Pressure Reduction Effects of Subdermal Silicone Block Gel Particle Implantation:A Preliminary Study

G reyhounds are subject to the development of painful digital pad lesions. These lesions have the appearance of a fibrous scar tissue and have been termed corns.^1–3 In essence, they are callus-like lesions. There are several theories as to the cause of these lesions. One theory is that cuts or punctures result in scar tissue accumulation.^2,3 Related to this is the theory of the presence of a small foreign body in the pad. This results in accumulation of scar tissue at the lesion site, ending in a thickened hard corn as the body attempts to isolate the foreign body.³ A second theory as to the cause of the callus-like lesion is a papilloma viral infection.^2,3 However, the pressure and abrasion of walking prevents the papilloma from growing on the pad surface. The result is that the lesion is pressed into deeper pad layers forming a white flat circular painful area, i.e., corn.² A third theory on the etiology of corns is that chronic low-grade pressure on the digital pad skin results in a callus lesion (corn). It is hypothesized that sparsity of body adipose tissue, characteristic of greyhounds, is also present in the pads. Thus, in comparison to other breeds of dogs, there is relatively less fibroadipose tissue in greyhound pads. As a result, the distal interphalangeal articulation is in closer apposition to pad skin. When the dog ambulates, chronic low-grade pressure on the pad skin causes a callus lesion to form.³ This would be similar to the etiology of callus/corn formation that occurs on human feet, especially in the patient with diabetes. In one author’s (SFS) experience, the last theory is most likely the case for the majority of digital pad calluses seen in greyhounds based on several factors. First, surgical removal of the callus generally results in the pad healing and alleviates signs of pain. However, within two to three months, the condition recurs, suggesting persistence of the underlying cause, i.e., chronic low-grade pressure on the pad. In addition, recurrence of the lesion is not associated with scar tissue forming from a puncture or laceration. Second, histologic examination of corns that have been removed has not revealed the presence of foreign bodies. Even if foreign bodies were present but missed on tissue sectioning, their removal should preclude recurrence of the condition. Third, electron microscopic examination of the corns that have been removed has not revealed the presence of a papilloma virus. Based on experience, the corns/calluses of greyhounds have some characteristics similar to the plantar foot calluses on humans with diabetes, with pressure being a significant factor in the etiology. Thus, an approach to alleviating the problem of digital pad calluses is reduction of digital pressure. Humans. Plantar pressure is a significant problem in humans with diabetes. It has been reported that one in five of all hospital admissions of patients with diabetes is related to foot lesions.^4,5 In addition, diabetes-related foot problems are the reason for more than 50,000 lower-extremity amputations per year in the United States.⁶ These amputations are the result of a nonhealing necrotic diabetic foot ulcer. A nonhealing foot ulcer precedes approximately 85 percent of all lower-limb amputations per year in the United States.⁷ With diabetic neuropathy, there is a cascade of events that can lead to plantar calluses and ulcers. The insensitive foot is prone to damage from otherwise physiologic or abnormal stresses, such as elevated plantar pressure due to loss of compensentory protective mechanisms.⁸ In addition to these abnormalities, excessive force directed through a bony prominence at rest or during prolonged activity diminishes the protective subcutaneous adipose tissue on the plantar surface of the foot, making skin vulnerable to breakdown.^9–12 The increased pressure on foot tissue commonly leads to ulcer or callus formation in these patients with diabetes.^5,8,13–19 Diabetic foot calluses may act as a hard foreign body to place high vertical pressure and shear stress on underlying tissue. The result is underlying ulceration.^5,8,14,19 Elevated pressure in the form of calluses has been associated with a 77-fold increased risk of ulceration;²⁰ thus, a callus should be recognized as a high-risk factor for foot ulceration.¹⁷ In summary, foot calluses and ulcers are extensive and expensive problems among the diabetic population. There are several risk factors that predispose to diabetic foot ulceration. These include somatic and sympathetic neuropathy, high foot pressures, callus formation, foot deformities, and peripheral vascular disease.²¹ One approach to alleviating the problem of plantar calluses and ulcers is reduction of plantar pressure. Subdermal padding. One approach to providing plantar pressure relief/padding in humans is the subdermal injection of fluid/liquid silicone.