Clinical application of controlled stress to the healing extensor tendon: a review of 112 cases.

The purposes of this article are to describe an early passive motion program for the healing extensor tendon and to report the results and trends noted in a review of 112 complex extensor tendon injuries treated with this therapeutlc technique. 7be rationale for this technique is based on a review of the physiologic response of healing tendon to controlled stress Clinical application is dependent on a biomechanical study of extensor tendon excursion, which allows the therapist to apply controlled stress to the healing tendon with precision. The early passive motion technique is considered in terms of physiology, biomechanics, clinical application, and results The author concludes that early controlled passive motion for the complex extensor tendon injury in zones V, VI, VII, T IV, and T V is a safe and effective rehabilitation technique that reduces complications associated with extensor tendon injury and repair [Evans RB: Clinical application of controlled stress to the healing extensor tendon: A review of 112 cases. Phys T-her 69:1041-1049, 1989] Key Words: Hand injuries; Kinesiology/biomecbanics, upper extremity; Rehabilitation; Tendon injuries. The rationale and technique for an early passive motion program and method of calculating precise excursions necessary for applying controlled stress to the healing extensor tendon have been described previously. The purposes of this article are to review the rationale, biomechanics, and clinical application for this therapeutic technique and to report the results and trends noted in 112 complex extensor tendon injuries treated with early passive motion. Following surgical repair of extensor tendon laceration, the tenorrhaphy site is traditionally protected by immobilizing the wrist and digits in extension.6 Although adhesions may develop locally, they are usually inconsequential with the simple extensor tendon laceration in terms of final functional outcome. However, the complex extensor tendon injury creates difficult rehabilitation problems, often resulting in limited recovery or the need for additional surgical procedures. A complex extensor tendon injury is defined as one in which the periosteum of bone, adjacent soft tissue, or extensor retinaculum are also injured. These untidy extensor injuries can be expected to be associated with a proliferative fibroblastic response that will jeopardize tendon glide. Complete immobilization during the healing phase of extensor tendon injuries with combined lesions in extensor tendon zones V, VI, VII, T IV, and T V frequently results in postoperative complications of adherent tendons, extensor lag, and joint contracture (Fig. 1). A controlled early passive motion protocol for the healing extensor tendon for die previously noted zones was established in 1979 to reduce the postoperative problems associated with the complex injury.1 Precise guidelines for correlating tendon excursion with joint motion for the early passive motion program was defined in 1986 in a study of the biomechanics and excursions of the extensor tendon system. Rationale for Early Passive Motion The ultimate goals of applying controlled stress to the healing tendon are to promote intrinsic healing and to encourage longitudinal reorientation of adhesions associated with extrinsic healing. Research studies focusing on flexor tendons indicate that the controlled stress of early motion has a positive effect on intrinsic healing, synovial diffusion to the tendon, repair site cellularity, tensile strength, peritendinous vessel density and configuration, and tendon excursion. 1-29Presumably, the principles for modification of the tendon repair process by application of controlled stress as used for the flexor tendon can be applied to extensor tendons in certain zones. 1-5 Problems of reestablishing tendon glide after repair are not selective to the flexor system. Rosenthal discusses the inflammatory response of the extensor paratenon when disturbed, especially in the complex extensor tendon injury, and notes that the paratenon has a prodigious capacity for generating scar tissue and adhesions.9 Peacock and van winkle, in a study of the effects of enveloping tendon transfers with paratenon, observed that transplanted paratenon abounds in collagen, synthesizing cells. The observed physiological response of disturbed paratenon is an increased production of adhesions in surrounding tissues. This increase may explain proliferative adhesion formation in the extra synovial extensor tendon injury in zones V and VI, particularly with crushing injury in which the enveloping paratenon is widely disturbed. Problems of reestablishing extensor tendon glide in zone VII following injury and repair are well known to the clinician. In zone VII, the tendons are synovial, passing through six fibro-osseous canals to gain entrance to the hand. The synovial sheaths and dorsal retinaculum mechanically act as pulleys, maintaining the relationship of tendon to bone while allowing for changes of direction, and may be important to tendon nutrition at this level. Rehabilitation problems in extensor zone VII are similar to problems associated with flexor zone 11 injuries. Tendon healing, nutrition, and problems associated with reestablishing tendon excursion following injury appear similar in some aspects for the flexor and extensor systems. 