Biomedical subjects

Nicholas J Giori

Publications and source records attributed to Nicholas J Giori.

12 recordsLinked to original sources

PubMed2007

Benefit of single-leaf resection for horizontal meniscus tear.

When treating a horizontal meniscus tear, the surgeon must decide whether to resect one or both leaves of the tear. We asked whether there is a biomechanical advantage to sparing one leaf when performing a partial meniscectomy for horizontal meniscus tear. We used pressure-sensitive film to measure the contact area, mean pressure, and peak pressure on the lateral tibial plateau of cadaveric sheep knees loaded to 2x body weight. For tears restricted to the posterior third, single-leaf resection decreased contact area by 40% compared with the intact case. Sparing one leaf was beneficial because resection of the second leaf reduced contact area an additional 15%. Similarly, mean pressure was increased 24% for single-leaf resection and an additional 27% for double-leaf resection. Peak pressure showed no differences with single- and double-leaf resections. For tears that span the entire meniscus, single-leaf resection reduced contact area by 59%, increased mean pressure by 55%, and increased peak pressure by 19%. Double-leaf resection in this situation did not change these values substantially, suggesting sparing one leaf offers no benefit over resecting both leaves with extensive horizontal meniscus tears.

Animals↗

PubMed2006

Intraoperative passive kinematics of osteoarthritic knees before and after total knee arthroplasty.

Total knee arthroplasty is a successful procedure to treat pain and functional disability due to osteoarthritis. However, precisely how a total knee arthroplasty changes the kinematics of an osteoarthritic knee is unknown. We used a surgical navigation system to measure normal passive kinematics from 7 embalmed cadaver lower extremities and in vivo intraoperative passive kinematics on 17 patients undergoing primary total knee arthroplasty to address two questions: How do the kinematics of knees with advanced osteoarthritis differ from normal knees?; and, Does posterior substituting total knee arthroplasty restore kinematics towards normal? Osteoarthritic knees displayed a decreased screw-home motion and abnormal varus/valgus rotations between 10 degrees and 90 degrees of knee flexion when compared to normal knees. The anterior-posterior motion of the femur in osteoarthritic knees was not different than in normal knees. Following total knee arthroplasty, we found abnormal varus/valgus rotations in early flexion, a reduced screw-home motion when compared to the osteoarthritic knees, and an abnormal anterior translation of the femur during the first 60 degrees of flexion. Posterior substituting total knee arthroplasty does not appear to restore normal passive varus/valgus rotations or the screw motion and introduces an abnormal anterior translation of the femur during intraoperative evaluation.

Aged↗

PubMed2006

Prepolarized magnetic resonance imaging around metal orthopedic implants.

A prepolarized MRI (PMRI) scanner was used to image near metal implants in agar gel phantoms and in in vivo human wrists. Comparison images were made on 1.5- and 0.5-T conventional whole-body systems. The PMRI experiments were performed in a smaller bore system tailored to extremity imaging with a prepolarization magnetic field of 0.4 T and a readout magnetic field of 27-54 mT (1.1-2.2 MHz). Scan parameters were chosen with equal readout gradient strength over a given field of view and matrix size to allow unbiased evaluation of the benefits of lower readout frequency. Results exhibit substantial reduction in metal susceptibility artifacts under PMRI versus conventional scanners. A new artifact quantification technique is also presented, and phantom results confirm that susceptibility artifacts improve as expected with decreasing readout magnetic field using PMRI. This proof-of-concept study demonstrates that prepolarized techniques have the potential to provide diagnostic cross-sectional images for postoperative evaluation of patients with metal implants.

Adult↗

PubMed2006

Gene regulation ex vivo within a wrap-around tendon.

