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Passive and Active Rehabilitation for Partial Lacerations of the Canine Flexor Digitorum Profundus Tendon in Zone II
Passive and Active Rehabilitation for Partial Lacerations of the Canine Flexor Digitorum Profundus Tendon in Zone II Rupinder Grewal, MD, Serena S. Chan Saw, MS, Jaime A. Bastidas, MD, Kenneth J. Fischer, PhD, Dean G. Sotereanos, MD, Pittsburgh, PA The purpose of this study was to compare the effect of unrestricted active versus passive mobilization on the gliding function and structural properties (ultimate load and stiffness) of repaired and nonrepaired canine flexor digitorum profundus tendons following partial laceration at 1 week. Using a radiographic method, normalized tendon gliding of the flexor digitorum profundus tendon adjacent to the metacarpal bone and total joint rotation were shown to be significantly greater in passive than in active tendons. Each group differed from their control group, however, by an average of only 5%. Both rehabilitation (active vs passive) and treatment (repair vs nonrepaired) of the partial tendon laceration significantly affected gap formation. Both active rehabilitation and repair of the laceration significantly increased gap formation compared with passive rehabilitation and nonrepair of the partial laceration. Rehabilitation did not significantly affect the normalized ultimate loads and stiffness in the passive and active groups but the nonrepair groups displayed significantly higher ultimate loads and stiffness than the repair groups. (J Hand Surg 1999;24A:743–750. Copyright © 1999 by the American Society for Surgery of the Hand.) Key words: Passive rehabilitation, active rehabilitation, FDP tendon, partial laceration, canine.
Rehabilitation regimens, in practice and in literature, have not differentiated between complete and partial lacerations of the flexor digitorum profundus (FDP) tendon in zone II of the hand. While there are numerous publications relating to the postoperative From the Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Supported by a Ferguson Orthopaedic Foundation grant and by the University of Pittsburgh Medical Center. Received for publication September 2, 1997; accepted in revised form January 20, 1999. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Dean G. Sotereanos, MD, Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of Pittsburgh, 210 Lothrop St—E1641 BST, PO Box 71199, Pittsburgh, PA 15213. Copyright © 1999 by the American Society for Surgery of the Hand 0363-5023/99/24A04-0006$3.00/0
management of complete tendon lacerations, there is a paucity of data on the postoperative care of partial lacerations. At present, rehabilitation of both complete and partial tendon lacerations usually involves some form of splinting with initially controlled passive mobilization followed by controlled, limited active mobilization after 4 to 6 weeks.1–3 Several animal studies have shown that passive mobilization results in greater tendon strength, better gliding function, and a reduction in the adhesion formation after complete tendon laceration compared with immobilization.4 – 8 Improved results with passive mobilization have been reported in clinical studies as well.3,9 –11 Encouraged by the results of early passive mobilization, many clinicians and researchers have introduced active mobilization at an earlier stage in the rehabilitation program of complete tendon laceration. Animal studies comparing active mobilization The Journal of Hand Surgery 743
744 Grewal et al / Rehabilitation for Partial Lacerations
with immobilization in partially lacerated tendons have reported increased strength in the tendons with mobilization.12–15 In addition, Aoki et al16 showed that in complete lacerations, active mobilization with appropriate suture techniques can provide successful results. A number of clinical studies have reported good results with early controlled active mobilization within the confines of a dorsal extension blocking splint.17–22 In 1977, Wray et al23 reported their series of 17 patients with partial lacerations varying from 25% to 95% that were treated without repair and with early active mobilization. All patients returned to work within 3 months. There were no tendon ruptures in this series. Early passive and active mobilization regimens have been shown to provide better results than immobilization, but these regimens have not been directly compared with each other. However, Hagberg and Selvik24 compared the excursion and joint motion between passive flexion of fingers and passive flexion followed by active hold after repair of complete lacerations. It was shown that the additional active hold improved the tendon excursion and the joint rotation. Thus, there is reason to believe that a partially lacerated tendon would benefit from active as opposed to passive mobilization in the immediate postoperative period. The tensile strength of the canine FDP tendon with a 60% cross-sectional laceration has been reported to be greater than the load sustained by tendons during active motion.25,26 This finding suggests that FDP tendons with lacerations up to 60% could tolerate active mobilization. We therefore hypothesized that partial lacerations of the canine flexor tendons in zone II can be rehabilitated with immediate free active mobilization without the need of a restricting cast or brace. Repairing as opposed to not repairing partially lacerated tendons remains controversial. Some investigators advocate repair of all partial lacerations to avoid complications like triggering, entrapment, and rupture.27,28 Others have shown that repairing the tendon reduces its strength if the laceration is less than 60% of the total area of the tendon.12,17,29,30 Therefore, our objective in this study was to compare active and passive rehabilitation regimens in both repaired and nonrepaired tendons.