1-5,31,35,36 The initial assumption that the techniques of applying controlled stress to flexor tendon injuries might be reversed and applied to the healing extensor tendon in certain zones and that they are safe and effective is supported by my 10-year clinical experience. Allieu and associates also report good results with an early controlled passive motion program for the extensor tendon system. The final consideration for the early passive motion program is to establish how much passive excursion or glide is necessary to prevent debilitating adhesions at the repair site without significantly increasing gap formation or causing tendon rupture. The initial protocol specified 5 mm of tendon glide based on Duran and Houser's recommendation that 3 to 5 mm of passive tendon glide is sufficient to prevent dense adhesions at a flexor tendon repair site.1 Clinically, 5 mm of excursion has worked well for this extensor protocol. Gelberman and associates recently concluded that 3 to 4 mm of passive excursion created no significant repair site deformation in 11 of 12 canine flexor tendons in a study of repair site elongation when protected early motion was used. In an earlier study, Ketchum et al recommended that the gap formation between the repaired tendon ends must be kept to a minimum, preferably to less than 1 mm, because larger gaps stimulated either adhesion formation or tendon rupture. Seradge noted the direct correlation between elongation at the repair site and development of adhesions requiring tenolysis. Gelberman and associates in a recent study have demonstrated that once small gaps <3 mm) occur between tendon ends, the tendon itself demonstrates considerable intrinsic capability to compensate for the defects.47 These studies are significant to early passive motion programs because they clearly emphasize the precision with which controlled stress to the healing tendon must be applied so that the repair site is stimulated but not elongated. Extensor Tendon Excursion The early passive motion program for the complex extensor tendon injury in zones V, VI, VII, T IV, and T V is dependent on the therapist's understanding of excursion as it relates to joint motion, allowing the therapist to apply controlled stress to the healing extensor tendon with precision. The following calculations on extensor tendon excursion in zones V, VI, VII, T IV, and T V based on literature review, biomechanical studies, and intraoperative measurement provide the clinician with the technical data necessary to provide precisely 5 mm of passive extensor tendon glide in these zones. This work is briefly reviewed because it is critical to the understanding of application of controlled stress to the healing tendon. Literature Review Literature review of reported tendon excursions yields information that is variable but within a consistent range. Differences exist between the individual extensor digitorum communis (EDC) tendons as well as from person to person. Calculations in excursion depend on where die excursion was measured and how it was determined, and certainly would vary with cadaver studies versus in-vivo studies. Bunnell's cadaver studies of excursions provided the most detailed information and correlated closely with those recently described by Brand. Bunnell assigned values for individual finger tendons at each metacarpophalangeal (MP), proximal interphalangeal IP), and distal IP joint with the wrist in a neutral position (Tab. 1). Biomechanical Considerations Considering that variations in tendon excursion exist, the existence of a constant relationship between EDC tendons and MP joint motion was studied. Biomechanically, the excursion of the extensor tendon at the MP joint level is directly proportional to angular changes of the joint. Brand describes the existence of a "constant" extensor tendon moment arm at the MP joint level, which, although not precisely constant, does not change dramatically with joint motion. On the basis of this rather constant relationship, a simple equation is proposed for determining excursion of the extrinsic finger extensors in zones V, VI, and VII in relation to MP joint motion: joint motion, divided by tendon excursion for that particular joint, is equal to the number of degrees of motion required to effect 1 mm of tendon glide.

