Evaluation of the triangular fibrocartilage and the scapholunate and lunotriquetral ligaments in cadavers with low-field-strength extremity-only magnet. Comparison of available imaging sequences and macroscopic findings.

RATIONALE AND OBJECTIVES: The authors assessed the ability of a low-field-strength extremity-only magnet to provide visualization of the triangular fibrocartilage and the scapholunate and lunotriquetral ligaments. METHODS: Twelve human wrists were examined with a 0.2 T extremity-only magnet. T1-weighted spin echo, proton density-weighted, and T2-weighted turbo spin echo, short-tau inversion recovery, and three-dimensional gradient recalled echo images were acquired, and sections of the specimens were then made that corresponded to the magnetic resonance images. Masked imaging analyses were correlated with macroscopic and limited histopathologic findings. RESULTS: Low-field-strength extremity-only magnet allowed consistent visualization of the triangular fibrocartilage and accurate assessment of a small number of complete tears of the triangular fibrocartilage. The scapholunate ligaments in all cases were identified using a combination of imaging sequences. Consistent visualization of the lunotriquetral ligament with a low-field-strength extremity magnet was difficult. CONCLUSIONS: Magnetic resonance imaging with a low-field-strength extremity-only magnet can be used to visualize the triangular fibrocartilage and the scapholunate ligament, but not the lunotriquetral ligament.

Functional recovery following neurorrhaphy of the rat sciatic nerve by epineurial repair compared with tubulization.

Recovery of motor function is often poor following transection injuries to peripheral nerves. The purpose of this study was to measure and compare functional recovery of the sciatic nerve in the rat following transection and neurorrhaphy with the use of a nerve guide tube and with traditional end-to-end epineurial repair. Muscle recovery was also evaluated following a crush injury, a model of an axonotmetic lesion. Recovery was assessed at 8, 16, and 32 weeks after injury by measuring the isometric contractile properties of the soleus muscle and at 8 and 16 weeks by measuring the conduction properties of the sciatic nerve. The mean conduction velocity of the sciatic nerve in the crush group and both transection groups was significantly slower than that of controls at both 8 and 16 weeks. Following a transection injury, the soleus became a significantly faster muscle as measured by time to peak twitch tension. By 32 weeks, the maximum isometric tension of the soleus muscle recovered to 90% that of the control group following a crush injury and to less than 70% following a transection injury and repair. Recovery was better in the epineurial repair group than in the tube repair group at 8 weeks, but no difference was found between the groups at 16 or 32 weeks. These results demonstrate that nerve guide tubes are a potential alternative to epineurial repair. The poor motor recovery following repair of transection injuries may be related to poor specificity of reinnervation.

Reliability after repeated use of a torque screwdriver employed for halo pin fixation.

It has been recommended that halo torque screwdrivers be used only once. To determine if this advice is justified on biomechanical grounds, five commercially available torque screwdrivers were cycled 1,600 times each in an Instron testing machine over a 7-day period. The screwdrivers displayed an initial error from the dial reading at both 6 and 10 in-lb of only +/- 0.3 in-lb. After cyclic loading and retesting, the percent deviation from original calibration was 8% at both 6 and 10 in-lb. These data demonstrate the accuracy and dependability of the torque screwdrivers and imply that repeated use of these devices should be safe.

Energy cost of ambulation with different methods of foot and ankle immobilization.

In order to measure the energy cost of immobilization of the foot and ankle during ambulation, 14 healthy male volunteers exercised while wearing various immobilization devices. Oxygen consumption, oxygen cost, cardiac output, minute ventilation, heart rate, stroke volume, stride length, and stride frequency were determined at a steady state of exercise as the subjects walked on a treadmill at 80 m/min (equivalent to the comfortable walking speed of approximately 3 mi/h). Each subject was tested with three different types of immobilization devices: a short leg walking cast, a prefabricated lower leg orthosis, and a rigid-soled surgical shoe. The results were compared with those for the same men ambulating without an immobilization device. Ambulation with the short leg walking cast and the prefabricated lower leg orthosis required significantly more energy in comparison with control values (all p values < 0.006) in terms of oxygen cost, cardiac index, oxygen consumption, and minute ventilation. However, when the rigid-soled surgical shoe was worn, energy consumption as measured by all parameters was not significantly increased compared with control values. Comparison of the findings for the short leg walking cast and the prefabricated lower leg orthosis showed no significant differences in any parameter of energy consumption. Stride length, however, was significantly shorter in the short leg walking cast compared with all immobilizers tested.

