A dynamic biomechanical study of scapholunate ligament sectioning

A biomechanical study was performed on fresh cadaver forearms to investigate the role of the scapholunate interosseous ligament in carpal stability. Scaphoid and lunate motion and radiocarpal and ulnocarpal pressure patterns were continually monitored while the wrist was moved physiologically. Prior to ligament sectioning, it was found that the position of the scaphoid and lunate were dependent on both the wrist position and the direction of wrist motion. Sectioning the scapholunate interosseous ligament caused increased scaphoid flexion, scaphoid pronation, and lunate extension. Pressure in the radiocarpal and ulnocarpal joint was redistributed following ligament sectioning. These findings support the clinical impression that the scapholunate interosseous ligament is an important stabilizer of the scaphoid and lunate.

Relative articular inclination of the distal radioulnar joint: a radiographic study

To determine the congruency of the distal radioulnar joint, 100 standardized normal wrist x-ray films were made and the following measurements taken: ulnar seat inclination, sigmoid notch inclination, and ulnar variance. The inclination angles were different in all but two cases. Relative to the long axis of the ulna, the sigmoid notch inclination averaged 7.7 degrees and the ulnar seat inclination averaged 21.0 degrees. There was a moderate correlation between the two inclination angles as well as between both sigmoid and ulnar seat inclination and ulnar variance. The data show that a wide variation between the inclination of the sigmoid notch and ulnar seat exists, which may explain why symptomatic articular incongruity can occur following ulnar shortening.

Lunate morphology: can it be predicted with routine x-ray films?

To assess our ability to predict lunate morphology, x-ray films of 81 cadaver wrists were obtained. The wrists were then dissected to determine true anatomy, specifically the presence or absence of a medial lunate facet. Thirty-five wrists were found to be type 1 lunates, while 46 were type 2. Cartilage erosion at the proximal pole of the hamate was found in association with 28 of the type 2 lunates. The accuracy of determining lunate morphology ranged from 64% to 72%. Therefore, lunate morphology cannot always be reliably predicted by a standard x-ray film. Arthrosis at the lunate-hamate articulation is frequent in association with type 2 lunates.

Biomechanical evaluation of operative procedures to treat Kienböck's disease

Operative procedures used to treat Kienböck's disease have been biomechanically evaluated experimentally. We have shown that joint leveling procedures, such as radial shortening and ulnar lengthening, experimentally unload the ulna and the radial lunate fossa. For wrists with neutral ulnar variance, a lateral opening or medial closing radial wedge procedure unloads the radial lunate fossa. Scapho-trapezio-trapezoidal fusion and scapho-capitate fusion also unload the radial lunate fossa but at the expense of loading the adjacent joints. Neither a capitate-hamate fusion nor a carpal tunnel release alter the radial ulnar carpal joint loading.

Identifying environmental factors harmful to reproduction

Reproduction is essential for the continuation of the species and for life itself. In biological terms, living and reproducing are essentially one and the same. There is, therefore, no sharp division between identifying factors harmful to reproduction and identifying factors harmful to life or vice versa. Detection of harmful factors requires balanced use of a variety of methodologies from databases on structure-activity relationships through in vitro and in vivo test systems of varying complexity to surveys of wildlife and human populations. Human surveys provide the only assured means of discriminating between real and imagined harmful factors, but they are time consuming and provide information after the harm has been done. Test systems with whole animals provide the best prospects for identifying harmful factors quickly, but currently available methods used for testing agrochemicals and drugs need a thorough overhaul before they can provide a role model. Whether there is a need for new methodology is doubtful. More certain is the need to use existing methodology more wisely. We need a better understanding of the environment--whatever it is--and a more thoughtful approach to investigation of multifactorial situations.

The change in ulnar variance with grip

The effect of grip on ulnar variance was evaluated in 66 symptom-free wrists of 53 volunteers. Zero-rotation posteroanterior x-ray films were taken of each wrist before and after exertion of a grip force measured with a Jamar dynamometer. The volunteers were randomly divided into two groups. Group I subjects (35 wrists) were asked to exert a constant grip force of 11.3 kg. Group II subjects (31 wrists) were asked to exert a maximum grip effort, which resulted in a mean grip force of 30 kg (range, 22.8 kg to 53.6 kg). Group I demonstrated a mean increase in ulnar variance of 1.27 mm and group II showed a mean increase of 1.95 mm. The minimum increase in ulnar variance observed was 0.25 mm. The changes observed were statistically significant. The results confirm that a relative increase in ulnar variance occurs with grip. There may be an etiologic role for daily activities that involve repetitive grip and forearm rotation in development of the ulnar impaction syndrome.