joint motion (degrees)/

Tendon excursion (millimeters)

Degrees/millimeters 1) Application of this equation is contingent upon assignments of joint motion, tendon excursion, and the amount of excursion necessary to stimulate the repair site and limit adhesions without increasing gap formation. The suggested equation is formulated with these values for MP joint motion: 85 degrees, index finger; 88 degrees, long finger; 90 degrees, ring finger; 92 degrees, little finger. Excursions used are those described by Bunnell because he measured each finger separately (Tab. 1). Five millimeters of glide, as suggested by Duran and Houser and substantiated by the results of my pilot study, was determined to be a safe and effective excursion (Tab. 2).' The efficacy of this equation is confirmed if one examines tendon excursion in relation to radians. A radian is a unit of angular motion that defines joint motion and tendon excursion in relation to the moment arm of the joint in question (Fig. 2). Brand believes that the radian concept is particularly applicable to the MP joint because a constant axis of joint motion and a rather constant tendon moment arm exist throughout the arc of motion.49 Brand has calculated the mean moment arm (that is, the perpendicular distance from the axis of the joint to the tendon) for the index finger MP joint to be 10 mm in cadaver studies.49 If the head of the metacarpal is considered in terms of a circle, the moment arm of the extensor tendon is equal to the radius of the circle. Tendon excursion is equal to the moment arm when the MP joint is rotated 1 radian 57.29 (sup deg.); therefore, angular rotation of 1 radian would produce 10 mm of extensor tendon glide for the index finger if the moment arm were 10 mm (Fig. 3). The early passive motion program requires only 5 mm of excursion; therefore, the MP joint would require movement through 0.5 radian 28.64 (sup deg.) of angular movement to effect this excursion. Note the close correlation to my suggested equation, which calculates that 28.3 degrees of MP joint motion effects 5 mm of extensor tendon excursion in the index finger at this level.3 As joint size varies, one must consider that it is the constant relationship of tendon excursion to angular change and the moment arm distance that is important. For example, if the MP joint of the little finger has a moment arm of 7.5 mm, an angular change of 0.5 radian will produce 3.75 mm of glide. To effect 5 mm of glide for the early passive motion program, it would be necessary to recalculate:

28.64 (sup deg.)/3.75mm= 7.64 (sup deg.) per each mm

glide x 5 mm = 38.2 (sup deg.) (2) The smaller ulnar joints might then have to move through more than 0.5 radian to produce 5 mm of excursion. This greater demand is related to the fact that the ulnar digits have more joint motion but less extensor tendon excursion than the radial joints. Intraoperative Measurements Intraoperative measurements of extensor tendon excursion correlated closely with the suggested equation and radian concept. Burkhalter found by gross measurement that approximately 60 degrees of MP joint angular motion effected 10 mm of extensor tendon glide and that 30 degrees effected 5 mm of glide. Extensor Pollicis Longus Tendon Excursions were studied for the extensor pollicis longus EPL) tendon in zones T [V and T V (Fig. 1). Injuries at this level create difficult rehabilitation problems because dense adhesions frequently limit excursion of the EPL tendon at the retinacular level. The EPL tendon excursions cited in the literature vary from 25 to 60MM. The simple angular arrangement of the flexion-extension axis at the MP joint level of the fingers does not exist for the EPL tendon in zones T IV and T V; therefore, my excursion equation cannot be applied to this tendon. Calculating excursion is complicated by the oblique course that the tendon takes at Lister's tubercle, by the moments of adduction and external rotation at the carpometacarpal joint level, and by the fact that alterations in thumb position alter the moment arms at each joint. Therefore, intraoperative passive excursions determined the joint motion necessary to create 5 mm of EPL tendon excursion in zones T IV and T V for the early passive motion program. Burkhalter found that with the wrist in neutral and the thumb MP joint extended, 60 degrees of IP joint motion effected 5 mm of tendon excursion at Lister's tubercle. The results of this study of the biomechanics and dynamic anatomy of the extensor tendons allow the therapist to apply controlled stress in a precise manner, which presumably because of the excellent clinical results satisfies the physiological balance between the small excursions necessary to stimulate the repair site and