Fifteen-year follow-up of transplantation of a cadaveric polycystic kidney: a case report.

INTRODUCTION: Kidneys from donors affected by autosomal-dominant polycystic kidney disease (ADPKD) are in general considered unsuitable for transplantation. To the best of our knowledge, only 12 cases of ADPKD transplanted renal units have been reported in the English literature; most have only short-term follow-up. METHODS: We provide a review of these patients and share our experience with an ADPKD patient who received a 21-year-old deceased donor ADPKD-affected renal transplant and has been closely followed for 15 years. Based on the current literature, this report is the longest follow-up of a ADPKD donor transplant. RESULTS: Over the 15-year follow-up period, there have been no complications related to the ADPKD-affected donor kidney, including three kidney transplant biopsies. The graft continues to function well with the serum creatinine currently 1.2 mg/dL. Serial axial imaging has demonstrated that the cystic disease has slowly progressed in the donor renal unit, with the largest cyst having only increasing from 1.2 to 2.9 cm in diameter. Metachronous, bilateral laparoscopic nephrectomies of the native kidneys were performed owing to intractable pain from cystic enlargement. CONCLUSIONS: Normal functioning deceased donor kidneys that show signs of early ADPKD should be considered acceptable for donation in select cases. These organs provide the recipient a safe, reasonable period of graft survival and have not been shown to cause adverse effects.

Complications after a 5-year experience with laparoscopic donor nephrectomy: the Indiana University experience.

BACKGROUND: Laparoscopic donor nephrectomy (LDN) is becoming the standard of care for living donor nephrectomy. However, questions have been raised about the safety of LDN for the donor and about the potentially increased rates for ureteral complications experienced by the recipient. In this report, the authors review their 5-year experience with 253 living laparoscopic donor nephrectomies. METHODS: A retrospective chart review was performed for 253 laparoscopic live donors. Graft function and survival were compared using recipient postoperative creatinine values up to 12 months. RESULTS: The overall rate of complications in the investigated series was 10.3%. There were seven intraoperative complications (2.8%), three of which required open conversion. There were 19 postoperative complications (7.5%), three of which required reexploration for bleeding. The majority of complications were minor including 62% grade 1, 8% grade 2, 31% grade 3, and no grade 4 or 5 complications. There were no intraoperative complications in the right-sided donor group. There was a 5% complication rate for patients with a body mass index (BMI) exceeding 25. The findings showed that 11.2% of the recipients had slow graft function, and 4.4% had delayed graft function. Less than 1% of the recipients experienced ureteral stricture requiring permanent stent placement or reoperation. Overall, there was a 2% graft loss rate. CONCLUSIONS: The findings show a low rate of intraoperative and postoperative complications, most of which were minor complications. There was an increase in operative time and hospital stay in the right-sided group, but no increase in complication rate. There was no significant difference in outcome or complication rate for the overweight patients.

Laparoscopic nephrectomy in patients with end-stage renal disease and autosomal dominant polycystic kidney disease.

Autosomal dominant polycystic kidney disease (ADPKD) is often characterized by end-stage renal disease (ESRD) and problems including pain, hematuria, and infection. Open nephrectomy is curative; however, the morbidity of the procedure is considerable. Between 1995 and 1998, 11 laparoscopic nephrectomies were performed on nine symptomatic patients (five men and four women) with ESRD and ADPKD. Two patients underwent a staged bilateral laparoscopic nephrectomy. All patients presented with abdominal or flank pain and an abdominal mass. Other clinical problems included hypertension in eight patients, urinary tract infections in two patients, and gross hematuria in one patient. Seven patients were receiving long-term dialysis treatment, and two patients had undergone prior renal transplantation. Patients were evaluated for preoperative and postoperative pain, analgesic use, hospital course, and convalescence. The overall average operative time was 6.3 hours, with an average estimated blood loss of 153 mL. Eight nephrectomy specimens were removed by morcellation, and three specimens were removed intact through a 7- to 12-cm incision. The average hospital stay was 3 days, and the average time to normal activity was 5 weeks. With a mean follow-up of 31 months, all nine patients reported elimination of their preoperative pain based on a pain analogue score. Six major and two minor complications occurred, including blood transfusion, a vena cavotomy, splenic cyanosis, pulmonary embolism, clotted arteriovenous fistula, and brachial plexus injury. Incisional hernias occurred in two of the three patients who underwent open removal. One patient noted improvement, and two patients noted resolution of their hypertension postoperatively. Laparoscopic nephrectomy in patients with ADPKD and ESRD offers an effective alternative to open nephrectomy to manage renal-related pain. This procedure provides the benefits of minimal intraoperative blood loss, minimal postoperative pain, brief hospital stay, and rapid convalescence.

