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P T Simonian

Publications and source records attributed to P T Simonian.

At least 37 records · Page 2Linked to original sources
PubMed1997

Biomechanics of pelvic fixation.

This article reviews a series of biomechanical studies performed in the author's laboratory, evaluating the instabilities produced by the more common and problematic pelvic ring fracture patterns and the increasingly popular and newly developed modes of internal fixation. Topics that are discussed include the following: anteroposterior compression injuries and the disrupted sacroiliac joint; sacral fractures; anteroposterior compression injuries and symphyseal fixation; new symphyseal plate designs; unstable pubic rami fractures; unstable fractures of the iliac wing; and resuscitation fixator biomechanics.

Biomechanical Phenomena↗
PubMed1997

Stabilization of pelvic ring disruptions.

Pelvic ring disruptions are challenging management problems for the orthopedic surgeon. Early hemorrhage, permanent nerve injury, and late pain caused by residual pelvic deformity are some of the many complicating factors. A variety of treatment alternatives are available to stabilize the disrupted pelvic ring. Each technique has inherent advantages and problems.

Child↗
PubMed1997

Popliteomeniscal fasciculi and the unstable lateral meniscus: clinical correlation and magnetic resonance diagnosis.

We hypothesize that disruption of the fascicular attachments between the popliteus and lateral meniscus can result in gross instability of the meniscus producing locking of the knee. This study brings attention to the importance of the clinical examination, and the need for clinical correlation to magnetic resonance (MR) studies. We report on three patients referred with the history of mechanical locking episodes of their knee. Initial MR examinations were all read as normal before referral to our institution. On close review of these MR examinations, popliteomeniscal fascicular disruption could be seen in each case. Each of these patients had arthroscopic-repair of these meniscal detachments. At 1-year follow-up, all patients had resolution of mechanical symptoms. Each patient had confirmation of their repair with repeat arthroscopy or MR and arthrographic examinations. An anatomic specimen was used to identify the popliteus muscle and tendon, the lateral meniscus, the antero-inferior popliteomeniscal fascicle, and the postero-superior popliteomeniscal fascicle attachments. MR images of the same anatomic specimen show both superior and inferior fasciculus attachments to the capsule. MR examples of the intact and disrupted antero-inferior and postero-superior popliteomeniscal fasciculi have been correlated to anatomic specimens to help familiarize the orthopaedic surgeon with these important stabilizing structures.

Adolescent↗
PubMed1997

Candida infection after total knee arthroplasty. Management without resection or amphotericin B.

A rare case of Candida infection after revision total knee arthroplasty that was treated medically, without amphotericin B or resection arthroplasty, is reported. This case occurred in an elderly patient without predisposing medical problems. The patient was treated with only a suppressive dose of ketoconazole. The patient was last evaluated 6 years after the revision surgery and had no problem or signs of infection. Factors contributing to successful medical treatment in this case were likely the routine debridement at revision surgery and the patient's intact immune system.

Aged↗
PubMed1997

Biomechanical comparison of internal fixation techniques for the treatment of unstable basicervical femoral neck fractures.

OBJECTIVES: The optimal method of internal fixation of basicervical femoral neck fractures is controversial. This area represents a transition zone between the intracapsular femoral neck fracture, usually fixed with multiple cancellous screws, and the extracapsular interochanteric fracture, fixed with a sliding screw device [sliding hip screw (SHS)] and derotation screw (DRS) device. The authors' specific aim was to biomechanically compare these two methods of fixation in a cadaveric model of a basicervical femoral neck fracture with posteromedial comminution. DESIGN: The authors compared the average peak force during cyclic loading and the maximum axial force sustained by matched pairs of specimens stabilized with either fixation and subjected to axial and torsional loading while flexing and extending the hip. The average peak force was defined as the mean of the peak force values measured in each loading cycle with the maximum displacement of the materials tester actuator the same for each cycle (displacement control) as opposed to the maximum force being held constant (load control). RESULTS: The cancellous screw group maintained a significantly lower average peak force, 470 Newtons (SD = 145 Newtons), compared with 868 Newtons (SD = 186 Newtons) for the SHS and DRS composite group (p < 0.01). Similarly, the cancellous screw group demonstrated a lower ultimate load to failure, 1,863 Newtons (SD = 475 Newtons) compared with 3,557 Newtons (SD = 215 Newtons) for the SHS and DRS composite group (p < 0.01). CONCLUSION: The results support the use of an SHS and DHS composite compared with three cancellous screws in the treatment of unstable basicervical femoral neck fractures.

