- Email: [email protected]
An Experimental Study Comparing Active Mobilization to Passive Flexion–Active Extension–Active Flexion After Flexor Tendon Repair in Zone 2
SCIENTIFIC ARTICLE
An Experimental Study Comparing Active Mobilization to Passive Flexion–Active Extension–Active Flexion After Flexor Tendon Repair in Zone 2 Hongliang Lee, MD, Zhidian Hou, MD, PhD, Peng Liu, MD, Yang Lee, MD, Zihai Ding, MD, Xuefeng Zheng, MD
Purpose Both passive flexion–active extension and active rehabilitation have shown advantages and disadvantages in tendon healing. The purpose of this study was to measure the effect of a combination of these 2 rehabilitation protocols. Methods A tendon injury model was used in white Leghorn chickens. Thirty-two animals were randomly assigned into 4 groups. We compared an unrestricted active flexion rehabilitation (UA) group with 3 groups starting passive flexion, active extension, and active flexion (PAA) at 5, 9.5 and 14 days after repair. The tensile properties and range of motion of the 3 interphalangeal joints were evaluated for 3 postoperative weeks. Results In terms of tensile properties of the operated foot, PAA-14 was higher than any other group, and PAA-5 was the lowest. There was no significant difference between the PAA-9.5 and UA. For the range of motion, there were significant differences between all 4 groups: UA increased the most, PAA-14 increased the least, and PAA-5 increased more than PAA-9.5. For the rupture rate, UA and PAA-5 were higher than were PAA-9.5 and PAA-14. Conclusions The results indicate that the PAA-9.5 and UA may give the best balance (tensile properties, range of motion, rupture rates) of these rehabilitation protocols. PPA-9.5 and UA had similar moderate tensile properties. When considering an increased range of motion, the UA method may be the most appropriate despite its higher rupture rate. When considering a lower rupture rate, PAA-9.5 may be the most suitable. (J Hand Surg 2013;38A:672–676. Copyright © 2013 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic III. Key words Biomechanical properties, early mobilization, flexor tendon repair, range of motion, zone 2. HE FULL RECOVERY of digit function remains a difficult clinical problem following zone 2 flexor tendon injuries. Kleinert et al1 developed a passive flexion–active extension regimen, and several authors2– 6 have indicated that protected passive mobi-
T
From the Anatomical Institute of Minimally Invasive Surgery, Southern Medical University, Guangzhou, China. Received for publication August 3, 2012; accepted in revised form January 4, 2013. The authors give special thanks to Zihai Ding for his care and support and to Weidong Zhao for help with the biomechanics. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
672 䉬 © ASSH 䉬 Published by Elsevier, Inc. All rights reserved.
lization can inhibit adhesion formation and improve tendon excursion. Silfverskiöld et al7 suggested that a passive flexion-active extension program had more joint motion and tendon excursion than did a passive regimen clinically. Even so, it still does not produce a Corresponding author: Zihai Ding, MD, Anatomical Institute of Minimally Invasive Surgery, Southern Medical University, No. 1838 Guangzhou Avenue North, Guangzhou, Guangdong 510515 China; e-mail: [email protected]. 0363-5023/13/38A04-0006$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2013.01.020
REHABILITATION FOR REPAIRED TENDON
673
FIGURE 1: A, B Weight was attached to the long toe by a thread so that the tip of the operated toe nearly touched the plantar surface of the foot. The extensor muscles could contract and extend the interphalangeal joints. A, C A dorsal splint held the ankle in 60° of plantar flexion and the metatarsophalangeal joint in 30° of flexion and allowed full interphalangeal joint extension.