Percutaneous ablation of malignant liver tumor in rabbits using low radio frequency energy.

Radio frequency (RF) current has been used successfully to ablate normal human tissue. To further investigate the clinical application of this modality in tumors we studied the potential of using RF percutaneously to destroy experimental liver tumors. Thirty five outbred albino rabbits underwent liver VX2 tumor direct-implantation during open surgery. After 21 days ultrasonography was performed revealing tumor presence and size. A shielded RF needle was designed so that it could be inserted percutaneously through an introducing needle, and an electrical insulation shield covering the RF needle could be retracted to control the length of the exposed RF needle inside the tissue. Twenty two days after tumor implantation RF was applied via the aforementioned needle using a ZoMed International RF generator. In one group of rabbits the procedure was performed under direct vision during open surgery and on the other group treatment was applied percutaneously, guiding the needle by tumor palpation. Rabbits were killed 3 days later and pathology revealed 4 to 25 mm intratumoral RF induced lesions. A direct relation was found between lesion size, power and duration of RF application (At 7.5 W, r = 0.48, p = 0.032). Based on our preliminary results we may conclude that RF may have clinical application in the near future for percutaneous local tumor control in parenchymal organs.

Survey of neuromuscular injuries to the patient and surgeon during urologic laparoscopic surgery.

OBJECTIVES: Laparoscopy may be complicated by neuromuscular injuries, both to the patient and to the surgeon. We used a survey to estimate the incidence of these injuries during urologic laparoscopic surgery, to assess risk factors for these injuries, and to determine preventive measures. METHODS: A survey of neuromuscular injuries associated with laparoscopy submitted to 18 institutions in the United States was completed by 18 attending urologists from 15 institutions. RESULTS: From among a total of 1651 procedures, there were 46 neuromuscular injuries in 45 patients (2.7%), including abdominal wall neuralgia (14), extremity sensory deficit (12), extremity motor deficit (8), clinical rhabdomyolysis (6), shoulder contusion (4), and back spasm (2). Neuromuscular injuries were twice as common with upper retroperitoneal as with pelvic laparoscopy (3. 1% versus 1.5%). Among patients with neuromuscular injuries, those with rhabdomyolysis were heavier (means 91 versus 80 kg) and underwent longer procedures (means 379 versus 300 minutes), and those with motor deficits were older (means 51 versus 42 years of age). Of the surgeons, 28% and 17% reported frequent neck and shoulder pain, respectively. CONCLUSIONS: Although not common, neuromuscular injuries during laparoscopy do contribute to morbidity. Abdominal wall neuralgias, injuries to peripheral nerves, and joint or back injuries likely occur no more frequently than during open surgery, but risk of rhabdomyolysis may be increased. Positioning in a partial rather than full flank position may reduce the incidence of some injuries. Measures to reduce neuromuscular strain on the surgeon during laparoscopy should be considered.

Laparoscopic nephroureterectomy. A new standard for the surgical management of upper tract transitional cell cancer.

Laparoscopic nephroureterectomy for upper tract TCC still remains somewhat controversial. Unlike laparoscopic radical nephrectomy, which has become widely accepted, LNU is still in its earliest stages. Although there are obvious benefits for the patient who has LNU--less pulmonary complications, less postoperative discomfort, a shorter hospital stay, a better cosmetic result, and a brief convalescence--there are significant concerns. The longer operative time creates a negative financial and professional inducement to learn this technique. Operative times need to fall into the 4-hour range or less to make the procedure cost-effective. Analysis of the efficacy of laparoscopic nephroureterectomy as a curative treatment modality is important. In the short-run, LNU seems to provide similar results to open nephroureterectomy for upper TCC. Although concerns over port site seeding, bladder recurrence, and intraperitoneal seeding have been voiced, these problems have not occurred. The higher incidence of local recurrence noted in the authors' series, however, is of concern and remains an unsettled issue. Despite these local recurrences, the overall cancer survival for a given grade and stage of upper tract TCC seem to be similar to survivals recorded after open nephroureterectomy. Still, the number of LNU cases remains small, and follow-up is brief. These patients need to be monitored closely, with follow-up CT scans over the next decade. The authors believe that there are still several significant hurdles standing in the path of LNU before it can become a widely accepted procedure. Issues of cost, training, and long-term efficacy must be answered definitively. To obtain these types of data, it will be necessary to create a multi-institutional, cooperative study to obtain sufficient numbers of patients with a more than 5-year follow-up on which to base future recommendations.