^9,21–27 The silicone induces a relatively stable soft tissue prosthesis between the skin and underlying bone and reduces the frequency of insensitive ulcer recurrence in the foot. Reports of collagen disease manifestation and alleged arthritis-like symptoms that have followed silicone gel-filled breast implants have not been noted with small amounts of medical-grade fluid used in any foot-injected patient.⁹ An adverse response to liquid silicone injection is fluid drift.²⁵ However, regardless of fluid migration, in most patients, the originally injected calluses remained improved or resolved. When considering the inordinate forces applied to the feet, it has been stated that it may be impossible to prevent migration in every case.²⁵ Twenty-four months after six injections of 0.2mL of liquid silicone, it has been reported that cushioning properties are reduced.²⁷ Even in a relatively light greyhound (60 lbs.), compared to a human, one author (SFS) has noted migration of injected liquid silicone from under the distal interphalangeal joint on necropsy examination. For maximum efficacy, the subdermal padding material should remain under pressure points. Purpose Because liquid forms of silicone used in breast implants have resulted in considerable controversy regarding their potential for causing secondary reactions, another form of silicone was evaluated for its efficacy in providing subdermal padding. A silicone block gel material (Firm Silicone Gel, Implantech Assoc., Inc., Ventura, California) is described as a “firm” silicone gel. Although it is described as firm, it is soft and has cushioning gel-like properties. The purpose of this study was to obtain preliminary data to evaluate the efficacy of small particles of silicone block gel in reducing pressure on digital pads of dogs. The hypothesis was that when silicone block gel particles (SBGP) are placed under a distal interphalangeal joint and the paw is offloaded for a period of time, fibrous connective tissue will grow around individual particles of the silicone block gel to stabilize and hold them in place to prevent their migration, thus serving as stable padding for the area. This design would simulate the natural architecture of the subdermal fibroadipose tissue of the digit, with the silicone particles replacing the adipose tissue to provide cushioning. Materials and Methods All animal procedures were approved by the Auburn University Institutional Animal Care and Use Committee (IACUC). Twelve hound-type dogs of both sexes and weighing ~60 pounds were used in this study. The dogs were divided into four groups of three dogs each—Treatment and Control Group I and Treatment and Control Group II. Preoperative ground contact pad pressure analysis. Pressure data were collected on control and treated dogs by affixing a force-sensing resistor (Model 400, Interlink Electronics, Camarillo, California) to the center of the ground surface of each weight-bearing paw pad on the right forepaw. The resistors were thin polymer film devices that respond to applied surface force by decreasing electrical resistance. Each force-sensing resistor had an active area of 5mm and was fitted with electrical leads and microconnectors. When assembled, the microconnectors were supported by a thin adhesive tape strip. A 12-cm length of stranded, 24-gauge, insulated wire (Southern Electronics Corp., Opelika, Alabama) was soldered to the electrical tabs of each resistor. A male pin connector was soldered to the other end of the wire. Individual pressure calibration curves were established for each resistor before use, and their function was checked against the curves after use. Prior to affixing the sensors, the pads were wiped clean with isopropanol and air dried. A thin film of cyanoacrylate adhesive (Duro, Super Glue®, Loctite Corp., North American Group, Rock Hill, Connecticut) was applied to the pads and allowed to dry before taping a sensor to each pad. A thin adhesive tape (Hypafix®, Smith & Nephew, Inc., Largo, Florida) patch was used to hold the sensors in place. The multiple electrical leads were then lightly taped to the caudal surface of the limb. Connection to a microcomputer was completed by a four-pair, stranded, 24 AWG (American Wire Gage) networking cable (Inmac, Gibbsboro, New Jersey). The female sockets of computer light-emitting diodes were used as plugs on the networking cable to receive the male pin connectors. Each force-sensing resistor was supplied with a current of 1.57 milliamperes (mA) at 5 volts direct current (VDC). Output signals were delivered to the analog/digital conversion board of the computer. The oscilloscope feature of a kinematic data collection software program (PEAK 5®, Peak Performance Technologies, Inc., Englewood, Colorado) was used to monitor data during collection and create a store of data. With the dog in a normal standing position, pressures were measured on each pad over a seven-second period for three measurements. Silicone block gel particle (SBGP) preparation. Silicone block gel (Firm Silicone Gel, Implantech Assoc., Inc., Ventura, California) was thoroughly washed in chlorhexidine surgical scrub solution (Nolvasan Scrub®, Ft. Dodge Animal Health, Ft. Dodge, Iowa) and rinsed with water. This procedure was repeated six times. The silicone block gel was then manually cut/minced into small particles (~1–2mm diameter) with a scalpel blade (Figure 1). The silicone block gel particles (SBGP) were placed in a small glass beaker, sealed, and sterilized by autoclaving. At the time of implantation, the SBGP were manually placed in a 3mL syringe barrel, and the plunger was replaced in the syringe aseptically. Operative procedures. Treatment Group I (n=3). Following induction and maintenance of a surgical plane of anesthesia, the right forelimb of each of three large hound-type dogs was prepared for aseptic surgery from the tips of the nails to the midradial level. After applying a 1/2 inch diameter Penrose drain tourniquet at the proximal metacarpal area, a small stab incision was made with a number 11 scalpel blade at the juncture of the pad and haired skin on the abaxial surface of the third digit. The incision was half way between the cranial and caudal aspects of the pad. A specialized narrow, thin scalpel blade (Beaver blade) was inserted through the incision into the fibroadipose tissue between the dermis and distal interphalangeal joint. It was advanced in all directions under the pad in a sweeping motion to cut and loosen the fibroadipose tissue under the pad. A small curette was inserted into the area and manipulated to further loosen the fibroadipose tissue. The pad skin was loose, and there appeared to be space under it. The subdermal area was flushed with sterile physiologic saline, and digital pressure was applied for approximately three minutes to attain hemostasis. A purse string suture of 3-0 monofilament polypropylene (Prolene®, Ethicon, Somerville, New Jersey) was placed around the stab incision, and one throw was placed in the suture, but it was not tied. The tip of the 3mL syringe containing SBGP was inserted into the incision. A special injection apparatus was placed on the syringe to provide a mechanical advantage for injecting. With the purse string suture tightened around the syringe tip, 0.5mL of SBGP was injected under the pad. The suture was tightened as the syringe tip was withdrawn. The final throws were placed on the suture to provide a secure closure of the stab incision. The hair was clipped, and the skin at the base of the right ear was prepared for aseptic surgery. A 1cm long skin incision was made in the skin, and the skin was undermined for approximately 1cm on one side of the incision. One half mL of SBGP was placed under the undermined skin. The incision was closed with simple interrupted sutures of 3-0 polypropylene. A simple interrupted suture of 5-0 stainless steel (Stainless Steel, Ethicon, Somerville, New Jersey) was placed in the skin over the implanted SBGP as a marker to assist in finding the SBGP in three months. This was done to determine if there was any difference in response to SBGP placed under weight-bearing skin (pad) and nonweight-bearing skin (near the ear). Control Group I (n=3). The procedures for this group were the same as for Treatment Group I; however, no SBGP were injected under the pad or at the base of the right ear. Treatment Group II (n=3). The procedures for this group were the same as those for Treatment Group I with two exceptions. First, after incising the fibroadipose tissue, a pair of fine alligator biopsy forceps were inserted into the fibroadipose tissue area. Bites were taken from the loosened tissue, removed, and collected. When as much fibroadipose tissue as possible had been removed, the subdermal area was flushed with sterile physiologic saline. A small amount of fibroadipose tissue remained. The pieces of fibroadipose tissue removed from the subdermal area were coalesced and placed in the barrel of a 3mL syringe to measure the amount of tissue removed. Second, when the SBGP were injected under the pad on two dogs, an amount equal to the amount of fibroadipose tissue removed was injected in the subdermal area (Dog 1, 0.5mL; Dog 2, 0.3mL; Dog 3, 0.3mL). Control Group II (n=3). The procedures were the same as for Treatment Group II; however, no SBGP were injected under the pad or at the base of the right ear. Postoperative procedures. Radiology and ultrasonography. Immediately following SBGP injection, while the dogs were still under anesthesia, radiographs and ultrasonographic scans were made to demonstrate the location of the SBGP related to the distal interphalangeal joint on treated dogs. Lateral and dorsopalmar radiographs were made of the injected right front third digit. Following radiography, ultrasonography was performed of the operated paw and the ear base using an ultrasound machine with a broadband 12-5 MHz linear array transducer (ATL HDI 5000 ultrasound machine, ATL Ultrasound, Bothell, Washington). Bandaging and splinting (offloading). After radiography and ultrasonography, the right forelimb of each dog was placed in a “clam-shell” splint. Segments of cast padding were placed in all interdigital and interpad areas. A one-inch-wide strip of tape approximately six inches long was applied to both the dorsal and palmar surface of the paw, parallel to the long axis of the limb and extending approximately four inches beyond the paw. The strips were adhered together beyond the end of the paw. A doughnut-type