Effects of local compression on peroneal nerve function in humans.

A new apparatus was developed to compress the anterior compartment selectively and reproducibly in humans. Thirty-five normal volunteers were studied to determine short-term thresholds of local tissue pressure that produce significant neuromuscular dysfunction. Local tissue fluid pressure adjacent to the deep peroneal nerve was elevated by the compression apparatus and continuously monitored for 2-3 h by the slit catheter technique. Elevation of tissue fluid pressure to within 35-40 mm Hg of diastolic blood pressure (approximately 40 mm Hg of in situ pressure in our subjects) elicited a consistent progression of neuromuscular deterioration including, in order, (a) gradual loss of sensation, as assessed by Semmes-Weinstein monofilaments, (b) subjective complaints, (c) reduced nerve conduction velocity, (d) decreased action potential amplitude of the extensor digitorum brevis muscle, and (e) motor weakness of muscles within the anterior compartment. Generally, higher intracompartmental pressures caused more rapid deterioration of neuromuscular function. In two subjects, when in situ compression levels were 0 and 30 mm Hg, normal neuromuscular function was maintained for 3 h. Threshold pressures for significant dysfunction were not always the same for each functional parameter studied, and the magnitudes of each functional deficit did not always correlate with compression level. This variable tolerance to elevated pressure emphasizes the need to monitor clinical signs and symptoms carefully in the diagnosis of compartment syndromes. The nature of the present studies was short term; longer term compression of myoneural tissues may result in dysfunction at lower pressure thresholds.

Kappa Delta Award paper. Tissue fluid pressures: from basic research tools to clinical applications.

The two basic research tools developed to measure tissue fluid pressure (wick catheter) and osmotic pressure (colloid osmometer) have undergone extensive validation and refinement over the past 20 years. Using these techniques, basic science investigations were undertaken of edema in Amazon reptiles, pressure-volume relations in animals and plants, adaptive physiology of Antarctic penguins and fishes, edema in spawning salmon, tissue fluid balance in humans under normal conditions and during simulated weightlessness, and orthostatic adaptation in a mammal with high and variable blood pressures--the giraffe. Following and sometimes paralleling this basic research have been several clinical applications related to use of our colloid osmometer and wick technique. Applications of the osmometer have included insights into (a) reduced osmotic pressure of sickle-cell hemoglobin with deoxygenation and (b) reduced swelling pressure of human nucleus pulposus with hydration or certain enzymes. Clinical uses of the wick technique have included (a) improvement of diagnosis and treatment of acute and chronic compartment syndromes, (b) elucidation of tissue pressure thresholds for neuromuscular dysfunction, and (c) development of a better tourniquet design for orthopaedics. This article demonstrates that basic research tools open up areas of basic, applied, and clinical research.

Anatomical considerations regarding the posterior interosseous nerve during posterolateral approaches to the proximal part of the radius.

BACKGROUND: The purpose of our study was to quantify the dimensions of a surgically safe zone along the proximal part of the radius, from the posterolateral aspect. METHODS: The posterolateral approach between the anconeus and the extensor carpi ulnaris was performed in thirty-two cadaveric specimens, and the posterior interosseous nerve was exposed. Forearms were measured from the radial styloid process to the radiocapitellar joint. The distance from the capitellum to the point where the posterior interosseous nerve crossed the radial shaft and the angle between the nerve and the shaft were measured with forearms in pronation and supination. RESULTS: Pronation of the forearm allowed safe exposure of at least the proximal thirty-eight millimeters of the lateral aspect of the radius, with an average proximal safe zone of 52.0 +/- 7.8 millimeters. Supination decreased this proximal safe zone to as little as twenty-two millimeters and an average of 33.4 +/- 5.7 millimeters. The angle formed by the posterior interosseous nerve and the radial shaft in supination averaged 47.4 +/- 6.8 degrees; this decreased to 27.8 +/- 6.7 degrees with pronation. CONCLUSIONS: Approaching the lateral aspect of the proximal part of the radius is safest in pronation.

