Biomedical subjects

K J Koval

Publications and source records attributed to K J Koval.

At least 19 recordsLinked to original sources

PubMed1996

Canine bone response to tyrosine-derived polycarbonates and poly(L-lactic acid).

Tyrosine-derived polycarbonates are a new class of degradable polymers developed for orthopedic applications. In this study the long-term (48 week) in vivo degradation kinetics and host bone response to poly(DTE carbonate) and poly(DTH carbonate) were investigated using a canine bone chamber model. Poly(L-lactic acid) (PLA) served as a control material. Two chambers of each test material were retrieved at 6-, 12-, 24-, and 48-week time points. Tyrosine-derived polycarbonates were found to exhibit degradation kinetics comparable to PLA. Each test material lost approximately 50% of its initial molecular weight (Mw) over the 48-week test period. Poly(DTE carbonate) and poly(DTH carbonate) test chambers were characterized by sustained bone ingrowth throughout the 48 weeks. In contrast, bone ingrowth into the PLA chambers peaked at 24 weeks and dropped by half at the 48-week time point. A fibrous tissue layer was found surrounding the PLA implants at all time points. This fibrous tissue layer was notably absent at the interface between bone and the tyrosine-derived polycarbonates. Histologic sections revealed intimate contact between bone and tyrosine-derived polycarbonates. From a degradation-biocompatibility perspective, the tyrosine-derived polycarbonates appear to be comparable, if not superior, to PLA in this canine bone chamber model.

Animals↗

PubMed1996

Operative stabilization of fracture dislocations of the sacroiliac joint.

Posterior fracture dislocations of the sacroiliac joint (crescent fracture) represent a subset of lateral compression pelvic fractures. The crescent fracture consists of a posterior iliac wing fracture with extension into the sacroiliac joint and a dislocation of the inferior 1/2 of the sacroiliac joint. The posterior superior iliac spine remains firmly attached to the sacrum by the strong posterior ligaments. As a result of this combination of bony and soft tissue injury, the hemipelvis is rotationally unstable, but because the sacrospinous and sacrotuberous ligaments remain intact the involved hemipelvis is stable to vertically applied forces. Operative stabilization is necessary to restore articular congruity of the sacroiliac joint, pelvic stability, and to allow early mobilization of the patient. Stabilization of the pelvis may be achieved through either an anterior or a posterior approach with or without transarticular fixation. A posterolateral approach to the crescent fracture and a method of stabilization using extraarticular fixation, intertable lag screws and outer table antiglide plates are described. The results of using this technique in 22 patients are reviewed.

Fracture Fixation, Internal↗

PubMed1996

The crescent fracture: a posterior fracture dislocation of the sacroiliac joint.

Between October 1987 and August 1992, 22 patients with crescent fractures, a posterior fracture-dislocation of the sacroiliac joint, were admitted, treated, and available for review at Tampa General Hospital and The Hospital for Special Surgery. The purpose of the study was twofold: (a) to evaluate the incidence, severity, and pattern of associated injuries, and (b) to determine the efficacy of a treatment protocol using a posterior extrapelvic approach and extraarticular internal fixation. The study population was composed of 13 females and nine males; the average age was 25 years (range 10-52). Despite the fracture pattern resulting in a rotationally unstable hemipelvis, all patients were hemodynamically stable at the time of presentation. Fourteen patients (64%) had other associated injuries, including five (23%) with closed head injury. In all cases a posterior extrapelvic approach was used with an anatomic reduction of the fractured iliac wing and the sacroiliac joint dislocation. Stable extraarticular internal fixation was obtained using intertable lag screws and outer-table neutralization plates. All the fractures were clinically and radiographically healed within 8-10 weeks postoperatively, and there were no acute wound, neurologic, or vascular complications. One patient developed osteomyelitis of the iliac crest 6 months postoperatively.

Adolescent↗

PubMed1996

Surgical neck fractures of the proximal humerus: a laboratory evaluation of ten fixation techniques.

