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Biomedical subjects

B K Graf

Publications and source records attributed to B K Graf.

At least 19 recordsLinked to original sources
PubMed1997

Untreated osteochondritis dissecans of the femoral condyles: prediction of patient outcome using radiographic and MR findings.

OBJECTIVE: We investigated the usefulness of plain film and MR findings in predicting the outcome of conservatively treated patients with femoral osteochondritis dissecans. DESIGN: Without knowledge of the clinical outcome, we retrospectively reviewed the initial plain films and MR examinations. Each MR examination was evaluated for the four MR findings of instability. PATIENTS: Fourteen patients were studied in whom osteochondritis dissecans of a femoral condyle had been treated conservatively for periods ranging from 1.2 to 8.5 years. RESULTS AND CONCLUSION: Three of five patients with an open femoral growth plate and one of nine patients with a closed growth plate had a good clinical outcome. Both patients with lesions smaller than 160 mm2 in area had a good outcome and ten of 12 patients with larger lesions had a poor outcome. Both patients with stable lesions by MR imaging had a good outcome while ten of 12 patients with a lesion unstable by MR imaging had poor outcomes. All six patients with a cartilage fracture or articular defect had poor outcomes. The results of this study should be considered preliminary since only 14 patients were followed. However, it appears that a good clinical outcome is likely when the femoral growth plate is open, when the osteochondritis dissecans is small, and when the lesion is stable by MR imaging. When a cartilage fracture or articular defect is found on MR imaging, the patient is likely to have a poor outcome.

Adolescent↗
PubMed1996

Reassessment of the MR criteria for stability of osteochondritis dissecans in the knee and ankle.

OBJECTIVE: T2-weighted MR images has been reported to be an accurate method for assessing osteochondritis dissecans. We reviewed our MR experience to confirm the accuracy of the published criteria of instability. We also assessed the value of each of four MR signs of instability. DESIGN: We reviewed the original MR interpretations, arthroscopic reports, and MR examinations of 40 patients with osteochondritis dissecans of the talar dome or femoral condyles. Arthroscopy was used as the gold standard for stability. The MR examinations were reviewed retrospectively for a high-signal-intensity line or cystic area beneath the lesion, a high-signal-intensity line through the articular cartilage, or a focal articular defect. PATIENTS: All patients who had undergone MR imaging for osteochondritis dissecans from 1990 to 1993 were reviewed. Forty patients were identified who had arthroscopy after the MR examination. There were 30 male and 10 female patients with an average age of 25.7 years. Thirty-one lesions were in femoral condyle and nine were in the talar dome. RESULTS AND CONCLUSIONS: The original MR interpretations correctly identified 35 of the 36 unstable lesions and all 4 stable lesions, giving a sensitivity of 0.97 and specificity of 1.0. There was a 98% agreement between the original and retrospective diagnoses. A high-signal-intensity line was seen beneath 72% of the 36 unstable lesions. The other three signs were noted in 22-31% of the unstable lesions. Fifty-six percent of the unstable lesions showed only one sign of instability. MR imaging is a highly sensitive method for detection of unstable osteochondritis dissecans. The presence of any one sign indicates instability, the most frequent sign being an underlying high-signal-intensity line. Because we examined only four stable lesions, our 95% confidence interval of 0.40-1.0 for a specificity of 1.0 gives only a limited estimate of the specificity of MR.

Adult↗
PubMed1995

Compatibility of adaptive responses with combining strength and endurance training.

Impairment in strength development has been demonstrated with combined strength and endurance training as compared with strength training alone. The purpose of this study was to examine the effects of combining conventional 3 d.wk-1 strength and endurance training on the compatibility of improving both VO2peak and strength performance simultaneously. Sedentary adult males, randomly assigned to one of three groups (N = 10 each), completed 10 wk of training. A strength-only (S) group performed eight weight-training exercises (4 sets/exercise, 5-7 repetitions/set), an endurance-only (E) group performed continuous cycle exercise (50 min at 70% heart rate reserve), and a combined (C) group performed the same S and E exercise in a single session. S and C groups demonstrated similar increases (P < 0.0167) in 1RM squat (23% and 22%) and bench press (18% for both groups), in maximal isometric knee extension torque (12% and 7%), in maximal vertical jump (6% and 9%), and in fat-free mass (3% and 5%). E training did not induce changes in any of these variables. VO2peak (ml.kg-1.min-1) increased (P < 0.01) similarly in both E (18%) and C (16%) groups. Results indicate 3 d.wk-1 combined training can induce substantial concurrent and compatible increases in VO2peak and strength performance.