Materials and Methods Sixteen adult mongrel dogs weighing up to 20 kg were used as experimental subjects. The protocol
was approved by the animal use and care committees of the institutions where the surgeries were performed. All surgeries and postoperative care were performed humanely with the assistance of veterinarians and animal technicians. The animals were anesthetized and a tourniquet was applied to the right forepaw. The paw was shaved, prepared, and draped. Under aseptic conditions, the flexor tendons of the second and fourth digits were exposed. Both digits are similar in size, shape, and anatomic qualities and behave in a similar way when injured.6,31 The sheath of the flexor tendons was opened between the A2 and A4 pulleys. With the digit held extended, a laceration involving 60% of the cross-sectional area of the tendon was made by dividing the ulnar fiber bundle of the FDP tendon in both digits at the level of the proximal interphalangeal joint. Previous work in our laboratory as well as that of others has shown that the ulnar bundle of the FDP comprises 60% of the total cross-sectional area.30,32 The tendon of one digit was repaired using the modified Kessler technique33 with 5– 0 ethibond suture (Johnson & Johnson, Somerville, NJ); the tendon of the other digit was left unrepaired. Digits were randomly selected for repair such that half the dogs in each rehabilitation group had the second digit repaired and half had the fourth digit repaired. The sheath was not repaired. The tourniquet was then released, hemostasis was obtained, and the skin was closed. Eight dogs were placed in a shoulder spica with the elbow flexed to 90° and the wrist flexed to 45° for passive mobilization. The remaining 8 dogs had a dressing bandage applied to enable immediate active mobilization. Each rehabilitation group had 4 dogs with the second digit repaired and 4 with the fourth digit repaired. Antibiotics were given (cefazolin 1 g), 1 dose before surgery and 3 doses after surgery, in addition to analgesics (torbugesic 0.2– 0.3 mg/kg body weight) in the first 24 hours. On the second postoperative day, the volar portion of the spica and the dressing distal to the wrist were removed and passive mobilization of the digits commenced at a rate of 12 cycles/min for 10 minutes each day. The animals without a spica were allowed to mobilize freely after surgery with adequate analgesia. At the end of 1 week, the animals were injected with a lethal dose of intravenous sodium pentathol (100 mg/kg). The forelimbs were then disarticulated at the elbow joint. The skin and subcutaneous tissues were excised and the digits were disarticulated at the carpometacarpal joints with the flexor and extensor
The Journal of Hand Surgery / Vol. 24A No. 4 July 1999 745
tendons divided at the level of the wrist. The second and fourth digits of the left forepaws were used as the control digits; the control tendons were not lacerated. For kinematic testing we used a modification of the radiographic method described by Horibe et al.34 Two 1-mm metal ball markers were placed at the metaphyseal/diaphyseal flair in each metacarpal, proximal, middle, and distal phalanx. The FDP tendon was marked with 2-mm pieces of 24-gauge surgical steel wire inserted into the tendon substance with a 21-gauge spinal needle. These markers were placed in the tendon close to the heads of the metacarpal, proximal, and middle phalanx with the digit in extension. A Plexiglas jig devised for this test allowed the digit to be mounted with 2 sets of adjustable screws holding the metacarpal such that the lateral aspect of the digit was parallel to the base of the testing device. Clamps attached to the FDP and the extensor tendon allowed load to be applied to the tendons separately. The digit was passively preconditioned through a full range of motion for 10 cycles within 15 seconds. A 100-g load was applied to the extensor tendon and a 25-g load to the FDP tendon to define the initial position of extension. A single lateral radiograph of the digit was taken. The extensor load was then removed and the flexor load was increased by 200 g for a total of 225 g to simulate low level/low load flexion.26,34 Five minutes were allowed for equilibration of the tendon before a second lateral radiograph was taken. This procedure was repeated 3 times for each tendon and the results averaged to produce a single result for each parameter per tendon. The centers of the bone and tendon marker positions were transferred from the radiographs to paper and digitized. With a computer program, the absolute tendon excursions along the metacarpal, proximal, and middle phalanx were calculated. Using the rigid body theory,35 the angular rotations of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints were calculated. The accuracy of this method is within 0.5 mm for excursion and within 2° for joint rotation (personal communication, Chan et al, April 1994). The flexor sheaths were then opened and the tendons were inspected for adhesions and gap formation. The length of the adhesions and gap were measured with a caliper under loupe magnification and documented. The distal interphalangeal joints were then disarticulated; the FDP tendon was left attached to the distal phalanx, creating a bone–tendon complex. The anteroposterior and transverse
widths at the level of the laceration, 2 mm proximal to the laceration, and 2 mm distal to the laceration were measured with a caliper under loupe magnification. The corresponding control tendons were measured at points corresponding to the laceration on the experimental tendon. The bone–tendon complex was then placed in a set of clamps and mounted in an Instron materials testing machine (model 4502; Instron Corporation, Canton, MA) for tensile testing to failure. The clamp for the distal phalanx was designed to securely hold only the bone such that the tensile load was entirely sustained by the tendon and its insertion to bone. The proximal end of the tendon was secured in a clamp with a decreasing sinusoidal pattern. The specimen was clamped at a gauge length of 45 mm and immersed in a 0.9% saline solution bath at 37°C for 15 minutes for temperature equilibrium. After a 0.5-N preload was applied, the specimen was loaded to failure at a rate of 50 mm/min. The load-elongation curve was recorded with a data acquisition program. Ultimate tensile load and stiffness were obtained from the curve. A 2-way ANOVA was used to compare the effects of rehabilitation (active vs passive) and treatment (repair vs nonrepair). Significance was further evaluated with the Fisher’s protected least significant difference post hoc test. The experimental digits were compared with the control digits using Student’s t-test. All statistical significance was set at the p # .05 level.
