JBJS | Gliding Resistance of Extrasynovial and Intrasynovial Tendons through the A2 Pulley*

The Journal of Bone & Joint Surgery, Volume 79, Issue 2

Articles | February 01, 1997

Gliding Resistance of Extrasynovial and Intrasynovial Tendons through the A2 Pulley*

SHIGEHARU UCHIYAMA, M.D.†; PETER C. AMADIO, M.D.†; J. HENK COERT, M.D.†; LARRY J. BERGLUND, B.S.†; KAI-NAN AN, PH.D.†, ROCHESTER, MINNESOTA

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Investigation performed at the Orthopedic Biomechanics Laboratory, Mayo Clinic and Mayo Foundation, Rochester

The Journal of Bone & Joint Surgery. 1997; 79:219-24

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Abstract

The gliding ability of the flexor digitorum profundus tendon and of the palmaris longus tendon through the A2 pulley was compared, in terms of gliding resistance, with use of a system that we developed. Fourteen digits and the ipsilateral palmaris longus tendons from fourteen cadavera were used. The average gliding resistance at the interface between the palmaris longus tendon and the A2 pulley was found to be greater than that between the flexor digitorum profundus tendon and the A2 pulley under similar loading conditions. We concluded that the gliding ability of the palmaris longus tendon was inferior to that of the flexor digitorum profundus tendon in vitro.CLINICAL RELEVANCE: The findings of the present study are consistent with those of in vivo experiments in which extrasynovial tendon grafts have been associated with substantial formation of adhesions. The adhesions may be explained by the poor gliding ability of the palmaris longus tendon. The palmaris longus tendon may have limitations, because of gliding resistance, when it is used as a graft to reconstruct flexor tendons in the digits.

Figures in this Article

Introduction

Introduction | Materials and Methods | Results | Discussion | References

When primary repair of the flexor tendon in the finger is not possible, a free tendon graft may be indicated¹². Complications such as adhesions on the tendon and contractures of the joint may occur, and motion is not as good after use of a tendon graft as it is after repair of a tendon^16,17. The palmaris longus tendon, which is extrasynovial, is a common source for a graft because the functional loss at the wrist is slight, it is in the same operative field as the flexor tendon, and it is easily accessible^12,20. Recently, several in vivo studies have shown differences between intrasynovial and extrasynovial tendon grafts with regard to the biological response and the healing process^6,7,14. Extrasynovial tendon grafts were associated with more adhesions to the surrounding tissue than were intrasynovial tendon grafts. On the basis of these findings, we hypothesized that the gliding ability of an extrasynovial tendon was inferior to that of an intrasynovial tendon.

We developed a system that enables direct measurement of the gliding resistance between the tendon and the pulley. Verification and validation of this experimental setup with use of a nylon monofilament cable around a nylon rod, and application of this system to the tendon-pulley unit, have been reported^1,18. In the present study, the gliding resistance between the A2 pulley and the flexor digitorum profundus tendon (an intrasynovial tendon) was compared with that between the A2 pulley and the palmaris longus tendon (an extrasynovial tendon).

*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. Funds were received in total or partial support of the research or clinical study presented in this article. The funding source was National Institutes of Health Grant AR17172.

†Orthopedic Biomechanics Laboratory, Mayo Clinic and Mayo Foundation, 200 First Street, S.W., Rochester, Minnesota 55905. Please address requests for reprints to Dr. Amadio.

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Fig. 1 Illustration of the measurement system, consisting of a mechanical actuator with a linear potentiometer, two tensile load-transducers (to measure tension distal [F1] and proximal [F2] to the Az pulley), a mechanical pulley (right), a Dacron cord, and a weight. FDP = flexor digitorum profundus.

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Fig. 2 The effect of load on the gliding resistance. The gliding resistance of the palmaris longus tendon (PL) was significantly greater (p < 0.001) than that of the flexor digitorum profundus tendon (FDP), except at a load of 0.98 newton. The gliding resistance of the flexor digitorum profundus tendon was less sensitive to increasing load than the palmaris longus tendon.

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Fig. 3 The effect of excursion on the measurements from the F1 and F2 load-transducers in a representative set of experimental tests. The load recorded by the F1 transducer was always constant. The force recorded by the F2 transducer increased as excursion of the flexor digitorum profundus tendon (FDP) increased but stayed constant during excursion of the palmaris longus tendon (PL).

