Biomedical subjects

Edward M Wojtys

Publications and source records attributed to Edward M Wojtys.

11 recordsLinked to original sources

PubMed2006

The effect of an impulsive knee valgus moment on in vitro relative ACL strain during a simulated jump landing.

BACKGROUND: We tested the hypothesis that impulsive compression, flexion and valgus knee moment loading during a simulated one-footed jump landing will significantly increase the peak relative strain in the anteromedial region of the anterior cruciate ligament compared with loading without the valgus moment. METHODS: Ten cadaveric knees [mean (SD) age: 67.9 (7.6) years; 5 males; 5 females] were mounted into a custom fixture to simulate a lower extremity impact loading of approximately 1600 N. Triaxial load cells monitored the 3D tibial and femoral impulsive force and moments at 2000 Hz, while 3D tibiofemoral kinematics were measured at 400 Hz. Pre-impact quadriceps, hamstring and gastrocnemius muscle forces were simulated using pretensioned steel cables. A differential variable reluctance transducer measured the relative strain in the anteromedial aspect of the anterior cruciate ligament. With the knee initially in 25 degrees flexion, 10 trials were conducted with the impulsive force directed 4 cm posterior to the knee joint center in the sagittal plane ("neutral" loading) to cause a flexion moment, 10 trials were conducted under a similar loading, but with the force directed 15 degrees lateral to the knee sagittal plane ("valgus" loading), and the 10 neutral loading trials were then repeated. A non-parametric Wilcoxon signed rank test was used to test the hypothesis using a P<0.05 significance level. FINDINGS: The peak normalized anterior cruciate ligament strain was 30% larger for the impulsive compression loading in valgus and flexion compared with an impulsive compression loading in isolated flexion (P<0.05). INTERPRETATION: Minimizing the abduction loading of the knee during a jump landing should help reduce anterior cruciate ligament strain during that maneuver.

Aged↗

PubMed2006

Understanding and preventing noncontact anterior cruciate ligament injuries: a review of the Hunt Valley II meeting, January 2005.

The incidence of noncontact anterior cruciate ligament injuries in young to middle-aged athletes remains high. Despite early diagnosis and appropriate operative and nonoperative treatments, posttraumatic degenerative arthritis may develop. In a meeting in Atlanta, Georgia (January 2005), sponsored by the American Orthopaedic Society for Sports Medicine, a group of physicians, physical therapists, athletic trainers, biomechanists, epidemiologists, and other scientists interested in this area of research met to review current knowledge on risk factors associated with noncontact anterior cruciate ligament injuries, anterior cruciate ligament injury biomechanics, and existing anterior cruciate ligament prevention programs. This article reports on the presentations, discussions, and recommendations of this group.

Anterior Cruciate Ligament↗

PubMed2005

The relationship between quadriceps muscle force, knee flexion, and anterior cruciate ligament strain in an in vitro simulated jump landing.

BACKGROUND: An instrumented cadaveric knee construct was used to quantify the association between impact force, quadriceps force, knee flexion angle, and anterior cruciate ligament relative strain in simulated unipedal jump landings. HYPOTHESIS: Anterior cruciate ligament strain will correlate with impact force, quadriceps force, and knee flexion angle. STUDY DESIGN: Descriptive laboratory study. METHODS: Eleven cadaveric knees (age, 70.8 [19.3] years; 5 male; 6 female) were mounted in a custom fixture with the tibia and femur secured to a triaxial load cell. Quadriceps, hamstring, and gastrocnemius muscle forces were simulated using pretensioned steel cables (stiffness, 7 kN/cm), and the quadriceps tendon force was measured using a load cell. Mean strain on the anteromedial bundle of the anterior cruciate ligament was measured using a DVRT. With the knee in 25 degrees of flexion, the construct was vertically loaded by an impact force initially directed 4 cm posterior to the knee joint center. Tibiofemoral kinematics was measured using a 3D optoelectronic tracking system. RESULTS: The increase in anterior cruciate ligament relative strain was proportional to the increase in quadriceps force (r(2) = 0.74; P < .00001) and knee flexion angle (r(2) = 0.88; P < .00001) but was not correlated with the impact force (r(2) = 0.009; P = .08). CONCLUSION: The increase in knee flexion and quadriceps force during this simulated 1-footed landing strongly influenced the relative strain on the anteromedial bundle of the anterior cruciate ligament. CLINICAL RELEVANCE: These results suggest that even in the presence of knee flexor muscle forces, the increase in quadriceps force required to prevent the knee from flexing during landing can place the anterior cruciate ligament at risk for large strains.