Results All the animals were mobile on the first postoperative day. The animals in the active group were fully bearing weight on the operated limb by the second postoperative day. There were no wound infections or any signs of triggering. In addition, no ruptures and no adhesions to the surrounding structures were found. In the passive repair group, 71% of the tendons had a gap (range, 0 –1 mm; mean, 0.6 mm); in the passive nonrepair group, 38% of the tendons had a 1-mm gap and no gap was found in the remaining tendons. In the active repair groups, gaps were found in 100% of the tendons (range, 0.5–2.3 mm, one outlier at 4 mm; mean, 1.9 mm). Finally, in the active nonrepair group, a gap was found in 63% of the tendons (range, 0 –2 mm; mean, 0.9 mm). The size of the gap was significantly affected by rehabilitation (active vs passive) and by treatment (repair vs nonrepair). A representative dissected tendon from each group is shown in Figure 1.
746 Grewal et al / Rehabilitation for Partial Lacerations
Figure 1. Dissected representative tendons from each group. (A) Active repair. (B) Active nonrepair. (Figure continues)
The Journal of Hand Surgery / Vol. 24A No. 4 July 1999 747
Figure 1. (Continued) (C) Passive repair. (D) Passive nonrepair.
748 Grewal et al / Rehabilitation for Partial Lacerations
Figure 2. Histogram of normalized excursion (mean 6 SD). *p # .05.
Excursion of the FDP tendons along the metacarpal was normalized and reported as a ratio of experimental to the contralateral control (Fig. 2). The excursion along the metacarpal is representative of the total excursion. The total joint rotation (summation of joint rotation at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints) was also reported as a ratio of the experimental to the corresponding contralateral control (Fig. 3). Normalized excursion and total joint rotation of the passive group were significantly greater than those of the active group. Although active and passive groups differed from each other, neither group was significantly different from the contralateral control tendons. The excursion and total joint rotation of the
Figure 4. Histogram of normalized ultimate load (mean 6 SD). *p # .05.
passive group were 104% and 107% that of contralateral control, respectively, and those of the active group were both 96% of contralateral control. There was no effect of surgical treatment (repair vs nonrepair) on normalized excursion and total joint rotation and no significant interactions were found. The ratio of the ultimate load of the experimental bone–tendon complex to the corresponding control bone–tendon complex for each group is shown in Figure 4. The experimental specimens failed at the laceration site, while the contralateral control specimens failed either at the muscular tendinous junction or the tendon bone interface. Since structural properties (ie, ultimate load, stiffness) were evaluated rather than material properties, comparison of 2 different failure site locations is valid. There was no statistical difference between the active and passive groups with regard to ultimate load or stiffness. However, the nonrepair group had statistically significantly greater ultimate load and stiffness than the repair group within each treatment group. In both ultimate load and stiffness, no significant interaction was found. In addition, the ultimate load and stiffness of the experimental bone–tendon complexes were significantly less than those of the unoperated contralateral control bone–tendon complexes for all groups. The ultimate loads and stiffness of each group without normalization are reported in Table 1.
Discussion Figure 3. Histogram of normalized total joint rotation (mean 6 SD). *p # .05.
Our results indicate that during the first week of healing of a 60% cross-sectional laceration in zone
The Journal of Hand Surgery / Vol. 24A No. 4 July 1999 749
Table 1. Nonnormalized Values for Ultimate Load and Stiffness for All Groups Ultimate load (N) Experimental Control Stiffness (N/mm) Experimental Control
Passive Repair
Active Repair
Passive Nonrepair
Active Nonrepair
137.1 6 35.2 331.1 6 91.3
125.8 6 53.5 344.9 6 55.3
186.5 6 44.2 312.4 6 72.3
196.3 6 51.9 380.4 6 75.3
27.6 6 3.0 42.4 6 8.2
13.2 6 7.2 43.0 6 3.7
27.3 6 4.3 37.6 6 6.0
30.1 6 4.0 41.4 6 6.5
Data are given as mean values 6 SD.
