Biomedical subjects

P C Noble

Publications and source records attributed to P C Noble.

At least 19 recordsLinked to original sources

PubMed2006

Cellular events leading to chondrocyte death after cartilage impact injury.

OBJECTIVE: We undertook this study to test our postulate that leukocytes extend the zone of injury in cartilage after acute mechanical trauma. METHODS: Fresh cadaveric canine femoral condyles were subjected to 20-25-MPa impact injury. Condyle explants or dispersed chondrocytes were cultured with autologous blood mononuclear leukocytes (MNLs). Viability of chondrocytes at varying distances from the impact site was assessed by trypan blue exclusion. RESULTS: Mechanical injury caused a significant loss of viable chondrocytes over 7 days, even in cartilage >10 mm from the impact site. After biomechanical stress, death of cells within 10 mm of the impact could be largely prevented by addition of N(G)-monomethyl-L-arginine to inhibit nitric oxide (NO) generation. Chondrocytes within 10 mm of the impact were also susceptible to killing by living MNLs, but not by incubation with the supernatants of endotoxin-activated MNLs. Chondrocytes in this vulnerable zone expressed intercellular adhesion molecule 1 (ICAM-1) (CD54), facilitating attachment of MNLs that localized adjacent to the chondrocytes. Leukocytes killed dispersed chondrocytes harvested from the impact zone by generation of reactive oxygen species. Leukocyte-mediated killing could be blocked by desferoxamine or by antibodies to CD18, which prevent attachment of leukocytes to ICAM-1-expressing chondrocytes. CONCLUSION: Our data suggest that after mechanical injury, chondrocytes distant from the site may be killed through the generation of NO. Inflammatory leukocytes further extend the zone of chondrocyte death by adhering to chondrocytes expressing ICAM-1 and by inducing the accumulation of free oxygen radicals in the chondrocyte cytoplasm. Patients may benefit from therapies that reduce infiltration of inflammatory leukocytes into acutely injured cartilage.

Animals↗

PubMed2006

CT analysis of defects of the cement mantle and alignment of the stem: in vitro comparison of Charnley-Kerboul femoral hip implants inserted line-to-line and undersized in paired femora.

Using a modern cementing technique, we implanted 22 stereolithographic polymeric replicas of the Charnley-Kerboul stem in 11 pairs of human cadaver femora. On one side, the replicas were cemented line-to-line with the largest broach. On the other, one-size undersized replicas were used (radial difference, 0.89 mm sd 0.13).CT analysis showed that the line-to-line stems without distal centralisers were at least as well aligned and centered as undersized stems with a centraliser, but were surrounded by less cement and presented more areas of thin (< 2 mm) or deficient (< 1 mm) cement. These areas were located predominantly at the corners and in the middle and distal thirds of the stem. Nevertheless, in line-to-line stems, penetration of cement into cancellous bone resulted in a mean thickness of cement of 3.1 mm (sd 0.6) and only 6.2% of deficient and 26.4% of thin cement. In over 90% of these areas, the cement was directly supported by cortical bone or cortical bone with less than 1 mm of cancellous bone interposed. When Charnley-Kerboul stems are cemented line-to-line, good clinical results are observed because cement-deficient areas are limited and are frequently supported by cortical bone.

Arthroplasty, Replacement, Hip↗

PubMed2006

Effect of early full weight-bearing after joint injury on inflammation and cartilage degradation.