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Fig. 4-A Scanning electron microscopic image of a specimen from the surface of the palmaris longus tendon. The tendon has no synovial membrane, but there are remnants of the paratenon. The tendon fibers are exposed. The irregularity of the surface is substantial (X 30).

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Fig. 4-B Scanning electron microscopic image of a specimen from the surface of the flexor digitorum profundus tendon. The tendon has a smooth synovial membrane, and the tendon fibers are not exposed (X 30).

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TABLE I MEAN GLIDING RESISTANCE (IN NEWTONS) OF THE TENDON-PULLEY INTERFACE AT EACH LOAD*

*The flexor digitorum profunds tendon was tested first in Specimens 1 through 7, and the palmaris longus tendon was tested first in Specimens 8 through 14.

	Flexor Digitorum Profunds Tendon					Palmaris Longus Tendon
Specimen	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N
1	0.12	0.17	0.24	0.38	0.46	0.17	0.34	0.64	1.21	1.69
2	0.03	0.06	0.10	0.18	0.26	0.04	0.09	0.22	0.51	0.98
3	0.04	0.06	0.11	0.18	0.23	0.09	0.23	0.49	1.04	1.57
4	0.09	0.12	0.19	0.23	0.35	0.10	0.25	0.49	0.98	1.40
5	0.13	0.23	0.34	0.55	0.75	0.04	0.10	0.21	0.60	1.35
6	0.03	0.05	0.06	0.07	0.10	0.04	0.09	0.17	0.40	0.79
7	0.06	0.08	0.13	0.14	0.22	0.12	0.26	0.52	0.97	1.29
Mean	0.07	0.11	0.17	0.25	0.34	0.09	0.19	0.39	0.82	1.30
Stand. dev.	0.04	0.07	0.10	0.16	0.21	0.05	0.10	0.19	0.31	0.32

8	0.12	0.17	0.23	0.32	0.42	0.14	0.29	0.68	1.44	2.31
9	0.09	0.11	0.15	0.20	0.19	0.01	0.05	0.15	0.43	0.81
10	0.10	0.15	0.24	0.34	0.44	0.11	0.29	0.72	1.63	2.43
11	0.08	0.13	0.21	0.31	0.44	0.09	0.17	0.35	0.70	1.33
12	0.07	0.12	0.21	0.28	0.43	0.13	0.34	0.74	1.47	2.26
13	0.08	0.13	0.22	0.31	0.50	0.06	0.18	0.50	1.26	2.34
14	0.07	0.11	0.17	0.25	0.32	0.12	0.26	0.48	0.93	1.41
Mean	0.09	0.13	0.20	0.29	0.39	0.09	0.23	0.52	1.12	1.84
Stand. dev.	0.02	0.02	0.03	0.05	0.10	0.05	0.10	0.22	0.45	0.65

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TABLE I MEAN GLIDING RESISTANCE (IN NEWTONS) OF THE TENDON-PULLEY INTERFACE AT EACH LOAD*

*The flexor digitorum profunds tendon was tested first in Specimens 1 through 7, and the palmaris longus tendon was tested first in Specimens 8 through 14.

	Flexor Digitorum Profunds Tendon					Palmaris Longus Tendon
Specimen	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N
1	0.12	0.17	0.24	0.38	0.46	0.17	0.34	0.64	1.21	1.69
2	0.03	0.06	0.10	0.18	0.26	0.04	0.09	0.22	0.51	0.98
3	0.04	0.06	0.11	0.18	0.23	0.09	0.23	0.49	1.04	1.57
4	0.09	0.12	0.19	0.23	0.35	0.10	0.25	0.49	0.98	1.40
5	0.13	0.23	0.34	0.55	0.75	0.04	0.10	0.21	0.60	1.35
6	0.03	0.05	0.06	0.07	0.10	0.04	0.09	0.17	0.40	0.79
7	0.06	0.08	0.13	0.14	0.22	0.12	0.26	0.52	0.97	1.29
Mean	0.07	0.11	0.17	0.25	0.34	0.09	0.19	0.39	0.82	1.30
Stand. dev.	0.04	0.07	0.10	0.16	0.21	0.05	0.10	0.19	0.31	0.32

