WO2001045601A2

WO2001045601A2 - Improved clamp assembly for a non-invasive positioning device system

Info

Publication number: WO2001045601A2
Application number: PCT/US2000/042824
Authority: WO
Inventors: James F. Guhl; Stephen P. Guhl; David J. Guhl
Original assignee: Guhl James F; Guhl Stephen P; Guhl David J
Priority date: 1999-12-23
Filing date: 2000-12-14
Publication date: 2001-06-28
Also published as: AU4525201A; WO2001045601A3

Abstract

An improved clamp assembly for use with a non-invasive ankle distraction positioning system to accommodate arthroscopic procedures provides the ability to apply a wide range of distraction forces to the ankle joint, to hold the ankle in positions above the table in leg positions ranging from nearly horizontal to acutely flexed, and to even position the ankle below the level of the operating table to accommodate special needs and/or positions. The improved clamp assembly includes a base releasably secured to the table and a sleeve releasably secured to the base. The sleeve includes a first high-friction surface on one end adjacent the base that is releasably engagable with a resilient washer and second high-friction surface located on the base. The engagement of the respective high-friction surfaces with the washer and each another allows the distraction system to be fixed in an infinite number of angular positions with respect to the base.

Description

IMPROVED CLAMP ASSEMBLY FOR A NON-INVASIVE POSITIONING DEVICE SYSTEM

BACKGROUND OF THE INVENTION The present invention relates to an apparatus for use in the performance of ankle arthroscopy procedures and, more particularly, to an improved clamp assembly for use with a non- invasive ankle joint distraction system in support of arthroscopic procedures.

As described in my prior U.S. Pat. No. 5,063,918, it is usually necessary to provide some form of ankle joint distraction in order to create sufficient space in the joint for the arthroscope and various other surgical equipment and instruments used in ankle arthroscopy. Furthermore, the degree of distraction will vary depending on the nature of the procedure, the type and size of surgical instruments required, and the relative tightness or looseness of the joint in a particular patient. The method and apparatus in the above patent provides for the use of a basic non- invasive technique and, if the level of distraction it provides is insufficient, the ability to convert without interruption to an invasive distraction technique utilizing pinned connections between the bones of the lower leg and foot.

Relatively recent improvements in the design and construction of arthroscopic instruments include smaller size instruments requiring less space within the joint for adequate performance. In turn, the amount of ankle joint distraction may also be reduced in many cases. As a result, the importance of non- invasive distraction techniques has recently taken on somewhat greater importance relative to invasive techniques. This is also significant because the disadvantages and potential complications of invasive techniques are well documented and these techniques are only utilized when adequate distraction by non-invasive means cannot be attained.

One method of providing non-invasive ankle distraction is shown in U.S. Pat. No. 5,020,525. In this method, a removable strap is attached to the patient's foot and the opposite end of the strap is strung to an outrigger fixed to and extending several feet away from the foot of the operating table. Variable distraction force is applied in a direction generally axially of the patient's leg with a manually operated crank and pulley system. The method provides good distraction and the ability to control the amount of the distraction force. However, the horizontal position of the leg and foot results in difficult access to posterior portals of the ankle and also results in the problem of water or saline solution running down the arthroscope and into the camera. The outrigger mechanism may also create an obstacle to the surgeon. Finally, the need to convert to invasive distraction means requires complete repositioning of the patient which is cumbersome and time consuming.