BACKGROUND: Early full weight-bearing after an acute osteochondral injury avoids problems associated with immobility but may also be harmful by amplifying the inflammatory response. To investigate these effects, we developed an in vivo model of subchondral trauma. METHODS: After an impact injury to the femoral condyle, fourteen dogs were randomized to immediate full weight-bearing or to four weeks of minimal weight-bearing before full weight-bearing. Synovial fluid was sampled by aspiration at one, two, four, eight, twelve, sixteen, twenty, and twenty-four weeks. Neutrophils, monocytes, and lymphocytes were enumerated, and the concentrations of tumor necrosis factor-alpha, interleukin-10, nitric oxide, matrix metalloproteinases, and glycosaminoglycans were measured. RESULTS: Compared with the findings for uninjured joints, the synovial fluid from the impacted joints of full-weight-bearing dogs had significantly higher peak concentrations of neutrophils (p = 0.0006 at one week), mononuclear leukocytes (p = 0.001 at four weeks), tumor necrosis factor-alpha (p = 0.001 at one week), nitric oxide (p = 0.001 at one week), matrix metalloproteinases (p = 0.008 at one week), and glycosaminoglycans (p = 0.002 at four weeks and p = 0.001 at six months). The size of the bone bruise correlated with the peak concentrations of tumor necrosis factor-alpha (r2= 0.89, p = 0.007; Spearman rank test), matrix metalloproteinases (r2= 0.96, p = 0.0004), and glycosaminoglycans (r2= 0.96, p = 0.0004). However, restriction to minimal weight-bearing for four weeks after the injury led to a significant reduction in the synovial fluid concentrations of neutrophils (p = 0.007 at one week and p = 0.01 at two weeks), tumor necrosis factor-alpha (p = 0.0006 to 0.02 during the first four weeks), nitric oxide (p = 0.001 to 0.04 during the first four weeks), and matrix metalloproteinases (p = 0.007 to 0.01 from the second week to the eighth week). In contrast, interleukin-10 concentrations were significantly higher (p = 0.002 at one week) and glycosaminoglycan levels remained at normal levels in animals that were restricted from immediate full weight-bearing after the injury. CONCLUSIONS: The magnitude of the inflammatory response is proportional to the size of the bone bruise. Restriction to minimal weight-bearing for four weeks reduces the magnitude of the inflammatory response and the cartilage degradation following articular cartilage impact injury. CLINICAL RELEVANCE: Strategies to minimize mechanical stress during the early postinjury period may help to preserve cartilage integrity and forestall the development of osteoarthritis.

Animals↗

PubMed2004

Brief report: validation of a system for automated measurement of knee laxity.

OBJECTIVE: To determine the accuracy and repeatability of an automated quantitative fluoroscopic imaging system for measuring knee laxity. DESIGN: Cadaveric validation study. BACKGROUND: Current methods of measuring anterior-posterior laxity lack sufficient accuracy and repeatability. A commercially developed fluoroscopic software package, capable of measuring laxity, required validation. METHODS: Five human cadaveric knees were used. A constant force of 130 N was applied anteriorly and posteriorly in turn to the tibia of each knee with the femur fixed in 30 degrees and 90 degrees of flexion. Quantitative fluoroscopic measurements of anterior-posterior laxity were determined using image analysis software. Fluoroscopic results were compared to the true anterior-posterior displacements of the tibia, which were simultaneously recorded using linear transducers directly attached to the cadaveric specimens. RESULTS: The quantitative fluoroscopic method underestimated laxity by an average of 0.40 mm with a root mean square error of 0.49 mm. The 95% confidence intervals for anterior and posterior laxity error were calculated to be -0.99 to 0.25 mm and -0.89 to 0.03 mm, respectively, where a negative error represents an underestimation. CONCLUSIONS: The quantitative fluoroscopic method offers a dramatic improvement in accuracy over current laxity measurement techniques and acceptable repeatability for assessing ligament damage. RELEVANCE: The considerably more accurate, validated measurement system of this study could improve ligament assessment and diagnosis, and the recognition of injuries otherwise undetected with current methods.

Fluoroscopy↗

PubMed2001

Interactive effects of tunnel dilation on the mechanical properties of hamstring grafts fixed in the tibia with interference screws.

The effect of dilation of the tibial tunnel on the strength of hamstring graft fixation using interference screws was evaluated. In all, 28 RCI screws were tested in male human tibia-hamstring constructs with tibial tunnels reamed or dilated to the respective size of the graft diameter. Dilation of the tibial tunnel failed to significantly enhance hamstring fixation. Grafts secured in dilated tunnels displayed an 11% greater resistance to the initiation of graft slippage (174+/-112 N) compared to their undilated controls (156+/-77 N, P=0.63). Dilation of the tibial tunnel increased the failure load by an average of 4%, independent of screw diameter (dilated specimens: 360+/-120 N, controls: 345+/-88 N, P=0.74). Biomechanical research on the effect of tibial tunnel dilation in hamstring fixation has not provided satisfactory evidence as to the benefits of this additional surgical step during anterior cruciate ligament (ACL) reconstruction.