Renal tuberculosis presenting as lateralizing hematuria diagnosis by ureteronephroscopy and selective upper tract urine culture.

A 48-year-old man presented with painless left lateralizing macroscopic hematuria. Ureteroscopy revealed flocculent material in the left kidney and white linear streaks on some upper pole papillae; urine culture from the left renal pelvis was positive for tuberculosis, whereas voided urine cultures were negative. Renal tuberculosis should be included in the differential diagnosis of lateralizing hematuria, especially in the absence of an obvious cause for the bleeding. Direct culture of urine from the renal pelvis may have more sensitivity than culture of voided urine in this circumstance.

Laparoscopic staging of bladder tumor: concerns about port site metastases.

Since the first laparoscopic pelvic lymph node dissection (LPLND) was performed for prostate cancer, only one case of port site metastasis has been reported, an incidence of 0.1%. On the other hand, three cases of port site metastasis have been reported after laparoscopic staging of transitional-cell carcinoma (TCC) of the bladder, a reported incidence of almost 4%. Herein, we review the circumstances of these three cases and address the potential risk factors and possible preventive measures regarding LPLND and port site metastasis in patients with TCC of the bladder.

Is laparoscopic radical nephrectomy with specimen morcellation acceptable cancer surgery?

Laparoscopic radical nephrectomy (LRN) for renal-cell carcinoma (RCF) with removal of the specimen by morcellation and suction remains controversial because precise pathologic tumor staging is lost, and there is a risk of tumor seeding. We assessed the theoretical impact of surrendering precise pathologic staging on the management of patients with low-stage RCC (T3a or less). In 22 patients who underwent open radical nephrectomy for RCC, the preoperative CT-based clinical stage was correlated with pathologic tumor staging. Possible clinical inclusion criteria for LRN were then correlated with pathologic tumor staging. When comparing clinical and pathologic staging, one patient was understaged and seven were overstaged by preoperative CT. However, if clinical stage T3a or lower was used as the inclusion criterion for LRN, 19 patients (86%) would have been so treated, none would have been underassigned, and future management would not have been compromised according to pathologic staging. Management of patients with low-stage RCC relying on clinical staging only is oncologically adequate. This would make LRN an acceptable option for this subset of patients.

The effect of patient position on intrarenal anatomy.

BACKGROUND AND OBJECTIVE: Although flexible ureteroscopes are designed with mechanisms for active and passive tip deflection, one of the major problems is the not infrequent inability to enter the lower pole calices. Accordingly, we measured the change in the lower pole infundibulopelvic (LIP) angle when the patient's position was varied (i.e., prone, supine, head down) during intravenous urography (IVU). PATIENTS AND METHODS: The LIP angle was measured in 20 right and 26 left adult kidneys during an IVU with the patient in six different positions: supine level, supine 20 degrees head down, supine 45 degrees head up, prone level, prone 20 degrees head down, and prone 45 degrees head up. None of the patients had a history of renal surgery. RESULTS: In all cases, the broadest angle of entry to the lower pole infundibulum was obtained with the patient in a prone position and 20 degrees head down. CONCLUSIONS: The LIP angle broadens when the patient lies in a prone 20 degrees head down position. This maneuver could improve the surgeon's ability to access the lower pole calices when performing flexible ureteronephroscopy.

Laparoscopic nephroureterectomy for upper tract transitional-cell cancer: technical aspects.

Standard surgical therapy for most patients with upper tract transitional-cell carcinoma (TCC) is total nephroureterectomy with excision of an ipsilateral cuff of bladder; this procedure is performed through two separate or one long abdominal incision. The laparoscopic approach has the same goals. At Washington University, our approach has been similar to the open operation in that the procedure is performed transperitoneally and a cuff of bladder is secured. Herein, our current method for laparoscopic nephroureterectomy is described and illustrated in detail. In addition, other laparoscopic techniques for performing the nephrectomy portion and handling the distal ureter are described. Overall, this technique is still evolving as laparoscopic surgeons attempt to balance the goal of a thorough nephroureterectomy with the need to make the procedure cost effective.

