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Biomedical subjects

L L Latta

Publications and source records attributed to L L Latta.

At least 19 recordsLinked to original sources
PubMed2006

A radiographic review of 135 total hip Charnley arthroplasties followed between 15 and 35 years.

The long-term radiologically interpreted results of low-friction Charnley hip arthroplasties have been previously suggested to be influenced by surgical details, such as orientation of the femoral component, degree of coverage of the plastic acetabulum and other features. We carefully analyzed the radiographs of 135 Charnley arthroplasties that had remained functional, had not been revised and had follow-ups between 15 and 35 years. Several common denominators were identified amongst these radiographs: 93.5% arthroplasties had 100% coverage of the acetabular component; 88% had acetabular inclination between 40-45 degrees ; 84.5% had a proximal/medial column of cement between 3 and 5 millimeters at the level of femoral head resection; 81% had a femoral canal/stem ratio more than 50%; and 84% had a column of cement that extended below the tip of the prosthesis. This study supports the importance of technical surgical details that enhance the chances of long-term survival of cemented total hip arthroplasties.

Adolescent↗
PubMed2002

[Mobility of unstable fractures of the odontoid during helmet removal. A biomechanical study].

In severe motorcyclist accidents unstable injuries of the cervical spine can usually not be excluded before an X-ray has been taken in the hospital. Despite this the helmet has to be taken off at the place of the accident in order to provide adequate treatment and airway management of the injured driver. There are no data in the current literature showing what happens to unstable lesions of the cervical spine during helmet removal. An experimental unstable lesion of the cervical spine was created by an osteotomy of the odontoid in 10 fresh frozen cadavers with intact soft tissues. All motions occurring in the segments C1-2 and C2-3 during helmet removal were recorded by fluoroscopy. The average motion in the unstable segment C1-2 was 23.7 degrees during a full range of extension-flexion movement of the cervical spine without any signs of dislocation of the segment. After application of the helmet there was one case of dislocation of C1-2 in neutral supine position already, and two further cases of dislocations during helmet removal. The average motion of C1-2 recorded during helmet removal was 19.0 degrees (2-25 degrees ), median 18.0 degrees. In order to avoid fracture dislocations and motion in the unstable upper cervical spine the helmet should better be cut in pieces at the place of the accident. There is a need for discussions with helmet producers to develop a new generation of helmets that can be removed easily without manipulating the head.

Accidents, Traffic↗
PubMed2001

A new modular testing system for biomechanical evaluation of tibial intramedullary fixation devices.

This biomechanical study was performed to evaluate a new modular, tibial testing system developed for analysis of tibial nails and their locking screws.A new testing system, consisting of five modules, was designed to simulate a tibia. For this study one module was removed to simulate a 55-mm distal tibial defect inducing maximum loading on the distal portion of the implant and locking bolts. The tibial load offsets were 23 mm proximally and 10 mm distally medial to the centreline of the tibial shaft to simulate the location of the expected resultant load during the peak loading and inversion torque on the ankle during the gait cycle. Four solid tibial nails (STN, Stryker-Howmedica-Osteonics, Kiel, Germany) were tested to static failure and 15 nails were tested dynamically. Our results showed that the solid tibial nails fractured in the testing device in the same manner and location as they do in clinical series. Evaluation of the results showed the mean fatigue limit of the STN to be 1.4 kN for 500,000 cycles with a standard deviation (S.D.) of 0.33 kN. This biomechanical study establishes a standard technique for the biomechanical testing of tibial nails, in a clinically relevant manner, avoiding the inconsistency of cadaver bone tests. As it is a standardised test set-up this new modular testing system could serve as a standard by which small diameter tibial nails and other devices could be evaluated and compared with other systems currently in use.

Biomechanical Phenomena↗
PubMed2001

Triangulated pedicle screw construct technique and pull-out strength of conical and cylindrical screws.

To compare the mechanical effectiveness of a new conical screw design with a conventional cylindrical screw design, the screw insertion time, torque, and pull-out strength of single-pedicle screw and triangulated-pedicle screw constructs of each type of screw were compared in human cadaveric vertebral bodies. The time required to insert the conical screws was less than that required for cylindrical screws. Regression analysis revealed a positive correlation between insertion torque and pull-out strength of single and triangulated constructs of each type of screw. The conical screw had a greater increase than the cylindrical screw in the pull-out strength of triangulated pedicle screw constructs. Application of the new conical screw design was significantly faster, and the new screw had better mechanical fixation to the vertebral body than did the conventional cylindrical screw tested.

Adolescent↗
PubMed2001

The stabilizing effects of different orthoses in the intact and unstable upper cervical spine: a cadaver study.