Adaptation, Physiological↗
PubMed1994

Effect of preconditioning on the viscoelastic response of primate patellar tendon.

Current techniques for anterior cruciate ligament reconstruction with patellar tendon (PT) allow a measurable tension to be applied to the graft at the time of fixation. The viscoelastic nature of the PT, however, ensures that relaxation will cause the graft tension to decrease over time. To better understand this process, a primate model was used to evaluate acute viscoelastic relaxation in the PT. Thirty-five patella-patellar tendon-tibia (P-PT-T) complexes were harvested from normal primate knees (Cynomolgus monkeys), and were divided into five groups for mechanical comparison. Specimens were subjected to two 10-min relaxation tests separated by a 1-30-min unloaded interval. The first test provided baseline relaxation data as well as serving as preconditioning for the second test. Results indicate that preconditioning significantly reduces the tension lost in a graft due to viscoelastic relaxation. The effect of preconditioning is reduced with increasing recovery time (the time between preconditioning and the second relaxation test), but the effect is still significant after 30 min of unloading. No differences were observed in the relaxation behavior of specimens that were cyclicly or isometrically preconditioned, nor were differences observed between irradiated and nonirradiated specimens. These results suggest that preconditioning can reduce acute tension loss in a graft due to viscoelastic relaxation and that simple isometric preconditioning is just as effective as cyclic stretching.

Animals↗
PubMed1994

Meniscal tears missed on MR imaging: relationship to meniscal tear patterns and anterior cruciate ligament tears.

OBJECTIVE: MR imaging of the knee is a valuable technique for diagnosing meniscal tears, but some tears found at arthroscopy are not shown on MR imaging. The purpose of this study was to determine whether or not tears were more frequently missed in the presence of an anterior cruciate ligament tear or when tears had certain locations or configurations. MATERIALS AND METHODS: We reviewed the original MR reports and surgical records of 400 patients who had both an MR examination and arthroscopy of the knee. Using chi 2 analysis, we examined how the sensitivity for detecting meniscal tears varied with the presence of a tear of the anterior cruciate ligament, with the location of the tear within the meniscus, and among six configurations of meniscal tears. We also studied whether sensitivity decreased with an increasing delay between MR examination and arthroscopy. RESULTS: In the presence of a tear of the anterior cruciate ligament, the sensitivity decreased from 0.97 to 0.88 (p = .016) for medial meniscal tears and from 0.94 to 0.69 (p = .0005) for lateral tears. The overall sensitivity for lateral meniscal tears was significantly less for posterior (p = .001) and peripheral (p = .005) tears than for other tear locations or configurations. The sensitivities did not significantly differ between tear locations and configurations in the medial meniscus or with an increasing delay until arthroscopy. Patients with a torn anterior cruciate ligament were more likely to have peripheral tears of the medial meniscus (p = .00004) and posterior (p = .0004) and peripheral (p = .04) tears of the lateral meniscus. CONCLUSION: Because of their location and configuration, meniscal tears associated with an anterior cruciate ligament injury are more difficult to detect on MR images than are tears in knees with an intact ligament. If a tear of the anterior cruciate ligament is detected, special attention should be given to the subtle peripheral tears that may be present in either meniscus, but most commonly in the posterior horn of the lateral meniscus. These tears are especially difficult to detect on MR images.

Adult↗
PubMed1994

Risk factors for restricted motion after anterior cruciate reconstruction.

A retrospective review of 373 patients who had undergone anterior cruciate ligament (ACL) reconstruction utilizing the central third of the patellar tendon was undertaken to identify those factors that placed a patient at risk for restricted postoperative motion (flexion < or = 125 degrees or flexion contracture > or = 10 degrees). Stepwise logistic regression analysis determined that the variables most strongly correlated with restricted final range of motion (ROM) were open surgery (P = .0008) and reconstruction performed < or = 7 days after the initial injury (P = .004). Age, associated meniscal repair, or associated collateral ligament injuries did not significantly affect the ROM. A subgroup of 204 patients arthroscopically reconstructed more than 7 days post-injury were significantly less likely to have limited motion when ROM exercises were begun within 2 days of surgery (P = .008). These data support delayed, arthroscopic ACL reconstruction followed by early ROM exercises as useful techniques for avoiding postoperative motion problems.

