Heat generation during ulnar osteotomy with microsagittal saw blades.

Ulnar shortening osteotomy is a surgical treatment option for patients with symptomatic ulnar positive variance for a variety of reasons. Delayed healing and nonunion of the osteotomized sites have been reported and present problematic complications of this procedure. Studies have shown nonunion rate with transverse cuts ranging from 8-15%. The goal is to achieve parallel cuts, thus maximizing the contacting bony surface area for a better union rate. The senior surgeon attempted using a custom thick blade to insure parallel cuts. The concern is whether the heat generated during such a cut would contribute to non-union. It is our hypothesis that complications with ulnar shortening osteotomy using a thick blade are secondary to excess heat generation. When generated heat surpasses the threshold temperature of bone tissue, the organic matrix is irreversibly damaged and necrosis of the bony ends may occur. The present study measured the heat generation during ulnar osteotomy using different blade thicknesses. Thirty-five fresh turkey femurs, having similar size and cortical thickness of the human ulna, were used. Loading was done at three different speeds of 0.66, 1.0, and 1.5 mm/second corresponding respectively to 30, 20, and 10 seconds for the complete cut. A general linear statistical model was fitted relating temperature rise to three predictive factors: blade thickness, sensor distance, and initial bone temperature. There was a statistically significant relationship between temperature rise and all three predictor variables at the 99% confidence level. There was no statistically significant relationship between temperature rise and the number of cuts with the same blade up to 10 times. Compared with the single microsagital saw blade, the temperature rise for the double thickness blade was 14% higher and for the triple thickness blade was 23% higher. The temperature rise was inversely related to the speed of the cut. The temperature rise for the bone cut in 30 seconds was 1.5 times higher than the temperature rise when the bone was cut in 10 seconds. Complications with ulnar shortening osteotomy may be secondary to excess heat generation. A new thick saw blade design and the use of proper internal/external irrigation may overcome the problem.

Etiology of Dupuytren's disease.

The etiology of Dupuytren's disease is still unknown in spite of significant recent advances in identifying the type of cell responsible for initiating the process. Associated factors such as alcoholism, smoking, work, diabetes, and epilepsy are discussed. The course of the disease in men as compared with women is also discussed. Recent evidence has shown that there may be genetic and immunologic factors involved. Superoxide free radicals and their effect on fibroblast proliferation may play a significant role in the disease process.

Kienbock's disease: treatment by implantation of vascular pedicle and bone grafting.

Eleven patients with stage II and IIIA Kienbock's disease treated with vascular pedicle implantation and bone grafting were reviewed to determine the long term efficacy of the procedure. Eight wrists had a negative ulnar variance and three wrists had a neutral ulnar variance. The procedure involved implanting the second dorsal metacarpal artery and its venae commitantes into a hole made in the lunate through a dorsal approach. Cancellous bone graft from the dorsal aspect of the distal radius was loosely packed in the hole to secure the pedicle. Follow-up was from 37 to 140 months with an average of six years. Nine patients had significant long term pain relief, improved function, and required no additional procedures. In two patients, continued pain necessitated proximal row carpectomy at two and 4.5 years postoperatively. Ten of the eleven patients had no worsening of their radiographic staging, but in no patient was the architecture of the lunate restored. There were no complications. The results are promising enough to recommend consideration of this procedure in the early stages of Kienbock's disease in patients with a neutral or negative ulnar variance.

Wrist arthrodesis. Technique and functional evaluation.

Wrist arthrodesis is a reliable procedure that, although it sacrifices motion for stability, provides the patient with relief from pain. This review of 26 wrist arthrodeses performed in 24 patients using the AO technique, with plate and screw fixation and iliac crest bone graft, shows a 100% union rate and high patient satisfaction. Using a questionnaire, the patients revealed that they adapted to their fused wrists but still had difficulty with some activities, such as getting the hand into tight places, heavy lifting, and positioning the hand for some specific activities. The most common complication was fracture at the ends of the plate. Removal of the plate after solid healing of the fusion is recommended strongly.

Late presentation of triceps rupture. A case report and review of the literature.

Rupture of the triceps tendon is a rare injury. The treatment protocol for acute injuries is well described and predictably successful. However, if the diagnosis is missed, the surgeon is presented with a more difficult management problem. We report the case of a 19-year-old woman who presented 8 months following a triceps tendon rupture. The diagnosis and technique for repair and postoperative rehabilitation are described. A review of the literature is also presented. Although our patient regained excellent motion and function, we feel the injury is best managed by avoiding misdiagnosis via a high index of suspicion and a careful examination at the time of injury.

Staple leg profile influence on pullout strength: a biomechanical study.