OBJECTIVE: A biomechanical cadaver study was performed to compare the stability and ultimate strength of ten standard fixation techniques used for the treatment of surgical neck fractures of the proximal humerus. DESIGN: One hundred twenty (60 fresh frozen, 60 embalmed) proximal humerus specimens were selected and divided into two groups: fresh frozen specimens represented a nonosteopenic group and embalmed specimens an osteopenic group. Simulated fractures were created at the level of the surgical neck, reduced, and randomly assigned to one of ten methods of fixation (six fresh frozen and six embalmed specimens per fixation group). These constructs were then mechanically tested with the humeri oriented to create primarily shear loading of the fixation. RESULTS AND CONCLUSIONS: The T-plate and screws provided significantly stronger fixation (p < 0.005) in the fresh frozen specimens than all other methods. The Ender nails/tension band construct was the second strongest fixation technique, providing significantly stronger fixation (p < 0.01) than all the remaining techniques. Four Schanz pins with one pin placed through the greater tuberosity followed by the T-plate and screws provided the strongest fixation in embalmed specimens. Tension band fixation in both humeral groups was shown to provide the least effective fixation.

Biomechanical Phenomena↗

PubMed1996

Tibiotalar contact area and pressure distribution: the effect of mortise widening and syndesmosis fixation.

An unconstrained cadaver ankle model was designed to reevaluate the effect of ankle mortise widening and syndesmotic fixation on the load-bearing characteristics of the tibiotalar joint. Tibiotalar contact area, centroid shift, and mean contact pressure were quantified using a pressure-sensitive film technique. Six fresh-frozen below-knee amputation specimens were axially loaded with 500 N in three positions: neutral, 10 degrees of dorsiflexion, and 20 degrees of plantarflexion. The tibiotalar contact area and centroid position for each specimen in its intact state were first determined and then compared with values obtained after syndesmotic fixation, mortise widening of 2 and 4 mm, and deep deltoid ligament transection. Syndesmotic fixation significantly decreased joint contact area but did not consistently affect centroid position. However, unlike earlier studies, which used more constrained ankle fracture models, mortise widening with or without deltoid rupture was not found to significantly affect contact area, centroid position, or joint contact pressure. When statically loaded, the talus moved to its position of maximal congruence in the mortise, rather than displacing laterally along with the lateral malleolus.

Ankle Joint↗

PubMed1996

Cement augmentation of intertrochanteric fracture fixation: a cadaver comparison of 2 techniques.

We evaluated 2 techniques of cement augmentation to enhance fixation of intertrochanteric hip fractures. 4 fixation groups with 6 cadaver femurs in each group were compared: stainless steel lag screw and side plate with and without cement augmentation and a titanium alloy expandable dome plunger and side plate with and without cement augmentation. Gauges were used to establish the mechanical behavior of intact and then fractured femurs to simple uniaxial loads. Subsequent loading to failure allowed determination of maximum fixation strengths and modes of failure. Cement augmentation of each device increased its load to failure. There was no significant difference between the cemented lag screw and the uncemented dome plunger groups with average loads to failure of 4.0 x 10(3) N. The greatest average load to failure was in the cemented dome plunger group (5.6 x 10(3) N) with the lowest in the uncemented sliding hip screw group (3.6 x 10(3) N). Device cut-out as a cause of failure occurred mostly in the uncemented lag screw group. Sliding was enhanced by those methods that increased the fixation surface area within the femoral head, unless cement encroached in the region of the barrel-screw junction. Strain analysis showed that the dome plunger unloaded the bone at the calcar, regardless of cement augmentation, while the sliding hip screw allowed for compressive stresses in this area. Proper cement augmentation increases load to failure and minimizes nail cut-out for both devices studied. However, the dome plunger, a device with a large fixation area in the femoral head, was equally effective and eliminated potential cement encroachment. Failure of intertrochanteric fracture fixation in osteoporotic bone may be minimized by an appropriate choice of device or cement augmentation.

Bone Cements↗

PubMed1995

Intraoperative somatosensory evoked potential monitoring during acute pelvic fracture surgery.

Independent clinical neurological evaluation and intraoperative somatosensory evoked potential (SSEP) monitoring was performed on 30 vertically unstable hemipelvis fractures in 28 patients undergoing acute open reduction and internal fixation. Preoperative ipsilateral neurologic injury of the sciatic/lumbosacral plexus was noted in 15 of 30 fractures (50%). Significant unilateral SSEP changes occurred during manipulative reduction of two displaced sacroiliac joints and one sacral fracture. Because of the expeditious response of the surgical team, with release of traction/retraction, SSEP returned to baseline and no patient sustained an iatrogenic nerve injury or worsening of their preoperatie neurologic status. The incidence of postinjury lumbosacral plexopathy in unstable pelvic fractures is high (50%) when careful preoperative evaluation including SSEP is performed. The use of intraoperative SSEP monitoring is feasible in acute posterior pelvic fracture surgery and can help identify potential intraoperative iatrogenic lumbosacral neurological compromise.

