Expandable surgical implants and methods of using them

Details Expandable surgical implants and methods of using them Expandable surgical implants and methods of using them

2001-10-05

2003-12-23

Winakur, Eric F. (Department: 3736)

Surgery

Body inserted urinary or colonic incontinent device or...

Implanted

C606S151000

Reexamination Certificate

active

06666817

ABSTRACT:

TECHNICAL FIELD
This invention generally relates to expandable surgical implants and methods of using such expandable surgical implants.
BACKGROUND INFORMATION
Numerous medical disease conditions that result from prolapse of internal organs and/or anatomical structures may be treated by providing support to the area of prolapse with a surgical implant such as a sling, a patch, or a mesh. Such implants are useful to treat, for example, stress urinary incontinence in female patients.
Various physiological conditions cause urinary incontinence in women. Stress urinary incontinence generally is caused by two conditions that occur independently or in combination, Intrinsic Sphincter Deficiency (ISD) and Bladderneck Hypermobility. ISD is a condition where the urethral sphincter valves fail to coapt properly. When functioning properly, the urethral sphincter muscles relax to enable the patient to void, and the sphincter muscles are otherwise constricted to retain urine. ISD may cause urine to leak out of the urethra during straining activities. Hypermobility is a condition where the pelvic floor is weakened or damaged causing the bladder neck and proximal urethra to descend in response to increases in intra-abdominal pressure. When intra-abdominal pressure increases (due, for example, to strain resulting from coughing), the hypermobility condition may cause urine leakage. Some women suffer from a combination of ISD and hypermobility.
The methods for treating stress urinary incontinence include placing an implant to provide support, elevation, or a “back stop” to the bladder neck and proximal urethra. Providing support to the bladder neck and proximal urethra maintains the urethra in the normal anatomical position, elevation places the urethra above the normal anatomical position, and the “back stop” prevents descent according to the so-called hammock theory.
One problem encountered following surgical intervention using an implant such as a sling or a patch to treat urinary incontinence is urinary retention resulting from excessive tension applied to the urethra. Overtensioning may also cause pressure necrosis and/or urethral erosion. One approach to alleviate these problems entails stretching the implant by inserting a catheter into the urethra and applying downward force. This procedure is imprecise and is contraindicated for patients with ISD as it may further damage the urethral sphincter. Another more invasive approach entails surgically removing the implant. Removal of such a surgical implant, which may require dissection, may cause irreparable damage to an already weakened or damaged pelvic floor. Accordingly, there is a need in the surgical arts for a surgical implant that may be expanded while positioned in the body. There is a further need for a precise and minimally invasive surgical method for expanding a surgical implant after it has been placed in the body.
SUMMARY OF THE INVENTION
It is an object of the invention to allow for expansion of a surgical implant while the implant is positioned in a body. Thus, the present invention provides for a surgical implant that may be expanded one or more times after being placed in the body, thereby providing a physician with the ability to loosen a surgical implant that was over-tensioned when placed by the surgeon and/or has become over-tensioned because of changes in the patient's anatomy. Thus, the expandable implant of the invention may be used, for example, in a suburethral sling procedure to treat female urinary incontinence by stabilizing the urethra, and later expanded if the patient suffers from urinary retention resulting from anatomical changes such as, for example, weight gain and/or pregnancy.
In one aspect, an expandable surgical implant having the features of the present invention may comprise a length of biocompatible material having at least one expansion loop positioned along the length of the biocompatible material and to one side of the center of the length (i.e., the central perpendicular axis of the implant).
In some embodiments, the expandable surgical implant may comprise an equal number of expansion loops that are positioned on either side of the central perpendicular axis; for example, the expandable surgical implant may comprise two, four, or six expansion loops positioned along the length of the biocompatible material and lateral to the central perpendicular axis. The expansion loops may each comprise at least one pair of control element attachment sites and at least one control element, such as a fastener, which is used to control the timing and degree of expansion. The pair of control element sites may be positioned on one side of the central perpendicular axis. The control elements may be attached to the control element sites and cinched so that the control element sites into are drawn into close proximity, thereby shortening the implant and facilitating its later expansion. In some preferred embodiments, a first control element site is positioned a distance ranging from 3-20 mm lateral to the central perpendicular axis of the length of biocompatible material and a second control element site is positioned a distance ranging from 3-12 mm further from the central perpendicular axis than the first control element. In particularly preferred embodiments, the second control element site is positioned a distance of about 5 mm further from the central perpendicular axis than the first control element site.
In some embodiments, the control element is a fastener such as a monofilament suture, a multifilament suture, an elongate length of biocompatible material, or a surgical staple. The control element attachment sites maybe reinforced to add resiliency to the implant at the expansion loop site or sites; for example, the control attachment site may be reinforced with an eyelet or an additional layer of biocompatible material.
In some embodiments, the control element is radio-opaque to facilitate indirect visualization of the control element site by a physician using the expandable surgical implant. When the control element is radio-opaque, it may be visualized using an instrument such as a fluoroscope. To facilitate direct visualization, the control element may a different color than the biocompatible material. Such direct and/or indirect visualization is particularly useful when expanding the surgical implant of the invention following implantation.
The control element may comprise bioabsorbable material so that it dissolves without physician intervention to thereby permit the implant to expand at the predetermined time. In alternative embodiments the control element is adapted to decompose upon application of external stimuli, thus permitting a physician to expand the implant at any desired time. For example, the control element may be adapted to decompose upon exposure to a localized low energy source or a chemical agent. The localized low energy may be in the form of, for example, ultrasonic waves, radio waves, microwaves, and ultraviolet radiation. The expandable surgical implant may comprise multiple expansion loops associated with control elements adapted to decompose upon the application of separate external stimuli. In such embodiments, the expandable surgical implant may be expanded multiple times by applying multiple stimuli (e.g., different forms or intensities of energy) that decompose different control elements. For example, the expandable surgical implant may be expanded a first time by applying one stimulus that decomposes a first control element and, possibly, a second control element, and subsequently expanded further by applying a separate stimulus that decomposes a third control element and, possibly, a fourth control element.
In some embodiments, the expandable loop comprises multiple layers of biocompatible material of unequal length. The layers of biocompatible material may, for example, be stacked in increasing length. In preferred embodiments, each layer of biocompatible material is about 2 mm to about 10 mm shorter than the adjacent longer layer in the stack of biocompatible mate

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