Adolescent↗
PubMed1993

Evaluation of acute knee injuries.

Early, accurate diagnosis and aggressive treatment are important in returning a patient with an acute knee injury to full function. Although many problems, such as acute tendinitis and mild sprains, can be simply treated with short periods of rest, some disabilities may be chronic or recurrent and require more invasive treatment. Many acute injuries necessitate emergency treatment or early surgical intervention. Detailed history taking and a thorough and knowledgeable examination of the knee are the key elements in evaluation. Special tests and radiographic studies are also helpful.

Arthrography↗
PubMed1993

The effects of knee effusion on quadriceps strength and knee intraarticular pressure.

The purpose of this study was to determine the effect of varied amounts of effusion on quadriceps strength and knee intraarticular pressure (IAP) during active knee movement. Five subjects had 60 ml of saline, in 20 ml increments, infused into the right knee. Quadriceps strength and knee IAP were continuously measured at each level of effusion, while the subject performed isokinetic knee exercises. A control group of five subjects performed the same exercises, but with no saline infusion. No significant changes in quadriceps strength were seen in the control group. In the experimental group, quadriceps strength decreased as the amount of effusion increased, and increased following aspiration. The greatest decrease in strength occurred at those knee positions where IAP was highest (full flexion and extension). Results of this study indicate that quadriceps strength is diminished and IAP markedly increased when an effused knee is exercised.

Adult↗
PubMed1993

Diagnosis of meniscal tears of the knee with MR imaging: effect of observer variation and sample size on sensitivity and specificity.

OBJECTIVE: A wide range in the efficacy of MR imaging for the diagnosis of meniscal tears of the knee has been reported. To evaluate two possible causes for this variation, we studied how sensitivity and specificity are affected when different observers and sample sizes are used. MATERIALS AND METHODS: Two hundred MR examinations of the knee in patients for whom the results of arthroscopy were available were used for the study. One hundred eight medial meniscal tears and 58 lateral meniscal tears were found at arthroscopy. The sensitivity and specificity for detection of meniscal tears were determined for the original interpretations and retrospective evaluations by three observers. Comparisons were also made between sample sizes of 25 and 100. chi 2 analysis was used for unmatched data sets and McNemar's statistic was used for matched sets. RESULTS: For the 200 examinations, the sensitivity was 0.89-0.93 for medial meniscal tears and 0.79-0.83 for lateral meniscal tears. The specificity was 0.86 for medial meniscal tears and 0.90-0.92 for lateral meniscal tears. Sensitivity and specificity varied widely among different observers and different sample sizes. However, we found no significant difference between any of the comparisons at the p < .05 level. The largest interobserver variation occurred in the detection of lateral meniscal tears, with a sensitivity of 0.71 for one observer and 0.88 for another observer (p = .16). The largest variation between sets of 100 examinations was a change in sensitivity for detection of lateral meniscal tears from 0.74 to 0.88 for the original interpretations (p = .10). For the sample sets of 25 cases, the variation was even larger, with the sensitivity for detection of lateral meniscal tears varying from 0.5 for one set to 1.0 for another. CONCLUSION: We conclude that chance variation related to sample size can cause large but not statistically significant variations in sensitivity and specificity in this setting. These variations are of sufficient magnitude to explain many of the differences in reported sensitivity and specificity for MR imaging in the diagnosis of meniscal tears. We found no significant difference in observer performance.

Adolescent↗
PubMed1993

MR diagnosis of meniscal tears of the knee: importance of high signal in the meniscus that extends to the surface.

