Volar plating of AO C3 distal radius fractures: biomechanical evaluation of locking screw and locking smooth peg configurations.

PURPOSE: The goal of this study was to determine whether locking screws or smooth locking pegs optimize fixation of AO C3 intra-articular distal radius fractures. A secondary goal was to determine which combinations of locking screws and smooth locking pegs influence construct stability. METHODS: In anatomic radius models, AO C3 intra-articular distal radius fractures were fixed using volar locking plates. For the first part, 16 specimens were randomized to receive either 2 locking screws or 2 smooth locking pegs in each of the 3 pairs of holes in the plate. For the second part, 30 specimens were randomized to receive any 4 combinations of locking screws and smooth locking pegs in each of the 3 pairs of holes. Axial loading to failure was applied. RESULTS: Constructs consisting of 4 smooth locking pegs within the lunate fragment were significantly weaker than constructs with 4 locking screws (means 626 N vs 981 N, respectively). Constructs with smooth locking pegs in the ulnar positions of the lunate fragment were weaker than with locking screws in these positions (means 737 N vs 977 N, respectively). Locking screws in the subchondral position of the lunate fragment were stronger than smooth locking pegs in these positions (means 1,227 N vs 934 N, respectively) and any other combination (means 1,227 N vs 942 N, respectively). CONCLUSIONS: Use of locking screws as opposed to smooth locking pegs for AO C3 intra-articular distal radius fractures, particularly subchondral and in the ulnar side of the lunate fragment, optimizes construct stability. This may have implications on postoperative rehabilitation protocols and may limit costs related to use of volar locking plates.

Simulation of nasal flow by lattice Boltzmann methods.

The lattice Boltzmann method is used to calculate the incompressible, viscous flow of air through a model of a nasal cavity, used in experiments. Computations are performed for steady flows at the inspiration and expiration phase of nose breathing. Computed pressure distributions and friction coefficients compare well with Navier-Stokes solutions from a finite-volume method on structured, curvilinear grids. The comparison with conventional Navier-Stokes solvers shows several advantages of the lattice Boltzmann method in particular for bio-medical flow problems. These are the fast grid generation, the simple, granular algorithm, suited for efficient parallelization and the high flexibility for implementing complex boundary conditions and additional transport equations. Lattice Boltzmann methods are therefore efficient candidates for fast flow predictions in the frame of computer-aided rhino-surgery.

Identification and functional characterization of a novel F5 mutation (Ala512Val, FVB onn ) associated with activated protein C resistance.

UNLABELLED: Essentials Activated protein C (APC) resistance is a prevalent risk factor for venous thrombosis. A novel missense mutation (Ala512Val - FVBonn ) was characterized in vitro and in silico. FVBonn is a new cause of APC resistance and venous thrombosis. FVBonn expresses additionally enhanced procoagulant activity in the absence of APC. SUMMARY: Background Activated protein C (APC) resistance is a prevalent risk factor for venous thrombosis. This phenotype is most commonly associated with the factor V Arg506Gln mutation (FV Leiden), which impairs the APC-mediated inactivation of both activated FV (FVa) and activated FVIII (FVIIIa). Objectives Here, we report the identification and characterization of a novel FV mutation (Ala512Val, FVBonn ) in six patients with APC resistance and venous thrombosis or recurrent abortions. Methods FVBonn was expressed in a recombinant system and compared with recombinant wild-type (WT) FV and FV Leiden in several functional assays. Results FVBonn conferred APC resistance to FV-depleted plasma, both in the activated partial thromboplastin time (APTT)-based test (APC sensitivity ratio [APCsr] of 1.98 for FVBonn versus 4.31 for WT FV and 1.59 for FV Leiden) and in the thrombin generation-based test (normalized APCsr of 5.41 for FVBonn versus 1.00 for WT FV and 8.99 for FV Leiden). The APC-mediated inactivation of FVaBonn was slower than that of WT FVa (mainly because of delayed cleavage at Arg506), but was greatly stimulated by protein S. The APC cofactor activity of FVBonn in FVIIIa inactivation was ~ 24% lower than that of WT FV. In line with these findings, an in silico analysis showed that the Ala512Val mutation is located in the same loop as the Arg506 APC cleavage site and might hamper its interaction with APC. Moreover, FVBonn was more procoagulant than WT FV and FV Leiden in the absence of APC, because of an increased activation rate and, possibly, an enhanced interaction with activated FX. Conclusions FVBonn induces hypercoagulability via a combination of increased activation/procoagulant activity, decreased susceptibility to APC-mediated inactivation, and slightly reduced APC cofactor activity.

