Sharp Transection Research Articles

Enhanced Mechanical Properties of Rabbit Flexor Tendons in Response to Intratendinous Injection of Adipose Derived Stromal Vascular Fraction

Tendon injuries are notorious for slow and functionally inferior healing. It is claimed that cell-based therapy would result in faster and more efficient healing of injured tissues with less postoperative complications. Given the limitations associated with ex vivo cellular expansion, we tried to evaluate the possible effects of intratendinous injection of adipose derived stromal vascular fraction on mechanical properties of tendon repair. The model of injury was complete sharp transection of rabbit deep digital flexor tendon followed by primary suture repair and an intratendinous injection of either allogeneic stromal vascular fraction or placebo. Tendons were harvested at three and eight weeks after surgery. The results of mechanical testing showed the treatment caused significant increase in ultimate and yield loads, stress, and energy absorption of repairs compared to controls at both time points. Also, improvement in terms of strain and stiffness were detected at the eighth week in treatments. In comparison with the result of previous studies using cultured mesenchymal stem cells from bone marrow or adipose tissue; the improved mechanical properties observed in the present study suggest that choosing stromal vascular fraction as a readily accessible and instant source of multipotent cells instead of expensive and long-lasting culture expansion may seem more favorable in cell based therapy for tendon injuries. The mechanical functionality of the repairs observed in the present study encourages further investigations into the use of stromal vascular fraction for the repair of tendon injuries.

Extrahepatic Portal Vein Ligation in Major Hepatectomies Performed under Selective Vascular Exclusion: A Case–Control Study

The aim of our study is to assess the effect of extrahepatic ipsilateral portal vein branch ligation in hepatectomies conducted under selective hepatic vascular exclusion with sharp transection of the liver parenchyma. Twenty-six patients (Group A) underwent major hepatectomy from January 2007 to December 2009, and hemostasis was achieved by ligation of the ipsilateral portal vein branch in addition to suture ligation of the cut surface vessels. A control group (Group B) was composed of 26 matched patients picked from our hospital's database, in which hemostasis was achieved by suture ligation of the cut surface vessels only. Warm ischemia time, intraoperative blood loss, blood transfusions, and liver function were compared. Reduced blood loss (450 vs 680 mL, P = 0.03), less transfusions (8 vs 20% of the patients, P = 0.04), and decreased warm ischemia time (34 vs 42 minutes, P = 0.04) were observed in Group A. Extrahepatic ligation of the ipsilateral portal vein branch is simple, safe, and effective in reducing blood loss and warm ischemia time in major hepatectomies performed under selective vascular exclusion.

Use of a radiofrequency probe for tenoscopic‐guided annular ligament desmotomy

Annular ligament desmotomy is commonly performed in horses with chronic tenosynovitis. Previously reported tenoscopic techniques have limitations related to haemorrhage and awkward instrumentation. Radiofrequency (RF) energy affords precision and excellent haemostasis and may be a good alternative to sharp transection of the annular ligament in horses. To describe a technique for using a RF probe for tenoscopic-guided annular ligament desmotomy and to report the clinical outcome of horses in which it was performed. Cadaver specimens (n = 14) and live horses undergoing unrelated terminal procedures (n = 2) were used to optimise the tenoscopic-guided RF annular ligament desmotomy technique. Records were examined for all horses undergoing annular ligament desmotomy with an RF probe from 2003 to 2008 for which follow-up of >1 year post operatively was available. The annular ligament was successfully transected in the cadaver and live horse model limbs using 2 different commercially available RF probes. Complete transection was achieved with practice and confirmed on gross dissection. Histopathology did not reveal any collateral damage to surrounding tissue. Follow-up of >1 year was available for 6 of 7 clinical cases. Four of 6 horses returned to work. Owners were satisfied with the outcome in all cases. Desmotomy using a RF probe allows precise tissue transection under tenoscopic guidance without damage to surrounding structures or haemorrhage. With experience, it is an easily performed technique. In clinical patients, an acceptable outcome may be expected. Tenoscopic-guided RF annular ligament desmotomy offers advantages, including reliable haemostasis and precise tissue transection, over previously reported techniques and is a viable surgical alternative for treating horses with annular ligament desmitis and other complex pathology within the tendon sheath.

