Biomedical subjects

A K Palmer

Publications and source records attributed to A K Palmer.

At least 19 recordsLinked to original sources

PubMed1992

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.

Analysis of Variance↗

PubMed1992

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.

Arthrodesis↗

PubMed1992

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)

Arthroscopy↗

PubMed1992

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.

Adolescent↗

PubMed1991

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.

Arthritis↗

PubMed1991

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.

Adolescent↗

PubMed1991

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.

Biomechanical Phenomena↗

PubMed1990

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.

Arthroscopy↗

PubMed1990

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.

Cartilage, Articular↗

PubMed1990

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.

Adolescent↗

PubMed1989

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.

Activities of Daily Living↗

PubMed1989

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.

Aged↗

PubMed1989

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.

Adult↗

PubMed1989

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.

Biomechanical Phenomena↗

PubMed1988

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.

Adolescent↗

PubMed1988

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.

Biomechanical Phenomena↗

PubMed1988

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.

Adolescent↗

PubMed1987

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.

Animals↗