This study tested the hypothesis that physiologic tendon loading modulates the fibrous connective tissue phenotype in undifferentiated skeletal cells. Type I collagen sponges containing human bone marrow stromal cells (MSCs) were implanted into the midsubstance of excised sheep patellar tendons. An ex vivo loading system was designed to cyclically stretch each tendon from 0 to 5% at 1.0 Hz. The MSC-sponge constructs were implanted into 2 tendon sites: the first site subjected to tension only and a second site located at an artificially created wrap-around region in which an additional compressive stress was generated transverse to the longitudinal axis of the tendon. The induced contact pressure at the wraparound site was 0.55 +/- 0.12 MPa, as quantified by pressure-sensitive film. An MSC-sponge construct was maintained free swelling in the same bath as an unloaded control. After 2 h of tendon stretching, the MSC-sponge constructs were harvested and real-time PCR was used to quantify Fos, Sox9, Cbfa1 (Runx2), and scleraxis mRNA expression as markers of skeletal differentiation. Two hours of mechanical loading distinctly altered MSC differentiation in the wrap-around region and the tensile-only region, as evidenced by differences in Fos and Sox9 mRNA expression. Expression of Fos mRNA was 13 and 52 times higher in the tensile-only and wrap-around regions, respectively, compared to the free-swelling controls. Expression of Sox9 mRNA was significantly higher (2.5-3 times) in MSCs from the wraparound region compared to those from the tensile-only region or in free-swelling controls. In contrast, expression levels for Cbfa1 did not differ among constructs. Scleraxis mRNA was not detected in any construct. This study demonstrates that the physiologic mechanical environment in the wrap-around regions of tendons provides stimuli for upregulating early response genes and transcription factors associated with chondrogenic differentiation. These differentiation responses begin within as little as 2 h after the onset of mechanical stimulation and may be the basis for the formation of fibrocartilage that is typically found in the wrap-around region of mature tendons in vivo.

Animals↗

PubMed2006

Bone cement improves suture anchor fixation.

Suture anchor fixation failure can occur if the anchor pulls out of bone. We hypothesized that suture anchor fixation can be augmented with polymethylmethacrylate cement, and that polymethylmethacrylate can be used to improve fixation in a stripped anchor hole. Six matched cadaveric proximal humeri were used. On one side, suture anchors were placed and loaded to failure using a ramped cyclic loading protocol. The stripped anchor holes then were injected with approximately 1 cc polymethylmethacrylate, and anchors were replaced and tested again. In the contralateral humerus, polymethylmethacrylate was injected into anchor holes before anchor placement and testing. In unstripped anchors, polymethylmethacrylate increased the number of cycles to failure by 34% and failure load by 71% compared with anchors not augmented with polymethylmethacrylate. Polymethylmethacrylate haugmentation of stripped anchors increased the cycles to failure by 31% and failure load by 111% compared with unstripped uncemented anchors. No difference was found in cycles to failure or failure load between cemented stripped anchors and cemented unstripped anchors. Polymethylmethacrylate can be used to augment fixation, reducing the risk of anchor pull-out failure, regardless whether the suture anchor hole is stripped or unstripped.

Aged↗

PubMed2006

The high variability of tibial rotational alignment in total knee arthroplasty.

Although various techniques are advocated to establish tibial rotational alignment during total knee arthroplasty, it is unknown which is most repeatable. We evaluated the precision and accuracy of five tibial rotational alignment techniques to determine whether computer-assisted navigation systems can reduce variability of tibial component rotational alignment when compared to traditional instrumentation. Eleven orthopaedic surgeons used four computer-assisted techniques that required identification of anatomical landmarks and one that used traditional extramedullary instrumentation to establish tibial rotational alignment axes on 10 cadaver legs. Two computer-assisted techniques (axes between the most medial and lateral border of the tibial plateau, and between the posterior cruciate ligament [PCL] and the anterior tibial crest) and the traditional technique were least variable, with standard deviations of 9.9 degrees, 10.8 degrees, and 12.1 degrees, respectively. Computer-assisted techniques referencing the tibial tubercle (axes between the PCL and the medial border or medial 1/3 of the tubercle) were most variable, with standard deviations of 27.4 degrees and 28.1 degrees. The axis between the medial border of the tibial tubercle and the PCL was internally rotated compared to the other techniques. None of the techniques consistently established tibial rotational alignment, and navigation systems that establish rotational alignment by identifying anatomic landmarks were not more reliable than traditional instrumentation.