Introduction to (pre)screening methods

In summation I start this session with the opinion that in vitro methods cannot be considered as adequate replacements for entire animals at the level of regulatory testing. But, when used to identify mechanisms of action, they can be extremely useful as secondary stage supporting studies. They are of doubtful value for general purpose, broad spectrum screening of single chemical entities or for priority selection of unrelated chemicals. They can be of value for priority selection of homologous series with a known, specific effect on reproduction or development. Such situations are most likely to be present in chemical and drug manufacturing industries where judicious use of in vitro methods in an integrated approach could reduce the number of failures at the later stage of full scale testing. Whether I will need to revise my opinions at the end of this session will depend upon what our speakers have to offer.

The ulnar impaction syndrome: follow-up of ulnar shortening osteotomy

Thirty wrists of 27 patients with ulnar impaction syndrome who underwent ulnar shortening osteotomy were retrospectively reviewed. The average follow-up was 51 months. The wrists were graded preoperatively and postoperatively according to a wrist-grading system modified from Gartland and Werley. The parameters of grading included pain, function, range of motion, grip strength, radiographic analysis, bony union, and complications. Twenty-four wrists were graded excellent, 4 good, 1 fair, and 1 poor after the surgery in comparison with 28 poor and 2 fair before the operative treatment. Complications were rare, with no ulnar nonunions. This long-term follow-up study revealed that distal ulnar shortening osteotomy is an excellent procedure for the treatment of ulnar impaction syndrome.

Anatomic and biomechanical analysis of the arthroscopic wafer procedure

The ulnar impaction syndrome is a common clinical entity that is most often associated with positive ulnar variance and is characterized by triangular fibrocartilage complex (TFCC), lunate, and/or distal ulnar pathology. Traditional treatment for symptomatic ulnar impaction syndrome has been conservative; however, in cases refractory to nonoperative management, formal ulnar shortening has been successful in long-term clinical series. Recently, arthroscopic ulnar shortening, the "arthroscopic wafer procedure" (AWP) (debridement of the perforated TFCC margins and limited ulnar head resection using a motorized burr) has become an option to treat this clinical syndrome. In an attempt to evaluate the biomechanical efficacy of the AWP, an experimental study was undertaken using nine ulnar positive cadaver forearms. Each specimen was evaluated biomechanically using axial load cells and pressure-sensitive film to evaluate the effect of serial resection of the TFCC and distal ulna on axial load and ulnar carpal pressures. The results of this experimental study revealed a statistically significant unloading of the ulnar aspect of the wrist after excision of the centrum of the TFCC and resection of the radial two-thirds width of the ulnar head, to a depth of subchondral bone resection. Furthermore, additional bony resection tended to correlate favorably with the stage of TFCC pathology noted, i.e., the more advanced the stage, the more resection necessary to unload the ulnar aspect of the wrist. Based on this biomechanical study, a limited clinical series has been initiated with early favorable results. The AWP biomechanically unloads the ulnar carpal complex, and therefore has a theoretical potential of relieving the symptoms of the ulnar impaction syndrome.(ABSTRACT TRUNCATED AT 250 WORDS)

Force transmission through the distal ulna: effect of ulnar variance, lunate fossa angulation, and radial and palmar tilt of the distal radius

The relationship between the amount of force transmitted through the distal ulna and seven radiologically apparent anatomic parameters (ulnar variance, radial tilt, palmar tilt, lunate fossa angulation, carpal height, carpal ulnar distance, and ulnar head inclination) was examined in 58 fresh cadaver forearms. A positive, although very weak, relationship was found between the amount of force and the ulnar variance (r = 0.44). This suggests that a clinically more positive ulnar variant wrist will not necessarily cause more force to be transmitted to the head of the ulna than a wrist with a more negative ulnar variance, primarily because the triangular fibro-cartilage complex is thicker in arms with a more negative ulnar variance. Changes in ulnar variance of a forearm due to ulnar lengthening or radial shortening do, however, dramatically alter the force transmission. No other relationships were found between the ulnar force and the other radiologic parameters.