Adolescent↗

PubMed1995

Effects of supine positioning and fracture post placement on the perineal countertraction force in awake volunteers.

An instrumented traction post was used to determine the magnitude and direction of the countertraction force applied to the perineum of 15 awake volunteers for a series of 12 positions used in fracture surgery and compared with their corresponding neutral position controls. The results demonstrated that adduction of the affected limb and abduction of the contralateral limb applied the greatest force to the perineum with ipsilateral and contralateral placement of the fracture post. These two maneuvers increased the perineal countertraction force 80% above their respective neutral readings. Abduction of the affected limb reduced the traction force by 50% with ipsilateral and contralateral placement of the fracture post. Flexion-abduction-external rotation of the contralateral leg reduced the forces applied to the perineum by 60% when the fracture post was placed contralateral to the affected limb. Contralateral placement of the post decreased the perineal countertraction force 46% below the value for ipsilateral post placement for this maneuver. Internal and external rotation of the affected limb had no effect on the perineal countertraction force for either placement of the post. There was a significant decrease in the perineal forces for the neutral positions after adduction of the affected limb and abduction of the contralateral limb with ipsilateral placement of the post, indicating that the volunteers shifted on the fracture table in response to pain. There was no significant difference in the direction of the countertraction force for the various positions.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗

PubMed1995

Treatment of fracture blisters: a prospective study of 53 cases.

From June 1987 to January 1993, 53 fractures complicated by overlying blisters were identified and prospectively followed. Data concerning the mechanism of injury, time course in the development of the fracture blisters, clinical characteristics of the blister, fracture type and management, and soft-tissue treatment and outcome were collected. Clinically, two types of blisters were identified: clear fluid filled and blood filled. Methods used to treat the skin blister were: aspiration of the blister, deroofing of the blister with subsequent application of Silvadene cream or coverage with a nonadherent dressing, and leaving the blister intact and covered by a loose gauze or exposed to the air. No significant difference was found in the outcome of the skin injury treated with the various modalities. Nineteen patients underwent early open reduction and internal fixation in the presence of intact fracture blisters. In 17 cases the incision healed within 3 days, sealing off the deeper structures, and reepithelialization of the blister bed then occurred at a later date. Two of the patients who had incisions pass through blood-filled blisters developed wound healing complications. Although there was no significant difference in the outcome of the soft-tissue treatment techniques, our present practice is to leave all fracture blisters intact. If the blisters rupture spontaneously, they are deroofed and covered with a nonadherent dressing. Early surgery is contemplated in patients with intact blisters and without severe swelling.

Adolescent↗

PubMed1995

Distal femoral nonunion: treatment with a retrograde inserted locked intramedullary nail.

Between March 1989 and August 1993, 16 distal femoral nonunions (16 patients) were treated using the supracondylar intramedullary nail. The time between the initial event and retrograde nailing averaged 33 months. The nonunion level was infraisthmal in four patients and supracondylar in 12. Operative technique involved retrograde insertion of a reamed supracondylar intramedullary nail through the intercondylar notch. Follow-up was available on all patients and averaged 20 months (range 9-46). Four nonunions (25%) united with a single surgery at an average of 17 months. A fifth nonunion united at 21 months after nail dynamization and subsequent nail breakage. The nonunions of two additional patients united after exchange of a broken retrograde nail. Additional surgical procedures were performed in six of the remaining nine patients in an attempt to gain union. At an average follow-up of 16 months (range 9-23), none of the nine had united. Nine nails fractured at an average of 11 months, all through a screw hole near the nonunion. Based on these results, we cannot recommend use of the supracondylar intramedullary nail in its present form for the treatment of distal femoral nonunions.

Adult↗

PubMed1995

Modular unipolar versus bipolar prosthesis: a prospective evaluation of functional outcome after femoral neck fracture.