Indirect reduction and percutaneous fixation versus open reduction and internal fixation for displaced intra-articular fractures of the distal radius: a randomised, controlled trial.

A total of 179 adult patients with displaced intra-articular fractures of the distal radius was randomised to receive indirect percutaneous reduction and external fixation (n = 88) or open reduction and internal fixation (n = 91). Patients were followed up for two years. During the first year the upper limb musculoskeletal function assessment score, the SF-36 bodily pain sub-scale score, the overall Jebsen score, pinch strength and grip strength improved significantly in all patients. There was no statistically significant difference in the radiological restoration of anatomical features or the range of movement between the groups. During the period of two years, patients who underwent indirect reduction and percutaneous fixation had a more rapid return of function and a better functional outcome than those who underwent open reduction and internal fixation, provided that the intra-articular step and gap deformity were minimised.

The de-endothelialized rat carotid arterial graft: a versatile experimental model for the investigation of arterial thrombosis.

A novel model of arterial thrombosis was developed. A mechanical endothelium-denuding injury was created (using a scalpel blade) on harvested, freezer-stored rat carotid arteries. Vessel length of 5 mm. were grafted into the femoral arteries of recipient Sprague-Dawley rats using microvascular anastomotic technique. Patency rates in untreated animals were compared with those in animals receiving systemic aspirin or heparin. The control group patency after 2 hours of flow was 15%, while grafts in aspirin- and heparin-treated animals achieved 35% and 95% patency rates, respectively. Uninjured non-frozen carotid grafts in untreated animals yielded a 95% patency rate, while frozen grafts achieved an 80% patency. Therapeutic levels of aspirin, heparin, and urokinase were confirmed through tail bleeding and whole blood clotting tests, as well as platelet aggregation studies and scanning electron microscopy of the graft lumenal surfaces. A long-term series using syngeneic grafts placed in recipients (Lewis-to-Lewis) and employing systemic heparinization demonstrated maintenance of patency for 4 weeks. Scanning electron microscopy revealed good re-endothelialization, well advanced by one week. Histology confirmed the regrowth of endothelial cells, but showed sparse cellular repopulation of medial and adventitial layers. The mechanical injury model was compared to enzymatic de-endothelialization (using trypsin or collagenase), for which patency rates were similar (10% and 0%, respectively). Trypsin de-endothelialized vessels were tested in vitro for the amount of active trypsin remaining bound to the lumenal surface; no detectable activity was found when trypsin inhibitor was applied following trypsin treatment. The versatility of allowing both in vitro evaluation and in vivo patency assessment demonstrates the uniqueness and value of this new model, offering an avenue toward more direct investigations of surface-mediated thrombotic processes.

The contribution of MD-PhD training to academic orthopaedic faculties.

UNLABELLED: Little is known about the distribution of research-trained physicians across the various specialties. To document the extent to which MD-PhD programs are a source of research-trained faculty for orthopaedic departments, this study examined the specialty choices of graduates of the Medical Scientist Training Program (MSTP) from 1964 to 1994. The MSTP, a combined MD-PhD program supported by the National Institute of General Medical Sciences, (NIGMS), produces roughly 25% of all MD-PhDs in the US. METHODS: Copies of the appendices from training grant applications containing information on MSTP graduates were obtained from the NIGMS. Also, a questionnaire was mailed to 116 university-affiliated orthopaedic surgery departments asking how many faculty were MD's, PhDs or MD-PhDs. RESULTS: Records were obtained for all MST programs. Information on postdoctoral training and/or a current position was reported for 1615 graduates who earned both MD and PhD. Of these graduates, 277 chose non-clinical paths. The other 1338 entered a residency or internship. Of these, 593 were still in residency training, 566 were academic faculty members and 130 were in private practice. In the records, 12 (0.9%) were listed as orthopaedic surgical residents (6) or faculty (6). At this time, all 12 have completed training, and 11 are in academic practice. Eighty-three departments replied to the questionnaire. In that sample of 1761 faculty positions, 1478 were MDs, 217 were PhDs and 36 (2.0%) were MD-PhDs. CONCLUSION: Despite robust support of MD-PhD programs, the number of dual degree recipients on orthopaedic faculties is small when compared to the relative size of the specialty. Other sources of research-trained staff should perhaps be developed.