Distribution of pressures and forces on the wrist after simulated intercarpal fusion and Kienböck's disease

Limited intercarpal fusion has been recommended for the treatment of Kienböck's disease. The effects of a simulated scapho-trapezio-trapezoid (STT) fusion and simulated Kienböck's disease on the biomechanics of the radio-ulno-carpal joint were investigated. The percent force, the centroid of the force, and the percent contact area in each fossa were determined. It was found that a STT fusion with the scaphoid in a neutral or extended position unloads the lunate fossa. STT fusion in flexion does not affect lunate load. It is concluded from this biomechanical experiment that STT fusion with the scaphoid in a neutral or extended position unloads the radiolunate joint regardless of the condition of the lunate. This load is shifted to the radioscaphoid articulation.

Radial head fractures and their effect on the distal radioulnar joint. A rationale for treatment

Nineteen patients were treated with open reduction and internal fixation for radial head fractures. Open reduction and internal fixation was performed to avoid radial head excision and the possible development of distal radioulnar joint dysfunction. Follow-up observation, which averaged 11.7 months, revealed that no patient developed wrist pain. Range of motion of the elbow and forearm was found to be complete in 14 patients and minimally restricted in four. Fourteen patients were pain free with full activity, and four had mild to moderate pain after heavy labor. One patient subsequently required radial head excision. Based on these findings and the authors continued disappointment with treatment of distal radioulnar joint dysfunction caused by proximal radial migration after radial head excision, the authors recommend early open reduction and internal fixation of all displaced or angulated radial head fractures.

Long-term results of Swanson interpositional wrist arthroplasty: Part II

Fifty-eight Swanson silicone interpositional wrist arthroplasties were done in 47 patients between 1974 and 1984. Thirty-nine of these original wrists were available for follow-up an average of 5.8 years after operation. This is a continuation of our study previously published in this Journal. With increased follow-up, progressive deterioration of clinical results was noted. With a follow-up of less than 2.5 years, 75% had relief of pain. After a follow-up of 4.8 years, 67% had relief of pain. Finally, with an average follow-up of 5.8 years, only 51% had relief of pain. Progressive radiographic changes are now obvious in each case compared with 70% of those cases reviewed at 4.8 years. Furthermore, we now have noted cystic changes in a significant proportion of the wrists radiographically. In several of these, silicone synovitis has been documented histologically. Our indications for this procedure have drastically narrowed.

The ulnar impaction syndrome

The ulnar impaction syndrome can be defined as the impaction of the ulnar head against the triangular fibrocartilage complex and ulnar carpus resulting in progressive degeneration of those structures. The differential diagnosis in patients who present with ulnar wrist pain and limitation of motion can also include ulnar impingement syndrome and arthrosis or incongruity of the distal radioulnar joint. Structural abnormalities involving the distal radioulnar joint, distal radius, and ulnar carpus must be carefully elucidated prior to developing a treatment plan. When such abnormalities are identified and appropriately addressed, surgical treatment can be expected to be effective in the majority of cases. It is important to remember that in the absence of obvious structural abnormalities, the ulnar impaction syndrome may result from daily activities that result in excessive intermittent loading of the ulnar carpus. In this group of patients, treatment is directed at decreasing ulnar load by shortening the distal ulna in any of several ways. If relative instability of the ulnar ligamentous complex is a factor, then ulnar shortening by recession is the treatment of choice. Malunion of the distal radius resulting in ulnar impaction syndrome is best treated by addressing the deformity; that is, corrective radial osteotomy. Patients who present with a combination of ulnar impaction syndrome along with distal radioulnar joint, abnormalities must have both of these abnormalities addressed at the time of surgery. The matched ulnar resection and the hemiresection interposition arthroplasty are both effective procedures; however, the Suave-Kapandji procedure also can be used to address relative ligamentous laxity at the ulnar aspect of the wrist. The Darrach procedure is presently not recommended as a first-line treatment in these cases; however, when used as a salvage procedure, satisfactory results can be obtained in properly selected patients. Careful preoperative evaluation and planning are therefore the key to successful treatment of the ulnar impaction syndrome.

Wrist arthrography: value of the three-compartment injection method

Arthrography of the wrist was performed on 300 consecutive patients by injecting contrast material separately into the radiocarpal (RCJ), midcarpal (MCJ), and distal radioulnar (DRUJ) joints. The addition of MCJ and DRUJ injections to the standard RCJ injection significantly improved diagnostic yield. In 78 (26%) of the 300 cases, the abnormality was found after MCJ or DRUJ injections alone. Of the 103 triangular fibrocartilage complex (TFCC) abnormalities identified, 27 (26%) could be demonstrated after DRUJ injection alone. Of the 145 abnormal RCJ and MCJ communications, 42 (29%) could be seen after MCJ injection alone. Similarly, 22 (15%) of the 145 abnormal RCJ and MCJ communications were seen after RCJ injection alone and would have been missed if only MCJ injection had been performed. Thus, three separate injections into the RCJ, MCJ, and DRUJ are necessary for complete arthrographic evaluation.