satisfactory result. Other authors7–9 indicated that an early active mobilization program with more effective tendon gliding and less adhesion formation10 produces more joint motion but results in unacceptably high rupture rates. Both passive flexion-active extension and active rehabilitation have shown advantages and disadvantages. The purpose of this study was to combine these 2 rehabilitation protocols to identify their ideal balance after flexor tendon repairs in zone 2 at 3 weeks of healing. MATERIALS AND METHODS Animal surgeries and postoperative care All experiment protocols were approved by the local animal care and use committee. Both the housing and surgeries were carried out in facilities meeting the standards of local and national regulatory bodies. Thirtytwo adult white Leghorn chickens (Dahuanong Animal Health Products Co., Ltd., Guangdong, China) weighing 1.3–1.5 kg were anaesthetized by xylazine (5–10 mg/kg, injected intramuscularly), and lidocaine hydrochloride (0.5%, 1 mL) was injected into the third toe of
the left foot. Under aseptic conditions, zigzag incisions were made on the plantar surface of the left third digits over zone 2. The flexor sheath was opened longitudinally between the proximal and distal pulleys. The flexor digitorum profundus tendon was isolated, and a transverse complete laceration was made to both the superficial and deep tendons with a scalpel blade. Under an operating microscope at 10⫻ magnification, only the flexor digitorum profundus tendon was repaired with the modified Kessler11 technique with a 5-0 suture. The sheath was completely repaired using a 7-0 suture, and then the skin was closed. The third digit was then placed in a dorsal low-temperature thermoplastic splint with the ankle plantar flexed at 60°, the metatarsophalangeal joints flexed to 30°, and the interphalangeal joints extended fully (Fig. 1). The unoperated control foot was left free to allow for ambulation. The 32 chickens were randomly assigned into 4 equally sized groups with different rehabilitation regimens. All of the operated digits were immediately immobilized in the splint for 3 days. Twenty- to 60-gram weights attached to the long toe were added gradually until the tip of the operated toe
JHS 䉬 Vol A, April
674
REHABILITATION FOR REPAIRED TENDON
nearly touched the plantar surface of the foot. The extensors were elongated and contraction was not restricted so that the animal could actively extend the digit. The passive flexion, active extension, active flexion (PAA) rehabilitation protocols thus realized passive flexion–active extension first, followed by active mobilization) (Fig. 1). The PAA groups were treated with a passive flexion–active extension regimen at a frequency of 12 cycles/min for 5 min/day, and the splints were removed at 5 days, 9.5 days, or 14 days after surgery, allowing unrestricted active motion. The frequency was instituted by Takai,12 who suggested that higher-frequency, controlled passive motion had a beneficial effect. The unrestricted active motion group (UA) had the splint removed after 3 days and were treated with an unrestricted active mobilization program. At the end of 3 weeks of healing, the animals were injected intramuscularly with a lethal dose of xylazine (20 mg/kg). Both the operated and control feet were harvested and tested biomechanically. Six chickens were not enrolled because of ruptured tendons. Biomechanical evaluation Range of motion: The active range of motion of the 3 interphalangeal joints generated by pulling the tendon with the mechanical testing machine was measured with a goniometer. The flexor digitorum profundus tendon of the third digit was cut free, and the first digit was severed. The remaining 3 digits were then mounted on a board by driving 2 nails into the second and fourth digits. The proximal end of the flexor digitorum profundus tendon of the third digit was held by a clamp from the material testing machine. Fifty grams of weight were attached to the tip of the third digit for full extension. The unoperated specimen was loaded at a constant speed of 0.4 mm/s until the tip of the operated toe nearly touched the plantar surface of the foot; the value (X) of the load was then recorded immediately, as was the range of motion of the 3 interphalangeal joints. The operated specimen was then loaded at a constant speed of 0.4 mm/s until the load increased to X, at which point the range of motion was recorded. Tensile properties: The tendon specimens were carefully dissected from the digits, leaving the tendon and sheath attached to the distal phalanx without disturbing the scar tissue around the sheath. Tensile testing was conducted with a material testing apparatus (Bose Corporation, Eden Prairie, MN). The bone–tendon complex was placed in the tendon clamps, and the proximal tendon was covered with dry gauze to reduce slippage.
TABLE 1. Range of Motion of 3 Interphalangeal Joints for 4 Groups (Operated/Control, %) Joints
PAA-14
PAA-9.5
PAA-5
UA
First IPJ
23 ⫾ 2
45 ⫾ 4
60 ⫾ 3
72 ⫾ 3
Second IPJ
22 ⫾ 3
44 ⫾ 4
61 ⫾ 3
72 ⫾ 3
Third IPJ
27 ⫾ 2
45 ⫾ 4
58 ⫾ 3
69 ⫾ 5
IPJ, interphalangeal joint.
The room temperature was maintained at 25°C, and the specimens were kept moist with a saline solution. The clamp-to-clamp distance was measured as the initial length (D0). The specimen was loaded until failure at a constant speed of 0.4 mm/s, and the load-elongation curve was recorded. To reduce the error produced by different initial tendon lengths, the elongation was normalized by D0, and the result was expressed as the percent elongation. To minimize specimen variability, the operative specimens were normalized using the controls. Tensile properties such as the peak force, stiffness, and energy absorption were recorded using the load-percent elongation curve. Statistical data analysis Statistical analysis was performed using a one-way analysis of variance, with the significance set at P ⱕ .05. RESULTS Rupture rates Rupture of the repaired tendon was observed in 6 chickens during the 3-week healing process—2 in both PPA-5 and UA, and 1 each in both PAA-9.5 and PAA-14. All ruptures occurred at the repair site. Range of motion The values were normalized by calculating operated value divided by control value. All 4 groups had significant between-group differences (P ⬍ .05, summarized in Table 1). Tensile properties Tensile properties of the operated digits were much lower than those of the controls (P ⬍ .001). The stiffness, measured between 15% and 30% of the total elongation; peak force; and energy absorption for both the operated and control tendons are summarized in Table 2. The values were normalized by dividing the operated value by the control value (Table 3).
JHS 䉬 Vol A, April
675
REHABILITATION FOR REPAIRED TENDON
TABLE 2.