BACKGROUND: Although cervical orthoses are frequently used in prehospital stabilization and in the definitive treatment for lesions of the cervical spine, there is little information about the control of extension-flexion, lateral bending, and rotation given to individual segments by different designs. METHODS: In an experimental in vitro study with four fresh frozen cadavers, the halo vest was compared with the soft collar, prefabricated Minerva brace, and Miami J collar. The controlling effects for the segments C1-2 and C2-3 were tested for all four devices in the intact and the unstable spine with an Anderson type II fracture of the odontoid. RESULTS: All four orthoses reduced the range of motion at both C1-2 and C2-3 of the intact spine significantly, although none of the three semirigid devices provided a halo-like immobilization in the intact spine. The osteotomy of the odontoid increased the range of motion in the segment C1-2. The soft collar did not give any clinically relevant stability to the unstable spine. Miami J and Minerva brace provided a similar moderate control in the sagittal plane but a much better control of "torque" in the upper cervical spine. The halo vest did not allow any measurable motion in any plane with our experimental external loading. CONCLUSION: The halo vest seems to be the first choice for conservative treatment of unstable injuries of the upper cervical spine, although pin track problems, accurate fitting of the vest, and a lack of patient compliance lead to clinical failures.

Biomechanical Phenomena↗
PubMed2000

Functional bracing for the treatment of fractures of the humeral diaphysis.

BACKGROUND: Nonoperatively treated fractures of the humeral diaphysis have a high rate of union with good functional results. However, there are clinical situations in which operative treatment is more appropriate, and, though interest in plate osteosynthesis has decreased, intramedullary nailing has gained popularity in recent years. We report the results of treating fractures of the humeral diaphysis with a prefabricated brace that permits full motion of all joints and progressive use of the injured extremity. METHODS: Between 1978 and 1990, 922 patients who had a fracture of the humeral diaphysis were treated with a prefabricated brace that permitted motion of adjacent joints. The injured extremities were initially stabilized in an above-the-elbow cast or a coaptation splint for an average of nine days (range, zero to thirty-five days) prior to the application of the prefabricated brace. Orthopaedic residents, supervised by teaching staff, provided follow-up care in a special outpatient clinic. Radiographs were made at each follow-up visit until the fracture healed. RESULTS: We were able to follow 620 (67 percent) of the 922 patients. Four hundred and sixty-five (75 percent) of the fractures were closed, and 155 (25 percent) were open. Nine patients (6 percent) who had an open fracture and seven (less than 2 percent) who had a closed fracture had a nonunion after bracing. In 87 percent of the 565 patients for whom anteroposterior radiographs were available, the fracture healed in less than 16 degrees of varus angulation, and in 81 percent of the 546 for whom lateral radiographs were available, it healed in less than 16 degrees of anterior angulation. At the time of brace removal, 98 percent of the patients had limitation of shoulder motion of 25 degrees or less. We were unable to follow most of the patients long-term, as they did not return to the clinic once the fracture had united and use of the brace had been discontinued. CONCLUSIONS: Functional bracing for the treatment of fractures of the humeral diaphysis is associated with a high rate of union, particularly when used for closed fractures. The residual angular deformities are usually functionally and aesthetically acceptable. The present study illustrates the difficulties encountered in carrying out long-term follow-up of indigent patients treated in charity hospitals that are affiliated with teaching institutions. These difficulties are also becoming common with patients insured under managed-care organizations and are frequent in our peripatetic population.

Adult↗
PubMed1999

Functional fracture bracing.

Functional bracing is an effective therapeutic modality in the management of selected fractures of the tibia, humerus, and ulna, particularly low-energy injuries. In the case of tibial fractures, it is applicable only to reduced transverse fractures and to axially unstable fractures with an acceptable degree of shortening. The rate of union of tibial fractures after functional bracing is approximately 97%. The initial shortening noted with closed tibial fractures rarely increases with weight bearing. Shortening has been reported to be as little as 12 mm in 95% of patients, with angulation of 8 degrees in 90%. Such minimal shortening and angulation do not affect functional results. In closed and type I open diaphyseal humeral fractures treated with functional braces, the nonunion rate is approximately 3%. Most of the reported residual angular deformities have been functionally and cosmetically acceptable. For isolated ulnar fractures, the nonunion rate is approximately 2%. Functional fracture bracing is predicated on the premise that motion at the fracture site encourages osteogenesis. The method is applicable only to selected fractures, and it is necessary to have a clear understanding of its rationale, indications, and technique.

