure 4 can be explained by the following facts. First, the motion pro®le for the assessment by motion analysis includes the intrinsic minus posture. The intrinsic minus posture may produce better PIP joint ¯exion and MP joint hyperextension recordings than a position of ¯exion and extension of all the ®nger joints. The recordings of AROM of the PIP and MP joints demonstrate this (time frame 125 s) (Fig 3). Secondly, this study was conducted with injured ®ngers in contrast to the previous study using a similar comparison in normal individuals (Chiu et al., 1998b). We found that in some cases there was hypermobility of a proximal joint to compensate for a sti distal joint (such as hyperextension of the MP joint) during motion. This is dicult to reveal by conventional goniometry but can be well demonstrated on the ®nger joint motion curve produced by the motion analysis system (time frame 125 s) (Fig 3).
MOTION ANALYSIS SYSTEM
During the motion analysis evaluation, each patient was asked to adopt ®ve postures so the joints of each ®nger would show separate ¯exion and extension at dierent time frames on the ®gure. The MP joint angle would increase (MP joint ¯exion) ®rst to its full amount (time frame 0±45 s) (Fig 3), followed by a rise in the PIP joint recording (PIP joint ¯exion) and a rise in the DIP joint recording (DIP joint ¯exion) a little later (time frame 45±70 s) (Fig 3). While keeping the PIP and DIP joints in ¯exion, the MP joint recording decreases (MP joint extension) ®rst (time frame 90±125 s) (Fig 3), followed by a decrease in the PIP and DIP joint recordings (PIP and DIP joints extending together) (time frame 125±150 s) (Fig 3). A sti ®nger showed ¯exion and extension of the joints together on the ®nger joint angle record. This was considered to be due to scarring around the tendons preventing separate joint motion (time frames 100±150 s, 350±400 s) (Fig 1). In contrast, an injured ®nger with better recovery showed a better separation of joint motion on the recording (Fig 2). The percentage of ®nger motion remaining can be calculated from the actual ®ngertip motion area of the injured ®nger divided by the estimated normal ®ngertip motion area (square of the injured ®nger length multiplied by 0.677) (Chiu et al., 1998a). This percentage of preservation of ®nger motion was compared to the motor impairment results calculated from goniometry. The correlation between these two impairment percentages is good when the percentage of impairment by goniometry is less than 40%, but above this value the correlation is very weak (Fig 5). It is dicult to decide which evaluation method is more accurate, but at least the functional preservation percentage of ®ngertip motion area is derived from a direct measurement.
199
The motion analysis evaluation is time-consuming. However, we believe that this system can provide useful data about the actual anatomical de®cits in the injured ®ngers. Acknowledgements This work was supported by grant NSC 86-2314-B006-063, from National Science Council of the Republic of China.
References An K-N, Bejjani FJ (1990). Analysis of upper-extremity performance in athletes and musicians. Hand Clinics, 6: 393±403. Bland JM, Altman DG (1986). Statistical methods for assessing agreement between two methods of clinical measurement. Lancet, 1: 307±310. Boyes JH (1955). Evaluation of results of digital ¯exor tendon grafts. American Journal of Surgery, 89: 1116±1119. Chiu H-Y, Su FC (1996). The motion analysis system and the maximal area of ®ngertip motion. Journal of Hand Surgery, 21B: 604±608. Chiu H-Y, Su FC, Wang S-T (1998a). The motion analysis system and the ®ngertip motion area: normal values in young adults. Journal of Hand Surgery, 23B: 53±56. Chiu H-Y, Su FC, Wang S-T, Hsu H-Y (1998b). The motion