Internal fixation of proximal radial head fractures

The treatment of choice for proximal radial head fractures remains controversial. The goal of any treatment for an intra-articular fracture must be the complete restoration of the joint and its function. Nonoperative treatment leads to full motion in cases of less than 1-2 mm of fracture displacement. Resection of the radial head can be recommended only for very comminuted fractures. All other fracture types should be treated by open reduction and internal fixation. Our own personal follow-up observation of 19 patients who had surgical intervention demonstrated restoration of elbow function after an average follow-up time of 11.7 months. Five patients had a slightly restricted range of motion of less than 10 degrees extension and flexion as well as less than 8 degrees pronation and supination, without signs of arthritis. Because complications were minimal, we recommend internal fixation of displaced proximal radial head fractures to restore the anatomic function of the elbow. This is especially true in cases with accompanying proximal ulna fractures and/or ruptured collateral ligaments of the elbow joint and/or disruption of the distal radio-ulnar joint.

Magnetic resonance imaging of the triangular fibrocartilage complex

Magnetic resonance imaging of seven fresh human cadaveric specimens was used to evaluate the integrity of the triangular fibrocartilage complex of the wrist. A variety of imaging parameters were systematically investigated, including T1-weighted images with and without contrast, long repetition times, short echo time images, and T2-weighted sequences. A variety of imaging planes were also evaluated. Wrist arthrography, dissection, and frozen coronal sections were done to substantiate our interpretations of the magnetic resonance images. T2-weighted images in the coronal plane proved to be of the greatest diagnostic value because the synovial fluid of the joint spaces serves as an excellent endogenous contrast agent. Long repetition time, short echo time sequences could be simultaneously obtained with T2-weighted sequences with the use of a multi-echo pulse sequence to provide an excellent diagnostic package in the future. On the basis of our investigation, the triangular fibrocartilage complex can be consistently and accurately evaluated with magnetic resonance imaging. As magnetic resonance imaging technology improves, wrist probes and suitable magnets should become available that will make the evaluation of triangular fibrocartilage complex abnormalities with magnetic resonance imaging clinically useful.

Triangular fibrocartilage disorders: injury patterns and treatment

On the basis of their arthroscopic experience with the diagnosis and management of acute and chronic lesions of the triangular fibrocartilage complex (TFCC), the authors review the anatomy and biomechanics of the TFCC, classify TFCC injury patterns, and suggest a treatment program for each pattern of injury. Traumatic patterns included central perforations (Class 1A), ulnar avulsions (Class 1B), distal avulsions (Class 1C), and radial avulsions (Class 1D). Degenerative (ulnar carpal abutment) patterns were classified (Class 2A-2E) by degree of severity and progressive involvement of adjacent structures. Arthroscopic debridement of the horizontal portion of the TFCC for Class 1A lesions and the Wafer procedure for Class 2C lesions have proved to be particularly successful over a 2-year follow-up, but the authors advise close long-term follow-up.

Triangular fibrocartilage complex lesions: a classification

Based on anatomic and biomechanical studies and review of our clinical experience of the past 10 years, a classification of injuries to the triangular fibrocartilage complex is presented. This classification is based on the clinical examination, routine x-ray films, wrist arthrograms, wrist arthroscopy, and wrist arthrotomy. The classification recognizes both traumatic and degenerative lesions. Traumatic lesions are classified according to their location. Degenerative lesions are classified by the location and severity of degenerative changes of the triangular fibrocartilage complex, ulnar head, ulnocarpal bones and lunotriquetral ligament.

Frequency spectrum analysis of wrist motion for activities of daily living

A frequency spectral analysis was performed on wrist motion data for 24 activities of daily living (ADLs). Wrist motion was measured using a triaxial electrogoniometer attached to the wrist using tape (for 12 subjects) and pins (for one subject). Results show that the average predominant frequency component of these ADLs was approximately 1 Hz with 75% of the spectral energy less than 5 Hz. The taped-on electrogoniometer, when compared with the pinned electrogoniometer, was adequate for calculating the predominant frequency component and spread of spectral data, but overestimated the magnitudes of the maximum spectral density and total area of the spectral curves. This discrepancy was largest for axial rotation.