II, unrestricted active mobilization does not have any clinically detrimental effects on the ultimate load and stiffness of the canine FDP tendon compared with traditional passive mobilization. Our study is different from previous work on rehabilitation of FDP tendon lacerations in zone II in that it compares active with passive mobilization. Published work has compared active and passive mobilization with immobilization, but has not directly compared active and passive mobilization. With regard to the incidence of gapping in the tendons, although gaps were found in all groups, the active groups had a higher occurrence. However, it must be noted that no ruptures occurred. In addition, those tendons that were not repaired had a lower incidence of gapping than those that were repaired. Thus, our data indicate that repair of a tendon and/or active rehabilitation increased the tendency for gap formation. However, because no ruptures occurred, we still feel that at 1 week after surgery, canine FDP tendons with lacerations up to 60% can tolerate active mobilization. On comparing the gliding function of the FDP tendon and the total joint rotation of the digit, we found that although both these parameters were statistically better in the passive group, the differences were not clinically significant. In the active group, tendon excursion and total joint rotation values were 96% of the control values, which is a good clinical result. The tendon excursion and total joint rotation in the passive group were greater than their respective controls by an average of 6.5%. This difference between the 2 groups (normalized data) is related to the controls, which are assumed to represent the experimental digits before surgery. If we compare the nonnormalized data from the experimental digits only, there is no significant difference between the tendon gliding and joint rotation for the active and passive groups. Thus, unrestricted active postoperative rehabilitation did not adversely affect these parameters when compared with passive mobilization.
The difference in the normalized ultimate loads of the bone–tendon complexes from the active and passive groups did not reach statistical significance. The difference between the loads of the repaired and nonrepaired bone–tendon complexes within each rehabilitation group, however, was statistically significant, with the nonrepaired group having a higher ultimate load. In addition, the average breaking strength of the bone–tendon complex from each group was higher than the reported force in human FDP tendons during active motion (approximately 117.6 N) and pinch grip.26 Our study was a 1-week survival study, which is the beginning of the period when the healing tendon has been shown to be at its weakest (5–14 days).38 No clinically relevant significant differences were found between active and passive rehabilitation except in gap formation. Because no ruptures occurred with unrestricted activity (which included jumping up against the sides of the cage), we feel that our results are encouraging and justify longer-term studies, which are planned. Similar patterns in the longterm studies could be extrapolated to the clinical situation, obviating the need for casts and braces for the treatment of many partially lacerated FDP tendon injuries in zone II. Active mobilization could reduce patient discomfort and treatment cost. The authors acknowledge Dr Savio L-Y. Woo for his guidance on this project. In addition, they thank Shawn Ward for his veterinary assistance.
References 1. Strickland JW. Flexor tendon injuries. part 5. Flexor tenolysis, rehabilitation and results. Orthop Rev 1987;16:18 – 26. 2. Silfverskio¨ld 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 1994;19A:53– 60. 3. Lister GD, Kleinert HE, Kutz JE, Atasoy E. Primary flexor tendon repair followed by immediate controlled mobilization. J Hand Surg 1977;2:441– 451.
750 Grewal et al / Rehabilitation for Partial Lacerations 4. Feehan LM, Beauchene JG. Early tensile properties of healing chicken flexor tendons: early controlled passive motion versus postoperative immobilization. J Hand Surg 1990;15A:63– 68. 5. Gelberman RH, Menon J, Gonsalves M, Akeson WH. The effects of mobilization on the vascularization of healing flexor tendons in dogs. Clin Orthop 1980;153:283–289. 6. Gelberman RH, Vandeberg JS, Lundborg GN, Akeson WH. Flexor tendon healing and restoration of the gliding surface: an ultrastructural study in dogs. J Bone Joint Surg 1983;65A:70 – 80. 7. Gelberman RH, Woo SL-Y, Lothringer K, Akeson WH, Amiel D. Effects of early intermittent passive mobilization on healing canine flexor tendons. J Hand Surg 1982;7: 170 –175. 8. Hitchcock TF, Light TR, Bunch WH, et al. The effect of immediate constrained digital motion on the strength of flexor tendon repairs in chickens. J Hand Surg 1987;12A: 590 –595. 9. Chow JA, Thomes LJ, Dovelle S, Milnor WH, Seyfer AE, Smith AC. A combined regimen of controlled motion following flexor tendon repair in “no man’s land.” Plast Reconstr Surg 1987;79:447– 453. 10. Silfverskio¨ld KL, May EJ, To¨rnvall AH. Gap formation during controlled motion after flexor tendon repair in zone II: a prospective clinical study. J Hand Surg 1992;17A: 539 –546. 11. Strickland JW, Glogovac SV. Digital function following flexor tendon repair in zone II: a comparison of immobilization and controlled passive motion techniques. J Hand Surg 1980;5:537–543. 12. Bishop AT, Cooney WP III, Wood MB. Treatment of partial flexor tendon lacerations: the effect of tenorrhaphy and early protected mobilization. J Trauma 1986;26:301–312. 13. Chow SP, Yu OD. An experimental study on incompletely cut chicken tendons—a comparison of two methods of management. J Hand Surg 1984;9B:121–125. 14. Wray RC Jr, Ollinger H, Weeks PM. Effects of mobilization on tensile strength of partial tendon lacerations. Surg Forum 1975;26:557–558. 15. Kubota H, Manske PR, Aoki M, Pruitt DL, Larson BJ. Effect of motion and tension on injured flexor tendons in chickens. J Hand Surg 1996;21A:456 – 463. 16. Aoki M, Kubota H, Pruitt DL, Manske PR. Biomechanical and histologic characteristics of canine flexor tendon repair using early postoperative mobilization. J Hand Surg 1997; 22A:107–114. 17. Becker H, Orak F, Duponselle E. Early active motion following a beveled technique of flexor tendon repair: report on fifty cases. J Hand Surg 1979;4:454 – 460. 18. Cullen KW, Tolhurst P, Lang D, Page RE. Flexor tendon repair in zone 2 followed by controlled active mobilisation. J Hand Surg 1989;14B:392–395. 19. Lee H. Double loop locking suture: a technique of tendon repair for early active mobilization. Part II: clinical experience. J Hand Surg 1990;15A:953–958.