Death Secondary to a Donkey's Bites

We present a unique case of death due to the assault and bites of a donkey on a 65-year-old man. The farmer, found dead in his farmyard, had a very deep wound in the anterior region of the neck, with a sharp transection of the trachea and severe bleeding by several minor vessels wall disruptions. The cause of death was established to be massive bleeding combined with asphyxia due to aspiration of the blood. Moreover, multiple contusions with associated skin abrasions and perforations were present. The general impression of the injuries was consistent with an animal's bite marks. Herbivorous or omnivorous bite attacks on humans are rare; instead, these animals attack by kicking, trampling, and kneeling, resulting in secondary blunt injuries. The donkey is usually a docile animal, but its behavior can be aggressive during the mating season, and the possibility of biting should not be underestimated, as illustrated by the 2 cases published previously as well as by the case presented here.

Outcome of the External Carotid Artery Following Carotid Endarterectomy with Added External Carotid Artery Eversion Endarterectomy

To study the results of eversion endarteterctomy of the external carotid artery (ECA) performed as part of standard CEA at a tertiary referral center using duplex ultrasonography. Sixty patients (18 women and 42 men) who underwent 65 carotid endarterectomies at Waikato Hospital between January 2006 and July 2007 for significant internal carotid artery (ICA) disease were studied. The procedure also included eversion endarterectomy of the ECA with sharp transection at eversion end point. Preoperative and postoperative duplex scans were performed for all patients using Acuson (USA) ultrasound machine and by one sonographer. Postoperative follow-up scans at periods between 6 weeks and 18 months were reviewed and analyzed with Ascer et al. Doppler ultrasound-scan peak systolic velocity (PSV) criteria. Preoperative scans revealed significant bifurcation disease involving both ICA and ECA in all patients. The first post operative scan, done six weeks post-operatively, revealed one incomplete ECA endarterectomy, resulting in moderate (50%-74%) stenosis, while the rest had no evidence of residual ECA disease at the site of ECA endarterectomy. Over the post-operative period, sixteen (24.6%) ECA lesions and no occlusions were reported. The degree of ECA stenosis ranged from moderate to severe with PSVs ranging from 120 to 461 cm per second. All ECA lesions were ostial. Only 3 (18.7%) lesions were detected in the first nine months post operatively. Fifteen lesions were smooth and regular on duplex, while one had features of irregular residual stenosis. Eight (50%) were isolated ECA lesions, while the rest was associated with either ICA restenosis or occlusion. ECA disease progression detected by Duplex ultrasound following eversion endarterectomy, as a part of CEA, commonly happens after 9 months and results in recurrent ECA stenosis, in most cases. Timing and features of the lesions suggest an intimal reaction as the aetiology in most cases. Eversion endarterectomy of the ECA does not predispose to ECA occlusion.

Combined Blunt-Clamp Dissection and LigaSure Ligation for Hepatic Parenchyma Dissection: Postcoagulation Technique

Blunt-clamp dissection allows for visualization of intrahepatic vessels and individual ligation of major blood or bile vessels. Recently, many instruments have been developed for "precoagulation" of liver parenchyma before sharp transection, but suffer from the possibility of injuring major blood and biliary vessels that are not well-visualized, along with high cost. In this article, we describe a "postcoagulation" technique combining clamp dissection and sealing of vessels under direct vision using a tissue-sealing device. Clinical evaluation of 400 patients from 2 centers subjected to liver resection using this technique. There were no cases complicated by hemorrhage. There was an incidence of 1.8% for bile leaks. This low incidence of biloma formation was seen even with the high incidence (49%) of abnormal parenchyma encountered in this cohort. Combining the clamp-crushing method with use of the LigaSure device (Valleylab) allows identification of intraparenchymal vessels followed by sealing. This method of parenchymal transaction optimizes ease of use with confidence in vessel ligation.