cast padding pad was placed over the carpal pad to prevent pressure injury from the splints. Absorbent secondary bandage wrap was wrapped around the limb from the digits to near the elbow with the adhered one-inch strips folded back into the bandage wrap. Two-inch wide adhesive tape strips were placed as the outer bandage layer. A Mason metasplint was placed on the cranial and caudal aspects of the limb with the paw cup portions facing each other and extending approximately one inch beyond the end of the bandage. These were taped in place, and the bottom of the splint was covered with strips of duct tape for water proofing purposes. The clam-shell splint/bandage placed the paw in a “toe-dancing” posture. This tended to offload the digits²⁶ to help keep pressure off of the implanted SBGP in the third digit to allow time for it to heal in place. Three-week, five-week, and three-month aftercare and procedures. During the three-week postoperative period, the dogs were housed in combination indoor-outdoor pen/run facilities. They had free access to move back and forth between the indoor and outdoor facilities. They had access to water ad libitum and were fed a balanced diet twice daily. The clam-shell bandage splints were changed daily for the first two postoperative days. Following this, they were generally changed every two to three days unless they became wet or soiled or the dog had damaged them by chewing. At three weeks postoperatively, ground contact pressure, radiographic, and ultrasonographic analyses were performed as previously described. The procedures were performed after the clam-shell splint/bandage had been removed and the dogs had been allowed to walk one day without the splint/bandage. Between three and five weeks, and five weeks and three months, the dogs were housed as previously described. They had no paw support during this time and were observed during this time with periodic examinations of the operated paw. At five weeks and three months postoperatively, ground contact pressure, radiographic, and ultrasonographic analyses were performed as previously described. Subjective observations. During the three-month postoperative period, the dogs were observed and note was made of any indication of SBGP migration and appearance of any lesions on the operated pad or other pads on the right forepaw. Biopsy/surgical exploration. At three months, biopsies and surgical exploration were performed. After general anesthesia and aseptic surgical preparation of the involved paw and ear area, where applicable, a dermal biopsy punch was used to obtain a biopsy of the pad skin and underlying subdermal tissue and any SBGP contained in this tissue. The biopsy was taken in the center of the pad to the depth of the distal interphalangeal joint. The skin, subdermal tissue, and SBGP were placed in 10-percent buffered formalin (pH 7). On treated dogs, digital pressure was placed on the pad skin surrounding the biopsy defect to ascertain if any SBGP could be expressed from the tissues. The biopsy defect was sutured with two far-near–near-far sutures of 3-0 polypropylene. At other points around the digital pad where it was suspected that SBGP might have migrated, incisions or a skin biopsy hole were made in the skin to explore these areas. If SBGP were found, it was taken along with surrounding connective tissue (capsule) and placed in 10-percent buffered formalin at pH 7 for histopathologic examination. The incisions were sutured with simple interrupted sutures of 3-0 polypropylene. The area under the right ear was clipped and prepared for aseptic surgery. An incision was made adjacent to the stainless steel suture that had been placed as a marker to locate the implanted SBGP. The SBGP and any surrounding connective tissue (capsule) were taken and placed in 10-percent buffered formalin (pH 7) for histopathologic evaluation. The incisions were sutured closed. To allow the third digital pad and adjacent biopsy sites to heal, paw bandages were placed on the right forepaw. Bandages were changed every other day, unless they became soiled or wet. Then they were changed daily. Bandaging was continued for two weeks or until the wounds were believed to be healed sufficiently to discontinue bandaging. Histopathologic procedures. After fixation in 10-percent buffered formalin (pH 7), the skin samples were processed routinely for histopathology, stained with hematoxylin and eosin, and examined by light microscopy. The parameters used for evaluation were relative density of neutrophils, lymphocytes, plasma cells, macrophages, eosinophils, and mast cells. Necrosis, fibroblast proliferation, neovascularization, edema, acute hemorrhage, chronic hemorrhage, and collagen density were also used for evaluation. Each of the parameters was scored from 0 to 3, with 0=normal, 1=mild increase, 2=moderate increase, 3=marked increase. Sparsely scattered neutrophils, lymphocytes, plasma cells, macrophages, eosinophils and mast cells arranged in a random fashion in the tissue were considered normal. Localization of 3 to 10, 11 to 30, or 31 or more cells in the tissue per 400x magnification field was considered a mild, moderate, or