20. Pribaz JJ, Morrison WA, Macleod AM. Primary repair of flexor tendons in no-man’s land using the Becker repair. J Hand Surg 1989;14B:400 – 405. 21. Savage R, Risitano G. Flexor tendon repair using a “six strand” method of repair and early active mobilisation. J Hand Surg 1989;14B:396 –399. 22. Small JO, Brennen MD, Colville J. Early active mobilisation following flexor tendon repair in zone 2. J Hand Surg 1989;14B:383–391. 23. Wray RC Jr, Holtmann B, Weeks PM. Clinical treatment of partial tendon lacerations without suturing and with early motion. Plast Reconstr Surg 1977;59:231–234. 24. Hagberg L, Selvik G. Tendon excursion and dehiscence during early controlled mobilization after flexor tendon repair in zone II: an x-ray stereophotogrammetric analysis. J Hand Surg 1991;16A:669 – 680. 25. McCarthy DM, Tramaglini DM, Chan SS, Schmidt CC, Sotereanos DG, Herndon JH. Effect of partial laceration on the structural properties of the canine FDP tendon: an in vitro study. J Hand Surg 1995;20A:795– 800. 26. Schuind F, Garcia-Elias M, Cooney WP III, An K-N. Flexor tendon forces: in vivo measurements. J Hand Surg 1992;17A:291–298. 27. Kleinert HE. Should an incompletely lacerated tendon be sutured? Plast Reconstr Surg 1976;57:236 (commentary). 28. Schlenker JD, Lister GD, Kleinert HE. Three complications of untreated partial tendon laceration of flexor tendon— entrapment, rupture, and triggering. J Hand Surg 1981;6:392–396. 29. Almekinders LC, Banes AJ, Ballenger CA. Effects of repetitive motion on human fibroblasts. Med Sci Sports Exerc 1993;25:603– 607. 30. Boardman ND III, Morifusa S, Chan Saw SS, McCarthy DM, Sotereanos DG, Woo SL-Y. Effects of tenorraphy on the gliding function and tensile properties of partially lacerated canine digital flexor tendons. J Hand Surg 1999; 24A:302–309. 31. Gelberman RH, Vandeberg JS, Manske PR, Akeson WH. The early stages of flexor tendon healing: a morphological study of the first fourteen days. J Hand Surg 1985;10A:776–784. 32. Dobyns RC, Cooney WC, Wood MB. Effect of partial lacerations on canine flexor tendons. Minn Med 1982;65:27–32. 33. Kessler I. The “grasping” technique for tendon repair. Hand 1973;5:253–255. 34. Horibe S, Woo SL-Y, Spiegelman JJ, Marcin JP, Gelberman RH. Excursion of the flexor digitorum profundus tendon: a kinematic study of the human and canine digits. J Orthop Res 1990;8:167–174. 35. Spiegelman JJ, Woo SL-Y. A rigid-body method for finding centers of rotation and angular displacements of planar joint motion. J Biomech 1987;20:715–721. 36. Mason ML, Allen HS. The rate of healing of tendons: an experimental study of tensile strength. Ann Surg 1941;113: 424 – 459.