In another known method, the patient is positioned supine at the end of the operating table with the hip and knee flexed and the lower leg depending downwardly from the end of the table over a padded horizontal bar behind the knee. Distraction of the ankle joint is provided by pulling vertically downward on a strap attached to the foot of the patient and secured to a pivotal cantilevered arm below the table. This method does not offer much variation in position and requires careful attention to the potential circulatory problems attendant the application of pressure to the popliteal area with the knee acutely flexed over the padded bar. My prior U.S. Pat. No. 5,290,220 describes a non-invasive distraction technique which allows variable positioning of the ankle above the operating table to accommodate access to the ankle joint from any direction. The non- invasive methods disclosed in this patent utilize an adjustable distraction device attached between the foot of the patient and the Clark rail on the operating table to provide a variable level of joint distraction. However, a deficiency in the system disclosed in this patent has been noted. The deficiency is that the serrated surfaces on the adjustable clamp only allow the distraction system to be fixed in a specified number of angular positions with respect to the operating table. In some instances, in order to obtain the optimal position for the particular arthroscopy procedure, it may be necessary to fix the distraction system in an angular position not available with the serrated surfaces on the adjustable clamp. Therefore, it is desirable to develop an improved adjustable clamp assembly for use with a non-invasive ankle distraction system that enables the distraction system to be fixed in an infinite number of angular positions with respect to the operating table.

SUMMARY OF THE INVENTION In accordance with the present invention, the deficiencies in prior art non- invasive ankle distraction techniques have been overcome with a system which provides the ability to hold the ankle in a convenient position above the table in leg positions ranging from a full extension position of 180° to a full flexion position of about 35°.

In the system of the present invention, a conventional operating table is used to support the patient on his back in a generally horizontal position. A conventional urology leg holder is used to support the patient's leg posteriorly of the knee joint where it may be maintained in a selected position between full extension (horizontal) and acutely flexed, with the leg holder attached directly to the operating table below the knee and including means for adjusting the height at which the knee joint is held above the table. The distraction means includes an elongate body having an axially adjustable length and a first end by which it is attached to the foot of the patient. A manually operable or rotatable lever arm has one end attached to the operating table and an opposite end attached to the second end of the body of the distractor. An improved adjustable clamp assembly is attached to one edge of the operating table and includes first clamping means to fix the position of the clamp assembly along the table edge and a second clamping means to which the opposite end of the lever arm is attached, permitting the lever arm to be rotated manually in a generally vertical plane and clamped in an initial selected position to impose a tensile load on the distractor and an initial level of distraction of the ankle joint. The initial level of ankle joint distraction may be varied by adjusting means on the distractor device.

In a preferred embodiment, the improved clamp assembly includes high friction, knurled surfaces on the engagable portions of the second clamping means. The knurled surfaces can be engaged in any orientation and allow the lever arm secured by the second clamping means to be placed in an infinite number of angular positions with respect to the operating table.

The clamp assembly may also include a washer formed of a deformable material positioned between the knurled surfaces to enhance the engagement of the knurled surfaces with each other.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING Fig. 1 is a side elevation view showing the apparatus of the present invention attached to a patient with the leg in a slightly flexed position. Fig. 2 is a side elevation view similar to Fig. 1 showing the leg of the patient in a more acutely flexed position.

Fig. 3 is a side elevation view showing the apparatus of the present invention utilized with the hinged end of the operating table tilted downwardly.

Fig. 4 is a side elevation view similar to Fig. 3 showing the hinged end of the table tilted further downwardly.

Fig. 5 is an end elevation view of the apparatus and patient taken on line 5-5 of Fig. 4 and in a plane generally parallel to the hinged end of the table. Fig. 6 is a cross-sectional view along line 6-6 of Fig. 5. Fig. 7 is a cross-sectional view along line 7-7 of Fig. 6. Fig. 8 is a sectional view along line 8-8 of Fig. 6.

Fig. 9 is an exploded view of the clamp assembly of the present invention. DETAILED DESCRIPTION OF THE INVENTION Referring initially to Fig. 1, a conventional operating table 10 includes a standard Clark rail 11 attached to one lateral edge of the table in a well known manner. The patient is positioned supine on the operating table 10 with the leg 12 of the patient supported at the back of the knee vertically above the table. The leg is only slightly flexed (nearly horizontal). Leg support is provided by a conventional gynecological or urological leg holder 13 attached in a known manner to the Clark rail 11. The leg holder 13 includes a support arm 14 adjustably attached to the

Clark rail 11 by a clamp 15 which allows the assembly to be slid along the rail, pivoted in a horizontal plane, and moved vertically up or down. The upper end of the support arm 14 is connected to the leg holder 13 with a pivot mechanism 16 that allows the holder to be adjustably pivoted in either a horizontal or a vertical plane.