Aged↗

PubMed2005

Meniscus structure and function.

True appreciation of the structure and function of the knee joint meniscus is a relatively recent occurrence. Even decades after studies were published documenting the detrimental effects of meniscectomoy such as osteoarthritis, many physicians continued to advocate total meniscectomy for even minor meniscal pathology. Fortunately, the clinical approach to these problems has undergone dramatic change over the past 20 years. A review of the anatomy and ultrastructure of the meniscus, and its relationship to normal function in terms of load transmission, shock absorption, joint stability, lubrication, and nutrition will enable a better understanding of the rationale for meniscus preservation techniques, including meniscal repair and meniscal transplant.

Humans↗

PubMed2004

Long-term results after combined medial meniscal allograft transplantation and anterior cruciate ligament reconstruction: minimum 8.5-year follow-up study.

PURPOSE: The purpose of this study was to evaluate the long-term results after medial meniscal allograft transplantation combined with anterior cruciate ligament (ACL) reconstruction. TYPE OF STUDY: Retrospective clinical outcome study. METHODS: Between 1990 and 1992, 9 medial meniscal allograft transplantations were performed in symptomatic knees with a previous total or near-total medial meniscectomy. One of the 9 patients required transplant removal postoperatively because of a presumed low-grade infection versus immune reaction. The remaining 8 patients were evaluated, with an average follow-up time of 9.7 years. All 8 patients underwent an ACL reconstruction. One patient also had a staged high tibial osteotomy. RESULTS: All 8 patients were evaluated with the standard International Knee Documentation Committee (IKDC) form with no normal scores: 1 had a nearly normal score, 4 had abnormal scores, and 3 severely abnormal scores. The IKDC symptoms evaluation produced 2 normal scores, 5 nearly normal scores, and 1 abnormal score. The IKDC function test showed 5 normal scores, 1 nearly normal score, and 2 abnormal scores. Six of the 8 patients were extremely pleased with the function of the knee and were active in recreational sports. All 8 patients would recommend the procedure to a friend and would undergo the procedure again given similar circumstances. CONCLUSIONS: The findings of this study agree with several other studies with shorter follow-up times that medial meniscal allograft transplantation can significantly improve knee function in symptomatic medial meniscus-deficient knees. The addition of a ligament-stabilizing procedure probably improved the results in this patient population. LEVEL OF EVIDENCE: Level IV, Case Series.

Adult↗

PubMed2003

Gender differences in muscular protection of the knee in torsion in size-matched athletes.

BACKGROUND: Female athletes who participate in sports involving jumping and cutting maneuvers are up to eight times more likely to sustain a rupture of the anterior cruciate ligament than are men participating in the same sports. We tested the hypothesis that healthy young women are able to volitionally increase the apparent torsional stiffness of the knee, by maximally activating the knee muscles, significantly less than are size-matched men participating in the same type of sport. METHODS: Twenty-four NCAA (National Collegiate Athletic Association) Division-I athletes (twelve men and twelve women) competing in sports associated with a high risk of injury to the anterior cruciate ligament (basketball, volleyball, and soccer) were compared with twenty-eight collegiate endurance athletes (fourteen men and fourteen women) participating in sports associated with a low risk of such injuries (bicycling, crew, and running). Male and female pairs were matched for age, height, weight, body mass index, shoe size, and activity level. Testing was performed with a weighted pendulum that applied a medially directed 80-N impulse force to the lateral aspect of the right forefoot. The resulting internal rotation of the leg was measured optically, to the nearest 0.25 degrees, at 30 degrees and 60 degrees of knee flexion, both with and without maximal activation of the knee muscles. RESULTS: Maximal rotations of the leg were greater in women than in men in both the passive and the active muscle state (16% and 27% greater [p = 0.01 and p = 0.02], respectively). Moreover, female athletes exhibited a significantly (18%) smaller volitional increase in apparent torsional stiffness of the knee under internal rotation loading than did the matched male athletes (p = 0.014); this was particularly the case for those who participated in sports involving jumping and pivoting maneuvers (42% difference between genders, p = 0.001). CONCLUSIONS: The collegiate female athletes involved in high-risk sports exhibited less muscular protection of the knee ligaments during external loading of the knee than did size and sport-matched male athletes.