The Tensile Properties of Tendon 共x⫾s兲 Peak Force (N)
Groups
No. of Tendons
Control
Operated
Stiffness (N/mm/mm) Control
Energy Absorption (N/mm/mm)
Operated
Control
Operated
PPA-14
7
107 ⫾ 16
37 ⫾ 9
696 ⫾ 224
342 ⫾ 116
13 ⫾ 4
3⫾1
PPA-9.5
7
100 ⫾ 20
14 ⫾ 6
671 ⫾ 164
187 ⫾ 99
9⫾5
0.5 ⫾ 0.4
PPA-5
6
113 ⫾ 21
3⫾1
561 ⫾ 144
60 ⫾ 22
15 ⫾ 7
0.10 ⫾ 0.3
UA
6
102 ⫾ 26
14 ⫾ 7
512 ⫾ 85
113 ⫾ 84
13 ⫾ 6
0.8 ⫾ 0.4
TABLE 3. The Normalized Tensile Properties of Tendon 共x⫾s兲 Groups
No. Tendons
Peak Force (%)
Stiffness (%)
Energy Absorption (%)
PPA-14
7
35 ⫾ 8
49 ⫾ 6
22 ⫾ 4
PPA-9.5
7
14 ⫾ 6
28 ⫾ 12
6⫾3
PPA-5
6
3⫾1
11 ⫾ 4
0.8 ⫾ 0.4
UA
6
14 ⫾ 6
22 ⫾ 15
7⫾3
There were no significant effects on the peak forces or the energy absorptions between PAA-9.5 and UA; therefore, no statistically significant differences were demonstrated between PAA-9.5 and UA for these measures or between PAA-5 and UA in terms of stiffness. Compared to the active flexion program, PAA-14 had higher tensile properties (P ⱕ .005), whereas PAA-5 showed the greatest decrease in it (P ⱕ .005). DISCUSSION The restoration of finger function after flexor tendon injury in zone 2 is particularly difficult, especially for sufficient tendon gliding and full joint motion. Tendon mobilization is frequently used in rehabilitation protocols, and several researchers4,13–15 have advocated that good results are observed in the early mobilization groups, whereas gap formation and tendon rupture emerge in the early active motion groups. There is also some evidence16,17 confirming that early mobilization can improve biological properties. Kleinert et al1 promoted a passive flexion-active extension regimen using a dorsal splint with rubber band traction that was modified to gain increased tendon excursion by improving the range of motion of the proximal and distal interphalangeal joints. Both the completely passive regimen and the passive flexionactive extension protocol are far from optimal. Becker18 suggested that dynamic splinting with passive flexion-
active extension was not able to produce sufficient movement of the repair site. With the appearance of several basic research stud17 ies and clinical evidence8,19,20 supporting active flexion, the importance of early active mobilization has increasingly been recognized. Although several authors have suggested that the early active motion of the flexor tendons has some advantages (less adhesion formation and less flexion deformity) over other regimens of passive flexion, high rupture rates7,16,21–23 of the repaired tendons remain an issue of concern. The fear of early tendon rupture following flexor tendon repair is the main reason that these regimens are not widely accepted by hand surgeons. Some authors24,25 recommended that tendon properties decrease from the 5th day to the 14th day after flexor tendon repair. High rupture rates have been observed during this particular period. We hypothesized that better results may emerge by combining the advantages of the active flexion program (sufficient tendon excursion) and of the passive flexion–active extension motion protocol (lower tendon rupture rates). In our study, we observed that PAA-14 had the highest tensile properties (peak force, stiffness, and energy absorption) and that PAA-5 had the lowest. The active motion protocol (UA) increased the range of motion more than any other group, and PAA-14 increased it the least, whereas PAA-5 increased it more than PAA-9.5. Both the UA and PAA-5 groups had 2 tendon ruptures, and PAA-9.5 and PAA-14 each had 1. Compared to the other groups, the PAA-14 can take a greater load, show a higher stiffness, possess a greater capacity of energy absorption, and maintain a lower rupture rate, but the range of motion is inferior to that of the other 3 groups. The PAA-5 protocol is inferior to the other 3 groups in terms of tensile properties, but it ranks second for increased joint motion. The PAA-9.5 and UA protocols were not significantly different in their tensile properties, but the latter had a better range
JHS 䉬 Vol A, April
676
REHABILITATION FOR REPAIRED TENDON