The leg holder 13 can easily be adjusted in three planes of rotation and its height readily varied as will be described hereinafter. The leg is generously padded with a heavy foam rubber padding 17 to provide as much cushioning as is practicable, thereby minimizing as much as possible pressure on the posterior thigh and leg, primarily in the popliteal area.

The distraction apparatus of the present invention includes an axially adjustable distractor 18 attached by a first end 20 to the foot of the patient and by a second end 21 to the operating table, via a lever arm 22 having one end 23 pivotally attached to the Clark rail and the other end 24 connected to the second end 21 of the distractor 18.

Attachment of the distractor 18 to the foot of the patient is provided by a foot strap 25 including an adjustable VELCRO fastener band 26 placed around the ankle above the heel and instep and a connecting strap 27, including looped ends 28 on either side of the foot through which the VELCRO fastener band 26 is threaded.

The doubled connecting strap 27 is threaded through a connector loop 30 attached to the first end 20 of the distractor by a swivel joint 31. Referring also to Fig. 5, the main body of the distractor 18 comprises a threaded bolt 32 to which the swivel joint 31 is attached. The threaded bolt 32 can be any desired length in order to reduce the cost of the distractor 18, so long as the bolt is of a sufficient length to provide the desired function. A length adjustment mechanism 33 is attached to the second end 21 of the threaded bolt 32. The adjustment mechanism includes a manually operable, threaded adjustment nut and an attached mount 35 for an attachment strap 36. The mount 35 is connected to the adjustment nut 34 with a swivel connection so that the adjustment nut 34 can be rotated on the threaded bolt 32 to change the position of the adjustment mechanism therealong without rotating the mount 35 or attachment strap 36. The attachment strap 36 may comprise a piece of conventional nylon webbing or the like extending through slots (not shown) on opposite sides of the mount 35 and looped around one leg 38 of the L-shaped lever arm 22, as best seen in Fig. 5. The end of leg 38 includes a reduced diameter section 39 within which the strap 36 is placed to prevent it from slipping off.

The other leg 40 of the lever arm 22 has its free end 41 attached to the Clark rail 11 for adjustable positioning rotationally about its free end 41 and axially along the leg 40. Attachment of the leg 40 to the Clark rail 11 is provided by an improved adjustable clamp assembly 42. The clamp includes a clamp body 44 mounted for slidable movement along the Clark rail 11 and a clamp head 45 rotatably attached to the clamp body 44 and movable into clamping engagement therewith by rotation of an operating arm 43. The clamp body includes a set screw 47 for fixing the position of the clamp along the Clark rail. The clamp head 45 includes a diametral through bore 46 for receiving the leg 40 of the lever arm 22, and the clamp head is configured internally to simultaneously clamp the leg 40 in the bore 46 and the clamp head to the clamp body 44 by rotation of the operating arm 43. Similarly, rotation of the operating arm in the opposite direction simultaneously unclamps the clamp head 45 from the body 44 so the head and lever arm may be rotated with respect thereto and the leg 40 can be positioned axially in the through bore 46. The improved clamp assembly 42 of the present invention is most clearly shown in Figs. 6-9. In the assembly 42, the clamp body 44 includes a circular housing opening 54 adjacent the set screw 47. The housing opening 54 is surrounded by a raised, knurled engaging surface 56 that assists in angularly positioning the distraction system on the table.

A generally cylindrical housing 58 is rotatably disposed within the housing opening 54. The housing 58, which forms a portion of the clamp head 45, is generally cylindrical in shape and includes the through bore 46 that receives the leg 40 of the lever arm 22. The housing 58 also includes a stop 60 disposed at the lower end of the housing which engages the surface of the clamp body opposite the engaging surface 56 to properly position the housing 58 within the housing opening 54. Opposite the stop 60, the housing 58 has a tapered upper end 62 including a threaded bore 64 that receives the operating arm 43 that is used to secure the lever arm leg 40 within the housing 58. The housing 58 also includes a pin bore 66 disposed between the stop 60 and upper end 62 which receives a pin 68 to retain the housing 58 within the housing opening 54.