Between January 1, 1987, and December 31, 1992, 140 community-dwelling geriatric patients > or = 65 years of age with a displaced femoral neck fracture (Garden III-IV) underwent primary prosthetic replacement and were followed prospectively for a minimum of 1 year. Overall, 92 patients received a cemented bipolar prosthesis and 48 patients received a cemented modular unipolar prosthesis. There were no statistically significant differences between the two groups with respect to preinjury characteristics (age, sex, and number and severity of medical comorbidities) and functional ability. There were no statistically significant differences between the two groups with regard to the number of postoperative complications, length of stay, and 1 year mortality rate. An in-depth functional evaluation was obtained as follows: level of ambulation, independence in basic activities of daily living (feeding, bathing, dressing, toileting), and independence in instrumental activities of daily living (food shopping, food preparation, banking, laundry, housework, and use of public transportation). At 1 year follow-up, no statistically significant differences in functional ability were identified between the unipolar and bipolar groups. Furthermore, at a minimum of 1 year follow-up, there were no statistically significant differences between the two groups with regard to the need for revision surgery or the incidence hip pain. Based on the results of this study, there does not appear to be any advantage to the use of bipolar endoprosthesis for the treatment of femoral neck fractures in the elderly patient. The lower cost of modular unipolar prostheses compared with bipolar prostheses provides additional support for their use.

Aged↗

PubMed1995

Fracture blister formation: a laboratory study.

A biomechanical study was performed to examine a proposed mechanism of fracture blister formation. Sixty cadaver ankle skin specimens were subjected to several levels of uniaxial strain and examined histologically. Dermal-epidermal separation patterns similar to those found histologically in previous studies of biopsied fracture blisters were seen in specimens strained 152% and greater. These findings support the hypothesis that fracture blisters can result from strain developed in the skin during initial fracture deformation.

Biomechanical Phenomena↗

PubMed1995

Postoperative complications and mortality associated with operative delay in older patients who have a fracture of the hip.

We prospectively studied 367 patients who had a fracture of the hip, to determine the effect of an operative delay on postoperative complications and on the one-year mortality rate. All of the patients were at least sixty-five years old, cognitively intact, living at home, and able to walk before the fracture. An operative delay was defined as an interval of three calendar days or more between the time of admission to the hospital and the operation. The operation was performed within two calendar days after admission in 267 (73 per cent) of the patients. When the factors of the patient's age and sex and the number of pre-existing medical conditions were controlled, it was found that an operative delay beyond this period approximately doubled the risk of the patient dying before the end of the first postoperative year. When the patient's age and sex and the severity of pre-existing medical conditions were controlled, there was also an increase in mortality associated with an operative delay, although this was not significant. With the numbers studied, an operative delay beyond two calendar days did not have a significant effect on the prevalence of complications during hospitalization. We concluded that an operative delay of more than two calendar days after admission is an important predictor of mortality within one year for elderly patients who have a fracture of the hip and who are cognitively intact, able to walk, and living at home before the fracture. Optimally, such patients should have the operation within two calendar days after admission to the hospital.

Activities of Daily Living↗

PubMed1995

Ambulatory ability after hip fracture. A prospective study in geriatric patients.

Three hundred thirty-six community-dwelling, previously ambulatory, geriatric patients with hip fracture were observed prospectively to determine ambulatory ability at a minimum followup of 1 year. One hundred thirty-seven (41%) patients maintained their prefracture ambulatory ability at a minimum followup of 1 year; 134 (40%) patients remained ambulatory but became more dependent on assistive devices; 39 (12%) previous community ambulators became household ambulators, and 26 (8%) patients became nonfunctional ambulators. Analysis was performed to determine which pre- and postinjury factors were predictive of failure to recover ambulatory capacity 1 year after fracture. Potential predictor variables analyzed included age, gender, number of comorbid conditions, prefracture ambulatory ability, prefracture living situation, fracture type, American Society of Anesthesiologists rating of operative risk, type of surgery, and number of postoperative complications. Multiple logistic regression analysis identified significant contributions of age, prefracture ambulatory ability, American Society of Anesthesiologists rating of operative risk, and fracture type to ambulatory recovery.

Activities of Daily Living↗

PubMed1995

Posttraumatic nonunion of the distal tibial metaphysis. Treatment using the Ilizarov circular external fixator.