Restoration of function of the thumb flexor apparatus requires repair of the oblique and one adjacent flexor tendon pulley.

Damage to the pulleys of the thumb flexor apparatus may cause bow-stringing of the tendon and affect muscle function. An experiment using the hands and distal forearms of cadavers was designed to determine which damaged pulleys increase excursion length of the flexor tendon with constant tendon and resisting loads. Each specimen was mounted to a loading frame with a dead weight pinned to the tip of the thumb. The thumb flexor tendon was clamped to an actuator that applied a fixed load and measured excursion of the tendon. Ranges of motion of the thumb joint were also measured. The thumb flexor apparatus of each specimen was tested intact first, with the hand in flexed, neutral, and extended positions; then it was tested with progressive sectioning of pulleys from proximal to distal in one group and from distal to proximal in a second group. The length of excursion increased significantly with all pulleys cut but there was no effect on overall range of motion of the thumb. With proximal to distal sectioning, no change in tendon excursion occurred when the flexor retinaculum and the first annular pulleys were cut, until the oblique pulley was sectioned, leaving only the second annular pulley intact (range, 1.17 - 1.31 times that of intact excursion, dependent on position of the hand). With distal to proximal sectioning, tendon excursion was not affected when the second annular and oblique pulleys were cut but did increase when the first annular pulley was sectioned, leaving only the flexor retinaculum intact (range, 1.28 - 1.36 times that of intact excursion). Dependent on the location of damage, therefore, an intact oblique or first annular pulley can maintain normal excursion of the tendon.

Consistency of AO fracture classification for the distal radius.

We sought to quantify agreement by different assessors of the AO classification for distal fractures of the radius. Thirty radiographs of acute distal radial fractures were evaluated by 36 assessors of varying clinical experience. Our findings suggest that AO 'type' and the presence or absence of articular displacement are measured with high consistency when classification of distal radial fractures is undertaken by experienced observers. Assessors at all experience levels had difficulty agreeing on AO 'group' and especially AO 'subgroup'. To categorize distal radial fractures according to joint displacement and AO type is simple and reproducible. Our study examined only whether distal radial fractures could be consistently classified according to the AO system. Validation of the classification as a predictor of outcome will require a prospective clinical study.

A comparison of short- and long-term intravenous antibiotic therapy in the postoperative management of adult osteomyelitis.

The current standard recommendation for antibiotic therapy in the management of chronic osteomyelitis is intravenous treatment for six weeks. We have compared this regime with short-term intravenous therapy followed by oral dosage. A total of 93 patients, with chronic osteomyelitis, underwent single-stage, aggressive surgical debridement and appropriate soft-tissue coverage. Culture-specific intravenous antibiotics were given for five to seven days, followed by oral therapy for six weeks. During surgery, the scar, including the sinus track, was excised en bloc. We used a high-speed, saline-cooled burr to remove necrotic bone, and osseous laser Doppler flowmetry to ensure that the remaining bone was viable. Infected nonunions (Cierny stage-IV osteomyelitis) were stabilised by internal fixation. In 38 patients management of dead space required antibiotic-impregnated polymethylmethacrylate beads, which were exchanged for an autogenous bone graft at six weeks. Free-tissue transfer often facilitated soft-tissue coverage. These 93 patients were compared with 22 consecutive patients treated previously who had the same surgical management, but received culture-specific intravenous antibiotics for six weeks. Of the 93 patients, 80 healed without further intervention. Of the 31 Cierny-IV lesions, 27 healed without another operation, and four fractures required additional bone grafts. No more wound drainage was needed. Treatment was successful in 91% of patients, regardless of the organism involved. There was no difference in outcome in terms of these variables when the series were compared. We conclude that the long-term administration of intravenous antibiotics is not necessary to achieve a high rate of clinical resolution of wound drainage for adult patients with chronic osteomyelitis.

Upper extremity replantation.

The most important determinants of the functional ability of an amputated part are proper patient selection and the recognition of vascular compromise. Ideally, a well-performed anastomosis should need no pharmacologic assistance, but the ideal is often the exception. The authors present an empirical approach to use of anticoagulation medication.

Traumatic plastic deformity of an adult forearm: case report and literature review.

