Physico-chemical properties and optimization of the deformable FlexyDos3D radiation dosimeter.

Deformable 3D radiation dosimetry is receiving growing interest for the validation of image-guided radiotherapy treatments (IGRT) of moving and deformable targets. Previously, a proof-of-concept of a flexible anthropomorphic 3D dosimeter called 'FlexyDos3D' has been demonstrated. One of the concerns with respect to the FlexyDos3D dosimeter is its dose-response instability. The effect of different formulations of the dosimeter on its stability were investigated. A stable formulation for the dosimeter was found by optimising the ratios of curing agent and base of the silicone matrix between 3% and 4.5% [w/w] curing agent. The effects of elevated curing temperatures and times upon the dosimetric properties were also investigated and the dose-response was found to be independent of curing times for curing times over an hour at 120 °C. 1H NMR spectra of the dosimeter chemical constituents and the effect of radiation dose were determined. The evaporation and diffusion rates of chloroform in the dosimeter were determined and are the likely cause of the dosimeters depth-dose profile uncertainties. A composition for a stable silicone dosimeter which can be cured quickly at elevated temperatures was found, demonstrating the potential for 3D printing of patient-specific dosimeters. However, it is suggested that another radical initiator be used in future formulations of the dosimeter.

Gardner Transition in Physical Dimensions.

The Gardner transition is the transition that at mean-field level separates a stable glass phase from a marginally stable phase. This transition has similarities with the de Almeida-Thouless transition of spin glasses. We have studied a well-understood problem, that of disks moving in a narrow channel, which shows many features usually associated with the Gardner transition. We show that some of these features are artifacts that arise when a disk escapes its local cage during the quench to higher densities. There is evidence that the Gardner transition becomes an avoided transition, in that the correlation length becomes quite large, of order 15 particle diameters, even in our quasi-one-dimensional system.

Intracranial migration of halo fixation pins: a complication of using an extraoral distraction device.

OBJECTIVE: Distraction osteogenesis is a well-accepted technique in the treatment of patients with hypoplastic craniofacial components. Complications of distraction osteogenesis are well described in the literature. We describe a complication of using an external distraction device in a 9-year-old girl with Pfeiffer. INTERVENTION AND RESULTS: A modified Lefort III osteotomy was performed for maxillary hypoplasia with application of an external distraction halo device by a pediatric neurosurgeon. A postoperative computed tomography (CT) scan showed 0.5-cm skull penetration of the cranial pins. The pins were repositioned and the patient was followed up on a regular basis until discharge from the hospital. At 3-week follow-up, a CT scan of the head showed migration of the pins 1.5 cm intracranially. The halo was removed and repositioned at a different site. No detectable neurological sequelae from the pin penetration were noted. The patient developed cellulitis at the site of the penetration and was admitted to the hospital for a course of intravenous antibiotics. There were no other complications, and the rest of her treatment course proceeded as planned. A review of the literature on complications of halo usage as well as suggestions for their management in association with distraction osteogenesis is described.

Carpal compression test and pressure provocative test in veterans with median-distribution paresthesias.

We investigated the value of the carpal compression test (CCT) and the pressure provocative test (PPT) in predicting carpal tunnel syndrome (CTS) in a predominantly male population of veterans. We performed a prospective, blinded comparison of these clinical diagnostic tests with neurophysiological testing. One cohort of 135 consecutive patients was assessed with the CCT; a separate cohort of 134 consecutive patients was assessed with the PPT. Of these 269 patients, 58.4% had electrodiagnostically confirmed CTS. The sensitivity of the CCT was 52.5%, specificity was 61.8%, positive predictive value was 66.6%, and the negative predictive value was 47. 2%. The sensitivity of the PPT was 54.5%, specificity was 68.4%, positive predictive value was 70%, and the negative predictive value was 52.7%. The CCT and PPT had minimal utility in predicting electrodiagnostically confirmed CTS. In a subset of the CCT cohort, 86 consecutive veterans were also evaluated in relation to a clinical gold standard. Of these patients, 60% had CTS based on this gold standard. CCT sensitivity was 53.8%, specificity was 61.8%, positive predictive value was 68.3%, and negative predictive value was 46.7%. The CCT thus had marginal utility in predicting CTS based on a clinical gold standard.

Secondary fractures of Le Fort I osteotomy.