Braces↗
PubMed1998

Isolated ulnar shaft fractures treated with functional braces.

OBJECTIVE: To report the results from functional bracing of isolated ulnar shaft fractures. DESIGN: Retrospective review. SETTING: Two university hospitals. PATIENTS: Isolated ulnar shaft fractures in 444 patients were stabilized in functional braces that permitted full range of motion of all joints. INTERVENTION: Prefabricated braces that extended from below the elbow to above the wrist were applied within the first week after the initial injury. OUTCOME MEASURES: Union of the fracture, fracture angulation, and final range of motion of the forearm were evaluated. RESULTS: Two hundred eighty-seven patients were available for follow-up (65 percent). Union took place in 99 percent of the fractures. Shortening of the ulna averaged 1.1 millimeters (range 0 to 10 millimeters). Final radial angulation averaged 5 degrees (range 0 to 18 degrees). Dorsal angulation averaged 5 degrees (range 0 to 20 degrees). Average loss of pronation was greatest in fractures of the proximal third of the ulna, averaging 12 degrees. Fractures in the distal third averaged a loss of 5 degrees of pronation. CONCLUSIONS: Functional bracing is a viable therapeutic alternative in the management of isolated ulnar shaft fractures. It is associated with a 99 percent union rate and good to excellent functional results in more than 96 percent of patients.

Adult↗
PubMed1995

Effect of nonsteroidal antiinflammatory drugs on fracture healing: a laboratory study in rats.

We studied the effects of two nonsteroidal antiinflammatory drugs (NSAIDs) on fracture healing in rats: ibuprofen (30 mg/kg/day) and indomethacin (1 mg/kg/day). Femoral fractures were induced via a three-point bending technique. NSAIDs were administered orally for 4 or 12 weeks. Control animals received no medication. In each group a minimum of six animals were killed at the following intervals: 2, 4, 6, 8, 10, and 12 weeks postfracture. Fracture healing was determined by mechanical testing and histologic evaluation. The bending strength of each fractured femur was expressed as a percentage of the strength of the intact, contralateral femur. Histologic evaluation was performed on serial longitudinal sections stained with hematoxylin and eosin using a qualitative score of maturity of the callus. Ibuprofen and indomethacin both retarded fracture healing, with significant differences in "mechanical healing" found between the control and experimental groups after 10 weeks of drug administration. Both drugs also induced qualitative histologic changes manifested by delayed maturation of callus, which was noticeable earlier than the difference found by mechanical testing of bone. Our data suggest that NSAIDs have an inhibitory effect on fracture repair that is reversible after cessation of indomethacin but not ibuprofen.

Animals↗
PubMed1995

Fracture healing and mast cells.

We analyzed the morphology and localization of mast cells during the course of fracture repair in control rats and in animals with delayed healing of fractures induced by nonsteroidal antiinflammatory drugs (NSAIDs). In the first 2 weeks of fracture healing in control animals, mast cells were found either in the vicinity of blood vessels or in the vascularized tissue proliferating into the cartilaginous portion of subperiosteal callus. In the later stages (6-8 weeks), mast cells were seen in loose connective tissue in bone marrow surrounded with translucent ground substance. At this stage of healing, a hyperplasia of mast cells and cell degranulation was often seen in close proximity to osteoclasts and areas of bone resorption. Treatment with NSAIDs delayed fracture healing and the appearance of mast cell hyperplasia in bone marrow for approximately 4 weeks, suggesting that mast cells have specifically defined temporal and regional distribution during the process of bone repair. Histochemical studies documented a significant amount of chymase in the mast cells in callus. This enzyme was purified from mast cells by chromatography and was able to digest in vitro proteins extracted from bone. Our data suggest that mast cells in fracture healing are involved in digestion of extracellular matrix in callus tissue that could facilitate (a) angiogenesis in the early stages of healing, and (b) the replacement of provisional tissue with newly formed bone in the later stages of fracture healing.

Animals↗
PubMed1993

A biomechanical evaluation of magnetic resonance imaging-compatible wire in cervical spine fixation.

In a bovine cervical spine model, the ultimate and fatigue strengths as well as relative magnetic resonance imaging artifact produced by titanium, cobalt chrome, and stainless-steel wires in various gauges were assessed. Single-cycle and fatigue strength of wire constructs were measured. Although larger wires generally had greater static strength, fatigue strength was mixed. Sixteen-gauge titanium, and all stainless-steel models (22-gauge braided, 18-gauge, and Songer cable) withstood 10,000 cycles without failure, whereas all other constructs rarely could withstand a similar 10,000 cycles. Magnetic resonance imaging was performed on calf cervical spines instrumented with the various materials. Titanium exhibited the least artifact, stainless-steel showed the greatest artifact, and cobalt chrome an intermediate amount. Although titanium wire produces the least amount of magnetic resonance imaging artifact, it remains a poor choice for implant fixation because its notch sensitivity reduces its fatigue resistance compared with stainless steel, which remains the more dependable choice.

