Biomedical subjects

Philip C Noble

Publications and source records attributed to Philip C Noble.

At least 19 recordsLinked to original sources

PubMed2006

Posterior cruciate ligament substitution is not essential for excellent postoperative outcomes in total knee arthroplasty.

The study compared postoperative range of motion (ROM) and functional outcome of total knee arthroplasty (TKA) with a posterior cruciate ligament (PCL)-substituting knee prosthesis compared with an ultracongruent PCL-sacrificing design. Two hundred nine patients underwent primary TKA. Posterior stabilized design (121) and highly conforming, PCL-sacrificing, ultracongruent design (88) TKAs were reviewed. Surgeon, surgical approach, and a hyperflexion postoperative rehabilitation protocol were the same. Results showed significant improvement in knee flexion, ROM, Knee Score, and Function Score within each group. Postoperative mean total ROM was slightly higher with the posterior stabilized design. The 2 groups were the same postoperatively in the improvement in ROM, Knee Score, Function Score, satisfaction level, among other activity metrics. There was no clear evidence proving superiority and the need for posterior stabilization in PCL-sacrificing TKA.

Aged↗

PubMed2006

Does neck/liner impingement increase wear of ultrahigh-molecular-weight polyethylene liners?

We explore the hypothesis that repetitive impingement increases wear of ultrahigh-molecular-weight polyethylene inserts. During revision total hip arthroplasty, 113 acetabular components were retrieved and examined for impingement, backside wear, and articular wear. Sixty percent of acetabular liners showed evidence of prosthetic impingement, with moderate or severe damage to the rim in 32%. Moderate or severe backside damage was present in 31%. Backside wear was found in 61% (22/36) of liners exhibiting impingement vs 16% (12/73) of liners without impingement (P < .0001). The average articular wear rate of liners with moderate/severe impingement damage was 159 +/- 42 mm(3)/y, compared with 70 +/- 21 mm(3)/y for liners with no/mild impingement damage (P = .02). Repetitive impingement frequently occurs after total hip arthroplasty and leads to a multitude of adverse events, including motion between the liner and the acetabular shell.

Acetabulum↗

PubMed2006

The John Insall Award: Patient expectations affect satisfaction with total knee arthroplasty.

Satisfaction with the outcome of total knee arthroplasty is highly variable, with a small but significant percentage of patients reporting dissatisfaction with the procedure. The purpose of this study was to determine which factors contribute to patient satisfaction with total knee replacement (TKR), and their relative importance. At a minimum of 1 year post unilateral primary TKR, 253 patients completed a self-administered, validated "Knee Function Questionnaire," which examined each patient's participation in a broad range of activities involving the knee, their level of satisfaction, and the extent to which TKR had fulfilled their expectations. The association between function, expectation and satisfaction was examined using univariate and multivariate logistic regression. Seventy-five percent of patients were either "satisfied" or "very satisfied" with their knee replacement, while 14% were "dissatisfied" or "very dissatisfied." Satisfaction correlated significantly (p < 0.001) with age less than 60, absence of residual symptoms, fulfillment of expectations, and absence of functional impairment. Satisfaction with TKR is primarily determined by patients' expectations, and not their absolute level of function. Real improvements in the outcome of TKA must address prevention of residual pain, stiffness and swelling, and each patient's preoperative concept of the likely outcome of these procedures.

Adult↗

PubMed2005

Cracking and impingement in ultra-high-molecular-weight polyethylene acetabular liners.

The purpose of this study was to determine the prevalence of crack formation in conventional ultra-high-molecular-weight polyethylene cups and its association with rim impingement, oxidation, and time in situ. One hundred twenty acetabular cups were retrieved during revision total hip arthroplasty. In 40% (48/120) of the retrieved specimens, multiple subsurface cracks of several millimeters in length were revealed by transillumination. In 5 specimens, full thickness cracks led to fragmentation of the liner before revision. Thirty-eight (32%) liners had regions of moderate to severe impingement damage to the rim; cracks were initiated at the site of impingement in all but 1 liner (P < .0001). Cracks commonly occur in conventional ultra-high-molecular-weight polyethylene liners, often after neck impingement and almost always in association with oxidation of the polymer.