Aged↗
PubMed1997

Iliosacral screw fixation: early complications of the percutaneous technique.

OBJECTIVE: To report on the early complications related to the percutaneous placement of iliosacral screws for the operative treatment of displaced posterior pelvic ring disruptions. STUDY DESIGN: Prospective, consecutive. SETTING: Level-one trauma center. PATIENTS: One hundred seventy-seven consecutive patients with unstable pelvic ring fractures. One hundred two male and seventy-five female patients ranging in age from eleven to seventy-eight years (mean, thirty-two years). INTERVENTIONS: Operative procedures were performed urgently according to the patient's clinical condition. Anterior pelvic reductions and fixations were performed by using internal and external fixation techniques. Accurate closed or open reductions of the posterior pelvic ring disruptions were accomplished by using a variety of surgical techniques dependent on the specific pattern of pelvic ring disruption. Closed manipulative reductions of the posterior pelvic ring were attempted for all patients. Open reductions were necessary in those patients with unacceptable closed manipulative reductions as assessed fluoroscopically at the time of operation (more than one centimeter in any field of fluoroscopic imaging). MAIN OUTCOME MEASURES: Plain inlet and outlet radiographs were obtained postoperatively at six weeks, three months, and twelve months. A pelvic computed tomography scan was performed postoperatively to assess fracture or dislocation reduction and the implant safety. Annual follow-up pelvic radiographs were obtained. Residual pelvic deformities were quantified based on these imaging modalities. RESULTS: There were no posterior pelvic infections. Minimal blood loss was associated with this technique. Complications occurred due to inadequate imaging, surgeon error, and fixation failure. Fluoroscopic imaging was inadequate due to obesity or abdominal contrast in eighteen patients. Five screws were misplaced due to surgeon error. One misplaced screw produced a transient L5 neuropraxia. Fixation failures related to either crandiocerebral trauma, delayed union, noncomplicance, and a deep anterior pelvic polymicrobial infection secondary to a urethral tear occurred in seven patients. There were two sacral nonunions that required debridement, bone grafting, and repeat fixation prior to healing. CONCLUSIONS: Iliosacral screw fixation of the posterior pelvis is difficult. The surgeon must understand the variability of sacral anatomy. Quality triplanar fluoroscopic imaging of the accurately reduced posterior pelvic ring should allow for safe iliosacral screw insertions. Anticipated noncompliant patients or those with craniocerebral trauma may need supplementary posterior pelvic fixation. Low rates of infection, blood loss, and nonunion can be expected.

Adolescent↗
PubMed1997

Joint motion and surface contact area related to component position in total hip arthroplasty.

A three-dimensional computer model of a total hip replacement was used to examine the relationship between the position of the components, the range of motion and the prosthetic joint contact area. Horizontal acetabular positions with small amounts of acetabular and femoral anteversion provide the largest contact areas, but result in limited joint movement. These data will allow surgeons to select implant positions that will provide the largest possible joint contact area for a given joint range of motion although these are conflicting goals. In some component positions a truncated spherical prosthetic head resulted in smaller contact areas than a completely spherical head.

Computer Simulation↗
PubMed1997

Assessment of morbidity of semitendinosus and gracilis tendon harvest for ACL reconstruction.