Animals↗
PubMed1993

Precision oblique osteotomy for shortening of the ulna.

The obstacles of prolonged healing time and technically demanding osteotomy and plate fixation in the performance of ulnar shortening osteotomies have been overcome by a precision system that includes a 45 degrees osteotomy and 2.7 mm interfragmentary lag screw. In 23 transverse osteotomies healing time averaged 21 weeks with one nonunion. In 17 precision oblique osteotomies healing time averaged a substantially shorter 11 weeks. Biomechanical data obtained from cadaveric testing comparing these two constructs demonstrated a structural stiffness that was clearly greater in torsion testing for the oblique osteotomy. No biomechanical difference was identified in the anteroposterior and lateral bending tests. The system permits the reliable performance of two parallel osteotomy cuts, allowing the removal of a precise amount of bone. The compression device and specialized plate permit easy coaptation of the osteotomy surfaces, which are locked into position by a precise 22 degrees interfragmentary lag screw. The surgical procedure is more quickly completed, and the frustration of this previously challenging procedure is now completely removed.

Adult↗
PubMed1993

Sliding characteristics of compression hip screws in the intertrochanteric fracture: a clinical study.

Sliding of compression hip screws (CHS) is advantageous when it allows for controlled collapse of a hip fracture and progressive stabilization. A retrospective review was performed on 47 intertrochanteric (IT) fractures treated with a Zimmer CHS. Previous studies had identified certain parameters as being important to CHS sliding characteristics in vitro. Using conventional diagnostic material (radiographs), we sought to use these parameters as clinically useful tools. Screw sliding, as well as geometric parameters of CHS that relate to screw sliding, such as barrel engagement in relation to screw extension and screw-plate angle, were measured and calculated from serial radiographs. Almost all screw sliding occurred within 30 days postoperation. Fracture stability and quality of reduction were two main factors relating to screw sliding (p < 0.01). High screw-plate angle and longer screw-barrel engagement had no correlation with screw sliding even in unstable fractures. All five failures were due to cut-out after complete or almost complete collapse of the sliding mechanism in non-anatomically reduced fractures in osteoporotic females. Unstable fractures in osteoporotic bone do seem to require supplementary fixation beyond sliding screw fixation alone. None of the mechanical parameters (as judged from plane radiographs) that control the tendency of the CHS to slide could be statistically correlated with incidence or degree of sliding. Therefore, it was concluded that it is impractical to attempt to predict sliding tendency from plane radiograph measurements.

Adult↗
PubMed1993

Tibial fracture stability. Analysis of external fracture immobilization in anatomic specimens in casts and braces.

Plaster casts, custom-fabricated fracture braces, and prefabricated fracture braces were compared in the laboratory for the stability they provided to closed, experimental, diaphyseal fractures of the tibia and fibula on anatomic specimens. The stability was comparable for each type of device tested for the loading conditions of isolated compression, bending, and torsion. Length stability (overriding at the fracture site) was poor, rotation was marginal (by clinical standards), and angulation was very good. Selective removal of portions of each cast and brace demonstrated that the classic patellar-tendon-bearing (PTB) extension proximally and below ankle extensions distally had insignificant effects on stability of these middle-third diaphyseal fractures for the conditions tested. The soft-tissue compression provided by a snug, tapered "cylindrical" sleeve, which encompassed the soft tissues from the tibial tubercle to the flare of the distal tibia and fibula, provided the stabilizing effect for all of the devices tested.

Biomechanical Phenomena↗
PubMed1988

Diaphyseal fractures of the humerus. Treatment with prefabricated braces.

Using a prefabricated brace, we treated 233 patients who had a fracture of the humeral shaft. One hundred and seventy patients were available for follow-up, which ranged from five weeks to forty-eight months. In these patients (forty-three open and 127 closed fractures), the average time to union was 10.6 weeks; the average varus-valgus angulation, 5 degrees; the average anterior-posterior angulation, 3 degrees; and the average shortening, as measured radiographically, four millimeters. All but three of the patients had an excellent or a good functional result with a nearly full range of motion of the extremity. There were a minimum of complications, including three non-unions. Because of the low morbidity and high rate of success, we concluded that the treatment of choice for diaphyseal fractures of the humerus is the prefabricated brace.

Adolescent↗