Anterior Cruciate Ligament↗

PubMed2001

Experimental and computational simulation of total hip arthroplasty dislocation.

Other than fatal pulmonary embolism and deep infection, dislocation following total hip replacement remains probably the most vexing complication to patient and surgeon. Subluxation and dislocation are complex, poorly understood phenomena. Many important questions in this area unfortunately do not lend themselves well to clinical or registry study. Appropriate realistic laboratory models have been lacking. This article synthesizes new work undertaken independently by two groups of biomechanical investigators using very different, but complimentary, methodologies to study the mechanisms of dislocation, and especially the influence of specific design and surgical variables.

Arthroplasty, Replacement, Hip↗

PubMed2001

The watershed labral lesion: its relationship to early arthritis of the hip.

This study examined the hypothesis that labral lesions contribute to early degenerative hip disease. Between 1993 and 1999, 436 consecutive hip arthroscopies were performed by the senior author (J.C.M.). In addition, 54 acetabula were harvested from human adult cadavers and 10 hips underwent microangiography to determine labral blood supply. Of the 436 arthroscopic patients, 241 (55.3%) had a total of 261 labral tears, all located at the articular, not capsular, margin of the labrum. Stereomicroscopic examination of the 54 cadaver acetabula revealed a total of 52 labral lesions. Overall, there was no significant difference between the arthroscopic and cadaver populations in terms of the incidence of labral tears (P=.315). There was a high association between labral lesions and adjacent acetabular chondral damage. Arthroscopic and anatomic observations support the concept that labral disruption and degenerative joint disease frequently are part of a continuum of joint pathology.

Acetabulum↗

PubMed2001

The Otto E. Aufranc Award: The role of labral lesions to development of early degenerative hip disease.

The current authors examined the hypothesis that labral lesions contribute to early degenerative hip disease. Between 1993 and 1999, 436 consecutive hip arthroscopies were done by the senior author. In addition, 54 acetabula were harvested from human adult cadavers. Two hundred forty-one of the 436 (55.3%) patients who had arthroscopies had a 261 labral tears, all located at the articular, not capsular margin of the labrum. Stereomicroscopic examination of the 54 acetabula from cadavers revealed 52 labral lesions. Overall, there was no significant difference between the arthroscopic and cadaveric populations in terms of the incidence of labral tears. (Overall, 73% of patients with fraying or a tear of the labrum had chondral change. Arthroscopic and anatomic observations support the concept that labral disruption and degenerative joint disease are frequently part of a continuum of joint disease.

Acetabulum↗

PubMed2001

Calcaneocuboid stability: a clinical and anatomic study.

Injuries to the midtarsal joints are relatively uncommon and often unrecognized entities. Acute and chronic instability patterns to the calcaneocuboid joint can occur from such injuries. No previous determinations of normal calcaneocuboid laxity have been reported. Utilizing a previously described technique, stress radiographs were performed in human cadaveric specimens following serial sectioning of the ligamentous supports of the calcaneocuboid joint. Significant differences in calcaneocuboid gap and angle occurred between unstressed and stressed conditions. Cadaveric specimen testing determined that the dorsal and plantar calcaneocuboid ligaments both provide significant contributions to joint stability. Prior to defining pathologic states of joint laxity, normal ranges of stability must be determined. By more clearly defining normal stability of the calcaneocuboid joint and its ligamentous contributions, greater insight into the diagnosis and treatment of calcaneocuboid instability can be obtained.

Adult↗

PubMed2000

Long-term residual musculoskeletal deficits after femoral shaft fractures treated with intramedullary nailing.