Acetabulum↗

PubMed2005

Celecoxib does not affect osteointegration of cementless total hip stems.

Celecoxib's effect on prosthetic osteointegration in patients undergoing total hip arthroplasty was studied. In a prospective, placebo-controlled, double-blind study of 49 patients, 24 were randomized to celecoxib (200 mg/d) and 25 to placebo over 6 weeks. Bone markers, N-teleopeptide, and bone-specific alkaline phosphatase were obtained postoperatively, and at 6 and 12 weeks. No radiographic prosthetic subsidence occurred. There were no significant differences from baseline in periprosthetic bone mineral density between the celecoxib and placebo groups at 3 and 6 months. There were no significant differences in baseline BSAlkP values between the 2 groups. At 6 and 12 weeks, average BSAlkP values increased. Urinary NTx concentrations followed a skewed distribution. Normalized NTx concentrations were statistically significantly greater in the celecoxib group than the placebo group at 6 weeks but not at 12 weeks.

Aged↗

PubMed2005

Does total knee replacement restore normal knee function?

Despite the advanced age of many patients having total knee arthroplasty, previous attempts to quantify patient function postoperatively have not allowed for normal deterioration of musculoskeletal function that occurs with aging. We determined the effects of aging on knee function, thereby providing a realistic level of normal, healthy knee function for patients and surgeons after total knee arthroplasties. A self-administered, validated knee function questionnaire consisting of 55 scaled multiple choice questions was used in this study. Responses were collected from 243 patients at least 1 year after they had total knee arthroplasties, and from 257 individuals (age- and gender-matched) who had no previous history of knee disorders. Many of these latter subjects reported that they could do most of the activities cited in the questionnaire without symptoms attributable to their knees. However, knee symptoms were experienced more frequently during activities that placed greater loads on the extremity. There was no difference in the knee function of men and women, and both groups had continuous deterioration in knee function with increasing age. There were large differences in the functional capacity to do activities involving the knee between the group of patients who had total knee arthroplasties and the age- and gender-matched patients with no previous knee disorders. Overall, 52% of the patients who had total knee arthroplasties reported some degree of limitation in doing functional activities, versus 22% of subjects with no previous knee disorders. Two groups of activities were identified: activities in which the patients and control subjects had essentially similar knee function (swimming, golfing, and stationary biking), and activities in which the function scores of the control group exceeded the scores of the patients who had total knee arthroplasties (kneeling, squatting, moving laterally, turning and cutting, carrying loads, stretching, leg strengthening, tennis, dancing, gardening, and sexual activity). Our data show that many of the limitations reported by patients after total knee arthroplasties are shared by individuals with no previous knee disorders. However, only approximately 40% of the functional deficit present after a total knee arthroplasty seems to be attributable to the normal physiologic effects of aging. Patients who had total knee replacements still experienced substantial functional impairment compared with their age- and gender-matched peers, especially when doing biomechanically demanding activities. This suggests that significant improvements in the procedure and prosthetic designs are needed to restore normal knee function after a total knee arthroplasty.

Adult↗

PubMed2005

Long-term results of the dial osteotomy in the treatment of high-grade acetabular dysplasia.

UNLABELLED: The dial osteotomy, an acetabular reorientation procedure based on radiographs, was developed by R. H. Eppright for treatment of hip dysplasia; however, long-term results are not recorded. The aim of this study was to evaluate retrospectively the results of the dial osteotomy as done in 37 patients (44 hips) at an average followup of 12.6 years. Articular pressures with the application of a time and pressure algorithm were calculated from radiographs to correlate calculated intraarticular pressures with progression of degenerative disease. Clinical results at followup were 32 (73%) satisfactory and 12 (27%) unsatisfactory hips. Six (13%) hips failed between 10-20 years (average 14.7 years). A satisfactory result correlated with the preoperative functional score. Radiographically, the anterior center-edge angle increased from an average of 6.7 degrees to 37.9 degrees. At followup, radiographic indices of degeneration indicated that eight (18%) hips had improved, 18 (41%) had stabilized, and 18 (41%) had deteriorated. Severin indices improved in 21 (48%) hips. Joint space width at followup provided the only correlation between radiographic parameters and clinical result. Contact pressures were reduced from 4.45 MPa to 1.12 MPa. The cumulative exposure to articular pressures averaged 61.6 MPa-years, and did not correlate with radiographic parameters or clinical success. LEVEL OF EVIDENCE: Therapeutic study, Level IV (case series--no, or historical control group). See the Guidelines for Authors for a complete description of levels of evidence.