Carpal tunnel syndrome. An evaluation of the provocative diagnostic tests.

In order to evaluate the usefulness of provocative tests (wrist-flexion test, nerve-percussion test, and tourniquet test) in the diagnosis of carpal tunnel syndrome, the results of provocative testing were evaluated in a group of patients (sixty-seven hands) with electrodiagnostically proved carpal-tunnel syndrome and in a group of fifty control subjects. The sensitivity and specificity of each test were calculated. The wrist-flexion test was found to be the most sensitive while the nerve-percussion test, although least sensitive, was most specific. The tourniquet test was quite insensitive and not very specific, and should not be used as a routine screening test in the diagnosis of carpal tunnel syndrome.

Application of the halo device for immobilization of the cervical spine utilizing an increased torque pressure.

The rates for loosening and infection of the pins used in the halo apparatus are unfortunately high. The commonly recommended amount of torque to be used in applying the pins is 0.68 newton-meter (six inch-pounds). Forty-two adult patients underwent application of a halo device for immobilization of the cervical spine using an increased torque of 0.90 newton-meter (eight inch-pounds). The rate for loosening of the pins and the rate for infection at the pin site dropped from 36 per cent to 7 per cent and 20 per cent to 2 per cent, respectively.

Results of transfer of the flexor digitorum superficialis tendons to the flexor digitorum profundus tendons in adults with acquired spasticity of the hand.

Thirty-one patients who had transfer of the flexor digitorum superficialis tendons to the flexor digitorum profundus tendons en masse in thirty-four non-functional spastic hands were examined at an average of fifty months postoperatively. All of the patients had had a clenched-fist deformity preoperatively, with severe hygienic problems of the palmar skin and no active function of the hand. Postoperatively, all of the hands were in an open position, which allowed for good hygiene of the palmar surface. A minor wound infection developed in three patients. Neurectomy of the motor branch of the ulnar nerve distal to the Guyon canal was needed for control of spasticity of the intrinsic muscles in twenty-five hands. An intrinsic-minus deformity did not develop in any of the hands that had neurectomy of the ulnar nerve, although an intrinsic-plus deformity developed in seven of the nine hands that did not have a neurectomy.

Complications in the use of the halo fixation device.

The medical records of 179 patients were reviewed to identify complications related to the use of the halo external skeletal-fixation device. The complications that were identified included pin-loosening in 36 per cent of the patients, pin-site infection in 20 per cent, pressure sores under either a plastic vest or a plaster cast in 11 per cent, nerve injury in 2 per cent, dural penetration in 1 per cent, dysphagia in 2 per cent, cosmetically disfiguring scars in 9 per cent, and severe pin discomfort in 18 per cent. One hundred and eighty (25 per cent) of the 716 pins used had become loose at least once, and an infection had developed at sixty-seven pin sites (9 per cent). Two-thirds of the pins that were loose or associated with infection required change or removal. These complication rates, particularly of pin-loosening and infection, are exceedingly high. Attention to details in pin application, pin maintenance, and proper pin-site care may minimize the number of complications.

Subdural abscess associated with halo-pin traction.

Osteomyelitis and intracranial abscess are among the most serious complications that have been reported in association with the use of the halo device. The cases of five patients who had formation of an intracranial abscess related to the use of a halo cervical immobilizer are described. All of the infections resolved after drainage of the abscess, débridement, and parenteral administration of antibiotics. Meticulous care of the pin sites is essential to avoid this serious complication. Additionally, since all of the infections were associated with prolonged halo-skeletal traction, this technique should be used with caution and with an awareness of the possible increased risks of pin-site infection and of formation of a subdural abscess.

Osteology of the skull as it affects halo pin placement.