Analysis of Variance↗

PubMed2002

The role of arthroscopic synovectomy in the management of hemarthrosis in hemophilia patients: financial perspectives.

PURPOSE: The purpose of this study was to determine the financial efficacy of arthroscopic synovectomy in hemophilia patients with recurrent hemarthroses. TYPE OF STUDY: Cost-benefit analysis. METHODS: A retrospective chart review from 1993 through 1999 yielded 11 cases of arthroscopic synovectomies performed for recurrent hemarthroses at the University of Michigan. There were 7 ankle arthroscopies, 3 elbow arthroscopies, and 1 knee arthroscopy. The average age of the patients was 8 years (range, 4-13 years). All had the severe form of hemophilia A. The average follow-up was 41 months (range, 9-75 months). The preoperative costs were determined by multiplying the number of preoperative bleeds by the dollar amount of the replacement therapy used to treat the hemarthroses. The surgical costs included the surgery itself as well as the hospital stay and the dollar amount of the replacement therapy used in the perioperative period. The total postoperative costs included the surgical costs and the dollar amount of any replacement therapy used to treat any postoperative hemarthroses. RESULTS: The financial benefit of arthroscopic synovectomy was found to be statistically significant when average preoperative cost per month ($7,500) was compared with the average postoperative cost per month ($900), P =.028. Arthroscopic synovectomy was again found to be financially beneficial when the average total preoperative cost ($88,000) was compared with the average total postoperative cost ($24,000), P =.028. The average number of hemarthroses preoperatively was 71 and the average postoperatively was 7, which was statistically significant (P =.028). CONCLUSIONS: In this small series of patients with intermediate follow-up, arthroscopic synovectomy was found to be cost effective in the treatment of patients with recurrent hemarthroses.

Adolescent↗

PubMed2002

Sonographic imaging of the posterolateral structures of the knee: findings in human cadavers.

PURPOSE: To evaluate and characterize the use of sonography in imaging the posterolateral structures of the knee in human cadavers. TYPE OF STUDY: In vitro laboratory investigation using human cadavers and sonography. METHODS: Three cadaver knees were dissected to expose the posterolateral corner with the skin and subcutaneous tissue removed. The iliotibial band, biceps femoris muscle and tendon, lateral gastrocnemius tendon, the lateral collateral ligament, the popliteus tendon, the popliteofibular ligament, the arcuate ligament, and the fabellofibular ligament (when present) were identified. Following the soft tissue dissection, sonography was performed to characterize these structures. The technique was refined using this "open" examination method as anatomical and structural detail was noted. After adequate familiarization with this technique, researchers performed sonography on 2 pairs of thawed fresh-frozen cadaver knees, 1 pair with a fabella and 1 pair without a fabella. After sonographic examination of all of the posterolateral structures, the knees were dissected and the structures previously identified by sonography were verified. RESULTS: In all 4 cadaver specimens, all posterolateral structures were identified based on their imaging characteristics and surrounding bony and soft tissue landmarks. We also present dissection photographs and sonographic images depicting our study findings. CONCLUSIONS: Sonographic imaging may provide the clinician with valuable information regarding the posterolateral structures of the knee. To our knowledge, this is the first study to investigate the sonographic findings of these structures. This technique may assist the physician evaluating these injuries and help in preoperative planning for repair or reconstructive procedures. Further research is needed to determine the accuracy of sonography in identifying injured posterolateral corner knee structures in vivo.

Aged↗

PubMed2002

A gender-related difference in the contribution of the knee musculature to sagittal-plane shear stiffness in subjects with similar knee laxity.