of joint motion. These results may indicate that the PAA-9.5 and UA groups provide the ideal balance of the combined protocols. These protocols leave surgeons with 2 choices: (1) adopting an active flexion motion regimen, in which doctors must endure a high risk of rupture with the benefit of good joint motion with moderate tensile properties, or (2) adopting a less aggressive motion regimen, such as PAA-9.5, in which there is a low rupture rate and moderate tensile properties but less improvement in joint motion than with UA. Considering that we evaluated motion and tensile strength at just 3 time points between the 5th and 14th day after surgery, it is difficult to say which is the best choice for the postoperative protocol: active flexion or PAA-X. In our study, there were only 8 chickens in each group; the sample size was sufficient to compare the tensile properties, but it was not sufficient to compare the tendon rupture rates among the 4 groups. This is a short-term study, and longer follow-up may produce different results. Because of the limitations of our study, subsequent work is required to determine the ideal regimen for flexor tendon rehabilitation. REFERENCES 1. Kleinert HE, Kurtz JE, Atasoy E, et al. Primary repair of lacerated flexor tendons. Orthop Clin North Am. 1973;4(4):865– 876. 2. Gelberman RH, Amifl D, Gonsalves M, et al. The influence of protected passive mobilization on the healing of flexor tendons: a biochemical and microangiographic study. Hand. 1981;13(6):120 – 128. 3. Gelberman RH, Woo SL, Lothringer K, et al. Effects of early intermittent passive mobilization on healing canine flexor tendons. J Hand Surg Am. 1982;7(2):170 –175. 4. Lister GD, Kleinert HE, Kutz JE, et al. Primary flexor tendon repair followed by immediate controlled mobilization. J Hand Surg Am. 1977;2(6):441– 451. 5. Woo SL, Gelberman RH, Cobb NG, et al. The importance of controlled passive mobilization on flexor tendon healing. A biomechanical study. Acta Orthop Scand. 1981;52(6):615– 622. 6. Gault DT. A review of repaired flexor tendons. J Hand Surg Br. 1987;12(3):321–325. 7. Silfverskiöld KL, May EJ. Flexor tendon repair in zone II with a new suture technique and an early mobilization program combining passive and active flexion. J Hand Surg Am. 1994;19(1):53– 60.
8. Becker H, Orak F, Duponselle E. Early active motion following a beveled technique of flexor tendon repair: report on fifty cases. J Hand Surg Am. 1979;4(5):454 –460. 9. Small JO, Brennen MD, Colville J. Early active mobilization following flexor tendon repair in zone two. J Hand Surg Br. 1989; 14(4):383–391. 10. Gelberman RH, Vandeberg JS, Manske PR, et al. The early stages of flexor tendon healing: a morphologic study of the first fourteen days. J Hand Surg Am. 1985;10(6):776 –784. 11. Kessler. The grasping technique for tendon repair. Hand. 1973;5(3): 253–255. 12. Takai S, Woo SL, Horibe S, et al. The effects of frequency and duration of controlled passive mobilization on tendon healing. J Orthop Res. 1991;9(5):705–713. 13. Young RE, Harmon JM. Repair of tendon injuries of the hand. Ann Surg. 1960;151:562–566. 14. Duran RE. Controlled passive motion following flexor tendon repair in zone 2 and 3. In: AAOS, Symposium on Tendon Surgery in the Hand. St. Louis, MO: CV Mosby Co, 1975:105–114. 15. May EJ, Sollerman CJ. Controlled mobilization after tendon repair in zone 2: a prospective comparison of three methods. J Hand Surg Am. 1992;17(5):942–952. 16. Gelberman RH, Vande Berg JS, et al. Flexor tendon healing and restoration of the gliding surface. An ultrastructural study in dogs. J Bone Joint Surg Am. 1983;65(1):70 – 80. 17. Aoki M, Kubota H, Pruitt DL, et al. Biomechanical and histologic characteristics of canine flexor tendon repair using early postoperative mobilization. J Hand Surg Am. 1997;22(1):107–114. 18. Becker H. Primary repair of flexor tendon in the hand without immobilization—preliminary report. Hand. 1978;10(1):37– 47. 19. Cullen KW, Tolhurst P, Lang D, et al. Flexor tendon repair in zone 2 followed by controlled active mobilisation. J Hand Surg Br. 1989;14(4):392–395. 20. Khan MI. Early active mobilisation following flexor tendon repair in zone 2. J Hand Surg Br. 1990;15(2):274. 21. Silfverskiöld KL, May EJ, Tornvall AH. Flexor digitorum profundus tendon excursions during controlled motion after flexor tendon repair in zone II: a prospective clinical study. J Hand Surg Am. 1992;17(1): 122–131. 22. Bainbridge LC, Robertson C, Gillies D, et al. A comparison of post-operative mobilization of flexor tendon repairs with “passive flexion-active extension” and “controlled active motion” techniques. J Hand Surg Br. 1994;19(4):517–521. 23. Peck FH, Bucher CA, Watson JS, et al. A comparative study of two methods of controlled mobilization of flexor tendon repairs in zone 2. J Hand Surg Br. 1998;23(1):41– 45. 24. Trumble TE, Vedder NB, Seiler JG III, et al. Zone-II flexor tendon repair: a randomized prospective trial of active place-and-hold therapy compared with passive motion therapy. J Bone Joint Surg Am. 2010;92(6):1381–1389. 25. Lehfeldt M, Ray E, Sherman R. MOC-PS(SM) CME article: treatment of flexor tendon laceration. Plast Reconstr Surg. 2008;121(4):1–12.