Laparoscopic management of retrovesical cystic disease: Washington University experience and review of the literature.

BACKGROUND AND PURPOSE: Recently, the laparoscopic approach to the management of seminal vesicle cysts has been described. This report outlines the Washington University experience and reviews the present literature to evaluate the results of the laparoscopic approach to the excision of retrovesical cysts of seminal vesicle and Müllerian origin. PATIENTS AND METHODS: The hospital and office records of three patients undergoing laparoscopic excision of seminal vesicle and Müllerian duct cyst disease between April 1993 and March 1999 were reviewed for the operative time, the estimated blood loss, total hospital stay, total analgesia required postoperatively, the time to resumption of oral intake, and the postoperative recovery. A literature search revealed two additional reports of laparoscopic management of cystic disease of the seminal vesicle, comprising only one and two patients. An additional review of the literature was performed to compare the laparoscopic procedure with the transvesical, transurethral, open transvesical, and open retrovesical approach for the management of the disease. RESULTS: For the three patients at Washington University, the operative time averaged 4 hours (range 1.8-6.1 hours), and the mean estimated blood loss was 150 mL (range 50-200 nL). The patients required a mean of 43 mg of morphine sulfate for postoperative pain control, had a mean hospital stay of 2.6 days, and resumed oral intake 5.8 hours postoperatively. In combination with the three other cases reported in the literature, the average operative time for laparoscopic retrovesical cyst excision was 2.9 hours, and the average hospital stay was 2.2 days. With an average follow-up of 17 months, all six patients had excellent resolution of their preoperative symptoms. There have been no major or minor complications or any need for further operative therapy. CONCLUSION: Laparoscopic excision of retrovesical cystic disease is an effective surgical procedure, associated with minimal postoperative morbidity, short hospitalization, and a rapid recovery for the patient.

Metabolic evaluation of stone disease patients: a practical approach.

In the last three decades, minimally invasive techniques have progressed significantly, replacing traditional open surgery as the mainstay of stone disease surgical treatment. The challenge for the next millennium remains medical prevention of calcium urolithiasis, a field where less dramatic progress has been achieved during the same period of time. The purpose of this article is to provide the practicing urologist with current practical guidelines for the assessment and management of calcium urolithiasis patients. The recommendations are based on the latest available information regarding the pathogenesis, medical treatment options, and decision-making rationale when managing these challenging patients. Every urolithiasis patient should undergo a basic evaluation, which is considered the minimal essential diagnostic work-up, in order to rule out obvious, treatable systemic causes of urinary stone disease. All patients should be advised about conservative nonspecific preventive measures. High-risk stone patients should have a more extensive metabolic evaluation based on two 24-hour urine samples. Treatment protocols for each patient are tailored individually according to the metabolic evaluation findings.

Endoscopic creation of reflux in the pig.

Vesicoureteral reflux (VUR) in the animal model for experimental purposes can be created either by open transvesical or endoscopic techniques. The concept of reflux creation is the same for both techniques: incision of the roof of the intramural portion of the ureter at the 12 o'clock position. The open method has the disadvantages of requiring a cystotomy and a lengthy healing period prior to initiating a study, thereby incurring additional expense and the problem of introducing several confounding factors. The open method is unreliable because of the resolution of reflux over time. Herein, we present a simple transurethral endoscopic technique for creating VUR in pigs. This technique was successful in producing persistent Grade II or III reflux in 94% of the incised ureters.

Laparoscopic ureteroureterostomy using vascular closure staples in porcine model.