Pressures in the distal radioulnar joint: effect of surgical procedures used for Kienbock's disease

Radial shortening and ulnar lengthening are two accepted surgical methods for treating Kienbock's disease. The effect of these procedures on the pressure within the distal radioulnar joint between the ulnar head and the sigmoid notch of the radius was experimentally evaluated in six fresh cadaver forearms. Radical shortening and ulnar lengthening led to increased pressure at the distal radioulnar articulation and caused shifting of the location of the center of pressure distally within the sigmoid notch. Radial displacement of the distal radial fragment at the time of radial shortening, however, decreased the peak pressures. Based on these experimental data, ulnar lengthening and radial shortening can be expected to alter the normal biomechanics of the distal radioulnar joint.

Wrist pain and distal growth plate closure of the radius in gymnasts

Three cases in which wrist pain developed in skeletally immature competitive gymnasts are presented. In all three cases there is radiographic evidence of premature growth plate closure, resulting in shortening of the radius and alterations in the normal distal radioulnar articulation. Repetitive compressive loading of the distal growth plate of the radius is proposed as a potential etiology of this condition. Treatment goals, including an example of successful ulnar shortening, are reviewed. The authors suggest activity limitation with the onset of symptoms, in order to avoid the permanent structural changes observed in our patients.

Triquetral-lunate arthritis secondary to synostosis

Until recently the problem of painful, symptomatic arthritis of the wrist secondary to congenitally incomplete separation of carpal bones has been infrequently recognized. Five patients with either excessive stress loading or trauma had eight symptomatic wrists with congenitally incomplete separation of the triquetral-lunate joint. Three of these patients had bilateral symptoms. Six of the wrists had been treated by a limited wrist arthrodesis of the triquetral-lunate joint resulting in asymptomatic wrists and improved range of motion. It appears that patients with this congenital condition poorly tolerate stress loading or trauma secondary to deficient intra-articular cartilage formation resulting in a clinical and anatomic state similar to degenerative arthritis. We suggest a limited wrist arthrodesis as definitive treatment for symptomatic congenitally incomplete separation of the triquetral-lunate joint, with possible application in incomplete separation of the other intercarpal joints.

The triple-injection wrist arthrogram

The last 100 patients to have wrist arthrography at our institution had, in addition to the standard radiocarpal joint injection, injections into the distal radioulnar joint and midcarpal joint. Seventy-seven of the 100 patients had abnormal arthrograms. In 29 cases abnormalities not identified by the radiocarpal joint injection were demonstrated either by the distal radioulnar joint or the midcarpal joint injection. In 38 patients abnormalities shown by radiocarpal joint injection were not demonstrable by the other two injections. Seven detachments of the triangular fibrocartilage complex from the ulnar styloid could be demonstrated only by the distal radioulnar joint injection. The midcarpal joint injection was far more useful than the radiocarpal joint injection in the evaluation of radiocarpal joint-midcarpal joint communications. All three injections appear to be necessary for a complete arthrographic evaluation.

Fractures and dislocations of the distal radioulnar joint

Fractures and dislocations of the distal radioulnar joint are frequently visualized as a secondary problem in comparison to the more apparent radius fractures. Frequently, in the long-term follow-up of patients with radius fractures, ulnar wrist pain secondary to distal radioulnar joint incongruity is the final outcome. Therefore, in the evaluation of the injured forearm the distal radioulnar joint must be assessed clinically and radiographically. In this assessment if distal radioulnar joint instability or incongruity is present then joint stabilization or reduction, respectively, must be attained.

Partial excision of the triangular fibrocartilage complex

A cadaver model was used to evaluate the effect of partial excision of the triangular fibrocartilage complex (TFCC) on ulnar wrist kinetics. Excision of less than two thirds of the horizontal portion of the TFCC was found to have no statistical effect experimentally on forearm axial load transmission. This data supports, from a biomechanical standpoint, partial excision of the central portion of the TFCC--a procedure advocated clinically by some for treatment of a central TFCC perforation.

Chronic ulnar wrist pain secondary to partial rupture of the extensor carpi ulnaris tendon

An unusual case of symptomatic partial rupture of the extensor carpi ulnaris (ECU) tendon after trauma is described. The patient was successfully treated by surgical removal of a prominent ulnar ridge, debridement of the ECU tendon, and ECU subsheath reconstruction. Extensor carpi ulnaris subluxation and partial rupture should be considered in the differential diagnosis of a patient with chronic ulnar wrist pain.