analysis system and goniometry of the ®nger joints. Journal of Hand Surgery, 23B: 788±791. Harding DC, Brandt KD, Hillberry BM (1993). Finger joint force minimization in pianists using optimization techniques. Journal of Biomechanics, 26: 1403±1412. Mendenhall W, Scheaer RL, Wackerly DD. Mathematical statistics with applications, 2nd edn. Boston, Duxbury Press, 1981: 159±160. Somia N, Rash GS, Wachowiak M, Gupta A (1998). The initiation and sequence of digital joint motion ± a three dimensional motion analysis. Journal of Hand Surgery, 23B: 792±795. Strickland JW (1985). Results of ¯exor tendon surgery in Zone II. Hand Clinics, 1: 167±179. Swanson AB, Goran-Hagert C, de Groot Swanson G (1987). Evaluation of impairment in the upper extremity. Journal of Hand Surgery, 12A: 896±926. Received: 12 March 1999 Accepted after revision: 25 October 1999 H-Y. Chiu MD, Section of Plastic Surgery, Department of Surgery, National Cheng-Kung University, 138 Sheng Li Road, Tainan, Taiwan, Republic of China. E-mail: [email protected] # 2000 The British Society for Surgery of the Hand DOI: 10.1054/jhsb.1999.0344, available online at http://www.idealibrary.com on
We have used the motion analysis system to measure loss of ®nger movement after injury. The motion analysis system can provide information about the dynamic angular changes of each ®nger joint and the ®ngertip motion area for the injured ®nger. The latter can be used to calculate the percentage of ®ngertip motion area preserved. A sti ®nger may show limited ®ngertip motion area with the ®nger joints tending to ¯ex and extend together. Journal of Hand Surgery (British and European Volume, 2000) 25B: 2: 195±199
Several methods have been suggested for evaluating loss of ®nger motion. The simplest is a linear measurement from the ®ngertip to the distal palmar crease (Boyes, 1955). The total active motion and total passive motion ranges (TAM, TPM) have been used to assess digital performance, especially after ¯exor tendon repair (Strickland, 1985). Direct measurement of the active range of motion (AROM) of each ®nger joint with a goniometer can express the mobility of each ®nger joint but the actual function of a ®nger cannot be fully represented by these angular measurements. The percentage loss of motion in a ®nger can be calculated through a complex combination of the measured ®nger joint motion using ®nger motion impairment tables described by Swanson et al. (1987). Computer-aided motion analysis instrumentation has been designed to provide objective measurements of the motion of body segments. A video-based motion analysis system has been used to evaluate the upperextremity performance in athletes and musicians (An and Bejjani, 1990; Harding et al., 1993) and the initiation and sequence of digital joint motion (Somia et al., 1998). The motion analysis system has been used to evaluate ®ngertip motion in patients with hand injuries (Chiu and Su, 1996). The curve derived from the motion analysis system and the area calculated from it can be compared in serial examinations. This method has been further modi®ed to record simultaneously the dynamic angular changes in each ®nger joint during the ®ngertip motion area study in normal individuals (Chiu et al., 1998b). The present study was conducted to assess the usefulness of the motion analysis system for evaluation of loss of ®nger motion by measuring the range of motion of each ®nger joint and the ®ngertip motion area. The percentage of ®nger motion impairment after injury was computed from the ®nger function impairment tables of Swanson et al. (1987) or as a percentage of normal ®ngertip motion area (Chiu and Su, 1996; Chiu et al., 1998a). The correlation between the percentages of impairment assessed by the two methods was examined.