Arthroplasty, Replacement, Knee↗

PubMed2005

Evaluation of methods that locate the center of the ankle for computer-assisted total knee arthroplasty.

Accurate alignment of the mechanical axis of the limb is important to the success of a total knee arthroplasty. Although computer-assisted navigation systems can align implants more accurately than traditional mechanical guides, the ideal technique to determine the distal end point of the mechanical axis, the center of the ankle, is unknown. In this study, we evaluated the accuracy, precision, objectivity, and speed of five anatomic methods and two kinematic methods for estimating the ankle center in 11 healthy subjects. Magnetic resonance images were used to characterize the shape of the ankle and establish the true ankle center. The most accurate and precise anatomic method was establishing the midpoint of the most medial and most lateral aspects of the malleoli (4.5 +/- 4.1 mm lateral error; 2.7 +/- 4.5 mm posterior error). A biaxial model of the ankle (2.0 +/- 6.4 mm medial error; 0.3 +/- 7.6 mm anterior error) was the most accurate kinematic method. Establishing the midpoint of the most medial and most lateral aspects of the malleoli was an accurate, precise, objective, and fast method for establishing the center of the ankle.

Ankle Joint↗

PubMed2005

The variability of femoral rotational alignment in total knee arthroplasty.

BACKGROUND: Several reference axes are used to establish femoral rotational alignment during total knee arthroplasty, but debate continues with regard to which axis is most accurately and easily identified during surgery. Computer-assisted navigation systems have been developed in an attempt to more accurately and consistently align implants during total knee arthroplasty, but it is unknown if navigation systems can improve the accuracy of femoral rotational alignment as compared with that achieved with more traditional techniques involving mechanical guides. The purposes of the present study were to characterize the variability associated with femoral rotational alignment techniques and to determine whether the use of a computer-assisted surgical navigation system reduced this variability. METHODS: Eleven orthopaedic surgeons used five alignment techniques (including one computer-assisted technique and four traditional techniques) to establish femoral rotational alignment axes on ten cadaveric specimens, and the orientation of these axes was recorded with use of a navigation system. These derived axes were compared against a reference transepicondylar axis on each femur that was established after complete dissection of all soft tissues. RESULTS: There was no difference between the mean errors of all five techniques (p > 0.11). Only 17% of the knees were rotated <5 degrees from the reference transepicondylar axis, with alignment errors ranging from 13 degrees of internal rotation to 16 degrees of external rotation. There were significant differences among the surgeons with regard to their ability to accurately establish femoral rotational alignment axes (p < 0.001). CONCLUSIONS: All techniques resulted in highly variable rotational alignment, with no technique being superior. This variability was primarily due to the particular surgeon who was performing the alignment procedure. A navigation system that relies on directly digitizing the femoral epicondyles to establish an alignment axis did not provide a more reliable means of establishing femoral rotational alignment than traditional techniques did.

Arthroplasty, Replacement, Knee↗

PubMed2004

Load-shifting brace treatment for osteoarthritis of the knee: a minimum 2 1/2-year follow-up study.

Objectives in treating primarily unicompartmental knee arthritis with a load-shifting brace are pain relief, compliance, brace durability, and complication-free treatment over multiple years. This was a single institution retrospective chart review, radiograph review, and telephone survey of patients treated from 1997 to 1999 with a load-shifting knee brace. Forty-six patients (49 knees) with a minimum 2 1/2-year follow-up (average 3.3 years) were reviewed. Kaplan-Meier survivorship analysis revealed that load-shifting brace use had a survival of 76% at 1 year, 69% at 2 years, and 61% at 3 years. Younger patients had a higher likelihood of longer brace use than older patients. One patient had ipsilateral leg swelling and a pulmonary embolus after initiating bracing. Eliminating the high numbers of early failures would be desirable. One should be aware of the potential complication of venous thrombosis and thromboembolism.