The introduction of a simple maneuver to reduce the risk of postoperative bleeding after major hepatectomies

In major hepatectomies, postoperative increases in central venous pressure (CVP) may cause suture failure and massive bleeding. The aim of our study is to test the application of an intraoperative maneuver to reduce the risk of postoperative bleeding. Our study included 172 consecutive patients who had major liver resection with selective hepatic vascular exclusion and sharp transection of the liver parenchyma. An intraoperative maneuver (5 s occlusion of the hepatic vein) was applied in an alternating way, and the patients were assigned to two groups: Cohort A (n = 86), that was granted the maneuver, and Cohort B (n = 86), that was used as a control group. In Cohort A, application of the maneuver was successful in demonstrating bleeders under low CVP levels. Cohort A had lower rate of massive bleeding requiring emergency reoperation (2.3 vs 5.8%, P = 0.049), less postoperative blood transfusions (13 vs 24%, P = 0.042), lower morbidity (20 vs 35%, P < 0.045) and shorter hospital stay compared to Cohort B. Hepatectomies conducted under low CVP are prone to postoperative hemorrhage which can be prevented if the final bleeding control is performed under high pressure in the hepatic veins. Application of our testing maneuver effectively unmasked previously undetectable bleeding veins.

A Guidance Channel Seeded With Autologous Schwann Cells for Repair of Cauda Equina Injury in a Primate Model

Background/Objective: To evaluate an implantable guidance channel (GC) seeded with autologous Schwann cells to promote regeneration of transected spinal nerve root axons in a primate model.Methods: Schwann cells were obtained from sural nerve segments of monkeys (Macaca fascicularis; cynomolgus). Cells were cultured, purified, and seeded into a PAN/PVC GC. Approximately 3 weeks later, monkeys underwent laminectomy and dural opening. Nerve roots of the L4 through L7 segments were identified visually. The threshold voltage needed to elicit hindlimb muscle electromyography (EMG) after stimulation of intact nerve roots was determined. Segments of 2 or 3 nerve roots (each ∼8-15 mm in length) were excised. The GC containing Schwann cells was implanted between the proximal and distal stumps of these nerve roots and attached to the stumps with suture. Follow-up evaluation was conducted on 3 animals, with survival times of 9 to 14 months.Results: Upon reexposure of the implant site, subdural nerve root adhesions were noted in all 3 animals. Several of the implanted GC had collapsed and were characterized by thin strands of connective tissue attached to either end. In contrast, 3 of the 8 implanted GC were intact and had white, glossy cables entering and exiting the conduits. Electrical stimulation of the tissue cable in each of these 3 cases led to low-threshold evoked EMG responses, suggesting that muscles had been reinnervated by axons regenerating through the repair site and into the distal nerve stump. During harvesting of the GC implant, sharp transection led to spontaneous EMG in the same 3 roots showing a low threshold to electrical stimulation, whereas no EMG was seen when harvesting nerve roots with high thresholds to elicit EMG. Histology confirmed large numbers of myelinated axons at the midpoint of 2 GC judged to have reinnervated target muscles.Conclusions: We found a modest rate of successful regeneration and muscle reinnervation after treatment of nerve root transection with a Schwann cell-seeded, implanted synthetic GC. Newer treatments, which include the use of absorbable polymers, neurotrophins, and antiscar agents, may further improve spinal nerve regeneration for repair of cauda equina injury.

Celiac trunk compression syndrome requiring surgery in 3 adolescent patients

Background/Methods Celiac trunk compression syndrome is a rare cause of recurrent, nonspecific upper abdominal pain. In this article, we present 3 cases of celiac trunk compression syndrome in 15- and 16-year-old adolescents who were treated surgically in our clinic and discuss our findings with existing literature. Results All 3 adolescents complained about unspecific upper gastrointestinal pain. The performance of digital subtraction angiography and, accordingly, magnetic resonance angiography showed, respectively, a stenosis and an occlusion of the celiac artery. In all cases, a decompression of the celiac trunk as well as a resection of the celiac plexus in the region near the outlet of the trunk was performed. Patients have been surveyed between 12 and 18 months postoperatively. In all cases, the gastrointestinal symptoms have completely disappeared. Discussion Celiac artery compression syndrome is understood to consist of symptoms of recurrent pain, caused by a neurovascular narrowing of the aortic hiatus and celiac trunk. The surgical approach of choice is sharp transection of the median arcuate ligament, along with complete resection of the nerve fibers of the celiac plexus with or without performance of revascularisation. In summary, celiac trunk compression syndrome is a rare cause of recurrent epigastric pain that should be not be ignored completely as a differential diagnosis.