OBJECTIVE: The presence of intrameniscal signal in contact with the surface is a commonly used criterion for the diagnosis of meniscal tear. This signal presumably represents the actual tear in the meniscus. However, some menisci with signal that contacts the surface are noted to be intact at arthroscopy whereas other menisci that have no signal in contact with the surface are found to be torn. We investigated the relationship between the presence of a meniscal tear at arthroscopy and the location within the menisci of signal that contacted the surface. We hypothesized that patterns were present that would improve the accuracy of MR diagnosis of a meniscal tear. MATERIALS AND METHODS: We reviewed the MR and arthroscopic findings from 200 consecutive patients who had both knee MR examinations and knee arthroscopy. There were 108 medial and 58 lateral meniscal tears on arthroscopy. Each MR examination was reviewed for three aspects of intrameniscal signal: the number of images showing signal possibly or definitely contacting the surface, the specific surfaces involved, and the signal location. The coronal and sagittal images were evaluated separately. We correlated each of these features with the presence of a meniscal tear at arthroscopy. RESULTS: Menisci with signal possibly contacting the surface had the same frequency of tears (three tears in 33 menisci) as menisci without signal contacting the surface (15 tears in 194 menisci). More than 90% of menisci with signal contacting the surface on more than one image were torn, but only 55% of medial and 30% of lateral menisci with such signal on only one image were torn. In the torn menisci with signal contacting the surface, such signal was seen only on sagittal MR images in 31% of the medial menisci and 45% of the lateral menisci. Sixteen percent of the torn lateral menisci had signal contacting the meniscal surface in only the anterior two thirds of the meniscus, whereas this was true in only 2% of the torn medial menisci. Distinct patterns were not seen in the association between tears and signal contacting either the superior or the inferior surface. CONCLUSION: We found definite patterns in the location of intrameniscal signal that comes in contact with the meniscal surface. These patterns vary in the frequency of associated meniscal tears. Although menisci with internal signal in contact with the surface are usually torn, a tear is less likely if such signal is present on only one image. Tears may be identifiable on only one image plane. Tears in the anterior horn of the lateral meniscus are not uncommon. Knowledge of these patterns should help in the MR diagnosis of meniscal tears.

Adolescent↗
PubMed1992

Signs of patellar chondromalacia on sagittal T2-weighted magnetic resonance imaging.

We incidentally noted distinctive high signal defects or fissures in the patellar articular cartilage on sagittal T2-weighted magnetic resonance (MR) images in 4 patients. At subsequent arthroscopy all 4 patients were found to have patellar chondromalacia. To determine the reliability of these signs, we retrospectively evaluated, in a blinded manner, sagittal T2-weighted MR images of the knee in 75 patients who were undergoing arthroscopic assessment of their patellar articular cartilage. We identified high signal defects or fissures in the patellar cartilage of 5 patients. Patellar chondromalacia was noted at arthroscopy in all 5 patients. Arthroscopy demonstrated patellar chondromalacia in an additional 21 patients with normal MR images. We conclude that high signal defects or fissures on sagittal T2-weighted images are useful signs of patellar chondromalacia. This single imaging sequence will, however, detect only a small number of the cartilage lesions that may be present.

Adolescent↗
PubMed1992

Anterior cruciate ligament tears in skeletally immature patients: meniscal pathology at presentation and after attempted conservative treatment.

We evaluated 12 skeletally immature patients with acute, intrasubstance tears of the anterior cruciate ligament (ACL) and open physes for meniscal pathology. Arthrograms were completed in 10 of 12 patients, and subsequent arthroscopy confirmed 8 meniscal tears (4 medial, 4 lateral) in 6 patients. Four patients with repairable menisci underwent arthroscopic meniscal repair and stabilization. Eight patients received quadriceps and hamstrings rehabilitation and returned to sports with a brace. After return to sports, all braced patients developed instability with multiple episodes of "giving way." Average time from initial injury to first episode of instability was 7 months. Seven patients sustained further meniscal damage an average of 15 months (range 7-27 months) after initial injury. We conclude that meniscal pathology is commonly associated with ACL tears in skeletally immature patients and we recommend arthrography or arthroscopy to evaluate patients with suspected ACL tears. Brace management did not prevent instability or new meniscal tears.

Acute Disease↗
PubMed1991

Anxiety and intense running exercise in the presence and absence of interpersonal competition.

The purposes of this study were to evaluate the effects of intense running exercise in the presence and absence of interpersonal competition on both (a) pre-exercise anxiety levels and (b) alterations in anxiety as a consequence of the exercise. Seven females and 10 males performed a 5-mile run over the same outdoor course on two separate days. In one condition the subjects ran in a road-race in which intense exercise was combined with interpersonal competition. In the second condition, exercise of the same intensity (84% VO2max) and duration was completed, but interpersonal competition was absent. Cognitive (State-Trait Anxiety Inventory; STAI) and somatic (Body Awareness Scale; BAS) aspects of anxiety were measured 15 min before and after exercise as well as on a separate day under non-stressful, baseline conditions. A main effect for the Trials factor was found using repeated measures ANOVA [Condition (presence/absence of interpersonal competition) X Gender X Trials (baseline/pre-exercise/post-exercise)], and post-hoc analysis revealed that post-exercise state anxiety and body awareness levels were both reduced compared to pre-exercise baseline values. Condition and Gender main effects were not significant nor were any of the interaction effects. Pre-exercise STAI and BAS levels were found to be significantly (p less than .01) elevated above baseline values. However, while post-exercise STAI scores were significantly (p less than .01) below the baseline STAI level, the post-exercise BAS values did not fall below the corresponding baseline level.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

A device to measure the cross-sectional area of soft connective tissues.