JHS 䉬 Vol A, April
An Experimental Study Comparing Active Mobilization to Passive Flexion–Active Extension–Active Flexion After Flexor Tendon Repair in Zone 2 Hongliang Lee, MD, Zhidian Hou, MD, PhD, Peng Liu, MD, Yang Lee, MD, Zihai Ding, MD, Xuefeng Zheng, MD
Purpose Both passive flexion–active extension and active rehabilitation have shown advantages and disadvantages in tendon healing. The purpose of this study was to measure the effect of a combination of these 2 rehabilitation protocols. Methods A tendon injury model was used in white Leghorn chickens. Thirty-two animals were randomly assigned into 4 groups. We compared an unrestricted active flexion rehabilitation (UA) group with 3 groups starting passive flexion, active extension, and active flexion (PAA) at 5, 9.5 and 14 days after repair. The tensile properties and range of motion of the 3 interphalangeal joints were evaluated for 3 postoperative weeks. Results In terms of tensile properties of the operated foot, PAA-14 was higher than any other group, and PAA-5 was the lowest. There was no significant difference between the PAA-9.5 and UA. For the range of motion, there were significant differences between all 4 groups: UA increased the most, PAA-14 increased the least, and PAA-5 increased more than PAA-9.5. For the rupture rate, UA and PAA-5 were higher than were PAA-9.5 and PAA-14. Conclusions The results indicate that the PAA-9.5 and UA may give the best balance (tensile properties, range of motion, rupture rates) of these rehabilitation protocols. PPA-9.5 and UA had similar moderate tensile properties. When considering an increased range of motion, the UA method may be the most appropriate despite its higher rupture rate. When considering a lower rupture rate, PAA-9.5 may be the most suitable. (J Hand Surg 2013;38A:672–676. Copyright © 2013 by the American Society for Surgery of the Hand. All rights reserved.) Type of study/level of evidence Therapeutic III. Key words Biomechanical properties, early mobilization, flexor tendon repair, range of motion, zone 2. HE FULL RECOVERY of digit function remains a difficult clinical problem following zone 2 flexor tendon injuries. Kleinert et al1 developed a passive flexion–active extension regimen, and several authors2– 6 have indicated that protected passive mobi-
T
From the Anatomical Institute of Minimally Invasive Surgery, Southern Medical University, Guangzhou, China. Received for publication August 3, 2012; accepted in revised form January 4, 2013. The authors give special thanks to Zihai Ding for his care and support and to Weidong Zhao for help with the biomechanics. No benefits in any form have been received or will be received related directly or indirectly to the subject of this article.
672 䉬 © ASSH 䉬 Published by Elsevier, Inc. All rights reserved.
lization can inhibit adhesion formation and improve tendon excursion. Silfverskiöld et al7 suggested that a passive flexion-active extension program had more joint motion and tendon excursion than did a passive regimen clinically. Even so, it still does not produce a Corresponding author: Zihai Ding, MD, Anatomical Institute of Minimally Invasive Surgery, Southern Medical University, No. 1838 Guangzhou Avenue North, Guangzhou, Guangdong 510515 China; e-mail: [email protected]. 0363-5023/13/38A04-0006$36.00/0 http://dx.doi.org/10.1016/j.jhsa.2013.01.020
REHABILITATION FOR REPAIRED TENDON
673
FIGURE 1: A, B Weight was attached to the long toe by a thread so that the tip of the operated toe nearly touched the plantar surface of the foot. The extensor muscles could contract and extend the interphalangeal joints. A, C A dorsal splint held the ankle in 60° of plantar flexion and the metatarsophalangeal joint in 30° of flexion and allowed full interphalangeal joint extension.