Twenty-seven cadaver skulls and 20 CT scans of skulls were measured above the orbital rim and ear but below the greatest diameter to determine optimal placement of halo pin sites. At the antero- and posterolateral portions of the calvaria, the outer table averaged 2 mm, the diploe 3 mm, and the inner table 2 mm. At the temporal fossa, the outer cortex averaged 1.7 mm, the diploe 2.0 mm, and the inner table 1.6 mm. Average distance between the anterior edge of the temporal fossa and the frontal sinus approximated 3 cm. These data confirm previously recommended halo pin insertion sites, anterolaterally and posterolaterally, where the bone is thickest and the thinner frontal sinus and temporal fossae are avoided.

Structural behavior of the halo orthosis pin-bone interface: biomechanical evaluation of standard and newly designed stainless steel halo fixation pins.

The structural response of the halo orthosis pin-bone interface to transverse loading was evaluated on an Instron testing machine using fresh cadaver calvarium sections. Commercially available stainless steel (control) pins and newly designed stainless steel experimental pins were evaluated. Cyclic loading tests and load-to-failure tests were performed. Of the many designs tested, one pin demonstrated an improvement in structural properties at the pin-bone interface compared with the control pin. Furthermore, the new pin design was more resistant to insertional torque reduction when subjected to cyclic loading after insertions at 4 and 6 in-lb. Both the control and experimental pins exhibited improved structural behavior at 8 in-lb of insertional torque compared to the currently recommended 6 in-lb.

External fixation of the calcaneus and talus: an anatomical study for safe pin insertion.

Fifteen fresh-frozen adult cadaver feet were dissected to investigate areas in the hindfoot where external fixation pins could be safely inserted with the least risk to underlying nerves, vessels, and tendons. Using palpable anatomic landmarks, four relative "safe zones" on the calcaneus and talus were delineated. These included an area on the medial calcaneus, the medial talus, the lateral calcaneus, and the lateral talus. The medial calcaneal safe zone was a large, easily definable rectangular area on the posterior aspect of the tuberosity, posterior to the neurovascular bundle and extrinsic tendons. The medial talar safe zone was located on the medial talar neck, anterior and superior to the tibialis posterior tendon. The lateral calcaneal safe zone consisted of a large area of the lateral calcaneal tuberosity, located posterior to the peroneal tendons and sural nerve trunk. The lateral talar safe zone included only a narrow, vaguely palpable, quadrangular area on the lateral neck of the talus. The medial safe zones could be easily delineated by palpation and appeared safe for routine unilateral external fixation across the medial hindfoot and ankle. The lateral safe zones appeared safe and useful if both medial and lateral frames were required. The structures most at risk for injury during pin insertion in the zones described were the medial and lateral calcaneal nerve branches, which inconsistently crossed the medial and lateral calcaneal safe zones, respectively. In these areas overlying the tuberosity, however, the subcutaneous tissues were thin, and iatrogenic nerve injury during pin insertion appeared avoidable if blunt dissection was used to reach the calcaneal cortex. The data presented here provide information to assist selection of pin sites that minimize risk to underlying soft tissues during external fixation of the talus and calcaneus.

The deep peroneal nerve in the foot and ankle: an anatomic study.

Injury to the deep peroneal nerve in the foot and ankle may result from trauma, repetitive mechanical irritation, or iatrogenic harm. The nerve is most susceptible to injury along its more distal anatomic course. Dissection of 17 cadaver specimens was undertaken to describe the course of the deep peroneal nerve and quantify its branch patterns. In the distal one third of the leg, the nerve was located superficial to the anterior tibial artery between the tibialis anterior and extensor hallucis longus muscles. Typically, the nerve crossed deep to the extensor hallucis longus tendon to enter the interval between the extensor hallucis longus and extensor digitorum longus at an average distance of 12.5 mm proximal to the ankle. A proximal bifurcation was usually present at an average distance of 12.4 mm distal to the mortise. The lateral terminal branch penetrated the deep surface of the extensor digitorum brevis to provide motor innervation. The medial terminal branch passed over the talonavicular joint capsule, and coursed an average of 2.9 mm lateral to the first tarsometatarsal joint. Within the forefoot, it passed deep to the extensor hallucis brevis tendon, bifurcated in the midmetatarsal region, and then arborized, supplying sensibility to the first toe interspace and the adjacent sides of the first and second toes.