Lacerations to the Brachial Plexus: Surgical Techniques and Outcomes

The charts of patients with 201 brachial plexus elements sustaining operative lacerations and managed at Louisiana State University Health Sciences Center (LSUHSC) were reviewed retrospectively. Results for elements injured by sharp transections and undergoing suture repairs performed within 72 hr, as well as secondary suture and secondary graft repairs are documented. Similarly, results for secondary end-to-end suture anastomosis and secondary graft repairs for elements sustaining blunt transections are reviewed. Results for neurolysis, end-to-end suture anastomosis, and graft repairs for plexus elements in continuity despite the laceration injury are reviewed. Outcomes for the LSUHSC series of brachial plexus lacerations are one of the best of all LSUHSC plexus injuries, even for elements generally viewed as unfavorable for repair. Lesions in continuity with positive nerve action potentials (NAPs) had the best outcomes.

Sharp liver transection versus clamp crushing technique in liver resections: A prospective study

Parenchymal liver transection constitutes an important phase of liver resection. Serious intraoperative bleeding, together with injuries to vital structures of the liver remnant, can occur during this stage. A method of sharp liver parenchymal transection with scalpel is compared in a prospective randomized manner with the widely used clamp crushing technique. Patients scheduled for hepatectomy under selective hepatic vascular exclusion (N = 82) were allocated randomly to either the sharp transection group (n = 41) or the clamp crushing group (n = 41). Warm ischemic time, blood loss and transfusions, postoperative morbidity and mortality, and tumor-free margins were recorded in both groups and analyzed. When the sharp transection group was compared with the clamp crushing group, the two groups were similar in warm ischemic time (median 36 vs 34 minutes), total operative time (median 205 vs 211 minutes), intraoperative blood loss (median 500 vs 460 mL), blood transfusion requirements (median value 0 in both groups), and overall complication rate (44% vs 39%). However, sharp transection yielded better tumor-free margins compared with the clamp crushing technique (12 +/- 1.4 mm vs 8 +/- 1.5 mm, mean +/- SD, P < .05). Sharp liver parenchymal transection with a scalpel is equally safe in terms of blood loss and mortality compared with the clamp crushing method. Although it is a technically demanding method, requiring selective hepatic vascular occlusion, it may be recommended when the tumor-free margins are anticipated to be narrow.

Effect of initial fluid resuscitation on subsequent treatment in uncontrolled hemorrhagic shock in rats.

Using a modified uncontrolled hemorrhage shock model with massive splenic and vascular injury, we evaluated outcome and tissue oxidation injury with different resuscitation interventions during prehospital and hospital phases. The aim of our study was to explore the effect of initial fluid resuscitation on subsequent treatment of uncontrolled hemorrhagic shock in rats. Uncontrolled hemorrhagic shock was produced in 114 Wistar rat by sharp transection both of the splenic parenchyma at one location between the major branches of the splenic artery into the spleen and of one of the major branches of the splenic artery. Experimental design consisted of three phases: a "prehospital phase" (resuscitation with balanced saline to a mean arterial pressure (MAP) of 40, 50, 60, 80, and 100 mmHg, respectively, when MAP reached 30 mmHg), followed by a "hospital phase" (120 min, including control of hemorrhage and resuscitation with balanced saline and whole blood (2:1) or balanced saline alone to a MAP >80 mmHg), and a 240-min observation phase. Blood loss, infused volume, hematocrit, and survival rate were recorded. At the end of the experiment, survivors were sacrificed, and the lung, kidney, and distal ileum were harvested for determination of malondialdehyde (MDA) content and total antioxidative capacity (T-AOC). All rats that were resuscitated to a MAP >80 mmHg in the prehospital phase and received balanced saline alone in the hospital phase died, whereas those that had been resuscitated to a MAP of 40 or 50 mmHg during the prehospital phase and then resuscitated with balanced saline and whole blood in the hospital phase survived throughout the experiment. The animals whose MAP was kept higher than 80 mmHg had significantly higher MDA content and lower T-AOC than those whose MAP was maintained 40, 50, or 60 mmHg during the prehospital phase. In the hospital phase, resuscitation with balanced saline and whole blood not only relieved tissue damage but also improved the survival, as indicated by 44.4% survival rate in the rats that resuscitated to a MAP of 80 or 100 mmHg in the prehospital phase. These results suggested that in our uncontrolled hemorrhagic shock model, limited resuscitation in the prehospital phase had benefit for subsequent treatment in the hospital phase in terms of alleviated tissue damage and improved survivorship.