8	0.12	0.17	0.23	0.32	0.42	0.14	0.29	0.68	1.44	2.31
9	0.09	0.11	0.15	0.20	0.19	0.01	0.05	0.15	0.43	0.81
10	0.10	0.15	0.24	0.34	0.44	0.11	0.29	0.72	1.63	2.43
11	0.08	0.13	0.21	0.31	0.44	0.09	0.17	0.35	0.70	1.33
12	0.07	0.12	0.21	0.28	0.43	0.13	0.34	0.74	1.47	2.26
13	0.08	0.13	0.22	0.31	0.50	0.06	0.18	0.50	1.26	2.34
14	0.07	0.11	0.17	0.25	0.32	0.12	0.26	0.48	0.93	1.41
Mean	0.09	0.13	0.20	0.29	0.39	0.09	0.23	0.52	1.12	1.84
Stand. dev.	0.02	0.02	0.03	0.05	0.10	0.05	0.10	0.22	0.45	0.65

Materials and Methods

Introduction | Materials and Methods | Results | Discussion | References

We previously described the concept of the arc of contact for measurement of friction between a cable and a fixed mechanical pulley and its accuracy and application to the tendon-pulley unit¹⁸.

Ten normal index and four normal long fingers and the ipsilateral palmaris longus tendons from fourteen fresh-frozen hands from cadavera were studied. A fifteen-centimeter segment of the palmaris longus tendon was obtained, with the distal end cut at the level of the distal wrist crease. The paratenon was removed carefully under an operating microscope^12,14. Great care was taken not to damage the surface of the tendon.

The finger was prepared as follows. A transverse incision was made in the synovial sheath, just distal to the A2 pulley, in order to mark the lateral surface of the flexor digitorum profundus tendon with the finger in full extension. The tendon then was pulled proximally to allow full flexion of the proximal and distal interphalangeal joints. At this position, the tendon was marked again through the previous incision. The distance between the two marks (mean distance and standard deviation, 18.9 ± 2.2 millimeters; range, fifteen to twenty-two millimeters) represented the excursion of the tendon at the A2 pulley. The synovial membrane, the other pulleys, and the flexor digitorum superficialis tendon then were removed. The A2 pulley (mean length and standard deviation, 15.9 ± 2.5 millimeters; range, twelve to twenty millimeters), the parietal membrane of the A2 pulley, and the gliding surface of the flexor digitorum profundus tendon were preserved.

The flexor digitorum profundus tendon was divided at its insertion and pulled out of the pulley. To measure the pure interaction between the A2 pulley and the tendon, the bone distal to the distal edge and proximal to the proximal edge of the A2 pulley was removed. A 1.5-millimeter Kirschner wire was inserted through the phalanx parallel to the long axis of the bone. The surface of the tendon was washed gently with saline solution to remove any synovial fluid. Once the bone had been prepared, the tendon was put through the A2 pulley. The proximal part of the phalanx and the A2 pulley from each finger were used to test the flexor digitorum profundus tendon and the corresponding palmaris longus tendon of the same hand.

The prepared specimen was mounted on the testing device. The measurement system consisted of one mechanical actuator with a linear potentiometer, two tensile load-transducers, a mechanical pulley, a Dacron cord, and a weight (Fig. 1). Load-transducers were connected to the proximal and distal ends of the tendon. The proximal load-transducer was connected to the mechanical actuator and the distal load-transducer, to the weight. The actuator was positioned at an angle of 30 degrees, defined as the angle formed between the horizontal plane and the proximal cable extension. The mechanical pulley between the load and the distal load-transducer was positioned at 20 degrees, defined as the angle formed between the horizontal plane and the distal cable extension.

The tendon was pulled proximally by the actuator against the weight at a rate of 2.0 millimeters per second. The tension of the tendon distal (F1) and proximal (F2) to the A2 pulley and the corresponding excursion in the distance between the two previously defined markers were recorded at a sampling rate of ten hertz. The actuator then was reversed, releasing the tendon to move distally. The actuator was put in reverse and the tendon was released at the same rate, with the weight used to maintain tension in the system. Displacement of the tendon was recorded by the potentiometer. This sequence was repeated for two trials, each at five different loads: 0.98, 2.45, 4.9, 9.8, and 14.7 newtons. These loads are representative of those seen with light activity^2,13. The load was set again at 0.98 newton, and the same sequence was repeated, with two trials at each load.