Ten nonunions of the distal tibial metaphysis were treated by using the Ilizarov circular external fixator. Original fractures were classified in terms of the Association for the Study of Internal Fixation as AO type A (4 cases), type B (5 cases), and type C (1 case). Six patients had a history of osteomyelitis. Bifocal compression-distraction lengthening osteosynthesis was performed in all cases. Proximal metaphyseal corticotomy was combined with resection and compression of the distal nonunion site in five cases, and compression alone in three patients. Ankle arthrodesis, in addition to nonunion resection, was performed in two patients. Follow-up averaged 48 months (range, 26 to 81). Eight nonunions healed (80%). Limb length was completely corrected in five cases; angular and rotational alignment was corrected to within 5 degrees in seven patients (70%). Based on an objective and subjective scale, the results were considered good-to-excellent in seven cases and poor in three. Despite the high complication rate and relatively low success rate (70%), the use of the circular frame with small-diameter, tensioned wires may provide an alternative method for the treatment of the very difficult problems associated with complex low distal tibial metaphyseal nonunions.

Adult↗

PubMed1995

Polytrauma in the elderly.

As the elderly population grows, a concomitant increase in polytrauma in the geriatric sector is predicted. Diminished physiologic reserve and deficiencies in management contribute to higher rates of morbidity and mortality in the elderly patient with trauma as compared with the young patient with equivalent trauma. Currently, traditional trauma scoring systems are insufficient in directing triage and predicting survival for these elderly patients. This may be related to the effects of aging and associated comorbidities. Age, therefore, should be considered in contemporary scoring systems and treatment algorithms. The benefits of prompt identification and treatment of musculoskeletal, neurologic, abdominal, and cardiopulmonary trauma, and maintenance of adequate nutritional status are well established in the polytrauma setting, in general. For the elderly patient with polytrauma, early invasive hemodynamic and cardiac monitoring are advisable to identify occult shock, limit end organ hypoperfusion, prevent multiorgan failure, and ultimately improve survival.

Aged↗

PubMed1995

Biomechanical comparison of the sliding hip screw and the dome plunger. Effects of material and fixation design.

We studied the biomechanical behaviour of three sliding fixation devices for trochanteric femoral fractures. These were a titanium alloy sideplate and lag screw, a titanium alloy sideplate and dome plunger with cement augmentation, and a stainless-steel sideplate and lag screw. We used 18 mildly osteoporotic cadaver femora, randomly assigned to one of the three fixation groups. Four displacement and two strain gauges were fixed to each specimen, and each femur was first tested intact (control), then as a two-part fracture and then as a four-part intertrochanteric fracture. A range of physiological loads was applied to determine load-bearing, load-sharing and head displacement. The four-part-fracture specimens were subsequently tested to failure to determine maximum fixation strengths and modes of failure. The dome-plunger group failed at a load 50% higher than that of the stainless-steel lag-screw group (p < 0.05) and at a load 20% higher than that of the titanium-alloy lag-screw group (NS). All 12 lag-screw specimens failed by cut-out through the femoral head or neck, but none of the dome-plunger group showed movement within the femoral head when tested to failure. Strain-gauge analysis showed that the dome plunger produced considerably less strain in the inferior neck and calcar region than either of the lag screws. Inferior displacement of the femoral head was greatest for the dome-plunger group, and was due to sliding of the plunger. The dome plunger with cement augmentation was able to support higher loads and did not fail by cut-out through the femoral head.(ABSTRACT TRUNCATED AT 250 WORDS)

Biomechanical Phenomena↗

PubMed1995

Fractures of the proximal part of the femur.

The orthopaedic surgeon has a multitude of internal fixation devices and techniques available for use in the treatment of subtrochanteric fractures of the proximal femur. The successful use of second-generation locking nails is technically demanding. Close attention to positioning of the patient, reduction of the fracture, placement of the guide-wire, and insertion of the nail and of the proximal and distal locking screws is mandatory. The newer, high-strength hip-screws allow good fixation of a fracture that extends into the piriformis fossa. If medial comminution is present, this technique is best performed in conjunction with indirect reduction and bone-grafting. With proper technique, these devices allow the surgeon to manage predictably a complex subtrochanteric fracture that previously had to be treated with traction or extensive dissection and with (frequently inadequate) internal fixation.

Adult↗