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ADHESION FORMATION AFTER NERVE REPAIR: AN EXPERIMENTAL STUDY OF EARLY PROTECTED MOBILIZATION IN THE RABBIT
ADHESION FORMATION AFTER NERVE REPAIR: AN EXPERIMENTAL STUDY OF EARLY PROTECTED MOBILIZATION IN THE RABBIT W. Y. IP, T. SHIBATA, F. H. TANG, A. F. T. MAK and S. P. CHOW From the Department of Orthopaedic Surgery, The University of Hong Kong, Hong Kong, the Department of Orthopaedic Surgery, Osaka University Medical School, Osaka, Japan and the Rehabilitation Engineering Centre, The Hong Kong Polytechnic University, Hong Kong
The common peroneal nerve and its surrounding muscles were cut and repaired in 14 rabbits. The injured limb was then either immobilized for 3 weeks or passively mobilized within a ‘‘safety range’’ every day. At 3 weeks after operation, the ‘‘stretch test’’ and ‘‘peel test’’ showed no difference in the biomechanical features of the adhesions between the nerve repair and the surrounding soft tissues. Journal of Hand Surgery (British and European Volume, 2000) 25B: 6: 582–584 motion ten times. The wedge was then replaced to immobilize the knee joint in 908 flexion. After three weeks, the rabbits were killed and adhesion formation around the nerve repair was assessed with the ‘‘stretch test’’ and the ‘‘peel test’’.
INTRODUCTION Early protected mobilization after flexor tendon repair improves the clinical result (Chow et al., 1988, 1990; Lister et al., 1997; Verdan, 1972) as it enhances gliding of the tendons and reduces or modifies adhesion formation (Hagberg et al., 1991; Woo et al., 1981). Peripheral nerves also glide over surrounding structures during motion (Apfelberg and Larson, 1972; Wilgis and Murphy, 1986) and, if they become tethered, can cause pain. Early protected movement after nerve repair may therefore be advantageous.
The ‘‘Stretch Test’’ The common peroneal nerve proximal and distal to the operation site was exposed, making sure that no adhesions were disturbed. Two simple marking sutures were placed in the distal and proximal segments (Fig 3) and the distances between the two sutures of each segment were measured. The knee was then extended from 1358 to 608 flexion and these distances were then remeasured. The percentage elongation of both nerve segments on extension was then calculated.
MATERIALS AND METHODS Adult albino rabbits (2.5–3 kg) were used in the experiment. Under general anesthesia, a 2 cm transverse incision was made on the lateral aspect of the right upper calf, just distal to the fibula head. After division of the superficial muscle (biceps femoris) in the line of the skin incision, the common peroneal and posterior tibial nerves were identified. The common peroneal nerve was cut 2 cm proximal to the site where it passed through the deep fascia of the calf. The superficial portion of the gastrocnemius muscle under the nerve was also cut, but immediately repaired with 3–0 nylon mattress sutures. The cut common peroneal nerve was repaired with four 10–0 nylon stitches (Fig 1), and the superficial muscle was repaired with 3–0 nylon mattress sutures. The skin was then sutured. After operation, each rabbit was housed separately and analgesic plus antibiotic was given for five days. Fourteen rabbits were operated on and were divided into two groups of seven. In group A (immobilized group) a hip spica was applied with the hip and knee joints at 908 flexion at the end of the operation. In group B (mobilized group) a hip spica was applied with the hip joint at 908 flexion and the knee at 608 flexion. A removable wedge was then inserted below the knee and strapped to the hip spica so that the knee joint was immobilized in 908 flexion (Fig 2). This wedge was removed once every day and the knee joint was passively moved through a ‘‘safety range’’ (608–1358 flexion) of
The ‘‘Peel Test’’ This assessed the strength of the adhesions between the repaired nerve and the surrounding soft tissues. A segment of the common peroneal nerve centred on the repair site was removed en bloc with the surrounding superficial and deep muscles. The superficial muscles were then carefully removed without disturbing the adhesion scar. The underlying muscle was held on a vertical PVC panel by plexiglass plates on either side of the area where the nerve was adherent to it. The PVCplexiglass holding jig was carefully positioned on the testing platform of an Instron material testing system so that the nerve and its site of adherence were collinear with the loading axis. The distal end of the nerve was held by a self-tightening clamp to the cross-head of the Instron machine (Fig 4). The subsequent cross-head movement (10 mm/min) then gradually peeled the nerve away from the adhesion site. The maximum peeling force and the energy represented by the area under the force-displacement curve were compared between the immobilized and the mobilized groups. 582
ADHESION FORMATION AT NERVE REPAIR
Fig 1 The gastrocnemius muscle and the common peroneal nerve have been repaired.