Wrist arthrography: the value of the three compartment injection technique

Arthrography of the wrist was performed on 50 consecutive patients with obscure post-traumatic wrist pain by injecting contrast separately into the radiocarpal joint, midcarpal compartment, and distal radioulnar joint. When distal radioulnar joint and midcarpal compartment injections were added to the standard radiocarpal injection, many significant unsuspected abnormalities were identified. Of the 25 triangular fibrocartilage complex abnormalities identified, six (24%) were found only with the distal radioulnar joint injection. Of the 29 abnormal communications between the midcarpal compartment and the radiocarpal joint, ten (35%) were found only with the midcarpal injection. Similarly, five of 29 (17%) of the abnormal radiocarpal-midcarpal communications would have been missed if a midcarpal injection alone had been performed. These findings indicate that separate injections into the radiocarpal joint, midcarpal compartment, and distal radioulnar joint are needed to identify a large number of abnormalities not seen with injections into one compartment alone.

A biomechanical study of distal radial fractures

In an attempt to explain disability in dorsally angulated malunited distal radius fractures, an experiment was designed to evaluate load patterns about the wrist with varying degrees of dorsal angulation of the distal radius. Osteotomies were made in the distal radius of fresh cadaver arms after a modified external fixator was applied to the radius and load cells applied to the proximal radius and ulna. Pressure-sensitive film was inserted into the radioulnar carpal joint. After a predetermined load was applied to the wrist it was found that the load through the ulna increased from 21% to 67% of the total load as the angulation of the distal radial fragment increased from 10 degrees of palmar tilt to 45 degrees of dorsal tilt. The pressure distribution on the ulnar and radial articular surfaces changed in position and became more concentrated as dorsal angulation increased.

The distal radioulnar joint. Anatomy, biomechanics, and triangular fibrocartilage complex abnormalities

The distal radioulnar joint plays an intricate part in the function of the wrist and thus in the function of the entire upper extremity. The radius and hand move in relation to and function about the distal ulna. Significant loads are transmitted to the forearm unit through the distal ulna via the triangular fibrocartilage complex. The anatomic relationships between the distal radius and ulna and ulnar carpus are precise, and even minor modification in these relationships leads to significant load changes and resultant pain syndromes. Evaluation of a patient with ulnar wrist pain is, at best, difficult. Despite a careful and thorough history and physical examination and the use of sophisticated ancillary diagnostic studies, some patients with distal radioulnar joint and ulnar carpal complex problems remain diagnostic and therapeutic mysteries. These patients are best followed; exploratory surgery is rarely satisfying to either the patient or the surgeon. Armed with an understanding of the normal anatomy and biomechanics, the examination of such a patient and subsequent treatment should become a challenge that is rewarding for both patient and treating physician.

An indirect assessment of the Chernoff/Kavlock assay

The underlying principle of the Chernoff/Kavlock assay--namely that prenatal toxicity can be detected by means of simple postnatal endpoints--is strongly supported by experience gained in performing reproductive and developmental toxicity studies to international requirements. Compared with the supposedly more sophisticated procedures of regulatory tests, the simpler endpoints of the assay offer greater speed, economy, consistency and reliability. At the most, there is only a marginal loss of sensitivity in respect of detecting the lowest dosage at which effects may occur. The assay is best used as a concept rather than as a protocol with, "tailored" variations providing effective means of priority selection from a series of chemicals, especially analogue series. The underlying principle is applicable at levels through and beyond formal regulatory testing.

Digital tourniquets: a pressure study with clinical relevance

This study measured the pressures under the three most commonly used digital tourniquets--the Penrose drain, the rolled rubber glove, and the rubber band. A miniature pressure transducer and a digital strain indicator were used to measure pressures generated by the various tourniquets. The rolled rubber glove technique was highly consistent, irrespective of the clinical experience of the subject, and uniformly generated pressures of less than 500 mm Hg. Pressures generated by Penrose drains and rubber bands were highly variable and were significantly greater than 500 mm Hg. The so-called calibrated Penrose drain generated the highest pressures in the study. The relationship between tourniquet pressures and neurovascular injury in the human digit is not clearly defined.