A washer 70 is disposed about the housing 58 in engagement with the engaging surface 56. The washer 70 is formed of a resilient material and assists the engaging surface 56 in retaining the lever arm 22 in the desired angular position. Preferably, the washer 70 is a soft polymeric material, and most preferably is formed from Teflon, Viton, Torlon, or Delrin.

The clamp head 45 also includes a clamp sleeve 71 disposed around the housing 58 opposite the stop 60 that engages the washer 70. The clamp sleeve 71 is generally cylindrical in shape and includes a knurled clamping surface 72 at a lower end that is engagable with the washer 70. The clamp sleeve 71 also includes a pair of lever arm openings 74, 76 located on opposite sides of the clamp sleeve 71 and alignable with the through bore 46 in the housing 58. Thus, the leg 40 of the lever arm 22 can be inserted through both the lever arm openings 74, 76 and the through bore 46 to properly position the lever arm 22 with respect to the table. The clamp sleeve 71 also has a pin opening 78 disposed between and level with the lever arm openings 74, 76. The pin opening 78 is aligned with the pin bore 66 on the housing 58 when lever arm openings 74 and 76 are aligned with the through bore 46 such that the pin 68 can be inserted through the pin opening 78 into the pin bore 66 to retain the clamp sleeve 71 and housing 58 on the clamp body 44. To releasably secure the lever arm 22 within the clamp sleeve 71 and housing 58, and the clamp head 45 to the clamp body 44, the operating arm 43 is threadably engaged with the threaded bore 64 in the housing 58. The operating arm 43 comprises a threaded bolt 80 including a handle opening 82 opposite the threaded portion of the bolt. A handle 84 is disposed within the handle opening 82 to allow the manual rotation of the bolt 80 to secure the lever arm 22 and clamp head 45 in the desired configuration on the clamp body 44.

When the clamp head 45 is engaged with the clamp body 44, the clamping surface 72 on the clamp sleeve 71 is compressed against the washer 70 positioned on engaging surface 56 on the clamp body 44. As shown in Figs. 7-9, both the clamping surface 72 and the engaging surface include high-friction, knurled surfaces that allow the clamping surface 72 to securely engage the washer 70 and engaging surface 56 in an infinite number of angular positions of the clamp head 45 with respect to the clamp body 44. This arrangement can also be altered to provide the same function by positioning the washer 70 against the clamping surface 72, or by moveably disposing the washer 70 between the engaging surface 56 and clamping surface 72. In any of these arrangements, the clamp assembly 42 enables an individual to easily position the lever arm 22 in an infinite number of angular positions with respect to the operating table 10. Therefore, the lever arm 22 and distractor 18 can be fixed in any position necessary for a particular arthroscopy procedure.

Furthermore, while the preferred embodiment is to provide both a high- friction, knurled clamping surface 72 and a high-friction, knurled engaging surface 56, in another embodiment it is also feasible to provide only one knurled surface on either the clamping surface 72 or the engaging surface 56. For example, the knurled clamping surface 72 can engage the washer 70 positioned against a smooth engaging surface 56 to secure the lever arm in the desired angular position.