PURPOSE: To report the ophthalmic complications of Le Fort I osteotomy for the correction of dentofacial deformities and to determine the maximal compressive loads applied during pterygomaxillary separation in a cadaver model. METHODS: Two cases of ophthalmic complications arising after Le Fort I osteotomy are reported. Le Fort I osteotomy was performed on five cadavers. The maximal compressive load applied during pterygomaxillary separation was recorded with a 10 kN (3,000 lbf) load cell of a MTS Mini-Bionix servo-hydraulic machine (MTS, Eden Prairie, MN, U.S.A.). A paired t test was used to compare forces applied to the right and left sides. Computed tomography scans of each specimen were obtained after Le Fort I osteotomy to document secondary fractures. The skulls were subsequently stained with 1% fuschin red to highlight secondary fractures. RESULTS: Maximum compressive loads during pterygomaxillary separation ranged from 22 N (5.0 lbf) to 162 N (36.5 lbf), with an average of 106 N (23.8 lbf) (SD 47.6 N [10.7 lbf]). Forces applied on the first operative side were significantly greater than forces applied on the second operative side (p = 0.0034). Secondary fractures were found in three specimens by computed tomography and in two specimens by 1% fuschin red. All secondary fractures occurred on the second operative side. CONCLUSION: Secondary fractures in the Le Fort I osteotomy procedures occurred on the side opposite the greater maximal compressive load and on the second operative side.

Early recovery after endoscopic vs. short-incision open carpal tunnel release.

Endoscopic carpal tunnel release has been claimed to offer improvement in recovery time and postoperative discomfort over open carpal tunnel release. Short-incision open carpal tunnel release has been claimed to offer recoveries comparable with endoscopic techniques. Patients receiving carpal tunnel surgery were randomized to short-incision open release or single-portal endoscopic release. Preoperative and postoperative evaluation included grip and pinch strength measurements and patient completion of a questionnaire regarding symptoms and function. Thirty-six operated hands completed evaluation, including 22 endoscopic and 14 open releases. Early grip and pinch strength after endoscopic carpal tunnel release were improved significantly over short-incision open release (p < 0.05). Subjective evaluation indicated a trend toward improved symptoms and function with endoscopic over short-incision open carpal tunnel release. Endoscopic carpal tunnel release provides faster recovery of strength than short-incision open carpal tunnel release and improves early postoperative comfort and function to a small degree.

Use of the radial forearm microvascular free-flap graft for cranial base reconstruction.

OBJECT: Reconstruction of the cranial base after resection of complex lesions requires creation of both a vascularized barrier to cerebrospinal fluid (CSF) leakage and tailored filling of operative defects. The authors describe the use of radial forearm microvascular free-flap grafts to reconstruct skull base lesions, to fill small tissue defects, and to provide an excellent barrier against CSF leakage. METHODS: Ten patients underwent 11 skull base procedures including placement of microvascular free-flap grafts harvested from the forearm and featuring the radial artery and its accompanying venae comitantes. Operations included six craniofacial, three lateral skull base, and two transoral procedures for various diseases. Excellent results were obtained, with no persistent CSF leaks, no flap failures, and no operative infections. One temporary CSF leak was easily repaired with flap repositioning, and at one flap donor site minor wound breakdown was observed. One patient underwent a second procedure for tumor recurrence and CSF leakage at a site distant from the original operation. CONCLUSIONS: Microvascular free tissue transfer reconstruction of skull base defects by using the radial forearm flap provides a safe, reliable, low-morbidity method for reconstructing the skull base and is ideally suited to "low-volume" defects.

Closed rupture of the deep transverse metacarpal ligament: diagnosis and management.

Closed rupture of the deep transverse metacarpal ligament (DTML) is an unusual injury. We have managed 2 patients with closed rupture of the DTML between the ring and small fingers resulting from crush injuries to the hand. Both patients presented with painful ulnar deviation of the small finger with extension. The diagnosis was confirmed by exploration through a volar incision. Repair of the ligament with use of the adjacent A1 pulleys to butress the repair was successful in both patients and restored a painless finger flexion-extension arc. Closed rupture of the DTML can be confused with a metacarpophalangeal joint collateral ligament rupture due to the characteristic deviation of the small finger.

Recurrent carpal tunnel syndrome following endoscopic carpal tunnel release: a preliminary report.