satisfactory result. Other authors7–9 indicated that an early active mobilization program with more effective tendon gliding and less adhesion formation10 produces more joint motion but results in unacceptably high rupture rates. Both passive flexion-active extension and active rehabilitation have shown advantages and disadvantages. The purpose of this study was to combine these 2 rehabilitation protocols to identify their ideal balance after flexor tendon repairs in zone 2 at 3 weeks of healing. MATERIALS AND METHODS Animal surgeries and postoperative care All experiment protocols were approved by the local animal care and use committee. Both the housing and surgeries were carried out in facilities meeting the standards of local and national regulatory bodies. Thirtytwo adult white Leghorn chickens (Dahuanong Animal Health Products Co., Ltd., Guangdong, China) weighing 1.3–1.5 kg were anaesthetized by xylazine (5–10 mg/kg, injected intramuscularly), and lidocaine hydrochloride (0.5%, 1 mL) was injected into the third toe of
the left foot. Under aseptic conditions, zigzag incisions were made on the plantar surface of the left third digits over zone 2. The flexor sheath was opened longitudinally between the proximal and distal pulleys. The flexor digitorum profundus tendon was isolated, and a transverse complete laceration was made to both the superficial and deep tendons with a scalpel blade. Under an operating microscope at 10⫻ magnification, only the flexor digitorum profundus tendon was repaired with the modified Kessler11 technique with a 5-0 suture. The sheath was completely repaired using a 7-0 suture, and then the skin was closed. The third digit was then placed in a dorsal low-temperature thermoplastic splint with the ankle plantar flexed at 60°, the metatarsophalangeal joints flexed to 30°, and the interphalangeal joints extended fully (Fig. 1). The unoperated control foot was left free to allow for ambulation. The 32 chickens were randomly assigned into 4 equally sized groups with different rehabilitation regimens. All of the operated digits were immediately immobilized in the splint for 3 days. Twenty- to 60-gram weights attached to the long toe were added gradually until the tip of the operated toe
JHS 䉬 Vol A, April
674
REHABILITATION FOR REPAIRED TENDON
nearly touched the plantar surface of the foot. The extensors were elongated and contraction was not restricted so that the animal could actively extend the digit. The passive flexion, active extension, active flexion (PAA) rehabilitation protocols thus realized passive flexion–active extension first, followed by active mobilization) (Fig. 1). The PAA groups were treated with a passive flexion–active extension regimen at a frequency of 12 cycles/min for 5 min/day, and the splints were removed at 5 days, 9.5 days, or 14 days after surgery, allowing unrestricted active motion. The frequency was instituted by Takai,12 who suggested that higher-frequency, controlled passive motion had a beneficial effect. The unrestricted active motion group (UA) had the splint removed after 3 days and were treated with an unrestricted active mobilization program. At the end of 3 weeks of healing, the animals were injected intramuscularly with a lethal dose of xylazine (20 mg/kg). Both the operated and control feet were harvested and tested biomechanically. Six chickens were not enrolled because of ruptured tendons. Biomechanical evaluation Range of motion: The active range of motion of the 3 interphalangeal joints generated by pulling the tendon with the mechanical testing machine was measured with a goniometer. The flexor digitorum profundus tendon of the third digit was cut free, and the first digit was severed. The remaining 3 digits were then mounted on a board by driving 2 nails into the second and fourth digits. The proximal end of the flexor digitorum profundus tendon of the third digit was held by a clamp from the material testing machine. Fifty grams of weight were attached to the tip of the third digit for full extension. The unoperated specimen was loaded at a constant speed of 0.4 mm/s until the tip of the operated toe nearly touched the plantar surface of the foot; the value (X) of the load was then recorded immediately, as was the range of motion of the 3 interphalangeal joints. The operated specimen was then loaded at a constant speed of 0.4 mm/s until the load increased to X, at which point the range of motion was recorded. Tensile properties: The tendon specimens were carefully dissected from the digits, leaving the tendon and sheath attached to the distal phalanx without disturbing the scar tissue around the sheath. Tensile testing was conducted with a material testing apparatus (Bose Corporation, Eden Prairie, MN). The bone–tendon complex was placed in the tendon clamps, and the proximal tendon was covered with dry gauze to reduce slippage.
TABLE 1. Range of Motion of 3 Interphalangeal Joints for 4 Groups (Operated/Control, %) Joints
PAA-14
PAA-9.5
PAA-5
UA
First IPJ
23 ⫾ 2
45 ⫾ 4
60 ⫾ 3
72 ⫾ 3
Second IPJ
22 ⫾ 3
44 ⫾ 4
61 ⫾ 3
72 ⫾ 3
Third IPJ
27 ⫾ 2
45 ⫾ 4
58 ⫾ 3
69 ⫾ 5
IPJ, interphalangeal joint.
The room temperature was maintained at 25°C, and the specimens were kept moist with a saline solution. The clamp-to-clamp distance was measured as the initial length (D0). The specimen was loaded until failure at a constant speed of 0.4 mm/s, and the load-elongation curve was recorded. To reduce the error produced by different initial tendon lengths, the elongation was normalized by D0, and the result was expressed as the percent elongation. To minimize specimen variability, the operative specimens were normalized using the controls. Tensile properties such as the peak force, stiffness, and energy absorption were recorded using the load-percent elongation curve. Statistical data analysis Statistical analysis was performed using a one-way analysis of variance, with the significance set at P ⱕ .05. RESULTS Rupture rates Rupture of the repaired tendon was observed in 6 chickens during the 3-week healing process—2 in both PPA-5 and UA, and 1 each in both PAA-9.5 and PAA-14. All ruptures occurred at the repair site. Range of motion The values were normalized by calculating operated value divided by control value. All 4 groups had significant between-group differences (P ⬍ .05, summarized in Table 1). Tensile properties Tensile properties of the operated digits were much lower than those of the controls (P ⬍ .001). The stiffness, measured between 15% and 30% of the total elongation; peak force; and energy absorption for both the operated and control tendons are summarized in Table 2. The values were normalized by dividing the operated value by the control value (Table 3).
JHS 䉬 Vol A, April
675
REHABILITATION FOR REPAIRED TENDON
TABLE 2.