Also, while the engagement of the clamping surface 72 with the engaging surface 56 is enhanced by the positioning of the washer 70 between the surfaces, in still another embodiment of the invention, the washer 70 can be omitted entirely from the assembly. In this embodiment, the knurled clamping surface 72 directly engages either a smooth or knurled engaging surface 56 to securely engage the clamp head 45 with the clamp body 44. In still another embodiment it is possible to form the engaging surface 56 and the clamping surface 72 by blunting the teeth (not shown) disposed on the clamp body 44 and clamp head 45 of the ankle distraction device disclosed in U.S.^' Patent No. 5,290,220 to a length of about 1 mm. This arrangement allows the blunted teeth to engage one another in a number of selected positions without having to displace the clamp head 45 an extended distance from the clamp body 44. In any of the above-described embodiments, the material which forms the clamp body 44 and clamp head 45 is preferably a metal. However, the material forming these components of the clamp assembly 42 may also be a resilient composite material, such as a carbon fiber composite, or a rigid thermoplastic material such as a polyaryletherketone. Materials of these types provide the rigidity necessary for the components of the clamp assembly 42, while also greatly reducing the weight of the overall assembly 42. Furthermore, these materials still enable the various parts of the clamp assembly 42 to withstand the necessary sterilization temperatures. For the same reasons, the lever arm 22 may also be formed of a composite material or a rigid thermoplastic material other than a metal. Preferably, whether the lever arm 22 is formed of a metal, composite, or thermoplastic material, the lever arm 22 is a solid piece of that material. However, the lever arm 22 may also be formed such that the lever arm has a hollow interior in order to greatly reduce the weight and cost of production of the lever arm 22, without any significant reduction in the strength of the lever arm. The other parts of the distractor 18 and clamp assembly 42 may also be formed to be hollow.

Arthroscopic procedures utilizing non-invasive distraction techniques are preferably commenced utilizing the distraction position shown in Fig. 1. The support arm 14 for the leg holder 3 is positioned in a mid-height position and fixed with the clamp 15. With the patient in a supine position, the leg is placed in the leg holder 13 with the knee slightly flexed to about 20°. This initial position of near extension reduces the pressure on the posterior thigh and leg, primarily the popliteal area. The VELCRO fastener band 26 is placed around the foot and is attached to the end of the distractor 18 by the connecting strap 27. The other end of the distractor is attached to the horizontal leg 38 of the L-shaped lever arm 22 by the attachment strap 36, and the other leg 40 of the lever arm is initially positioned loosely in the through bore 46 in the clamp head 45. The clamp body 44 is positioned in an appropriate position on the Clark rail 11 and clamped thereto with the set screw 47. The lever arm 22 is then manually rotated (e.g. by the surgeon's assistant) around the end 41 held in the clamp 42 in a counterclockwise direction as viewed in Fig. 1. The position of clamp 42 on the Clark rail or the position along the leg 40 of the lever arm 22 may be adjusted as necessary to place the axis of the distractor 18 in generally axial alignment with the lower leg of the patient.

Continued rotation of the lever arm 22 in the clockwise direction will impose a tensile load on the ankle joint and provide an initial level of joint distraction. The initial level of distraction need only be very slight and just enough to hold the patient's leg and the apparatus firmly in position. The operating arm 43 of the clamp 42 is then turned to clamp the lever arm leg 40 in the through bore 46 to simultaneously establish its angular position with respect to the operating table and its axial position along the length of the leg.

If additional distraction is needed beyond a level which can be adequately supported by the patient's knee only slightly flexed (Fig. 1), it may be necessary to more acutely flex the knee to a position shown, for example, in Fig. 2. The Fig. 2 angle of the lower leg may also position the posterior of the ankle joint in a more desirable position for the surgeon requiring entry through the posterior portals. The adjustment from the Fig. 1 to the Fig. 2 position is easily effected by raising the leg holder 13 to a slightly higher position and sliding the clamp 42 along the Clark rail 11 toward the leg holder. These adjustments may be made simply and with little loss of time and without affecting the sterile draping. Also, no other repositioning of the distraction apparatus may be needed, although as shown in Fig. 2, the leg 40 of the lever arm 22 may be lengthened somewhat with respect to the position of the free end 41 of the leg in the clamp 42.

In either of the Fig. 1 or Fig. 2 positions, it will be appreciated that the vertical position of the ankle above the operating table 10 can be varied considerably and as desired by varying the position of the leg 40 of the lever arm in the adjustable clamp 42. Furthermore, if necessary, the leg could be flexed even more acutely than shown in the Fig. 2 position with similar adjustments to the leg holder and distractor as previously described. However, in the more acutely flexed positions, the pressure which can be applied to the popliteal area is potentially greater and circulation must be monitored.

