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Biomedical subjects

S G Agnew

Publications and source records attributed to S G Agnew.

10 recordsLinked to original sources
PubMed1996

Radiographic recognition of the sacral alar slope for optimal placement of iliosacral screws: a cadaveric and clinical study.

Malpositioning of iliosacral screws happens more often when common variations in the morphology of the upper sacral segments are unrecognized. Radiological-anatomic correlations of sacral anatomy were studied in 10 fresh-frozen cadaveric pelvises without evidence of skeletal disease, obtained from six male and four female donors. Eighty consecutive patients with complicated pelvic fractures treated operatively by the same surgeon using percutaneously placed iliosacral screws were evaluated. Variations in the sacral alar anatomy and slope found in upper sacral segmentation anomalies are common. Surgically important and predictable abnormal morphological patterns can be easily identified using pelvic outlet and lateral sacral plain radiographs along with computed tomographic scans. On the true lateral projections, the iliac cortical density adjacent to the sacroiliac joint parallels the sacral alar slope and is almost always caudal and posterior to it; it delineates the anterior extent of the "safe zone" for iliosacral screw insertion. Thus, the lateral sacral image provides the surgeon with a better understanding of the sacral alar slope and can help prevent iliosacral screw placement errors. The lateral sacral image should always be used intraoperatively with the inlet and outlet images to guide iliosacral screw placement.

Adolescent↗
PubMed1996

Evaluation of new plate designs for symphysis pubis internal fixation.

The purpose of this study was to evaluate and compare biplanar and other newly designed plates used for pubic symphysis internal fixation to other standard plates. Our data demonstrate that neither of the newly designed symphyseal plates, curved (Zimmer four-hole plate with either two or four 4.5-mm cortical screws) nor the biplanar (Zimmer six-hole plate with four 4.5-mm cortical screws in one plane and two 4.5-mm cortical screws in another) significantly reduce motion more than the other plates tested (Synthes two-hole 4.5-mm dynamic compression plate with two 6.5-mm cancellous screws and six-hole 3.5-mm reconstruction plate with four 3.5-mm cortical screws). All of the plate constructs were able to restore motion to nearly that of the intact symphysis pubis and sacroiliac joint. In summary, using the anteroposterior compression disruption pattern and model, the disrupted symphysis does gap under load but has no effect on sacroiliac joint gapping. It does permit increase in relative flexion angles between the wings of the pelvis. All of the plate systems tested restore normal gap motion at the symphysis and normal sacroiliac joint flexion.

Bone Density↗
PubMed1995

Analysis of the torque applied to bone screws by trauma surgeons. Comparisons based on years of experience and material of implant construction.

Stability of an internal fixation construct is dependent on the torque placed on the screws holding the plate, the number of screws in the construct, and the number of cortices purchased by each screw. This study addresses the ability of surgeons to apply uniform torque and the variability between stainless steel and titanium. A total of 630 measurements were made by trained orthopedists using a device to measure the torque applied to 3.5 mm screws when tightening them to a plate. Variations were found to be significant depending on the number of years the orthopedist was in practice and the type of construct material used. The average torque applied to a stainless steel construct is 5.82 in-lb, while the torque applied to titanium is 5.41 in-lb (P < 0.01). The longer an orthopedist is in practice, the more torque will be applied to the screw/plate construct.

Biomechanical Phenomena↗
PubMed1994

Hemodynamically unstable pelvic fractures.

This article reviews the past and present data regarding the evaluation and resuscitation of patients with concomitant pelvic fractures and hemodynamic instability. The emphasis is that successful treatment requires a concerted and aggressive team approach from all disciplines. Timely care has proven to be the single most important factor in patient survivorship. Recent advances such as emergency posterior frames will allow simultaneous evaluation and resuscitation. A treatment algorithm is presented for emergency care.

Angiography↗
PubMed1994

The mangled lower extremity: can salvage be predicted?