Bone staples have widespread applicability in orthopaedic surgery. Their use, however, is limited by inconsistent quality of fixation. Prior studies have shown potential for improvement in the reliability of staple fixation through a change in the design of the staple legs. To identify a superior leg cross section profile, pullout strength of 5 different newly designed staple leg cross sections were evaluated in fresh frozen human cadaveric bones before and after toggle loading. The tests were repeated in a synthetic bone model with variable but consistent densities. The curvilinear square profile had the highest pullout strength in both the cadaveric and synthetic bone, followed in descending order by square, circular, and triangular profiles. Controlling for density, the pullout strength of the curvilinear square profile was 8% higher than the square profile and 34% higher than the circular profile. The triangular profiles had the least resistance to pullout force before and after cyclic loading. The curvilinear square may be the best profile for the cross section of the staple leg for maximum pullout strength and may expand the clinical use of staples in bone fixation.

Internal fixation of oblique metacarpal fractures. A biomechanical evaluation by impact loading.

Internal fixation of oblique metacarpal fractures was studied in a cadaver model by impact loading. One hundred twenty fresh-frozen human metacarpals underwent compressive and bending impacts after oblique osteotomy and internal fixation. Dorsal plating with lag screws, 2 dorsal lag screws (2-screws), crossed Kirschner wire tension band (crossed K-wire), 5 stacked intramedullary Kirschner wire (5-rod), and paired intramedullary Kirschner wire (2-rod) were used. The failure occurred within 6 msec in the compressive impact and was almost immediate in the bending impact. The dorsal plate and the intramedullary rod fixations were the strongest and were not significantly different from the intact specimens in compressive impact; they were, however, 19% weaker in bending impact. The 2-screws was the weakest fixation in this group. This fixation was 59% weaker in compressive impact and 47% weaker in bending impact compared with the dorsal plating.

Heterotopic ossification.

Heterotopic ossification is a well-recognized condition frequently encountered by the orthopedic surgeon. Although typically asymptomatic, heterotopic ossification can be a complication of extreme severity. This article is a review of literature and attempts to clarify the definition, and delineates the etiology, incidence, risk factors, and current modes of prophylaxis and treatment of various types of heterotopic ossification.

Vascular injuries associated with elbow fractures and dislocations.

The association between elbow fractures and dislocations and vascular injury was reviewed at our institution over a ten year period from 1983 to 1993. A total of fifty-six cases of acute elbow fracture or dislocation which required operative treatment were reviewed and of these two had a concomitant vascular injury. In both these cases diagnostic imaging studies confirmed the clinical diagnosis and arterial reconstruction was done. These cases are reviewed along with the arterial anatomy about the elbow which allows for significant collateral circulation. The general principles of fracture or dislocation reduction followed by vascular reassessment and arterial reconstruction if needed are reviewed.

Mechanics of retrograde nail versus plate fixation for supracondylar femur fractures.

Two common types of internal fixations for the supracondylar femur fractures--the retrograde intramedullary nail and the 95 degrees sideplate and screw--were mechanically tested in synthetic composite femur bones to determine the quantitative differences in their inherent rigidity. The medial and lateral femoral condyles were separated by a sagittal osteotomy, and a standardized medial segmental shaft defect was created at the distal shaft. The osteotomized specimens were stabilized using one of the two implants and were tested in different modes of loading. The bending stiffness of both constructs were not significantly different in varus compression, medial bending (pure varus), and bending in flexion. The plate and screw implant was three times stiffer in lateral bending (pure valgus) and 1.2 times stiffer in valgus compression than the retrograde supracondylar nail (p < 0.01). The torsional stiffness of the plate and screw implant was significantly higher, 1.6 times that of the nail. Clinically, the most important and common cause of implant failure is varus loadings due to loss of medial cortical contact. Although the retrograde nail was less rigid in other physiologically less critical modes of loading, it had a rigidity comparable to that of the plate in varus loading. Therefore, a supracondylar nail may be considered a mechanically possible alternative to plate fixation.

Acute gamekeeper's thumb. Quantitative outcome of surgical repair.

Ten consecutive patients with 11 complete ulnar collateral ligament tears who had early surgical repair were evaluated at an average of 42 months' followup. The mean arc of motion at the metacarpophalangeal joint at 50.9 degrees was less than the 73.7 degrees seen in the uninjured thumbs. At the interphalangeal joint, the mean arc of motion in the injured thumb was 101.6 degrees compared with 112.6 degrees on the uninjured side. Ulnar laxity was decreased slightly compared with the contralateral thumb (14.0 degrees versus 15.3 degrees) and radial laxity was 10.3 degrees on both sides. The mean grip strength and key pinch were similar between the injured and uninjured sides: grip strength was 32.3 kg in the injured thumbs and 34.0 kg in the uninjured; key pinch was 8.1 kg in the injured thumbs and 8.8 kg in the uninjured. Good stability with slight decrease in motion was obtained in our patients.

Anomalous hand muscle found in the Guyon's canal at exploration for ulnar artery thrombosis. A case report.