The specimens were randomly divided into two groups. In one (Specimens 1 through 7, Table I), the flexor digitorum profundus tendon was tested before the palmaris longus tendon. In the other (Specimens 8 through 14, Table I), the palmaris longus tendon was tested first. The reproducibility of the measurements was confirmed in our previous study¹⁸. The palmaris longus tendon was put through the A2 pulley in its normal anatomical orientation—that is, with the tendon insertion distal and the anterior surface anterior. The excursion and the relative position of the insertion site of the palmaris longus tendon were determined so that they were identical to those of the flexor digitorum profundus tendon. The specimens were kept moist in a bath of saline solution during the procedure.

In order to assess the completeness of the excision of the paratenon, specimens from the surfaces of both types of tendon were observed with scanning electron microscopy after the testing had been completed. The presence or absence of a smooth synovial covering layer also was determined.

Analysis of the Data

Plots of the force measurements (F1 and F2) versus excursion in flexion were examined for each trial and their shapes were evaluated. Since the data from all trials generally were identical and the first trial was considered preconditioning, the data from the second trial of each of the two sequences were selected and the two values were averaged for analysis.

The mean difference between the F1 and F2 forces for the whole excursion was considered to be the gliding resistance between the tendon and the pulley. The gliding resistance of the palmaris longus tendon was compared with that of the flexor digitorum tendon, with use of five paired t tests with Bonferroni correction of an adjusted significance level at p < 0.01 (0.05/5) to maintain the over-all protection level at each load.

The frictional force was plotted against the load for both types of tendon. A line was fitted with use of the least-squares method for each specimen. The slopes were compared with use of a paired t test.

Results

Introduction | Materials and Methods | Results | Discussion | References

The gliding resistance of the palmaris longus tendon was significantly greater (p < 0.001) than that of the flexor digitorum profundus tendon at all loads except the lowest one (0.98 newtons) and for each direction that was tested (Table I). The gliding resistance of the flexor digitorum profundus tendon changed less with increasing tension of the tendon than did that of the palmaris longus tendon (Fig. 2). The average slope (and standard deviation) for the plot of the frictional force versus load was 0.023 ± 0.011 for the flexor digitorum profundus tendon and 0.108 ± 0.04 for the palmaris longus tendon. This difference was significant (p < 0.001).

The pattern of the F2 force also was different for the two tendons. The F2 force for the flexor digitorum profundus tendon tended to increase as excursion progressed, whereas the F2 force for the palmaris longus tendon stayed almost constant throughout excursion (Fig. 3). These patterns were consistent for both tendons. Scanning electron microscopy revealed that remnants of the paratenon remained on the surface of the palmaris longus tendons (Fig. 4-A). The flexor digitorum profundus tendons had a smooth gliding surface (Fig. 4-B).

Discussion

Introduction | Materials and Methods | Results | Discussion | References

There are remarkable differences between the gross anatomy of the flexor digitorum profundus and that of the palmaris longus tendon⁵. The palmaris longus tendon is flat, with a uniform cross-sectional shape³, whereas the flexor digitorum profundus tendon has a variety of cross-sectional shapes and areas. Because of this constantly changing profile, there may be more change in the contact area, throughout excursion, between the flexor digitorum profundus tendon and the A2 pulley than between the palmaris longus tendon and the A2 pulley. This may explain why the F2 force stayed relatively constant during excursion of the palmaris longus tendon but varied during excursion of the flexor digitorum profundus tendon (Fig. 3).

The differences between the palmaris longus and flexor digitorum profundus tendons with regard to the magnitude and pattern of gliding resistance also may be due to differences in the surface structure. The palmaris longus tendon is extrasynovial and thus does not have a synovial membrane. Instead, it has a paratenon of loose connective tissue. For this study, we removed the paratenon, but scanning electron microscopy of specimens from the surface of the tendon demonstrated that remnants of the paratenon remained on the surface and may have acted to resist gliding (Fig. 4-A). In contrast, the flexor digitorum profundus tendon had a gliding surface of smooth synovial membrane^10,15 (Fig. 4-B). Although the cells of this membrane also secrete synovial fluid in vivo, which is believed to be important for lubrication⁸, this of course was not a factor in our in vitro test protocol. Additionally, the surface of the flexor digitorum profundus tendon may contain fibronectins, which may bind to lipid or hyaluronic acid^3,4. These complexes could act as a lubrication between the tendon and the pulley. Since the gliding resistance of the flexor digitorum profundus tendon was less sensitive to increases in load than was the gliding resistance of the palmaris longus tendon, it is also possible that boundary lubrication occurred¹⁹ when the flexor digitorum profundus tendon came into contact with the A2 pulley.