BACKGROUND: Locked intramedullary (IM) nailing has been recognized as one of the most reliable methods for treatment of femoral shaft fractures. Although IM nails are routinely used in the treatment of these fractures, the long-term effects of retained IM nails are unknown. METHODS: Seventeen patients with radiographically documented healed fracture of femoral diaphysis after locked IM nailing technique were evaluated at a follow-up of at least 18 months postoperatively. All patients had returned to their preinjury level of function and activity before the study. The bone mineral densities (BMD) of the injured and contralateral femora were measured using dual energy x-ray absorptiometry (DEXA). BMD of symmetrical regions in the femoral neck and medial and lateral femoral cortex of the implanted and contralateral femora were compared. Postinjury muscle function was assessed from measurement of the isometric strength of six separate muscle groups (quadriceps, hamstrings, hip extensors, hip flexors, hip abductors, and hip adductors) in treated and control extremities. RESULTS: The average BMD of the femoral neck region of instrumented femora was 9% less than in contralateral control. Within the medial cortex, BMD of the control femora was an average of 20% greater than in the implanted side. In the lateral cortex, the difference averaged 13%. The isometric dynamometric data demonstrated a statistically significant reduction in the strength of the quadriceps of the instrumented extremities as compared with the contralateral ones. There was no significant difference in the strength of the hamstrings, hip extensors, hip flexors, abductors, or adductors. In the control extremities, the average torque generated by isometric contraction of the quadriceps was 3.45+/-1.35 times greater than by the hamstrings. Torque in extension/flexion and abduction/adduction was also observed. CONCLUSION: Our data suggest that limbs with long-term retained IM nails experience a significant reduction in the femur BMD and quadriceps muscle strength. These findings may not be simply related to the implant, and further study is warranted to determine the causes of these changes.

Adolescent↗

PubMed1999

Femoral ring versus fibular strut allografts in anterior lumbar interbody arthrodesis. A biomechanical analysis.

STUDY DESIGN: A comparison between femoral ring and fibular strut allografts in anterior lumbar interbody arthrodesis, as assessed by biomechanical analysis. OBJECTIVES: To assess the difference in stability and rigidity provided by the femoral ring allograft versus that provided by fibular strut allograft. SUMMARY OF BACKGROUND DATA: Two commonly used techniques for spinal arthrodesis at L4-L5 include the femoral ring allograft and the fibular strut allograft. The postoperative stability has not been evaluated biomechanically. METHODS: An anterior lumbar interbody fusion on seven cadaveric specimens was performed using femoral ring and fibular strut allografts. Biplanar radiography was used to measure the 6 degrees of motion of L4 with respect to L5 during a range of loading maneuvers. RESULTS: When an extension moment was applied, the femoral ring allograft extended 4.2 degrees more than the intact specimen, compared with 1.6 degrees with the fibular strut allograft (P = 0.18). When the flexion moment was imposed, lateral bending increased by 2.2 degrees with the femoral ring, compared with 0.7 degree with the fibular strut allograft (P = 0.06). During lateral bending, increased lateral translation was observed to be 0.9 mm with the fibular strut allograft compared with 1.4 mm with the femoral ring allograft (P = 0.06). CONCLUSIONS: Although not statistically significant, the fibular strut allograft creates a more rigid construct immediately after surgery during flexion-extension, lateral bending angulations, and lateral translation. One should consider using the fibular strut allograft over the femoral ring allograft, as it is more stable and rigid construct in the immediate postoperative period.

Aged↗

PubMed1999

Predicting the position of the femoral head center.

To find an accurate method to predict the position of the normal head center in severely deformed hips without a contralateral reference, we studied the relationships between the head center and dimensions of the normal proximal femur using cadaveric specimens. From a large anatomic collection, 32 cadaveric femora with neck-shaft angles ranging from 115 to 146 were selected. The two parameters with the greatest correlation with the height of the femoral head were the height of the neck isthmus (r = .932) and the lowest point of neck saddle (r = .790). Medial head offset was most strongly correlated with the offset of the neck isthmus (r = .945) and the distance from the medullary axis to the outer borders of the medial cortex at the +30% level (r = .861). As a rule of thumb, the height of the head center can be predicted as the height of the midpoint of the neck isthmus plus 10 mm or as the height of the neck saddle with an accuracy of +/-5.1 mm and +/-8.3 mm. The offset of the head center can be predicted as the offset of the midpoint of the neck isthmus plus 15 mm or as the distance from the medullary axis to the medial cortex at the +30% level plus 15 mm with an accuracy of +/-4.6 mm and +/-6.3 mm.