marked increase, respectively. Sparsely scattered necrotic cell debris, extravasated erythrocytes (indicative of acute hemorrhage), and hemosiderin-laden macrophages (indicative of chronic hemorrhage) were considered a mild increase for each of these parameters. Focal dense accumulations of each of these components in the tissue were considered a moderate increase. Extensive tissue necrosis, massive hemorrhage to involve the surrounding tissue, and the presence of greater than 30 hemosiderin-laden macrophages per 400x magnification field were considered a marked increase for each of these parameters, respectively. Fibroblasts and collagen organized in a random pattern, typical of normal tissue, were considered normal. Localization of fibroblasts and capillary buds in the tissue in numbers of 3 to 10, 11 to 30, and greater than 31 per x400 magnification field was considered mild, moderate, and a marked increase, respectively, for fibroblast proliferation and neovascularization. Scant collagen bundles slightly separating the fibroblasts in the tissues were considered a mild increase in collagen density. Somewhat dense accumulations of collagen between fibroblasts in the tissues were considered a moderate increase in collagen density. Extensive separation of fibroblasts by abundant collagen was considered a marked increase in collagen density. Slight separation of cells and collagen from one another in the tissue by nonstaining or poorly staining acellular material was considered mild edema. Separation of 3–50mm by this acellular material was considered moderate edema, while separation of greater than 50mm was considered marked edema. Observations were made of the presence SBGP, noting whether the particles were phagocytosed or nonphagocytosed and present as individual particles surrounded by fibroblasts. Samples were evaluated for one parameter before proceeding to the next, which allowed for more accurate comparison of individual parameters. Results Subjective observations. During the three-week postoperative period while the dogs had the clam-shell splints in place, they were tolerated well. However, the splints came off of one dog on Day 1 and 17, and the dog was able to bear weight on the paw before the splint could be replaced. None of the dogs showed any signs of pain or discomfort at any time during the study. By the end of the three-month observation period, all six dogs of the two treatment groups showed signs of migration of the SBGP in the form of subcutaneous enlargements on either the axial or abaxial surfaces of the third digit adjacent to the pad. On two dogs in Treatment Group II, these enlargements were very small. On two Treatment Group I dogs and two Treatment Group II dogs, the enlargements appeared while the offloading clam-shell splints were still in place. In the two Treatment Group II dogs, the enlargements at this early time were in the form of a more turgid feel to the adjacent digital web fold. Despite the enlargements adjacent to the pads in Treatment Group I, the third digital pads of all three dogs showed evidence of SBGP under the pad during the postoperative observation period. The pads either appeared more distended/larger or felt more cushioned than adjacent pads. No significant lesions were observed on the third digital pads or other pads of any of the treated or control dogs. Exploratory surgery subjective observations. In Treatment Group I, two dogs had isolated SBGP within the subdermal fibroadipose tissue (Figure 2) with one of these dogs having a small mass of SBGP in this tissue at the point where the biopsy was taken. However, in the third dog, SBGP were not found in the pad subdermal fibroadipose tissue. In all three dogs, the subdermal enlargements adjacent to the third digital pad were masses of SBGP surrounded by a connective tissue capsule with no evidence of connective tissue ingrowth between particles, because they were easily separated. The SBGP that were placed at the base of the right ear of each dog appeared like the masses found adjacent to the third digital pad, i.e., a mass of SBGP surrounded by a fibrous capsule with no ingrowth of connective tissue between particles. In Treatment Group II, one dog had isolated SBGP surrounded by connective tissue in the pad fibroadipose tissue. Only a single particle was found in tissue adjacent to the pad of this dog. The other two dogs of the group had no SBGP found in the pad fibroadipose tissue. In one of these dogs, only a single particle was found in tissue adjacent to the pad. In the other dog, a mass of SBGP surrounded by a connective tissue capsule with no connective tissue ingrowth between individual particles was found adjacent to the third digital pad. Only one dog of this group had a mass of SBGP surrounded by a fibrous capsule at the base of the right ear (Table 1). Both control groups had only subdermal fibroadipose tissue underlying the pad skin. Histopathologic observations. Although 13 parameters were evaluated in this study, seven were selected to give an overview of the effects of SBGP on the inflammatory and repair stages of healing. When considering the parameters that