There are several limitations of this study. First, this model includes only the contact between the tendon and the A2 pulley. Furthermore, although the cross section of the palmaris longus tendon is relatively uniform, the cross section of the flexor digitorum profundus tendon varies in terms of both shape (circular or oval) and diameter along its length. A detailed study of the effect of cross-sectional shape and diameter of the tendon on gliding resistance is beyond the scope of this paper. Because the flexor digitorum profundus tendon has a larger cross section, it is more likely that it contacts structures other than the A2 pulley in vivo. The in vivo results might therefore be different from our in vitro findings.

Second, the lack of synovial fluid as a lubricant may have exaggerated the results. If synovial fluid had been used as a lubricant, the gliding resistance of both tendons through the A2 pulley may have been reduced. However, if synovial fluid is bound to the surface of the flexor digitorum profundus tendon, that tendon may be well lubricated already, so that extrinsic lubrication with synovial fluid may have a greater effect on the gliding resistance of the palmaris longus tendon than it would have on the flexor digitorum profundus tendon.

Third, the irregularities of the surface of the palmaris longus tendon depended partly on the amount of the paratenon that had been removed. As the paratenon was removed by dissection, the amount may have varied among the specimens, which in turn may have increased the variability of the gliding resistance for the palmaris longus tendon.

Fourth, we studied only one portion of the complex in vivo tendon-sheath interaction. We isolated the interaction between the surface of the tendon and the A2 pulley because clinically this complex seems most important to the kinematics of the flexor tendon in human fingers¹¹. Furthermore, the entire system, which includes a series of pulleys and the intervening synovial membrane, is complicated by the presence of two tendons within the sheath, gliding at different rates. We believe that a study of this complex series of interactions en masse would be unproductive without an understanding of the interactions in a simpler model. We think that our model preserved essential minimum features (a key pulley with an intact parietal surface and a normal tendon with an intact visceral surface) to permit useful analysis.

Last, the speed (2.0 millimeters per second) that was chosen for the testing is slower than that which is normally associated with active gliding of the tendon in vivo. In part, this speed was dictated by our model, which uses quasistatic mechanics to determine the frictional coefficient. This coefficient may vary with rate.

Although it is not possible to determine the actual gliding resistance of these two tendons when they pass through the A2 pulley in vivo, we have demonstrated that the in vitro gliding pattern throughout excursion was different for the two tendons and that the potential gliding ability of the palmaris longus tendon through the A2 pulley was inferior to that of the flexor digitorum profundus tendon. We believe that it is important to assess the gliding ability because a tendon graft may have to glide through the pulley under suboptimum conditions, such as contamination of synovial fluid with blood, injury to the sheath, or an osseous deformity. In this regard, we believe that it is instructive to relate our work to recent in vivo experiments with the canine flexor-tendon model^6,14. A different biological response and healing process for the two different types of tendon (extrasynovial and intrasynovial) has been confirmed in vivo^6,14. This differential healing response may be an effect of the poorer gliding ability of extrasynovial tendons such as the palmaris longus tendon. Gelberman et al.⁶ demonstrated that this differential effect is associated with the formation of more adhesions on extrasynovial grafts than on intrasynovial grafts, and Seiler et al. showed that this response occurs even with postoperative passive motion therapy. We believe that increased gliding resistance may explain both of these observations. Adhesions may be more likely to form on the irregular paratenon-covered surface of an extrasynovial tendon (Fig. 4-A) than on the smoother surface of an intrasynovial tendon (Fig. 4-B). Passive motion may not produce gliding if resistance is high; instead, the tendon may buckle, possibly aggravating the tendency to form adhesions⁹. We believe that this latter situation may be even more of a problem in vivo, as postoperative edema and inflammation may cause additional resistance to gliding.

References

Introduction | Materials and Methods | Results | Discussion | References

An, K.-N.; Berglund, L.; Uchiyama, S.; and |and |Coert, J. H.: Measurement of friction between pulley and flexor tendon. Biomed. Sci. Instrum.,29: 1-7, 1993.291 1993

An, K.-N.; Berglund, L.; Cooney, W. P.; Chao, E. Y.; and |and |Kovacevec, N.: Direct in vivo tendon force measurement system. J. Biomech.,23: 1269-1271, 1990.231269 1990 [PubMed]