the excessive stress that would lead to gap formation or rupture. However, no histological studies have been performed because few of these cases have required tenolysis. Review of the literature, biomechanical findings, and intraoperative measurements indicate that, depending on the involved finger, 28.3 to 40.9 degrees of MP joint flexion will create 5 mm of EDC tendon excursion in zones V, VI, and VII. The EPL tendon will glide 5 mm at Lister's tubercle with the wrist and MP joint at neutral, with 60 degrees of IP joint flexion. Clinical Application Controlled stress is applied to the extrinsic extensor tendons by the third postoperative day in zones V, VI, VII, T IV, and T V by allowing the repaired tendons to glide 5 mm within a forearm-based dynamic extension splint. Stress is relieved at the repair site of the finger extensors by positioning the wrist at approximately 40 degrees of extension. The MP and IP joints rest at 0 degrees in dynamic extension slings (Fig. 4). An interlocking palmar blocking splint will permit only the predetermined angular changes at the MP joint level (Tab. 2). The patient is instructed to actively flex the digits at the MP joint until the fingers touch the volar splint and then to relax the digits, allowing the extensor outrigger to passively return the finger joints to 0 degrees (Fig. 5). The patient is instructed to repeat this exercise 10 to 20 times each waking hour. If the patient has difficulty flexing the fingers at the MP joint level or if the proximal IP joints do not rest at 0 degrees within the extension sling, then digital volar extension splints can be slipped inside each finger cuff to ensure that motion takes place at the MP joint. The patient is seen in therapy for wound care, splint adjustments, and controlled passive motion for the IP joints. Minimal excursion of the EDC joint in zones V, VI, and VII is created by motion at the proximal and distal IP joint level if the wrists and MP joints are held in maximum extension. Anticipated problems of IP joint tightness such as those associated with posttraumatic edema or arthritis should be addressed from the first postoperative week by careful passive motion to each IP joint with the wrist and MP joints held in maximum extension (Fig. 6). I allow 45 degrees of passive proximal IP joint motion for repairs in zone V, 60 degrees of motion for repairs in zone VI, and 90 degrees of proximal IP joint motion for injuries in zone VII based on the results of excursion studies and my personal clinical experience.3 The distal IP joints may be moved through a full ROM with injuries in zones V, VI, or VII. Care must be taken to ensure that the ulnar MP joints cannot rest in hyperextension, compromising the transverse metacarpal arch or creating problems for MP joint collateral ligament extensibility. The patient may be instructed to remove the dorsal outrigger component and to secure the volar component by repositioning the Velcro straps to simplify dressing activities. The digits must rest at the 0degree position at all other times, however, to prevent extensor lag or an elongated callous healing. The patient follows the active flexion passive extension exercise regimen at home within the confines of the dynamic extension splint and volar block. The EPL tendon is splinted with the wrist extended, the carpometacarpal joint in a neutral position, and the MP joint at 0 degrees (Fig. 7). Dynamic traction rests the IP joint at 0 degrees but allows 60 degrees of active flexion to effect the necessary excursion (Fig. 8). This regimen is followed for 21 days, at which time the volar block is removed, and splint protection is provided in the daytime by the dynamic extension component for another two to three weeks. The volar component is worn at night during this same time period. The usual exercise and splinting protocol for extensor tendon rehabilitation is initiated three weeks postrepair." Resting the digital joints at 0 degrees prevents extensor lag. The controlled stress to the tendon is thought to positively influence intrinsic healing, metabolic activity, tensile strength, and excursion. Metacarpophalangeal joint motion during the healing phase diminishes the problems of extension contractures and helps to maintain collateral ligament integrity. The controlled intrinsic flexion promotes a tightening of the dorsal skin, which helps to create venous and lymphatic return, thus reducing edema and improving local nutrition. Results Results of a 10-year study on early passive motion in the complex extensor tendon injury in zones V, VI, VII, T IV, and T V are reviewed for this article. In 1986, results of the pilot study were reported in an article on the biomechanics and dynamic anatomy of the extensor