Acetabulum↗

PubMed2005

Computerized matching of autologous femoral grafts for the treatment of medial talar osteochondral defects.

BACKGROUND: Cored autologous graft from the distal ipsilateral femur has been used to fill osteochondral defects in the talus. There are no studies that compare the articular morphology of potential donor sites on the distal femur with recipient sites on the talus. METHODS: Using coronal MRI of the talus and distal femur of five matched cadaver, computer reconstructions of the articular surfaces were prepared. From these, six 10-mm in diameter donor sites from the nonweightbearing surfaces of the medial and lateral aspects of the femoral condyles were matched to three recipient sites on the anterior, middle, and posterior aspects of the corresponding medial talus using customized computer software that minimized differences between the articular surfaces of the graft and the talus. After matching the femoral to the talar graft, the average and maximal distances between the surfaces (surface contour) and the average and maximal distances of the offset at the outer 1 mm of the graft periphery (step-off) were determined. RESULTS: For all graft combinations, the average step-off was 0.24 +/- 0.03 mm and the maximum 0.60 mm. The average surface contour was 0.32 +/- 0.04 mm and the maximum was 1.16 mm. In all cases, the best donor site was from the superolateral femur for any medial talar lesion. CONCLUSION: In this study of grafts from the femoral condyles, the superolateral femur was the optimal location for an osteochondral graft for any medial talar lesion.

Bone Transplantation↗

PubMed2005

Surface damage of patellar components used in total knee arthroplasty.

BACKGROUND: Patellofemoral complications are a common cause of failure of total knee replacement. In this study, we examined eighty-five patellar components that had been retrieved for a variety of reasons after a mean of 71.9 months in vivo. The objective of this study was to identify factors contributing to surface damage of patellar components in total knee replacements. METHODS: The retrieved patellar components were of three primary designs: dome-shaped, sombrero-shaped, and pseudo-anatomic. Five zones on each specimen were evaluated for five different types of damage (creep, pitting, delamination, abrasion, and burnishing). The severity of the damage was assigned a score of 0 to 4, with 0 indicating no damage and 4 indicating extreme damage. The extent of the damage was also assigned a score of 0 to 4, with 0 indicating 0% and 4 indicating 76% to 100%. An asymmetry ratio was calculated for each damage pattern to evaluate the uniformity of the distribution of the damage across each component. RESULTS: Eighty-six percent of the components had a damage score of > or =4 (product of the extent and severity scores) for at least one damage mechanism (creep for 38% of the components, pitting for 47%, delamination for 26%, abrasion for 49%, and burnishing for 76%). Components that had been in situ for more than two years had significantly more severe creep, delamination, and burnishing than components that had been in place for less than two years. Metal-backed designs had more severe damage than all-polyethylene components. Factors that reduced the occurrence and severity of polyethylene damage were a congruent patellar design (a non-dome-shaped component) and the use of an asymmetric femoral component. CONCLUSIONS: Damage to the patellar component was a common finding, particularly when the implant had been retrieved more than two years after implantation. Moreover, delamination was frequently found on the patellar components, as has been observed by others who examined retrieved tibial inserts. The results of this study suggest that the use of congruent patellar components may reduce damage.

Adult↗

PubMed2005

Backside wear of polyethylene tibial inserts: mechanism and magnitude of material loss.