BACKGROUND: Women's susceptibility to injuries involving the anterior cruciate ligament remains unexplained. Volitional contraction of the knee musculature is known to increase the resistance of the knee to shear deformation, raising the possibility that muscles play a part in protecting the anterior cruciate ligament during hazardous activities. We therefore tested the hypothesis that a volitional co-contraction of the knee muscles increases the sagittal-plane shear stiffness (or resistance to anterior tibial translation) of the knee more in men than in women. METHODS: Twenty-three volunteers (ten men and thirteen women; mean age, 24.7 +/- 5.4 years), all with anterior tibial translation of 6 mm, agreed to participate in the study. Each subject underwent a subjective evaluation of knee function and activity level, an arthrometric measurement of passive anterior tibial translation, and an isokinetic dynamometer strength test at 60 degrees/sec. A dynamic stress test was then performed to measure anterior tibial translation while simultaneously monitoring lower-extremity muscle response. RESULTS: Maximum co-contraction of the knee musculature significantly decreased mean anterior tibial translation in both men and women (from 7.8 mm to 2.2 mm in men and from 6.5 mm to 3.1 mm in women). The corresponding percentage increase in shear stiffness of the knee was significantly greater (p = 0.003) in men (379%) than in women (212%). CONCLUSIONS: The results suggested that women have a diminished potential for muscular protection of passive structures of the knee in anterior tibial translation. CLINICAL RELEVANCE: Maximal muscular protection of the anterior cruciate ligament in women may be less than that in men. This may be one factor explaining why more women than men are apt to sustain injuries to the anterior cruciate ligament.

Adult↗

PubMedDate not supplied

The effect of the menstrual cycle on anterior cruciate ligament injuries in women as determined by hormone levels.

Anterior cruciate ligament injury rates are reported to be two to eight times higher in women than in men within the same sport. Because the menstrual cycle with its monthly hormonal fluctuations is one of the most basic differences between men and women, we investigated the association between the distribution of confirmed anterior cruciate ligament tears and menstrual cycle phase. Sixty-nine female athletes who sustained an acute anterior cruciate ligament injury were studied within 24 hours of injury at four centers. The mechanism of injury, menstrual cycle details, use of oral contraceptives, and history of previous injury were recorded. Urine samples were collected to validate menstrual cycle phase by measurement of estrogen, progesterone, and luteinizing hormone metabolites and creatinine levels at the time of the anterior cruciate ligament tear. Results from the hormone assays indicate that the women had a significantly greater than expected percentage of anterior cruciate ligament injuries during midcycle (ovulatory phase) and a less than expected percentage of those injuries during the luteal phase of the menstrual cycle. Oral contraceptive use diminished the significant association between anterior cruciate ligament tear distribution and the ovulatory phase.

Adolescent↗

PubMedDate not supplied

The effect of ankle braces on the prevention of dynamic forced ankle inversion.

BACKGROUND: Athletes often employ prophylactic braces to reduce the risk of ankle injuries. HYPOTHESIS: Ankle braces do not significantly decrease the risk of forced inversion on a standardized one-footed jump landing. STUDY DESIGN: Controlled laboratory study. METHODS: Fourteen healthy men with a mean age of 25.1 years were tested. Three braces, two semirigid (Aircast and Bledsoe) and one lace-up (Swede-O), were fitted to each subject. Forced dynamic ankle inversion of 24 degrees was to be resisted as the subjects landed on one foot with a force of two body weights on a stimulus presented randomly in 5 of 15 jump trial blocks onto a hard, level force plate. Subjects first completed 1 no-brace block of 5 trials to establish baseline performance, then 3 randomly ordered 15-trial blocks testing performance with each of the braces, and then finally a no-brace 5-trial block. RESULTS: The average no-brace success rate was 24%, which demonstrated the challenging nature of the task. All three braces increased the success rate (average, 44%); however, only the two semirigid braces proved to be significantly better than the unbraced state. CONCLUSION: This test holds promise for evaluating brace efficacy when landing with one foot unexpectedly on an object that acts to forcibly invert the ankle.

Adult↗