tendons. The average total active ROM for 66 digits in 36 patients treated with early passive motion was 210.41 degrees. No extensor tenolysis was performed. One rupture of an extensor indicis proprius tendon occurred in a patient who removed his splint prematurely. All patients were treated by the same therapist. Establishing precise guidelines for allowable excursion of the healing extensor tendon in 1986 provided the foundation for a new study in which a prospective multicenter comparison of immobilization and early passive motion techniques was proposed. Invited participants in this study were all experienced hand therapists and members of the American Society of Hand Therapists. Patient selection, treatment protocol, and data collection were carefully defined. The purpose of the study was stated as a comparison of immobilization and early passive motion in terms of total active ROM, complications, and required rehabilitation time of both immobilized and mobilized complex extensor tendon injuries. Patients to be included were those with complex extensor tendon injury to the EDC, extensor indicis proprius, or extensor digiti minimi tendon in zones V, VI, and VII or the EPL tendon in zones T IV and T V. A complex extensor tendon injury was defined as extensor injury with combined lesions or osseous injury, multiple soft tissue injury such as a crushing injury, injury with anticipated increased fibroblastic response such as an injury with infection, hematoma, skin problems, and any injury at the retinacular level. Other requirements for inclusion in the experimental group were that the osseous injury be stable, that the tendon have good juncture, and that the patient be cooperative. Surgical or suture technique was not a factor because this study evaluated only rehabilitation technique. The control group required immobilization for 21 days with fingers and wrists extended, followed by the conventional extensor tendon protocol for guarded progressive exercise and splinting. The experimental group required a complex extensor tendon injury and controlled passive motion by the third postoperative day, as defined in the section on clinical application. Information recorded for each patient in both the control and experimental groups included age, sex, mechanism of injury, zone and tendons involved, and complications. Total active ROM for each involved digit was recorded at 4, 6, 8, 10, and 12 weeks postinjury. Results of 76 other cases were studied in addition to the 36 cases reported in 1986. Thirty-two of these cases were excluded from statistical review because they did not qualify as complex extensor tendon injuries or as primary tendon repairs or because the protocol was not precisely followed. These cases included simple extensor laceration in zones V and VI, tendon transfers for radial nerve lesions and rheumatoid rupture, and cases in which early motion was started at five to seven days postinjury. It is of interest, however, that no ruptures were noted in the experimental patients who were excluded, that rehabilitation time was four to six weeks in this group, and that total active ROM averaged 240 degrees per digit. The remaining 44 cases included 84 tendon repairs and were treated by participants in the multicenter study. The results were divided by extensor tendon zone into three groups for more careful analysis of the results and problems: 1) zones V and VI, 2) zone VII, and 3) zones T IV and T V. Results in the first experimental group (zones V and vi) were excellent. Thirty-five tendons in 16 patients treated with early passive motion averaged 237 degrees. One digit resulted in ray resection and was excluded from the data analysis. There were no ruptures, tenolysis, or extensor tag in this group. Rehabilitation time averaged four to six weeks in 86% of the patients in this group. The control group, which was treated with immobilization, consisted of only 6 patients (9 tendon repairs). Their average total active ROM was 185 degrees. Two cases involved extensor lag greater than 30 degrees; two cases required tenolysis. Therapy averaged 10 weeks in this group. Results in the second experimental group (zone VII) are misleading if one considers total active ROM with the wrist in a neutral position. The 8 patients (17 tendon repairs) in this group averaged a total active ROM of 242 degrees. The success of this patient group, however, should also be measured in terms of wrist and digital function combined. As a whole, this group had no problem with simultaneous wrist and finger extension, and only two of the digits had extensor tag of more than 30 degrees. Two patients, however, developed extension contractures of the wrist and were unable to flex the wrist beyond 15 to 20 