PATIENTS AND METHODS Thirty-three ®ngers from 12 patients (three women and nine men) with various injuries were included in this study. Their ages ranged from 19 to 64 years, with a mean of 40.5 years. Seven of the 33 digits had been replanted after total amputation, two had soft tissue avulsion injuries, 11 had ¯exor tendon repairs and 13 underwent reduction and ®xation of fractures (three digits in this group also had a tendon repair during the operation). The movements in these injured ®ngers, after a period of 3 to 6 months of rehabilitation, were measured by goniometer and also by the motion analysis system. The AROM of each joint of the injured ®nger was measured by goniometer ®rst. The injured ®nger was then evaluated using the Expert Vision motion analysis system (Motion Analysis Corporation, Santa Rosa, CA, USA) with eight external retrore¯ective markers placed on the dorsal surface of the examined hand. The patient was asked to adopt ®ve postures during the video evaluations. The placing of the markers, the recording of ®nger motion and the data processing have been described previously (Chiu and Su, 1996; Chiu et al., 1998b). The calculated joint angles during each motion cycle were plotted in sequence as shown in Figures 1 to 3. The maximum and minimum recorded angles were used to calculate the AROM of each joint in the examined ®nger. The percentage of the ®nger motion impairment was calculated from the AROM of each ®nger joint measured by goniometer and the ®nger motor impairment tables of Swanson et al. (1987), or from the ®ngertip motion area measured by the motion analysis system which was expressed as a percentage of the estimated normal ®ngertip motion area, calculated from the ®nger length (Chiu et al., 1998a). Statistical analysis We used the method of Bland and Altman (1986) to assess the agreement between the measurements in the three ®nger joints using the goniometer and the motion 195
196
THE JOURNAL OF HAND SURGERY VOL. 25B No. 2 APRIL 2000
Fig 2 The motion analysis results in case 2. Fig 1 The motion analysis results in case 1.
analysis system. Each patient had two angular measurements, one using a goniometer and the other from the motion analysis system. Limits of agreement [Mean (2SD)] based on the dierences between the paired data were calculated. At least 97.5% of the data points will fall within these limits (Mendenhall et al., 1981). This allowed us to assess the degree of agreement. The Wilcoxon signed rank test was used to compare the paired data for assessing relative bias. The correlation between the percentages of ®nger motion impairment determined by goniometry and the motion analysis system was computed using the Pearson product moment. The associated 95% con®dence intervals were calculated using the Fisher-Z transformation.
RESULTS The AROM of each joint in the injured ®ngers measured by the motion analysis system and goniometry and the
dierences in these paired measurements are summarized in Table 1. The limits of agreement [Mean (2SD)] between these angular measurements were calculated as 18(30), 9(25), and 1(17) for metacarpophalangeal (MP), proximal interphalangeal (PIP) and distal interphalangeal (DIP) joints respectively. Figure 4 displays the dierence in angular measurements between the two methods against their means. This allows us to investigate any possible relationship between the reproducibility and true value. Since the true value is unknown, the mean of the two measurements is the best estimate we have. The mean dierence for the DIP joint did not reach statistical signi®cance, but those for PIP and MP joints did (P50.05). The loss of ®nger motion calculated from the goniometer measurements and the tables of Swanson et al. (1987) correlated well with that calculated from the ®ngertip motion area (r70.87, P50.001). The associated 95% con®dence interval was 70.93 to 70.74. Figure 5 displays the percentage of the ®ngertip
MOTION ANALYSIS SYSTEM
197
Fig 3 The motion analysis results in case 3.
motion area against the percentage of impairment by goniometer. The results of motion analysis data for some representative cases with poor, fair and good functional recovery in the injured ®nger are shown in Figures 1 to 3.
Fig 4 The agreements of the joint angle measurement between the goniometer and motion analysis system. (a) MP joint, (b) PIP joint, (c) DIP joint.
Case 1 A 49-year-old man was referred with a sti left index ®nger which had been injured 6 months previously and Table 1ÐData of the AROM of joints of the injured ®nger measured by motion analysis system and goniometer. Mean (SD) Joint
Sample size
Motion analysis
Goniometer
Dierence
MPJ PIPJ DIPJ
33 33 33
78(30) 69(37) 40(19)
60(24) 60(31) 39(22)
18(15)* 9(12)* 1(9)
Wilcoxon signed rank test was used to assess the dierences of paired angular measurements (*P50.05).