The greatest difficulty in performing a laparoscopic pyeloplasty is the suturing of the ureteropelvic junction. The purpose of this study was to evaluate the use of nonperforating titanium vascular closure staple (VCS) clips to perform in laparoscopic ureteroureterostomy in the porcine model. Six female minipigs underwent laparoscopic transection of one of the proximal ureters at the level of the lower pole of the kidney. Ureteroureterostomy was then performed using the titanium VCS clips. The animals were evaluated at 6 and 12 weeks postureteroureterostomy with retrograde pyelography and differential creatinine clearances. At 12 weeks, the animals were euthanized, and the area of ureteroureterostomy was examined grossly and histopathologically. The technique for laparoscopic vascular clipping of the ureteroureterostomy proved to be fast and effective. Follow-up indicated that the method was successful in producing a functionally patent anastomosis. No encrustation, stone formation, or intraluminal clip was noted in any of the ureters or kidneys undergoing the ureteroureterostomy. The area of the ureteroureterostomy showed minimal fibrosis and inflammation on histopathologic examination. In this animal study, the nonperforating titanium clips facilitated the performance of a laparoscopic ureteroureterostomy.

Endopyelotomy for high-insertion ureteropelvic junction obstruction.

We assessed the results of endourologic treatment of patients with a primary ureteropelvic junction obstruction (UPJO) caused by high insertion of the ureter into the renal pelvis (HIUPJO). A total of 10 patients 15 to 76 years old with preoperatively diagnosed HIUPJO were treated. Acucise retrograde endopyelotomy was performed in eight patients and percutaneous antegrade endopyelotomy in two. A stent was left in place for an average of 5.3 weeks. The subjective success rate, based on patient questionnaire and analog pain scales, was 80% at 27 months' average follow-up. The objective success rate, based on diuretic renal scanning or Whitaker test, was 70% at 26 months' mean follow-up. Overall, 60% of the patients had both an objectively and a subjectively successful outcome. The success rate for endopyelotomy in patients with UPJO caused by high insertion is similar to that reported for endopyelotomy in patients without high insertion. High insertion is not a contraindication to endopyelotomy.

Impact of etiology of secondary ureteropelvic junction obstruction on outcome of endopyelotomy.

Endopyelotomy for secondary ureteropelvic junction obstruction (UPJO) is a highly effective procedure. However, the impact of the etiology of the obstruction on the outcome of an endopyelotomy has not been defined. Herein, we review the success rates with endopyelotomy for secondary UPJO after failure of open pyeloplasty or endopyelotomy. Thirty-five adult patients with both objective and subjective follow-up were identified retrospectively who had endopyelotomy for secondary UPJO. Twenty-four patients had failed a previous open reconstruction (23) or laparoscopic Foley Y-V plasty (1). Eleven patients had failed a prior endopyelotomy. Retrograde endopyelotomy was performed using the Acucise device in 11 patients, and antegrade endopyelotomy was performed in 24 patients. Objective follow-up was obtained with diuretic renal scintigraphy (mean 14.1 months) and subjective follow-up by analog pain scales (mean 27.8 months). Objective success was defined as no obstruction on renal scintigraphy, while subjective success was used to describe a minimum of 50% resolution of symptoms. The subjective success rate of secondary endopyelotomy in the open-pyeloplasty group was 88% v 71% in the prior endopyelotomy group (P = 0.20). The objective success rate in the failed-pyeloplasty group was 71% v 55% in the prior endopyelotomy group (P = 0.40). Endopyelotomy for secondary UPJO has a good success rate. Success rates tend to be higher in patients who have failed an open pyeloplasty; however, a statistically significant difference was not seen between the two groups.

Laparoscopic replacement of urinary tract segments using biodegradable materials in a large-animal model.

OBJECTIVE: We elected to evaluate laparoscopic segmental bladder and ureteral replacement with free biodegradable graft materials in a large-animal model. MATERIALS AND METHODS: In 18 Yucatan minipigs, a 1.5- to 2.8-cm segment of the upper ureter was excised. In 15 study animals, the ureter was laparoscopically replaced: by a stinted (6F double-J stent) tube graft made of acellular matrix (AMX) prepared from minipig ureters (MUMX) in 6 animals, acellular matrix prepared from domestic pig ureters (DUMX) in 3, and small-intestinal submucosa (SIS) in 6. In 3 control animals, the ureteral gap was bridged only by an indwelling stent. The stent was removed at 6 weeks, and retrograde ureteropyelography was performed preoperatively and at 8 and 12 weeks postoperatively, when animals were sacrificed. In 18 Yucatan minipigs, 3 x 3-cm bladder dome segments were laparoscopically replaced: by acellular matrix prepared from minipig small bowel (MBMX) in 6 animals, and SIS in 6 animals. The bladder was closed primarily in 6 control animals. Bladder capacity was assessed preoperatively and at 6 and at 12 weeks, when the animals were sacrificed. RESULTS: The average operating time for ureteral replacement was 187 (range 105-360) minutes. At 12 weeks, all animals had complete obstruction at the level of the replacement, with fibrosis +/- bone formation at the level of the stricture. For the bladder replacement groups, the average operating time was 147 (range 85-200) minutes. At 12 weeks, the bladder capacity was 60% of the preoperative capacity in the control group, 118% in the MBMX group, and 142% in the SIS group. Histologic examination showed regeneration of urothelium and some muscle with both MBMX and SIS. CONCLUSIONS: We were able to develop a reliable laparoscopic technique for both segmental ureteral and partial bladder replacement in a porcine model. With AMX and SIS replacement, regeneration of urothelium occurred in both ureter and bladder. However, functional replacement was successful only in the bladder.