degrees with the digits in flexion. There were no ruptures in this group. Rehabilitation time averaged six to eight weeks. Two cases required additional therapeutic procedures because of wrist extension contracture. The control group consisted of 3 patients (12 tendon repairs). Their average total active ROM was 188.12 degrees. Two cases required tenolysis, and this group's rehabilitation time averaged 12 weeks. Range of motion of the thumb was measured in terms of carpometacarpal metacarpal, and IP joint motion and die ability to oppose the little finger. The third experimental group (zones T IV and T V) consisted of 8 patients (8 tendon repairs) and had an average total active ROM of 116 degrees, with all patients demonstrating an ability to oppose the little finger with the thumb. This group had an average rehabilitation time of four to six weeks. There were no ruptures, and no patients required additional treatment. The control group consisted of 3 patients (3 tendon repairs) with an average total active ROM of 82 degrees. Two patients were able to oppose to the little finger with the thumb. one patient's thumb required tenolysis. Their average rehabilitation time was six to eight weeks. Summary and Conclusions I have used early passive motion in extensor tendon zones V, VI, VII, T IV, and T V as a safe and effective management technique for the complex extensor tendon injury since 1979. The original hypodiesis as stated in the pilot study, that early passive motion for the complex extensor tendon injury yields improved motion, reduces postoperative complications, and shortens rehabilitation time has been supported by both my 10-year experience with this technique and the results of this recent multicenter study. The application of controlled stress to a healing tendon is dependent on an understanding of tensile strength, the amount of stress necessary to stimulate but not elongate a repair site, and precise transmission of that force.1-5,11-29 The rationale for my clinical application of this early passive motion technique is supported by current research of the physiological response of the healing tendon to controlled stress, by biomechanical studies of the dynamic anatomy of extensor tendons that relates tendon excursion to joint motion, and by clinical results. The purposes of this article were to review the rationale, biomechanics, and clinical application of early passive motion for the complex extensor tendon injury and to report the results of a multicenter study comparing treatment by early mobilization with immobilization during the healing phases. The results and trends noted in the multicenter study have been reviewed and support the original hypothesis.1 These results are not statistically valid, however, because of the large variation in the complexity of the injuries and because the validity of any multicenter study is questionable. Results of the multicenter study indicate that the zone VII injury may require further study. Metacarpophalangeal joint motion alone in the healing phase does not appear to be sufficient for zone VII injuries. Protected excursions involving limited wrist motion may need to be studied as an adjunct to this protocol for injuries that involve the dorsal retinaculum or dorsal capsule. This technique has application for the simple extensor injury, the repaired rheumatoid tendon, and extensor tendon transfer, as evidenced by information collected from the multicenter study and my personal clinical experience (J Agee, personal communication, December 1988). 1 recommend consideration of early passive motion in the specified zones as an alternative treatment to immobilization during the healing phases for the extensor tendon injury. Results of this extended study would indicate that this management technique is safe and physiologically superior to treatment by immobilization. Acknowledgments The following participants in the multicenter study comparing immobilization with early passive motion for the healing of injured extensor tendons are gratefully acknowledged in order of their participation: Ginger Clark, OTR; Susan Emerson, MEd, OTR; Marcia McCalla, RPT; William Love, MD; Susan johnson, OTR; Terri Wilson, OTR; Patricia Chan, OTR; and Chris Smithie, OTR. The help of William E Burkhalter, MD, for technical assistance, shared clinical results, and encouragement is greatly appreciated. The shared clinical results through personal communication of john Agee, MD; Pam Silverman, OTR; Leslie Mervis, OTR; Missy Donnell, OTR; Patty Taylor Mullins, RPT; Nancy Cannon, OTR; and janet Waylett-Rendal, OTR, support the conclusions of this article. Karen Stewart, MS, OTR, is recognized for her work with the evaluation form used in the comparison study.