treated by a Chinese bone setter. Physical examination revealed limited active range of motion in the injured ®nger. Hand radiographs showed a malunion of a fracture of the base of the proximal phalanx. After 3 months rehabilitation, the injured ®nger was assessed by goniometry and the motion analysis system. The AROM of the injured ®nger joints measured by goniometer were 0 to 608, 10 to 658 and 5 to 358 for the MP, PIP and DIP joints respectively. The results measured by motion analysis system are shown in Figure 1. The MP, PIP and DIP joints ¯exed and extended synchronously without separate motion. The
198
THE JOURNAL OF HAND SURGERY VOL. 25B No. 2 APRIL 2000
done at another hospital. He was referred to our hand clinic 1 month later for further care. After 4 months rehabilitation, the AROM of the injured ®nger joints measured by goniometer were 0 to 908, 5 to 958 and 0 to 558 for the MP, PIP and DIP joints respectively. The results measured by the motion analysis system are shown in Figure 3. Good individual movements in the MP, PIP and DIP joints of the injured ®nger were noted. The calculated functional impairment was 15% by goniometry. The ®ngertip motion area was 81% of the normal ®ngertip motion area. DISCUSSION
Fig 5 The percentage of normal ®ngertip motion area plotted against the percentage of impairment calculated from goniometry in each injured ®nger.
functional impairment calculated from the goniometer measurements and the tables of Swanson et al. (1987) was 39%. The ®ngertip motion area was quite small, representing only 2% of the normal ®ngertip motion area. Case 2 A 54-year-old woman was referred 1 month after a crush injury which resulted in an intra-articular comminuted fracture of the head of the proximal phalanx of the right long ®nger. The injured ®nger had been splinted during this period. After 4 months rehabilitation, the injured ®nger was assessed by goniometry and the motion analysis system. The AROM of the injured ®nger joints measured by goniometer were 0 to 858, 15 to 858 and 0 to 408 for the MP, PIP and DIP joints respectively. The results measured by the motion analysis system are shown in Figure 2. Separate motion in the MP, PIP and DIP joints of the injured ®nger was noted but was poor. The calculated functional impairment was 33% by goniometry. The ®ngertip motion area was 25% of the normal ®ngertip motion area. Case 3 A 24-year-old man sustained a crush injury of the left distal forearm with distal radial and ulnar fractures and division of the ¯exor digitorum super®cialis. Open reduction with internal ®xation and tendon repairs were
The conventional goniometer is a simple and useful tool. It oers a convenient way of measuring the range of motion in the ®nger joints, but this measurement is a static one in which the AROM is measured in a position of ¯exion or extension of all the ®nger joints. The patient might in¯uence the measurements by forceful ¯exion or extension of the ®nger joint that is being measured. In contrast, the recording of the AROM of ®nger by the motion analysis system is accomplished by freely moving the ®nger along a ®xed motion cycle without contact between the ®nger and the device. The motion track pro®le is composed of various combinations of ¯exion and extension of the MP, PIP and DIP joints. Therefore, the motion analysis system can record and demonstrate the dynamic changes in the angles in all three ®nger joints continuously during motion of the ®nger. Analysis of the angular measurements evaluated by the goniometry and the motion analysis system showed poorer agreement for the MP and PIP joints. The Wilcoxon signed rank statistics also indicated signi®cantly larger biases between the goniometric measurements for these two joints. The more proximal the ®nger joint, the poorer was the agreement. The larger dierences in PIP and MP joint movements shown in Figure 4 can be explained by the following facts. First, the motion pro®le for the assessment by motion analysis includes the intrinsic minus posture. The intrinsic minus posture may produce better PIP joint ¯exion and MP joint hyperextension recordings than a position of ¯exion and extension of all the ®nger joints. The recordings of AROM of the PIP and MP joints demonstrate this (time frame 125 s) (Fig 3). Secondly, this study was conducted with injured ®ngers in contrast to the previous study using a similar comparison in normal individuals (Chiu et al., 1998b). We found that in some cases there was hypermobility of a proximal joint to compensate for a sti distal joint (such as hyperextension of the MP joint) during motion. This is dicult to reveal by conventional goniometry but can be well demonstrated on the ®nger joint motion curve produced by the motion analysis system (time frame 125 s) (Fig 3).