Ultrasound visualization of central slip injuries of the finger extensor mechanism

Purpose To evaluate the ability of ultrasound to detect a central tear of the finger extensor tendon mechanism. Methods Twelve fresh-frozen and thawed cadaver fingers were used. All fingers had a midradial incision with exposure of the extensor mechanism over the proximal interphalangeal joint. Six fingers had a sharp transection of the central slip. The other 6 fingers were used as sham dissection controls. All fingers had the exposure closed by suture and then were examined by a musculoskeletal ultrasonographer. Results All 12 fingers were identified correctly as either sham controls with intact central slips or as injury models that had a transected central slip. Thus there was a sensitivity of 100% a specificity of 100%, and a positive predictive value of 1.000, which were statistically significant. Conclusions Diagnostic ultrasound is a very accurate noninvasive study that can identify central slip injuries in the extensor mechanism of the finger. We recommend that clinically suspected cases of boutonniere injury be scanned by high-frequency ultrasound to confirm the diagnosis and allow either early initiation of splinting or eliminate the need for prolonged splinting required for this injury.

Highlights Of The Society Of Urologic Oncology Meeting, June 2, 2001

Highlights Of The Society Of Urologic Oncology Meeting, June 2, 2001

Recent progress in flexor tendon healing

AbstractAlthough advances in the treatment of flexor tendon injuries have led to improved clinical outcomes during the past several decades, a subset of patients continue to experience a loss of function. Using a canine model of sharp transection of the flexor digitorum profundus tendon followed by repair and rehabilitation using clinically relevant techniques, we have examined the influence of multistrand suture and postoperative rehabilitation variables on digital function and tendon strength. Our findings highlight the critical role of repair technique in providing a stiff and strong repair and indicate that continued refinement of suture techniques is warranted in order to minimize repair-site elongation (gap). Gap formation continues to occur at a high frequency, and the formation of gaps greater than 3 mm delays the accrual of repair-site strength that occurs with time. Furthermore, our results indicate that passive-motion rehabilitation that produces a moderate amount of tendon excursion (2mm) at low levels of tendon force (5 N) is sufficient to inhibit adhesion formation and to promote healing. Increases in excursion or force beyond these levels do not accelerate the healing process. These findings suggest that we are approaching the limit of the extent to which we can modulate healing by manipulating rehabilitation variables such as tendon excursion and force. Future advances will probably require manipulation ofthe biological factors that promote healing.

Laparoscopic ovariectomy using sequential electrocoagulation and sharp transection of the equine mesovarium.

To describe in horses and ponies a laparoscopic ovariectomy technique facilitated by electrosurgical instrumentation. Elective ovariectomy was performed in 23 mares using laparoscopic electrosurgical instrumentation. Twenty-three mares (13 horses, 10 ponies), aged from 2 to 21 years and weighing 90 to 545 kg. Food was withheld for a minimum of 12 hours. Mares were sedated with detomidine hydrochloride (0.02 to 0.03 mg/kg) or xylazine hydrochloride (0.5 to 1.0 mg/kg). Excluding the pony mares, all other mares were restrained in stocks. Portal sites in the paralumbar fossa region were desensitized with 2% mepivacaine. Abdominal insufflation was achieved through a teat cannula positioned in the ventral abdomen or a Verres-type needle placed through the paralumbar fossa. After trocar and laparoscope insertion, the ipsilateral ovary and mesovarium were identified, and the mesovarium, tubal membrane, and proper ligament were infiltrated with 2% mepivacaine. The mesovarium was coagulated using bipolar or monopolar electrosurgical forceps and transected sequentially from cranial to caudal until the ovary was completely freed and then removed. The contralateral ovary was removed in a similar fashion through the opposite paralumbar fossa. Bipolar and monopolar electrosurgical forceps were easy to use and provided adequate coagulation of vessels within the mesovarium. Two mares were euthanatized after the procedure for unrelated reasons. One mare had mild signs of colic 24 hours after ovariectomy. In 1 pony mare, the incision used to remove one ovary dehisced on the 5th postoperative day and was allowed to heal by second-intention. No long-term complications had occurred in 11 horses and 10 ponies, 6 to 24 months after surgery. Laparoscopic ovariectomy and hemostasis of the mesovarium can be easily accomplished using electrosurgical instrumentation. Standing laparoscopic ovariectomy, using electrosurgical instrumentation, is an effective and safe technique to provide hemostasis of the mesovarium in mares.