Banes, A. J.; Link, G. W.; Bevin, A. G.; Peterson, H. D.; Gillespie, Y.; Bynum, D.; Watts, S.; and |and |Dahners, L.: Tendon synovial cells secrete fibronectin in vivo and in vitro. J. Orthop. Res.,6: 73-82, 1988.673 1988 [PubMed]

Banes, A. J.; Donlon, K.; Link, G. W.; Gillespie, Y.; Bevin, A. G.; Peterson, H. D.; Bynum, D.; Watts, S.; and |and |Dahners, L.: Cell populations of tendon: a simplified method for isolation of synovial cells and internal fibroblasts: confirmation of origin and biologic properties. J. Orthop. Res.,6: 83-94, 1988.683 1988 [PubMed]

Carlson, G. D.; Botte, M. J.; Josephs, M. S.; Newton, P. O.; Davis, J. L.; and |and |Woo, S. L.: Morphologic and biomechanical comparison of tendons used as free grafts. J. Hand Surg.,18A: 76-82, 1993.18A76 1993

Gelberman, R. H.; Chu, C. R.; Williams, C. S.; Seiler, J. G., III; and |and |Amiel, D.: Angiogenesis in healing autogenous flexor-tendon grafts. J. Bone and Joint Surg.,74-A: 1207-1216, Sept. 1992.74-A1207 1992

Gelberman, R. H.; Seiler, J. G., III; Rosenberg, A. E.; Heyman, P.; and |and |Amiel, D.: Intercalary flexor tendon grafts. A morphological study of intrasynovial and extrasynovial donor tendons. Scandinavian J. Plast. and Reconstr. Surg. and Hand Surg.,26: 257-264, 1992.26257 1992

Hagberg, L.; Heinegard, D.; and |and |Ohlsson, K.: The contents of macromolecule solutes in flexor tendon sheath fluid and their relation to synovial fluid. A quantitative analysis. J. Hand Surg.,17-B: 167-171, 1992.17-B167 1992

Horii, E.; Lin, G. T.; Cooney, W. P.; Linscheid, R. L.; and |and |An, K.-N.: Comparative flexor tendon excursion after passive mobilization: an in vitro study. J. Hand Surg.,17A: 559-566, 1992.17A559 1992

Inoue, H.; Takasugi, H.; and |and |Akahori, O.: Surface study of tenosynovium in hens and humans by electron microscopy. Hand,8: 222-227, 1976.8222 1976 [PubMed]

Lin, G.-T.; Amadio, P. C.; An, K.-N.; and |and |Cooney, W. P.: Functional anatomy of the human digital flexor pulley system. J. Hand Surg.,14A: 949-956, 1989.14A949 1989

Schneider, L. H., Hunter, J. M.: Flexor tendons—late reconstruction. In Operative Hand Surgery, edited by D. P. Green. Ed. 2, vol. 3, pp. 1969-2044. New York, Churchill Livingstone, 1988.

Schuind, F.; Garcia-Elias, M.; Cooney, W. P., III; and |and |An, K.-N.: Flexor tendon forces: in vivo measurements. J. Hand Surg.,17A: 291-298, 1992.17A291 1992

Seiler, J. G., III; Gelberman, R. H.; Williams, C. S.; Woo, S. L-Y.; Dickersin, G. R.; Sofranko, R.; Chu, C. R.; and |and |Rosenberg, A. E.: Autogenous flexor-tendon grafts. A biomechanical and morphological study in dogs. J. Bone and Joint Surg.,75-A: 1004-1014, July 1993.75-A1004 1993

Steinberg, P. J., and |and |Hodde, K. C.: The morphology of synovial lining of various structures in several species as observed with scanning electron microscopy. Scan. Microsc.,4: 987-1020, 1990.4987 1990

Strickland, J. W.: Flexor tendon surgery. Part 1: primary flexor tendon repair. J. Hand Surg.,14-B: 261-272, 1989.14-B261 1989

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Uchiyama, S.; Coert, J. H.; Berglund, L.; Amadio, P. C.; and |and |An, K.-N.: Method for the measurement of friction between tendon and pulley. J. Orthop. Res.,13: 83-89, 1995.1383 1995 [PubMed]

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TABLE I MEAN GLIDING RESISTANCE (IN NEWTONS) OF THE TENDON-PULLEY INTERFACE AT EACH LOAD*

*The flexor digitorum profunds tendon was tested first in Specimens 1 through 7, and the palmaris longus tendon was tested first in Specimens 8 through 14.