MOTION ANALYSIS SYSTEM
During the motion analysis evaluation, each patient was asked to adopt ®ve postures so the joints of each ®nger would show separate ¯exion and extension at dierent time frames on the ®gure. The MP joint angle would increase (MP joint ¯exion) ®rst to its full amount (time frame 0±45 s) (Fig 3), followed by a rise in the PIP joint recording (PIP joint ¯exion) and a rise in the DIP joint recording (DIP joint ¯exion) a little later (time frame 45±70 s) (Fig 3). While keeping the PIP and DIP joints in ¯exion, the MP joint recording decreases (MP joint extension) ®rst (time frame 90±125 s) (Fig 3), followed by a decrease in the PIP and DIP joint recordings (PIP and DIP joints extending together) (time frame 125±150 s) (Fig 3). A sti ®nger showed ¯exion and extension of the joints together on the ®nger joint angle record. This was considered to be due to scarring around the tendons preventing separate joint motion (time frames 100±150 s, 350±400 s) (Fig 1). In contrast, an injured ®nger with better recovery showed a better separation of joint motion on the recording (Fig 2). The percentage of ®nger motion remaining can be calculated from the actual ®ngertip motion area of the injured ®nger divided by the estimated normal ®ngertip motion area (square of the injured ®nger length multiplied by 0.677) (Chiu et al., 1998a). This percentage of preservation of ®nger motion was compared to the motor impairment results calculated from goniometry. The correlation between these two impairment percentages is good when the percentage of impairment by goniometry is less than 40%, but above this value the correlation is very weak (Fig 5). It is dicult to decide which evaluation method is more accurate, but at least the functional preservation percentage of ®ngertip motion area is derived from a direct measurement.
199
The motion analysis evaluation is time-consuming. However, we believe that this system can provide useful data about the actual anatomical de®cits in the injured ®ngers. Acknowledgements This work was supported by grant NSC 86-2314-B006-063, from National Science Council of the Republic of China.
References An K-N, Bejjani FJ (1990). Analysis of upper-extremity performance in athletes and musicians. Hand Clinics, 6: 393±403. Bland JM, Altman DG (1986). Statistical methods for assessing agreement between two methods of clinical measurement. Lancet, 1: 307±310. Boyes JH (1955). Evaluation of results of digital ¯exor tendon grafts. American Journal of Surgery, 89: 1116±1119. Chiu H-Y, Su FC (1996). The motion analysis system and the maximal area of ®ngertip motion. Journal of Hand Surgery, 21B: 604±608. Chiu H-Y, Su FC, Wang S-T (1998a). The motion analysis system and the ®ngertip motion area: normal values in young adults. Journal of Hand Surgery, 23B: 53±56. Chiu H-Y, Su FC, Wang S-T, Hsu H-Y (1998b). The motion analysis system and goniometry of the ®nger joints. Journal of Hand Surgery, 23B: 788±791. Harding DC, Brandt KD, Hillberry BM (1993). Finger joint force minimization in pianists using optimization techniques. Journal of Biomechanics, 26: 1403±1412. Mendenhall W, Scheaer RL, Wackerly DD. Mathematical statistics with applications, 2nd edn. Boston, Duxbury Press, 1981: 159±160. Somia N, Rash GS, Wachowiak M, Gupta A (1998). The initiation and sequence of digital joint motion ± a three dimensional motion analysis. Journal of Hand Surgery, 23B: 792±795. Strickland JW (1985). Results of ¯exor tendon surgery in Zone II. Hand Clinics, 1: 167±179. Swanson AB, Goran-Hagert C, de Groot Swanson G (1987). Evaluation of impairment in the upper extremity. Journal of Hand Surgery, 12A: 896±926. Received: 12 March 1999 Accepted after revision: 25 October 1999 H-Y. Chiu MD, Section of Plastic Surgery, Department of Surgery, National Cheng-Kung University, 138 Sheng Li Road, Tainan, Taiwan, Republic of China. E-mail: [email protected] # 2000 The British Society for Surgery of the Hand DOI: 10.1054/jhsb.1999.0344, available online at http://www.idealibrary.com on