Rehabilitation regimens, in practice and in literature, have not differentiated between complete and partial lacerations of the flexor digitorum profundus (FDP) tendon in zone II of the hand. While there are numerous publications relating to the postoperative From the Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of Pittsburgh Medical Center, Pittsburgh, PA. Supported by a Ferguson Orthopaedic Foundation grant and by the University of Pittsburgh Medical Center. Received for publication September 2, 1997; accepted in revised form January 20, 1999. No benefits in any form have been received or will be received from a commercial party related directly or indirectly to the subject of this article. Reprint requests: Dean G. Sotereanos, MD, Musculoskeletal Research Center, Department of Orthopaedic Surgery, University of Pittsburgh, 210 Lothrop St—E1641 BST, PO Box 71199, Pittsburgh, PA 15213. Copyright © 1999 by the American Society for Surgery of the Hand 0363-5023/99/24A04-0006$3.00/0
management of complete tendon lacerations, there is a paucity of data on the postoperative care of partial lacerations. At present, rehabilitation of both complete and partial tendon lacerations usually involves some form of splinting with initially controlled passive mobilization followed by controlled, limited active mobilization after 4 to 6 weeks.1–3 Several animal studies have shown that passive mobilization results in greater tendon strength, better gliding function, and a reduction in the adhesion formation after complete tendon laceration compared with immobilization.4 – 8 Improved results with passive mobilization have been reported in clinical studies as well.3,9 –11 Encouraged by the results of early passive mobilization, many clinicians and researchers have introduced active mobilization at an earlier stage in the rehabilitation program of complete tendon laceration. Animal studies comparing active mobilization The Journal of Hand Surgery 743
744 Grewal et al / Rehabilitation for Partial Lacerations
with immobilization in partially lacerated tendons have reported increased strength in the tendons with mobilization.12–15 In addition, Aoki et al16 showed that in complete lacerations, active mobilization with appropriate suture techniques can provide successful results. A number of clinical studies have reported good results with early controlled active mobilization within the confines of a dorsal extension blocking splint.17–22 In 1977, Wray et al23 reported their series of 17 patients with partial lacerations varying from 25% to 95% that were treated without repair and with early active mobilization. All patients returned to work within 3 months. There were no tendon ruptures in this series. Early passive and active mobilization regimens have been shown to provide better results than immobilization, but these regimens have not been directly compared with each other. However, Hagberg and Selvik24 compared the excursion and joint motion between passive flexion of fingers and passive flexion followed by active hold after repair of complete lacerations. It was shown that the additional active hold improved the tendon excursion and the joint rotation. Thus, there is reason to believe that a partially lacerated tendon would benefit from active as opposed to passive mobilization in the immediate postoperative period. The tensile strength of the canine FDP tendon with a 60% cross-sectional laceration has been reported to be greater than the load sustained by tendons during active motion.25,26 This finding suggests that FDP tendons with lacerations up to 60% could tolerate active mobilization. We therefore hypothesized that partial lacerations of the canine flexor tendons in zone II can be rehabilitated with immediate free active mobilization without the need of a restricting cast or brace. Repairing as opposed to not repairing partially lacerated tendons remains controversial. Some investigators advocate repair of all partial lacerations to avoid complications like triggering, entrapment, and rupture.27,28 Others have shown that repairing the tendon reduces its strength if the laceration is less than 60% of the total area of the tendon.12,17,29,30 Therefore, our objective in this study was to compare active and passive rehabilitation regimens in both repaired and nonrepaired tendons.
Materials and Methods Sixteen adult mongrel dogs weighing up to 20 kg were used as experimental subjects. The protocol
was approved by the animal use and care committees of the institutions where the surgeries were performed. All surgeries and postoperative care were performed humanely with the assistance of veterinarians and animal technicians. The animals were anesthetized and a tourniquet was applied to the right forepaw. The paw was shaved, prepared, and draped. Under aseptic conditions, the flexor tendons of the second and fourth digits were exposed. Both digits are similar in size, shape, and anatomic qualities and behave in a similar way when injured.6,31 The sheath of the flexor tendons was opened between the A2 and A4 pulleys. With the digit held extended, a laceration involving 60% of the cross-sectional area of the tendon was made by dividing the ulnar fiber bundle of the FDP tendon in both digits at the level of the proximal interphalangeal joint. Previous work in our laboratory as well as that of others has shown that the ulnar bundle of the FDP comprises 60% of the total cross-sectional area.30,32 The tendon of one digit was repaired using the modified Kessler technique33 with 5– 0 ethibond suture (Johnson & Johnson, Somerville, NJ); the tendon of the other digit was left unrepaired. Digits were randomly selected for repair such that half the dogs in each rehabilitation group had the second digit repaired and half had the fourth digit repaired. The sheath was not repaired. The tourniquet was then released, hemostasis was obtained, and the skin was closed. Eight dogs were placed in a shoulder spica with the elbow flexed to 90° and the wrist flexed to 45° for passive mobilization. The remaining 8 dogs had a dressing bandage applied to enable immediate active mobilization. Each rehabilitation group had 4 dogs with the second digit repaired and 4 with the fourth digit repaired. Antibiotics were given (cefazolin 1 g), 1 dose before surgery and 3 doses after surgery, in addition to analgesics (torbugesic 0.2– 0.3 mg/kg body weight) in the first 24 hours. On the second postoperative day, the volar portion of the spica and the dressing distal to the wrist were removed and passive mobilization of the digits commenced at a rate of 12 cycles/min for 10 minutes each day. The animals without a spica were allowed to mobilize freely after surgery with adequate analgesia. At the end of 1 week, the animals were injected with a lethal dose of intravenous sodium pentathol (100 mg/kg). The forelimbs were then disarticulated at the elbow joint. The skin and subcutaneous tissues were excised and the digits were disarticulated at the carpometacarpal joints with the flexor and extensor