To facilitate certain procedures or to accommodate the personal preference of the surgeon, the apparatus of the present invention allows further significant adjustments in the height and relative position of the ankle joint in a manner utilizing simple adjustment of the type previously described, with little loss of time, and without affecting the sterile draping. By additionally utilizing a table end 48 which can be pivoted or tilted downwardly about a laterally disposed hinge 50 and locked in a tilted position, the lower leg may be positioned nearly vertical or even below the level of the operating table 10, if desired. The hinge 50 is positioned between the adjustable clamp 42 for the lever arm and the clamp 15 for the leg holder support arm 14. The leg holder clamp 15 may be adjusted to position the leg holder close to the hinge 50 to accommodate the downwardly depending positions of the leg as shown in Figs. 3 and 4. The Fig. 3 position may be suitable for most diagnostic work and some surgery. In this position, the ankle may be placed closer vertically to the horizontal top of the operating table, but because of the downwardly dependent table end 48, the table does not provide as significant an obstruction to surgeon procedures and access to the entire ankle joint is relatively uninhibited.

If posterior lateral entry is required or if a lower position of the ankle is more convenient to the surgeon, the table end 48 may be tilted downwardly to an even greater acute angle with respect to the horizontal table top and locked in the Fig. 4 position. This position may require the leg holder to be positioned closer to the hinge by repositioning the leg holder clamp 15. This, in turn, may also necessitate repositioning the adjustable clamp 42 on the table end 48 to move it closer to the distal end thereof. It is also possible to continue adjustments of the leg holder 15, table end 48, and clamp 42 to flex and position the leg from an angle of 180° to an angle of about 35°.

Should invasive distraction techniques, such as those described in my prior U.S. Pat. No. 5,063,918, become necessary during procedures performed in any of the positions of Figs. 1-4, conversion to such invasive techniques can be made quickly and without reprepping or redraping as indicated in that patent. As may best be seen in Fig. 5, the distractor 18 includes an adjustable head 51 for holding the pins used in invasive distraction techniques and, similarly, the mount 35 on the adjustment mechanism 33 at the other end of the distractor includes a similar head 52 for the other pins used in an invasive procedure, all as described in the above identified patent. Thus, in converting from the non-invasive techniques described herein to an invasive technique, the same distractor 18 can be utilized. This provides both a convenience to the surgeon and a significant cost savings.

Various alternatives and embodiments are contemplated as being within the scope of the following claims particularly pointing out and distinctly claiming the subject matter regarded as the invention.

Claims

CLAIMS I claim:

1. An improved adjustable clamp assembly for use with a non-invasive distraction system for ankle joint arthroscopy, the clamp assembly comprising: a first member releasably attachable to a side rail of an operating table to support the distraction system on the table; a second member releasably engagable with the first member and releasably attachable to the distraction system to angularly position the distraction system with respect to the table; and a first high- friction surface disposed on one of the first or second members that frictionally contacts the other member to fix the distraction system to the table in an infinite number of angular positions with respect to the table.

2. The improved clamp assembly of claim 1 further comprising a resilient washer disposed opposite the first high-friction surface.

3. The improved clamp assembly of claim 2 wherein the washer is made of a thermoplastic material.

4. The improved clamp assembly of claim 1 further comprising a second high- friction surface located on the other of the first or second members and frictionally engagable with the first first-friction surface.

5. The improved clamp assembly of claim 4 further comprising a resilient washer disposed over one of the first or second high-friction surfaces and engagable with the other of the high-friction surfaces.

6. The improved clamp assembly of claim 5 wherein the washer is made of a thermoplastic material.

7. The clamp assembly of claim 6 wherein the washer is formed of a thermoplastic material selected from the group consisting of: Teflon, Viton, Torlon, and Delrin.

8. The improved clamp assembly of claim 2 wherein the clamp assembly is formed entirely of a rigid, non-metal material.

9. The improved clamp assembly of claim 8 wherein the clamp assembly is formed of a rigid thermoplastic material.

10. The clamp assembly of claim 9 wherein the thermoplastic material forming the clamp assembly is a polyaryletherketone.