Persistent or recurrent symptoms following endoscopic carpal tunnel release have been reported in 0.5% to 3% of patients undergoing this procedure. Unfortunately, preoperative risk factors for this complication have not been defined. We reviewed the records of 126 consecutive patients who underwent Agee single-portal endoscopic carpal tunnel release between June 1994 and March 1997. Five patients and six hands required subsequent open carpal tunnel release for persistent or recurrent carpal tunnel syndrome. Fulminant synovitis was identified during open carpal tunnel release in all reexplored patients, and four of the six hands were cured with open release and synovectomy. No recurrences were identified in the group of patients who presented with unilateral carpal tunnel syndrome. The presence of bilateral carpal tunnel syndrome may be a risk factor for persistent or recurrent carpal tunnel syndrome following endoscopic carpal tunnel release.

A safe, reliable method for skin-graft coverage of the radial forearm donor site.

Delayed donor-site healing remains one of the most significant disadvantages of the radial forearm free flap. In an effort to decrease morbidity at the donor site, the authors adopted a closure technique that utilized the flexor digitorum sublimis (FDS) and flexor pollicis longus (FPL) muscle bellies to cover the flexor carpi radialis (FCR) tendon prior to placement of a split-thickness skin graft. While this approach eliminated tendon exposure, two patients with postoperative median-nerve compression forced a modification of this technique. The authors now detach the radial attachment of the FDS muscle and mobilize the median nerve away from the underside of the muscle, to prevent kinking of the nerve when the FDS and FPL muscle bellies are sewn together. With these modifications, the technique retains its efficacy, but with an improved margin of safety for the median nerve.

Successful hand revascularization with urokinase following a crush injury.

Acute hand ischemia is a medical emergency requiring immediate treatment. We report a case of acute hand ischemia due to a crush injury of the wrist. Management with urokinase was successful in reestablishing flow to the ulnar artery and the digital vessels. In the setting of acute trauma with extensive thrombosis of the vessels of the hand, thrombolytic therapy may offer a better treatment option than surgical exploration with bypass grafting.

The need for rigid fixation of combined parasymphyseal and bilateral subcondylar fractures.

Both miniplate and larger fracture plate fixation techniques have been utilized successfully in the treatment of mandibular fractures. Parasymphyseal fractures which occur in conjunction with bilateral subcondylar fractures, however, represent a special fracture pattern that is not well managed with miniplate fixation. Miniplates do not have the tensile strength to resist the strong, muscular-deforming forces that act on these fractures. This fracture pattern is best managed with anatomic symphyseal reduction and internal fixation with a 2.7 mm mandibular fracture plate and a 2.0 mm tension band plate. The subcondylar fractures can then be managed with either intermaxillary fixation or open reduction. This approach provides good functional results and can prevent late complications.

A new flap for nasal tip reconstruction.

Aesthetic reconstruction of tumor defects of the nasal tip and supratip areas remains a challenge. Because of our dissatisfaction with the current reconstructive options, we have developed a modification of the nasalis flap based on the angular artery for the management of nasal tip defects. This is an axial flap-pattern that rotates toward the midline and nasal tip, leaving donor scars in the nasojugal and alar creases. A second rotation flap from the alar groove fills the donor defect in the nasojugal region to minimize scarring. We have utilized this flap 19 times in 18 consecutive patients with nasal tip and supratip tumor defects with follow-up ranging from 10 to 72 months. Donor scars are well concealed and nasal contour is minimally altered. Color and texture matches are excellent, and the pincushion deformity has been eliminated. On the basis of these results, we believe the modified nasalis flap is ideally suited for nasal tip reconstruction.

The use of intra-arterial urokinase in the management of hand ischemia secondary to palmar and digital arterial occlusion.