Braces↗

PubMed2003

Offset acetabular components introduce torsion on the implant and may increase the risk of fixation failure.

Loading of an offset acetabular component causes torsion on the implant around the center of the reamed acetabular bed. A mechanical analysis was performed to determine this torsional moment. A 70 kg person walking normally on a well-positioned, 4-mm offset acetabular component will produce torsion on the prosthesis of approximately 3.86 Nm. A 10-mm offset increases the applied torsion to 9.65 Nm. Vertical placement of the cup further increases this torsion. These torsional moments are comparable to moments shown to cause failure of the initial interference fit of cementless acetabular components in vitro. If using an offset cementless acetabular component, one should initially limit weight bearing and consider using pegs or screws to augment fixation and minimize the risk of interference fit failure.

Acetabulum↗

PubMed2003

Acetabular retroversion is associated with osteoarthritis of the hip.

Primary osteoarthritis of the hip may have a structural basis. It was hypothesized that the radiographic appearance of acetabular retroversion could be created by altering the morphologic features of the acetabular walls, and that acetabular retroversion, as defined on an anteroposterior radiograph of the pelvis, is associated with osteoarthritis of the hip. A model pelvis was used to simulate normal, augmented, deficient, and rotated walls of the acetabulum, and radiographs were taken to compare the projections of the modified acetabular walls with the known plain radiographic appearance of a retroverted acetabulum. One hundred thirty-one good quality anteroposterior radiographs of the pelvis taken before total hip arthroplasty for idiopathic hip osteoarthritis were compared with 99 good quality radiographs taken for nonorthopaedic reasons. The prevalence of radiographic acetabular retroversion is 20% among patients with idiopathic hip osteoarthritis and 5% among the general population. The appearance of acetabular retroversion on an anteoroposterior radiograph of the pelvis is created by deficiency of the posterior wall of the acetabulum. There is a statistically significant association between radiographic acetabular retroversion and hip osteoarthritis. These findings have applicability to understanding the mechanical etiology of hip osteoarthritis, and to surgical technique during periacetabular osteotomy and total hip arthroplasty.

Acetabulum↗

PubMed2002

Total knee arthroplasty in limbs affected by poliomyelitis.

BACKGROUND: Little information is available regarding the results and complications of total knee arthroplasty in limbs affected by poliomyelitis with severe knee degeneration. METHODS: We performed a retrospective chart and radiograph review of patients with a history of poliomyelitis involving a limb that subsequently underwent primary total knee arthroplasty between 1970 and 2000. Sixteen total knee arthroplasties were performed in limbs affected by poliomyelitis in fifteen patients. Eleven patients were followed for a minimum of two years, one (two knees) died before the minimum two-year follow-up could be completed, and three were followed for less than two years. No patient was lost to follow-up. RESULTS: There were two periprosthetic fractures, one peroneal nerve palsy, one avulsion of the patellar tendon, and four cases of recurrent instability. These complications were related to the poor bone quality, valgus deformity, patella baja, poor musculature, and attenuated soft tissues commonly found in knees affected by poliomyelitis. Knee Society pain and knee scores were improved postoperatively for all nine knees with a two-year follow-up that had had at least antigravity quadriceps strength prior to surgery. However, Knee Society function scores remained at 0 or worsened for six of the eleven knees followed for at least two years, including those with less than antigravity strength, and four of the nine knees with at least antigravity strength. None of the prostheses loosened. CONCLUSIONS: Pain and knee scores improved following total knee arthroplasty in patients with a history of poliomyelitis and antigravity quadriceps strength, but there was less pain relief in patients with less than antigravity quadriceps strength. Recurrence of instability and progressive functional deterioration is possible in all knees affected by poliomyelitis that have undergone total knee replacement, but they appear to occur more commonly in more severely affected knees.

Aged↗