We report a case of plastic deformity involving both the radius and the ulna in an adult treated with osteotomy of both bones.

Lateral approach to the humeral shaft: an alternative approach for fracture treatment.

Indications for operative treatment of fractures of the shaft of the humerus have been well described. Anterolateral and posterior surgical approaches are generally preferred for fractures of the proximal/middle thirds and distal third of the humerus, respectively. Each approach has its advantages and disadvantages. We present an alternative, "lateral" approach to the humeral shaft. This approach allows supine positioning of the multiply injured patient and visualization of the radial nerve throughout the extent of the incision, and requires no muscle splitting.

Intra-articular fractures of the distal aspect of the radius.

Intra-articular distal radius fractures are a heterogeneous group of injuries with different fracture patterns. The existing classification systems are helpful for describing the fractures but not for assessing their stability or for deciding which surgical approach to use. Patients who have a fracture with at least 1.0 mm of displacement of the articular surface may benefit from open surgical treatment. Improved diagnostic imaging with CT is helpful for fracture classification and surgical planning. The options for surgical treatment include limited open reduction and internal fixation, arthroscopically assisted internal fixation, and open reduction and internal fixation. The surgical approach is determined on the basis of the initial displacement of the fracture. Patients who have a displaced fracture of the volar rim may benefit from a volar approach; those who have a dorsally displaced fracture, from a dorsal approach; and those who have an impacted fracture such as a die-punch fracture, from a dorsal approach that provides better visualization of the articular surface. The long-term functional outcome is determined in part by the severity of the fracture as defined by the amount of comminution, the initial severity of displacement, and the number of fracture fragments. The accuracy of the reconstruction of the articular surface, with the goal of establishing congruency to within 1.0 mm, is also important in order to minimize the risk of late osteoarthrosis. Of all of the extra-articular parameters, restoration of the length of the radius is the most important for enhancing recovery of motion and grip strength and for preventing problems involving the distal radioulnar joint--the so-called forgotten joint in distal radial fractures.

High-resolution bone scintigraphy of the adult wrist.

Bony anatomic landmarks of the wrist (e.g., pisiform, hook of hamate, radioulnar joint, and styloid processes of the radius and ulna) were routinely identified in 28 adult patients examined for wrist pain. With the wrists prone and immobilized, bone scintigrams were obtained for 500,000 counts with an asymmetric (133 to 161 keV) Tc-99m energy window and either a converging (best choice) or straight-bore, high-resolution collimator. High-resolution scintigraphy precisely localized degenerative joint disease (nine patients), scaphoid fractures (five), pisiform fracture (one), lunate avascular necrosis (one), radioulnar arthritis (one), septic or inflammatory arthritis (six), ulnocarpal impingement (two), and reflex sympathetic dystrophy syndrome (two). Images obtained palm down with the wrist in ulnar deviation helped identify increased uptake within the scaphoid. Fracture and significant bone or joint disease were excluded in one patient.

Successful infiltration of the flexor tendon sheath.

Twenty cadaveric fingers and five thumbs were injected through a midaxial approach, a palmar approach superficial to the flexor tendon, and a palmar approach deep to the tendon, to assess the ability of these approaches to infiltrate the flexor tendon sheath successfully. With care to observe proper positioning of the needle, we were able to achieve essentially equivalent success in infiltration with most of these approaches. However, the midaxial approach to the thumb flexor sheath was unsuccessful.

Management of acute and chronic vascular injuries to the arm and forearm. Indications and technique.

Acute arterial injuries of the upper extremity account for half of civilian arterial injuries in the United States. The great majority of these injuries are due to penetrating trauma, with stab wounds and gunshot wounds being the most common cause. The history of the injury and a careful physical examination will identify most injuries. Arteriography should be performed when a vascular injury is suspected but not confirmed by physical examination. Reconstruction of critical vascular lesions is essential for restoration of flow distally. Noncritical lesions may be repaired in most cases, with long-term patency rates averaging 50% to 68%. Although amputation is uncommon after upper-extremity vascular injury, long-term disability can be significant in those patients with concomitant nerve injury. Chronic upper-extremity ischemia may be secondary to atherosclerotic occlusive disease, aneurysms, or arteriovenous fistulas. Angiography will delineate the diseased or occluded arterial segment, allowing bypass to be successful in more than 90% of cases. With careful attention to proper diagnosis and treatment, good to excellent long-term relief of symptoms can be obtained.