Effects of increased in vivo excursion on digital range of motion and tendon strength following flexor tendon repair.

Postoperative rehabilitation is an important factor in determining functional outcome following intrasynovial flexor tendon repair. We hypothesized that a rehabilitation protocol that produced increased in vivo excursion would lead to increased digital range of motion and tendon strength and decreased adhesion formation in a canine model. Ninety-six flexor digitorum profundus tendons from 48 dogs were cut transversely and repaired by a multistrand suture technique. Postoperative rehabilitation was performed daily with a low excursion-low force (1.7-mm average excursion; < 10 N force) or a high excursion-low force (3.6 mm excursion; < 10 N force) protocol. After death of the dogs at 10, 21, or 42 days, specimens were evaluated for digital range of motion, tensile mechanical properties, elongation of the repair site, and adhesion formation. Our data indicate that the range of motion of digits whose tendons were at low or high excursion was similar to that of controls. Increased in vivo tendon excursion due to synergistic wrist motion did not significantly affect ex vivo flexion of the distal and proximal interphalangeal joints or tendon displacement (p > 0.05). Similarly, tensile properties (ultimate load, repair site rigidity, and repair site strain at 20 N and at failure) and length of the gap at the repair site were not significantly affected by increased excursion (p > 0.05). Severity of adhesion formation was reduced slightly by increased excursion (p = 0.04). Our findings indicate that 1.7 mm of tendon excursion is sufficient to prevent adhesion formation following sharp transection of the canine flexor tendon and that additional excursion provides little added benefit.

The effect of gap formation at the repair site on the strength and excursion of intrasynovial flexor tendons. An experimental study on the early stages of tendon-healing in dogs.

Elongation (gap formation) at the repair site has been associated with the formation of adhesions and a poor functional outcome after repair of flexor tendons. Our objectives were to evaluate the prevalence of gap formation in a clinically relevant canine model and to assess the effect of gap size on the range of motion of the digits and the mechanical properties of the tendons. We performed operative repairs after sharp transection of sixty-four flexor tendons in thirty-two adult dogs. Rehabilitation with passive motion was performed daily until the dogs were killed at ten, twenty-one, or forty-two days postoperatively. Eight tendons ruptured in vivo. In the fifty-six intact specimens, the change in the angles of the proximal and distal interphalangeal joints and the linear excursion of the flexor tendon were measured as a 1.5-newton force was applied to the tendon. The gap at the repair site was then measured, and the isolated tendons were tested to failure in tension. Twenty-nine tendons had a gap of less than one millimeter, twelve had a gap of one to three millimeters, and fifteen had a gap of more than three millimeters. Neither the time after the repair nor the size of the gap was found to have a significant effect on motion parameters (p > 0.05); however, the ultimate force, repair-site rigidity, and repair-site strain at twenty newtons were significantly affected by these parameters (p < 0.05). Testing of the tendons with a gap of three millimeters or less revealed that, compared with the ten-day specimens, the forty-two-day specimens failed at a significantly (90 percent) higher force (p < 0.01) and had a significantly (320 percent) increased rigidity (p < 0.01) and a significantly (60 percent) decreased strain at twenty newtons (p < 0.05). In contrast, the tensile properties of the tendons that had a gap of more than three millimeters did not change significantly with time. Our data indicate that, in a dog model involving sharp transection followed by repair, a gap at the repair site of more than three millimeters does not increase the prevalence of adhesions or impair the range of motion but does prevent the accrual of strength and stiffness that normally occurs with time.