are indicative of an inflammatory reaction, i.e., neutrophils, lymphocytes, macrophages, and necrosis, the pads that received SBGP tended to have higher scores than their corresponding controls. This was true of both treatment groups, especially Treatment Group I (Table 2). The pattern of elevated scores also held true for tissues adjacent to the pads where SBGP had migrated in Treatment Group I. The mean scores for Treatment Group II for adjacent tissues were inconclusive, because one dog had high scores due to a histopathologic abscess in the area, and a second dog had very low scores (Table 3). Mean scores for these parameters were similarly elevated in SBGP-implanted tissues at the base of the ear (Table 4). When histologic parameters associated with tissue repair are considered for the pads, i.e., fibroblast proliferation, neovascularization, and collagen density, the mean scores of the treatment groups and control groups were similar. Because one of the main factors in the hypothesis of the study was the ingrowth of connective tissue around individual SBGP, the results of fibroblast ingrowth and collagen density were of particular interest, since fibroblasts produce the collagen of the connective tissue. Within the pads, the mean scores of both of these factors were basically the same for treatment and control groups (Table 2). The mean scores for these two parameters for SBGP at the base of the ear were lower than the mean scores for SBGP in the pad (Tables 2 and 4). The histologic samples from the pads of all dogs receiving SBGP contained phagocytosed and nonphagocytosed (or free) SBGP. Nonphagocytosed SBGP was characterized by angular empty spaces that contained SBGP prior to tissue processing. These empty spaces were surrounded by mild to moderate fibrosis (Figure 3). The large masses of SBGP that were found adjacent to the pads as a result of migration and the masses of SBGP found at the bases of the ears had limited fibroblast ingrowth into the masses. It was believed that the fibroblasts and the resultant collagen they produced were mainly associated with the fibrous connective tissue capsule that surrounded the masses. Some of these fibrous capsules around SBGP masses were up to 15 fibroblast layers thick. Radiographic and ultrasonographic observations. These results will be presented for only treated dogs, because they showed the information of interest. Radiographic and ultrasonographic results were the same for both treatment groups. The SBGP were radiopaque and could be clearly seen on radiographs. On ultrasonography, the SBGP created a wide hyperechoic reverberation artifact (“dirty” acoustic shadow) that tended to obscure underlying tissues. During the course of the study, the SBGP tended to migrate in the implanted digits. Implants at the base of the ear produced a distinct reverberation artifact in all dogs up to five weeks postoperatively. However, at three months, the implant was difficult to find on three dogs but was readily found on the other three dogs. These findings at the base of the ear coincided with findings at exploratory surgery in that the SBGP could not be found on two dogs; however, they were located on the third dog. In general, the radiographic and ultrasonographic findings correlated with subjective observations during aftercare and the exploratory surgery observations, i.e., SBGP migration. Ground contact pad pressure observations. The consistency of preoperative ground contact pad pressure measurements for individual dogs indicated that the technique for measuring pressures was uniform throughout the study. Preoperative ground contact pressure values had the same general pattern in all 12 dogs. This pattern showed the following: 1. Pressure on digital pad 3 was considerably higher than the pressure on the other three digital pads and the metacarpal pad. Thus, it was indicated as the appropriate digit on which to perform pressure change studies. 2. Pressures on digital pads 4 and 5 were comparable. 3. Pressures on the metacarpal pad and digital pad 2 were comparable. 4. Pressures on the metacarpal pad and digital pad 2 were higher than pressures on digital pads 4 and 5 (Table 5). The pressures were measured in four groups, i.e., two treatment groups and their corresponding control groups, with pressure measurements taken on each pad for each group. Although pressures were measured preoperatively, three and five weeks and three months postoperatively, preoperative and three-month postoperative pressures are reported on digits 2, 3, and 4, because they provided the best information about pressure trends (Table 6). The results will be presented by comparing the percents decrease between preoperative pressures and the final (3 month) pressures on digital pad 3 of each treatment group with its corresponding control group, comparing this same parameter for pressures on digital pad 3 in Treatment Group I with the digital pad 3 pressures in Group II (Table 7). The effect of SBGP injection in digit 3 on percent increase/decrease in pressure in adjacent digits 2 and 4 between preoperative pressures and the final (3 month) pressures were also evaluated (Table