11. The clamp assembly of claim 8 wherein the clamp assembly is formed of a composite material.

12. The clamp assembly of claim 11 wherein the clamp assembly is formed of a carbon fiber composite.

13. An improved adjustable clamp assembly for use with a non-invasive distraction system for ankle joint arthroscopy, the clamp assembly comprising: a base member releasably attachable to a side rail of an operating table to support the distraction system on the operating table, the base member including an opening extending therethrough; and a clamp head releasably attachable to the distraction system that is used to angularly position the distraction system with respect to the table; and a first high-friction surface located at one end of the clamp head adjacent the base, the first surface releasably engaging the base about the opening to securely fix the clamp head and the distraction system to the base member in an infinite number of angular positions with respect to the base member and the table.

14. The improved clamp assembly of claim 13 further comprising a resilient washer disposed on the base about the opening and engagable with the first high-friction surface on the clamp head.

15. The improved clamp assembly of claim 14 wherein the resilient washer is formed of a thermoplastic material.

16. The improved clamp assembly of claim 13 wherein the base further comprises a second high-friction surface located around the opening in the base and engagable with the first high-friction surface on the clamp head.

17. The improved clamp assembly of claim 16 further comprising a resilient washer disposed on the base around the opening over the second high- friction surface.

18. The improved clamp assembly of claim 13 wherein the first and second high- friction surfaces are formed of blunted, angular teeth.

19. The improved clamp assembly of claim 18 wherein the blunted teeth are approximately one (1) millimeter in length.

20. The improved clamp assembly of claim 13 wherein the clamp assembly is formed entirely of a non-metal material.

21. The improved clamp assembly of claim 20 wherein the clamp assembly is formed of a composite material.

22. The improved clamp assembly of claim 20 wherein the clamp assembly is formed of a thermoplastic material.

23. An improved clamp assembly for use with a non-invasive distraction system for ankle joint arthroscopy, the distraction system including a leg holder adapted to adjustably support the leg of the patient posteriorly of the knee joint to maintain the leg in a selected position between slightly flexed and acutely flexed, the leg holder attached directly to one edge of an operating table below the knee and including means of adjusting the height of the knee joint above the table and for pivoting the leg holder in each of three mutually perpendicular planes, a distraction means including an elongate body having an axially adjustable length and having first and second ends, the first end adapted to be attached to the foot of the patient, and a manually operable lever arm having one end attached to the clamp assembly and an opposite end attached to the second end of the elongate body, and a means for adjusting the length of the elongate body to vary the initial level of ankle joint distraction, the clamp assembly comprising: a base releasably secured to a side rail of the operating table and including a housing opening disposed perpendicularly to the side rail of the table; a resilient washer extending around the opening on an exterior face of the base; a generally cylindrical housing rotatably positionable within the housing opening in the base, the housing including a lever arm channel extending through the housing that receives the end of the lever arm opposite the elongate body and a threaded bore at one end; a generally cylindrical clamp sleeve disposed around the housing, the clamp sleeve including a pair of lever arm openings located on opposite sides of the sleeve and alignable with the lever arm channel, and a first knurled surface at one end releasably engagable with the base around the housing opening; and a securing means threadably engaged with the threaded bore in the cylindrical housing for releasably engaging the lever arm within the housing and the clamp sleeve, and releasably engaging the knurled surface on the clamp sleeve with the base to retain the distraction system in the desired angular position.

24. The improved clamp assembly of claim 23 wherein the base further comprises a second knurled surface extending around the opening on the base.

25. The improved clamp assembly of claim 23 further comprising a resilient washer secured to and extending around the housing opening on the base.

26. The improved clamp assembly of claim 25 wherein the lever arm is formed of a non-metal material.

27. The improved clamp assembly of claim 25 wherein the lever arm is formed of a thermoplastic material.

28. The improved clamp assembly of claim 25 wherein the lever arm is hollow.