A device has been designed and fabricated to measure the cross-sectional area of soft connective tissues ex vivo. It consists of two displacement transducers; one sensing tissue thickness and the other sensing width. Outputs are recorded (via an analog to digital interface) using a personal computer. Numerical integration of a thickness versus width plot computes cross-sectional area. This plot also provides a quality check of acquired data. This device has been successfully used in biomechanical studies of rabbit patellar tendons, rat medial collateral ligaments, and dissected specimens of human fascia.

Anthropometry↗
PubMed1990

Acute modification of biomechanical properties of the bone-ligament insertion to rat limb unweighting.

We investigated the acute adaptation of the rat femur-medial collateral ligament-tibia (FMT) complex to 7 days of limb unweighting by means of a hind-limb suspension protocol. Male, young adult, Harlan Sprague-Dawley rats were randomly assigned to either control or suspended groups. Rats deprived of hind limb-to-ground contact forces had a 42% decrease in soleus muscle mass compared with the control group. Medial collateral ligament (MCL) length and cross-sectional area were measured, and each FMT complex was tension tested to failure. All failed at their tibia-MCL insertion. The ultimate load in the FMT and the peak Kirchhoff stress in the MCL (occurring immediately before insertion site failure) were significantly reduced in the suspended group. The suspended MCLs were 9.7% larger in area and 5.7% shorter in length than the controls under the same preload (0.25 N). We found no significant differences between the control and suspended MCLs in Green strain, stretch, or deformation immediately before insertion site failure, nor did we find a significant difference in the MCL tangent modulus. This study indicates that even acute periods of limb unweighting can structurally compromise bone-ligament insertions. Further, this study implies that the adaptations responsible for this structural compromise must involve acute changes in the intrinsic zone (or zones) of the bone-ligament insertion.

Animals↗
PubMed1990

Value of MR imaging in staging osteochondral lesions of the talus (osteochondritis dissecans): results in 14 patients.

Osteochondral lesions (osteochondritis dissecans) of the talus are common articular lesions that are usually traumatic in origin. Clinical management of these lesions is based on whether or not the fragments are attached. We studied the value of MR imaging in determining the stability of the osteochondral fragments. In 13 of 14 patients who had had correlative surgery, we accurately predicted the presence and extent of attachment of the fragment to the talus by performing preoperative MR imaging. The other patient had a false-positive diagnosis of a chondral fragment. All seven partially attached fragments had an irregular high-signal zone on T2-weighted images at the fragment/talar interface. The four unattached fragments had a complete ring of fluid surrounding the lesion. On the basis of these findings, we think MR of the ankle can be used to assess accurately talar osteochondral lesion stability and aid in clinical decision making.

Adolescent↗
PubMed1990

Osteochondritis dissecans of the knee: value of MR imaging in determining lesion stability and the presence of articular cartilage defects.

Osteochondritis dissecans is a lesion of articular surfaces that is of uncertain etiology. These lesions are seen on radiographs as a bony defect or fragmentation of the subchondral bone. A bony defect may be an actual surface hole or the defect may be filled with fibrous tissue or fibrocartilage. Similarly, the apparent bone fragments may be only partially attached so they are unstable and prone to displacement or they may be firmly attached with fibrous tissue. Knowledge of fragment stability and the presence of an articular cartilage defect is useful in deciding on treatment. This information cannot be determined on plain films or clinical examination. We correlated MR examinations with arthroscopic findings in 21 patients with osteochondritis dissecans of the knee to see if MR imaging could be used to predict lesion stability and articular cartilage defects. A high-signal interface between the lesion and the femur was used as evidence of lesion instability and was found in 15 lesions. One of these lesions was questionably stable at surgery; the remainder were unstable and partially attached. The other six patients had displaced fragments with large articular defects that were clearly visualized on the MR examinations. We conclude that MR imaging is useful in evaluating articular surface defects and lesion stability in patients with osteochondritis dissecans.

Adolescent↗