Force transmission through the distal radioulnar carpal joint: effect of ulnar lengthening and shortening

Although numerous surgical procedures are performed on the wrist joint, little has been written regarding the effect of these procedures on the biomechanics of the wrist. This study has been undertaken to examine the in vitro consequences of ulnar lengthening and shortening. We have measured the axial forces transmitted through the distal radius and ulna and the pressure distribution on the articulating surface of the radius and triangular fibrocartilage complex for the intact wrist, with ulnar lengthening and with ulnar shortening. Lengthening of the ulna by 2.5 mm in the intact wrist increased the force borne by the ulna from 18.4% to 41.9% of the total axial load. Shortening of the ulna by 2.5 mm decreased axial load borne by the ulna to 4.3%. Removal of the articular disc portion of the triangular fibrocartilage complex decreased the load on the intact ulna from 18.4% to 6.2%. The peak pressure at the ulnolunate articulation increased from 1.4 N/mm2 for the unaltered wrist to 3.3 N/mm2 when the ulna was lengthened by 2.5 mm. These results suggest that the biomechanics of the wrist joint can be dramatically altered with relatively small (2.5 mm) changes in ulnar length and by removal of the articular disc portion of the triangular fibrocartilage complex.

Injuries to the distal radioulnar joint

Disorders of the distal radioulnar joint can be divided into those secondary to ligamentous injuries, fractures, and arthritis changes. Further classification of the first two categories relates to acute versus chronic problems. Acute radioulnar joint disruption can, for the most part, be diagnosed on the basis of early physical examination, radiographic evaluation, and a high index of suspicion. Early recognition and the institution of satisfactory treatment are the hallmarks of a successful result. Those injuries seen after 8 weeks can be termed chronic problems, and further diagnostic evaluation beyond physical examination and routine radiographs includes wrist arthrography, arthroscopy, tomograms, and CT scans. These disorders are certainly much more difficult to treat; however, a systematic assessment with a full knowledge of the anatomy and biomechanics is helpful in preventing arthritis as the late sequela of distal radioulnar joint abnormality. Surgical treatment may be necessary in many of these situations but must be tempered to the needs and demands of the individual patient.

Biomechanical analysis of internal fixation techniques for proximal interphalangeal joint arthrodesis

Although numerous fixation techniques have been developed for performing small joint arthrodesis, no previous study of the biomechanical properties of these constructs has been published. The strength of specimens of arthrodesis of the proximal interphalangeal joint performed with cadaver material was determined for three-point anteroposterior bending, axial torsion, and lateral cantilever bending stress. Crossed Kirschner wires, intraosseous wiring, and figure of eight tension-band wiring were studied. Figure of eight tension-band wiring demonstrates superior strength in anteroposterior bending and torsion. For lateral bending stress, no significant difference exists among the techniques studied.

Complications from tourniquet use

Complications of tourniquet use are rare, but when they do occur, they may be devastating. This article outlines potential complications of tourniquet use and recommends measures that can be taken by clinicians using this valuable and potentially dangerous tool.

The long-term results of Swanson silicone rubber interpositional wrist arthroplasty

Fifty-three Swanson silicone rubber interpositional wrist arthroplasties were done in 42 patients. A painful rheumatoid wrist was the most common operative indication. Very acceptable clinical results were obtained early in follow-up, with more than 90% of the wrists obtaining significant pain relief. However, in the group of wrists followed for more than 2.5 years, only 61% had good or excellent results. The reoperation rate in this group was 25%. Postoperative complications included prosthetic breakage (9.4%), ulnar cap breakage (71%), and a very high incidence of progressive radiographic deterioration (70%).

The toxicity of beta-carotene

The safety of beta-carotene, a widely distributed food colorant was assessed in tests with cells and in sub-chronic and chronic experiments with animals. Mutagenicity evaluations which included the standard Ames test and the micro-nucleus test of bone marrow cells from mice showed that beta-carotene exerted no mutagenic properties. Embryotoxicity studies in rats and rabbits showed that there was no evidence of embryotoxicity and a multiple generation study in rats showed that there was no interference with the reproductive function in rats given oral doses of up to 1000 mg/kg/day. Chronic toxicity was studied in a 2-year study with dogs in a toxicity/tumorigenicity study in rats and in a mouse carcinogenicity study. Histological findings in the livers of treated dogs and mice, but not in rats, included vacuolated cells with eccentric nuclei which were distributed in periportal areas and which were frequently associated with minimal lipid deposition. There was no evidence that the vacuolisation was dose-related. It was considered that the vacuolated cells were fat storage cells. There was no effect on the tumor profiles in the rat and the mouse studies.

The scaphotrapezial ligament complex: an anatomic and biomechanical study

An anatomic and biomechanical study of the ligamentous stabilizers of the scaphotrapezial trapezoidal joint was performed in 25 fresh cadaver specimens. A consistent scaphotrapezial ligament complex consisting of four entities was identified. This complex is comprised of a stout scaphotrapezial ligament on the radial and palmar aspects of the scaphotrapezial joint, weak palmar and dorsal capsules, and a scaphocapitate capsular ligament. A biomechanical study subsequently found that these structures were directly related to resisting diastasis of the scaphotrapezial trapezoidal joint. This information is helpful in understanding scaphoid tuberosity fractures, scaphotrapezial instability and arthrosis, scaphoid dislocations, and perhaps scapholunate disassociations.