The Journal of Hand Surgery / Vol. 24A No. 4 July 1999 745
tendons divided at the level of the wrist. The second and fourth digits of the left forepaws were used as the control digits; the control tendons were not lacerated. For kinematic testing we used a modification of the radiographic method described by Horibe et al.34 Two 1-mm metal ball markers were placed at the metaphyseal/diaphyseal flair in each metacarpal, proximal, middle, and distal phalanx. The FDP tendon was marked with 2-mm pieces of 24-gauge surgical steel wire inserted into the tendon substance with a 21-gauge spinal needle. These markers were placed in the tendon close to the heads of the metacarpal, proximal, and middle phalanx with the digit in extension. A Plexiglas jig devised for this test allowed the digit to be mounted with 2 sets of adjustable screws holding the metacarpal such that the lateral aspect of the digit was parallel to the base of the testing device. Clamps attached to the FDP and the extensor tendon allowed load to be applied to the tendons separately. The digit was passively preconditioned through a full range of motion for 10 cycles within 15 seconds. A 100-g load was applied to the extensor tendon and a 25-g load to the FDP tendon to define the initial position of extension. A single lateral radiograph of the digit was taken. The extensor load was then removed and the flexor load was increased by 200 g for a total of 225 g to simulate low level/low load flexion.26,34 Five minutes were allowed for equilibration of the tendon before a second lateral radiograph was taken. This procedure was repeated 3 times for each tendon and the results averaged to produce a single result for each parameter per tendon. The centers of the bone and tendon marker positions were transferred from the radiographs to paper and digitized. With a computer program, the absolute tendon excursions along the metacarpal, proximal, and middle phalanx were calculated. Using the rigid body theory,35 the angular rotations of the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints were calculated. The accuracy of this method is within 0.5 mm for excursion and within 2° for joint rotation (personal communication, Chan et al, April 1994). The flexor sheaths were then opened and the tendons were inspected for adhesions and gap formation. The length of the adhesions and gap were measured with a caliper under loupe magnification and documented. The distal interphalangeal joints were then disarticulated; the FDP tendon was left attached to the distal phalanx, creating a bone–tendon complex. The anteroposterior and transverse
widths at the level of the laceration, 2 mm proximal to the laceration, and 2 mm distal to the laceration were measured with a caliper under loupe magnification. The corresponding control tendons were measured at points corresponding to the laceration on the experimental tendon. The bone–tendon complex was then placed in a set of clamps and mounted in an Instron materials testing machine (model 4502; Instron Corporation, Canton, MA) for tensile testing to failure. The clamp for the distal phalanx was designed to securely hold only the bone such that the tensile load was entirely sustained by the tendon and its insertion to bone. The proximal end of the tendon was secured in a clamp with a decreasing sinusoidal pattern. The specimen was clamped at a gauge length of 45 mm and immersed in a 0.9% saline solution bath at 37°C for 15 minutes for temperature equilibrium. After a 0.5-N preload was applied, the specimen was loaded to failure at a rate of 50 mm/min. The load-elongation curve was recorded with a data acquisition program. Ultimate tensile load and stiffness were obtained from the curve. A 2-way ANOVA was used to compare the effects of rehabilitation (active vs passive) and treatment (repair vs nonrepair). Significance was further evaluated with the Fisher’s protected least significant difference post hoc test. The experimental digits were compared with the control digits using Student’s t-test. All statistical significance was set at the p # .05 level.
Results All the animals were mobile on the first postoperative day. The animals in the active group were fully bearing weight on the operated limb by the second postoperative day. There were no wound infections or any signs of triggering. In addition, no ruptures and no adhesions to the surrounding structures were found. In the passive repair group, 71% of the tendons had a gap (range, 0 –1 mm; mean, 0.6 mm); in the passive nonrepair group, 38% of the tendons had a 1-mm gap and no gap was found in the remaining tendons. In the active repair groups, gaps were found in 100% of the tendons (range, 0.5–2.3 mm, one outlier at 4 mm; mean, 1.9 mm). Finally, in the active nonrepair group, a gap was found in 63% of the tendons (range, 0 –2 mm; mean, 0.9 mm). The size of the gap was significantly affected by rehabilitation (active vs passive) and by treatment (repair vs nonrepair). A representative dissected tendon from each group is shown in Figure 1.
746 Grewal et al / Rehabilitation for Partial Lacerations
Figure 1. Dissected representative tendons from each group. (A) Active repair. (B) Active nonrepair. (Figure continues)
The Journal of Hand Surgery / Vol. 24A No. 4 July 1999 747
Figure 1. (Continued) (C) Passive repair. (D) Passive nonrepair.
748 Grewal et al / Rehabilitation for Partial Lacerations
Figure 2. Histogram of normalized excursion (mean 6 SD). *p # .05.