The Tensile Properties of Tendon 共x⫾s兲 Peak Force (N)
Groups
No. of Tendons
Control
Operated
Stiffness (N/mm/mm) Control
Energy Absorption (N/mm/mm)
Operated
Control
Operated
PPA-14
7
107 ⫾ 16
37 ⫾ 9
696 ⫾ 224
342 ⫾ 116
13 ⫾ 4
3⫾1
PPA-9.5
7
100 ⫾ 20
14 ⫾ 6
671 ⫾ 164
187 ⫾ 99
9⫾5
0.5 ⫾ 0.4
PPA-5
6
113 ⫾ 21
3⫾1
561 ⫾ 144
60 ⫾ 22
15 ⫾ 7
0.10 ⫾ 0.3
UA
6
102 ⫾ 26
14 ⫾ 7
512 ⫾ 85
113 ⫾ 84
13 ⫾ 6
0.8 ⫾ 0.4
TABLE 3. The Normalized Tensile Properties of Tendon 共x⫾s兲 Groups
No. Tendons
Peak Force (%)
Stiffness (%)
Energy Absorption (%)
PPA-14
7
35 ⫾ 8
49 ⫾ 6
22 ⫾ 4
PPA-9.5
7
14 ⫾ 6
28 ⫾ 12
6⫾3
PPA-5
6
3⫾1
11 ⫾ 4
0.8 ⫾ 0.4
UA
6
14 ⫾ 6
22 ⫾ 15
7⫾3
There were no significant effects on the peak forces or the energy absorptions between PAA-9.5 and UA; therefore, no statistically significant differences were demonstrated between PAA-9.5 and UA for these measures or between PAA-5 and UA in terms of stiffness. Compared to the active flexion program, PAA-14 had higher tensile properties (P ⱕ .005), whereas PAA-5 showed the greatest decrease in it (P ⱕ .005). DISCUSSION The restoration of finger function after flexor tendon injury in zone 2 is particularly difficult, especially for sufficient tendon gliding and full joint motion. Tendon mobilization is frequently used in rehabilitation protocols, and several researchers4,13–15 have advocated that good results are observed in the early mobilization groups, whereas gap formation and tendon rupture emerge in the early active motion groups. There is also some evidence16,17 confirming that early mobilization can improve biological properties. Kleinert et al1 promoted a passive flexion-active extension regimen using a dorsal splint with rubber band traction that was modified to gain increased tendon excursion by improving the range of motion of the proximal and distal interphalangeal joints. Both the completely passive regimen and the passive flexionactive extension protocol are far from optimal. Becker18 suggested that dynamic splinting with passive flexion-
active extension was not able to produce sufficient movement of the repair site. With the appearance of several basic research stud17 ies and clinical evidence8,19,20 supporting active flexion, the importance of early active mobilization has increasingly been recognized. Although several authors have suggested that the early active motion of the flexor tendons has some advantages (less adhesion formation and less flexion deformity) over other regimens of passive flexion, high rupture rates7,16,21–23 of the repaired tendons remain an issue of concern. The fear of early tendon rupture following flexor tendon repair is the main reason that these regimens are not widely accepted by hand surgeons. Some authors24,25 recommended that tendon properties decrease from the 5th day to the 14th day after flexor tendon repair. High rupture rates have been observed during this particular period. We hypothesized that better results may emerge by combining the advantages of the active flexion program (sufficient tendon excursion) and of the passive flexion–active extension motion protocol (lower tendon rupture rates). In our study, we observed that PAA-14 had the highest tensile properties (peak force, stiffness, and energy absorption) and that PAA-5 had the lowest. The active motion protocol (UA) increased the range of motion more than any other group, and PAA-14 increased it the least, whereas PAA-5 increased it more than PAA-9.5. Both the UA and PAA-5 groups had 2 tendon ruptures, and PAA-9.5 and PAA-14 each had 1. Compared to the other groups, the PAA-14 can take a greater load, show a higher stiffness, possess a greater capacity of energy absorption, and maintain a lower rupture rate, but the range of motion is inferior to that of the other 3 groups. The PAA-5 protocol is inferior to the other 3 groups in terms of tensile properties, but it ranks second for increased joint motion. The PAA-9.5 and UA protocols were not significantly different in their tensile properties, but the latter had a better range
JHS 䉬 Vol A, April
676
REHABILITATION FOR REPAIRED TENDON