Radiography and computerized tomography in the diagnosis of incongruity of the distal radio-ulnar joint. A prospective study

The diagnosis of subluxation or dislocation of the distal radio-ulnar joint may be difficult to confirm by routine radiographs. We undertook a prospective evaluation of fifteen patients with acute or chronic pain in the distal radio-ulnar joint, using both standardized radiographs and computer assisted tomography. In the absence of a deformity of the distal end of the radius, a lateral radiograph made with the wrist in the neutral position accurately revealed incongruency of the distal radio-ulnar joint. When pain or cast immobilization prevented optimum positioning of the wrist for radiography, or when a deformity of the distal end of the radius was present, computer assisted tomography gave a more accurate determination of the congruency of the joint.

The extensor retinaculum of the wrist: an anatomical and biomechanical study

Through an anatomical and biochemical study, utilizing sixty-five cadaver specimens, the extensor retinaculum of the wrist was examined. It is a complex variable fibrous structure, whose functions are to prevent dorsal bowstringing of the extensor tendons and to prevent radial and ulnar displacement of extensor tendons. We recommend that a portion of the extensor retinaculum be preserved or reconstructed at the time of dorsal wrist surgery.

Functional wrist motion: a biomechanical study

A triaxial electrogoniometer was used to measure functional wrist motion. Wrist motion was evaluated in 10 normal subjects who performed 52 standardized tasks. The wrist joint was found to have three degrees of freedom (flexion-extension, radioulnar deviation, and rotation). The normal functional range of wrist motion is 5 degrees of flexion, 30 degrees of extension, 10 degrees of radial deviation, and 15 degrees of ulnar deviation.

Teratology and reproduction studies with triclopyr in the rat and rabbit

Triclopyr (3,5,6-trichloro-2-pyridyloxyacetic acid), being developed as a new herbicide for use on brush and weeds, was evaluated for its potential effects on reproduction, and embryonal and fetal development. Pregnant Sprague-Dawley rats were given doses of 0, 50, 100, or 200 mg/kg/day by gavage on Days 6 through 15 of gestation. Dose-related signs of maternal toxicity were observed during the treatment period. No teratogenic effects were observed at any dose level, though slight fetotoxicity, possibly secondary to maternal toxicity, occurred at the high dose level (200 mg/kg/day). Pregnant New Zealand White rabbits were given doses of 0, 10, or 25 mg/kg/day by gavage on Days 6 through 18 of gestation which produced transient, dose-related decreases in maternal body weight gain. However, there were no indications of any treatment-related effects on fetal growth and development among rabbits. Male and female Sprague-Dawley rats maintained on diets supplying 0, 3, 10, or 30 mg/kg/day over three generations exhibited no consistent treatment-related effects on reproductive performance, pregnancy, parturition, or neonatal survival. These data indicated that triclopyr had little or no potential for teratogenic or reproductive toxicity even when the level of exposure approached that which elicited maternal toxicity.

Relationship between ulnar variance and triangular fibrocartilage complex thickness

The thickness of the thinnest aspect of the articular disc portion of the triangular fibrocartilage complex (TFCC) was experimentally measured and compared with ulnar variance. There is an inverse relationship between positive ulnar variance and TFCC thickness.

Biomechanics of the distal radioulnar joint

The distal radioulnar joint is an intricate part of wrist function. The radius and hand move in relation to, and function about, the distal ulna. Significant loads are transmitted to the forearm unit through the distal ulna via the triangular fibrocartilage. The anatomic relations between the distal radius and ulna and the ulnar carpus are precise, and even minor modifications in these relations leads to significant load-pattern changes. The authors can only speculate on the clinical ramifications of such load-pattern modifications. Since M. DeSault's dissertation on dislocation of the distal radius, published in 1791, much has been written on injuries to, and afflictions of, the radiocarpal area. Although injuries and afflictions in this area undoubtedly have not changed throughout the years, an increasing variety of ulnar wrist syndromes and treatment programs are being recognized. This phenomenon attests not only to the need for continuous investigations of wrist problems but also to the great excitement that presently exists in the field. Better understanding of the anatomy and newer knowledge of the biomechanics of the distal radioulnar joint should herald an ulnar wrist renaissance.