583
Fig 3 Sutures secured to the distal and proximal segments of the common peroneal nerve. The superficial muscles overlying the nerve repair have been retained.
Fig 4 Set-up of the ‘‘Peel test’’.
Gliding of the common peroneal nerve
Fig 2 (A) Hip spica with a knee wedge to immobilize the knee joint at 908 of flexion. Hip spica with removable flexor component and wedge shown in (B) which held the knee in 908 flexion. After removal of the wedge and replacement of the removable flexor component of the spica, the knee could be passively moved between 608 and 908 flexion.
To find out the extent of gliding occurring between the normal common peroneal nerve and its surrounding muscles within the ‘‘safety range’’ (608–1358 flexion), one additional rabbit was operated on and four stainless steel wire sutures were anchored to the common peroneal nerve at about 1 cm intervals. Four other wire sutures with a different configuration were similarly anchored to the deep and superficial muscles. The skin wound was then closed. Under anaesthesia, the excursion of the nerve and its surrounding muscles were studied by biplane radio-geometric methods with the knee joint flexed at 608, then 908 and finally 1358. The three dimensional locations of the markers were then calculated, allowing the relative movement between the nerve and the adjacent muscles to be determined.
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THE JOURNAL OF HAND SURGERY VOL. 25B No. 6 DECEMBER 2000
Table 1—Mean (SD) percentage changes in length of nerves in the Stretch Test Proximal segment % difference – mean (SD)
Distal segment % difference
3.4 (+1.3) 2.6 (+2.3)
6.4 (+4.6) 10.4 (+8.7)
Immobilized group Mobilized group
RESULTS The study was completed satisfactorily in all 14 rabbits.
Stretch test (Table 1) The proximal segment of the mobilized group elongated slightly more than in the immobilized group, but this difference was not statistically significant (t-test, P 40.05).
Peel test During the peel testing, one nerve in each group peeled horizontally towards the side of the specimen and not vertically towards the proximal end of the nerve: these were both excluded from the analysis. The mean (SD) maximum load during peeling was 2.9 (+0.6) N for the immobilized group and 3.4 (±0.7) N for the mobilized group. This difference was not statistically significant (t test, P 40.05). The energy used peeling the nerve was 29.7 (+7.1) N mm for the immobilized group and 35.8 (+7.3) N mm for the mobilized group. Again, the difference was not statistically significant (t-test, P 40.05).
Gliding of the common peroneal nerve When the knee joint was extended from 1358 to 908 flexion, the nerve and surrounding muscles stretched about 1 mm. When the knee joint was further extended to 608 flexion, the structures stretched by another 2 mm. When the knee joint was extended from 1358 to 908 flexion, there was about 1 mm of gliding between the nerve and the superficial muscles, but no gliding between nerve and deep muscles. However, from 908 to 608 flexion, there was about 1.5 mm of gliding between the nerve and both the superficial muscle and deep muscles.