of joint motion. These results may indicate that the PAA-9.5 and UA groups provide the ideal balance of the combined protocols. These protocols leave surgeons with 2 choices: (1) adopting an active flexion motion regimen, in which doctors must endure a high risk of rupture with the benefit of good joint motion with moderate tensile properties, or (2) adopting a less aggressive motion regimen, such as PAA-9.5, in which there is a low rupture rate and moderate tensile properties but less improvement in joint motion than with UA. Considering that we evaluated motion and tensile strength at just 3 time points between the 5th and 14th day after surgery, it is difficult to say which is the best choice for the postoperative protocol: active flexion or PAA-X. In our study, there were only 8 chickens in each group; the sample size was sufficient to compare the tensile properties, but it was not sufficient to compare the tendon rupture rates among the 4 groups. This is a short-term study, and longer follow-up may produce different results. Because of the limitations of our study, subsequent work is required to determine the ideal regimen for flexor tendon rehabilitation. REFERENCES 1. Kleinert HE, Kurtz JE, Atasoy E, et al. Primary repair of lacerated flexor tendons. Orthop Clin North Am. 1973;4(4):865– 876. 2. Gelberman RH, Amifl D, Gonsalves M, et al. The influence of protected passive mobilization on the healing of flexor tendons: a biochemical and microangiographic study. Hand. 1981;13(6):120 – 128. 3. Gelberman RH, Woo SL, Lothringer K, et al. Effects of early intermittent passive mobilization on healing canine flexor tendons. J Hand Surg Am. 1982;7(2):170 –175. 4. Lister GD, Kleinert HE, Kutz JE, et al. Primary flexor tendon repair followed by immediate controlled mobilization. J Hand Surg Am. 1977;2(6):441– 451. 5. Woo SL, Gelberman RH, Cobb NG, et al. The importance of controlled passive mobilization on flexor tendon healing. A biomechanical study. Acta Orthop Scand. 1981;52(6):615– 622. 6. Gault DT. A review of repaired flexor tendons. J Hand Surg Br. 1987;12(3):321–325. 7. Silfverskiöld KL, May EJ. Flexor tendon repair in zone II with a new suture technique and an early mobilization program combining passive and active flexion. J Hand Surg Am. 1994;19(1):53– 60.
8. Becker H, Orak F, Duponselle E. Early active motion following a beveled technique of flexor tendon repair: report on fifty cases. J Hand Surg Am. 1979;4(5):454 –460. 9. Small JO, Brennen MD, Colville J. Early active mobilization following flexor tendon repair in zone two. J Hand Surg Br. 1989; 14(4):383–391. 10. Gelberman RH, Vandeberg JS, Manske PR, et al. The early stages of flexor tendon healing: a morphologic study of the first fourteen days. J Hand Surg Am. 1985;10(6):776 –784. 11. Kessler. The grasping technique for tendon repair. Hand. 1973;5(3): 253–255. 12. Takai S, Woo SL, Horibe S, et al. The effects of frequency and duration of controlled passive mobilization on tendon healing. J Orthop Res. 1991;9(5):705–713. 13. Young RE, Harmon JM. Repair of tendon injuries of the hand. Ann Surg. 1960;151:562–566. 14. Duran RE. Controlled passive motion following flexor tendon repair in zone 2 and 3. In: AAOS, Symposium on Tendon Surgery in the Hand. St. Louis, MO: CV Mosby Co, 1975:105–114. 15. May EJ, Sollerman CJ. Controlled mobilization after tendon repair in zone 2: a prospective comparison of three methods. J Hand Surg Am. 1992;17(5):942–952. 16. Gelberman RH, Vande Berg JS, et al. Flexor tendon healing and restoration of the gliding surface. An ultrastructural study in dogs. J Bone Joint Surg Am. 1983;65(1):70 – 80. 17. Aoki M, Kubota H, Pruitt DL, et al. Biomechanical and histologic characteristics of canine flexor tendon repair using early postoperative mobilization. J Hand Surg Am. 1997;22(1):107–114. 18. Becker H. Primary repair of flexor tendon in the hand without immobilization—preliminary report. Hand. 1978;10(1):37– 47. 19. Cullen KW, Tolhurst P, Lang D, et al. Flexor tendon repair in zone 2 followed by controlled active mobilisation. J Hand Surg Br. 1989;14(4):392–395. 20. Khan MI. Early active mobilisation following flexor tendon repair in zone 2. J Hand Surg Br. 1990;15(2):274. 21. Silfverskiöld KL, May EJ, Tornvall AH. Flexor digitorum profundus tendon excursions during controlled motion after flexor tendon repair in zone II: a prospective clinical study. J Hand Surg Am. 1992;17(1): 122–131. 22. Bainbridge LC, Robertson C, Gillies D, et al. A comparison of post-operative mobilization of flexor tendon repairs with “passive flexion-active extension” and “controlled active motion” techniques. J Hand Surg Br. 1994;19(4):517–521. 23. Peck FH, Bucher CA, Watson JS, et al. A comparative study of two methods of controlled mobilization of flexor tendon repairs in zone 2. J Hand Surg Br. 1998;23(1):41– 45. 24. Trumble TE, Vedder NB, Seiler JG III, et al. Zone-II flexor tendon repair: a randomized prospective trial of active place-and-hold therapy compared with passive motion therapy. J Bone Joint Surg Am. 2010;92(6):1381–1389. 25. Lehfeldt M, Ray E, Sherman R. MOC-PS(SM) CME article: treatment of flexor tendon laceration. Plast Reconstr Surg. 2008;121(4):1–12.
JHS 䉬 Vol A, April