This study evaluates the morbidity of harvest of both the semitendinosus and gracilis tendons for anterior cruciate ligament reconstruction on nine patients at a minimum of 3 year follow-up. Specifically, the effect on knee function, knee extension and flexion strength, the size of the individual posterior thigh muscles, and the extent of retraction of the semitendinosus and gracilis tendons were evaluated. At final follow-up, each patient was evaluated using the following functional scales: International Knee Documentation Committee (IKDC), Hospital for Special Surgery (HSS), Lysholm, and Tegner. Each patient also had a dynamometer evaluation and a comprehensive magnetic resonance imaging study of both the operated and nonoperated knees. The average functional evaluation scores were: HSS-47.9, Lysholm-88, and Tegner-0.27. The average percent quadriceps and hamstring strength of the operated compared with the nonoperated extremities were 93.7% and 95.3%, respectively; neither decrease was significant. Magnetic resonance imaging evaluation of the cross-sectional areas of the biceps femoris, semimembranosus, and sartorius muscles of both thighs at the same level above the joint were not significantly different. The distal-most insertion of the semitendinosus and gracilis tendons after harvest were always more proximal than the nonoperated side; the average difference was 26.7 mm (range: 11 to 32 mm) for the semitendinosus (unable to calculate in three patients) and 47.1 mm (range: 17 to 72 mm) for the gracilis. We conclude that tendon harvest of the semitendinosus and gracilis muscles does not significantly compromise function and strength despite a more proximal insertion of the retracted tendons. In addition, the majority of cases demonstrated some but never complete regrowth or scar formation of these tendon remnants.

Adult↗
PubMed1996

Traumatic dislocation of the thumb carpometacarpal joint: early ligamentous reconstruction versus closed reduction and pinning.

Early reconstruction of the thumb carpometacarpal (CMC) joint after traumatic dislocation, when instability is present, may decrease the incidence of recurrent instability and post-traumatic joint degeneration. We report two retrospective cohort groups of patients who had sustained a traumatic thumb CMC joint dislocation. The first 8 patients, group A, were treated with closed reduction and pinning. Because the results were unsatisfactory with 4 patients, requiring revision surgery for recurrent instability in 3 and degenerative arthritis in 1, the treatment plan was changed to open reduction with a flexor carpi radialis weave, group B. The 9 patients in group B underwent early (an average of 7 days after injury) ligamentous reconstruction to decrease the incidence of joint damage from recurrent instability and improve long-term functional results. For patients in group B with a minimum follow-up period of 2 years, pain was not a major problem, and range of motion and grip strength were essentially preserved. The functional variables affected most in both groups were thumb abduction, which was decreased by 10%, and pinch strength, which was decreased by 13%, in group B, as compared to 20% and 19%, respectively, for the patients in group A. Radiographically, the joint space was slightly narrowed (Eaton stage II) in 3 cases in group B; however, these were asymptomatic. In group A, 5 patients demonstrated degenerative changes of the CMC joint (3 Eaton stage II, 2 stage III), and 3 patients were symptomatic after treatment.

Adult↗
PubMed1996

Closed reduction and percutaneous skeletal fixation of sacral fractures.

Closed manipulative reduction and percutaneous fixation of a displaced sacral fracture is a treatment alternative that offers several advantages. The fracture is reduced and stabilized without an extensile surgical exposure. The risks of surgical wound problems, especially infection, are lessened. Operative and anesthesia times are decreased by using percutaneous techniques of reduction and fixation. Blood loss is also minimized by the percutaneous procedure. Sacral nonunion after this technique is rare. The procedure is dependent on quality fluoroscopic pelvic imaging, a thorough understanding of the posterior pelvic anatomy and early operative intervention, especially in patients with severe posterior pelvic deformities.

Adolescent↗
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

Internal fixation in pelvic fractures and primary repairs of associated genitourinary disruptions: a team approach.