Impending gangrene of the hand or digits secondary to palmar or digital artery occlusion can be a devastating complication of upper extremity thromboembolic or atheroembolic disease. Over the past 7 years, 9 patients with severe unilateral hand ischemia and impending tissue loss secondary to distal forearm, palmar arch, and digital artery occlusion were managed with intra-arterial urokinase (UK) infusion. The etiology of the ischemia was thromboembolism in 3 patients, atheroembolism in 2, and traumatic ulnar artery occlusion ("hypothenar hammer syndrome") in the remaining 4 patients. Initial high-dose UK was administered in 3 patients (240,000 U per hour for 2 hours) and all 9 patients were maintained on 80,000 to 120,000 U per hour until clot lysis occurred or until a minimum dose of 600,000 U had been given without clinical improvement. Following UK therapy, the 3 patients with thromboemboli had angiographic demonstration of clot lysis as well as complete resolution of ischemia. The 2 patients with atheroemboli showed no angiographic or clinical improvement, and both required surgical intervention. Angiographic improvement was demonstrated in only 1 patient with traumatic ulnar artery occlusion, although 3 of the 4 patients were clinically improved. A pericatheter thrombosis due to insufficient heparinization and a subcutaneous abscess at the femoral artery puncture site were the only complications of UK infusion. No hemorrhagic complications occurred and no adverse effects of lytic therapy were documented in patients who subsequently required surgery. UK is an effective treatment for recent thromboembolism, because it lyses unorganized thrombi. It is ineffective for treatment of organized thrombi or atheroemboli. Because the etiology of acute hand ischemia is not always obvious at the time of presentation, a trial of UK infusion is warranted, because it is relatively safe and its use may obviate the need for complex microsurgical reconstruction.

Are the palmar cutaneous nerves safe during standard carpal tunnel release?

An incision in the axis of the ring finger is thought to be the safest for carpal tunnel release based on cadaveric studies that suggest that the palmar cutaneous nerves do not cross into this area. Despite the use of this incision, persistent postoperative scar tenderness has been reported in up to 36% of patients following standard carpal tunnel release. For this reason, an investigation was undertaken to determine the presence of palmar cutaneous nerves in this incision. Random biopsies of transversely oriented fibrous bands in the subcutaneous tissue were taken during 15 open carpal tunnel releases. In every patient, at least one biopsy was positive for peripheral nerve tissue. These findings, combined with previous cadaveric studies, suggest that a "safe" palmar incision that will avoid injury to palmar cutaneous nerves does not exist. Carpal tunnel release techniques that avoid a palmar incision may lessen postoperative morbidity by avoiding injury to these small cutaneous nerves.

Is training in endoscopic carpal tunnel release appropriate for residents?

Based on the relatively high incidence of complications for surgeons initially learning the technique, endoscopic carpal tunnel release is thought to have a steep learning curve. To determine if endoscopic carpal tunnel release can be safely performed by trainees, the outcomes of 84 patients who underwent endoscopic carpal tunnel release performed by a chief resident or hand fellow in a supervised setting were reviewed. All but 1 patient had uneventful procedures and complete resolution of preoperative symptoms. One patient with persistent symptoms represented the only complication. At reexploration through a standard palmar incision, the transverse carpal ligament was found to have been completely divided and fulminant tenosynovitis surrounding the nerve and flexor tendons was presumed to be the cause of his persistent symptoms. It appears that endoscopic carpal tunnel release can be safely performed by chief residents in a supervised clinical setting. Given that this procedure has a high learning curve, repeated exposure during a residency training program may offer significant advantages over the current approach of training surgeons during a single cadaveric instructional course.

A 32-year follow-up of lunate excision for Kienbock's disease: a case report and a review of results from excision and other treatment methods.

Lunate excision alone is seldom utilized in the management of Kienbock's disease due to concerns about progressive carpal collapse following removal of this central carpal bone. We report a 32-year follow-up of a patient who underwent lunate excision only for treatment of Kienbock's disease with a successful outcome. Although lunate excision is thought to be associated with a high failure rate, a review of the literature suggests that success rates following lunate excision are comparable to those reported for other more conventional techniques such as radial shortening, ulnar lengthening, limited carpal fusions, and proximal row carpectomy. The current perception that lunate excision is associated with a high failure rate is not supported in the literature. As such, it may not be appropriate to assign this operation to the category of "historical interest only."

The management of unsalvageable free flaps.

The loss of vascular flow in the early postoperative period will generally lead to free flap failure. When attempts at flap salvage are unsuccessful, conservative management with delayed flap debridement may be indicated. Seven unsalvageable free flaps were managed with observation and flap debridement 4 to 14 days following loss of vascular signals. At the time of debridement, six of the seven wounds had viable granulation tissue and were successfully closed with skin grafts. The seventh patient had loss of vascular flow to the free flap within 12 hr of surgery and, at the time of delayed debridement, had no evidence of granulation ingrowth. Local revascularization of flaps is known to occur and offers an explanation for these findings. Delayed debridement of unsalvageable free flaps is indicated for noncritical wounds, and may obviate the need for a second free-tissue transfer to obtain wound closure.