	Flexor Digitorum Profunds Tendon					Palmaris Longus Tendon
Specimen	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N
1	0.12	0.17	0.24	0.38	0.46	0.17	0.34	0.64	1.21	1.69
2	0.03	0.06	0.10	0.18	0.26	0.04	0.09	0.22	0.51	0.98
3	0.04	0.06	0.11	0.18	0.23	0.09	0.23	0.49	1.04	1.57
4	0.09	0.12	0.19	0.23	0.35	0.10	0.25	0.49	0.98	1.40
5	0.13	0.23	0.34	0.55	0.75	0.04	0.10	0.21	0.60	1.35
6	0.03	0.05	0.06	0.07	0.10	0.04	0.09	0.17	0.40	0.79
7	0.06	0.08	0.13	0.14	0.22	0.12	0.26	0.52	0.97	1.29
Mean	0.07	0.11	0.17	0.25	0.34	0.09	0.19	0.39	0.82	1.30
Stand. dev.	0.04	0.07	0.10	0.16	0.21	0.05	0.10	0.19	0.31	0.32

8	0.12	0.17	0.23	0.32	0.42	0.14	0.29	0.68	1.44	2.31
9	0.09	0.11	0.15	0.20	0.19	0.01	0.05	0.15	0.43	0.81
10	0.10	0.15	0.24	0.34	0.44	0.11	0.29	0.72	1.63	2.43
11	0.08	0.13	0.21	0.31	0.44	0.09	0.17	0.35	0.70	1.33
12	0.07	0.12	0.21	0.28	0.43	0.13	0.34	0.74	1.47	2.26
13	0.08	0.13	0.22	0.31	0.50	0.06	0.18	0.50	1.26	2.34
14	0.07	0.11	0.17	0.25	0.32	0.12	0.26	0.48	0.93	1.41
Mean	0.09	0.13	0.20	0.29	0.39	0.09	0.23	0.52	1.12	1.84
Stand. dev.	0.02	0.02	0.03	0.05	0.10	0.05	0.10	0.22	0.45	0.65

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TABLE I MEAN GLIDING RESISTANCE (IN NEWTONS) OF THE TENDON-PULLEY INTERFACE AT EACH LOAD*

*The flexor digitorum profunds tendon was tested first in Specimens 1 through 7, and the palmaris longus tendon was tested first in Specimens 8 through 14.

	Flexor Digitorum Profunds Tendon					Palmaris Longus Tendon
Specimen	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N	0.98 N	2.45 N	4.9 N	9.8 N	14.7 N
1	0.12	0.17	0.24	0.38	0.46	0.17	0.34	0.64	1.21	1.69
2	0.03	0.06	0.10	0.18	0.26	0.04	0.09	0.22	0.51	0.98
3	0.04	0.06	0.11	0.18	0.23	0.09	0.23	0.49	1.04	1.57
4	0.09	0.12	0.19	0.23	0.35	0.10	0.25	0.49	0.98	1.40
5	0.13	0.23	0.34	0.55	0.75	0.04	0.10	0.21	0.60	1.35
6	0.03	0.05	0.06	0.07	0.10	0.04	0.09	0.17	0.40	0.79
7	0.06	0.08	0.13	0.14	0.22	0.12	0.26	0.52	0.97	1.29
Mean	0.07	0.11	0.17	0.25	0.34	0.09	0.19	0.39	0.82	1.30
Stand. dev.	0.04	0.07	0.10	0.16	0.21	0.05	0.10	0.19	0.31	0.32

8	0.12	0.17	0.23	0.32	0.42	0.14	0.29	0.68	1.44	2.31
9	0.09	0.11	0.15	0.20	0.19	0.01	0.05	0.15	0.43	0.81
10	0.10	0.15	0.24	0.34	0.44	0.11	0.29	0.72	1.63	2.43
11	0.08	0.13	0.21	0.31	0.44	0.09	0.17	0.35	0.70	1.33
12	0.07	0.12	0.21	0.28	0.43	0.13	0.34	0.74	1.47	2.26
13	0.08	0.13	0.22	0.31	0.50	0.06	0.18	0.50	1.26	2.34
14	0.07	0.11	0.17	0.25	0.32	0.12	0.26	0.48	0.93	1.41
Mean	0.09	0.13	0.20	0.29	0.39	0.09	0.23	0.52	1.12	1.84
Stand. dev.	0.02	0.02	0.03	0.05	0.10	0.05	0.10	0.22	0.45	0.65