Citations

Background Tightness of the posteroinferior capsule is assumed to be the cause of internal rotation loss in baseball pitchers. Although the relationship between posterior capsule and subacromial impingement has been recognized, this relationship during the baseball-pitching motion is unclear. Hypothesis Contact pressure during baseball-pitching motion increases with posterior capsule tightness. Study Design Controlled laboratory study. Methods Eight fresh-frozen shoulders were used. The peak contact pressure and area on the coracoacromial arch were measured on a custom-designed shoulder experimental device capable of 6 degrees of freedom motion. Simultaneously, the sites of peak pressure on the coracoacromial arch and humerus were observed from various angles. The posteroinferior capsule tightness was simulated by plicating the capsule in the region from 6 to 8 o'clock. The static testing positions correlated to the early cocking, late cocking, acceleration, deceleration, and follow-through phases of the pitching motion. Results The peak contact pressure during the follow-through phase (0.63 ± 0.50 MPa) significantly increased with posteroinferior capsule tightness (1.00 ± 0.65 MPa) (P = .014). Additionally, the contact area on the coracoacromial ligament during the follow-through phase (0.98 ± 0.67 cm2) significantly increased with posteroinferior capsule tightness (1.47 ± 0.91 cm 2) (P < .001). The site of the peak contact pressure did not change between the 2 conditions. Conclusion Our findings demonstrate that posteroinferior capsule tightness leads to higher contact pressure under the subacromial arch and increased contact area, particularly on the coracoacromial ligament during the follow-through phase. Clinical Relevance This tightness may affect risk of injury of the rotator cuff and its surrounding tissues by increasing subacromial contact during pitching.

With progress of modern technology, manually-propelled wheelchairs are still of importance for individuals with mobility impairments. The repeated wheelchair propulsion and strenuous daily activities cause high loads and thus injuries on the upper extremity joints. Over the past few years, a considerable number of studies have been made on biomechanical analysis of wheelchair propulsion and wheelchair-related activities. Thorough investigation of biomechanics during wheelchair propulsion enhances comprehension of mechanism of injuries and provides information to improve wheelchair design and fitting. Numerous investigations have been made to demonstrate factors which cause low effectiveness of force application and inefficiency of movements. Emphasis was also placed on developing analytical models to simulate wheelchair propulsion.

Since the electrogoniometric method has been justified for the measurement of lower extremity joint motion, a similar device is developed for the measurement of elbow joint and forearm rotations. In this design, the axis of forearm rotation coincides with the anatomical axis which eliminates the cross talk existing in the regular triaxial goniometer. Although the axis of abduction-adduction is still offset from the elbow joint, special linkage arrangement was used to obtain equivalent motion. Experimental method was used to validate the accuracy of the device and model simulation was performed to emphasize the importance of accurate placement of the instrument on test subjects. Application of the present apparatus to normal subjects was studied to illustrate the range of elbow motion required in performing normal activities of daily living. This device is currently used in the functional evaluation of patients with elbow and forearm problems.

Tendons are frequently injured by direct trauma. Tendon adhesions were a common sequel of tendon repair and are one of the most challenging problems in hand surgery. The concept of “controlled motion” gradually replaced “total immobilization” in the treatment of flexor tendon injuries and today represents a standard of care for all primary repaired flexor tendon injury. Use of controlled motion splints during the early stages of stages of tendon recovery in crease tendon gliding. However, how best to achieve passive motion and the effect of passive motion on tendon gliding have remained controversial subjects. Based on a series of recent experiments, the concept of “dynamic synergistic wrist motion splint” was established and evaluated. It was found that this synergistic wrist motion increases the tendon excursion due to eliminating the laxity and buckling of tendon in the regions between pulleys without introduce excessive amount of tension. The purpose of this study is to design and fabricate a dynamic splint based on this concept and define the nature coordinated motion between the wrist and finger joints due to the passive tension of the muscles in vivo. Parametric analysis will be conducted to achieve an optimum design with the consideration of anatomic constraints. Clinical trial of using such dynamic splint will be evaluated in the future.

AbstractPurpose: Complement may play a role in the clinical response to rituximab and other monoclonal antibody–based therapies of cancer. The purpose of this study was to explore the relationship between the C1qA[276] polymorphism and the clinical response to rituximab in patients with follicular lymphoma.Experimental Design: Genotyping for C1qA[276A/G] was done in 133 subjects with follicular lymphoma treated with single-agent rituximab, and correlation with clinical response was done using Cox regression analysis.Results: Prolonged remission was observed among subjects that responded clinically to rituximab therapy and were carriers of the A allele compared with homozygous G subjects. Homozygous G subjects had a time to progression of 282 days, whereas A-allele carriers had a time to progression of 708 days [hazard ratio, (HR), 2.5; 95% confidence interval (95% CI), 2.0-3.1; P = 0.02]. Among subjects who achieved complete remission, homozygous G subjects had a time to progression of 250 days, whereas A-allele carriers had a time to progression of 1,118 days (HR, 4.5; 95% CI, 4.1-4.8, P = 0.04). The difference persisted after controlling for CD32 and CD16 polymorphisms. In patients who responded to rituximab used as first-line agent, a linear trend was observed among the C1qA[276] genotypes, with homozygous A subjects achieving complete response at a higher rate compared with heterozygous or homozygous G subjects.Conclusions: Our findings indicate that polymorphisms in the C1qA gene may affect the clinical response and duration of response to rituximab therapy of follicular lymphoma. These results could have direct implications on designing antibodies with improved efficiency and enhance our understanding of the role of complement in monoclonal antibody therapy.

Muscle moment arm defines the function of the muscle. To date, moment arms of the arm muscles at the glenohumeral joint using the tendon excursion method have not been reported. As the functions of these muscles at the shoulder joint are controversial, this study was undertaken to determine the moment arms of the long and short heads of the biceps (LHB, SHB), the coracobrachialis, and the long head of the triceps muscles. The moment arms were determined in 10 cadaveric shoulders by measuring the tendon excursion when the arm was rotated by 1 radian (57.3°) in 22 different motions. The LHB was a flexor, horizontal flexor, and abductor. The SHB and coracobrachialis were flexors, horizontal flexors, and adductors. The long head of the triceps was an extensor and adductor. Arm rotation significantly affected the function of the LHB only: it was an internal rotator in flexion and an external rotator in abduction. This study clarifies the individual function of the arm muscles at the glenohumeral joint.

Total joint arthroplasty (TJA) is implemented primarily for the relief of pain, and secondarily for achieving better function by increasing the joint’s strength and motion. In order to keep health costs low, it is desirable that the TJA achieves and maintains a long-term and secure fixation of the implanted components. Unfortunately, clinical follow-up shows that the prosthetic finger implant components have long-term complications including bone resorption, wear, loosening, and failure of the implant components. Although the mechanism of complications is not fully understood, it is well known that the wear and failure of prostheses are highly related to the mechanical forces or stresses of implant components. It is therefore desirable that reliable 3-D computational finite element analysis (FEA) models can be developed and used for the stress analysis of implants. In this study, the finger proximal interphalangeal (PIP) prosthetic components were analyzed using a nonlinear finite element method. Implant components under different joint flexion angles as well as different forces were studied. The stress distribution on the contact surface of the implant component was obtained. The developed FEA models can be used to examine the contact situations (contact stress, contact region, and stress distribution), which are critical to the wear and potential failure of the implant components. Based on FEA results, the design of the current finger PIP implants can be improved for optimum performance and a long-term fixation.