BACKGROUND: Wear of the underside of modular tibial inserts (backside wear) in total knee replacements has been reported by several authors. Although, for some implant designs, this phenomenon seems to contribute to osteolysis, the actual volume of material lost through wear of the backside surface has not been quantified. This study describes the results of computerized measurements of tibial inserts of one design known to be associated with a high prevalence of backside wear in situ. METHODS: A series of retrieved total knee components of one design were examined. The duration of implantation of the retrieved components ranged from thirty-six to 146 months. Laser surface profilometry and computer-aided design software were used to develop individual three-dimensional models of each worn, retrieved tibial insert to compare with scanned unused inserts. Volumetric subtraction of both models revealed the material lost because of backside wear. RESULTS: Worn and unworn areas on the backside surface were easily identified by stereomicroscopy and laser profilometry. The computer reconstructions showed that, in all retrievals, all unworn surfaces on the nonarticulating surface lay in one plane. The average volume (and standard deviation) of the material lost because of backside wear was 925 +/- 637 mm(3) (range, 197 to 2720 mm(3)). On the basis of the time in situ for each implant, the average volumetric wear rate was 138 +/- 95 mm(3)/yr. CONCLUSIONS: The predicted volume of material removed because of backside wear is substantial and may be sufficient to induce osteolysis. Our results suggest that peg-like protrusions are not generated by the extrusion of polyethylene into screw-holes within the base-plate but by abrasion of the underside of the bearing insert, leaving the protruding pegs as the only remnants of the original surface.

Aged↗

PubMed2004

Direct measurements of the compressive properties of single proteoglycan aggregates.

Proteoglycan aggregate is a major component of the extracellular matrix in articular cartilage and is considered to be responsible for the resistance to compression of this tissue. The reduced stiffness of articular cartilage due to the loss of proteoglycan aggregate has been reported in osteoarthritis. In order to understand the mechanical properties of extracellular matrix in articular cartilage at molecular level, the compressive properties of 36 single molecules of proteoglycan aggregate were directly measured using a laser tweezers/interferometer system. The proteoglycan aggregates showed resistance when compressed to approximately 30% of their contour length. The stiffness of proteoglycan aggregates increased non-linearly from 2.6+/-3.8 pN/microm (compressed to 30-35% of their contour length) to 115.5+/-30.9 pN/microm (compressed to 2.5-5% of their contour length).

Compressive Strength↗

PubMed2004

The PCL significantly affects the functional outcome of total knee arthroplasty.

This study tests the hypothesis that patients receiving a posterior cruciate ligament (PCL)-retaining prosthesis have no difference in functional outcome compared to those receiving a cruciate-sacrificing, posterior-stabilized (PS) design. Forty-nine patients underwent a total knee arthroplasty (TKA), performed by a single surgeon using the same implant design with either a PCL-retaining or a PS tibial insert. Each patient completed a self-administered, validated Total Knee Function Questionnaire as well as the SF-36. At 1-year follow-up, each patient's range of motion and Knee Society knee score were measured. There were no statistically significant differences between the 2 groups using the traditional measures of function following total knee replacement, including overall satisfaction with surgery. However, the TKFQ revealed that patients with PS knees reported greater functional limitations in squatting, kneeling, and gardening. Our results suggest that with the specific implant used in this study, substitution for the PCL with a spine and cam mechanism may not fully restore the functional capacity of the intact PCL, particularly in high-demand activities that involve deep flexion.

Aged↗

PubMed2004

The optimal strategy for stable tibial fixation in revision total knee arthroplasty.

In revision total knee arthroplasty, the optimal strategy for stabilizing the tibial component in the face of proximal defects remains controversial. The stability of a revision tibial prosthesis was measured using a mechanical surrogate of the revision tibia, while varying the defect treatment proximally and the cortical engagement distally. An offset axial load in combination with an axial torque were applied to each specimen to simulate the stance phase of gait. It was found that, in revision total knee arthroplasty, the mechanical stability of tibial fixation is increased by the addition of a canal filling stem, especially in the presence of poor proximal bone. Proximal tibial coverage, even with a custom-fitted tibial component, adds little additional stability to a tibial tray stabilized by intramedullary engagement of a canal-filling stem.

Arthroplasty, Replacement, Knee↗

PubMed2004

Cyclic testing of arthroscopic knot security.