Adult↗

PubMed1999

Quantitative assessment of the midcarpal shift test.

The subjective, clinical midcarpal shift test was compared with a quantitative measurement of carpal volar/dorsal translation versus ulnar deviation using a mechanical testing system. Testing was performed on 19 healthy volunteers (mean age, 33 years) and 3 patients (four wrists; mean age, 23 years) who had been diagnosed with ulnar midcarpal instability, a nondissociative form of carpal instability. During physical examination, each subject's wrist was graded I to V using the previously described classification of the degree of laxity and clunk observed with the midcarpal shift test. Each subject was also evaluated using a quantitative mechanical testing system that simulates the subjective clinical test. The testing system measures displacement of the distal carpal row, more specifically, the capitate, as the wrist is moved from neutral to ulnar deviation under a constant axial load of 44 N directed volarly at the head of the capitate. Reflective markers were attached to the skin above the proximal and distal ends of the third metacarpal and at the point where the 44-N load was applied to the carpus. Motion of the markers was used to calculate ulnar deviation and dorsal/volar translation of the carpus. The maximum slope of the carpal translation versus ulnar deviation curve was measured for each subject and compared with the results of the clinical midcarpal shift test. Higher maximum slopes were seen in subjects with the higher grades of carpal laxity. There were also differences with regard to the point at which the clunk occurred; the higher the clinical grade of laxity, the greater the ulnar deviation of the wrist at the point at which the clunk was observed. These differences were not significant, however. These data confirm the validity of the clinical test and establish its usefulness as a diagnostic indicator of midcarpal nondissociative carpal instability. The mechanized test also may be useful as a biomechanical marker, enabling the results of ligament sectioning to be effectively compared with defined clinical laxity.

Adult↗

PubMed1999

Open versus closed repair of the Achilles tendon: an experimental animal study.

This experimental animal study compared the healing patterns between open and closed treatments of Achilles tendon tenotomies. Twenty-four male New Zealand rabbits underwent tenotomy of the left Achilles tendon and were randomized into two groups, treated with either open surgical repair or closed management. After the death of the animal, the retrieved tendons were submitted for biomechanical and histological testing. The total elongation of the open treatment group was 9.5+/-1.0 mm compared with 21.2+/-3.4 mm for the closed treatment group (P = 0.008), and the regain of stiffness was 67.4+/-2.0% and 48.9+/-5.3%, respectively (P = 0.132). Histological evaluation demonstrated similar healing patterns in both groups.

Achilles Tendon↗

PubMed1998

Morphology of the lumbar vertebral endplates.

STUDY DESIGN: The dimensions and shapes of vertebral body endplates of inferior L4, inferior and superior L5, and superior S1 were analyzed. Computed tomographic scans parallel to each endplate were used to develop a standardized geometric model of the boundaries of each vertebral body. OBJECTIVES: To provide a detailed analytic and geometric model of the vertebral endplates from the inferior surface of L4 to the superior surface of S1. SUMMARY OF BACKGROUND DATA: Although measurements of the sagittal and maximum transverse diameters of the vertebral bodies have been well documented, no study offers a complete geometric description of the shape of the endplates. Also, information acquired using the techniques of previous published reports may not provide measurements as accurate as those of the current investigation. METHODS: Twenty-five men and 21 women were studied. Computed tomographic scans of the endplates were digitized. The data were interpolated, and multivariate regression equations were derived to devise a standardized model. Measurements were taken, and the data were curve fitted to give best-fit equations for the standardized models. RESULTS: The endplates resembled a cardioid at the inferior L4 level and became more elliptical toward the superior S1 level. The sagittal and transverse diameters of the endplates of inferior L4, superior and inferior L5, and superior S1 are provided and compared with those reported in previous studies. CONCLUSION: Although the female endplates are smaller than their male counterparts, the overall shapes are similar.

Adult↗

PubMed1998

Proximal and distal femoral centralizers in modern cemented hip arthroplasty.