DISCUSSION The results of this experiment shows that, within a protected ‘‘safety range’’ of passive mobilization of the knee joint in the rabbit, controlled mobilization produced no advantage over immobilization in reducing adhesion formation after repair of the common peroneal nerve. This may be for several reasons. Firstly, passive movements may merely cause buckling of the nerve and the surrounding muscles, especially in the ‘‘safety range’’ of 608 to 1358 flexion. Extension beyond 608 flexion might have produced more gliding but risked disruption of the repair site: a proper balance between protection and mobilization has to be achieved. Secondly, our marker study suggests that only 2 to 3 mm of differential gliding between the nerve and the surrounding muscles occurred within the ‘‘safety range’’. This is probably not enough to prevent or even modify adhesion formation. The nerve and the surrounding muscle, which were bound together by adhesions, moved in unison and differential movement which might cause disruption of the nerve repair or a traction injury was only observed in the proximal portion. If, however, the nerve is tethered to more solid structures, such as bone or an aponeurosis, the situation may be very different, and adhesions may then predispose to a late traction injury of the repaired nerve. References Apfelberg DB, Larson SJ (1973). Dynamic anatomy of the ulnar nerve at the elbow. Plastic and Reconstructive Surgery, 51: 76–81. Chow JA, Thomes LJ, Dovelle S, Monsivais J, Milnor WH, Jackson JP (1988). Controlled motion rehabilitation after flexor tendon repair and grafting. A multi-centre study. Journal of Bone and Joint Surgery, 70B: 591–595. Chow SP, Stephens MM, Ngai WK, et al (1990). A splint for controlled active motion after flexor tendon repair: design, mechanical testing, and preliminary clinical results. Journal of Hand Surgery, 15A: 645–651. Hagberg L, Wik O, Gerdin B (1991). Determination of biomechanical characteristics of restrictive adhesions and of functional impairment after flexor tendon surgery: a methodological study of rabbits. Journal of Biomechanics, 24: 935–942. Lister GD, Kleinert HE, Kutz JE, Atasoy E (1977). Primary flexor tendon repair followed by immediate controlled mobilization. Journal of Hand Surgery, 2: 441– 451. Verdan CE (1972). Half a century of flexor-tendon surgery: current status and changing philosophies. Journal of Bone and Joint Surgery, 54A: 472–492. Wilgis EFS, Murphy R (1986). The significance of longitudinal excursion in peripheral nerves. Hand Clinics, 2: 761–766. Woo SLY, Gelberman RH, Cobb NG, Amiel D, Lothringer K, Akeson WH (1981). The importance of controlled passive mobilization on flexor tendon healing: a biomechanical study. Acta Orthopaedic Scandinavica; 52: 615–622. Received: 24 February 2000 Accepted after revision: 13 July 2000 Professor S.P. Chow, Department of Orthopaedic Surgery, Queen Mary Hospital, Pokfulam, Hong Kong SAR, PR China # 2000 The British Society for Surgery of the Hand doi: 10.1054/jhsb.2000.0480, available online at http://www.idealibrary.com on
The common peroneal nerve and its surrounding muscles were cut and repaired in 14 rabbits. The injured limb was then either immobilized for 3 weeks or passively mobilized within a ‘‘safety range’’ every day. At 3 weeks after operation, the ‘‘stretch test’’ and ‘‘peel test’’ showed no difference in the biomechanical features of the adhesions between the nerve repair and the surrounding soft tissues. Journal of Hand Surgery (British and European Volume, 2000) 25B: 6: 582–584 motion ten times. The wedge was then replaced to immobilize the knee joint in 908 flexion. After three weeks, the rabbits were killed and adhesion formation around the nerve repair was assessed with the ‘‘stretch test’’ and the ‘‘peel test’’.
INTRODUCTION Early protected mobilization after flexor tendon repair improves the clinical result (Chow et al., 1988, 1990; Lister et al., 1997; Verdan, 1972) as it enhances gliding of the tendons and reduces or modifies adhesion formation (Hagberg et al., 1991; Woo et al., 1981). Peripheral nerves also glide over surrounding structures during motion (Apfelberg and Larson, 1972; Wilgis and Murphy, 1986) and, if they become tethered, can cause pain. Early protected movement after nerve repair may therefore be advantageous.
The ‘‘Stretch Test’’ The common peroneal nerve proximal and distal to the operation site was exposed, making sure that no adhesions were disturbed. Two simple marking sutures were placed in the distal and proximal segments (Fig 3) and the distances between the two sutures of each segment were measured. The knee was then extended from 1358 to 608 flexion and these distances were then remeasured. The percentage elongation of both nerve segments on extension was then calculated.