The ability to predict amputation following combined orthopedic, vascular and soft tissue trauma to an extremity could eliminate prolonged attempts at salvage of a doomed limb. We reviewed our experience with 48 mangled lower extremities in 46 patients. Twenty-one penetrating wounds and 25 blunt injuries occurred in 37 men and nine women ranging in age from 3 to 59 years. Severity of injuries to muscle, skin, and major nerves were strongly interrelated (r = 0.49 to 0.74, P < 0.001), but there were no correlations between injuries to these tissues and severity of bone injury (r < 0.19, P > 0.20). Twenty-four limbs were salvaged, and 24 were amputated. Increased severity of soft tissue injury was associated with a greater probability of limb loss (P < 0.001), but limb salvage or amputation could not be predicted accurately by any variable or group of variables such as age, mechanism of injury, Injury Severity Score, presence of shock, level of injury, venous injury or repair, sequence of repair (vascular vs skeletal), time of fasciotomy, arteriography, blood requirement, or duration of ischemia. Amputation was best predicted by severity of injury to the sciatic or tibial nerves (P < 0.001), and by failure of arterial repair (P < 0.01). Severe extremity injuries require a coordinated approach and decisions regarding amputation require careful judgement. These decisions cannot always be made at the time of presentation or during the initial operation. If after revascularization and skeletal stabilization the extremity is clearly nonviable or remains insensate, then delayed amputation can be performed under more controlled circumstances.

Adolescent↗
PubMed1992

Lower extremity fracture fixation in head-injured patients.

Compared with nonsurgical management or delayed repair, early fracture fixation can reduce the incidence of pulmonary complications in patients with long-bone fractures of the lower extremities. Blunt trauma victims often have multiple nonskeletal injuries that might influence the risk of pulmonary complications, and when head injuries are present it has been a common practice to delay nonemergent operations for several days to protect the injured brain. We conducted a retrospective review of 114 patients with multiple trauma whose injuries included head trauma and a fracture of the neck or shaft of the femur or shaft of the tibia to determine if delayed stabilization of lower extremity fractures increased the risk of pulmonary complications or reduced the risk of cerebral complications. Forty-six patients underwent surgical fixation of their fractures within 24 hours of injury (early fixation), 26 patients had their fractures repaired more than 24 hours after injury (late fixation), and 42 patients did not undergo surgical fracture fixation. The risk of pulmonary complications was not related to the timing of surgical fracture fixation but was strongly influenced by the severity of injuries to the head and to the chest (p less than 0.001). Furthermore, a delay in fracture fixation did not protect the injured brain; the risk of CNS events was determined by the severity of the head injury (p less than 0.0001). Early fracture fixation in patients with head injury may be appropriate because it simplifies patient care and does not seem to worsen the head injury, but it does not prevent pulmonary complications in these high-risk patients.

Adolescent↗
PubMed1992

Immediate internal fixation of open, complex tibial plateau fractures: treatment by a standard protocol.

A retrospective review of 46 consecutive patients with complex (Schatzker V and VI) tibial plateau fractures treated at Harborview Medical Center between 1984 and 1989, disclosed a subset of 14 grade II or III (Gustilo) open injuries. We wished to determine the incidence of infection, union rate, and the number of operations required to achieve a satisfactory result, based on a treatment protocol: alignment and splinting of fracture at the scene of injury if possible, antibiotics administered in the emergency room (ER) and continued for 48 h, and admission of patient to the operating room as quickly as possible for irrigation and thorough debridement of the wound, immediate rigid internal fixation, and delayed primary closure at 5 days. No acute deep infection or radiographic evidence of implant loosening was noted. The final outcome was graded by Hospital for Special Surgery (HSS) Knee Rating Score at an average follow-up of 2 years 7 months. Radiographs were reviewed for reduction and evidence of postoperative change in reduction. The average HSS Functional Score was 81.5, and Knee Score was 84.6. Of 14 limbs, 10 had an excellent radiographic grade that did not change at follow-up, 2 had a satisfactory grade, and 2 had a poor grade.

Abbreviated Injury Scale↗