A diagnosis of ulnar artery thrombosis should be considered when a patient reports symptoms of ulnar neuropathy, ischemia in the hand, or a mass in the hypothenar area. A history of repetitive blunt trauma to the hypothenar area is particularly suggestive of this. Ulnar artery thrombosis is possibly associated with an anomalous muscle in the Guyon's canal. The anomalous muscle in this case originated on the flexor carpi ulnaris muscle, was ulnarly innervated, and joined the flexor digiti minimi muscle distally. This patient had a history of blunt injury and a significant smoking history, thus, a causal relationship between the anomalous muscle and ulnar artery thrombosis cannot be stated with certainty.

Mangled extremity severity score: an accurate guide to treatment of the severely injured upper extremity.

The mangled extremity severity score (MESS) is a scoring system that can be applied to mangled extremities and help one determine which mangled limbs will eventually come to amputation. The MESS is a graduated grading system based on skeletal and soft tissue injury, shock, ischemia, and age. The records of 37 patients having sustained 43 open fractures or mangled upper extremity injuries, seen and treated at the University of New Mexico's Regional Trauma Center between April 1987 and September 1990, have been reviewed. All nine extremity injuries with a MESS of greater than or equal to seven were amputated, and 34 of 34 with a MESS of less than seven were salvaged. Nine Grade IIIC and six mangled extremities were identified in our study. Five of these Grade IIIC and four of the mangled extremities with a MESS of greater than or equal to seven were amputated. All Grade IIIC or mangled extremities with a MESS of less than seven were salvaged. In conclusion, the MESS is an early and accurate predictor for identifying the extremities that may be best treated by amputation.

The reduction clamp: a simple device for closed reduction during intramedullary nailing.

Reduction of femoral shaft fractures prior to passing the guide pin during intramedullary fixation may be a challenging problem, especially in delayed reductions or obese patients. We describe a simple and useful instrument for obtaining and maintaining reduction for closed intramedullary fixation. It provides a three-point fixation that may be locked into position to maintain the reduction. The surgeon is not required to hold the device in position while passing the guide pin, the reamer, or the nail. It frees the surgeon's hands, minimizes the need for an assistant, and reduces harmful x-ray exposure to the hands.

Hemodynamic comparison of microsurgical repairs for large arterial defects.

Twenty-eight femoral arteries in 14 rats were used to compare transverse closures and end-to-end anastomoses in blood vessels approximately 1 mm in diameter. The transverse closures were applied to arteriectomies created by excising one-half the circumference of the vessel over a length of 1 mm. The end-to-end anastomoses were performed after resecting a 1-mm segment. Recordings were made of pre- and postrepair flow velocity and three-point diameter measurements every 5 minutes using a 20-MHz pulsed Doppler velocimeter and digimatic caliper. Maximum reductions in flow velocity were 18% and 31% for the transverse repair and end-to-end anastomosis, respectively. Otherwise, intergroup comparisons of the postrepair normalization of both flow velocity and vessel diameter showed few significant differences (P < 0.05). We conclude that arterial defects involving no more than half the diameter of the vessel can be effectively repaired in significantly less time using the transverse closure.

Isokinetic dynamometric technique for spasticity assessment.

This study was conducted to determine the feasibility of quantifying spasticity by measuring the resistance to passive movement using an isokinetic dynamometer. A quantifiable method was developed by determining the summation of the four consecutive resisting torque amplitudes during flexion and extension of the knee at specified speeds and range of motion. A more rigorous assessment was made by finding the slope of the linear regression curve of torque-velocity data. Although the values of maximum torque were higher in the spastic group than in the normal group, the difference was statistically significant only when the sum of the torque amplitudes was considered (P < 0.0028). Values of the maximum torque as well as the sum of the torque amplitudes increased in a linear fashion (r > 0.75) with increasing velocity. The slopes of the torque-velocity curves were greater in spastic subjects than in normal subjects. The sensitivity to the rate of stretch was statistically greater (P < 0.0004) for the spastic group than normals only when the sum of torque amplitudes was considered. The corresponding data obtained during the flexion and extension of the knee were not statistically different (P > 0.05). Serial summation of torque amplitudes and measurement of slope in the torque-velocity curve are sensitive and repeatable methodologies for the measurement of spasticity assessment.

Comparative fatigue strengths and stabilities of metacarpal internal fixation techniques.

To study quantitative differences in the fatigue strength and stability obtained with 5 types of internal fixation of metacarpal fractures, 105 preserved human metacarpals were cyclically tested in bending, torsion, and axial loading after oblique osteotomies of the metacarpal and internal fixation. The dorsal plate with lag screw was superior in all modes, followed by the two dorsal lag screws, crossed Kirschner wire tension banding, and intramedullary Kirschner wire fixation. The five intramedullary and the paired intramedullary Kirschner wire fixations were not statistically different. The fatigue life of the plate fixation was significantly larger in bending (1.5 times), torsion (1.6 times), and axial loading (2.5 times) than the second strongest fixation, two dorsal lag screws. Its initial rigidity was significantly higher in axial loading (1.5 times) but was not statistically different in bending and torsion.