Associated urological and orthopedic injuries of the pelvic ring are complex with numerous potential complications. These patients are treated optimally using a team approach. The combined expertise is not only helpful initially when managing these difficult patients, but also later as problems develop. This study describes a treatment protocol and reports the early results of 23 patients with unstable pelvic fractures and associated bladder or urethral disruptions, or both, treated surgically with open reduction and internal fixation of the anterior pelvic ring injuries at the same anesthetic and using the same surgical exposure as the urethral realignments or bladder repairs or both. Early complications occurred in four patients (17%): one patient sustained a fifth lumbar nerve injury caused by the pelvic reduction procedure, and three patients had anterior pelvic internal fixation failures. Late complications occurred in eight patients (35%). There was one deep wound infection (4.3%) that presented 6 weeks after injury. Late urological complications occurred in seven patients (30%). Four of the nine male patients with urethral disruptions had urethral stricture after their primary urethral realignments (44%). Three of the 18 male patients admitted to impotence (16.7%). One of the three had a residual thoracic paraplegia caused by a burst fracture. One of the five female patients had urinary incontinence and required a bladder suspension operation to restore normal function (20%). A low infection rate can be expected despite the use of internal fixation. Early urethral "indirect" realignments avoid more difficult delayed open repairs; however, late urological complication rates are still high. Early "direct" bladder repairs are easily performed at the time of anterior pelvic open reduction and internal fixation. Suprapubic tubes are not necessary to adequately divert the urine when large diameter urethral catheters are used in these patients.

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↗
PubMed1996

MRI in acute knee dislocation. A prospective study of clinical, MRI, and surgical findings.

We treated 17 knees in 15 patients with severe ligament derangement and dislocation by open repair and reconstruction. We assessed the competence of all structures thought to be important for stability by clinical examination, MRI interpretation, and surgery. Our findings showed that in these polytrauma patients clinical examination was not an accurate predictor of the extent or site of soft-tissue injury (53% to 82% correct) due mainly to the limitations of associated injuries. MRI was more accurate (85% to 100% correct) except for a negative result for the lateral collateral ligament and posterolateral capsule. The detail and reliability of MRI are invaluable in the preoperative planning of the surgical repair and reconstruction of dislocated knees.

Acute Disease↗
PubMed1996

Pectoralis tendon avulsion in the skeletally immature.

Pectoralis tendon avulsion is a rare injury typically occurring in skeletally mature men. The diagnosis can be difficult to make and is often delayed. We report a case of a complete bony avulsion of the pectoralis tendon at the site of its humeral insertion in a skeletally immature male. The palpable and radiographic evidence of ossification at the injury site made the diagnosis in this adolescent case uniquely obvious.

Adolescent↗
PubMed1996

Spontaneous resolution of soft-tissue interposition after closed reduction of hip endoprosthesis dislocation.

Over a 5-year period at a single institution, 164 endoprostheses were used for the treatment of displaced femoral neck fractures. Soft-tissue restraint preservation and repair (hip capsule and labrum) is recommended to enhance stability after endoprosthesis placement. When dislocation does occur, however, this soft tissue may become interposed after closed reduction. This occurred in 2 of the dislocations reported here. In these 2 dislocations, despite the widened joint space, the range of motion was stable. Neither of these cases had a subsequent dislocation, and after 1 month, both had spontaneously narrowed their joint space back to the immediate postoperative state.

Aged↗
PubMed1996

Internal fixation of pelvic ring disruptions.

The internal fixation of pelvic ring fractures and dislocations has become more popular recently. Aggressive resuscitation of the injured patient includes pelvic stabilization and improves survival rates. Pelvic surgical exposures as well as the skeletal anatomy become more familiar as the orthopaedic surgeon gains experience in treating these difficult patients. Recent radiographic techniques for pelvic imaging facilitate comprehensive preoperative planning and intraoperative decision-making for pelvic injuries. Improved outcomes are expected as treatment is individualized for each patient.

Adolescent↗