MATERIALS AND METHODS Adult albino rabbits (2.5–3 kg) were used in the experiment. Under general anesthesia, a 2 cm transverse incision was made on the lateral aspect of the right upper calf, just distal to the fibula head. After division of the superficial muscle (biceps femoris) in the line of the skin incision, the common peroneal and posterior tibial nerves were identified. The common peroneal nerve was cut 2 cm proximal to the site where it passed through the deep fascia of the calf. The superficial portion of the gastrocnemius muscle under the nerve was also cut, but immediately repaired with 3–0 nylon mattress sutures. The cut common peroneal nerve was repaired with four 10–0 nylon stitches (Fig 1), and the superficial muscle was repaired with 3–0 nylon mattress sutures. The skin was then sutured. After operation, each rabbit was housed separately and analgesic plus antibiotic was given for five days. Fourteen rabbits were operated on and were divided into two groups of seven. In group A (immobilized group) a hip spica was applied with the hip and knee joints at 908 flexion at the end of the operation. In group B (mobilized group) a hip spica was applied with the hip joint at 908 flexion and the knee at 608 flexion. A removable wedge was then inserted below the knee and strapped to the hip spica so that the knee joint was immobilized in 908 flexion (Fig 2). This wedge was removed once every day and the knee joint was passively moved through a ‘‘safety range’’ (608–1358 flexion) of
The ‘‘Peel Test’’ This assessed the strength of the adhesions between the repaired nerve and the surrounding soft tissues. A segment of the common peroneal nerve centred on the repair site was removed en bloc with the surrounding superficial and deep muscles. The superficial muscles were then carefully removed without disturbing the adhesion scar. The underlying muscle was held on a vertical PVC panel by plexiglass plates on either side of the area where the nerve was adherent to it. The PVCplexiglass holding jig was carefully positioned on the testing platform of an Instron material testing system so that the nerve and its site of adherence were collinear with the loading axis. The distal end of the nerve was held by a self-tightening clamp to the cross-head of the Instron machine (Fig 4). The subsequent cross-head movement (10 mm/min) then gradually peeled the nerve away from the adhesion site. The maximum peeling force and the energy represented by the area under the force-displacement curve were compared between the immobilized and the mobilized groups. 582
ADHESION FORMATION AT NERVE REPAIR
Fig 1 The gastrocnemius muscle and the common peroneal nerve have been repaired.
583
Fig 3 Sutures secured to the distal and proximal segments of the common peroneal nerve. The superficial muscles overlying the nerve repair have been retained.
Fig 4 Set-up of the ‘‘Peel test’’.
Gliding of the common peroneal nerve
Fig 2 (A) Hip spica with a knee wedge to immobilize the knee joint at 908 of flexion. Hip spica with removable flexor component and wedge shown in (B) which held the knee in 908 flexion. After removal of the wedge and replacement of the removable flexor component of the spica, the knee could be passively moved between 608 and 908 flexion.
To find out the extent of gliding occurring between the normal common peroneal nerve and its surrounding muscles within the ‘‘safety range’’ (608–1358 flexion), one additional rabbit was operated on and four stainless steel wire sutures were anchored to the common peroneal nerve at about 1 cm intervals. Four other wire sutures with a different configuration were similarly anchored to the deep and superficial muscles. The skin wound was then closed. Under anaesthesia, the excursion of the nerve and its surrounding muscles were studied by biplane radio-geometric methods with the knee joint flexed at 608, then 908 and finally 1358. The three dimensional locations of the markers were then calculated, allowing the relative movement between the nerve and the adjacent muscles to be determined.
584
THE JOURNAL OF HAND SURGERY VOL. 25B No. 6 DECEMBER 2000
Table 1—Mean (SD) percentage changes in length of nerves in the Stretch Test Proximal segment % difference – mean (SD)
Distal segment % difference
3.4 (+1.3) 2.6 (+2.3)
6.4 (+4.6) 10.4 (+8.7)
Immobilized group Mobilized group
RESULTS The study was completed satisfactorily in all 14 rabbits.
Stretch test (Table 1) The proximal segment of the mobilized group elongated slightly more than in the immobilized group, but this difference was not statistically significant (t-test, P 40.05).