The sural nerve in the foot and ankle: an anatomic study with clinical and surgical implications.

Operative procedures and traumatic injuries of the lateral foot and ankle place the sural nerve and its branches at risk. Anatomic studies quantifying the course of this nerve are sparse. In this study, 17 cadaver specimens were dissected to clarify its course and branching patterns. Despite multiple variations of the nerve and its branches, description of the course of a "typical" nerve trunk was possible. The nerve was found to lie in close proximity to the Achilles tendon at a level of 7 cm above the tip of the lateral malleolus. In the hindfoot, the nerve coursed 14 mm posterior and 14 mm inferior to the malleolus. Distally, it crossed superficial to the peroneus longus and brevis tendons. An anastomotic branch coursing into the sinus tarsi area was observed in 24% of specimens. An understanding of the course and distribution of the sural nerve may lessen the risk of iatrogenic injury.

Management of the adult, spastic, equinovarus foot deformity.

Management of the persistent, acquired, neurogenic equinovarus foot may be a confounding rehabilitative dilemma. Victims of cerebrovascular accidents and traumatic brain injury commonly develop this neurogenic deformity. The plantarflexed and inverted foot position results from an imbalance of forces about the hindfoot due to exaggerated muscle tone and hyperactive stretch reflexes. Significant functional impairment may ensue if a plantigrade foot position cannot be achieved and maintained. Surgical correction may be necessary if conservative measures fail. Determination of the dynamic and static components contributing to the equinovarus deformity is difficult. Gait analysis and dynamic electromyographic studies are valuable adjuncts for operative planning. The wide-ranging goals of surgery vary from improving transfer and ambulation skills, to assisting wheelchair positioning, to facilitating use of braces and/or shoe wear.

Volkmann's ischemic contracture of the foot and ankle: evaluation and treatment of established deformity.

Fibrotic contracture of skeletal muscle can follow weeks or months after the severe ischemic insult of compartment syndrome. Commonly known as Volkmann's ischemic contracture, the affected limb often becomes dysfunctional and painful, and may lose sensibility. The pathogenesis of the muscle contracture includes prolonged ischemia, myonecrosis, fibroblastic proliferation, contraction of the cicatrix, and myotendinous adhesion formation. Resultant shortening or overpull of involved muscles leads to stiffness and deformity. Simultaneously, nerve injury from initial ischemia or subsequent soft tissue fibrotic compression leads to muscle paresis or paralysis of the involved compartment and of those muscles more distally innervated. The resultant deformity is thus a combination of varying degrees of contracture and weakness depending on which muscles and nerves are affected. Deformity and functional impairment in the foot and ankle secondary to ischemia are determined by many factors, including: (1) which leg compartment, if any, has been affected and to what degree extrinsic flexor or extensor overpull is exhibited, (2) degree of nerve injury sustained causing weakness or paralysis of extrinsic or intrinsic foot and ankle muscles (3) which foot compartment, if any, has been affected and to what degree intrinsic overpull is exhibited, and (4) degree of sensory nerve injury leading to anesthesia, hypoesthesia, or hyperesthesia of the foot. Therefore, a variety of clinical presentations can be encountered following compartment syndrome of the leg and foot. Treatment is based on an appreciation of the pathoanatomy of the deformity. Nonoperative therapy is aimed at obtaining or preserving joint mobility, increasing strength, and providing corrective bracing and accommodative footwear. Operative management is usually reserved for treatment of residual nerve compression or severe and problematic deformities. Established surgical protocols are performed in a stepwise fashion, to include: (1) release of residual or secondary nerve compression, (2) release of fixed contractures, using infarct excision, myotendinous lengthening, muscle recession, or tenotomy, (3) tendon transfers or arthrodesis to increase function, and (4) ostectomy or amputation for severe, refractory deformities.

Lengthening the terminal portion of a tendon.

In the operative reattachment of an avulsed or lacerated tendon, additional tendon length is occasionally needed to reach the proposed reinsertion site. This is encountered when there is loss of distal tendon substance or when muscle shortening and tendon retraction has occurred. The following describes a technique of lengthening the terminal portion of the tendon to facilitate reattachment.