Third generation cementing techniques using intramedullary restrictors, low porosity cement with pressurization, lavage, and cement-stem bond enhancement do not prevent implant malalignment and inadequate cement mantle thickness. This has led to the development of modular proximal and distal centralizers to control the alignment of the femoral component and maintain an adequate thickness of the cement, thereby theoretically decreasing the rate of aseptic loosening. A retrospective analysis was performed of 100 primary cemented centralized femoral components. At an average followup of 5.7 years (range, 4-8 years), the average Harris Hip Score was 90. There were no cases of aseptic loosening, osteolysis, or impending failure. Ninety-one percent of femoral stems were implanted with satisfactory alignment with an optimal cement thickness. However, six distal centralizers and one proximal centralizer fractured at the time of insertion and voids frequently were seen in and around the distal centralizer. Although centralizers improve prosthesis alignment and cement mantle thickness, the long term effects of centralizer fracture and distal cement voids need to be observed to determine if centralizers improve previous implant survival.

Aged↗

PubMed1998

Pressurization and centralization enhance the quality and reproducibility of cement mantles.

Cementing technique has a profound influence on the incidence of aseptic loosening of total hip replacements. Two specific measures that seem to have the greatest impact on the longevity of cemented femoral stems are pressurization of cement and control of mantle thickness, typically through the use of modular centralizing devices attached to the tip of the prosthesis. Two laboratory studies are presented that examine the success of these measures in clinical practice. In the first study, the performance of five designs of intramedullary plugs in resisting migration during pressurization of cement was evaluated in human anatomic specimen femurs. Profound differences were observed between the performance of the different plug designs. In canals larger than 12 to 14 mm, most commercial devices failed to resist pressures greater than 30 to 40 pounds per square inch. Overall, it was estimated that between 6% to 76% of these devices would fail to resist cement pressures of 50 pounds per square inch in clinical practice. The second study examined the role of distal centralizers in the accumulation of air bubbles around the distal tip of the prosthesis during insertion of the stem into the femur. Acrylic replicas of a femoral stem were implanted in cavities simulating the femoral canal. Colored dyes, present within the cement, revealed the complex patterns of cement flow. It was shown that cement, dragged from the top of the femur, forms a thin layer that covers the entire surface of the prosthesis and the distal centralizer. Significant voids were present behind the trailing edges of the distal centralizer in 42% of the cases examined. These studies show that improvements in intramedullary plugs and stem centralizers are needed to increase the reproducibility of cement technique in total hip replacement.

Arthroplasty, Replacement, Hip↗

PubMed1998

Optimal location of a single distal interlocking screw in intramedullary nailing of distal third femoral shaft fractures.

OBJECTIVE: This biomechanical study was done to determine the effect of the level of a single distal screw in a static intramedullary (IM) femoral nail on the stability of fixation of a fracture in the distal third of the femur. DESIGN: Fifteen composite fiberglass femora were osteotomized transversely in the distal third of the femur. A Grosse-Kempf nail was implanted into the femurs, which were divided into three groups of five specimens. Single screw distal nail locking was varied distal to the osteotomy site for each group at 2.5, 5.0, and 7.5 centimeters, respectively. INTERVENTION: All instrumented femurs were mounted on a servohydraulic testing machine and fitted with transducers to measure axial, rotational, and bending displacements. Specimens were cyclically loaded (one hertz) in simultaneous torsion (moment: +/- 10 newton-meters) and axial compression (amplitude: 2,000 newtons) for 500 cycles with a 250-pound abductor force. MAIN OUTCOME MEASUREMENT: Data from linear and rotational transducers were sampled at 100 hertz for five cycles before cycling, every 100 cycles of loading, and immediately after cycling. Custom computer software was developed to convert transducer signals into static and dynamic measurements of axial motion (in millimeters), rotation (in degrees), and angulation (in degrees). RESULTS: Osteotomy site dynamic rotation increased significantly in specimens locked at 7.5 centimeters when compared with the 2.5-centimeter group. There was minimal difference between the stability of the 5.0-centimeter and 7.5-centimeter groups. There was no significant change in position at the fracture site before or after cyclic loading with respect to axial shortening, rotation, or bending. Both dynamic axial and angular displacements were also unaffected by screw position. CONCLUSION: The location of a single distal interlocking screw in static IM nail fixation of distal third femur fractures can significantly affect rotational stability but not axial or angular fixation.

Biomechanical Phenomena↗