The timing of congenital brachial plexus injury: A study of electromyography findings in the newborn piglet

Objective: Permanent congenital brachial plexus palsy is a recognized serious complication associated with shoulder dystocia. The timing and etiology of this injury remains controversial. Previous authorities have used adult-derived, non–brachial plexus data to extrapolate the anticipated timing for electromyographic denervation changes to date such injuries in the newborn. With use of a domestic swine model, this investigation tests the hypothesis that electromyographic evidence of brachial plexus denervation in the newborn is temporally different than that in the adult. Study Design: Five healthy 2-day-old and two adult pigs underwent unilateral sharp transection of the brachial plexus. Daily electromyographic studies were performed in brachial plexus innervated muscle groups on the involved and contralateral (control) front limbs. Postmortem measurements of the transected nerve segments were obtained in one piglet and one adult animal. Representative hard copy recordings of individual electromyographic studies were collected. Results: Immediately after surgical transection of the brachial plexus, no electromyographic evidence of denervation was observed. Uniformly in the newborn piglets, at 24 hours after transection, denervation in the form of fibrillation potentials, positive sharp waves, and complex repetitive discharges was seen. Serial testing demonstrated proximal to distal gradients of denervation over the next 24 to 48 hours. A delay in electromyographic evidence of denervation was observed in the two adult pigs until days 5 and 8, respectively. Control limb studies remained normal throughout the study period. Nerve length measurements for individual muscle groups were as follows for the adult and newborn pigs, respectively: deltoid 11.4 cm, 2.5 cm; cleidobrachialis 16.0 cm, 4.0 cm; triceps 15.5 cm, 4.5 cm; forelimb flexors 26.0 cm, 6.5 cm; and extensor carpi radialis 31.0 cm, 9.0 cm. Conclusion: Electromyographic evidence of brachial plexus denervation after surgical transection differs between the newborn and the adult pig. Consistent with wallerian degeneration, a correlation exists between length of the distal nerve segment and timing for electromyographic signs of denervation. These findings suggest it would be inappropriate to extrapolate the anticipated timing for electromyographic changes in the newborn on the basis of previously established adult non–brachial plexus data. (Am J Obstet Gynecol 1998;178:688-95.)

Healing of the Anterior Attachment of the Rabbit Meniscus to Bone

In a rabbit model the healing process of the anterior attachment of the medical meniscus was observed during the first 12 weeks after sharp transection and refixation in a tibial bone channel. Evaluations of the healing tissue were histologic analysis, application of immunohistochemical methods to show collagen types and nerve regeneration, and mechanical load to failure tests. Secondary changes to knee joint cartilage, as signs of eventual dysfunction of the refixed meniscus, were evaluated by analysis of proteoglycan fragment concentration in joint fluid and histologic analysis of knee joint articular cartilage and synovium. The healing tissue between the refixed attachment and bone matured from highly cellular, nonspecific granulation tissue at 1 week, to bone, fibrocartilaginous, and fibrous tissues, which at some sites developed an insertion specific tissue arrangement within a 12-week period. However, the irregular interface between the fibrocartilaginous tissue and the underlying bone, which is typical for a normal insertion, was not reestablished. Labeling for collagen Types I and II in the newly formed insertion did not return to normal. In addition a few collagen fibers connected the refixed attachment tissue to bone. New bone formation turned the initially cancellous bone tunnel walls into more solid cortical bone. However, new bone formation did not fill the distal part of the channel. The refixed meniscal attachment underwent necrosis and was revitalized by cell ingrowth from the periphery. Nerve fibers were found in the newly formed insertion by 12 weeks. The failure load at tensile testing never reached more than 20% that of a normal attachment. Degeneration of articular cartilage and increased proteoglycan fragment in the joint fluid were common after this procedure. These data suggest that, despite the focal appearance of insertion specific tissues and healing of collagen fibers to bone, the tissue architecture of a normal meniscal insertion and a normal meniscal joint protective function were not reestablished.