Excursion of the FDP tendons along the metacarpal was normalized and reported as a ratio of experimental to the contralateral control (Fig. 2). The excursion along the metacarpal is representative of the total excursion. The total joint rotation (summation of joint rotation at the metacarpophalangeal, proximal interphalangeal, and distal interphalangeal joints) was also reported as a ratio of the experimental to the corresponding contralateral control (Fig. 3). Normalized excursion and total joint rotation of the passive group were significantly greater than those of the active group. Although active and passive groups differed from each other, neither group was significantly different from the contralateral control tendons. The excursion and total joint rotation of the
Figure 4. Histogram of normalized ultimate load (mean 6 SD). *p # .05.
passive group were 104% and 107% that of contralateral control, respectively, and those of the active group were both 96% of contralateral control. There was no effect of surgical treatment (repair vs nonrepair) on normalized excursion and total joint rotation and no significant interactions were found. The ratio of the ultimate load of the experimental bone–tendon complex to the corresponding control bone–tendon complex for each group is shown in Figure 4. The experimental specimens failed at the laceration site, while the contralateral control specimens failed either at the muscular tendinous junction or the tendon bone interface. Since structural properties (ie, ultimate load, stiffness) were evaluated rather than material properties, comparison of 2 different failure site locations is valid. There was no statistical difference between the active and passive groups with regard to ultimate load or stiffness. However, the nonrepair group had statistically significantly greater ultimate load and stiffness than the repair group within each treatment group. In both ultimate load and stiffness, no significant interaction was found. In addition, the ultimate load and stiffness of the experimental bone–tendon complexes were significantly less than those of the unoperated contralateral control bone–tendon complexes for all groups. The ultimate loads and stiffness of each group without normalization are reported in Table 1.
Discussion Figure 3. Histogram of normalized total joint rotation (mean 6 SD). *p # .05.
Our results indicate that during the first week of healing of a 60% cross-sectional laceration in zone
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Table 1. Nonnormalized Values for Ultimate Load and Stiffness for All Groups Ultimate load (N) Experimental Control Stiffness (N/mm) Experimental Control
Passive Repair
Active Repair
Passive Nonrepair
Active Nonrepair
137.1 6 35.2 331.1 6 91.3
125.8 6 53.5 344.9 6 55.3
186.5 6 44.2 312.4 6 72.3
196.3 6 51.9 380.4 6 75.3
27.6 6 3.0 42.4 6 8.2
13.2 6 7.2 43.0 6 3.7
27.3 6 4.3 37.6 6 6.0
30.1 6 4.0 41.4 6 6.5
Data are given as mean values 6 SD.
II, unrestricted active mobilization does not have any clinically detrimental effects on the ultimate load and stiffness of the canine FDP tendon compared with traditional passive mobilization. Our study is different from previous work on rehabilitation of FDP tendon lacerations in zone II in that it compares active with passive mobilization. Published work has compared active and passive mobilization with immobilization, but has not directly compared active and passive mobilization. With regard to the incidence of gapping in the tendons, although gaps were found in all groups, the active groups had a higher occurrence. However, it must be noted that no ruptures occurred. In addition, those tendons that were not repaired had a lower incidence of gapping than those that were repaired. Thus, our data indicate that repair of a tendon and/or active rehabilitation increased the tendency for gap formation. However, because no ruptures occurred, we still feel that at 1 week after surgery, canine FDP tendons with lacerations up to 60% can tolerate active mobilization. On comparing the gliding function of the FDP tendon and the total joint rotation of the digit, we found that although both these parameters were statistically better in the passive group, the differences were not clinically significant. In the active group, tendon excursion and total joint rotation values were 96% of the control values, which is a good clinical result. The tendon excursion and total joint rotation in the passive group were greater than their respective controls by an average of 6.5%. This difference between the 2 groups (normalized data) is related to the controls, which are assumed to represent the experimental digits before surgery. If we compare the nonnormalized data from the experimental digits only, there is no significant difference between the tendon gliding and joint rotation for the active and passive groups. Thus, unrestricted active postoperative rehabilitation did not adversely affect these parameters when compared with passive mobilization.
The difference in the normalized ultimate loads of the bone–tendon complexes from the active and passive groups did not reach statistical significance. The difference between the loads of the repaired and nonrepaired bone–tendon complexes within each rehabilitation group, however, was statistically significant, with the nonrepaired group having a higher ultimate load. In addition, the average breaking strength of the bone–tendon complex from each group was higher than the reported force in human FDP tendons during active motion (approximately 117.6 N) and pinch grip.26 Our study was a 1-week survival study, which is the beginning of the period when the healing tendon has been shown to be at its weakest (5–14 days).38 No clinically relevant significant differences were found between active and passive rehabilitation except in gap formation. Because no ruptures occurred with unrestricted activity (which included jumping up against the sides of the cage), we feel that our results are encouraging and justify longer-term studies, which are planned. Similar patterns in the longterm studies could be extrapolated to the clinical situation, obviating the need for casts and braces for the treatment of many partially lacerated FDP tendon injuries in zone II. Active mobilization could reduce patient discomfort and treatment cost. The authors acknowledge Dr Savio L-Y. Woo for his guidance on this project. In addition, they thank Shawn Ward for his veterinary assistance.
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