PURPOSE: Arthroscopic soft tissue repairs undergo many cycles of tensioning and relaxation before significant tissue healing occurs, and knot security under cyclic loads is essential for good results after these repairs. The current study was designed to assess the security of arthroscopic knots under stepwise cyclic loading. TYPE OF STUDY: In vitro materials testing. METHODS: Three types of arthroscopic knots--sliding knots with loop reversal but without post switching (S=SxSxSxS), modified Revo knots with loop reversal and post switching twice (S=S//xSxS//xS), and the SMC knot backed by 2 throws with loop reversal and post switching (S//xS//xS)--were compared with five-throw square knots tied with an open technique. All knots were tied with No. 2 braided nonabsorbable suture around 2 aluminum rods. They were pretensioned to 10 N, and initial displacement was recorded. The knots were then cycled at 1 Hz for 9 different load levels, with 250 cycles at each level, followed by a 30-second rest period to allow recording of permanent laxity of the suture loop. The first step of cyclic loading was from 10 to 40 N, and the upper limit was increased by 10 N for each successive load level. Any knot surviving cyclical loading was pulled to failure. RESULTS: Ten knots of each configuration were tested. All 3 arthroscopic slip knots showed significantly less initial displacement compared with the square knots (0.26 mm compared with 0.45 mm, respectively, P <.005). All square and modified Revo knots reached the ninth (120 N) loading level, whereas only 6 of the SMC knots and 3 of the arthroscopic knots without post switching reached the ninth loading level. Furthermore, all square and modified Revo knots failed by suture breakage at the knot, whereas 8 arthroscopic knots without post switching and 5 SMC knots failed by slipping. In fact, 3 of the arthroscopic knots without post switching and 1 of the SMC knots failed during the initial cyclic loading from 10 to 40 N. The modified Revo knots reached 3 mm of permanent laxity at significantly higher load levels than the square knots tied with an open technique (96 N v 78 N, P <.005). The SMC knots reached 3 mm of permanent laxity at statistically similar load levels compared with the square knots, but showed considerably more variability. None of the arthroscopic knots without post switching survived the entire cyclic-loading protocol. Four square, 5 modified Revo, and 5 SMC knots that survived cyclic loading reached ultimate failure at statistically similar load levels (157, 156, and 152 N, respectively). CONCLUSIONS: Post switching and loop reversal are key to arthroscopic knot security. Arthroscopic slip knots may be tighter at the time of knot construction than openly hand-tied square knots. The modified Revo knots appear to be as durable as openly hand-tied square knots regarding resistance to loosening under cyclic loading conditions. Security of arthroscopic knots without post switching is quite variable, making these knots less reliable. The SMC knot also proved not to be as reliable as the square and modified Revo knots when cyclically tested.

Arthroscopy↗

PubMed2004

Factors affecting the severity of backside wear of modular tibial inserts.

BACKGROUND: The use of modular tibial components in total knee arthroplasty introduces a possible source of polyethylene wear at the nonarticulating (backside) surface. However, it is not known whether this phenomenon is an incidental finding observed in unique specimens or is a feature common to all modular components. The purpose of this study was to determine the type and severity of backside wear in retrieved tibial inserts of several common total knee designs. METHODS: One hundred and twenty-four polyethylene tibial inserts of twelve different designs were retrieved at revision total knee replacements after implantation periods ranging from zero to 180 months. Each insert was visually inspected with use of a stereomicroscope for seven different modes of surface damage in four quadrants defining the backside surface. RESULTS: Pitting, burnishing, and measurable polyethylene protrusions were observed on the backside of polyethylene inserts of implant designs with a variety of different capture mechanisms. Across all implant designs, pitting was observed in 90% of the retrieved specimens; burnishing, in 77%; and protrusion, in 61%. Overall, implants of the IB-II (Insall-Burstein-II) design (Zimmer) exhibited the most severe burnishing, whereas those of the Duracon design (Howmedica) had the most severe pitting. Severe protrusions were noted with inserts of one design (AMK [Anatomic Modular Knee]; DePuy). A longer time in situ was associated with larger polyethylene protrusions, but the severity of pitting and burnishing did not increase with increasing duration of implantation. CONCLUSIONS: Moderate-to-severe wear of the nonarticulating surface of the tibial insert was frequently observed in all designs of knee prostheses, independent of the capture mechanism. These results indicate that new designs of modular tibial components are needed to prevent the generation of polyethylene wear debris through backside wear of total knee replacements.