Peel test During the peel testing, one nerve in each group peeled horizontally towards the side of the specimen and not vertically towards the proximal end of the nerve: these were both excluded from the analysis. The mean (SD) maximum load during peeling was 2.9 (+0.6) N for the immobilized group and 3.4 (±0.7) N for the mobilized group. This difference was not statistically significant (t test, P 40.05). The energy used peeling the nerve was 29.7 (+7.1) N mm for the immobilized group and 35.8 (+7.3) N mm for the mobilized group. Again, the difference was not statistically significant (t-test, P 40.05).
Gliding of the common peroneal nerve When the knee joint was extended from 1358 to 908 flexion, the nerve and surrounding muscles stretched about 1 mm. When the knee joint was further extended to 608 flexion, the structures stretched by another 2 mm. When the knee joint was extended from 1358 to 908 flexion, there was about 1 mm of gliding between the nerve and the superficial muscles, but no gliding between nerve and deep muscles. However, from 908 to 608 flexion, there was about 1.5 mm of gliding between the nerve and both the superficial muscle and deep muscles.
DISCUSSION The results of this experiment shows that, within a protected ‘‘safety range’’ of passive mobilization of the knee joint in the rabbit, controlled mobilization produced no advantage over immobilization in reducing adhesion formation after repair of the common peroneal nerve. This may be for several reasons. Firstly, passive movements may merely cause buckling of the nerve and the surrounding muscles, especially in the ‘‘safety range’’ of 608 to 1358 flexion. Extension beyond 608 flexion might have produced more gliding but risked disruption of the repair site: a proper balance between protection and mobilization has to be achieved. Secondly, our marker study suggests that only 2 to 3 mm of differential gliding between the nerve and the surrounding muscles occurred within the ‘‘safety range’’. This is probably not enough to prevent or even modify adhesion formation. The nerve and the surrounding muscle, which were bound together by adhesions, moved in unison and differential movement which might cause disruption of the nerve repair or a traction injury was only observed in the proximal portion. If, however, the nerve is tethered to more solid structures, such as bone or an aponeurosis, the situation may be very different, and adhesions may then predispose to a late traction injury of the repaired nerve. References Apfelberg DB, Larson SJ (1973). Dynamic anatomy of the ulnar nerve at the elbow. Plastic and Reconstructive Surgery, 51: 76–81. Chow JA, Thomes LJ, Dovelle S, Monsivais J, Milnor WH, Jackson JP (1988). Controlled motion rehabilitation after flexor tendon repair and grafting. A multi-centre study. Journal of Bone and Joint Surgery, 70B: 591–595. Chow SP, Stephens MM, Ngai WK, et al (1990). A splint for controlled active motion after flexor tendon repair: design, mechanical testing, and preliminary clinical results. Journal of Hand Surgery, 15A: 645–651. Hagberg L, Wik O, Gerdin B (1991). Determination of biomechanical characteristics of restrictive adhesions and of functional impairment after flexor tendon surgery: a methodological study of rabbits. Journal of Biomechanics, 24: 935–942. Lister GD, Kleinert HE, Kutz JE, Atasoy E (1977). Primary flexor tendon repair followed by immediate controlled mobilization. Journal of Hand Surgery, 2: 441– 451. Verdan CE (1972). Half a century of flexor-tendon surgery: current status and changing philosophies. Journal of Bone and Joint Surgery, 54A: 472–492. Wilgis EFS, Murphy R (1986). The significance of longitudinal excursion in peripheral nerves. Hand Clinics, 2: 761–766. Woo SLY, Gelberman RH, Cobb NG, Amiel D, Lothringer K, Akeson WH (1981). The importance of controlled passive mobilization on flexor tendon healing: a biomechanical study. Acta Orthopaedic Scandinavica; 52: 615–622. Received: 24 February 2000 Accepted after revision: 13 July 2000 Professor S.P. Chow, Department of Orthopaedic Surgery, Queen Mary Hospital, Pokfulam, Hong Kong SAR, PR China # 2000 The British Society for Surgery of the Hand doi: 10.1054/jhsb.2000.0480, available online at http://www.idealibrary.com on