Mechanism of ureteral stent flow: a comparative in vivo study.

BACKGROUND AND OBJECTIVES: The flow characteristics of ureteral stents have yet to be clearly defined. In this study, flow mechanics were studied in several silicone-based stents including 4.8F, 7F, and 10.3F pigtail; 7F Tower; and a prototype mesh stent. MATERIALS AND METHODS: Forty-five female Yucatan minipigs underwent bilateral laparoscopic occlusion of their renal vessels to stop urine production. A nephrostomy tract was established by retrograde puncture. A stent was placed in the ureter, and three measurements were taken with flow from a bag of irrigant 20 cm above the kidney: stent occluded with a guidewire (extraluminal flow), stent unobstructed (total flow), and laparoscopically placed extraureteral ligature (luminal flow). RESULTS: Luminal flow and, to a lesser extent, total flow appeared to increase as the internal and external diameters of the stent increased. The Tower stent, which had no sideholes, had much lower flow rates in all categories, while the prototype mesh stent showed greater total flow compared with the other stents. Extraluminal flow did not increase with stent size greater than 7F. CONCLUSIONS: Luminal flow, but not extraluminal flow, increased with an increase in the internal diameter of the stent. In general, the least favorable flow occurred with a Tower stent, which had the smallest internal diameter. The greatest flow was seen with the prototype mesh stent.

Laparoscopic midsagittal hemicystectomy and replacement of bladder wall with small intestinal submucosa and reimplantation of ureter into graft.

BACKGROUND AND PURPOSE: A variety of biodegradable organic materials have been used for bladder wall replacement. In some instances, partial replacement has been done using laparoscopic reconstructive techniques. However, to date, this activity has been limited to small patches. Herein, we present the initial experience with laparoscopic sagittal hemicystectomy and the use of laparoscopic reconstructive techniques to replace half of the bladder with small-intestinal submucosa (SIS) and to reimplant the ureter into SIS. MATERIALS AND METHODS: Six female minipigs (20-25 kg) underwent transperitoneal laparoscopic sagittal hemicystectomy; the excised bladder wall was replaced with a 5 x 15-cm patch of SIS (Cook Biotechnology, Spencer, IN). The ipsilateral ureter was reimplanted through a small incision in the graft and secured with two sutures. Cystoscopy and cystometrograms were performed under general anesthesia preoperatively and at 6 and 12 weeks postoperatively. Tissues were harvested at 12 weeks. RESULTS: The procedure was successful in six animals (left three, right three). During cystoscopy at 12 weeks, the area of the graft was not distinguishable from normal mucosa. Cystometrograms revealed maintenance of volume and compliance, with volumes of 338, 343, and 369 mL and intravesical leak-point pressures of 37, 59, and 39 cm H2O at 0, 6, and 12 weeks, respectively. Antegrade ureterograms demonstrated extrinsic obstruction, minimal (two), moderate (three), or complete (one), at the ureterovesical junction. The kidney associated with the completely obstructed ureter was grossly hydronephrotic at sacrifice. Histologically, patchy epithelialization of the graft with a mixture of squamoid and mature transitional-cell epithelium was found. CONCLUSIONS: Laparoscopic hemicystectomy with replacement of the bladder wall and implantation of the ureter into the SIS graft is a feasible procedure. Clinical application awaits improvements in the method of ureteral reimplantation and longer follow-up to assess for ingrowth of muscle and nerve fibers.