Humans↗

PubMed2004

Backside wear of modular ultra-high molecular weight polyethylene tibial inserts.

BACKGROUND: The capture mechanisms of modular tibial total knee components may allow relative micromotion between the insert and the base-plate, leading to wear at the nonarticulating (backside) surface. Although retrieved components often display laxity in the capture mechanism in the unloaded condition, the magnitude of the relative motion that actually occurs under physiologic conditions has not been determined. This study was performed to assess the impact of different modes of knee-loading on the relative micromotion between the insert and the base-plate and the relationship between the duration that the implant had been in situ and the severity of backside wear. METHODS: Twenty-one posterior-stabilized total knee replacements of one common design (Insall-Burstein II) were retrieved at one to 100 months after implantation. The extent and severity of backside wear was graded with use of stereomicroscopy. All components were soaked in a bath (of physiologic saline solution at 37 degrees C for four days prior to reassembly. The relative micromotion between the insert and the base-plate of each specimen was measured in vitro in two different conditions: with no axial load and with a combination of loads and torques simulating the stance phase of gait. RESULTS: The capture mechanism laxity between the insert and the tibial base-plate in the unloaded condition was approximately eight times larger than the micromotion measured during simulated gait. The capture mechanism laxity allowed a mean (and standard deviation) of 618 +/- 226 micro m of total relative micromotion compared with 103 +/- 54 micro m of relative micromotion during the gait cycle. Under both loading conditions, the predominant direction of interface motion was medial-lateral. No correlation was found between the magnitude of capture mechanism laxity and the relative micromotion measured during simulated gait (p = 0.11). Larger polyethylene protrusions on the backside surface did not correlate with less micromotion (p = 0.48) or with capture mechanism laxity (p = 0.06). CONCLUSIONS: For the implant design that was studied, capture mechanism laxity between the modular insert and the base-plate in the unloaded condition was an order of magnitude larger than and not indicative of the micromotion that occurred during simulated physiologic loading. In addition, polyethylene protrusions into the screw-holes of tibial base-plates did not seat or lock the insert in place and reduce relative motion. CLINICAL RELEVANCE: While some clearance between the insert and the base-plate is required to allow assembly of modular tibial components at the time of surgery, the amount of relative interface motion during a functional activity such as normal gait, which can produce potentially damaging wear debris, is unknown. However, the compressive forces applied to the articular surface during a functional activity may substantially reduce micromotion between the insert and the base-plate relative to the unloaded condition.

Adult↗

PubMed2003

A method for testing compressive properties of single proteoglycan aggregates.

This study presents a method for direct measurement of the compressive properties of single molecules of proteoglycan aggregate using a state-of-the-art laser tweezers/interferometer system previously developed to test the tensile properties of single molecules. A typical molecule of proteoglycan aggregate showed a highly non-linear resistance to compression after being compressed to about 25% of its original molecule length.

Compressive Strength↗

PubMed2003

Extraarticular abrasive wear in cemented and cementless total knee arthroplasty.

In this study, we examine the contributions of periprosthetic impingement to a seldom recognized source of PE damage resulting in gouging, abrasion, and severe localized damage in cemented and cementless total knee replacement. One hundred sixty two tibial components of 34 different designs in a retrieval collection were examined. The presence and location of abrasive wear to the nonarticulating edges of the insert were measured, with representative specimens examined using SEM. Significant abrasive wear was observed in 35% of the retrievals with cemented femoral components and 25% from noncemented components. Within the group of worn inserts, abrasive scars were seen with a frequency of 75% on the extreme medial edge, 20% on the extreme lateral edge, 26% on the posteromedial edge, and 16% on the posterolateral edge. The role of extraarticular impingement in this damage mode was confirmed by examination of retrieved femoral components with overhanging cement or embedded osteophytes. In the majority of cases, this complication may be avoided by careful removal of excess cement and extracortical osteophytes.

Adult↗